Reactor system for the oxidative dehydrogenation (ODH) of ethane

Abstract

An oxidative dehydrogenation (ODH) reactor system and method of operating the ODH reactor system, comprising providing a feed having ethane, oxygen, and a diluent to obtain a reaction mixture flowing through a tube side of an ODH reactor, and converting the ethane to ethylene using an ODH catalyst on the tube side. A coolant is passed through a shell side of the ODH reactor to maintain the tube side at a first temperature in a first cooling section and a second temperature in a second cooling section, the first temperature being lower than the second temperature. The ODH reactor system may comprise two or more ODH reactors. In the case of an ODH reactor system having two or more ODH reactors in series, oxygen gas may be injected between the ODH reactors.

Description

[Technical field]

[0001] The present disclosure relates to an oxidative dehydrogenation (ODH) reactor system for improving the performance of an ODH plant for the production of ethylene. [Background technology]

[0002] Catalytic oxidative dehydrogenation of alkanes to the corresponding alkenes is an alternative to steam cracking. In contrast to steam cracking, oxidative dehydrogenation (ODH) can operate at lower temperatures and generally does not produce coke. For ethylene production, ODH can provide higher yields for ethylene than steam cracking. ODH may be carried out in a reactor vessel with a catalyst for converting alkanes to the corresponding alkenes. Acetic acid as a by-product may be produced in the conversion of lower alkanes (e.g., ethane) to the corresponding alkenes (e.g., ethylene). The product alkene and by-product acetic acid may each be recovered from the ODH reactor effluent.

[0003] Carbon dioxide is the primary greenhouse gas emitted by human activities. Carbon dioxide (CO2) can be produced in various industrial and chemical plant facilities. In such facilities, there is the potential to reduce the CO2 emissions at the facility by using energy more efficiently, thus decreasing the facility's CO2 footprint. Summary of the Invention

[0004] An oxidative dehydrogenation (ODH) reactor system and method of operating an ODH reactor system. During operation, a feed having ethane, oxygen, and a diluent is provided to obtain a reaction mixture that flows through a tube side of the ODH reactor. The ethane is converted to ethylene via an ODH catalyst in the tube side. A coolant is passed through the shell side of the ODH reactor to maintain the tube side at a first temperature in a first cooling section and a second temperature in a second cooling section, the first temperature being lower than the second temperature.

[0005] The ODH reactor system may include two or more ODH reactors. In the case of an ODH reactor system having two or more ODH reactors in series, oxygen gas may be injected between the ODH reactors. Oxygen gas may be injected into the product effluent of the upstream ODH reactor that feeds the downstream ODH reactor. In some implementations, the interstage product effluent may be cooled to accommodate oxygen injection.

[0006] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will become apparent from the description and drawings, and from the claims. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram of an ODH plant having an ODH reactor system for dehydrogenating ethane to ethylene. [Diagram 2] 2 and 2A are diagrams illustrating an exemplary multi-tubular fixed bed reactor. [Diagram 3] FIG. 3 is a diagram of an ODH reactor system that may be the ODH reactor system of FIG. [Figure 4] FIG. 4 is a diagram of an ODH reactor system that may be the ODH reactor system of FIG. [Figure 4A] FIG. 4A is a diagram of an ODH reactor system that may be the ODH reactor system of FIG. [Diagram 5] FIG. 5 is a diagram of an ODH reactor system that may be the ODH reactor system of FIG. [Figure 6] FIG. 6 is a diagram of an ODH reactor system that may be the ODH reactor system of FIG. [Figure 7] FIG. 7 is a diagram of an ODH reactor system that may be the ODH reactor system of FIG. [Figure 8] FIG. 8 is a diagram of an ODH reactor system that may be the ODH reactor system of FIG. [Figure 9]FIG. 9 is a diagram of an ODH reactor system that may be the ODH reactor system of FIG. [Figure 10] FIG. 10 is a diagram of an ODH reactor system that may be the ODH reactor system of FIG. [Figure 11] FIG. 11 is a diagram of an ODH reactor system that may be the ODH reactor system of FIG. [Figure 12] FIG. 12 is a diagram of an ODH reactor system that may be the ODH reactor system of FIG. [Figure 13] FIG. 13 is a ternary plot of an example flammability diagram for a mixture of ethane, oxygen, and steam at 300° C. and 500 kilopascals (kPa) absolute pressure. [Figure 14] FIG. 14 is a block flow diagram of a method of operating an ODH reactor system having at least one ODH reactor. [Figure 15] FIG. 15 is a block flow diagram of a method of operating an ODH reactor system having at least one ODH reactor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Embodiments of the present technology relate to oxidative dehydrogenation (ODH) reactor systems that dehydrogenate alkanes (e.g., ethane) to the corresponding alkenes (e.g., ethylene). Aspects relate to configurations of the ODH reactor system that reduce energy consumption at the ODH plant. For example, some aspects relate to configurations that reduce the amount of dilution steam in the alkane feed, thereby reducing energy consumption by the ODH plant.

[0009] The ODH reactor may dehydrogenate ethane to ethylene over an ODH catalyst in the presence of oxygen. Ethylene may be separated from the ODH reactor effluent to obtain product ethylene.

[0010] FIG. 1 is an ODH plant 100 having an ODH reactor system 102 that dehydrogenates ethane to ethylene. The dehydrogenation of ethane to ethylene may be the reaction of ethane with oxygen over an ODH catalyst to obtain ethylene. The ODH reactor system 102 may be a single reactor system having a single ODH reactor (e.g., configurations 1-7 described below) or may be a multi-reactor system having two or more ODH reactors operatively arranged in series (e.g., configurations 8-13 described below). Additional ODH reactors may be included in parallel in configurations 1-13 to achieve a desired amount of ethylene production capacity in the ODH plant. The ODH reactor may be a multi-tubular fixed bed reactor having an ODH catalyst on the tube side and a coolant (e.g., molten salt) flowing on the shell side to remove the heat of reaction from the tube side.

[0011] In addition to configuring the ODH reactor system 102 to reduce the amount of dilution steam implemented in the feed 104 to reduce the energy consumption of the ODH plant, considerations may also include increasing energy efficiency by recovering heat from the ODH reactor to generate steam 106 for the ODH plant 100. For example, heat from the coolant discharged from the reactor (heated on the shell side) and / or heat from the process effluent discharged from the ODH reactor (from the tube side) may be utilized to heat and vaporize boiler feedwater into steam.

[0012] The ODH reactor system 102 may have a single ODH reactor 110 or may have additional ODH reactors 112 in operational series. Additionally, additional similarly configured ODH reactors may be included in parallel in operational series to increase ethylene production capacity. In the case of a multiple reactor system, the first ODH reactor 110 in the series may discharge effluent as a feed to the second ODH reactor 112. In certain implementations with the ODH reactor system 102 as a multiple reactor system, the effluent 108 may be discharged from the last ODH reactor 112 in the series (e.g., the second ODH reactor, the third ODH reactor, etc.). The diluent in the reactors of the feed 104 may include, for example, nitrogen gas (N2), carbon dioxide gas (CO2), or water (steam), or any combination thereof. If the diluent in feed 104 includes water, the water in effluent 108 may include both unreacted diluent water and water produced in the ODH reaction in the ODH reactor.

[0013] In implementations, the feed 104 may include ethane and oxygen and is provided (e.g., conveyed in a conduit) to the ODH reactor 110. The feed 104 may include a diluent (e.g., steam) to place the feed 104 outside the flammability limits. The steam as a diluent may be referred to as dilution steam. In preparing the feed 104, energy (heating capacity) may be applied to heat or vaporize water and water vapor or steam may be incorporated into the feed 104 as dilution steam. The feed 104 may be characterized as a mixed feed including ethane, oxygen, and dilution steam.

[0014] Dilution steam entering ODH reactor system 102 in feed 104 may be discharged from ODH reactor system 102 in effluent 108. In processing the effluent 108 downstream of reactor system 102, energy (cooling capacity) may be applied to condense the dilution steam in the effluent 108.

[0015] The major demands of energy in the ODH plant 100 can be [1] heating water to provide dilution steam for the feed 104 (e.g., in the feed preparation system 114), [2] condensing the dilution steam in the ODH reactor effluent 108 in the downstream effluent processing 116, and [3] separating the condensed acetic acid from the condensed water. Thus, by reducing the amount of dilution steam in the feed 104, energy consumption in the ODH plant 100 can be reduced. Techniques for reducing the amount of dilution steam in the feed 104 include reducing the amount of oxygen gas in the feed 104. Advantageously, for a feed 104 low in oxygen, the low dilution steam places the feed 104 outside the flammability limit. See, e.g., FIG. 13.

[0016] Techniques for reducing the amount of oxygen in the feed 104 may include increasing ethylene selectivity in promoting ethylene formation over carbon monoxide formation (consuming a greater stoichiometric amount of oxygen than ethylene formation) and promoting ethylene formation over carbon dioxide formation (consuming a greater stoichiometric amount of oxygen than ethylene formation) in the ODH reactor. Techniques for promoting ethylene formation over carbon monoxide and carbon dioxide formation may include operating one or more cooling sections of the ODH reactor at lower temperatures, if feasible and / or beneficial, since higher temperatures (of the tube-side reaction mixture and ODH catalyst) may more readily allow for the undesirable formation of carbon monoxide and carbon dioxide.

[0017] Techniques that do not promote the formation of carbon monoxide and carbon dioxide may include increasing the heat transfer (and / or increasing the efficiency of heat transfer, e.g., by increasing the heat transfer coefficient) in the ODH reactor from the tube side to the shell side. This may avoid or reduce the occurrence of tube-side temperature spikes that may promote or cause (lead to) the (undesirable) formation of carbon monoxide and carbon dioxide. To improve heat transfer, it may include limiting the temperature rise of the coolant (e.g., molten salt) through the shell side of the ODH reactor to increase the flow rate of the coolant through the shell side to increase the value of the heat transfer coefficient. To improve heat transfer, it may include limiting the diameter (e.g., nominal diameter, outer diameter, or inner diameter) of the tubes in the tube bundle in the ODH reactor to increase the velocity of the reaction mixture flowing through the tubes. This may result in, for example, an increase in the Reynolds number (Re), which may increase the heat transfer coefficient. Increasing the heat transfer coefficient may also reduce the occurrence of tube-side temperature spikes. Tube-side temperature spikes can undesirably result in greater formation of carbon monoxide and carbon dioxide (and therefore greater consumption of oxygen).

[0018] The formation of carbon monoxide and carbon dioxide consumes a greater stoichiometric amount of oxygen than the formation of ethylene. Thus, increased formation of carbon monoxide and carbon dioxide may result in more oxygen in the feed 104, which undesirably results in more dilution steam in the feed 104. More dilution steam in the feed 104 may mean more energy consumption in the ODH plant 100. Also, the formation of carbon monoxide and carbon dioxide is an undesirable reaction since ethylene is the more valuable product. Carbon monoxide and carbon dioxide are generally undesirable products. The production of carbon dioxide may increase the CO2 footprint of the ODH plant (facility) 100.

[0019] The ODH plant 100 includes a feed preparation system 114 that provides a feed 104 to the sole or first ODH reactor 110 in the ODH reactor system 102. Again, the feed 104 may include ethane and oxygen. As discussed above, the feed 104 may include a diluent that places the feed 104 outside of the flammability limits. See, for example, FIG. 13, which shows a flammability diagram for a mixture of ethane, oxygen, and diluent as water (steam).

[0020] Examples of diluents that may be utilized to place the feed 104 stream outside the flammability limits may include water, nitrogen, carbon dioxide, helium, argon, methane, and the like. In some embodiments, water is the diluent. As shown, water as a diluent may generally be in the form of steam. Steam or vaporized water may be an attractive diluent, for example, because in some implementations separation of water from the product stream (effluent) of the ODH reactor system 102 is relatively straightforward.

[0021] The feed preparation system 114 may combine a diluent with the ethane (and oxygen) to obtain the feed 104 that is delivered to the ODH reactor system 102. When using a diluent such as water, the feed preparation system 114 may heat or vaporize the water for incorporation (addition) to the ethane (and oxygen) as dilution steam.

[0022] In some implementations, ethane 118 (gas) and water 120 may be provided to the feed preparation system 114, where the water 120 is incorporated as steam or water vapor into the ethane 118 to obtain the feed 104. Such incorporated water 120 may be characterized or referred to as dilution steam. Oxygen 122 (gas) may be provided to the feed preparation system 114 for addition to the ethane 118 to obtain the feed 104. In certain implementations, some or all of the oxygen 122 may be added to a conduit that carries the feed 104 to the ODH reactor system 102.

[0023] Feed preparation equipment 124 may include heat exchangers for heating water 118 as a liquid (possibly vaporizing liquid water), ethane saturation columns for saturating ethane 118 with water 120, steam drum vessels for adding steam (including water 120) to ethane 118, etc. In embodiments of feed dilution when heating water 118 (e.g., in feed preparation 114), medium pressure (MP) steam may be used, which is a higher value (more expensive) steam than low pressure (LP) steam. Sources of LP and MP steam in ODH plant 100 may include, for example, extraction turbines or pressure reducing valves for HP or VHP steam.

[0024] For the addition of water steam to the feed 104 to the ODH reactor, embodiments may use, for example, a dilution steam drum or a saturation tower. A dilution steam drum may be simpler in providing dilution steam, but unfortunately may rely on a higher value heat source, such as medium pressure steam. In some implementations, the medium pressure steam may be better utilized instead, for example to drive a steam turbine. A saturation tower saturates a hydrocarbon (e.g., ethane) gas and / or oxygen gas with water steam and may utilize a relatively high water circulation. For examples of feed dilution, see International Publication No. WO 2022 / 229848, entitled "Integration for Feed Dilution in Oxidative Dehydrogenation (ODH) Reactor System," which is incorporated herein by reference in its entirety.

[0025] In addition to ethylene formed in the ODH reactor, components may include acetic acid, carbon dioxide, carbon monoxide, and water. Thus, the ODH plant 100 may produce ethylene 126 and acetic acid 128. Carbon monoxide and carbon dioxide may undesirably be formed in the ODH reactor and discharged to the effluent 108 along with the ethylene and acetic acid.

[0026] The ODH reactors (e.g., 110, 112) may produce ethylene (C2H4) as a primary product and acetic acid (CH3COOH) as a value-added by-product. The ODH reactors (e.g., 110, 112) may produce carbon monoxide (CO), carbon dioxide (CO2), and water (H2O). The reaction mechanism within the ODH reactor, characterized as the reaction of ethane (C2H6) with oxygen (O2), can be described as follows: C2H6+0.5O2→C2H4+H2O C2H6+1.5O2→CH3COOH+H2O C2H6+2.5O2→2CO+3H2O C2H6+3.5O2→2CO2+3H2O

[0027] As seen in the above equation, the reactions that form CO and CO generally utilize (consume) a greater stoichiometric amount of O than the listed reactions that produce ethylene. Thus, configuring the ODH reactor system 102 to increase ethylene selectivity in promoting ethylene formation over CO and / or CO formation may reduce the amount of O implemented in the feed 104. A reduction in the amount of O in the feed 104 may mean that less dilution steam is implemented in the feed 104 to place the feed 104 outside the flammability limits (outside the flammability envelope) (see, e.g., FIG. 13). As explained, less dilution steam in the feed 104 may mean reduced energy consumption in the ODH plant.

[0028] The product effluent 108 from the ODH reactor system 102 may include ethylene, acetic acid, carbon dioxide, carbon monoxide, water, and unreacted ethane. In addition to dilution steam as water in the effluent 108, the effluent 108 may also include water (as water vapor or steam) formed in the ODH reactor.

[0029] Treatment 116 of the effluent 108 may include condensing the water and acetic acid to remove the acetic acid and water from the effluent 108. The water and acetic acid may be condensed, for example, via a heat exchanger utilizing a cooling medium (e.g., cooling water, air, etc.). In some implementations, a flash drum vessel or quench tower vessel may facilitate separation of the condensed liquid from the effluent 108.

[0030] The condensed water and condensed acetic acid as a mixture may be processed in an acetic acid unit (e.g., having an extraction column vessel, a solvent recovery column vessel, and a water stripper column vessel) to separate the by-product acetic acid 128 and liquid water 130. In some implementations, the water 130 may be reused for use in the ODH plant 100. For example, the water 130 discharged from the acetic acid unit may be reused for scrubbing the process gas in effluent treatment 116 (as recycle water) and / or as water for dilution steam in feed preparation 114) (e.g., 120), etc.

[0031] After the condensed water and condensed acetic acid are removed from the effluent 108 to the acetic acid unit, the remaining portion of the effluent 108 as a gas (excluding the condensate) may include ethylene, CO, CO2, and ethane. The gas may be scrubbed (e.g., with liquid water, such as water 130) in a scrubber column vessel to remove residual acetic acid vapor and residual water vapor from the gas. The gas may be subjected to separation to remove CO and CO2. The gas may be sent through a C2 splitter (ethane / ethylene splitter) (a distillation column vessel with distillation trays) to separate the ethane from the gas to obtain the product ethylene 126.

[0032] Equipment 132 in effluent treatment 116 may include, for example, a heat exchanger for condensing water and acetic acid from the effluent, a flash drum vessel for separating condensed water and condensed acetic acid as a mixture from effluent 106, and an acetic acid unit (e.g., having an extraction column vessel) for processing the mixture to separate by-product acetic acid 128 and liquid water 130. Equipment 132 may include a scrubber vessel and a process gas compressor (mechanical compressor) as described above to increase the pressure of the ethylene-bearing gas from effluent 108. Other configurations and alternative equipment are applicable.

[0033] In some implementations, the equipment 132 may include vessels for separating CO and CO2 (and other light components) from the gas, as well as a C2 splitter. In other implementations, the equipment 132 does not include such equipment, and the product stream 126 is an intermediate product stream having ethylene and ethane sent for further processing. Again, other configurations are applicable. For examples of processing effluents, see International Publication No. WO 2022 / 229847, entitled "Integration for Processing Effluent of Oxidative Dehydrogenation (ODH) Reactor," which is incorporated herein by reference in its entirety.

[0034] The acetic acid unit can be a significant consumer of energy in an ODH plant, which is affected by the amount of dilution steam. The presence of more dilution steam in the effluent 108 (and condensed with the acetic acid) can mean more heating (e.g., in the steam reboiler of the column) and more cooling (e.g., in the overhead condenser of the column) in the acetic acid unit.

[0035] FIG. 2 depicts an exemplary multi-tubular fixed-bed reactor 200 that is a vessel. The vessel is typically a cylindrical vessel with an elliptical or semi-elliptical head. The vessel may have a vertical orientation (as shown) or a horizontal orientation. The vessel may be a pressure vessel designed and configured (e.g., having an appropriate wall thickness) to be subjected to an internal pressure up to a specified pressure (design pressure) that is higher than the ambient pressure (atmospheric pressure). The pressure vessel may be rated to hold a fluid up to the design pressure. During operation, the operating pressure within the pressure vessel may generally be maintained below the design pressure. The pressure vessel may be constructed according to a formal code or standard, such as the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) or the European Union (EU) Pressure Equipment Directive (PED). In the case of an ODH reactor as a multi-tubular fixed-bed reactor, the reactor vessel and tubes may be metal, such as steel (e.g., stainless steel).

[0036] The multi-tubular fixed bed reactor 200 comprises a tube side and a shell side. The tube side may be the process side (for converting a flowing reaction mixture of a process feed to a product). The shell side may be the utilization side (for the flow of a heat transfer fluid). The shell side may be similar in nature to a vessel jacket, but may also be similar or similar to the shell side of a shell-and-tube heat exchanger.

[0037] The multi-tubular fixed bed reactor 200 has a shell 202 and a tube bundle, which may be similar to a shell-and-tube heat exchanger, except that the tubes 204 contain a fixed bed of catalyst. The tube bundle is a plurality of tubes 204 aligned generally in parallel. In the tube bundle, the tubes 204 may be supported and held in place in a parallel fashion by a tube sheet (e.g., a plate). The tube sheet may be a circular plate perforated so that the tubes fit through the perforated openings.

[0038] The walls of the shell 202 may be the walls of the vessel. The volume of the shell 202 around the longitudinal length of the tubes 204 may be characterized as the shell side of the reactor 202. The shell side may be for the flow of heat transfer fluid around the tubes 204. The volume inside the tubes 204 may be characterized as the tube side of the reactor 202. FIG. 2A is an exploded view of the tubes 204 with the tube walls 210 and the catalyst 212 disposed within the tubes 204. Additionally, in FIG. 2, the longitudinal ends of the vessel may be considered as tube sides. In particular, the longitudinal ends of the vessel where the process feed 206 is introduced into the tubes 204 and where the process product 208 is discharged from the tubes 204, respectively, may be characterized as the tube sides of the reactor 202.

[0039] In FIG. 2, the tubes 204 may be (at least partially) filled with a catalyst 212. The catalyst 212 may be a fixed bed of catalyst within the tubes 204. The catalyst 212 may facilitate the conversion of the feed 206 to a product 208 discharged from the reactor. In operation, providing the feed 206 to the tube side may result in a reaction mixture flowing through the tubes 204, in which reactions in the reaction mixture are facilitated by the catalyst 212. The process feed 206 may enter the vessel through a vessel inlet (e.g., an inlet nozzle) to the tube side. The process product 208 may exit the vessel through a vessel outlet (e.g., an outlet nozzle) from the tube side.

[0040] The process feed 206 enters the bottom of the vessel. The process product 208 exits the top of the vessel. However, the reactor 200 can be configured such that the process feed 206 enters the top of the vessel and the process product 208 exits the bottom of the vessel.

[0041] The heat transfer fluid 214 may enter the vessel (on the shell side) through a vessel inlet (e.g., an inlet nozzle) and flow through the shell side around the tubes 204. In the case of tube-side reactions as endothermic, the heat transfer fluid 214 may be a heat carrier to provide heat for the endothermic reaction. In the case of tube-side reactions as exothermic, the heat transfer fluid 214 may be a cooling medium (coolant) and the heat transfer fluid 214 removes the heat of reaction.

[0042] The heat transfer fluid 214 provided to the reactor 200 and entering the shell side may be referred to as the heat transfer fluid feed. The heat transfer fluid 214 may flow around the tubes 204. Thus, the heat transfer fluid 214 may be subjected to heat exchange with the process reaction mixture and catalyst 212 on the tube side. The shell side may include baffles 216 that create more turbulence in the heat transfer fluid 214 to improve (increase) the heat transfer between the heat transfer fluid 214 and the tube side.

[0043] The heat transfer fluid 218 may be discharged from the reactor 200 from the shell side, such as through a vessel outlet (e.g., an outlet nozzle). The heat transfer fluid 218 discharged from the reactor 200 from the shell side may be referred to as a heat transfer fluid return that is sent (as return) to the heat transfer fluid supply system. The composition of the heat transfer fluid 218 discharged from the reactor 200 may be the same as the composition of the heat transfer fluid 214 supplied to the reactor 200. The discharged heat transfer fluid 218 may have the same composition as the supplied heat transfer fluid 214 but a different temperature due to heat exchange with the tube side reaction mixture (and catalyst 212).

[0044] The flow of heat transfer fluid 214 through the shell side is in a co-current flow direction with the flow of the reaction mixture on the tube side. However, the flow of heat transfer fluid 214 through the shell side can instead be in a counter-current flow direction with the flow of the reaction mixture on the tube side. For example, in the illustrated implementation, the reactor 200 can be configured with an inlet for supplying heat transfer fluid 214 to the top of the vessel and an outlet for returning heat transfer fluid 218 to the bottom of the vessel.

[0045] In the case of the ODH reactor as a multi-tubular fixed bed reactor, the heat transfer fluid 214 may typically be a coolant since the ODH reaction is exothermic. Additionally, the ODH reactor may have two or more cooling sections. For example, a baffle 216 or plate may extend completely across the shell side dividing the shell side into two or more sections. Each shell side section may have an inlet for supplying the heat transfer fluid 214 and an outlet for returning the heat transfer fluid 218. Each shell side section may be referred to as a cooling section that maintains the tube side reaction mixture and catalyst 212 at their respective designated temperatures (respective isotherm temperatures).

[0046] Implementations of the ODH reactors 110, 112 in FIG. 1 can be similar to reactor 200. For ODH reactors, the number of tubes 204 in the tube bundle can range into the thousands (e.g., 30,000 tubes 204). For ODH reactors, the process feed 206 can be feed 104 (FIG. 1). The process feed 206 can be the effluent discharged from the upstream ODH reactor if more than one ODH reactor is used. The process product 208 can be effluent 108 (FIG. 1). The process product 208 can be the effluent discharged as a feed to the downstream ODH reactor if more than one ODH reactor is used.

[0047] As mentioned above, for ODH reactors, the heat transfer fluid 214 may typically be a coolant since the reactions on the tube side are generally exothermic. Heat transfer occurs from the reaction mixture and catalyst 212 on the tube side, through the tube walls 210, to the heat transfer fluid 214 flowing through the shell side. The heat transfer fluid 214 as a coolant for the ODH reactor may be, for example, steam, water (including pressurized water or supercritical water), oil, or molten salt, etc. Molten salt may be selected as the coolant because of the relatively high stability of molten salts and because of the relatively high heat transfer coefficient values ​​provided by molten salts at the operating temperatures of the ODH reactor (e.g., 300-500°C). Water (whose critical points are 374°C and 22,064 kPa) or ultra-high pressure steam used as the heat transfer fluid 214 provides a relatively high pressure on the shell side, resulting in thicker walls of the shell (vessel).

[0048] An embodiment of the present technology may include specifying a diameter (e.g., nominal diameter, outer diameter, or inner diameter) of the tubes 204 of the ODH reactor to provide an appropriate velocity of the reaction mixture through the tubes 204 to advance a sufficient Reynolds number (Re) to provide a sufficient heat transfer coefficient. The fluid dynamics of the reaction mixture within the tubes 204 may affect the heat transfer from the reaction mixture and the ODH catalyst 212 to the shell-side coolant. As explained, improving the heat transfer may not promote the formation of carbon monoxide and carbon dioxide in the reaction mixture flowing through the tubes 204. Multiple embodiments may include configuring the ODH reactor to reduce the tubes 204 to a specified diameter or less in response to specifying an increase in ethylene selectivity (and thereby increasing ethylene selectivity).

[0049] For typical operating conditions and capacities of an ODH reactor, the diameter of the tube 204 of the ODH reactor [e.g., nominal diameter, outer diameter (OD), or inner diameter (ID)] may be specified in the range of, for example, 0.75 inches to 2.0 inches, 0.75 inches to 1.5 inches, or 0.75 inches to 1.25 inches. A diameter less than 0.75 inches may, in some implementations, make it difficult to load the catalyst 212 into the tube 204. However, certain implementations may accommodate a tube 204 diameter of less than 0.75 inches (for an ODH reactor). In examples, a tube 204 diameter of more than 1.25 inches or more than 1.5 inches (for an ODH reactor) may result in insufficient velocity of the reaction mixture through the tube 204, resulting in insufficient heat transfer, and thus increased formation of carbon dioxide and carbon monoxide. However, certain implementations can accommodate tube 204 diameters (for ODH reactors) greater than 1.5 inches. The following examples and associated simulations consider a 1 inch tube with 1 inch OD, 0.083 inch tube wall thickness, and 0.834 inch ID, a 1.25 inch tube with 1.25 inch OD, 0.120 inch tube wall thickness, and 1.01 inch ID, and a 1.5 inch tube with 1.5 inch OD, 0.134 inch tube wall thickness, and ID=1.232 inch. In a hypothetical example, a 2 inch tube, for example, has a 2 inch OD, 0.188 inch tube wall thickness, and 1.624 inch ID.

[0050] In some implementations, the ODH reactor may have an auxiliary tube bundle for superheating the steam. During operation, the auxiliary tube bundle receives steam (e.g., saturated steam). The steam flows through the tubes of the auxiliary tube bundle and is heated by the heat transfer fluid 214. Once the steam is superheated, it is discharged from the reactor 200 through the auxiliary tube bundle. The auxiliary tube bundle may be in the reactor vessel adjacent to the main tube bundle. Alternatively, the auxiliary tube bundle may have a dedicated shell adjacent to or attached to the vessel of the reactor 200 and a dedicated shell coupled to the shell side of the reactor 200 for the flow of the heat transfer fluid 214. The auxiliary dedicated shell may receive the wake flow of the coolant from the main shell.

[0051] Options for an ODH reactor system are shown. The example of configuration 2 presented below may be a base case. Presented configurations 1 and 3-13 may generally be compared to configuration 2 as a baseline case. However, the present technique is not limited to the various options and configurations summarized or characterized. Instead, various configurations including configurations 1-13 are given as examples. Figures 3-12 may be presented relative to one another, some including differentials relative to one another. For a description of the equipment and operation in a given view of Figures 3-12, please also refer to the description of the other views of Figures 3-12.

[0052] Figure 3 is an ODH reactor system 300, which may be ODH reactor system 102 of Figure 1. For comparison of examples of ODH reactor systems disclosed herein, an implementation of ODH reactor system 300 is referred to as Configuration 1.

[0053] The ODH reactor system 300 comprises an ODH reactor 302, which is a multi-tubular fixed-bed reactor. The reactor 302 is symbolized by multiple vertical lines collectively representing the shell side and tube side within the reactor vessel. The two diagonal lines are symbolic of coolant flow through the shell side for heat exchange between the shell side and the tube side, and indicate a cooling section. The reactor 302 has one cooling section. A coolant system external to the reactor 302 is associated with the cooling section. The cooling section may remove the heat of reaction of the exothermic reaction in the tube side to obtain a reactor isotherm temperature where the process reaction mixture and the ODH catalyst in the tube side are maintained at a constant temperature (e.g., in the range of 300°C to 500°C).

[0054] The ODH reactor 302 as a multi-tube fixed-bed reactor comprises a tube bundle having multiple tubes. In one implementation of FIG. 3, the diameter (e.g., nominal, outer, or inner diameter) of each tube is 1 inch. The inside of the tubes (internal volume) may be the tube side. The shell side may be the volume within the reactor vessel along the tube bundle around the tubes. In some implementations, the vessel wall along the straight side of the vessel may be the shell wall. During operation, heat transfer may occur from the tube side (inside the tube) through the tube wall of each tube to the shell side. In particular, heat transfer may occur from the reaction mixture (flowing within the tube) and the ODH catalyst within the tube, through the tube wall, to the coolant flowing through the shell side. In some implementations, the coolant is a molten salt.

[0055] An ODH catalyst (e.g., as a fixed bed) may be disposed inside the tube. The term "ODH catalyst" as used herein may be a catalyst known for ODH of ethane. The ODH catalyst may dehydrogenate ethane to ethylene, providing an ODH reaction in which acetic acid as a by-product may be formed. A low-temperature ODH catalyst may be beneficial. One non-limiting example of an ODH catalyst that may be utilized in the ODH reactor is a low-temperature ODH catalyst comprising molybdenum (Mo), vanadium, tellurium (Te), niobium, and oxygen (O), wherein the molar ratio of molybdenum to vanadium is 1:0.12 to 1:0.49, the molar ratio of molybdenum to tellurium is 1:0.01 to 1:0.30, the molar ratio of molybdenum to niobium is 1:0.01 to 1:0.30, and the oxygen is present in an amount that satisfies at least the valence of any metal element present. The molar ratios of molybdenum, vanadium, tellurium, and niobium can be determined by inductively coupled plasma mass spectrometry (ICP-MS).When providing an ODH reaction at less than 450°C, less than 425°C, less than 400°C, or less than 375°C, or in the range of, for example, 300°C to 500°C, the catalyst may be referred to as a low temperature ODH catalyst.

[0056] The reactor 302 vessel includes a feed inlet for receiving a feed 304 (e.g., similar to feed 104 in FIG. 1 or feed 206 in FIG. 2) into the reactor 302 on the tube side to obtain a reaction mixture flowing through the tube side. In the illustrated embodiment, the reaction mixture flows upward through the tubes. The feed inlet may be a vessel inlet nozzle coupled to a feed conduit that carries the feed 304 to the reactor 302. The feed 304 may include ethane, oxygen, and a diluent. The diluent may be steam as a dilution steam.

[0057] As discussed, in connection with the ODH reaction of dehydrogenating ethane to ethylene, the by-product formed in the reaction mixture flowing through the tube side may be acetic acid. As further noted, the by-products formed in the reaction mixture flowing through the tube side may also include water, CO2, and CO. Thus, the effluent 308 discharged from the ODH reactor 302 vessel (which may be similar to, for example, effluent 108 of FIG. 1 or process product 208 of FIG. 2) may include ethylene, acetic acid, water, CO2, CO, unreacted ethane, and unreacted diluent (which may be water in some embodiments).

[0058] To remove reaction heat from the reaction mixture flowing through the tube side, the reactor system 300 may include a coolant supply system that supplies a coolant 310 to the shell side of the reactor 302. The coolant 310 introduced to the shell side through the inlet nozzle of the reactor 302 vessel may be referred to as a coolant supply or a low temperature coolant (e.g., low temperature salt for the coolant as a molten salt). Heat transfer may occur from the reaction mixture and ODH catalyst on the tube side to the coolant 310 flowing through the shell side. The heated coolant 312 may be discharged from the reactor 302 from the shell side (e.g., through the reactor vessel outlet nozzle) as a coolant return (high temperature coolant or high temperature salt for the coolant as a molten salt) to the coolant supply system. The coolant supply system may maintain the reaction mixture and the ODH catalyst at a specified temperature. The coolant 310 and the heated coolant 312 may generally have the same composition.

[0059] The heated coolant 312 typically has a higher temperature than the supplied coolant 310. In other words, the coolant experiences a temperature increase (ΔT) across the shell-side. The amount of energy (Q) received by the coolant as heat from the tube-side is given by Q=mc p ΔT, where Q is the energy per time [e.g., kilojoules per second (kJ / s) or kilowatts (kW)], m is the mass flow rate of the coolant per time [e.g., kilograms per second (kg / s)], and c pis the specific heat capacity of the coolant [e.g., in units of (kJ / kg)(1 / °C)], ΔT is the temperature rise of the coolant (e.g., in °C), and Q is the amount of heat accepted by the coolant to maintain the tube side (reaction mixture, ODH catalyst) at a specified temperature.

[0060] Formula Q=mc p As seen in ΔT, for a given Q to maintain the tube side at a specified temperature, the temperature rise of the coolant (ΔT) and the flow rate of the coolant (m) are inversely proportional. Thus, specifying a lower temperature rise of the coolant (ΔT) gives a higher flow rate of the coolant (m) through the shell side. Conversely, specifying a higher temperature rise of the coolant (ΔT) gives a lower flow rate of the coolant (m) through the shell side. The temperature rise of the coolant (ΔT) can be specified to give a sufficient flow rate of the coolant (m) to give a sufficient heat transfer coefficient (e.g., to give a sufficient Reynolds number (Re)). The fluid dynamics of the coolant flowing along the tubes and down the shell side can affect the heat transfer from the reaction mixture on the tube side to the coolant.

[0061] The coolant supply system may include a coolant pump 314 (circulation pump), a control valve 316, and a coolant heat exchanger 318. The coolant pump 314 (e.g., a centrifugal pump) provides the motive force for the circulation of the coolant through the shell side of the reactor 302. The suction (inlet) of the pump 314 receives heated coolant 312 (return conduit) as a suction fluid. The pump 314 exhausts the heated coolant 312 through the control valve 316 and the coolant heat exchanger 318.

[0062] The coolant heat exchanger 318 (e.g., a shell-and-tube heat exchanger) removes heat from the heated coolant 312 to provide a coolant 310 (coolant supply) at a desired (specified) temperature (the inlet temperature of the coolant 312 to the reactor 302). The control valve 316 regulates (modulates, regulates, maintains, changes) the amount of heated coolant 312 flowing through the heat exchanger 318 to provide a coolant 310 supply at a desired temperature. A bypass portion 320 of the heated coolant 312 flows through a bypass conduit that bypasses the coolant heat exchanger 318. The total flow rate of coolant in the coolant supply system and circulation through the shell side of the reactor 302 may generally be substantially constant. This flow rate of coolant provided by the pump 314 through the shell side will be lower at a certain higher temperature rise (ΔT) of the coolant through the shell side. This flow rate of coolant provided by pump 314 through the shell side is greater at a particular lower temperature rise (ΔT) of the coolant through the shell side.

[0063] The ODH reactor 302 vessel may have an effluent outlet for discharging effluent 308 from the ODH reactor 302. The effluent outlet may be a vessel outlet nozzle coupled to an effluent discharge conduit for flowing effluent 308 discharged from the reactor 302. The temperature of the discharged effluent 308 may be in the range of, for example, 300° C. to 500° C., consistent with the operating temperature of the ODH reactor 302 vessel (e.g., 300° C. to 500° C.).

[0064] The effluent heat exchanger 322 is disposed along the effluent discharge conduit. The heat exchanger 322 cools the effluent 308 using the water 324 as a cooling medium. For example, the effluent exchanger 322 may cool the effluent 308 to a temperature in the range of 150° C. to 350° C. (or in the range of 200° C. to 300° C.). The heat exchanger 322 may be referred to as a transfer line exchanger (TLE). In the illustrated implementation, the heat exchanger 322 is a steam generation heat exchanger for generating steam 326 from the water 312 by heating (vaporizing) the water 324 (e.g., liquid water) using the effluent 308 as a heat medium. Thus, the effluent heat exchanger 322 may be characterized as a steam generation heat exchanger. The water 324 may be heated in the heat exchanger 322 with heat from the effluent 308 to flash (vaporize) the water 324 into steam 326. In alternative embodiments, the effluent heat exchanger 322 may heat (preheat) the water 312 for downstream vaporization of the water into steam 326. In these embodiments, the effluent heat exchanger 322 may be characterized as a preheater (e.g., a BFW preheater). The effluent heat exchanger 322 (steam generating heat exchanger) may be, for example, a shell-and-tube heat exchanger or a finned heat exchanger (e.g., having a finned tube bundle), etc. The water 324 may be, for example, desalinated water, condensate steam, or boiler feed water (BFW), etc. The boiler feed water may be treated with desalinated water. The effluent 308 may be cooled, for example, by an amount in the range of 50° C. to 350° C. across the heat exchanger 322.

[0065] The coolant heat exchanger 318 may also be utilized to generate steam 326 from the water 324. Thus, the coolant heat exchanger 318 may be referred to as a steam generating heat exchanger. Similar to the effluent heat exchanger 322, the coolant heat exchanger 318 may be, for example, a shell-and-tube heat exchanger or a finned heat exchanger (e.g., having finned tube bundles), etc.

[0066] In some embodiments, one or both of the heat exchangers 318, 322 may heat (preheat, no vaporization) the water 324 to vaporize the water 324 into steam 326 in the steam drum 328. In these embodiments, one or both of the heat exchangers 318, 322 may receive the water 324 from the steam drum 328 or a boiler feed water (BFW) pump and discharge the heated (preheated) water 324 (generally not steam 326) into the steam drum 328.

[0067] The reactor system 300 may include a steam drum 328 vessel (e.g., a VHP steam drum) for providing water 324 to the heat exchangers 318, 322. The steam drum 328 vessel may have a horizontal orientation (as shown) or a vertical orientation. The steam drum 328 vessel may receive the water 324 from a pump (not shown) (e.g., a boiler feed water pump) via a water supply conduit. The steam drum 328 vessel may have a vessel inlet nozzle for receiving the water 324. The steam drum 328 may discharge the water 324 to the heat exchangers 318, 322 via a vessel outlet nozzle. The motive force for the flow of the water 324 from the steam drum 328 to the heat exchangers 318, 322 (and for the flow of the steam 326 from the heat exchangers 318, 322 to the steam drum 328) may be, for example, a thermosiphon.

[0068] During operation, the level of the water 324 is maintained within the steam drum 328 vessel, such as by a level control, which may include a level control valve on a discharge conduit from the bottom of the steam drum 328 vessel (forming a vessel outlet nozzle for directing the water 324 to the heat exchangers 318, 322), a level sensor in the steam drum 328 vessel, an instrument transmitter for indicating the level measured by the level sensor to a control system, and control logic within the control system for controlling the level control valve to maintain the level at a set point.

[0069] In some implementations, to prevent or reduce the buildup of impurities (e.g., solids) within the steam drum 328 vessel, a small portion of the water 324 discharged from the steam drum 328 vessel (or a slipstream of the water 324) may be sent to a blowdown (e.g., a sewer), indicated at 330. The blowdown may be intermittent.

[0070] The steam 326 generated by the heat exchangers 318, 322 may be sent to a steam drum 328. The steam drum 328 may have a vessel inlet nozzle for receiving the steam 326. The steam 326 generated by the heat exchangers 318, 322 may be low pressure (LP) steam (e.g., 150 pounds per square inch gauge [psig] or less), medium pressure (MP) steam (e.g., in the range of 150 psig to 500 psig), high pressure (HP) steam (e.g., in the range of 500 psig to 900 psig), or very high pressure (VHP) steam (e.g., in the range of 900 psig to 1700 psig), etc. For steam that may be HP steam or VHP steam, the designation HP / VHP steam (e.g., in the range of 500 psig to 1700 psig) is used. In some implementations, the steam 326 is HP / VHP steam. The pressure of the steam generated via the steam generating heat exchanger 310 may be a function of the temperature of the effluent 308 driven by the operating temperature (ODH reaction temperature) of the ODH reactor 302. The operating temperature within the steam drum 328 vessel may be in the range of 240° C. to 330° C. for the steam 314 as HP / VHP steam, for example.

[0071] Higher pressure steam, such as above 500 pounds per square inch gauge (psig) or above 900 psig, may typically be more valuable than lower pressure steam, such as below 500 psig or below 150 psig. In the steam generating heat exchangers 318, 322, the generation of HP or VHP steam may generally be more profitable (worth more) than generating MP or LP steam, and thus may improve the economics of the reactor system 300 and the associated ODH plant. The steam 326 may have different uses. The use of the steam by the consumer or customer receiving the steam may depend on the pressure of the steam. In some implementations, the higher steam pressure of the generated steam may allow more versatility in the integration of the steam within the facility or plant. For example, HP steam may be utilized to power a turbine attached to a compressor, while LP steam is typically used for heating purposes, etc.

[0072] During operation of the steam drum 328, steam 326 entering the steam drum 328 may be discharged upwardly from the steam drum 328 as steam 326. Any liquid water 324 that flashes (vaporizes) within the steam drum 328 may be discharged upwardly as steam 326. The steam 326 discharged upwardly from the steam drum 328 may be saturated steam (or slightly above the saturation temperature). The steam drum 328 may have a vessel outlet nozzle at the top or top of the steam drum 328 vessel to discharge the steam 326. The steam 326 (e.g., saturated steam or near saturated) may be discharged upwardly from the steam drum 328 into a conduit for distribution to a user (e.g., at an ODH plant facility).

[0073] The ODH reactor system 300 may superheat the steam 326 before distributing it to users. In particular, the steam 326 may flow through a superheater 332 heat exchanger before distribution. The steam 326 discharged from the superheater 332 heat exchanger is the steam 326 superheated by the superheater 332. The heat medium of the superheater 332 is a coolant flowing through the shell side of the reactor 302. The symbol shown for the superheater 332 is a heat exchanger symbol. The heat exchanger symbol for the superheater 332 may represent a heat exchanger (e.g., a shell-and-tube heat exchanger or a plate-fin heat exchanger) that is located outside the reactor 302 and where the wake of the coolant is sent from the shell side of the reactor 302 through the superheater 332.

[0074] The heat exchanger symbol for superheater 332 may represent an additional or auxiliary tube bundle (with a dedicated surrounding shell) with a relatively small number of tubes (without ODH catalyst). The additional tube bundle may complement the tube side of reactor 302, with steam 326 flowing through the tubes of the additional tube bundle (second tube bundle). Coolant (wake) from the main shell side of reactor 302 flows through the shell side of the additional tube bundle to heat (superheat) steam 326. The additional tube bundle with its dedicated shell may be attached to the reactor 302 vessel, with the dedicated shell coupled to the shell side of reactor 302 for flowing coolant. The auxiliary tube bundle may be a tube bundle (another tube bundle or a second tube bundle) within the reactor 302 vessel adjacent to the main tube bundle.

[0075] During operation, the additional or auxiliary tube bundle receives steam 326 (e.g., saturated steam) via a steam inlet nozzle. The steam 326 flows through the tubes of the additional tube bundle and is heated by coolant from the shell of the reactor 302. Once the steam 326 is superheated, it is discharged from the reactor 302 from the additional tube bundle. The additional or auxiliary tube bundle attached to the reactor 302 vessel (with its dedicated shell) may have an outlet (superheated steam outlet nozzle) for discharging the superheated steam 326.

[0076] The tubes of the additional or auxiliary tube bundle may generally be parallel to the tubes of the main tube bundle within the main shell of the reactor 302. The additional tubes may typically be separate from the main bundle. The additional tubes may share the shell coolant. In the case of an additional tube bundle mounted external to the reactor 302 vessel, the wake of the main shell coolant may flow as the additional shell coolant.

[0077] FIG. 4 is an ODH reactor system 400 similar to the ODH reactor system 300 of FIG. 3, except that the single ODH reactor 402 has two cooling sections instead of a single shell or single cooling section as in the ODH reactor 302. See FIG. 3 for a description of similar or identical equipment and operation. FIG. 4A is an ODH reactor system 400A similar to the ODH reactor system 400 of FIG. 4, except that the coolant flow is in a countercurrent (rather than cocurrent) flow direction to the reaction mixture flowing through the tube side. Each of the ODH reactor systems 400 and 400A may be the ODH reactor system 102 of FIG. 1. For comparison of the examples of ODH reactor systems disclosed herein, the implementations of the ODH reactor systems 400 and 400A provide the basis for configurations 2-5. In the analytical example, configuration 2 is selected as the base case in the comparison of configurations 1-13.

[0078] The ODH reactor 402 has a first cooling section 404 and a second cooling section 406 separated by a barrier 408 on the shell side of the ODH reactor 402. For the "first" and "second" cooling sections presented herein in various embodiments, the second cooling section is operationally upstream and downstream of the first cooling section in the flow direction of the reaction mixture in the tubes. The flow of coolant through the shell of the first cooling section can be co-current or counter-current to the reaction mixture flowing through the tubes. The flow of coolant through the shell of the second cooling section can be co-current or counter-current to the reaction mixture flowing through the tubes.

[0079] The barrier 408 may be, for example, a metal plate that seals the shell side of the first cooling section 404 from the shell side of the second cooling section 406. Thus, during operation, the coolant in the first cooling section 404 is separated from the coolant in the second cooling section 408. The barrier 408 may have perforations or other openings to allow tubes of the tube bundle to pass through the barrier 408 and thus allow the reaction mixture to flow through both cooling sections 404, 406.

[0080] The cooling section in the ODH reactor may be referred to as a catalyst cooling section for cooling the section where the tubes have a catalyst (ODH catalyst). In FIG. 4, both the first cooling section 404 and the second cooling section are catalyst cooling sections, respectively. The catalyst cooling section may be utilized to cool both the tube-side reaction mixture and the ODH catalyst. For cooling sections where the tubes do not have a catalyst (ODH catalyst), the cooling section may be referred to as a non-catalytic cooling section where the cooling section is utilized to cool the tube-side reaction mixture. For an example of the use of a non-catalytic cooling section, see cooling section 510 in FIG. 5 and cooling section 804 in FIG. 8. For a non-catalytic cooling section, inert particles may be placed in the tubes. In several implementations, the use of a non-catalytic cooling section may be characterized as a coolant quench of the tube-side reaction mixture. In the case of the coolant as a molten salt, the coolant quench may be referred to as a salt quench.

[0081] A feed 410 to the reactor 402 introduced into the tubes (tube side) may provide an initial reaction mixture in the first cooling section 404. The feed 410 may be similar to the feed 104 of FIG. 1. The reaction mixture flows through the tubes. The reaction mixture flowing in the tubes flows from the first cooling section 404 through a barrier 408 into the second cooling section 406. The reaction mixture exiting the tubes (tube side) of the second cooling section 406 may provide an effluent 412 of the ODH reactor 402. The effluent 412 may be similar to the effluent 108 of FIG. 1.

[0082] The first cooling section 404 and the second cooling section 406 may provide a respective isotherm temperature for the reactor 402. In particular, each cooling section 404, 406 may provide or promote a constant temperature for the tube-side reaction mixture and the ODH catalyst, respectively, by removing the heat of reaction (exotherm).

[0083] As described (e.g., with respect to FIG. 3), the coolant supply system of the ODH reactor may include a coolant pump (e.g., a centrifugal pump) that receives coolant from the shell side of the ODH reactor and provides motive force for circulation of the coolant through the shell side. The coolant pump may be configured to provide a specified capacity (coolant circulation flow rate) based on a specified temperature rise of the coolant through the shell side. Specifying a lower temperature rise (e.g., within a range of 2°C to 8°C) results in a configuration of the coolant pump that provides a higher flow rate that is advantageous for increasing the efficiency of heat transfer from the tube side to the shell side. The coolant supply system may include a coolant heat exchanger that cools at least a portion of the coolant to provide a desired or specified coolant supply temperature to the shell side. The coolant supply system may include a control valve (e.g., a flow control valve) for regulating the amount of circulating coolant sent through the coolant heat exchanger (and thus the amount of coolant bypassing the coolant heat exchanger).

[0084] A first coolant supply system 414 circulates a coolant (e.g., molten salt) through the shell side in the first cooling section 404. The first coolant system 414 provides a coolant supply to the first cooling section 404 and receives a coolant return from the first cooling section 404. A second coolant supply system 416 circulates a coolant (e.g., molten salt) through the shell side in the second cooling section 406. The second coolant system 416 provides a coolant supply to the second cooling section 406 and receives a coolant return from the second cooling section 406.

[0085] The coolant heat exchanger in the first coolant supply system and the coolant heat exchanger in the second coolant supply system may each receive water (e.g., BFW) from a steam drum and heat the water (with the coolant as the heat carrier) to vaporize the water and obtain steam (e.g., HP / VHP steam). Similarly, the effluent heat exchanger receives water from the steam drum to cool the effluent 412 and thus vaporize the water (with the effluent 412 as the heat carrier) to obtain steam. As described, the steam may be discharged from the steam drum for distribution to users. Also, as described, the steam may be superheated in a heat exchanger associated with the cooling section (e.g., such as 332 in FIG. 3). In FIG. 4, there are two such heat exchangers associated with the first cooling section 404 and the second cooling section 406, respectively.

[0086] The heat medium of the two superheater heat exchangers is a coolant that flows through the shell side of the first cooling section 404 and the second cooling section 406, respectively. Each superheater heat exchanger may be: [1] a heat exchanger (e.g., a shell-and-tube heat exchanger or a plate-fin heat exchanger) located outside the reactor 402, where the wake of the coolant is routed through the superheater heat exchanger from the shell side; [2] a second tube bundle having some tubes (without ODH catalyst) adjacent to the main tube bundle in the reactor 402, through which steam flows such that the coolant flowing through the shell side in each cooling section 404, 406 heats (superheats) the steam; and / or [3] an attached additional (auxiliary) tube bundle (second tube bundle) (with its own surrounding shell) in which steam flows through the tubes (without ODH catalyst) and the coolant (e.g., wake) from the main shell side of the reactor 402 flows through the shell side of the additional tube bundle to heat (superheat) the steam.

[0087] Generally, in steam generating heat exchangers (e.g., the two coolant and effluent heat exchangers of FIG. 4), the heat exchangers may be configured to heat water (preheat, no vaporization) to vaporize the water into steam in a steam drum. In these embodiments, the heat exchangers may receive water from the BFW pump and discharge heated (preheated) water (generally not steam) into the steam drum.

[0088] The second cooling section 406 is disposed upstream and downstream of the first cooling section 404 in the direction of flow of the tube-side reaction mixture. Thus, the concentration of oxygen in the reaction mixture in the first cooling section 404 may generally be higher than in the reaction mixture in the second cooling section 406. Thus, the more oxygen available in the first cooling section 404, the more likely the reactions in the reaction mixture may include reactions that give carbon monoxide and carbon dioxide. In contrast, oxygen is less concentrated (less available) in the second cooling section 406. Thus, the reactions in the reaction mixture in the second cooling section 404 may be less likely to be reactions that give carbon monoxide and carbon dioxide. An advantage of having two cooling sections in the ODH reactor may be that the tube side can be operated at a lower temperature in the first cooling section 404 to reduce reactions that form carbon monoxide and carbon dioxide in the presence of a higher concentration of oxygen. For example, (1) the reaction mixture and ODH catalyst on the tube side in the first cooling section 404 can be maintained at a temperature in the range of 300°C to 400°C or 300°C to 450°C, and (2) the reaction mixture and ODH catalyst on the tube side in the second cooling section 406 can be maintained at a temperature in the range of 350°C to 500°C.

[0089] Again, the cooling sections 404, 406 and associated coolant supply systems remove the heat of reaction (exotherm) generated in the tube-side reaction mixture. The amount of heat removed can be varied to obtain a specified isotherm temperature. The amount of cooling flowing through each cooling section can be varied to give a specified temperature rise (e.g., within a range of 2°C to 8°C) of the coolant passing through the cooling sections 404, 406.

[0090] FIG. 5 is an ODH reactor system 500 similar to the ODH reactor system 400 of FIG. 4, except that the single ODH reactor 502 has a third cooling section (non-catalytic cooling section) that can be characterized as [1] a coolant (salt) quench and [2] no effluent heat exchanger is used to cool the effluent. See FIGS. 3-4 for a description of similar or identical equipment and operation. The ODH reactor system 500 may be the ODH reactor system 102 of FIG. 1. For comparison of the examples of ODH reactor systems disclosed herein, the implementation of the ODH reactor system 500 provides the basis for configuration 6.

[0091] The ODH reactor 502 has a first cooling section 504 and a second cooling section 506 separated by a barrier 508 on the shell side of the ODH reactor 502. As described, the barrier 508 may be, for example, a metal plate that seals the shell side of the first cooling section 504 from the shell side of the second cooling section 506. Thus, during operation, the coolant (e.g., molten salt) in the first cooling section 504 is separated from the coolant (e.g., molten salt) in the second cooling section 506. The barrier 508 may have perforations or other openings for tubes of the tube bundle to pass through the barrier 508 and thus for the reaction mixture to flow through both cooling sections 504, 506.

[0092] The ODH reactor 502 has a third cooling section 510 on the shell side of the ODH reactor 502 separated from the second cooling section 506 by a barrier 512. Similar to the barrier 508, the barrier 512 (e.g., a metal plate with openings for tubes) seals the shell side of the third cooling section 510 from the shell side of the second cooling section 506. Thus, during operation, the coolant (e.g., molten salt) in the third cooling section 510 is separated from the coolant in the second cooling section 506.

[0093] The reaction mixture flows tube side from the second cooling section 508 through the third cooling section 510. The third cooling section 510 is a non-catalytic cooling section in that the tubes in the third cooling section 510 do not have a catalyst (but may have inert particles disposed therein). Thus, the reaction in the third cooling section 510 may be limited. The purpose of the cooling section 510 may be to cool the reaction mixture flowing through the tubes in the third cooling section 510 before the reaction mixture is discharged as effluent 514. Thus, in some implementations, the third cooling section 510 may be implemented in place of an effluent heat exchanger that cools the effluent 514. The effluent 514 may be similar to the effluent 108 of FIG. 1. In some implementations, the third cooling section 510 may cool the effluent 514 to a temperature in the range of 150° C. to 350° C. (or in the range of 200° C. to 300° C.).

[0094] A feed 516 to the reactor 502 introduced into the tubes (tube side) may provide an initial reaction mixture at the first cooling section 504. The feed 516 may be similar to the feed 104 of FIG. 1. The reaction mixture flows within the tubes. The tubes are fed through barriers 508 and 512. The barriers 508 and 512 are not inside the tubes. The reaction mixture flows within the tubes across the barrier 508 from the first cooling section 504 to the second cooling section 506. The reaction mixture flows within the tubes across the barrier 512 from the second cooling section 506 to the third cooling section 510. The reaction mixture exiting the tubes (tube side) of the third cooling section 510 may provide an effluent 514 of the ODH reactor 502.

[0095] Each of the cooling sections 504, 506 may provide a respective isotherm temperature for the reactor 502. In particular, the cooling sections 504, 506 may provide or facilitate a respective constant temperature for the tube-side reaction mixture and the ODH catalyst. As discussed above, the third cooling section 510 may cool the reaction mixture for discharge as an effluent 514 having a temperature in the range of 150°C to 350°C (or in the range of 200°C to 300°C). The third cooling section 510 may be in lieu of a TLE and thus may act more literally as a HEX, but the third cooling section 510 may approach isothermal on the coolant (molten salt) side, but the coolant may have an elevated temperature with less molten salt coolant circulation. The third cooling section 510 (e.g., in lieu of a TLE) may reduce the temperature of the tube-side reaction mixture, for example, from 450°C to 150°C to 200°C.

[0096] As described (e.g., with respect to Figs. 3-4), the coolant supply system of the ODH reactor may include a coolant pump (e.g., a centrifugal pump) that receives coolant from the shell side of the ODH reactor and provides motive force for circulation of the coolant through the shell side. The coolant pump may be configured to provide a specified capacity (coolant circulation flow rate) based on a specified temperature rise of the coolant through the shell side. Specifying a lower temperature rise (e.g., within a range of 2°C to 8°C) results in a configuration of the coolant pump that provides a higher flow rate that is advantageous for increasing the efficiency of heat transfer from the tube side to the shell side. The coolant supply system may include a coolant heat exchanger that cools at least a portion of the coolant to provide a desired or specified coolant supply temperature to the shell side. The coolant supply system may include a control valve (e.g., a flow control valve) for regulating the amount of circulating coolant sent through the coolant heat exchanger (and thus the amount of coolant bypassing the coolant heat exchanger).

[0097] In FIG. 5 , a first coolant supply system circulates a coolant (e.g., molten salt) through the shell side in the first cooling section 504. The first coolant supply system provides a coolant supply to the first cooling section 504 and receives a coolant return from the first cooling section 504. The second coolant supply system circulates a coolant (e.g., molten salt) through the shell side in the second cooling section 506. The second coolant supply system provides a coolant supply to the second cooling section 506 and receives a coolant return from the second cooling section 506. The third coolant supply system circulates a coolant (e.g., molten salt) through the shell side in the third cooling section 510. The third coolant supply system provides a coolant supply to the third cooling section 510 and receives a coolant return from the third cooling section 510.

[0098] The coolant heat exchanger in the first coolant supply system and the coolant heat exchanger in the second coolant supply system may each receive water (e.g., BFW) from a steam drum, heat the water (using the coolant as a heat medium) to vaporize the water, and provide steam (e.g., HP / VHP steam) to the steam drum. The coolant heat exchanger in the third coolant supply system heats water (e.g., BFW) using the coolant as a heat medium, and delivers the heated water to the steam drum.

[0099] As explained, steam may be discharged from the steam drum for distribution to a user. Also as explained, the steam may be superheated in a heat exchanger associated with a cooling section (e.g., such as 332 in FIG. 3) prior to distributing the steam to a user. In FIG. 5, there are two such heat exchangers associated with a first cooling section 504 and a second cooling section 506, respectively.

[0100] The heat medium of the two superheater heat exchangers is a coolant that flows through the shell side of the first cooling section 504 and the second cooling section 506, respectively. Each of the superheater heat exchangers may be: [1] a heat exchanger (e.g., a shell-and-tube heat exchanger or a plate-fin heat exchanger) located outside the reactor 502, where the wake of the coolant is routed through the superheater heat exchanger from the shell side; [2] a second tube bundle having some tubes (without ODH catalyst) adjacent to the main tube bundle in the reactor 502, through which steam flows such that the coolant flowing through the shell side in each cooling section 504, 506 heats (superheats) the steam; and / or [3] an attached additional (auxiliary) tube bundle (second tube bundle) (with its own surrounding shell) in which steam flows through the tubes (without ODH catalyst) and the coolant (e.g., wake) from the main shell side of the reactor 402 flows through the shell side of the additional tube bundle to heat (superheat) the steam.

[0101] Generally, in a steam generating heat exchanger (e.g., the two coolant heat exchangers of FIG. 5), the heat exchanger may instead be configured to heat water (preheat, no vaporization) to vaporize the water into steam in a steam drum. In these embodiments, the heat exchanger may receive water from the BFW pump and discharge heated (preheated) water (generally not steam) into the steam drum.

[0102] The second cooling section 506 is disposed upstream and downstream of the first cooling section 504 in the flow direction of the tube side reaction mixture. Thus, the concentration of oxygen in the reaction mixture in the first cooling section 504 may generally be higher than in the reaction mixture in the second cooling section 506. Thus, the more oxygen is available in the first cooling section 504, the more likely the reactions in the reaction mixture may include reactions that give carbon monoxide and carbon dioxide. In contrast, oxygen is less concentrated (less available) in the second cooling section 506. Thus, the reactions in the reaction mixture in the second cooling section 504 may be less likely to be reactions that give carbon monoxide and carbon dioxide. The advantage of having two cooling sections with OHD catalysts in the tubes of the ODH reactor may be that the tube side can be operated at a lower temperature in the first cooling section 504 to reduce reactions that form carbon monoxide and carbon dioxide in the presence of a higher concentration of oxygen. For example, (1) the tube-side reaction mixture and ODH catalyst in the first cooling section 504 can be maintained at a temperature in the range of 300° C. to 450° C., and (2) the tube-side reaction mixture and ODH catalyst in the second cooling section 506 can be maintained at a temperature in the range of 350° C. to 500° C. The third cooling section 510 is disposed operatively upstream and downstream of the second cooling section 506 in the direction of flow of the tube-side reaction mixture.

[0103] FIG. 6 is an ODH reactor system 600 similar to the ODH reactor system 500 of FIG. 5, except that the third cooling section of the single ODH reactor 602 has an ODH catalyst and the ODH reactor system 600 includes an effluent heat exchanger for cooling the effluent. For a description of similar or identical equipment and operation, see FIGS. 3-5. The ODH reactor system 600 may be the ODH reactor system 102 of FIG. 1. For comparison of the examples of ODH reactor systems disclosed herein, the implementation of the ODH reactor system 600 provides the basis for configuration 7. The inclusion of the third cooling section may provide better control of the ODH catalytic reaction, and therefore may beneficially produce less CO and CO2. Increasing the number of cooling sections (catalyst cooling sections) may result in better selectivity to ethylene, since the tube side may be operated at a lower temperature in the upstream cooling section to reduce reactions that form CO and CO2 in the presence of higher concentrations of oxygen. Generally, the temperature of the reaction mixture may increase from one cooling section to the next.

[0104] Having more cooling sections in the same ODH reactor may achieve better performance in some implementations. However, as the number of cooling sections increases, the ODH reactor system may become more complex. In certain examples, the increased complexity may not be desirable. Although more than two cooling sections may be implemented in a single reactor, certain implementations may have up to two cooling sections in a single reactor. In the case of an ODH reactor system as a multi-reactor system with two reactors in series, one example is that the first reactor has two catalyst cooling sections and one inert cooling section (salt quench), and the second reactor in series has two catalyst cooling sections. This scenario or reactor system configuration may be applicable to any number of reactors in series (the last reactor with two catalyst cooling sections, and the previous stage with two catalyst cooling sections and one salt quench section). Of course, other configurations are also applicable.

[0105] In the ODH reactor system 600, the ODH reactor 602 has a first cooling section 604, a second cooling section 606, and a third cooling section 608. The second cooling section 606 is disposed operatively upstream and downstream of the first cooling section 604 in the direction of flow of the reaction mixture. The third cooling section 608 is disposed operatively upstream and downstream of the second cooling section 606 in the direction of flow of the reaction mixture.

[0106] A barrier 610 (e.g., a metal plate with perforations for the tubes) separates the first cooling section 604 and the second cooling section 606 on the shell side of the reactor 602. A barrier 612 (e.g., a metal plate with perforations for the tubes) separates the second cooling section 606 and the third cooling section 608 on the shell side of the reactor 602. The reaction mixture flows through the tubes on the tube side through the three cooling sections 604, 606, 608 and the flow is unaffected by the barriers 610, 612. The ODH catalyst is disposed within the tubes in the three cooling sections 604, 606, 608.

[0107] The feed 614 to the reactor 602 introduced into the tubes (tube side) may provide the initial reaction mixture upon entering the first cooling section 604. The feed 614 may be similar to the feed 104 of FIG. 1. The reaction mixture flows through the tubes. The tubes are sent through the barriers 610, 612. The barriers 610, 612 are not inside the tubes. Again, the flow of the reaction mixture is not affected by the barriers 610, 612. The reaction mixture flowing in the tubes flows from the first cooling section 604 across the barrier 610 into the second cooling section 606. The reaction mixture flows in the tubes from the second cooling section 606 across the barrier 612 into the third cooling section 608. The reaction mixture exiting the tubes (tube side) of the third cooling section 608 may provide the effluent 616 of the ODH reactor 602. The reaction mixture from the third cooling section 608 is discharged as effluent 616. The effluent 616 may be similar to effluent 108 of FIG.

[0108] Each of the cooling sections 604, 606, 608 may provide a respective isotherm temperature for the reactor 602. In particular, each of the cooling sections 604, 606, 608 may provide or facilitate a respective constant temperature for the tube side reaction mixture and the ODH catalyst. For example, this temperature may be in the range of 300° C. to 450° C. for the first cooling section 604 and in the range of 350° C. to 500° C. for the cooling sections 606, 608.

[0109] As described (e.g., with respect to FIGS. 3-5), the coolant supply system of the ODH reactor may include a coolant pump (e.g., a centrifugal pump) that receives coolant from the shell side of the ODH reactor and provides motive force for circulation of the coolant through the shell side. The coolant pump may be configured to provide a specified capacity (coolant circulation flow rate) based on a specified temperature rise of the coolant through the shell side. The coolant supply system may include a coolant heat exchanger that cools at least a portion of the coolant to provide a desired or specified coolant supply temperature to the shell side. The coolant supply system may include a control valve (e.g., a flow control valve) to adjust the amount of circulating coolant sent through the coolant heat exchanger.

[0110] In FIG. 6, a first coolant supply system circulates a coolant (e.g., molten salt) through the shell side in the first cooling section 604 via a coolant pump, thus providing a coolant supply to the first cooling section 604 and accepting a coolant return from the first cooling section 604 (to the coolant pump). A second coolant supply system circulates a coolant (e.g., molten salt) through the shell side in the second cooling section 606 via a coolant pump, thus providing a coolant supply to the second cooling section 606 and accepting a coolant return from the first cooling section 606 (to the coolant pump suction). A third coolant supply system circulates a coolant (e.g., molten salt) through the shell side in the third cooling section 608 via a coolant pump, thus providing a coolant supply to the third cooling section 608 and accepting a coolant return from the third cooling section 608 (to the coolant pump inlet).

[0111] Each of the respective coolant heat exchangers in each of the first coolant supply system, the second coolant supply system, and the third coolant supply system may receive water (e.g., BFW) from the steam drum, heat the water (with the coolant as the heat carrier) to vaporize the water, and provide steam (e.g., HP / VHP steam) to the steam drum. The effluent heat exchanger 618 (located along the effluent discharge conduit from the reactor 602) may receive water from the steam drum, heat the water (with the effluent 616 as the heat carrier) to vaporize the water, and provide steam (e.g., HP / VHP steam) to the steam drum. Thus, the effluent heat exchanger 618 may beneficially cool (remove heat from) the effluent 616. In some implementations, the effluent heat exchanger 618 may cool the effluent 616, for example, to a temperature in the range of 150° C. to 350° C. (or in the range of 200° C. to 300° C.).

[0112] As described, steam may be discharged from the steam drum for distribution to a user. Also as described, the steam may be superheated in a heat exchanger associated with a cooling section (e.g., such as 332 in FIG. 3 ) prior to distributing the steam to a user. In FIG. 6 , there are two such heat exchangers associated with the first cooling section 604 and the second cooling section 606, respectively. A third such heat exchanger (superheater) (not shown) may also be associated with the third cooling section 608.

[0113] The heat medium of the two superheater heat exchangers is a coolant that flows through the shell side of the first cooling section 604 and the second cooling section 606, respectively. Each of these two superheater heat exchangers may be configured as described with respect to the corresponding superheater heat exchangers of Figures 3-5. The third superheater heat exchanger coupled to the third cooling section 608 may be similarly configured as described above. In general, the number of such superheater heat exchangers for the reactor system 600 may be one associated with one cooling section, two associated with two cooling sections respectively, or three associated with three cooling sections respectively. A coolant (e.g., molten salt) is utilized to superheat the steam.

[0114] FIG. 7 is an ODH reactor system 700 similar to the ODH reactor systems of FIGS. 3-6, except that the ODH reactor system 700 is not a single reactor system. Instead, the ODH reactor system 700 is a multi-reactor system having two ODH reactors 704, 706 operatively arranged in series. See FIGS. 3-6 for a description of similar or identical equipment and operation. The ODH reactor system 700 may be the ODH reactor system 102 of FIG. 1. For comparison of the examples of ODH reactor systems disclosed herein, the implementation of the ODH reactor system 700 provides the basis for configuration 8.

[0115] The first ODH reactor 702 and the second ODH reactor 704 are each multi-tubular fixed-bed reactors with two cooling sections on the reactor shell side that use a coolant such as molten salt to cool the tube-side reaction mixture and ODH catalyst. The cooling sections 710, 712, 742, 744 may provide or promote respective isotherm temperatures (constant temperatures) of the tube-side reaction mixture and ODH catalyst. For example, the tube-side temperature may be maintained in the range of 300°C to 450°C in the first cooling section 710, 742 and in the range of 350°C to 500°C in the second cooling section 712, 744.

[0116] The two cooling sections in each reactor 702, 704 are separated by respective barriers on the shell side (sealing the shell side between the cooling sections). The reaction mixture flows through the tubes (tube side) through each barrier. The tubes (tube side) in the four cooling sections contain the ODH catalyst.

[0117] The first ODH reactor 702 is disposed operatively upstream of the second ODH reactor 704. The first ODH reactor 702 receives a feed 706, which may be similar to the feed 104 of FIG. 1. The feed 706 may beneficially have less oxygen gas (and therefore less dilution steam) since oxygen 708 gas is injected between the reactors 702, 704. This may be an advantage of a multiple reactor system compared to a single reactor system. The feed 706 may contain an appropriate amount of oxygen (or more) for the OHD reaction in the first ODH reactor 702.

[0118] A feed 706 (first reactor feed) introduced into the first ODH reactor 702 provides an initial reaction mixture that flows through the tube side. The reaction mixture (tube side) flows through a first cooling section 710 of the first reactor 702 and a second cooling section 712 of the first reactor 702. The second cooling section 712 is located operationally upstream and downstream of the first cooling section 710.

[0119] A first coolant supply system 714 provides a first coolant as a coolant supply to the reactor shell side in the first cooling section 710 and receives the first coolant as a coolant return from the reactor shell side in the first cooling section 710. A second coolant supply system 716 provides a second coolant as a coolant supply to the reactor shell side in the second cooling section 712 and receives the second coolant as a coolant return from the reactor shell side in the second cooling section 712. Both the first and second coolants may be, for example, molten salts.

[0120] The first coolant supply system 714 may include a first coolant pump 718, a first coolant control valve 720, and a first coolant heat exchanger 722 that cools the first coolant using water 724 as a cooling medium. The first coolant pump 718 (e.g., a centrifugal pump) as a first coolant circulation pump may be configured such that the flow rate (circulation rate) of the first coolant provides a specified temperature rise of the first coolant through the shell side in the first cooling section 710. The first coolant control valve 720 (e.g., a flow control valve) may adjust the amount (flow rate) of the first coolant sent through the first coolant heat exchanger 722. The first coolant heat exchanger 722 (e.g., a shell-and-tube heat exchanger) may remove the reaction heat received by the first coolant on the reactor shell side to provide a desired supply temperature of the first coolant to the reactor shell side.

[0121] The second coolant supply system 716 may include a second coolant pump 726, a second coolant control valve 728, and a second coolant heat exchanger 730 that cools the second coolant using water 724 as a cooling medium. The second coolant pump 726 (e.g., a centrifugal pump) as a second coolant circulation pump may be configured such that the flow rate (circulation rate) of the second coolant provides a specified temperature rise of the second coolant through the shell side in the first cooling section 710. The second coolant control valve 728 (e.g., a flow control valve) may adjust the amount (flow rate) of the second coolant sent through the second coolant heat exchanger 730. The second coolant heat exchanger 730 (e.g., a shell-and-tube heat exchanger) may remove the reaction heat received by the second coolant on the reactor shell side to provide a desired supply temperature of the second coolant on the reactor shell side.

[0122] The first coolant heat exchanger 722 and the second coolant heat exchanger 730 may each receive water 724 from a steam drum 732 vessel and vaporize the water 724 into steam 734 that is delivered to the steam drum 732. The water 724 is provided to the steam drum 732 from a source (not shown). In the case of water 724 as boiler feed water (BFW), the source may be a BFW pump.

[0123] The reaction mixture exits the first ODH reactor 702 from the tube side as first ODH reactor 702 effluent 736. This effluent 736 may include ethylene, acetic acid (vapor), CO, CO2, water (vapor), unreacted ethane, and residual oxygen. The effluent 736 may exit the first ODH reactor 702 through an effluent discharge conduit. This effluent discharge conduit may carry the effluent 736 to the feed inlet of the second ODH reactor 702. Thus, the effluent discharge conduit from the first ODH reactor 702 may function as a feed conduit to the second ODH reactor 702.

[0124] Liquid water 738 is added (injected) into the effluent 736 as a water quench of the effluent 736 to cool the effluent 736. In particular, the vaporization of the added liquid water 738 in the effluent 738 consumes heat in the effluent 736 to cool the effluent 736. In other words, the sensible heat of the effluent 736 may provide the latent heat of vaporization to vaporize the injected liquid water 738, thereby cooling the effluent 736. In some implementations, the liquid water supply conduit conveys the liquid water 738 to an effluent discharge conduit that conveys the effluent 736. A tee may couple the liquid water supply conduit with the effluent discharge conduit for addition (injection) of the liquid water 738 into the effluent 736. Water quenching via injected liquid water 738 may cool the effluent 736, for example, to a temperature in the range of 150° C.-350° C. (or in the range of 200° C.-300° C.). After water quenching, O2 may be injected into the effluent 736. The purpose of cooling the effluent 736 (whether by water quenching as shown or by other cooling techniques) may be to avoid spontaneous ignition of the hydrocarbons and acetic acids (which may be at or near their autoignition temperatures) due to the addition of O2, and to avoid associated undesirable reactions (e.g., combustion and production of CO and CO2).

[0125] Oxygen 708 gas may be added (injected) to the effluent 736. The amount of oxygen 708 added to the effluent 736 provides oxygen for the ODH reaction in the second ODH reactor 704. (The amount of oxygen gas included in the upstream feed 706 to the first ODH reactor 702 may be appropriate for the ODH reaction in the reaction mixture in the first ODH reactor 702.) In some implementations, the oxygen supply conduit carries the oxygen 708 gas to an effluent discharge conduit that carries the effluent 736. A tee may couple the oxygen supply conduit with the effluent discharge conduit for addition (injection) of oxygen 708 to the effluent 736.

[0126] In the illustrated embodiment, the feed 740 provided to the second ODH reactor 704 includes the first reactor effluent 736, vaporized added liquid water 738, and added oxygen 708 gas. The effluent discharge conduit from the first ODH reactor 702 may be a feed conduit that couples to a feed inlet (e.g., a vessel inlet nozzle) of the second ODH reactor 704, or may couple to a feed conduit.

[0127] The feed 740 (second reactor feed) introduced into the second ODH reactor 704 provides an initial reaction mixture for the second ODH reactor 704 that flows through the tube side. The reaction mixture (tube side) flows through a first cooling section 742 of the second ODH reactor 704 and a second cooling section 744 of the second ODH reactor 702. The second cooling section 744 is located operationally upstream and downstream of the first cooling section 742. In the context of the ODH reactor system 100, the first cooling section 742 can be referred to as the third cooling section and the second cooling section 744 can be referred to as the fourth cooling section of the four cooling sections.

[0128] A third coolant supply system 746 provides a third coolant as a coolant supply to the reactor 704 shell side in the first cooling section 742 and receives the first coolant as a coolant return from the reactor 704 shell side in the first cooling section 710. A fourth coolant supply system 748 provides a fourth coolant as a coolant supply to the reactor 704 shell side in the second cooling section 744 and receives the fourth coolant as a coolant return from the reactor 704 shell side in the second cooling section 744. Both the third coolant and the fourth coolant may each be, for example, a molten salt.

[0129] The third coolant supply system 746 may include a third coolant pump 750, a third coolant control valve 752, and a third coolant heat exchanger 754. The third coolant heat exchanger 754 cools the third coolant using water 724 as a cooling medium. The third coolant pump 750 (e.g., a centrifugal pump) as a third coolant circulation pump may be configured such that the flow rate (circulation rate) of the third coolant provides a specified temperature rise of the third coolant passing through the shell side in the first cooling section 742. The third coolant control valve 752 (e.g., a flow control valve) may adjust the amount (flow rate) of the third coolant sent through the third coolant heat exchanger 754. The third coolant heat exchanger 754 (e.g., a shell-and-tube heat exchanger) may remove the heat of reaction received by the third coolant on the shell side of the reactor 704 to provide a desired supply temperature of the third coolant on the shell side of the reactor 704.

[0130] The fourth coolant supply system 748 may include a fourth coolant pump 756, a fourth coolant control valve 758, and a fourth coolant heat exchanger 760 that cools the fourth coolant using water 724 as a cooling medium. The fourth coolant pump 756 (e.g., a centrifugal pump) as a fourth coolant circulation pump may be configured such that the flow rate (circulation rate) of the fourth coolant provides a specified temperature rise of the fourth coolant through the shell side in the second cooling section 744. The fourth coolant control valve 758 (e.g., a flow control valve) may adjust the amount (flow rate) of the fourth coolant sent through the fourth coolant heat exchanger 760. The fourth coolant heat exchanger 760 (e.g., a shell-and-tube heat exchanger) may remove the reaction heat received by the fourth coolant on the reactor 704 shell side to provide a desired supply temperature of the second coolant on the reactor 704 shell side.

[0131] The third coolant heat exchanger 754 and the fourth coolant heat exchanger 760 may each receive water 724 from the steam drum 732 vessel and vaporize the water 724 (with the coolant as the heat carrier) into steam 734 that is sent to the steam drum 732. Additionally, the effluent heat exchanger 762 may heat the water 724 and vaporize it (with the effluent 764 from the second ODH reactor 704 as the heat carrier) into steam 734 that is sent to the steam drum 732.

[0132] The reaction mixture is discharged from the second ODH reactor 704 from the tube side as effluent 762. The effluent 762 may be a product effluent similar to effluent 108 of FIG. 1. The effluent 762 may include ethylene, acetic acid (vapor), CO, CO2, water (vapor or steam), and unreacted ethane. The effluent 762 may be discharged from the second ODH reactor 704 through an effluent discharge conduit. The effluent discharge conduit may be coupled to an effluent outlet nozzle of the second ODH reactor 704 to receive the effluent 762. The effluent heat exchanger 762 described above may be disposed along the effluent discharge conduit carrying the effluent 764. The effluent heat exchanger 762 may cool the effluent 762 using water 724 as a cooling medium. As described above, the effluent heat exchanger 762 may use the effluent 762 as a heat medium to vaporize the water 724 to generate steam 734 .

[0133] In an implementation of ODH reactor system 700, steam 734 generated in heat exchangers 722, 730, 754, 760, and 762 may be HP / VHP steam. Thus, steam drum 732 vessel may operate at HP / VHP (e.g., pressures in the range of 500 psig to 1700 psig). Thus, steam 734 discharged from steam drum 732 for distribution may be HP / VHP steam, which is generally saturated steam. Thus, steam 734 discharged from steam drum 732 may be at a temperature (saturation temperature) in the range of, for example, 240° C. to 330° C.

[0134] The ODH reactor system 700 may heat the steam 734 to a temperature above the saturation temperature to obtain the steam 734 as superheated steam (HP / VHP) for distribution. In particular, the superheater heat exchangers 766, 768, 770, and 772 may receive the steam 734 from the steam drum 732 and heat the steam 734 to superheat the steam 734 (using the reactor shell-side coolant as a heat medium). Although the superheater heat exchangers are shown receiving the seam 734 in parallel, they may be operatively arranged in series. As shown, each heat exchanger 766, 768, 770, 772 may be associated with a respective cooling section 710, 712, 742, 744. Each of these four superheater heat exchangers 766, 768, 770, 772 may be configured as described with respect to the corresponding superheater heat exchanger of FIGS. 3-6.

[0135] FIG. 8 is an ODH reactor system 800 that is the same or similar to the ODH reactor system 700 of FIG. 7, except that the first ODH reactor 802 has a third cooling section 804 (without catalyst) instead of a water quench between the ODH reactors of FIG. 7. In the case of a coolant as a molten salt, the third cooling section 804 can be characterized as a salt quench. An advantage of the third cooling section 804 may be that heat removed from the reaction mixture can be recovered to generate steam via a coolant heat exchanger. In contrast, in the case of a water quench, the removed heat may be lost in the vaporization of water. Additionally, as explained, cooling of the effluent prior to interstage O2 addition can be beneficial to lower the temperature of the effluent components (e.g., acetic acid) below their autoignition temperature (if above their autoignition temperature), thus preventing autoignition (and associated combustion of materials such as ethane, ethylene, acetic acid, CO, etc.).

[0136] For an explanation of generally similar or identical equipment and operations regarding ODH reactor system 800, see Figures 3-7. ODH reactor system 800 may be ODH reactor system 102 of Figure 1. For comparison of the example ODH reactor systems disclosed herein, the implementation of ODH reactor system 800 provides the basis for configuration 9.

[0137] The third cooling section 804 (of the first ODH reactor 802) may be a non-catalytic cooling section in that there may be no catalyst present (but inert particles may be disposed) in the tubes within the third cooling section 804. This third cooling section 804 and an associated fifth coolant supply system (which circulates a fifth coolant through the reactor shell side within the third cooling section 804) provide a respective isotherm in that the reaction mixture flowing through the tubes within the third cooling section 804 is maintained at a specified temperature, for example, within the range of 150° C. to 350° C. (or within the range of 200° C. to 300° C.).

[0138] A fifth coolant heat exchanger (for a fifth coolant, e.g., molten salt) in a fifth coolant supply system associated with the third cooling section 804 preheats water (e.g., BFW) for vaporizing the water in the steam drum. Water may be provided from a pump, typically at the operating pressure of the steam drum (e.g., HP / VHP). Water may flow from a pump (e.g., BFW pump) through the fifth coolant heat exchanger to the steam drum.

[0139] Again, the water level may be maintained within the steam drum. Steam may be discharged from the steam drum for distribution to users. After being discharged from the steam drum, the steam may be superheated in a superheater heat exchanger, for example as described with respect to FIG. 7, before being distributed to users.

[0140] The first ODH reactor 802 receives a feed 806, which may be the same as or similar to the feed 706 of FIG. 7. The feed 806 enters the tube side of the first ODH reactor 802, providing a flowing reaction mixture within the tubes. The reaction mixture flows through first and second cooling sections of the first reactor 802, as in the ODH reactor system 700 of FIG. 7. However, in reactor system 800, the reaction mixture further flows through the tube side of a third cooling section 804 of the first ODH reactor 802. Again, the reactor tubes within the third cooling section 804 may be free of catalyst.

[0141] The reaction mixture is discharged from the first ODH reactor 802 from the tube side as effluent 808 (first reactor effluent) to feed the tube side of the second ODH reactor 810. The effluent 808 may be of similar or the same composition as the effluent 736 of FIG. 7, but is typically at a lower temperature than the discharged effluent 736 due to the presence of the third cooling section 804 of the first ODH reactor 802 of FIG. 8. As with the ODH reactor system 700 of FIG. 7, oxygen gas may be injected into the effluent 808. However, injecting liquid water for water quenching into the effluent as in FIG. 7 may be avoided since the third cooling section 804 cools the reaction mixture that is discharged as effluent 808. The effluent 808 and the injected oxygen enter the second ODH reactor 810 as feed to give the reaction mixture that flows through the tube side. The reaction mixture flows in tubes through two cooling sections and through an effluent heat exchanger as effluent 812, as in FIG. 7. The effluent 812 may be the same as or similar to effluent 764 of FIG. 7. The effluent 812 may be similar to effluent 108 of FIG. 1. As in FIG. 7, the effluent heat exchanger and four coolant heat exchangers generate steam from water received from the steam drum and discharge the steam to the steam drum. The four superheater heat exchangers superheat the steam discharged from the steam drum for distribution.

[0142] 9 is an ODH reactor system 900 that is the same or similar to the ODH reactor system 700 of FIG. 7, except that an effluent heat exchanger 902 (instead of an injected water quench) cools the effluent 904 discharged from the first ODH reactor 906. An advantage of the effluent heat exchanger 902 may be that heat removed from the effluent 904 can be recovered to preheat water (e.g., BFW) for steam generation. In contrast, with an injected water quench, the removed heat may be lost to vaporization of the injected water in the effluent 904.

[0143] For an explanation of generally similar or identical equipment and operations regarding ODH reactor system 900, see Figures 3-8. ODH reactor system 900 may be ODH reactor system 102 of Figure 1. For comparison of the examples of ODH reactor systems disclosed herein, the implementation of ODH reactor system 900 provides a basis for configuration 10.

[0144] The effluent heat exchanger 902 (e.g., a shell-and-tube heat exchanger) may cool the effluent 904 with water (e.g., BFW) to a specified temperature, e.g., in the range of 150°C to 350°C (or in the range of 200°C to 300°C). The effluent heat exchanger 902 may receive water (e.g., from a BFW pump) and heat the water (in cooling the effluent) that preheats the water to vaporize the water in the steam drum. Water may be provided to the effluent heat exchanger 902 generally at the operating pressure of the steam drum (e.g., HP / VHP). Water may flow from a pump (e.g., a BFW pump) through the effluent heat exchanger 902 to the steam drum.

[0145] The water level may be maintained in the steam drum as described. Steam may be discharged from the steam drum for distribution to users. After being discharged from the steam drum, the steam may be superheated in a superheater heat exchanger before being distributed to users as described with respect to FIG.

[0146] The first ODH reactor 906 receives a feed 908, which may be the same as or similar to the feed 706 of FIG. 7. The feed 908 enters the tube side of the first ODH reactor 906, providing a flowing reaction mixture within the tubes. The reaction mixture flows through first and second cooling sections of the first reactor 906, as in the ODH reactor system 700 of FIG. 7, and is discharged as effluent 904 (first reactor effluent). However, as in FIG. 7, liquid water is not injected into the effluent 904. Instead, an effluent heat exchanger 902 (not in FIG. 7 for the first reactor effluent) cools the effluent 904. Again, it may be desirable to cool the effluent 904, e.g., to cool any components approaching or exceeding their autoignition temperature well below their autoignition temperature.

[0147] The reaction mixture exits the first ODH reactor 902 from the tube side as effluent 902 (first reactor effluent) to feed the tube side of the second ODH reactor 910. The effluent 904 may have the same or similar composition as the effluent 736 of FIG. 7. As with the ODH reactor system 700 of FIG. 7, oxygen gas may be injected into the effluent 904 to provide a feed 912 to the second ODH reactor 910. However, again, injecting liquid water into the effluent for water quenching as in FIG. 7 may be avoided since the effluent heat exchanger 902 cools the effluent 904. The effluent 904 and the injected oxygen enter the second ODH reactor 910 as feed 912 to provide the reaction mixture that flows through the tube side. The reaction mixture flows in the tubes through two cooling sections of the second ODH reactor 910, as in FIG. 7, and exits the second ODH reactor 910 tube-side as effluent 914 (second reactor effluent) through effluent heat exchanger 916. The effluent 914 may be the same as or similar to effluent 764 of FIG. 7. The effluent 914 may be similar to effluent 108 of FIG. 1. As in FIG. 7, the effluent heat exchanger 916 and four coolant heat exchangers generate steam from water received from the steam drum and discharge the steam to the steam drum. The four superheater heat exchangers (described above) superheat the steam discharged from the steam drum for distribution.

[0148] FIG. 10 is an ODH reactor system 1000 that is the same or similar to the ODH reactor system 700 of FIG. 7, except that the ODH reactor system 1000 has a third ODH reactor 1002 operatively disposed in series downstream of the second ODH reactor 1004. Thus, the ODH reactor system 1000 has three ODH reactors in series. In this embodiment of the ODH reactor system, the number "n" of ODH reactors in series can be greater than three. A larger number "n" of ODH reactors in series can be advantageous from the perspective of ODH plant performance and energy considerations. However, a larger number "n" of ODH reactors in series can increase the operational complexity and capital costs of the ODH reactor system.

[0149] In ODH reactor system 1000, effluent 1006 (third reactor effluent) discharged from third ODH reactor 1002 is a product effluent similar to effluent 108 of Figure 1. Effluent 1008 discharged from second ODH reactor 1004 is fed to third ODH reactor 1002. Similar to effluent 1010 (first reactor effluent) discharged from first ODH reactor 1012 in the series of three ODH reactors of ODH reactor system 1000, both liquid water (for water quench cooling) and oxygen may be injected into effluent 1008 (second reactor effluent).

[0150] The fifth coolant supply system circulates a fifth coolant (via a coolant pump) through the shell side in the first cooling section of the third ODH reactor 1002. The fifth coolant supply system removes heat from the circulating fifth coolant through a coolant heat exchanger (with water as the cooling medium) that also produces steam from water (e.g., BFW). The coolant heat exchanger receives water from a steam drum and discharges the produced steam to the steam drum.

[0151] Similar to the other coolant supply systems described above, the sixth coolant supply system circulates a sixth coolant (via a coolant pump) through the shell side in the second cooling section of the third ODH reactor 1002. The sixth coolant supply system removes heat from the circulating sixth coolant through a coolant heat exchanger (with water as the cooling medium) that also produces steam from water (e.g., BFW). The coolant heat exchanger receives water from a steam drum and discharges the produced steam to the steam drum. The sixth coolant and the fifth coolant may each be, for example, a molten salt.

[0152] For an explanation of generally similar or identical equipment and operations regarding ODH reactor system 1000, see Figures 3-9. ODH reactor system 1000 may be ODH reactor system 102 of Figure 1. For comparison of the examples of ODH reactor systems disclosed herein, the implementation of ODH reactor system 1000 provides the basis for configuration 11.

[0153] Similar to the ODH reactor system 700 of Figure 7, the first ODH reactor 1012 receives a feed 1014 similar to the feed 104 of Figure 1. Advantageously, the feed 1014 may have less oxygen gas (and therefore less dilution steam) than a single reactor system because oxygen gas is injected between the ODH reactors in series in the multiple reactor system. This may be an advantage of the multiple reactor system compared to a single reactor system.

[0154] The first ODH reactor 1012, the second ODH reactor 1004, and the third ODH reactor 1002 are each multi-tubular fixed-bed reactors with two cooling sections on the reactor shell side that use a coolant such as molten salt to cool the tube-side reaction mixture and ODH catalyst. Each of the six cooling sections may provide or promote a respective isotherm temperature (constant temperature) of the tube-side reaction mixture and ODH catalyst. For example, this tube-side temperature may be maintained within a range of 300°C to 450°C in the first cooling section of each reactor and within a range of 350°C to 500°C in the second cooling section of each reactor. The two cooling sections in each ODH reactor are separated by respective barriers on the shell side (sealing the shell side between the cooling sections). The reaction mixture flows through the tubes (tube side) across each barrier. The barriers are not inside the tubes. The tubes (tube side) in the six cooling sections have ODH catalyst.

[0155] The feed 1014 (first reactor feed) introduced into the first ODH reactor 1012 provides an initial reaction mixture that flows through the tube side. The reaction mixture (tube side) flows through a first cooling section of the first ODH reactor 1012 and a second cooling section of the first ODH reactor 1012 disposed operationally upstream and downstream of the first cooling section of the first ODH reactor 1012. The reaction mixture exits the first ODH reactor 1012 from the tube side as an effluent 1010 of the first ODH reactor 1012. This effluent 1010 may include ethylene, acetic acid (vapor), CO, CO2, water (vapor), unreacted ethane, and residual oxygen. The effluent 1010 may exit the first ODH reactor 1012 through an effluent discharge conduit. This effluent discharge conduit may carry the effluent 1010 to the feed inlet of the second ODH reactor 1004. Thus, the effluent discharge conduit from the first ODH reactor 1012 may function as a feed conduit to the second ODH reactor 1004.

[0156] Liquid water may be added (injected) to the effluent 1010 as a water quench of the effluent 1010 to cool the effluent 1010. In particular, the vaporization of the added liquid water in the effluent 1010 consumes heat in the effluent 1010 to cool the effluent 1010. In other words, the sensible heat of the effluent 1010 may provide the latent heat of vaporization to vaporize the injected liquid water, thereby cooling the effluent 1010. This water quench via the injected liquid water may cool the effluent 1010 to a temperature, for example, in the range of 150°C to 350°C (or in the range of 200°C to 300°C). Furthermore, oxygen gas may be added (injected) to the effluent 1010. The oxygen added to the effluent 1010 provides oxygen for the ODH reaction (via the ODH catalyst) in the tubes of the second ODH reactor 1004.

[0157] Thus, the feed provided to the second ODH reactor 1004 includes the first reactor effluent 1010, vaporized added liquid water, and added oxygen gas. The effluent discharge conduit from the first ODH reactor 1004 may be a second reactor feed conduit that connects to the feed inlet (e.g., vessel inlet nozzle) of the second ODH reactor 1004 or may connect to a second reactor feed conduit. This feed (second reactor feed) introduced to the second ODH reactor 1004 provides an initial reaction mixture of the second ODH reactor 1004 that flows through the tube side. The reaction mixture (tube side) flows through a first cooling section of the second ODH reactor 1004 and a second cooling section of the second ODH reactor 1004. The second cooling section of the second ODH reactor 1004 is located operationally upstream and downstream of the first cooling section of the second ODH reactor 1004. In the context of an ODH reactor system, the first cooling section of the second ODH reactor 1004 can be referred to as the third cooling section, and the second cooling section of the second ODH reactor 1004 can be referred to as the fourth cooling section of the six cooling sections of the three ODH reactors.

[0158] The reaction mixture is discharged from the second ODH reactor 1004 from the tube side as effluent 1008 to feed the third ODH reactor 1002. The effluent 1008 may include ethylene, acetic acid (vapor), CO, CO2, water (vapor or steam), and unreacted ethane. The effluent 1008 may be discharged from the second ODH reactor 1004 through an effluent discharge conduit. The effluent discharge conduit may be coupled to an effluent outlet nozzle of the second ODH reactor 1004 to receive the effluent 1008. This effluent discharge conduit may convey the effluent 1008 to a feed inlet of the third ODH reactor 1002. Thus, the effluent discharge conduit from the second ODH reactor 1004 may function as a feed conduit to the third ODH reactor 1002.

[0159] Liquid water and oxygen may be injected between the second reactor 1004 and the third reactor 1002, as well as between the first reactor 1012 and the second reactor 1004. Liquid water may be added (injected) to the second reactor effluent 1008 as a water quench of the effluent 1008 via vaporization of the injected water to cool the effluent 1008. This water quench via the injected liquid water may cool the effluent 1008, for example, to a temperature in the range of 150°C to 350°C (or in the range of 200°C to 300°C). Additionally, oxygen gas may be added (injected) to the second reactor effluent 1008. The oxygen added to the effluent 1008 provides oxygen for the ODH reaction (via the ODH catalyst) in the tubes of the third ODH reactor 1002.

[0160] Thus, the feed provided to the third ODH reactor 1002 includes the second reactor effluent 1008, vaporized added liquid water, and added oxygen gas. The effluent discharge conduit from the second ODH reactor 1004 may be a third reactor feed conduit that connects to the feed inlet (e.g., vessel inlet nozzle) of the third ODH reactor 1002, or may be connected to a third reactor feed conduit. This feed (third reactor feed) introduced to the third ODH reactor 1002 provides an initial reaction mixture for the third ODH reactor 1002 that flows through the tube side. The reaction mixture (tube side) flows through a first cooling section of the third ODH reactor 1002 and a second cooling section of the third ODH reactor 1002.

[0161] The second cooling section of the third ODH reactor 1002 is disposed operationally upstream and downstream of the first cooling section of the third ODH reactor 1002. In the context of the ODH reactor system, the first cooling section of the third ODH reactor 1002 can be referred to as the fifth cooling section, and the second cooling section of the third ODH reactor 1002 can be referred to as the sixth cooling section of the six cooling sections of the three ODH reactors.

[0162] The reaction mixture is discharged from the third ODH reactor 1002 from the tube side as effluent 1006 (third reactor effluent). The effluent 1006 may be a product effluent similar to the effluent 108 of FIG. 1. The effluent 1006 may include ethylene, acetic acid (vapor), CO, CO2, water (vapor or steam), and unreacted ethane. The effluent 1006 may be discharged from the third ODH reactor 1002 through an effluent discharge conduit. The effluent discharge conduit may be coupled to an effluent outlet nozzle of the third ODH reactor 1002 to receive the effluent 1006. An effluent heat exchanger 1016 may be disposed along the effluent discharge conduit carrying the effluent 1006. The effluent heat exchanger 1016 may cool the effluent 1006 using water (e.g., BFW) from a steam drum as a cooling medium. The effluent heat exchanger 1016 may use the effluent 1006 as a heat medium to vaporize water and generate steam that is sent to a steam drum.

[0163] In an implementation of the ODH reactor system 1000, the steam generated in the six coolant heat exchangers and the effluent heat exchanger 1016 may be HP / VHP steam. Thus, the steam drum vessel may operate at HP / VHP (e.g., pressures in the range of 500 psig to 1700 psig). Thus, the steam discharged from the steam drum for distribution may be HP / VHP steam, which is generally saturated steam. Thus, the steam discharged from the steam drum may be at a temperature (saturation temperature) in the range of, for example, 240° C. to 330° C.

[0164] The ODH reactor system 1000 may heat steam discharged from a steam drum to a temperature above the saturation temperature to obtain the steam as superheated steam for distribution (HP / VHP). In particular, six superheater heat exchangers may receive steam from a steam drum (e.g., in parallel) and heat the steam (using reactor shell-side coolant as a heat carrier) to superheat the steam. As shown, each of the six superheater heat exchangers may be associated with a respective cooling section. Each of these six superheater heat exchangers may be configured as described with respect to the corresponding superheater heat exchanger in Figures 3-9. The number of superheater heat exchangers may be less than six, such as in the range of one to six, may be in parallel as shown, or may be in series with respect to the steam flow being superheated. Such alternative configurations for the superheater exchangers in the ODH reactor system may be applicable to the ODH reactor systems shown herein having two or more superheaters.

[0165] FIG. 11 is an ODH reactor system 1100 that is the same or similar to the ODH reactor system 1000 of FIG. 10, except that instead of a water quench between the ODH reactors, a coolant (e.g., molten salt) quench is performed in each of the first and second ODH reactors. In particular, the first and second ODH reactors each have a third cooling section that does not have a catalyst. For example, see FIG. 5 and FIG. 8 for a description of a third cooling section that does not have a catalyst. The third cooling section (non-catalyst cooling) section in each of the first and second ODH reactors removes heat from the reaction mixture on the tube side via a circulating coolant on the shell side. The third cooling section may cool the reaction mixture to a temperature, for example, in the range of 150° C. to 300° C. (or in the range of 200° C. to 300° C.). In the case of a coolant as a molten salt, the third cooling section can be characterized as performing a salt quench. An advantage of the third cooling section may be that heat removed from the reaction mixture can be recovered to heat water (e.g., preheat BFW) via a coolant heat exchanger for steam generation. In contrast, in the case of a water quench as in Figures 7 and 10, the removed heat may be lost to the vaporization of water.

[0166] For an explanation of generally similar or identical equipment and operations regarding ODH reactor system 1100, see Figures 3-10. ODH reactor system 1100 may be ODH reactor system 102 of Figure 1. For comparison of the examples of ODH reactor systems disclosed herein, the implementation of ODH reactor system 1100 provides the basis for configuration 12.

[0167] The third cooling section (non-catalytic cooling section) of the first ODH reactor is operationally downstream of the second cooling section of the first ODH reactor. The seventh coolant supply system circulates the seventh coolant (via a coolant circulation pump) through the shell side in the third cooling section of the first ODH reactor. The seventh coolant heat exchanger (with water as the cooling medium) removes heat from the circulating seventh coolant, thus heating (e.g., preheating) the water (e.g., BFW) for vaporization into steam (e.g., HP / VHP) in the steam drum. The seventh coolant heat exchanger may be configured to vaporize water, partially vaporize water, or heat water without vaporization in the heat exchanger. The illustrated embodiment is heating (preheating) water without significant vaporization in the heat exchanger. The seventh coolant heat exchanger receives water from a pump, such as a BFW pump.

[0168] The third cooling section (non-catalytic cooling section) of the second ODH reactor is operationally downstream of the second cooling section of the second ODH reactor. The eighth coolant supply system circulates the eighth coolant (via a coolant circulation pump) through the shell side in the third cooling section of the second ODH reactor. The eighth coolant heat exchanger (with water as the cooling medium) removes heat from the circulating eighth coolant and thus heats the water (e.g., BFW) for vaporization into steam (e.g., HP / VHP) in the steam drum. The eighth coolant heat exchanger may be configured to vaporize water, partially vaporize water, or heat water without vaporization in the heat exchanger. The illustrated embodiment is heating (pre-heating) of water without significant vaporization in the heat exchanger. The eighth coolant heat exchanger receives water from a pump, such as a BFW pump.

[0169] The seventh and eighth coolants may each be, for example, a molten salt. In the context of the ODH reactor system 1100, the third cooling section of the first ODH reactor may be referred to as the seventh cooling section, and the third cooling section of the second ODH reactor may be referred to as the eighth cooling section of the eight cooling sections of the three ODH reactors.

[0170] Again, the water level may be maintained within the steam drum. Steam may be discharged from the steam drum for distribution to users. After being discharged from the steam drum, the steam may be superheated in a superheater heat exchanger (described above) before being distributed to users.

[0171] The first ODH reactor receives a feed, which may be the same as or similar to the feed 1014 of FIG. 10. The feed enters the tube side of the first ODH reactor, providing a flowing reaction mixture in the tubes. The reaction mixture flows through the first, second, and third cooling sections of the first ODH reactor. The reaction mixture exits the first ODH reactor from the tube side as an effluent (first reactor effluent) (similar to effluent 808 of FIG. 8) for feeding the tube side of the second ODH reactor. The effluent may be of similar or the same composition as the effluent 1008 of FIG. 10, but is typically at a lower temperature than the discharged effluent 1008 due to the presence of the third cooling section of the first ODH reactor of FIG. 11. These two quench cooling sections may be characterized as alternatives to a water quench for cooling the reactor effluents of the first ODH reactor and the second ODH reactor prior to adding O2.

[0172] In FIG. 11, oxygen gas may be injected into the first reactor effluent as in FIG. 10. However, injecting liquid water for water quenching into the first reactor effluent as in FIG. 10 may be avoided because the third cooling section of the first ODH reactor cools the reaction mixture that is discharged as the first reactor effluent. In general, in the case of O2 injection, water injection may be performed if the interstage effluent temperature is relatively high. The three cooling techniques (water quench between two reactors, salt quench, and HEX) that give a cooled interstage effluent before O2 addition can be used alone or in combination.

[0173] The first reactor effluent and the injected oxygen enter the second ODH reactor as a feed to give a reaction mixture that flows through the tube side. The reaction mixture flows through the three cooling sections of the second ODH reactor into the tubes and is discharged from the second ODH reactor as an effluent (second reactor effluent). Oxygen gas may be injected into the second reactor effluent. The second reactor effluent and the injected oxygen enter the third ODH reactor as a feed to give a reaction mixture that flows through the tube side of the two cooling sections of the third ODH reactor. The reaction mixture may be discharged from the tube side of the third ODH reactor as an effluent (third reactor effluent), which may be similar to the effluent 108 of FIG. 1. The effluent may be cooled in an effluent heat exchanger with water as the cooling medium, the water is vaporized with heat from the effluent into steam, and the steam is sent to a steam drum. In the ODH reactor system 1100, six superheater heat exchangers (as shown) superheat the steam discharged from the steam drum for distribution to users.

[0174] Figure 12 is an ODH reactor system 1200 that is the same or similar to the ODH reactor system 1000 of Figure 10, except that effluent heat exchangers 1202, 1204 (instead of an injected water quench) cool the effluent discharged from the first ODH reactor and the second ODH reactor, respectively. An advantage of the effluent heat exchangers 1202, 1204 may be that heat removed from the effluent can be recovered to preheat water (e.g., BFW) for steam generation. Conversely, in the case of an injected water quench, the removed heat may be lost to vaporization of the injected water in the effluent.

[0175] For an explanation of generally similar or identical equipment and operations regarding ODH reactor system 1200, see Figures 3-11. ODH reactor system 1200 may be ODH reactor system 102 of Figure 1. For comparison of the examples of ODH reactor systems disclosed herein, the implementation of ODH reactor system 1200 provides the basis for configuration 13.

[0176] Each of the effluent heat exchangers 1202, 1204 (e.g., shell-and-tube heat exchangers) may cool the respective effluent with water (e.g., BFW) to a specified temperature, e.g., in the range of 150°C to 350°C (or in the range of 200°C to 300°C). The effluent heat exchangers 1202, 1204 may receive water (e.g., from a BFW pump) and heat the water (in cooling the effluent) that preheats the water for vaporizing the water in the steam drum. Water may be provided to the heat exchangers 1202, 1204 generally at the operating pressure (e.g., HP / VHP) of the steam drum. Water may flow from a pump (e.g., a BFW pump) through the heat exchangers 1202, 1204 to the steam drum.

[0177] In FIG. 12, each of the six coolant heat exchangers in the coolant supply system, as well as the third reactor effluent heat exchanger, may vaporize water (e.g., BFW) (as a cooling medium) from the steam drum to obtain steam that is sent to the steam drum, as described with respect to FIG. 10. Also as described, the water level may be maintained in the steam drum. Steam may be discharged from the steam drum for distribution to users. The steam after being discharged from the steam drum may be superheated in a superheater heat exchanger (as shown) before being distributed to users, as described with respect to the previous figures.

[0178] As discussed, for the process feed (e.g., 104 in FIG. 1 ) to an ODH reactor system (e.g., 102 in FIG. 1 ), dilution steam may be included with the ethane and oxygen gas to keep the feed mixture outside flammability limits.

[0179] FIG. 13 is an example of a flammability diagram 1300 for a mixture of ethane, oxygen, and steam at 300° C. and 500 kilopascals (kPa) absolute pressure. The flammability diagram 1300 is a ternary plot with an ethane axis and associated horizontal grid lines 1302 for the molar concentration of ethane in the mixture in mole percent (mol%), an oxygen axis with associated diagonal grid lines 1304 for the molar concentration of oxygen gas in the mixture in mol%, and a steam axis with associated diagonal grid lines 1306 for the molar concentration of oxygen gas in the mixture in mol%. The area (region) between the upper flammability limit (UFL) 1308 and the lower flammability limit (LFL) 1310 is the flammable zone, meaning that the mixture at the composition of that area is flammable. Areas of the plot outside the flammability limits are not flammable and may be the desired operating zone (outside the flammable zone). Line 1312 represents an oxygen to ethane molar ratio of 3.5 for all ethane combustion.

[0180] As a contingency in the operation of the ODH reactor system, the maximum concentration of oxygen in the feed can be specified with a margin 1314 (e.g., 1-5 mol%) below the oxygen concentration at UFL 1308. As shown, margin 1314 is a line parallel to the line for UFL 1308. Margin 1314 is the amount of oxygen mol% outside the flammable zone, specifically the margin outside the upper flammable limit (UFL 1308). The oxygen concentration can be reduced from the oxygen concentration at UFL 1308 to margin 1314 by increasing the concentration of dilution steam. Table 1 shows an exemplary target concentration of oxygen in the feed based on FIG. 13 (flammability diagram at 300° C. and 500 kPa). Margins 1314 that are considered to be aggregated are no margin, 1 mol% less, 2 mol% less, 3 mol% less, 4 mol% less, and 5 mol% less. [Table 1]

[0181] FIG. 14 is a method 1400 of operating an ODH reactor system having an ODH reactor. The ODH reactor is a multi-tube reactor having a tube side and a shell side. The tube side may include tubes for flow of the reaction mixture. The shell side may include a volume within the reactor around (external to) the tubes for flow of a coolant around the tubes. The ODH reactor comprises a first cooling section and a second cooling section that may be separated by a barrier on the shell side. The second cooling section may be operationally upstream and downstream of the first cooling section with respect to the direction of flow of the reaction mixture flowing through the tube side. The ODH reactor may have a shell-side flow barrier separating the first and second cooling sections such that the first and second coolants are not combined on the shell side.

[0182] At block 1402, the method includes providing a feed including ethane, oxygen, and a diluent (e.g., water as steam) to obtain a reaction mixture flowing through a tube side of an ODH reactor. The diluent may be water, CO2, N2, argon, helium, or methane, or any combination thereof. The presence of a diluent, including these aforementioned diluents, may maintain the feed outside flammability limits. For example, the feed may include water (dilution steam) as a diluent, thereby maintaining the feed outside flammability limits. Providing a feed to the tube side may be providing the feed to an inlet of a tube (of a tube bundle) of the ODH reactor. The tube may have an ODH catalyst disposed therein.

[0183] At block 1404, the method includes dehydrogenating ethane to ethylene in the reaction mixture (via an ODH catalyst) on the tube side. The ODH reaction may include dehydrogenating ethane to ethylene in the tube via an ODH catalyst in the presence of oxygen in the reaction mixture. The reaction of ethane with oxygen in the reaction mixture may include a first total reaction, which is the dehydrogenation of ethane to ethylene, a second total reaction to give acetic acid (and water), a third total reaction to give carbon monoxide (and water), and a fourth total reaction to give carbon dioxide (and water). Each of these four total reactions may be a representation that incorporates intermediate reactions. These four reactions are simplified representations of total reactions that may be characterized as yield-type reactions (total reactions) each having an associated reaction chain. The method may include specifying an increase in ethylene selectivity by promoting the first total reaction over the third and fourth total reactions, the first total reaction consuming a lesser stoichiometric amount of oxygen than each of the third and fourth total reactions.

[0184] At block 1406, the method includes flowing a first coolant through a shell side in the first cooling section, thereby maintaining the reaction mixture (and / or ODH catalyst) in the first cooling section at a first temperature, such as within a range of 300° C. to 450° C., 350° C. to 450° C., 300° C. to 400° C., or 300° C. to 375° C. The first coolant may be, for example, a molten salt. As will be appreciated by those skilled in the art, a molten salt may be a salt that is solid at standard temperature and pressure, but enters a liquid phase due to elevated temperature. The molten salt may be a class of ionic liquids that are solid at ambient temperature. Molten salts (e.g., fluoride salts, chloride salts, nitrates, etc.) may be heat transfer fluids used as coolants for the ODH reactor.

[0185] At block 1406, the method includes flowing a second coolant (e.g., molten salt) through a shell side in the second cooling section, thereby maintaining the reaction mixture (and / or the ODH catalyst) in the second cooling section at a second temperature, the first temperature being lower than the second temperature. The second temperature may be, for example, in the range of 350° C. to 500° C., or in the range of 375° C. to 450° C. The ODH reactor can have a third cooling section (e.g., FIG. 6), up to “n” cooling sections.

[0186] The method includes cooling the reaction mixture (and / or the ODH catalyst) to a first temperature in a first cooling section via a first coolant flowing through a shell side in the first cooling section, and to a second temperature in a second cooling section via a second coolant flowing through a shell side in the second cooling section. The shell side is for the first coolant and the second coolant to flow around the tubes. The second coolant and the first coolant may both be molten salts and may have the same composition.

[0187] The method may include specifying that the first temperature is lower than the second temperature to promote dehydrogenation of ethane to ethylene over reactions in the reaction mixture that give carbon dioxide and over reactions in the reaction mixture that give carbon monoxide, thereby increasing ethylene selectivity. Maintaining the first temperature lower than the second temperature may be responsive to specifying an increase in ethylene selectivity, thereby decreasing the amount of oxygen in the feed and decreasing the amount of water in the feed. Additionally, an ODH reactor of the present invention having three or more cooling sections may provide more advantages for the performance of the reaction and better selectivity to ethylene.

[0188] In a given cooling section, the temperatures of the reaction mixture and the ODH catalyst may be substantially the same. The temperature difference between the reaction mixture and the ODH catalyst may be, for example, less than 1° C. or less than 2° C. The shell-side coolant flow cools both the reaction mixture and the ODH catalyst. At steady state, the coolant temperature may be similar to the temperatures of the reaction mixture and the ODH catalyst.

[0189] At block 1408, the method includes maintaining a temperature rise of the first coolant through the first cooling section below a first threshold. The first threshold may be, for example, within a range of 2° C. to 8° C. The method includes maintaining a temperature rise of the second coolant through the second cooling section below a second threshold. The second threshold may be, for example, within a range of 2° C. to 8° C. These specified thresholds may determine the amount of molten salt circulation.

[0190] The method may include specifying maintaining a temperature rise of the first coolant below a first threshold and maintaining a temperature rise of the second coolant below a second threshold to promote dehydrogenation of ethane to ethylene over reactions resulting in carbon dioxide reactions and reactions resulting in carbon monoxide, thereby increasing ethylene selectivity. The maintaining of the temperature rise of the first coolant below the first threshold and maintaining of the temperature rise of the second coolant below the second threshold may be responsive to specifying an increase in ethylene selectivity, thereby increasing the ethylene selectivity, thereby decreasing the amount of oxygen in the feed and decreasing the amount of water in the feed.

[0191] At block 1410, the method may include discharging an effluent from the ODH reactor, the effluent comprising ethylene, acetic acid, water, carbon dioxide, and carbon monoxide. In particular, the method may include discharging the reaction mixture as an effluent from the ODH reactor.

[0192] At block 1412, the method may include heating water (e.g., BFW) with at least one of a first coolant discharged from the ODH reactor, a second coolant discharged from the ODH reactor, or an effluent discharged from the ODH reactor. In implementations, heating the water with at least one of the first coolant, the second coolant, or the effluent vaporizes the water, thereby producing steam from the water.

[0193] At block 1414, the method may include flowing the generated steam to a steam drum and from the steam drum through a superheater heat exchanger (e.g., one per cooling section of the ODH reactor). There may be one superheater heat exchanger per cooling section. There may be two or more superheaters per cooling section in series and / or parallel. The superheater heat exchanger may be a heat exchanger (e.g., a shell-and-tube heat exchanger) located adjacent (but not attached to) the ODH reactor. Coolant from the ODH reactor shell may be routed as a heat medium through the superheater heat exchanger. Alternatively, the superheater heat exchanger may be an auxiliary tube bundle in the reactor shell or an additional tube bundle attached to the ODH reactor (with a dedicated shell), which shares the coolant with the ODH reactor shell.

[0194] At block 1416, the method may include flowing a third coolant through a shell side in a third cooling section of the ODH reactor, thereby maintaining the reaction mixture on the tube side in the third cooling section at a third temperature, the third temperature being lower than the second temperature. The third cooling section (if used) is operationally downstream of the second cooling section in the flow direction of the reaction mixture and is separated from the second cooling section by a second flow barrier on the shell side. In implementations, the third cooling section may be a catalyst cooling section or a non-catalytic cooling section. In the case of a catalyst cooling section, the temperature of the coolant may be the highest (maximum) of the three cooling sections. In the case of a non-catalytic cooling section, e.g., a coolant (salt) quench section, the temperature of the reaction mixture and the coolant may be the lowest (minimum) of the three cooling sections. A non-catalytic cooling section (without catalyst, but possibly with inert particles in the tubes) as the third cooling section (if used) may be utilized to cool the reaction mixture for discharge as the reactor effluent, instead of utilizing a TLE to cool the effluent.

[0195] Per blocks 1412 and 1416, the method may include heating the water (e.g., BFW) with at least one of a first coolant discharged from the ODH reactor, a second coolant discharged from the ODH reactor, a third coolant discharged from the ODH reactor, or an effluent discharged from the ODH reactor. In some implementations, the tube side in the third cooling section does not include a catalyst and the water (e.g., BFW) is not heated with the effluent. In other implementations, the tube side in the third cooling section does not include a catalyst and the water (e.g., BFW) is heated with the effluent.

[0196] The method may include configuring the ODH reactor to specify an increase in ethylene selectivity, thereby increasing the ethylene selectivity, by reducing the tube to a specified diameter (e.g., nominal, outer, or inner diameter) or less. The specified diameter may be, for example, a diameter (e.g., nominal, outer, or inner diameter) of 1.5 inches or 1.25 inches or less, a linear velocity of the reaction mixture in the tube is within a range of 150 centimeters per second (cm / s) to 500 cm / s, and a gas hourly space velocity of the reaction mixture through the ODH catalyst in the tube is within a range of 1,500 hours. -1 (hr -1 )~10,000hr -1 is within the range.

[0197] 15 is a method 1500 of operating an ODH reactor system having a first ODH reactor and a second ODH reactor operatively arranged in series, each being a multi-tubular fixed-bed reactor having a shell side and a tube side. The first ODH reactor and the second ODH reactor each have a first cooling section and a second cooling section. The first ODH reactor and the second ODH reactor each may have a flow barrier on the shell side separating the first and second cooling sections. For the first ODH reactor and the second ODH reactor, the second cooling section may be operationally upstream and downstream of the first cooling section in the direction of flow of the reaction mixture flowing through the tube side and is separated from the first cooling section by a flow barrier on the shell side.

[0198] At block 1502, the method includes providing a feed including ethane, oxygen (oxygen gas), and a diluent (e.g., steam) to a first ODH reactor, which can result in a reaction mixture flowing through a tube side of the first ODH reactor.

[0199] At block 1504, the method includes dehydrogenating ethane to ethylene over an ODH catalyst in a reaction mixture flowing through the tube sides of each of the first ODH reactor and the second ODH reactor. As described, further reactions may occur in the reaction mixture.

[0200] At block 1506, the method includes flowing a coolant (e.g., molten salt) through a shell side in the first and second cooling sections of the first and second ODH reactors, respectively, to cool the ODH catalyst on the tube side. This can cool the reaction mixture and the ODH catalyst on the tube side of the first and second ODH reactors, respectively. The shell side can be for flowing the coolant to cool the ODH catalyst on the tube side. Cooling the ODH catalyst may include (1) maintaining the ODH catalyst (and / or reaction mixture) on the tube side in the first cooling section of the first ODH reactor at a temperature lower than the temperature of the ODH catalyst (and / or reaction mixture) on the tube side in the second cooling section of the first ODH reactor, and (2) maintaining the ODH catalyst (and / or reaction mixture) on the tube side in the first cooling section of the second ODH reactor at a temperature lower than the temperature of the ODH catalyst (and / or reaction mixture) on the tube side in the second cooling section of the second ODH reactor. The temperature of the ODH catalyst and reaction mixture in the first cooling section of each of the first ODH reactor and the second ODH reactor may be, for example, in the range of 300°C to 450°C. The temperature of the ODH catalyst and reaction mixture in the second cooling section of each of the first ODH reactor and the second ODH reactor may be, for example, in the range of 350°C to 500°C. In a given cooling section, the temperature of the reaction mixture and the ODH catalyst may be substantially the same. The temperature difference between the reaction mixture and the ODH catalyst may be, for example, less than 1° C. or less than 2° C. At steady state, the temperature of the coolant may be similar to the temperature of the reaction mixture and the ODH catalyst.

[0201] At block 1508, the method includes maintaining a temperature rise of the coolant through each of the first and second cooling sections of the first and second ODH reactors, respectively, below a threshold value. The threshold value may be, for example, within a range of 2° C. to 8° C.

[0202] At block 1510, the method includes heating water (e.g., BFW) with coolant discharged from at least one of the first cooling section of the first ODH reactor, the second cooling section of the first ODH reactor, the first cooling section of the second ODH reactor, or the second cooling section of the second ODH reactor, where heating the water vaporizes the water into steam or preheats the water for vaporizing (evaporating) the water into steam in a steam drum.

[0203] At block 1512, the method includes discharging a first effluent from the first ODH reactor to a second ODH reactor. In particular, the method may include discharging the first effluent from the first ODH reactor to a tube side of the second ODH reactor as a feed. The first effluent includes ethylene, acetic acid, water, carbon dioxide, carbon monoxide, and unreacted ethane.

[0204] At block 1514, the method includes cooling the first effluent. For example, the method may include injecting liquid water into the first effluent, thereby vaporizing the liquid water via heat from the first effluent to cool the first effluent. Instead of (or in addition to) liquid water injection, the method may include cooling the first effluent by a heat exchanger (e.g., operatively disposed between the first reactor and the second reactor) using boiler feedwater as a cooling medium, thereby vaporizing the boiler feedwater into steam, or heating the boiler feedwater to vaporize the boiler feedwater into steam in a steam drum.

[0205] Instead of (or in addition to) liquid water injection and / or a heat exchanger to cool the first effluent, the method may include indirect or upstream cooling of the first effluent. In other words, the first ODH reactor may have a third cooling section (e.g., without ODH catalyst in the tubes) to cool the reaction mixture in the tubes before discharging the reaction mixture as the first effluent. Thus, to cool the first effluent, the method may include flowing a coolant through a shell side in the third cooling section of the first ODH reactor, thereby cooling the reaction mixture on the tube side in the third cooling section, the third cooling section being operationally downstream of the second cooling section of the first ODH reactor in the flow direction of the reaction mixture and separated from the second cooling section by a second flow barrier on the shell side. In some implementations, the tube side in the third cooling section (if used) of the first ODH reactor (through which the reaction mixture flows) does not contain a catalyst. In some implementations, the tubes in the third cooling section may have non-catalytic particles with relatively high thermal conductivity to facilitate or increase heat removal.

[0206] At block 1516, the method includes injecting oxygen into the first effluent. In particular, the method may include injecting oxygen gas into the first effluent between the first ODH reactor and the second ODH reactor.

[0207] The method includes discharging a second effluent from the second ODH reactor, the second effluent comprising ethylene, acetic acid, water, carbon dioxide, and carbon monoxide.

[0208] Consistent with block 1510, the method may include generating steam via heat from at least one of the coolant discharged from the first ODH reactor, the coolant discharged from the second ODH reactor, the first effluent discharged from the first ODH reactor, or the second effluent discharged from the second ODH reactor. The method may include flowing the steam through another tube bundle (not having an ODH catalyst) associated with the first ODH reactor or the second ODH reactor, or both, to heat the steam with the coolant flowing on the shell side, thereby superheating the steam. The tubes may be in a separate shell-and-tube heat exchanger adjacent to the ODH reactor and receiving / returning the coolant (as a heat carrier) from / to the ODH reactor shell. Alternatively, the tubes may be an auxiliary (additional) tube bundle within the ODH reactor shell or in a dedicated shell (adjacent or attached to the ODH reactor) that receives (and returns) the slipstream of coolant (molten salt) from the ODH reactor shell. Steam (e.g., at about saturation) may flow through these additional tubes from a steam drum. Superheating the steam may be to raise the temperature of the steam above the saturation temperature of the steam.

[0209] In order to reduce DS consumption, oxygen consumption needs to be reduced. Considering the above four reactions, the minimum oxygen demand is for ethylene production (0.5 moles O2 per mole ethane) and the maximum oxygen demand is for CO2 production (3.5 moles O2 per mole ethane). Therefore, in order to reduce O2 consumption, the selectivity towards ethylene needs to be increased. Furthermore, an increase in the selectivity of acetic acid is more desirable than the formation of CO or CO2.

[0210] ODH reactor design (and operation) can be configured to achieve higher ethylene selectivity (and higher acetic acid selectivity). The ODH reactor design specified is a multi-tube fixed-bed reactor in which the tubes are packed with catalyst. During operation, process gas passes through these tubes and a coolant flows on the shell side to remove the heat of reaction. Molten salt is specified as the coolant in the following examples due to the operating temperatures, which are generally in the range of 300°C to 500°C. Molten salt can generally impart higher stability at high temperatures and better heat transfer coefficients compared to other heat transfer fluids.

[0211] Configurations 1-13 are presented as implementations and are not intended to limit the present technology. Alternatives or other variations are applicable as shown in the overall disclosure of this specification. Specific exemplary data applies to configurations 1-13 in the following examples. Other exemplary data is applicable to configurations 1-13. In the description of configurations 1-13 of the ODH reactor system, the reactors may be referred to as stages. In particular, a single reactor system may be referred to as a single-stage reactor system or a one-stage reactor system, and a multi-reactor system may be referred to as a multi-stage reactor system (e.g., a two-stage reactor system, a three-stage reactor system, etc.). For example, a two-stage reactor system is an ODH reactor system having two ODH reactors in operative series. A three-stage reactor system in an ODH reactor system having three ODH reactors in operative series. The phrase "between stages" or the word "interstage" means between the ODH reactors. Between the first stage and the second stage means between the first ODH reactor and the second ODH reactor. Between the second and third stages means between the second and third ODH reactors. An effluent heat exchanger that cools the effluent discharged from a reactor in a single reactor system or from the terminal (final) reactor in a multiple reactor system may be referred to as a transfer line exchanger (TLE). Interstage cooling of the effluent may be provided by (1) a water quench via liquid water injection, (2) a heat exchanger with water as the coolant (this option is represented by the acronym HEX), or (3) a salt quench of the reaction mixture in an end-of-reactor cooling section (with molten salt as the coolant) prior to the discharge of the interstage effluent from the reactor. A HEX of the final effluent (not interstage) may be referred to as a TLE. The cooling section in an ODH reactor may be referred to as a catalyst cooling section for cooling the section where the tubes have catalyst (ODH catalyst). A catalyst cooling section may be utilized to cool both the reaction mixture and the ODH catalyst on the tube side. For cooling sections in which the tubes do not have a catalyst (ODH catalyst) (but may have inert particles disposed within the tubes), the cooling section may be characterized as a non-catalytic cooling section that cools the tube-side reaction mixture. The coolant as a molten salt may be referred to as salt for short.

[0212] Remarks and basis for thirteen exemplary configurations (configurations 1-13) of ODH reactor systems are presented below. The implementations of the ODH reactor systems in Figures 3-12 provide the basis for configurations 1-13: configuration 1 (Figure 3), configurations 2, 3, 4, and 5 (Figure 4), configuration 6 (Figure 5), configuration 7 (Figure 6), configuration 8 (Figure 7), configuration 9 (Figure 8), configuration 10 (Figure 9), configuration 11 (Figure 10), configuration 12 (Figure 11), and configuration 13 (Figure 12). However, each figure is not limited by the specific implementation in the presented configuration. The figures provide a general basis for the number of reactors, the number of cooling sections, and the heating of the water. In contrast, the specific implementations, for example, regarding the tube size (diameter), the coolant as molten salt, the value of the temperature or temperature rise, etc., for the configurations are not limiting the figures. An initial remark as an overview regarding configurations 1-13 is presented immediately below.

[0213] Configuration 1 is a single reactor (1 stage) with one catalyst cooling section (1 section), 1 inch tubing, and less than 5°C temperature rise on the coolant side. The coolant is utilized to generate HP / VHP steam and superheat the generated HP / VHP steam (500 psig to 1700 psig). The reactor effluent can be cooled in the post-reactor TLE against BFW (to preheat or vaporize BFW for HP / VHP steam generation).

[0214] Configurations 1, 2, and 7 are single stage with 1, 2, or 3 catalyst cooling sections, respectively. The number of catalyst cooling sections can be expanded to n sections, which may improve the performance of the reaction.

[0215] Configurations 2 and 3 are single stage with two catalyst cooling sections. The temperature rise of the coolant side in the two catalyst cooling sections is less than 5°C and about 15°C, respectively. Other values ​​for the coolant temperature rise can be implemented. A temperature rise of 2-8°C (e.g., 5°C) may be preferred over higher values ​​such as more than 8°C (e.g., 15°C) in terms of reaction performance related to the coolant flow rate. A higher delta T may mean less coolant (e.g., molten salt) circulation resulting in a lower Reynolds number (Re) and therefore a lower heat transfer coefficient (HTC). The key parameter for improving the performance of the ODH reactor (higher ethylene selectivity and lower CO / CO2 selectivity) is the heat removal capacity.

[0216] Configurations 2, 4, and 5 are one stage with two catalyst cooling sections. Configurations 2, 4, and 5 have tube diameters of 1 inch, 1.25 inch, and 1.5 inch, respectively. Other tube sizes can be implemented. In general, smaller tubes have a higher Re inside the tube and therefore may have better (increased) heat removal capability due to higher HTC, which may result in better reactor performance.

[0217] Configuration 2 is a single stage with two catalyst cooling sections and a TLE after the reactor to produce HP / VHP steam. Configuration 6 is a single stage with two catalyst cooling sections and a third cooling section (non-catalytic cooling section with inert particles in the tubes) as a low temperature cooling section to cool (lower) the tube side reaction mixture (gas) and where the coolant (molten salt) preheats and vaporizes the BFW to produce HP / VHP steam. The difference between configuration 2 (with TLE) and configuration 6 (coolant quench section) is the TLE versus the coolant (e.g., molten salt) quench.

[0218] Configuration 8 is a two-stage reactor system with two catalyst cooling sections at each stage and oxygen gas (O2) interstage injection. Liquid water is injected between the stages to vaporize, and the latent heat of vaporization is used to reduce the reactor effluent temperature from the first stage (before O2 interstage injection) to a temperature in the range of 200°C to 300°C. This may further reduce the risk of spontaneous ignition of hydrocarbons and other flammable gases. The two-stage reactor system splits the O2 between the two stages. In this way, the first stage accepts less O2 than the one-stage reactor system and therefore requires much less dilution steam (DS) compared to the one-stage reactor system configuration.

[0219] Configuration 9 is a two-stage reactor system with two catalytic cooling sections in each stage and O2 interstage injection. Similar to the single reactor of Configuration 6, the first reactor (stage) of Configuration 9 has an inert (non-catalytic) cooling section with a coolant (low temperature molten salt as salt quench) at the end of the first reactor to cool the tube-side gas before O2 injection. The coolant (lower temperature molten salt) preheats the BFW or generates HP / VHP steam. The first reactor has three cooling sections (molten salt cooling sections), two to cool the catalytic reaction and the third to cool the tube-side gas before it exits the reactor.

[0220] Configuration 10 is a two-stage reactor system with two catalyst cooling sections in each stage and O2 interstage injection. Instead of a water quench or molten salt quench, a heat exchanger (HEX) cools the reactor effluent from the first stage and recovers heat to preheat BFW or generate HP / VHP steam. As described herein, in this quench context, the phrase salt quench refers to a molten salt quench (coolant molten salt in the shell of the ODH reactor).

[0221] Configurations 11, 12, and 13 are three-stage reactor systems with two catalyst cooling sections in each stage and with O2 interstage injection. The interstages can use water quench, salt quench, or HEX, or can be used to cool the reactor effluent before O2 injection as described above (configurations 8, 9, and 10). Combinations of these techniques may also be used. Applicability can be extended to n-stage reactors.

[0222] In specific implementations of configurations 1-7, some features of the single-stage reactor system include an O2 target of 6-10 mol% in the feed, a water / O2 molar ratio of 6-12 in the feed, a tube-side linear velocity of 150 cm / s-500 cm / s, and a gas hourly space velocity (GHSV) of 1,500-10,000 hr through the tube-side ODH catalyst. -1 Features may be temperature and pressure dependent. Features may be considered at feed conditions to the ODH reactor (e.g., 200-350°C and 300-600 kPa absolute pressure). Observations for configurations 1-7 (single-stage reactor systems) include: (a) Two or more catalyst cooling sections improve ethylene selectivity and reduce the overall feed flow to the reactor, thus allowing for smaller reactors; (b) Smaller tube diameters generally provide better ethylene selectivity, since smaller diameters improve (increase) the heat transfer coefficient (HTC) and heat removal, thus preventing or reducing the occurrence of peak temperature spikes (higher peak temperatures generally result in more undesirable reactions); (c) Larger coolant side temperature rises may negatively impact heat removal and reactor size, since there is a higher chance of less coolant (salt) circulation, which may result in smaller HTCs. (d) Having a salt quench section is more efficient than TLE in terms of overall reactor size (however, the salt quench adds complexity to the reactor design, i.e., another cooling section [molten salt section]).

[0223] In specific implementations of configurations 8-10 (two-stage reactor system), some features of the two-stage reactor system include an O2 target for the feed to the first stage reactor of 6-10 mol%, an O2 target for the feed to the second stage reactor of 6-10 mol%, a water / O2 molar ratio in the first stage reactor of 1.5-3.5, a linear velocity in the first stage reactor of 250 cm / s-600 cm / s, a linear velocity in the second stage of 100 cm / s-400 cm / s, and a GHSV of both stages combined of 2,000-6,000 hr -1 The GHSV of the first reactor is 5,000 to 30,000 hr -1 The GHSV of the second reactor is 2,000 to 10,000 hr -1 These features may be affected by the feed temperature and feed pressure, considered at 200-350°C and 300-600 kPa absolute pressure for the feed to the first stage, and 150-300°C and 300-500 kPa absolute pressure for the feed to the second stage. The tube side temperature (containing the reaction mixture and / or ODH catalyst) (generally the shell side temperature) in the first cooling section of each stage (reactor) may be, for example, in the range of 300-450°C. The tube side temperature (containing the reaction mixture and / or ODH catalyst) (generally the shell side temperature) in the second cooling section of each stage (reactor) may be, for example, in the range of 350-500°C. Observations of the two-stage reactor system are for a salt quench with interstage HEX or interstage discharge of the reaction mixture, the first reactor is larger and the second reactor is smaller than when a water quench is used interstage. In general, the second reactor is typically larger than the first reactor, including when a water quench is used. Nevertheless, in some implementations, in the case of a HEX and salt quench versus a water quench, the first reactor may be larger in the HEX and salt quench than in the water quench. In some implementations, the second reactor may be smaller in the HEX and salt quench than in the water quench.

[0224] In a specific implementation in configurations 11-13 (three-stage reactor system), the three-stage reactor system includes an O2 target of 6-10 mol% for the feed to each of the first, second, and third stage reactors. Most of the O2 per stage should be consumed. The O2 at the discharge of each stage may be, for example, less than 0.1 mol%. The water / O2 molar ratio in the first stage reactor is 0.5-2.5, and generally, there is no target for the water / O2 molar ratio in the subsequent stages, since DS is typically not added between stages. If there is a water quench interstage, the purpose is not to dilute, but rather to quench the effluent. For quenching, an appropriate amount of water may be added to reduce the temperature of the effluent, for example, to 200-300°C. Further features of these three-stage reactor systems are that the linear velocities are 250-700 cm / s in the first stage reactor, 100-450 cm / s in the second stage reactor, and 50-350 cm / s in the third stage reactor, and the combined GHSV of the three stages is 2,000-6,000 hr -1 The GHSV is 5,000 to 60,000 hr in the first reactor. -1 , 5,000~30,000hr in the second reactor -1 , 2,000~10,000hr in the third reactor -1 These characteristics may be influenced by the feed temperature and pressure, which are considered to be 200-350°C and 300-600 kPa absolute pressure for the first stage reactor, 150-300°C and 200-500 kPa absolute pressure for the second stage reactor, and 150-300°C and 200-500 kPa absolute pressure for the third stage reactor.

[0225] In a specific implementation form of configurations 8 to 13 (two-stage reactor system or three-stage reactor system), the observations of the multi-reactor system include that for salt quench or HEX between stages, a first reactor that is larger, a second reactor that is larger, and a third reactor that is smaller are used when water quench is carried out between stages. From two stages to three stages, the sizes of the reactors may vary. Generally, the size of the first reactor < the second reactor < the third reactor <... < the nth reactor. When quench water is used, the size of the last reactor is larger compared to HEX and salt quench. When quench water is used, the size of the reactor before the last reactor is generally smaller compared to the case of HEX and salt quench. Further observations about the multi-reactor system include the following. (a) Compared with a one-stage (single reactor) system, there is less O2 to the first stage and much less DS demand. (b) A first reactor that is smaller than the terminal (final) reactor (smaller than the single reactor in a one-stage system). (c) As the number of stages increases, the ethylene selectivity slightly decreases (ethylene selectivity: one stage > two stages > three stages >... > n stages). (d) As the number of stages increases, the acetic acid (AA) selectivity increases (AA selectivity: one stage < two stages < three stages <... < n stages). (e) As the number of stages increases, the CO / CO2 selectivity decreases (CO / CO2 selectivity: one stage > two stages > three stages >... > n stages). (f) Salt quench and HEX between stages can contribute to steam generation, while water quench generally has no evaporation of liquid water and no heat recovery. (g) In the case of salt quench or HEX between stages, more DS is carried out in the mixed feed to the first reactor than with water quench (in water quench, liquid water is added to the second or third reactor for dilution). (h) Any combination of salt quench / HEX / water quench can be used for inter-stage cooling of the reactor effluent. (i) In salt quench or HEX, more stages result in more HP / VHP steam generation. The present disclosure captures one-stage, two-stage, and three-stage reactor systems that can be extended to an n-stage reactor system. The present disclosure captures one, two, or three catalyst cooling sections for each stage reactor (which can be extended to n catalyst cooling sections).

[0226] One embodiment is a method of operating an ODH reactor system, comprising providing a feed comprising ethane, oxygen, and a diluent (e.g., steam) to obtain a reaction mixture flowing through a tube side of an ODH reactor, the ODH reactor being a multi-tube reactor having a tube side and a shell side, the ODH reactor comprising a first cooling section and a second cooling section. The method comprises dehydrogenating ethane to ethylene (in the reaction mixture) over an ODH catalyst on the tube side. The method comprises flowing a first coolant (e.g., molten salt) through a shell side in the first cooling section, thereby maintaining the reaction mixture in the first cooling section at a first temperature (e.g., in a range of 300° C. to 450° C.). The method comprises flowing a second coolant (e.g., molten salt) through a shell side in the second cooling section, thereby maintaining the reaction mixture in the second cooling section at a second temperature (e.g., in a range of 350° C. to 500° C.), the first temperature being lower than the second temperature. The ODH reactor may have a shell-side flow barrier separating the first and second cooling sections such that the first and second coolants are not combined at the shell side. The second cooling section may be operationally upstream and downstream of the first cooling section in a flow direction of the reaction mixture. Again, the second cooling section may be separated from the first cooling section by a shell-side flow barrier. The method includes maintaining a temperature rise of the first coolant through the first cooling section below a first threshold (e.g., within a range of 2°C to 8°C) and maintaining a temperature rise of the second coolant through the second cooling section below a second threshold (e.g., within a range of 2°C to 8°C). The method may include discharging an effluent from the ODH reactor. The effluent may include ethylene, acetic acid, water, carbon dioxide, and carbon monoxide. The method may include heating the water with at least one of a first coolant discharged from the ODH reactor, a second coolant discharged from the ODH reactor, or an effluent discharged from the ODH reactor. In implementations, this heating of the water (e.g., BFW) with at least one of the first coolant, the second coolant, or the effluent vaporizes the water, thereby producing steam from the water.If so, the method includes flowing steam through tubes of a heat exchanger to heat the steam with a first coolant or a second coolant, or both, flowing on the shell side, thereby superheating the steam, where the water includes boiler feedwater, and discharging the superheated steam from the heat exchanger.

[0227] The method may include flowing a third coolant through a shell side in a third cooling section of the ODH reactor, thereby maintaining the reaction mixture on the tube side in the third cooling section at a third temperature, the third temperature being lower than the second temperature, the third cooling section being operatively downstream of the second cooling section in a flow direction of the reaction mixture and separated from the second cooling section by a second flow barrier on the shell side. The method may include heating water with at least one of a first coolant discharged from the ODH reactor, a second coolant discharged from the ODH reactor, a third coolant discharged from the ODH reactor, or an effluent discharged from the ODH reactor. In implementations, the tube side in the third cooling section does not include a catalyst, and in certain implementations, the water is not heated with the effluent.

[0228] Another embodiment is a method of operating an ODH reactor system, comprising providing a feed comprising ethane and oxygen into the tubes of the ODH reactor, the tubes having an ODH catalyst disposed therein, the feed comprising water (e.g., in the form of steam) as a diluent, thereby maintaining the feed outside the flammability limit. The method comprises dehydrogenating ethane to ethylene in the tubes over the ODH catalyst in the presence of oxygen in the reaction mixture. The ODH reactor is a multi-tubular fixed-bed reactor having a tube side and a shell side with tubes for the flow of the reaction mixture. The ODH reactor has a first cooling section and a second cooling section operationally upstream and downstream of the first cooling section in the flow direction of the reaction mixture. The first cooling section and the second cooling section may be separated by a flow barrier on the shell side. The method includes cooling the ODH catalyst to a first temperature (e.g., in the range of 300° C. to 450° C.) in a first cooling section via a first coolant flowing through a shell side in the first cooling section, and to a second temperature (e.g., in the range of 350° C. to 500° C.) in a second cooling section via a second coolant flowing through a shell side in the second cooling section, the first temperature being lower than the second temperature. The method includes, in response to specifying an increase in ethylene selectivity, maintaining the first temperature lower than the second temperature, thereby increasing ethylene selectivity, thereby decreasing the amount of oxygen in the feed and decreasing the amount of water in the feed.

[0229] The method may include specifying that the first temperature is lower than the second temperature to promote dehydrogenation of ethane to ethylene over reactions in the reaction mixture that give carbon dioxide and over reactions in the reaction mixture that give carbon monoxide, thereby increasing ethylene selectivity. The method may include maintaining a temperature rise of the first coolant through the first cooling section below a first threshold (e.g., in a range of 2°C to 8°C) and maintaining a temperature rise of the second coolant through the second cooling section below a second threshold (e.g., in a range of 2°C to 8°C). The method may include specifying that the temperature rise of the first coolant is maintained below the first threshold and the temperature rise of the second coolant is maintained below the second threshold to promote dehydrogenation of ethane to ethylene over reactions that give carbon dioxide and over reactions that give carbon monoxide, thereby increasing ethylene selectivity. Maintaining the temperature rise of the first coolant below a first threshold and maintaining the temperature rise of the second coolant below a second threshold may be responsive to specifying an increase in ethylene selectivity, increasing the ethylene selectivity, thereby decreasing the amount of oxygen in the feed and decreasing the amount of water in the feed.

[0230] The reaction of ethane with oxygen in the reaction mixture may include a first total reaction including dehydrogenation of ethane to ethylene, a second total reaction to give acetic acid, a third total reaction to give carbon monoxide, and a fourth total reaction to give carbon dioxide. The method may include specifying an increase in ethylene selectivity by promoting the first total reaction over the third total reaction and the fourth total reaction, where the first total reaction consumes a lesser stoichiometric amount of oxygen than each of the third total reaction and the fourth total reaction.

[0231] The method may include discharging the reaction mixture as an effluent from the ODH reactor, the effluent including ethylene, acetic acid, water, carbon dioxide, carbon monoxide, and unreacted ethane. The method may include heating the boiler feedwater with at least one of the first coolant, the second coolant, or the effluent. In implementations, heating the boiler feedwater vaporizes the boiler feedwater, thereby producing steam from the boiler feedwater. The method may include configuring the ODH reactor to specify an increase in ethylene selectivity, thereby reducing the tube to a specified diameter or less in response to increasing the ethylene selectivity. The specified diameter may be, for example, a 1.25 inch diameter (e.g., nominal diameter, outer diameter, or inner diameter), the linear velocity of the reaction mixture in the tubes is in a range of 150 cm / s to 500 cm / s, and the gas hourly space velocity of the reaction mixture through the ODH catalyst in the tubes is in a range of 1,500 h -1 (hr -1 )~10,000hr -1 is within the range.

[0232] Yet another embodiment is an ODH reactor system comprising an ODH reactor (multi-tubular fixed bed reactor) with a first cooling section and a second cooling section separated by a flow barrier on the shell side. The ODH reactor comprises a tube side having an ODH catalyst for receiving a feed comprising ethane, oxygen, and steam, dehydrogenating the ethane to ethylene in a reaction mixture, and discharging an effluent comprising ethylene, acetic acid, water, carbon dioxide, carbon monoxide, and unreacted ethane. The steam in the feed may act as a diluent to place the feed outside the flammability limit. The ODH reactor may be configured to produce acetic acid in the reaction mixture on the tube side. The dehydrogenation of ethane to ethylene may be a first total reaction of ethane with oxygen on the tube side. The configured ODH reactor may provide a reaction of ethane with oxygen in the reaction mixture on the tube side, including a second total reaction to give acetic acid, a third total reaction to give carbon monoxide, and a fourth total reaction to give carbon dioxide.

[0233] The second cooling section may be operatively upstream and downstream of the first cooling section with respect to the flow of the reaction mixture. The shell side is configured to receive a first coolant (e.g., molten salt) in the first cooling section and maintain a temperature of the tube-side ODH catalyst in the first cooling section at a first temperature (e.g., in the range of 300°C to 450°C) and receive a second coolant (e.g., molten salt) in the second cooling section and maintain a temperature of the tube-side ODH catalyst in the second cooling section at a second temperature (e.g., in the range of 350°C to 500°C), the first temperature being lower than the second temperature. Again, the second cooling section may be operatively upstream and downstream of the first cooling section with respect to the flow direction of the reaction mixture. The ODH reactor system includes a first coolant supply system having a pump for providing the first coolant to the first cooling section and maintaining a temperature rise of the first coolant through the first cooling section below a first threshold (e.g., in the range of 2°C to 8°C). The ODH reactor system includes a second coolant supply system having a pump for providing a second coolant to the second cooling section and maintaining a temperature rise of the second coolant through the second cooling section below a second threshold (e.g., in a range of 2°C to 8°C). The ODH reactor system includes a first heat exchanger for heating a first water (e.g., BFW) with the first coolant for steam generation of the first water. The steam generation may include a first heat exchanger configured to vaporize the first water into steam. The ODH reactor system may include a steam drum for receiving steam from the first heat exchanger and discharging the steam. Alternatively, the first heat exchanger for heating the first water may be a first heat exchanger configured to preheat the first water for heating the first water to vaporize the first water in the steam drum.

[0234] The ODH reactor system may include a second heat exchanger for heating a second water (e.g., BFW) with a second coolant discharged from the second cooling section for steam generation of the second water. The ODH reactor system may include a third heat exchanger for heating a third water (e.g., BFW) with an effluent for steam generation of the third water. Finally, the ODH reactor may have a third cooling section operationally upstream and downstream of the second cooling section with respect to the flow of the reaction mixture for receiving a third coolant on the shell side. The third cooling section may be separated from the second cooling section by a second flow barrier on the shell side.

[0235] Yet another embodiment is a method of operating an ODH reactor system. The ODH reactor system includes a first ODH reactor and a second ODH reactor, each of which is a multi-tubular fixed-bed reactor having a shell side and a tube side. The first ODH reactor and the second ODH reactor each have a first cooling section and a second cooling section. The first ODH reactor and the second ODH reactor each may have a flow barrier on the shell side separating the first cooling section and the second cooling section. The second ODH reactor is arranged in series upstream and downstream of the operation of the first ODH reactor. The method included providing a feed to the first ODH reactor, the feed including ethane, oxygen, and a diluent (e.g., steam), and dehydrogenating the ethane to ethylene over an ODH catalyst in a reaction mixture flowing through the tube side of each of the first ODH reactor and the second ODH reactor. The method includes flowing a coolant (e.g., molten salt) through a shell side in a first cooling section and a second cooling section of each of the first ODH reactor and the second ODH reactor, thereby cooling the tube side reaction mixture and the ODH catalyst. The method includes maintaining a temperature rise of the coolant through each of the first cooling section and the second cooling section of each of the first ODH reactor and the second ODH reactor below a threshold value (e.g., 2°C to 8°C). Cooling the reaction mixture may include maintaining a tube side reaction mixture in the first cooling section of the first ODH reactor at a temperature lower than a temperature of the tube side reaction mixture in the second cooling section of the first ODH reactor and maintaining a tube side reaction mixture in the first cooling section of the second ODH reactor at a temperature lower than a temperature of the tube side reaction mixture in the second cooling section of the second ODH reactor. In implementations, the temperature of the reaction mixture in the first cooling section of each of the first ODH reactor and the second ODH reactor is in the range of 300°C to 450°C, and the temperature of the reaction mixture in the second cooling section of each of the first ODH reactor and the second ODH reactor is in the range of 350°C to 500°C.

[0236] The method includes discharging a first effluent from a first ODH reactor to a second ODH reactor, the first effluent including ethylene, acetic acid, water, carbon dioxide, carbon monoxide, and unreacted ethane. The method includes injecting oxygen into the first effluent. The method may include cooling the first effluent upstream of injecting oxygen into the first effluent, or cooling the reaction mixture in a third cooling section in the first ODH reactor discharging as the first effluent from the first ODH reactor, or a combination thereof. The method may include injecting liquid water into the first effluent, thereby vaporizing the liquid water via heat from the first effluent to cool the first effluent. The method may include cooling the first effluent by a heat exchanger using boiler feedwater as a cooling medium, thereby vaporizing the boiler feedwater into steam, or heating the boiler feedwater to vaporize the boiler feedwater into steam in a steam drum.

[0237] The method may include heating water with a coolant discharged from at least one of the first cooling section of the first ODH reactor, the second cooling section of the first ODH reactor, the first cooling section of the second ODH reactor, or the second cooling section of the second ODH reactor, where heating the water vaporizes the water into steam or preheats the water for vaporizing the water into steam in a steam drum. For the first ODH reactor and the second ODH reactor, the second cooling section may be defined as being operationally downstream of the first cooling section in the flow direction of the reaction mixture and separated from the first cooling section by a shell-side flow barrier. The method may include flowing a coolant through the shell side in a third cooling section of the first ODH reactor, thereby cooling the reaction mixture on the tube side in the third cooling section, where the third cooling section is operationally downstream of the second cooling section of the first ODH reactor in the flow direction of the reaction mixture and separated from the second cooling section by a shell-side second flow barrier. In implementations, the tube side in the third cooling section of the first ODH reactor stream does not include catalyst. The method may include discharging a second effluent from the second ODH reactor, the second effluent including ethylene, acetic acid, water, carbon dioxide, and carbon monoxide. The method may include generating steam via heat from at least one of the coolant discharged from the first ODH reactor, the coolant discharged from the second ODH reactor, the first effluent discharged from the first ODH reactor, or the second effluent discharged from the second ODH reactor. Finally, the method may include heating the steam with the coolant from the first ODH reactor or the second ODH reactor, or both, thereby superheating the steam.

[0238] Yet another embodiment is a method of operating an ODH reactor system, the method including providing a feed including ethane, oxygen, and a diluent to a first ODH reactor having a tube side and a shell side to obtain a first reaction mixture flowing through the tube side. The feed may have a diluent (e.g., steam) to maintain the feed outside flammability limits. The method includes dehydrogenating ethane to ethylene in the first reaction mixture flowing through the tube side over an ODH catalyst on the tube side, the first ODH reactor having a first cooling section and a second cooling section operatively downstream of the first cooling section. In implementations, the first cooling section and the second cooling section are separated by a shell-side flow barrier. The method includes flowing a first coolant through the shell side in the first cooling section, thereby maintaining the ODH catalyst in the first cooling section at a first temperature. The method includes flowing a second coolant through a shell side in the second cooling section, thereby maintaining the ODH catalyst in the second cooling section at a second temperature. The method includes designating a first temperature to be lower than a second temperature to promote ethylene selectivity in the first reaction mixture in the first cooling section. The method may include designating a temperature rise of the first coolant through the first cooling section to be less than a first threshold to promote ethylene selectivity in the first reaction mixture, and designating a temperature rise of the second coolant through the second cooling section to be less than a second threshold to promote ethylene selectivity in the first reaction mixture. The method may include maintaining a temperature rise of the first coolant through the first cooling section less than a first threshold, the first temperature being less than a second temperature, and maintaining a temperature rise of the second coolant through the second cooling section less than a second threshold. The method may include discharging the first reaction mixture from a tube side from the first ODH reactor to a second ODH reactor as a first effluent to obtain a second reaction mixture that flows through the second ODH reactor.

[0239] The method may include cooling the first effluent by injecting liquid water into the first effluent or by a heat exchanger using boiler feed water as a cooling medium. The method may include injecting oxygen into the first effluent, the first effluent discharged from the first ODH reactor comprising ethylene, acetic acid, water, carbon dioxide, carbon monoxide, and unreacted ethane. The method may include flowing a third coolant through a shell side in a third cooling section of the first ODH reactor, thereby cooling the first reaction mixture on a tube side in the third cooling section, the third cooling section being operatively downstream of the second cooling section and separated from the second cooling section by a second flow barrier on the shell side. The method may include injecting oxygen into the first effluent. In some implementations, the tube side in the third cooling section (of the first ODH reactor) does not include a catalyst. The method may include heating water with at least one of a first coolant discharged from the first cooling section, a second coolant discharged from the second cooling section, or the first effluent, thereby facilitating the generation of steam from the water. In implementations, heating the water (e.g., boiler feedwater) to facilitate the generation of steam from the water includes heating the water to vaporize the water into steam or preheating the water to vaporize the water into steam in a steam drum. The method may include heating the steam with a first coolant from a shell side of the first cooling section, or a second coolant from a shell side of the second cooling section, or both, thereby superheating the steam.

[0240] The method may include dehydrogenating ethane to ethylene in a second reaction mixture flowing through a tube side of a second ODH reactor over an ODH catalyst in the tube side of the second ODH reactor, the second ODH reactor having a third cooling section and a fourth cooling section. The second ODH reactor may be a multi-tubular fixed bed reactor having a tube side and a shell side, the second reaction mixture flowing through the tube side of the second ODH reactor. The method may include discharging the second reaction mixture from the second ODH reactor as a second effluent. The method may include flowing a third coolant through the shell side of the second ODH reactor in the third cooling section, thereby maintaining the ODH catalyst in the third cooling section at a third temperature, and flowing a fourth coolant through the shell side in the fourth cooling section, thereby maintaining the ODH catalyst in the fourth cooling section at a fourth temperature, the fourth temperature being higher than the third temperature. The method may include maintaining a temperature rise of the third coolant through the third cooling section below a third threshold and maintaining a temperature rise of the fourth coolant through the second cooling section below a fourth threshold. The method may include heating water in at least one of the first coolant discharged from the first cooling section, the second coolant discharged from the second cooling section, the third coolant discharged from the third cooling section, the fourth coolant discharged from the fourth cooling section, the first effluent, or the second effluent, where heating the water vaporizes the water into steam or preheats the water for vaporizing the water into steam in the steam drum.

[0241] Yet another embodiment is an ODH reactor system comprising a first ODH reactor (multi-tubular fixed bed reactor) having a first cooling section and a second cooling section separated by a flow barrier on a first shell side. The second cooling section is operationally upstream and downstream of the first cooling section. The first ODH reactor comprises a first tube side having an ODH catalyst for receiving a feed comprising ethane, oxygen, and steam, dehydrogenating the ethane to ethylene in a first reaction mixture, and discharging a first effluent comprising ethylene, acetic acid, water, carbon dioxide, carbon monoxide, and unreacted ethane through a first effluent discharge conduit to the second ODH reactor. The steam in the feed may act as a diluent to place the feed outside the flammability limit. The first ODH reactor comprises a first shell side for receiving a first coolant in a first cooling section and maintaining a temperature of the ODH catalyst in the first cooling section at a first temperature, and a second coolant in a second cooling section and maintaining a temperature of the ODH catalyst in the second cooling section at a second temperature, the first temperature being lower than the second temperature. The ODH reactor system comprises a second ODH reactor (multi-tubular fixed bed reactor) having a third cooling section and a fourth cooling section separated by a flow barrier on the second shell side. The fourth cooling section is operationally upstream and downstream of the third cooling section. The second ODH reactor comprises a second tube side having an ODH catalyst for receiving the first effluent, dehydrogenating ethane to ethylene in a second reaction mixture, and discharging the second effluent through a second effluent discharge conduit. The second ODH reactor comprises a second shell side for receiving a third coolant in a third cooling section and maintaining a temperature of the ODH catalyst in the third cooling section at a third temperature, and a fourth coolant in a fourth cooling section and maintaining a temperature of the ODH catalyst in the fourth cooling section at a fourth temperature, the third temperature being lower than the fourth temperature. In some implementations, the first temperature and the third temperature are each in a range of 300° C. to 450° C., and the second temperature and the fourth temperature are each in a range of 350° C. to 500° C.

[0242] The ODH reactor system may include a first coolant supply system having a pump to provide a first coolant to the first cooling section and to maintain a temperature rise of the first coolant through the first cooling section below a first threshold, a second coolant supply system comprising a pump to provide a second coolant to the second cooling section and to maintain a temperature rise of the second coolant through the second cooling section below a second threshold, a third coolant supply system comprising a pump to provide a third coolant to the first cooling section and to maintain a temperature rise of the third coolant through the third cooling section below a third threshold, and a fourth coolant supply system comprising a pump to provide a fourth coolant to the fourth cooling section and to maintain a temperature rise of the fourth coolant through the fourth cooling section below the second threshold. In some implementations, the first threshold and the second threshold are in a range of 2°C to 8°C. In implementations, the first coolant and the second coolant each are or include a molten salt.

[0243] The ODH reactor system may include an oxygen supply conduit for injecting oxygen into the first effluent flowing through the first effluent discharge conduit. The ODH reactor system may include an injection water conduit for injecting liquid water into the first effluent flowing through the first effluent discharge conduit to cool the first effluent. The ODH reactor system may include a heat exchanger disposed along the first effluent discharge conduit for heating the water to cool the first effluent with the water and thereby generate steam from the water. The first ODH reactor may include a fifth cooling section operatively upstream and downstream of the second cooling section for cooling the first reaction mixture flowing through a first tube side in the fifth cooling section, the fifth cooling section and the second cooling section being separated by a second flow barrier on the first shell side. In some implementations, the first tube side in the fifth cooling section does not have an ODH catalyst or other catalysts.

[0244] The ODH reactor system may include a heat exchanger for heating water with a first coolant discharged from the first cooling section to generate steam from the water. The ODH reactor system may include a superheater heat exchanger for heating steam with a first coolant from the first shell side or a second coolant from the first shell side, or both, to superheat the steam. The ODH reactor system may include a heat exchanger for heating water with a second coolant discharged from the second cooling section to generate steam from the water. The ODH reactor system may have a heat exchanger for heating water with a third coolant discharged from the third cooling section to generate steam from the water. The ODH reactor system may have a heat exchanger for heating water with a fourth coolant discharged from the fourth cooling section to generate steam from the water. The ODH reactor system may have a heat exchanger disposed along the second effluent discharge for heating water with the second effluent to generate steam from the water. The first ODH reactor may be configured to produce acetic acid from ethane in a first reaction mixture flowing through a first tube side, and the second ODH reactor is configured to produce acetic acid from ethane in a second reaction mixture flowing through a second tube side.

[0245] example The examples (for configurations 1-13) encompass reactions in an ODH reactor occurring at temperatures between 300-450°C using a low temperature ODH catalyst (MoVNbTeOx as previously mentioned) to produce primarily ethylene with high selectivity. A diluent is used to stay outside the flammable envelope of the ethane-oxygen mixture. Vaporized water can be utilized as a diluent to achieve staying outside the flammable envelope. Based on the pressure and temperature of the mixed feed to the reactor, the target oxygen concentration can vary. This disclosure includes reactor design and setup configurations with different stages and different reactor cooling schemes presented for comparison. In the configurations, HP / VHP steam is generated by cooling high temperature coolant (high temperature molten salt) exhausted from different reactor sections. The comparison numbers (values) presented below are intended to show the relative advantages or disadvantages of one configuration over another, as examples. Configurations 1-13 as several configurations of reactor systems and reactor designs are summarized below, taking into account the compiled data (see Tables 2-4). In the comparison, configuration 2 is selected as the base case.

[0246] The reactor design was considered via gPROMS® platform software (gPROMS ProcessBuilder version 1.3.1) by Siemens Process Systems Engineering (PSE). Process simulation was performed using Aspen Plus® V10. The SR-POLAR equation of state was utilized for the simulation. Aspen Plus® software is available from Aspen Technology, Inc., headquartered in Bedford, Massachusetts, USA.

[0247] Configuration 1 (implementation of FIG. 3) is a single-stage reactor with one catalyst cooling section, 1-inch tubes, and less than 5°C temperature rise of the coolant (salt). Includes a TLE after the reactor for HP / VHP steam generation or BFW preheat. This can be characterized as the simplest configuration to build a reactor. However, with only one cooling section, the highest possible dilution is required. This is a relatively large reactor per ethylene production unit. The reactor requires about 65% more tubes with about 35% longer tubes than Configuration 2 (baseline), which means about 125% more catalyst. This translates to a longer residence time or smaller GHSV compared to Configuration 2. Ethylene and AA selectivities are lower than Configuration 2, but CO / CO2 selectivities are much higher. This means more molten salt to cool the reactor and more steam generation. Due to the high dilution requirements and poor performance compared to configuration 2, the CO2 intensity (mass ratio) (e.g., tons of CO2 emitted per ton of ethylene produced) of the ODH plant (whole plant) is about 50% higher than configuration 2.

[0248] Configuration 2 (implementation of FIG. 4) is a single stage reactor with two catalyst cooling sections, 1 inch tubes, and less than 5° C. temperature rise in the molten salt, and a post-reactor TLE for HP / VHP steam generation or BFW preheat. Again, Configuration 2 is optionally the base case in the comparison of Configurations 1-13. Configuration 2 generally has much better performance than Configuration 1, as discussed above.

[0249] Configuration 3 (implementation of FIG. 4) is a single-stage reactor with two catalyst cooling sections, 1-inch tubes, and a temperature rise of about 15° C. in the coolant (molten salt) across each of the two cooling sections, as well as a TLE after the reactor for HP / VHP steam generation or BFW preheat. Thus, the basis of configuration 3 is the same as configuration 2, except that the temperature rise of the salt is 15° C. instead of less than 5° C. The results of configuration 3 show that the temperature rise of the reactor coolant (here molten salt) should generally be limited. A higher temperature rise would result in less molten salt circulation and a lower heat transfer coefficient (HTC). This would result in about 9% lower ethylene and AA selectivity and 9% higher CO / CO2 selectivity compared to configuration 2. To achieve the same amount of ethylene production, the number of tubes would be more than doubled and the tube length would be about 140% longer, which means about 420% more catalyst than configuration 2. This may translate to a longer residence time or a smaller GHSV compared to configuration 2. Due to the high dilution requirements and poor performance compared to configuration 2, the whole plant CO2 intensity is about 40% higher than in configuration 2.

[0250] Configuration 4 (implementation of FIG. 4) is a single-stage reactor with two catalyst cooling sections, 1.25-inch tubes, and a temperature rise of less than 5° C. in the molten salt, as well as a TLE after the reactor for HP / VHP steam generation or BFW preheat. The fundamentals are the same as Configuration 2, except that 1.25-inch tubes are used instead of 1-inch tubes. This shows that larger tubes can be used in the reactor design, but the heat removal and performance will not be as effective as with the smaller tubes of Configuration 2. The larger tubes have smaller HTCs in the tubes and poorer heat removal. This will result in slightly lower ethylene and AA selectivity and slightly higher CO / CO2 selectivity compared to Configuration 2. To achieve the same amount of ethylene production, the number of tubes needs to be 20% less (easier to build), the tube length is about 35% longer, and about 65% more catalyst than Configuration 2. This may translate to a longer residence time or smaller GHSV compared to Configuration 2. Due to the slightly higher dilution requirements and slightly poorer performance compared to configuration 2, the CO2 intensity of the ODH plant is about 5% higher than in configuration 2, which is very comparable. Nevertheless, the lower catalyst loading makes configuration 2 more attractive.

[0251] Configuration 5 (implementation of FIG. 4) is a single-stage reactor with two catalyst cooling sections, 1.5-inch tubes, and less than 5° C. temperature rise in the molten salt, and a TLE after the reactor for HP / VHP steam generation or BFW preheat. This shows that larger tubes can be used in the reactor design, but the heat removal and performance are not as effective as with smaller tubes (configurations 2 and 4). The larger tubes have smaller HTCs in the tubes and poorer heat removal. This would result in about 5% lower ethylene and AA selectivity and 5% higher CO / CO2 selectivity compared to configuration 2. To achieve the same amount of ethylene production, 20% fewer tubes (easier to build) are needed and the tubes are almost twice as long, which means about 265% more catalyst than configuration 2. This can translate to a longer residence time or smaller GHSV compared to configuration 2. Due to the higher dilution requirements and poorer performance compared to configuration 2, the CO2 intensity of the ODH plant is about 25% higher than configuration 2.

[0252] Configuration 6 (implementation of FIG. 5) is a single-stage reactor with two catalytically cooled sections and one non-catalytically cooled section for BFW heating or V / HP steam generation, 1-inch tubing, and less than 5° C. temperature rise in the molten salt. This indicates that instead of a TLE after the reactor, added to the end of the reactor is another cooling section with molten salt circulation, and the high temperature molten salt is utilized to preheat boiler feedwater (BFW) or generate HP / VHP steam. This increases the length of the reactor for this third non-catalytically cooled section and generally does not affect other aspects of the reactor design or performance compared to configuration 2.

[0253] Configuration 7 (implementation of FIG. 6) is a single-stage reactor with three catalyst cooling sections, 1-inch tubes, less than 5° C. temperature rise in the molten salt, and a TLE after the reactor for HP / VHP steam generation or BFW preheat. This shows that adding an additional cooling section would generally improve reactor performance since the reaction can generally be conducted in a more temperature-controlled manner. This would result in slightly higher ethylene selectivity at the expense of lower AA / CO / CO2 selectivity compared to Configuration 2. To achieve the same amount of ethylene production, the number of tubes needs to be 10% less and 10% shorter, which means about 20% less catalyst than Configuration 2. This may translate to a shorter residence time or a larger GHSV compared to Configuration 2. Due to the lower dilution requirements and superior performance compared to Configuration 2, the CO2 intensity of the ODH plant is slightly lower than Configuration 2. Configuration 7 shows that the number of catalyst cooling sections can be extended to “n”. However, this would increase the complexity of the reactor design and manufacturing.

[0254] Configuration 8 (implementation of FIG. 7) is a two-stage reactor system with two catalyst cooling sections in each stage, 1-inch tubes, less than 5° C. temperature rise in molten salt, interstage water quench, interstage oxygen addition, and a TLE after the second reactor for HP / VHP steam generation or BFW preheat. Again, this configuration is a two-stage reactor system. All the ethane, a portion of the oxygen, and the water diluent enter the first reactor with two catalyst cooling sections. The first reactor converts nearly all of the oxygen that enters (feeds) the first reactor. The effluent from the first reactor is quenched with liquid water to reduce the temperature of the gas (effluent). Oxygen is then added. The addition of quench water will prevent sudden spontaneous ignition of the gas components (ethylene, ethane, AA, CO) when oxygen is added. The main idea of ​​the two-stage reactor is to split the oxygen between the two stages. This would reduce the demand for oxygen in the first stage and therefore dilution water in the first stage and the entire reactor system. In the second stage, no additional dilution is needed because the water added to the first stage and the water produced are still in the mixture.

[0255] This two-stage reactor system with interstage water quench and interstage addition would result in slightly lower ethylene selectivity. However, it would increase AA selectivity by more than 2% and decrease CO / CO2 selectivity compared to configuration 2. To achieve the same amount of ethylene production, the first stage reactor is much smaller than the second stage reactor. In the first stage, the number of tubes needs to be 65% less and 60% shorter than configuration 2. Meanwhile, in the second stage, the number of tubes needs to be 30% more and 15% shorter than the single reactor of configuration 2. The second stage reactor is relatively large, but comparable to one single stage reactor (configuration 2). The total catalyst is about 25% more in the two-stage reactor compared to configuration 2 with a single stage reactor. The residence time in the first stage is very short, while the second stage has a residence time comparable to that of the reactor in configuration 2. Due to the much lower dilution requirement and slightly better performance compared to configuration 2, the CO2 intensity of the ODH plant is 40% lower than configuration 2.

[0256] Configuration 9 (implementation of FIG. 8) is a two-stage reactor system with two catalyst-cooled sections in each stage, 1-inch tubing, less than 5° C. temperature rise in the molten salt, one non-catalytically cooled section at the end of the first stage, oxygen between the stages, and a TLE after the second reactor for HP / VHP steam generation or BFW preheat. Similar to configuration 8, but instead of quenching the effluent from the first stage reactor with quench water, an additional cooling section, a non-catalytically cooled section, is added to the end of the first stage reactor. This means that the first stage has two catalyst-cooled sections with molten salt circulation and one non-catalytically cooled section with molten salt circulation. This additional section would increase the complexity of the design and manufacture of the first reactor, but could significantly improve heat recovery from the first stage reactor effluent. In configuration 8, no heat recovery is performed because the quench water evaporates. In contrast, the hot molten salt from this third cooling section of configuration 9 preheats the BFW or generates HP / VHP steam.

[0257] Configuration 9 has slightly lower ethylene selectivity than Configuration 8. However, it will slightly increase AA selectivity and decrease CO / CO2 selectivity compared to Configuration 8. To achieve the same amount of ethylene production, the first stage reactor is much smaller than the second stage reactor. In the first stage, the number of tubes needs to be 60% less and 40% shorter than the single reactor of Configuration 2. However, it is larger than the first stage reactor of Configuration 8. Meanwhile, in the second stage, the number of tubes needs to be 20% more and 15% shorter than the single reactor of Configuration 2. The second stage reactor is relatively equivalent to one single stage reactor (Configuration 2). However, the second stage of Configuration 9 is smaller than the second stage reactor of Configuration 8. The total catalyst is about 15% more in the second reactor (two stage reactor) compared to the single reactor of Configuration 2 (single stage reactor). The residence time in the first stage is very short, while the second stage has a residence time comparable to that of Configuration 2. Due to the much lower dilution requirements and significant heat recovery from the first stage reactor effluent compared to configuration 2, as well as slightly better performance, the whole plant CO2 intensity is 55% lower than configuration 2 and almost 10% lower than configuration 8.

[0258] Configuration 10 (implementation of FIG. 9) is a two-stage reactor system with two catalyst cooling sections in each stage, 1-inch tubes, less than 5° C. temperature rise in the molten salt, HEX quench between stages, oxygen addition between stages, and a TLE after the second reactor for HP / VHP steam generation or BFW preheat. Similar to configuration 10, but instead of a third cooling section in the first stage reactor, a HEX is used between the two stages. This HEX is similar to a TLE after the entire reactor system and can be used for either BFW preheat or HP / VHP steam generation. There is generally no difference between the performance of configuration 10 and configuration 9.

[0259] Configuration 11 (implementation of FIG. 10) is a three-stage reactor system with two catalyst cooling sections in each stage, 1-inch tubes, less than 5° C. temperature rise in the molten salt, water quenching between stages, oxygen addition between stages, and a TLE after the third reactor for HP / VHP steam generation or BFW preheat. This is similar to configuration 8, but with a third reactor. All of the ethane, some of the oxygen, and water diluent enter the first reactor (with two catalyst cooling sections) which converts nearly all of the oxygen. The effluent from the first reactor is quenched with liquid water to reduce the temperature of the gas (effluent). Oxygen is then added between the first and second reactors. The addition of quench water will prevent sudden spontaneous ignition of the gas components (ethylene, ethane, AA, CO) when oxygen is added. This effluent passes through the second stage in a similar approach to the first stage. The effluent from the second stage is quenched again using quench water, then oxygen is added and it proceeds to the third stage. The main idea of ​​the third reactor (three-stage reactor) is to split the oxygen between the three stages. This will reduce the demand for oxygen in the first stage and therefore for dilution water in the first stage and the entire reactor system. In the second and third stages, there is no need for additional dilution, since the water added to the first stage is still in the mixture.

[0260] This three-stage reactor system with water quench and oxygen interstage addition would result in low ethylene selectivity. However, it would increase AA selectivity by about 4% and decrease CO / CO2 selectivity compared to configuration 2. This shows the same trend from the second stage (configuration 8) to the third stage. AA selectivity is improved and ethylene, CO / CO2 selectivity is decreased. To achieve the same amount of ethylene production, the first stage reactor is much smaller than the second and third stage reactors. The second stage is also much smaller than the third stage. In the first stage, the number of tubes needs to be 80% less and 70% shorter than configuration 2. In the second stage, the number of tubes needs to be 40% less and 55% shorter than configuration 2. Meanwhile, in the third stage, the number of tubes needs to be 60% more than configuration 2 but about 30% shorter. The total catalyst is about 40% more in the third reactor (three-stage reactor) compared to configuration 2 and also larger than configuration 8. The first and second stages have very low residence times, while the third stage has a residence time comparable to the second stage in configurations 2 and 8. Due to the much lower dilution requirements and slightly better performance compared to configuration 2, the overall plant CO2 intensity is 50% lower than configuration 2 and 10% better (lower) than configuration 8. This indicates that adding a stage would improve the overall performance of the ODH plant. However, going from one to two stages reduces the CO2 intensity by 40%, while the increment from two to three stages is only 10%, which may make two stages more attractive. Adding another stage would add capital and operating costs to the plant and complexity to the reactor design and manufacture.

[0261] Configuration 12 (implementation of FIG. 11) is a three-stage reactor system with two catalyst-cooled sections in each stage, 1-inch tubing, less than 5° C. temperature rise in the molten salt, one non-catalytically cooled section at the end of the first and second stages, oxygen injection between stages, and a TLE after the third reactor for HP / VHP steam generation or BFW preheat. Similar to configuration 11, but instead of quenching the effluent from the first and second stage reactors with quench water, an additional non-catalytically cooled section is added to the first and second stage reactors. This means that the first and second stages have two catalyst-cooled sections with molten salt circulation and one non-catalytically cooled section with molten salt circulation. This additional section would increase the complexity of the design and manufacture of the first and second reactors, but would greatly improve the heat recovery from the first and second stage reactor effluent. In configuration 11, the quench water is evaporated and no heat recovery is performed. In contrast, in configuration 12, the hot molten salt from the third cooling section is used to preheat the BFW or V / HP steam generation.

[0262] Additionally, configuration 12 has slightly lower ethylene selectivity than configurations 2, 9, and 11. However, it would slightly increase AA selectivity and decrease CO / CO2 selectivity compared to configurations 2, 9, and 11. To achieve the same amount of ethylene production, the first stage reactor is much smaller than the second and third stage reactors. In addition, the second stage is much smaller than the third stage. In the first stage, the number of tubes needs to be 75% less and 55% shorter than configuration 2. In the second stage, the number of tubes needs to be 25% less and 45% shorter than configuration 2. Meanwhile, in the third stage, the number of tubes needs to be 40% more than configuration 2 but about 35% shorter. The total catalyst is about 15% more in the three-stage reactor (third reactor) compared to configuration 2, but similar to the two-stage reactor (second reactor) of configuration 9. The residence times in the first and second stages are very short, while the third stage has a comparable residence time to configuration 2. Due to the much lower dilution requirements and higher heat recovery from the effluent of the first and second stage reactors as compared to configurations 2 and 9, as well as slightly better performance, the CO2 intensity of the ODH plant is 70% lower than configuration 2, almost 15% lower than configuration 9, and 20% lower than configuration 11. Thus, adding an additional stage would improve the overall performance of the ODH plant in terms of CO2 intensity.

[0263] Configuration 13 (implementation of FIG. 12) is a three-stage reactor system with two catalyst cooling sections in each stage, 1-inch tubes, less than 5° C. temperature rise in the molten salt, HEX quench between stages, oxygen addition between stages, and a TLE after the third reactor for HP / VHP steam generation or BFW preheat. Similar to configuration 12, but instead of a third cooling section in the first and second stage reactors, a HEX is used between stages (see FIG. 12). These HEX are similar to the TLE after the entire reactor system and can be used for either BFW preheat or HP / VHP steam generation. There is generally no difference between the performance of configuration 13 and that of configuration 12.

[0264] Table 2 is the data for configurations 1-7, which are single reactor systems with a single ODH reactor. ΔT coolant is the temperature rise (Temp Rise) of the coolant (molten salt) through each cooling section. The number of tubes (#), tube length, active catalyst (ODH catalyst), space-time yield (STY), and total flow rate are assigned 100% to configuration 2 as the base case, and the remaining configurations are assigned as a percentage relative to 100% of configuration 2. Total mass flow rate is the total mass flow rate (mass per hour) of the feeds (ethane, oxygen, and dilution steam) to the ODH reactor. No TLE is used for configuration 6, since the third cooling section in configuration 6 is a non-catalytic cooling section. This non-catalytic cooling section cools the reaction mixture with coolant (molten salt) before the reaction mixture is discharged as effluent, and therefore the cooling can be referred to as a salt quench. The Δ symbol for ethane conversion means that the listed value is the absolute percent difference from the ethane conversion of configuration 2. Similarly, the Δ symbol for the selectivity ethane conversion in row 3 means that the listed value is the absolute percent difference from the given conversion in configuration 2. The O2 / ethane and water / ethane mass ratios are relative to the feed to the ODH reactor, with water being the dilution steam. The ethane feed rate (mass per hour) is the same in all configurations 1-7. Finally, the tube diameters in the various applications may be outer diameter (OD), inner diameter (ID), or nominal diameter, but the given numbers for diameters in Table 2 are OD for the simulations. In these examples for the simulations, the 1-inch tubes have an OD of 1 inch, a tube wall thickness of 0.083 inches, and an ID of 0.834 inches, the 1.25-inch tubes have an OD of 1.25 inches, a tube wall thickness of 0.120 inches, and an ID of 1.01 inches, and the 1.5-inch tubes have an OD of 1.5 inches, a tube wall thickness of 0.134 inches, and an ID of 1.232 inches. [Table 2]

[0265] Table 3 provides data for configurations 8-13. As explained, configurations 8-13 are multi-reactor systems with two or more ODH reactors (stages). All configurations 8-13 have the same ethane feed (mass per hour) to the ODH reactor system (specifically the first ODH reactor). All configurations 8-13 have 1 inch tubing in the ODH reactors (1 inch is the outer diameter (OD) of the tubing for the simulation), TLE after the last ODH reactor, and less than 5°C temperature rise of the coolant molten salt through each cooling section. The number (#) of cooling sections is given per stage. For example, the 3 / 2 listed for configuration 9 means 3 cooling sections in the first reactor (first stage) and 2 cooling sections in the second reactor (second stage). The number of tubes (#), tube length, active catalyst (ODH catalyst), space-time yield (STY), and total flow rate are assigned 100% to the single ODH reactor of configuration 2 as the base case, and the corresponding values ​​for the ODH reactors of configurations 8-13 are assigned as a percentage of 100% of configuration 2. The total mass flow rate is the total flow rate (mass per hour) of the feed to the first ODH reactor (ethane, oxygen, and dilution steam), oxygen injected between stages, and any water injected between stages (for water quench configurations 8 and 11). As in Table 2, the Δ symbol for ethane conversion (for the multi-reactor system) means that the value listed is the absolute percentage difference from the ethane conversion of the single reactor system of configuration 2. Similarly, the Δ symbol for selectivity means that the value listed is the absolute percentage difference from the given conversion of configuration 2. The O2 / ethane mass ratio is the mass ratio of total oxygen (feed to first ODH reactor plus interstage injection) to ethane fed to the first ODH reactor. The water / ethane mass ratio is the mass ratio of water (dilution steam) in the feed to the first ODH reactor (as well as any interstage injected liquid water for water quench purposes in configurations 8 and 11) to ethane fed to the first ODH reactor. [Table 3]

[0266] Table 4 shows the results for configurations 1-13. The first row is the configuration number. Configurations 1-7 are ODH reactor systems having one ODH reactor (single reactor systems). Configurations 8-13 are ODH reactor systems having two or more ODH reactors (multi-reactor systems). In particular, configurations 8-10 have two ODH reactors in series (two-stage reactor systems) and configurations 11-13 have three ODH reactors in series (three-stage reactor systems).

[0267] The second row of Table 4 is the primary load (heat) demand for the ODH plant, which is a combination of (1) the heat demand of dilution steam generation for the reactor feed and (2) the solvent recovery in the acetic acid unit. More energy may be consumed for solvent recovery in the AA unit because there is more water. More dilution steam gives more cooling demand to condense the water / AA after the reactor system. More dilution steam also gives the AA unit more water in AA. Therefore, more solvent is utilized to separate the AA from the water, and therefore more heat for the reboiler in the solvent recovery tower and more cooling demand for the condenser in the solvent recovery tower.

[0268] The third row is the primary cooling demand in the ODH plant, which is a combination of (1) the cooling demand for condensation in the reactor effluent (including water condensation) and (2) the cooling demand for solvent recovery in the acetic acid unit. The fourth row of Table 2 is the reactor HP / VHP steam production. The fifth row is the mass ratio (e.g., kg / kg) of the LP / MP steam demand of the ODH plant to the HP / VHP steam produced in the reactor system. The sixth row is the CO2 intensity (emitted and non-emitted) of the ODH plant, which is the CO2 emissions per ethylene produced.

[0269] In Table 4, the load demand, cooling demand, steam generation, and CO2 intensity are assigned 100% to configuration 2 as the base case, and the remaining configurations have a percentage relative to 100% of configuration 2. Because less oxygen (and therefore less dilution steam) is fed to the first reactor in the two-stage reactor system, the load demand and cooling demand (and therefore CO2 intensity) are significantly reduced in the two-stage reactor system compared to the single-stage reactor system. [Table 4]

[0270] In general, for the configuration, any combination of water quench, HEX quench, or non-catalytic salt quench for the effluent of each stage of the reactor can be used. Additionally, ethane or steam can also be added between stages. Additionally, the salt flow versus the process flow in the tubes can be cocurrent or countercurrent (see, for example, Figures 4 and 4A). In configurations with two or more stages, each stage can be cocurrent or countercurrent. This means, for example, that if the first stage is cocurrent, the second stage can be cocurrent or countercurrent, or if the first stage is countercurrent, the second stage can be cocurrent or countercurrent.

[0271] The following may be advantages of the embodiments of this technology: TLE alone or after the last reactor can help to recover more heat. Additional cooling section as non-catalytic section at the end of each stage can also help to recover heat for HP / VHP steam generation.

[0272] Adding more catalyst cooling sections would improve the reactor's performance to produce more ethylene and AA and less undesirable CO / CO2. This could help control the reaction temperature. The first cooling section of the reactor could consume most of the oxygen, and the next section of the reactor could consume the remaining oxygen while maintaining good selectivity to the desired products.

[0273] By limiting the salt temperature rise to about 5°C, the overall performance of the reactor can be improved in terms of producing more desirable products. A higher salt temperature rise in each cooling section generally reduces the overall HTC of the molten salt side and means less molten salt circulation resulting in insufficient heat removal from the reaction inside the tube.

[0274] Smaller tubes give better reactor performance in terms of the desired product. This improves the HTC inside the tube (tube side) and therefore improves (increases) the heat removal from inside the tube.

[0275] Adding additional stages (additional reactors) to the ODH reactor system to get a two-stage or three-stage system (or an n-stage system where n=3+) would help split the oxygen between the stages and reduce the dilution requirements in the reactor system (for the first stage), which would improve the overall plant efficiency. Less dilution steam means less energy consumption by the ODH plant. Energy is required for the generation of dilution steam. Downstream, the steam water in the reactor system effluent is condensed (along with AA) in the AA unit. This means energy consumed for the condensation of water from the reactor effluent and for the AA unit.

[0276] Water quenching can be used as an effective technique to cool the reactor effluent between stages before oxygen is added. A HEX quench or additional non-catalytic salt quench section at the end of each stage can be more effective than water quenching due to heat recovery using molten salt or HEX quenching. This additional heat recovery compared to water quenching will improve the overall plant performance in terms of energy and CO2 intensity.

[0277] Although several implementations have been described, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure.

Claims

1. A method for operating an oxidative dehydrogenation (ODH) reactor system, To provide a feed comprising ethane, oxygen, and a diluent containing water, to obtain a reaction mixture that flows through the tube side of an ODH reactor, which is a multitubular reactor having a tube side and a shell side, wherein the ODH reactor comprises a first cooling section and a second cooling section, Dehydrogenation of ethane to ethylene in the reaction mixture via the ODH catalyst on the tube side, The first coolant is flowed through the shell side within the first cooling section, thereby maintaining the reaction mixture within the first cooling section at a first temperature. The method involves flowing a second coolant through the shell side within the second cooling section, thereby maintaining the reaction mixture within the second cooling section at a second temperature, wherein the first temperature is lower than the second temperature. Maintaining the temperature rise of the first coolant passing through the first cooling section below a first threshold, Maintaining the temperature rise of the second coolant passing through the second cooling section below a second threshold, Methods that include...

2. The method according to claim 1, wherein the first temperature is in the range of 300°C to 450°C, the second temperature is in the range of 350°C to 500°C, the first threshold is in the range of 2°C to 8°C, the second threshold is in the range of 2°C to 8°C, the first coolant and the second coolant each contain a molten salt, and the diluent contains steam.

3. Discharging effluent from the ODH reactor, wherein the effluent comprises ethylene, acetic acid, water, carbon dioxide, and carbon monoxide, and the ODH reactor is equipped with a flow barrier on the shell side that separates the first cooling section and the second cooling section so that the first coolant and the second coolant do not come into contact on the shell side. Heating water with at least one of the first coolant discharged from the ODH reactor, the second coolant discharged from the ODH reactor, or the effluent discharged from the ODH reactor, and optionally vaporizing the water to generate steam from the water. The method according to claim 1, including, Moreover, depending on the circumstances, The steam is passed through the tubes of the heat exchanger, and the steam is heated by the first coolant or the second coolant, or both, flowing on the shell side, thereby superheating the steam, wherein the water includes boiler feedwater, and the superheating is performed. The superheated steam is discharged from the heat exchanger, The method according to claim 1, further comprising:

4. The method of discharging the effluent, comprising discharging effluent from the ODH reactor, wherein the effluent comprises ethylene, acetic acid, water, carbon dioxide, and carbon monoxide, the second cooling section is located operationally downstream of the first cooling section in the flow direction of the reaction mixture, and the second cooling section is separated from the first cooling section by the shell-side flow barrier.

5. The method involves flowing a third coolant through the shell side within the third cooling section of the ODH reactor, thereby maintaining the reaction mixture on the tube side within the third cooling section at a third temperature, wherein the third temperature is lower than the second temperature, the third cooling section is operationally downstream of the second cooling section in the flow direction of the reaction mixture, and is separated from the second cooling section by the second flow barrier on the shell side. Heating water with at least one of the first coolant discharged from the ODH reactor, the second coolant discharged from the ODH reactor, the third coolant discharged from the ODH reactor, or the effluent discharged from the ODH reactor, The method according to claim 4, which includes, The method according to claim 4, wherein, in some cases, the tube side within the third cooling section does not contain a catalyst and the water is not heated by the effluent.

6. A method for operating an oxidative dehydrogenation (ODH) reactor system, To provide a feed containing ethane and oxygen into the tubes of an ODH reactor, wherein the tubes contain an ODH catalyst placed therein, and the feed contains water as a diluent, thereby keeping the feed outside the flammability limit. Dehydrogenation of ethane to ethylene in a tube via the ODH catalyst in the presence of oxygen in the reaction mixture, wherein the ODH reactor comprises a multi-tube fixed-bed reactor having a tube side and a shell side containing the tube for the flow of the reaction mixture, and the ODH reactor comprises a first cooling section in the flow direction of the reaction mixture and a second cooling section downstream of the operation of the first cooling section, The ODH catalyst is cooled to a first temperature in the first cooling section via a first coolant flowing through the shell side in the first cooling section, and to a second temperature in the second cooling section via a second coolant flowing through the shell side in the second cooling section, wherein the first temperature is lower than the second temperature. Maintaining the temperature rise of the first coolant passing through the first cooling section below a first threshold, Maintaining the temperature rise of the second coolant passing through the second cooling section below a second threshold, Methods that include...

7. (a) The first cooling section and the second cooling section are separated by the shell-side flow barrier, the temperature of the first is in the range of 300°C to 450°C, the temperature of the second is in the range of 350°C to 500°C, the threshold of the first cooling section is in the range of 2°C to 8°C, the threshold of the second cooling section is in the range of 2°C to 8°C, and the water in the feed contains steam or, (b) Specifying that the first temperature is lower than the second temperature in order that the method promotes the dehydrogenation of ethane to ethylene more than the reaction in the reaction mixture that gives carbon dioxide and the reaction in the reaction mixture that gives carbon monoxide, thereby increasing ethylene selectivity, To promote the dehydrogenation of ethane to ethylene more than the reaction that produces carbon dioxide and the reaction that produces carbon monoxide, thereby increasing ethylene selectivity, the temperature rise of the first coolant is kept below a first threshold, and the temperature rise of the second coolant is kept below a second threshold. Includes or, (c) The reaction between ethane and oxygen in the reaction mixture includes a first total reaction involving the dehydrogenation of ethane to ethylene, a second total reaction giving acetic acid, a third total reaction giving carbon monoxide, and a fourth total reaction giving carbon dioxide, The method according to claim 6, wherein it is any one of the following.

8. The reaction between the ethane and the oxygen in the reaction mixture comprises a first total reaction including the dehydrogenation of the ethane to ethylene, a second total reaction giving acetic acid, a third total reaction giving carbon monoxide, and a fourth total reaction giving carbon dioxide. The method according to claim 7, wherein the method specifies an increase in ethylene selectivity by promoting the first total reaction more than the third total reaction and the fourth total reaction, wherein the first total reaction consumes less stoichiometric amount of oxygen than each of the third total reaction and the fourth total reaction.

9. The method according to claim 8, comprising discharging the reaction mixture from the ODH reactor as an effluent, wherein the effluent contains ethylene, acetic acid, water, carbon dioxide, carbon monoxide, and unreacted ethane, and discharging in response to maintaining the first temperature lower than the second temperature specifying an increase in ethylene selectivity, thereby increasing the ethylene selectivity and thereby reducing the amount of oxygen in the feed and reducing the amount of water in the feed.

10. Heating boiler feedwater with at least one of the first coolant, the second coolant, or the flotation, wherein maintaining the temperature rise of the first coolant below a first threshold and maintaining the temperature rise of the second coolant below a second threshold specifies an increase in ethylene selectivity, thereby increasing the ethylene selectivity and reducing the amount of oxygen in the feed and thus reducing the amount of water in the feed, The method according to claim 9, wherein, in some cases, heating the boiler feedwater vaporizes the boiler feedwater and thereby generates steam from the boiler feedwater.

11. This includes specifying an increase in ethylene selectivity and configuring the ODH reactor so that the tube is less than or equal to a specified diameter in response to the increase in ethylene selectivity, The method according to claim 8, wherein the specified diameter is 1.25 inches, the linear velocity of the reaction mixture in the tube is in the range of 150 centimeters / second (cm / s) to 500 cm / s, and the space velocity of the gas per hour of the reaction mixture passing through the ODH catalyst in the tube is in the range of 1,500 hours⁻¹ (hr⁻¹) to 10,000 hr⁻¹.

12. An oxidative dehydrogenation (ODH) reactor system, An ODH reactor comprising a first cooling section and a second cooling section separated on the shell side by a flow barrier, wherein the ODH reactor is A tube side having an ODH catalyst is configured to receive a feed containing ethane, oxygen, and a diluent including water, dehydrogenate the ethane to ethylene in the reaction mixture, and discharge an effluent containing ethylene, acetic acid, water, carbon dioxide, carbon monoxide, and unreacted ethane. The shell side is configured to receive a first coolant in the first cooling section and maintain the temperature of the ODH catalyst in the first cooling section at a first temperature, and to receive a second coolant in the second cooling section and maintain the temperature of the ODH catalyst in the second cooling section at a second temperature, wherein the first temperature is lower than the second temperature, and the second cooling section is located downstream of the first cooling section in the flow direction of the reaction mixture. A multi-tube fixed-bed reactor, an ODH reactor, A first coolant supply system comprising a pump configured to supply the first coolant to the first cooling section and to maintain the temperature rise of the first coolant passing through the first cooling section below a first threshold, A second coolant supply system comprising a pump configured to supply the second coolant to the second cooling section and to maintain the temperature rise of the second coolant passing through the second cooling section below a second threshold, A first heat exchanger configured to heat the first water with the first coolant for the generation of steam from the first water, A system equipped with these features.

13. (a) The first temperature is in the range of 300°C to 450°C, the second temperature is in the range of 350°C to 500°C, the first threshold is in the range of 2°C to 8°C, the second threshold is in the range of 2°C to 8°C, the steam in the feed acts as a diluent to keep the feed outside the flammability limit, and the ODH reactor is configured to produce acetic acid in the reaction mixture on the tube side, or (b) The steam generation includes the first heat exchanger configured to vaporize the first water into steam, and optionally includes a steam drum for receiving the steam from the first heat exchanger and discharging the steam, (c) The first heat exchanger for heating the first water includes a first heat exchanger configured to preheat the first water in a steam drum to vaporize the first water, wherein the first water includes boiler feedwater. The system according to claim 12, which is any of the following.

14. The ODH reactor is configured to provide a second heat exchanger for heating the second water with the second coolant discharged from the second cooling section for the generation of steam from the second water, and the dehydrogenation of ethane to ethylene comprises a first total reaction of ethane and oxygen on the tube side, and the ODH reactor comprises a second total reaction of acetic acid, a third total reaction of carbon monoxide, and a fourth total reaction of carbon dioxide. The system according to claim 12, wherein, in some cases, a third heat exchanger is provided for heating the third water with the effluent for the generation of steam of the third water, and the first coolant and the second coolant each contain a molten salt.

15. The system according to claim 12, wherein the second cooling section is operationally downstream of the first cooling section with respect to the flow of the reaction mixture, and the ODH reactor includes a third cooling section operationally downstream of the second cooling section with respect to the flow of the reaction mixture for receiving a third coolant into the shell, and the third cooling section is separated from the second cooling section by a second flow barrier on the shell side.

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