Oxidative dehydrogenation (ODH) series reactor system with inter-stage quenching and oxygen injection

Abstract

A method and a system for oxidative dehydrogenation (ODH) are provided. An exemplary ODH reactor system includes an ODH reactor to receive a feed including ethane and oxygen (O2) and dehydrogenate ethane to ethylene. An effluent from the ODH reactor is passed over a first end of a heat pipe to a quench tower. The heat pipe heats boiler feedwater (BFW) with the effluent to generate steam from the BFW, to heat steam discharged from the steam drum, and to heat an overhead stream from the quench tower. An overhead stream from the quench tower is fed to a second ODH reactor. The quench tower includes a column vessel to receive BFW from the steam drum to quench the effluent, an oxygen (O2) stream introduced below a liquid level in the quench tower, and discharges liquid including water and acetic acid.

Description

[0001] OXIDATIVE DEHYDROGENATION (ODH) SERIES REACTOR SYSTEM WITH INTER-STAGE QUENCHING AND OXYGEN INJECTION

[0002] TECHNICAL FIELD

[0003] This disclosure relates to an oxidative dehydrogenation (ODH) reactor system with ODH reactors operationally in series.

[0004] BACKGROUND ART

[0005] Catalytic oxidative dehydrogenation of alkanes into corresponding alkenes is an alternative to steam cracking. In contrast to steam cracking, oxidative dehydrogenation (ODH) may operate at lower temperature and generally does not produce coke. For ethylene production, ODH can provide a greater yield for ethylene than does steam cracking. The ODH may be performed in a reactor vessel having catalyst for the conversion of an alkane to a corresponding alkene. Acetic acid as a byproduct may be generated in the conversion of the lower alkanes (e.g., ethane) into the corresponding alkenes (e.g., ethylene). The product alkene and byproduct acetic acid may each be recovered from the ODH reactor effluent.

[0006] SUMMARY OF INVENTION

[0007] An embodiment described herein provides a method of operating an oxidative dehydrogenation (ODH) reactor system. The method includes providing a first feed including ethane and oxygen (O2) to a first ODH reactor, dehydrogenating ethane to ethylene via ODH catalyst in the first ODH reactor, thereby forming water and acetic acid. An effluent is discharged from the first ODH reactor across a first end portion of a heat pipe to a quench tower, the effluent including ethane, ethylene, water, acetic acid, carbon dioxide, and carbon monoxide. The boiler feed water (BFW) is flowed across the heat pipe to heat the BFWwith the effluent to generate steam from the BFW in a steam drum, and discharging the steam from an upper portion of the steam drum across the heat pipe to heat the steam with the effluent. BFW discharged from a bottom portion of the steam drum is introduced as quench water to the quench tower to quench the effluent that enters the quench tower, thereby reducing temperature of the effluent. Oxygen (O2) is introduced to a lower portion of the quench tower below a liquid level in the quench tower. A second ODH reactor an overhead stream from the quench tower is discharged across the heat pipe to heat the overhead stream with the effluent, the overhead stream including ethane, ethylene, oxygen (O2), water, acetic acid, carbon dioxide, and carbon monoxide.

[0008] Another embodiment described herein provides an oxidative dehydrogenation (ODH) reactor system. The ODH reactor system includes a first ODH reactor to receive a first feed including ethane and oxygen (O2), dehydrogenate ethane to ethylene via first ODH catalyst in the first ODH reactor, and discharge a first effluent through a first effluent conduit across a first end portion of a heat pipe to a quench tower, the first effluent including ethane, ethylene, water, acetic acid, carbon dioxide, and carbon monoxide. The ODH reactor system includes the heat pipe to heat boiler feedwater (BFW) with the effluent for generation of steam from the BFW in a steam drum, heat steam discharged from the steam drum with the effluent, and heat an overhead stream from the quench tower with the effluent, wherein the overhead stream is a second feed to a second ODH reactor, the overhead stream including ethane, ethylene, oxygen (O2), water, acetic acid, carbon dioxide, and carbon monoxide. The ODH reactor system includes the quench tower including a column vessel to receive BFW from a bottom portion of the steam drum to quench the first effluent, receive an oxygen (O2) stream introduced below a liquid level in the quench tower, and discharge liquid including water and acetic acid from a bottom portion of the quench tower through a bottoms discharge conduit.

[0009] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.

[0010] BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a diagram of an ODH reactor system having a first ODH reactor and a second ODH reactor disposed operationally in series.

[0012] Figure 2 is a diagram of the heat pipe in the ODH reactor system of Figure 1.

[0013] Figure 3 is a block flow diagram of a method 300 operating an ODH reactor system.

[0014] Like reference numbers and designations in the various drawings indicate like elements.

[0015] DESCRIPTION OF EMBODIMENTS

[0016] Some aspects of the present disclosure are directed to the staged oxygen injection between two oxidative dehydrogenation (ODH) reactors in series. The product effluent from the first ODH reactor is cooled for the inter-stage introduction of the oxygen. Quenching of the first reactor effluent, and the oxygen injection, may be implemented in the same quench tower. Further, a heat pipe (as an indirect heat exchanger) may be utilized to cool the first reactor effluent prior to entry of the first reactor effluent into the quench tower.

[0017] A benefit of the inter-stage addition of oxygen can be that less oxygen is included in the first feed to the first ODH reactor, thereby advantageously avoiding need for diluent in the first feed in certain implementations. Further, the overhead discharged from the quench tower as second feed to the second ODH reactor includes water, and therefore there may be no need for direct supply of diluent (e.g., steam) for feed dilution in implementations.

[0018] Figure 1 is an ODH reactor system 100 having a first ODH reactor 102 and a second ODH reactor 104 disposed operationally in series. The first ODH reactor 102 may be labeled as a first reactor stage or first stage of the ODH reactor system 100. The second ODH reactor 104 may be labeled as a second reactor stage or second stage of the ODH reactor system 100. Equipment disposed operationally between the first ODH reactor 102 and the second ODH reactor 104 facilitates the inter-stage addition of oxygen (O2) 106. An advantage may be that due to this intermediate addition of oxygen 106 between the first ODH reactor 102 and the second ODH reactor 104, less oxygen (O2) is included in the first feed 108 to the first ODH reactor 102. Therefore, the amount of diluent in the first feed 108 to give the first feed 108 outside of flammability limits may be beneficially reduced. Advantageously, this may lead to reduction of size of the first ODH reactor 102.

[0019] In implementations, a majority of oxygen gas in the first feed 108 introduced to the first ODH reactor 102 may typically be consumed in the ODH reaction in the first ODH reactor 102. Therefore, the inter-stage addition of oxygen 106 (between the first ODH reactor 102 and the second ODH reactor 104) may provide oxygen for the ethane dehydrogenation to proceed adequately in the second ODH reactor 104.

[0020] For the inter-stage (intermediate) addition of oxygen 106 gas, the first effluent 110 from the first ODH reactor is cooled so to avoid auto-ignition with the increased amount of oxygen added inter-stage. The cooling of the first effluent 110 can be by a heat pipe 112 (heat-pipe heat exchanger) and with a quench tower 114. The first ODH reactor 102 and the second ODH reactor 104 may each dehydrogenate ethane to ethylene via an ODH catalyst in presence of oxygen. The dehydrogenation of ethane to ethylene may be a reaction of ethane with oxygen via the ODH catalyst to give the ethylene. The ODH reaction of ethane and oxygen to ethylene and water is generally exothermic. For operational stability, the ODH reaction may be performed with the feed and reaction mixture compositions above the ethane upper flammable limit (UFL).

[0021] The ODH reactors 102, 104 may each be a multi-tubular fixed-bed reactor having a fixed bed of ODH catalyst, or a fluidized bed reactor that operates with a fluidized bed of ODH catalyst. Other reactor types are applicable.

[0022] For a fluidized bed reactor, the reactor vessel jacket for receiving coolant 116 may be labeled as a utility side of the reactor. The main inside volume of the reactor having the fluidized bed may be labeled as the process side of the reactor. For the ODH reactors 102, 104 as a fluidized bed reactor, the coolant 116 may flow through the reactor vessel jacket to remove the heat of reaction.

[0023] The ODH reactors 102, 104 may each be a multi-tubular fixed-bed reactor having ODH catalyst on the tube side for the ODH reaction, and in which coolant 116 (e.g., molten salt or other heat-transfer fluid) flows on the shell side and / or a reactor vessel jacket to remove the heat of reaction from the tube side. For the reactors 102, 104 as a multi-tubular reactor, the first feed 108 is introduced to the first ODH reactor to give a reaction mixture flowing on the tube side of the ODH reactor.

[0024] The first feed 108 (process feed) to the first ODH reactor 102 may include ethane and oxygen conveyed in a conduit to the ODH reactor 102. The feed 108 may also include diluent to place the feed outside of flammability limits. The diluent can be, for example, nitrogen gas (N2), carbon dioxide gas (CO2), water (steam), helium, argon, or methane, or any combinations thereof. In implementations, steam or vaporized water can be an attractive diluent, for example, due to the relative simplicity of the separation of the water from the ODH reactor effluent. If the diluent in the feed 108 includes water, the water in the first effluent 110 may include both unreacted diluent water and water generated in the ODH reaction in the ODH reactor.

[0025] Components in addition to ethylene that form in the ODH reactors 102, 104 may include acetic acid, carbon dioxide, carbon monoxide, and water. Thus, an ODH plant having the ODH reactor system 100 may produce ethylene as product and acetic acid as coproduct. Carbon monoxide and carbon dioxide may undesirably form in the ODH reactors 102, 104 and discharge in the reactor effluent 110, 118 with the ethylene and acetic acid.

[0026] The ODH reactors 102, 104 may generate ethylene (C2H4) as the main product and acetic acid (CH3COOH) as a value-added coproduct. The ODH reactors 102, 104 may generate carbon monoxide (CO), carbon dioxide (CO2), and water (H2O). The reactions or reaction mechanisms in the ODH reactors 102, 104 characterized as reactions of ethane (C2H6) and oxygen (O2) can be explained at least in part as follows:

[0027] C2H6 + 0.5 O2 C2H4 + H2O

[0028] C2H6 + 1.5 O2 CH3COOH + H2O

[0029] C2H6 + 2.5 O2 2 CO + 3 H2O C2H6 + 3.5 O2 2 CO2 + 3 H2O

[0030] The first effluent 110 from the first ODH reactor 102 and the second effluent 118 (product effluent) from the second ODH reactor 104 may each include ethylene, acetic acid, carbon dioxide, carbon monoxide, water, and unreacted ethane. The first effluent 110 as discharged at the first ODH reactor 102 and the second effluent 118 as discharged at the second ODH reactor 104 may be, for example, at a temperature in the range of 300°C to 550°C, or in the range of 340°C to 370°C for the first effluent 110, or in the range of 400°C to 500°C for the second effluent 118.

[0031] The first effluent 110 flows a cross a first end portion (first longitudinal end portion) of the heat pipe 112 in route to the quench tower 114. The first end portion is the hot end portion having the hot end 120 of the heat pipe 112. The first effluent 110 upstream of the heat pipe 112 may be labeled as hot first effluent 110. The first effluent 110 downstream of the heat pipe 112 may be labeled as cooled first effluent 110. Indeed, the heat pipe 112 cools the first effluent 110, for example, to a temperature in the range of 80°C to 220°C or in the range of 180°C to 220°C. The opposite longitudinal end portion is the second end portion (cold end portion having the cold end 122) of the heat pipe 112. In cooling the first effluent 110, heat from the first effluent 110 is utilized by the heat pipe 112 to heat other streams. Thus, heat transfer occurs from the first effluent 110 via the heat pipe 112 to the other streams that flow across the heat pipe 112. Typically, a heat pipe or heat tube includes a sealed tube (metallic) containing a working fluid and an internal capillary to transport the condensed working fluid from the end of the heat pipe in the cold section to the end of the heat pipe in the hot section. In operation, the working fluid in the heat tube is boiled or evaporated in the hot section taking heat from the hot fluid. The resulting vapor moves up the heat tube to the cold section. The vapor then condenses in the cold section giving up heat to the medium passing across the cold section. The resulting condensed liquid is transported through the capillary or wick in the tube to the hot section by gravity and capillary forces where it again evaporates.

[0032] The heat pipe 112 is depicted exaggerated enlarged in size for clarity. Moreover, the heat pipe may include multiple heat pipes or heat tubes. See, for example, Figure 2.

[0033] The first effluent 110 after being cooled by the heat pipe 112 flows into the quench tower 114. The quench tower 114 is a column vessel (e.g., having a vertical orientation). Quench water 124 is added to the quench tower 114 to quench the first effluent 110 in the quench tower 114, thereby further reducing the temperature of the first effluent 110 and thus condensing water and acetic acid from the first effluent 110 in the quench tower 114.

[0034] Liquid 126 including condensed water and condensed acetic acid may discharge from a bottom portion of the quench tower 114 through a bottoms discharge conduit. The liquid level 128 (the height of the liquid level 128) may be controlled, for example, by controlling flow rate of the discharged liquid 126 via a control valve 130 (e.g., flow control valve) disposed along the bottoms discharge conduit. In implementations, for the inter-stage addition of oxygen (O2) gas 106, the O2 gas 106 is introduced into the quench tower 114 below the liquid level 128 in the quench tower 114. The liquid 126 discharged from the bottom portion of the quench tower 114 may be processed to recover acetic acid as coproduct.

[0035] The quench water 124 is typically introduced into an upper portion of the quench tower 114 above the liquid level 128 in the quench tower 114. In implementations, the quench tower 114 may have spray nozzles and / or a distributor to facilitate the addition of the quench water 124 and promote contact of the quench water 124 with the entering first effluent 110 in the quench tower 114. The quench tower 114 may also include random packing, structured packing, or trays, or any combinations thereof, and the like to promote contact of the quench water 124 with the first effluent 110 components to cool the first effluent 110 components in the quench tower 114.

[0036] An overhead stream discharges overhead from the quench tower 114 as second feed 132 to the second ODH reactor 104. Beneficially, this overhead stream will generally include unreacted ethane from the first effluent 110, as well as the O2 106 added to the quench tower 114. Thus, the ethane and O2 106 in the overhead stream as the second feed 132 can provide feed components for the reaction of oxygen with ethane in the dehydrogenation of ethane into ethylene via ODH catalyst in the second reactor 104. Further, the overhead stream includes water that can act as a diluent for the second feed 132. The overhead stream (that is the second feed 132) may include ethane, ethylene, oxygen (O2), water, acetic acid, carbon dioxide, and carbon monoxide.

[0037] In implementations, this overhead stream as discharged from the quench tower 114 may be saturated in water and / or acetic acid. The temperature of the overhead stream as discharged from the quench tower 114 may be, for example, in the range of 60°C to 130°C, or in the range of 100°C to 130°C.

[0038] In route to the second ODH reactor 104, the second feed 132 (overhead stream from the quench tower 114) flows across the heat pipe 112 that heats the second feed 132 with the first effluent 110. The second feed 132 after being heated via the heat pipe 112 is not saturated with water and / or acetic acid. The temperature of the second feed 132 after being heated with the heat pipe 112 may be, for example, in the range of 150°C to 200°C, or in the range of 180°C to 200°C.

[0039] The flow rate of the second feed 132 can be determined by the amount of water / acetic acid that is removed from the first effluent 110 in the quench tower, and by the amount of oxygen added. The first effluent 110 will be saturated with water and acetic acid. Further, depending on the amount of oxygen that is added at the interstage, we may need additional steam or different diluent e.g. N2 / CH4 to stay outside the flammability limits.

[0040] The volume ratio of acetic acid to water in the overhead stream (second feed 132) can be increased to reduce formation of acetic acid in the second ODH reactor and increase ethane conversion in the second ODH reactor 104. See, for instance, the Example below. The volume ratio of acetic acid to water in the second feed 132 may be increased by 0.1 to 2 vol%. The temperature and flow rate of the quench water 124 will determine the concentration of acetic acid in the second feed 132. The lower the amount of quench water 124 fed into reactor 2, the lower the amount of the acetic acid formed. More acetic acid in the second feed 132 can be used to reach acetic acid neutral conditions. Again, the volume ratio of acetic acid to water in the overhead stream (second feed 132) can be increased, wherein this volume ratio as increased reduces formation of acetic acid in the second ODH reactor and increases ethane conversion in the second ODH reactor.

[0041] Boiler feedwater (BFW) 134 may flow across the heat pipe 112 so that the BFW 134 is heated with the heat removed from the first effluent 110 via the heat pipe 112 to generate steam 136 from the BFW 134 in a steam drum 138. The BFW 134 may be treated liquid water including demineralized water and can include steam condensate, and the like. The BFW 134 may be a combination of fresh BFW (e.g., demineralized water plus treatment additives) and recycled steam condensate. Motive force for flow of the BFW 134 across the heat pipe 112 and to the steam drum 138 may be provided, for example, by an upstream BFW pump (e.g., a centrifugal pump). The temperature of the feed BFW 134 to the heat pipe 112 may be, for example, in the range of 80°C to 220°C or in the range of 110°C to 120°C. The temperature of the BFW 134 as heated by the heat pipe 112 and entering the steam drum 134 may be, for example, in the range of 100°C to 270°C or in the range of 200°C to 250°C.

[0042] The pressure in the steam drum 138 and thus the pressure of the steam 136 discharged from an upper portion of the steam drum 138 may be driven by the temperature of the BFW 134 as heated by the heat pipe 112. The pressure in the steam drum 138 may be the same as the pressure of the heated BFW 134 determined by the BFW pump (not shown in the diagram). The steam drum 138 is a reservoir that initiates phase separation between the steam and the hot water due to density difference. The pressure in the steam drum 138 (and pressure of the steam 136 as discharged) may be, for example, in the range of 210 pounds per square inch gauge (psig) to 562 psig. The steam drum 138 is a phase separator that separates steam from the hot water by the density difference. The pressure in the steam drum 138 may be the same as the pressure of the heated stream 134.

[0043] The steam 136 as discharged from the steam drum 138 may generally be saturated steam. The steam 136 may flow across the heat pipe 122 that heats (superheats) the steam 136 with the first effluent 110 to give the steam 136 as superheated steam. The temperature of the steam 136 can be controlled by controlling the residence time of the steam 136 in the chamber or that section, for example, by controlling the flow of the steam 136 with a control valve.

[0044] The flow rate of the BFW 134 may be regulated (adjusted), such as via a control valve 140 (e.g., flow control valve), to control the temperature of the second feed 132 as heated by the heat pipe 112 and fed to the second ODH reactor 104. Controlling the flow rate of the BFW 134 will determine how much of heat remaining after the third section of the heat pipe 122 needs to be removed. Generally, this is controlled to achieve a heat balance between sections 3 and 4 of the heat pipe 122. This also controls and how much is removed by the BFW 134 flow and the overhead stream 132 of the quench tower.

[0045] In the illustrated implementation, the BFW 134 flows across the cold end portion (having the cold end 122) of the heat pipe 112. In alternate embodiments, the overhead stream (second feed 132) from the quench tower 114 is routed across the cold end portion (having the cold end 122) of the heat pipe 112. Generally, the coolest stream flows across the cold end of the heat pipe, warmer streams flow across the heat pipe between the cold end in the hot end, and the first effluent 110 flows across the hot in to vaporize the heat pipe liquidBoiler feedwater may discharge from a bottom portion of the steam drum 138 as the quench water 124 to the quench tower 114. The pressure in the steam drum 138 may provide the motive force for flow of the BFW from the bottom of the steam drum 138 through a quench-water conduit to the quench tower 114. The flow rate of this quench water 124 may be controlled, such as via a control valve disposed along the quench- water conduit. Control of this flow may facilitate control of the BFW liquid level in the steam drum 138.

[0046] The ODH reactor system 100 may include a control system 142 having a processor 144 and memory 146 storing code (logic, instructions) executed by the processor 144 to direct operation of the ODH reactor system 100 to provide for and facilitate control of flow rates, pressures, control valves, and so on. The processor 144 may be one or more processors and each processor may have one or more cores. These hardware processor(s) may include a microprocessor, a central processing unit (CPU), a graphic processing unit (GPU), a controller card, or other circuitry. The memory 146 may include volatile memory (for example, cache and random access memory (RAM)), nonvolatile memory (for example, hard drive, solid-state drive, and read-only memory (ROM)), and firmware. The control system 142 may include a desktop computer, laptop computer, computer server, programmable logic controller (PLC), distributed computing system (DSC), controllers, actuators, control cards, and a user interface. The control system 142 may be disposed remotely in a control room, and / or disposed in the field such as with control modules and apparatuses distributed in the field. The control system 142 may receive user input or remote-computer input that specifies the set points of control devices or other control components in the ODH reactor system 100. Determinations by the control system 142 may be based at least in part on values of operating conditions of the ODH reactor system 100 received via feedback from (e.g., from sensors in) the ODH reactor system 100.

[0047] Some implementations may include a control room that can be a center of activity, facilitating monitoring and control of the process or facility. The control room may contain a human machine interface (HMI), which is a computer, for example, that runs specialized software to provide a user-interface for the control system. The HMI may vary by vendor and present the user with a graphical version of the remote process. There may be multiple HMI consoles or workstations, with varying degrees of access to data. The control system 142 may also or instead employ local control (e.g., distributed controllers, local control panels, etc.) distributed in the system 100.

[0048] In the ODH reactor system 100, ODH catalyst (e.g., as a fixed bed of catalyst) may be disposed inside the tubes of the ODH reactors 102, 104 as a multi-tubular reactor, or as mentioned, be a fluidized bed of catalyst in operation in the ODH reactors 102, 104 as a fluidized bed reactor. The term “ODH catalyst” as used herein may be catalyst known for ODH of ethane. The ODH catalyst may give an ODH reaction that dehydrogenates ethane to ethylene and in which acetic acid as a byproduct may be formed. A low-temperature ODH catalyst may be beneficial. One non-limiting example of an ODH catalyst that may be utilized in an ODH reactor is a low-temperature ODH catalyst that includes molybdenum (Mo), vanadium (V), tellurium (Te), niobium (Nb), and oxygen (O), wherein the molar ratio of molybdenum to vanadium is from 1 :0.12 to 1:0.49, the molar ratio of molybdenum to tellurium is from 1:0.01 to 1:0.30, the molar ratio of molybdenum to niobium is from 1 :0.01 to 1:0.30, and oxygen is present at least in an amount to satisfy the valency of any present metal elements. The molar ratios of molybdenum, vanadium, tellurium, niobium can be determined by inductively coupled plasma mass spectrometry (ICP-MS). The catalyst may be labeled as low temperature ODH catalyst in providing for the ODH reaction at less than 550°C, less than 500°C, less than 450°C, less than 425°C, less than 400°C, or less than 375°C, or in the ranges, for example, of 300°C to 550°C, 300°C to 500°C, 300°C to 450°C, 275°C to 425°C, 275°C to 550°C, 250°C to 550°C, or 250°C to 400°C, and the like.

[0049] The ODH reactors 102, 104 are typically each a cylindrical vessel having elliptical or semi-elliptical heads. The vessel (metal, such as stainless steel) may have a vertical orientation (as depicted) or a horizontal orientation. The reactor vessel may be a pressure vessel designed and configured (e.g., with adequate wall thickness) to be subjected to an internal pressure up to a specified pressure (design pressure) greater than ambient pressure (atmospheric pressure). A pressure vessel may be rated to hold a fluid up to the design pressure. In operation, the operating pressure in a pressure vessel may generally be maintained less than the design pressure. A pressure vessel may be constructed per a formal standard or code, such as the American Society of Mechanical Engineers (ASME) Boiler & Pressure Vessel Code (BPVC) or the European Union (EU) Pressure Equipment Directive (PED).

[0050] The ODH reactors 102, 104 if a multi-tubular fixed-bed reactor may have a shell and a tube bundle, which may be similar to a shell-and-tube heat exchanger, except that the tubes have a fixed bed of catalyst. The tube bundle is multiple tubes generally aligned in parallel. The number of tubes in the tube bundle of the ODH reactors 102, 104 if multi-tubular fixed-bed reactor can range in the thousands, such as 10,000 to 50,000, e.g., 30,000 tubes as a particular non-limiting example.

[0051] As indicated, the ODH reactors 102, 104 in embodiments as a multi-tubular reactor include a tube side and a shell side. The tube side may be the process side (for conversion in a flowing reaction mixture of process feed into product). The shell side may be the utility side (for flow of a coolant 116). The shell side can be similar in effect to a vessel jacket, but may be similar or analogous to a shell side of a shell-and-tube heat exchanger.

[0052] As discussed, the process feed (feed 108 and second feed 132) may enter the respective reactor vessel through a vessel inlet (e.g., inlet nozzle) to the tube side. The process feed can enter a bottom portion of the reactor, as depicted for the reactor 102, or enter a top portion of the reactor, as depicted for the reactor 104. The process product effluent (first effluent 110 and second effluent 118) may discharge from the respective reactor vessel through a vessel outlet (e.g., outlet nozzle) from the tube side. The effluent discharge is generally at the longitudinal end portion opposite the longitudinal end the feed is introduced. The effluent can discharge from a top portion of the reactor, as depicted for the reactor 102, or enter a bottom portion of the reactor, as depicted for the reactor 104.

[0053] A coolant 116 (e.g., molten salt, oil, etc.) may enter the reactor vessel (e.g., to the shell side for a multi-tubular reactor or to a vessel jacket for a fluidized bed reactor) through a vessel inlet (e.g., inlet nozzle) to flow through the utility side (shell side or vessel jacket) around the tubes or fluidized bed to remove the heat of reaction. The coolant 116 provided to the reactors 102, 104 and that enters the shell side or jacket may be labeled as coolant supply. Again, the coolant 116 may flow around the tubes for a multi-tubular reactor, or around the exterior of the fluidized bed for a fluidized bed reactor. Therefore, the coolant 116 may be subjected to heat exchange with the process reaction mixture and ODH catalyst on the process side (tube side or main inside reactor volume). The coolant 116 removes the heat of reaction of the ODH reaction. The shell side or jacket may include baffle(s) to generate more turbulent flow of the coolant 116 to improve (increase) heat transfer between the heat transfer fluid 116 and the tube side or process side.

[0054] The coolant 116 may discharge from the reactors 102, 104 from the shell side or jacket (utility side), such as through a vessel outlet (e.g., outlet nozzle). The coolant 116 that discharges from the reactors 102, 104 from the shell side or jacket may be labeled as coolant return sent (as return) to a coolant supply system. The composition of the coolant 116 that discharges from the reactors 102, 104 may be the same as the composition of the coolant 116 supplied to the reactors 102, 104. The discharged coolant 116 may have the same composition but a different (increased) temperature than the supplied coolant 116 due to the heat exchange with the reaction mixture (and ODH catalyst) on the tube side or process side. The flow of the coolant 116 through the shell side or vessel jacket may be in a cocurrent flow direction (or counter current flow direction) with the flow of the reaction mixture on the tube side for a multi-tubular reactor or with the flow of the fluidized catalyst for a fluidized bed reactor.

[0055] As indicated, the ODH reaction is exothermic. The shell 102 via the coolant may maintain the reaction mixture and ODH catalyst on the process side (the tube side or fluidized bed) at a specified temperature (isotherm temperature). The temperature of the reaction mixture and / or ODH catalyst may be related to the catalyst 112 bed average temperature, catalyst-bed peak temperature, coolant temperature through the shell or jacket, and the like. In implementations, the coolant 116 can be maintained at a specified temperature to give desired temperatures for the reaction mixture and the ODH catalyst. The temperature of at least one of the coolant 116, the reaction mixture, or the ODH catalyst may be maintain at a specified temperature via flowing the coolant through the utility side (shell side or vessel jacket). For a multi-tubular fixed-bed reactor, heat transfer occurs from the process reaction mixture and ODH catalyst on the tube side through the tube wall (of each of the multiple tubes) to the coolant 116 flowing through the shell side.

[0056] The technique may include flowing the coolant 116 through the shell side or vessel jacket to maintain the reaction mixture (and ODH catalyst) on the process side at a specified temperature. Again, the technique may include maintaining temperature of at least one of the coolant 116, the reaction mixture, or the ODH catalyst at a specified temperature via flowing the coolant 116 through the utility side. The specified temperature may be, for example, in the ranges of 300°C to 550°C, 300°C to 500°C, 300°C to 475°C, 300°C to 450°C, 300°C to 425°C, 300°C to 400°C, 350°C to 500°C, 350°C to 450°C, 325°C to 425°C, 275°C to 425°C, or 250°C to 400°C, and the like. The temperature of the reaction mixture and / or ODH catalysts may be congruent with or related to catalyst-bed average temperature, catalyst-bed peak temperature, coolant temperature 116 through the utility side, coolant 116 as discharged, and the like. In some implementations, the coolant 116 temperature can be controlled at the aforementioned specified temperature ranges to give a desired temperature for the reaction mixture and / or the ODH catalyst.

[0057] The coolant 116 can be, for example, steam, water (including pressurized or supercritical water), oil, or molten salt, and so forth. Molten salt may be selected as the coolant due to relatively high stability of the molten salt and due to relatively high heat-transfer coefficient values provided by molten salt at the temperature (e.g., 300-500°C) of operation of the ODH reactor. Water (critical point is 374°C and 22,064 kPa) or very high-pressure steam (e.g., 1500 psig or greater) employed as the coolant 116 would give relatively high pressure on the shell side leading to thicker walls of the shell (vessel). The coolant 116 may be, for example, molten salt, or oil or other high- temperature heat transfer fluid. The molten salt can include, for example, potassium nitrate, sodium nitrate, potassium nitrite, and / or sodium nitrite. Examples include ASD molten salt available from Durferrit GmbH having headquarters in Mannheim, Germany, and HITEC® heat transfer medium available from Coastal Chemical Co., LLC having headquarters in Houston, Texas, USA, and the like. The HITEC heat transfer medium is a mixture of inorganic salts of potassium nitrate, sodium nitrite, and sodium nitrate. The oil or other high-temperature transfer fluid if utilized as coolant, for example, may be SYLTHERM® 800 (stabilized heat transfer fluid) or DOWTHERM® A (organic heat transfer fluid) available from The Dow Chemical Company, officially Dow Inc., having headquarters in Midland, Michigan, USA, or THERMINOL® VP-1 [mixture of diphenyl oxide (DPO) and biphenyl] or THERMINOL 75 (synthetic heat transfer fluid) available from Eastman Chemical Company having headquarters in Kingsport, Tennessee, USA, or SANTOLUBES® OS-750 or SANTOLUBES OS-124 available from Santolubes LLC having headquarters in Spartanburg, South Carolina, USA.

[0058] The second effluent 118 that discharges from the second ODH reactor 104 may be labeled as a product effluent in having ethylene to be recovered as product. The downstream processing of the second effluent 118 may include condensing the water and acetic acid in the second effluent 118 to remove the acetic acid and water from the second effluent 118. 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 downstream flash drum vessel or a quench tower vessel may facilitate separation of the liquid as condensed from the second effluent 118.

[0059] In implementations, the condensed water and the condensed acetic acid as a mixture from the ODH reactor effluent may be processed in an acetic acid unit (e.g., having an extractor column vessel, solvent recovery column vessel, and water stripper column vessel) to separate the co-product acetic acid and liquid water. In implementations, the water may be recycled for use in the ODH plant. For instance, the water discharging from the acetic acid unit may be recycled (as recycle water) for scrubbing process gas in the second effluent 118 processing and / or as water for the dilution steam in the ODH reactor feed preparation, and so on. After the condensed water and condensed acetic acid are removed from the second effluent 118, the remaining portion of the second effluent 118 as gas can includes ethylene, CO, CO2, and ethane. In examples, this gas may be scrubbed (e.g., with liquid water) in a scrubber column vessel to remove residual acetic acid vapor and residual water vapor from the gas. The gas may be subjected to separations to remove CO and CO2. The gas may be sent through a C2 splitter (ethane / ethylene splitter) (a distillation column vessel having distillation trays) to separate the ethane from the gas to give the product ethylene.

[0060] The second effluent 118 as discharged from the second ODH reactor 104 may be routed through one or both of two heat exchangers 148, 150 to recover heat from the second effluent 118 in route to the aforementioned downstream processing. The temperature of the second effluent 118 as discharged may be, for example, in the range of 300°C to 500°C commensurate with the operating temperature (e.g., 300°C to 500°C) of the second ODH reactor 104. Other temperature ranges are applicable, as indicated. The second effluent 118 may discharge from the second ODH reactor 104 through a second effluent discharge conduit. The heat exchangers 148,150 may be disposed along the second effluent discharge conduit.

[0061] The first heat exchanger 148 may be a steam-generation heat exchanger. In operation, the first heat exchanger 148 cools the second effluent 118 with water as a cooling medium. For example, the first heat exchanger 148 may cool the second effluent 118 to a temperature in the range of 150°C to 350°C, or in the range of 200°C to 300°C, or in the range of 100°C to 150°C. The second effluent 118 may be cooled, for example, by an amount in a range of 50°C to 350°C across the first heat exchanger 148. The water (e.g. cooling medium as BFWfrom a BFW pump) may be heated in the first heat exchanger 148 with heat from the second effluent 118 to vaporize at least a portion of the water in the heat exchanger to give a discharged stream from the first heat exchanger 148 as steam. On the other hand, the first heat exchanger 148 may heat (pre-heat) the water to give heated water as the discharged stream that vaporizes (flashes) after exiting the first heat exchanger 148 into the steam and hot water.

[0062] The water utilized as cooling medium may be heated with heat from the second effluent 118 to [A] vaporize the water into steam in the first heat exchanger 148 or [B] for the heated water to vaporize (flash) downstream, for example, in a flash vessel or steam drum. The first heat exchanger 148 (as effluent cooler and steam generation heat exchanger) may be, for example, a shell-and-tube heat exchanger or a fin-type heat exchanger (e.g., with a finned-tube bundle), and so on. The water as cooling medium to be converted into steam may be, for example, demineralized water, steam condensate, or BFW, and the like.

[0063] In the depicted implementation, the first heat exchanger 148 is a steamgeneration heat exchanger to heat the water (e.g., liquid water) with the second effluent 118 as a heating medium to: [1] vaporize the water in the first heat exchanger 148 to generate steam from the water to give a stream discharged from the first heat exchanger 148 as steam; or [2] heat (pre-heat) and not vaporize the water to give a stream discharged from the first heat exchanger 148 as heated water for downstream vaporization of the water into the steam. Thus, the first heat exchanger 148 may be characterized as a steam-generation heat exchanger.

[0064] In the latter configuration [2], the first heat exchanger 148 may act as a preheater (e.g., BFW preheater). The steam generation system may include additional equipment, such as a vessel (e.g., flash vessel), a pump (e.g., boiler feedwater pump), etc. In embodiments, the first heat exchanger 148 may heat (preheat, not vaporize) the water for vaporization of the water into steam, for example, in a steam drum. In those embodiments, the first heat exchanger 148 may receive water from the steam drum or from a boiler feedwater (BFW) pump, and discharge heated (pre-heated) water (generally not steam) to, for example, the steam drum.

[0065] The second effluent 118 (as cooled by the first heat exchanger 148) may discharge from the first heat exchanger 148 to downstream processing. As discussed, the downstream processing of the second effluent 118 may isolate product ethylene and byproduct (coproduct) acetic acid. The second effluent 118 may flow from the first heat exchanger 148 through a second heat exchanger 150 (e.g., as a feed heat exchanger or a cross exchanger) in route to the downstream processing.

[0066] The ODH reactor system 100 may include the second heat exchanger 150 (feed heat exchanger) that heats the feed 108 flowing to the first ODH reactor 102. The second heat exchanger 150 may be, for example a shell-and-tube heat exchanger or a plate-fin heat exchanger. In implementations, the second heat exchanger 150 may be a cross exchanger, and in which the feed 108 is heated with the second effluent 118. Thus, the second effluent 118 operationally between the first heat exchanger 148 and the downstream processing may be utilized to heat the feed 108 in the second heat exchanger 150.

[0067] The steam generated via the first heat exchanger 148 and via the aforementioned heat pipe 112 and steam drum 138 may discharge into a steam header (or sub-header) conduit or through a conduit to a user, and so on. Higher- pressure steam may generally be more valuable than lower pressure steam. Higher-pressure steam, such as greater than 600 pounds per square inch gauge (psig) or greater than 1500 psig, may typically be more valuable than lower pressure steam, such as less than 600 psig or less than 150 psig. The pressure of the steam generated via the first heat exchanger 148 may be a function of the temperature of the second effluent 118 driven by the operating temperature (ODH reaction temperature) of the second ODH reactor 104.

[0068] Figure 2 is the heat pipe 112 of Figure 1. The heat pipe 212 is depicted as multiple (six) heat pipes 202 (heat tubes) generally aligned and extending in parallel. The heat pipes 202 (heat tubes) may be, for example, stainless steel or other metal alloy including nickel and / or chromium. The heat pipes 202 may each have internal capillaries and internal wicking. The heat pipes 202 may include a wick and a capillary channel. The wick may be a porous metal substrate foam, felt, mesh, or screen. The working fluid in the heat pipes 202 may include, for example, sodium, potassium, or cesium, or any combination thereof.

[0069] The heat pipes 202 (heat tubes) run from the interior (inside volume) of the effluent conduit 204 that conveys the effluent 110 (Figure 1) to the interior (inside volume) of the BFW conduit 206 that conveys the BFW 134 (Figure 1). The effluent 110 flows across the hot end 120 portion of the heat tubes 202 in the effluent conduit 204. The BFW 134 flows across the cold end 122 portion of the heat tubes 202 in the BFW conduit 206.

[0070] The heat pipes 202 (heat tubes) run through the interior (inside volume) of the second feed conduit 208 that conveys the second feed 132 (Figure 1) and through the interior (inside volume) of the steam conduit 210 that conveys the steam 136 (Figure 1). Thus, the second feed 132 flows across an intermediate portion of the heat tubes 202 (between the hot end 120 portion and the cold end 122 portion) in the second feed conduit 208. The steam 136 flows across an intermediate portion of the heat tubes 202 (between the hot end 120 portion and the cold end 122 portion) in the steam conduit 210. The heat pipes 202 traverse the open space (outside of the conduits) between the effluent conduit 204 and the steam conduit 210, between the steam conduit 210 and the second feed conduit 208, and between the second feed conduit 208 and the BFW conduit 206. These lengths (parts or portions) of the heat pipes 202 outside of the conduits 204, 206, 208, and 210 may be insulated with thermal insulation for reducing heat loss from the heat pipes 202 to the environment and for personnel protection.

[0071] Heat transfer occurs from the effluent 110 along the heat pipes 202 to the steam 136, the second feed 132, and the BFW 134. Therefore, the effluent 110 is cooled via the heat pipes 202. The steam 136, the second feed 132, and the BFW 134 are heated via the heat pipes 202 with the effluent 110. In operation, the temperature differential between the effluent 110 and the BFW 134 may be at least 200°C.

[0072] The heat pipes 202 may each have an outer diameter, for example, from 1 centimeter (cm) to 5 cm and a length up to 20 meters, such as in a range of 5 meters to 20 meters. The heat pipes 202 on the ends may have surface modification, such as fins, ribs, protuberances, pins, or any combinations thereof, on their exterior surface to improve heat transfer to and from the heat pipes 202. In some embodiments, the inner surface of the heat pipes 202 is scored with capillary striations to transport the condensed liquid back to the hot end 120 of the heat pipes 202. The sections of the heat pipes 202 outside of the conduits 204, 206, 208, and 210 can be straight or have bends or twists (helical) to allow for thermal expansion of the heat pipes 10 and the conduits 204, 206, 208, and 210.

[0073] The working fluid in the heat pipes 202 should vaporize at a temperature at least 50°C below (or at least 80°C below) the minimum anticipated temperature of the entering effluent 110. The working fluid in the heat pipe 202 should condense at a temperature at least 25°C, in some instances at least 50°C, above the maximum anticipated temperature of the BFW 134. The temperature of the entering BFW 134 should be below the condensation temperature of the working fluid in the heat pipes 202 (heat tubes). For a discussion of heat-pipe heat exchangers, see for example, U.S. Patent Application Publication No. 2021 / 0190435A1 and U.S. Provisional Application No. 63 / 237,000, both of which are incorporated herein by reference in their entirety. The arrangement (sequence) of the conduits along the heat pipe 112 (heat tubes 202) can be altered. For instance, the positions of the second feed conduit 208 and the BFW conduit 208 can be switched, such that the second feed 132 (not the BFW 134) flows across the cold end 122 portion of the heat tubes 202. Other configurations, arrangements, and sequences are applicable.

[0074] Figure 3 is a method 300 of operating an ODH reactor system. The ODH reactor system may include a first ODH reactor and a second ODH reactor, wherein the second ODH reactor is disposed operationally in series downstream of the first ODH reactor.

[0075] At block 302, the method includes providing a first feed including ethane and oxygen (O2) to the first ODH reactor, and dehydrogenating ethane to ethylene via ODH catalyst in the first ODH reactor, thereby forming water and acetic acid. In implementations, the first feed includes diluent including steam, nitrogen (N2), carbon dioxide, or methane, or any combinations thereof.

[0076] The ODH reaction in the first ODH reactor (and in the second ODH reactor) is promoted via the ODH catalyst. A primary reaction may be C2H6 + 0.5 O2 — > C2H4 + H2O, which is the conversion of ethane / oxygen to ethylene / water with the ethylene as a desired product. The coproduct acetic acid may also be produced in the ODH reaction via the reaction C2H6 + 1.5 O2 — > CH3COOH + H2O. Carbon monoxide and carbon dioxide may also be generated (typically undesired) as byproducts by the following reaction equations C2H6 + 2.5 O2 — > 2 CO + 3 H2O, and C2H6 + 3.5 O2 2 CO2 + 3 H2O.

[0077] At block 304, the method includes discharging effluent from the first ODH reactor across a first end portion of a heat pipe to a quench tower. The effluent includes ethane, ethylene, water, acetic acid, carbon dioxide, and carbon monoxide. The effluent may include oxygen (O2). The first end portion of the heat pipe may include the hot end of the heat pipe.

[0078] At block 306, the method includes flowing BFW across the heat pipe, e.g., across the second end portion (cold end portion) of the heat pipe, to heat the BFW with the effluent to generate steam from the BFW in a steam drum. The method includes discharging the steam overhead from the steam drum (or from an upper portion of the steam drum) across the heat pipe to heat the steam with the effluent. The steam as discharged from the upper portion of the steam drum may be saturated steam, and the steam as heated with the effluent via the heat pipe may be superheated steam.

[0079] At block 308, the method includes introducing BFW discharged from a bottom portion of the steam drum as quench water to the quench tower to quench the effluent that enters the quench tower, thereby reducing temperature of the effluent. The method may include maintaining a liquid level of BFW in the steam drum.

[0080] At block 310, the method includes introducing oxygen (O2) to a lower portion of the quench tower below a liquid level in the quench tower. This addition of oxygen is an inter-stage addition of oxygen operationally between the first ODH reactor and the second ODH reactor.

[0081] At block 312, the method includes discharging as a second feed to the second ODH reactor an overhead stream from the quench tower across the heat pipe to heat the overhead stream with the effluent. The overhead stream includes ethane, ethylene, oxygen (O2), water, acetic acid, carbon dioxide, and carbon monoxide. The overhead stream upstream of the heat pipe as discharged from the quench tower may be saturated in acetic acid and water. The heating of the overhead stream with the effluent via the heat pipe may give the overhead stream superheated with respect to not being saturated in acetic acid and not being saturated in water. Temperature of the second feed (overhead stream) to the second ODH reactor as heated via the heat pipe may be less than 200°C, or in the range of 150°C to 200°C, or in the range of 180°C to 200°C.

[0082] The method may include dehydrogenating ethane to ethylene via ODH catalyst in the second ODH reactor. The method may include discharging a second effluent from the second ODH reactor, the second effluent including ethane, ethylene, water, carbon dioxide, and carbon monoxide. The discharging of the second effluent may involve discharging the second effluent from the second ODH reactor through a heat exchanger to heat water to generate steam or to heat the first feed.

[0083] The discharging of the overhead stream from the quench tower across the heat pipe may involve flowing the overhead stream (instead of the BFW) across the second end portion of the heat pipe. In this alternate implementation, the BFW flows across the heat pipe at an intermediate portion between the first end portion (hot end portion) and the second end portion (cold end portion) of the heat pipe. The first end portion of the heat pipe may include the hot end of the heat pipe. The second end portion of the heat pipe may include the cold end of the heat Pipe.

[0084] At block 314, the method includes discharging liquid including water and acetic acid from a bottom portion of the quench tower through a bottoms discharge conduit, and controlling the liquid level in the quench tower by controlling flow rate of the liquid discharged via a control valve disposed along the bottoms discharge conduit.

[0085] With ODH catalyst (e.g., MoVNbTeOx), ethane undergoes oxidative dehydrogenation at temperatures, for example, between 300°C to 450°C to produce ethylene and byproducts. For this reaction, oxygen is generally the limiting reactant. On stoichiometric basis, oxygen to ethane molar ratio is 0.5. This corresponds to 33.3 vol% of oxygen and 66.6 vol% of ethane in the mixture. At elevated temperature and pressure, the amount of oxygen in the mixture is typically decreased in order to stay outside the upper flammable zone. For instance, the upper flammability limit (UFL) of ethane in ethane-oxygen mixture at 300°C and 500 kilopascal (kPa) is about 81 volume percent (vol%). This corresponds to oxygen to ethane molar ratio of approximately 0.23, which is well below the stoichiometry ratio of 0.5. The ethane conversion that can be achieved at this oxygen to ethane molar ratio of 0.23 is around 40%. For higher ethane conversion, the oxygen to ethane molar ratio needs to be raised. There are two ways to accommodate an increase in oxygen. First, a way to do this while ensuring that the mixture is not flammable is by addition of diluent to the feed. Second, a way to do this for multiple ODH reactors in series is staged oxygen injection.

[0086] For the feed dilution, the amount of diluent required will be at least 70 vol%. Consequently, this results in large reactor size for a given productivity and majority of the reactor is occupied by diluent component. In addition, the size of equipment at the back end will also increase depending on the type of diluent used.

[0087] For the staged oxygen injection, more than one reactor is implemented for higher ethane conversion. A concern is injecting and mixing oxygen at each interstage while avoiding auto-ignition. The product effluent from the previous stage can be cooled via a heat exchanger before the before introduction of oxygen into this inter-stage stream. For embodiments here, both quenching and oxygen injection are carried out inside a single column. Oxygen is bubbled through liquid water held in the lower section of the column and quenching of the hot gaseous effluent from the first reactor is performed in the upper section of the column. The column (e.g., 114 of Figure 1) may be labeled as a quench tower. There is direct contact of all the process fluids in the column, e.g., mass and heat transfer occurs at the same time, and a conventional indirect heat exchanger (e.g., shell-and-tube heat exchanger) is not included in implementations for cooling of the first reactor effluent. A heat pipe (as an indirect heat exchanger) may be utilized to recover heat from the first reactor effluent for generating steam, and thus the heat pipe cools the effluent. The amount of acetic acid fed into the second reactor from the column may be adjusted by the temperature or amount of water used for quenching.

[0088] EXAMPLES

[0089] In order to explore the effect of acetic acid in ODH reactor feed on ODH catalyst activity in the ODH reactor and on the product effluent distribution (composition) discharged from the ODH reactor, four experiments 1 , 2, 3, and 4 were conducted with different respective wet feed compositions for the ODH reactor.

[0090] In experiments 1 and 2, the gas hourly space velocity (GHSV) was 648 IT1, reaction temperature was 320-321°C, reaction operating pressure was about atmospheric, and the dry feed composition was C2H6 / O2 / CO2 = 38 / 21 / 41 vol%. The wet feed composition for experiments 1 and 2 is given in Table 1.

[0091] Table 1. Wet Feed Composition

[0092] The catalyst activity results are shown in Table 2. The highlights of the activity results indicated that the presence of 2 vol% acetic acid (or 0.03 volume ratio of acetic acid to water) in the feed led into (1) partial suppression of acetic acid formation, (2) no change to ethylene yield, and (3) no change in ethane conversion. This finding reports ODH product flexibility by changing the ratio of feed acetic acid to water to suppress formation of acetic acid in the ODH reactor.

[0093] Table 2. Catalyst Activity In experiments 3 and 4, the GHSV was 648 h-1, reaction temperature was

[0094] 324°C, reaction operating pressure was about atmospheric, and the dry feed composition of C2H6 / O2 / CO2 = 38 / 21 / 41 vol%. Thus, these conditions were identical to those conditions for experiments 1 and 2, except for a slight difference in reaction temperature. The wet feed composition for experiments 3 and 4 is given in Table 3.

[0095] Table 3. Wet Feed Composition

[0096] The catalyst activity results for experiments 3 and 4 are shown in Table 4.

[0097] The highlights of the activity results indicated that the presence of 3 vol% acetic acid (or 0.1 volume ratio of acetic acid to water) in the feed led into (1) complete suppression of acetic acid formation, (2) almost no change to ethylene yield, and (3) increase in ethane conversion. This finding reports ODH product flexibility by changing the ratio of feed acetic acid to water to suppress formation of acetic acid in the ODH reactor. Table 4. Catalyst Activity

[0098] A fixed bed reactor unit (FBRLI) apparatus was used to conduct experiments 1, 2, 3, and 4 related to addition of acetic acid in the feed stream for the oxidative dehydrogenation of ethane. The FBRLI apparatus included two vertically oriented fixed bed tubular reactors in series, each reactor a SS316L tube with an outer diameter of 1” and a length of 34”, wrapped in an electrical heating jacket and sealed with ceramic insulating material. The two reactors were operated collectively as a single reactor. Each reactor contained an identical catalyst bed consisting of one weight unit of catalyst to 2.14 units of weight of DENSTONE® 99 (mainly alpha alumina) powder. Total weight of the catalyst in each reactor was 143 g catalyst having the formula MoV0.40Nb0.i6Te0.14O, with relative atomic amounts of each component, relative to a relative amount of Mo of 1, shown in subscript. The remainder of each reactor, below and above the catalyst bed was packed with quartz powder secured in place with glass wool to minimize risk of bed movement during the experimental runs.

[0099] The temperature of each of the reactors were monitored using corresponding 7-point thermocouples present in each reactor, 4 of which were situated within each catalyst bed. Temperature control, particularly at lower temperatures, was limited and resulted in fluctuations. Temperatures listed in the examples represents averages of the temperatures at the 8 different locations within the two catalyst beds. Both reactors were being controlled for temperature by controlling the pressure and boiling temperature of water inside water jackets surrounding each reactor.

[0100] For the experimental setup, a pressure transducer located immediately upstream of the first reactor was used to monitor the pressure at the inlet. The product stream leaving the second reactor was passed through condensing units before venting to air, which indicates that pressure at the point approximates 0 psig. The term “selectivity” refers to the carbon atom selectivity, based on the degree to which ethane is consumed. Selectivity, stated as a %, can be calculated according to the formula: where X is the product that is being assessed, the net mass flow rate refers to flow in g / min for X or converted C2H6 and is equal to the mass flow rate of X or converted C2H6 in the product stream minus the mass flow rate of component X or converted C2H6 in the feed stream, and molar equivalent (Mol. Equiv.) refers to the amount of X, in moles, that reacts completely with or is produced by one mole of ethane. If the sum of all selectivities for products derived from conversion of ethane did not total 100%, the selectivities are normalized to 100%. Normalization for each product can be calculated by dividing the selectivity for that product by the sum of all carbon atom product selectivities.

[0101] Embodiments

[0102] An embodiment described herein provides a method of operating an oxidative dehydrogenation (ODH) reactor system. The method includes providing a first feed including ethane and oxygen (O2) to a first ODH reactor, dehydrogenating ethane to ethylene via ODH catalyst in the first ODH reactor, thereby forming water and acetic acid. An effluent is discharged from the first ODH reactor across a first end portion of a heat pipe to a quench tower, the effluent including ethane, ethylene, water, acetic acid, carbon dioxide, and carbon monoxide. The boiler feed water (BFW) is flowed across the heat pipe to heat the BFWwith the effluent to generate steam from the BFW in a steam drum, and discharging the steam from an upper portion of the steam drum across the heat pipe to heat the steam with the effluent. BFW discharged from a bottom portion of the steam drum is introduced as quench water to the quench tower to quench the effluent that enters the quench tower, thereby reducing temperature of the effluent. Oxygen (O2) is introduced to a lower portion of the quench tower below a liquid level in the quench tower. A second ODH reactor an overhead stream from the quench tower is discharged across the heat pipe to heat the overhead stream with the effluent, the overhead stream including ethane, ethylene, oxygen (O2), water, acetic acid, carbon dioxide, and carbon monoxide.

[0103] In an aspect, combinable with any other aspect, the method includes discharging liquid including water and acetic acid from a bottom portion of the quench tower through a bottoms discharge conduit, and controlling the liquid level in the quench tower by controlling flow rate of the liquid discharged via a control valve disposed along the bottoms discharge conduit.

[0104] In an aspect, combinable with any other aspect, the overhead stream upstream of the heat pipe as discharged from the quench tower is saturated in acetic acid and water, and wherein heating the overhead stream with the effluent via the heat pipe gives the overhead stream superheated with respect to not being saturated in acetic acid and not being saturated in water.

[0105] In an aspect, combinable with any other aspect, the temperature of the second feed including the overhead stream as heated via the heat pipe is less than 200°C.

[0106] In an aspect, combinable with any other aspect, the steam as discharged from the upper portion of the steam drum includes saturated steam, and wherein the steam as heated with the effluent via the heat pipe includes superheated steam.

[0107] In an aspect, combinable with any other aspect, the method includes maintaining a liquid level of BFW in the steam drum, wherein the first end portion of the heat pipe includes a hot end of the heat pipe.

[0108] In an aspect, combinable with any other aspect, flowing BFW across the heat pipe includes flowing the BFW across a second end portion of the heat pipe, or wherein discharging the overhead stream from the quench tower across the heat pipe includes flowing the overhead stream across the second end portion of the heat pipe.

[0109] In an aspect, combinable with any other aspect, the first end portion includes a hot end of the heat pipe, and wherein second end portion includes a cold end of the heat pipe. In an aspect, combinable with any other aspect, the first feed includes diluent including steam, nitrogen (N2), carbon dioxide, or methane, or any combinations thereof, and wherein the effluent includes oxygen (O2).

[0110] In an aspect, combinable with any other aspect, the method includes dehydrogenating ethane to ethylene via ODH catalyst in the second ODH reactor.

[0111] In an aspect, combinable with any other aspect, the method includes discharging a second effluent from the second ODH reactor, the second effluent including ethane, ethylene, water, carbon dioxide, and carbon monoxide.

[0112] In an aspect, combinable with any other aspect, the ODH reactor system includes the first ODH reactor and the second ODH reactor, wherein the second ODH reactor is disposed operationally in series downstream of the first ODH reactor, and wherein discharging the second effluent includes discharging the second effluent from the second ODH reactor through a heat exchanger to water to generate steam or to heat the first feed or to heat the second feed.

[0113] Another embodiment described herein provides an oxidative dehydrogenation (ODH) reactor system. The ODH reactor system includes a first ODH reactor to receive a first feed including ethane and oxygen (O2), dehydrogenate ethane to ethylene via first ODH catalyst in the first ODH reactor, and discharge a first effluent through a first effluent conduit across a first end portion of a heat pipe to a quench tower, the first effluent including ethane, ethylene, water, acetic acid, carbon dioxide, and carbon monoxide. The ODH reactor system includes the heat pipe to heat boiler feedwater (BFW) with the effluent for generation of steam from the BFW in a steam drum, heat steam discharged from the steam drum with the effluent, and heat an overhead stream from the quench tower with the effluent, wherein the overhead stream is a second feed to a second ODH reactor, the overhead stream including ethane, ethylene, oxygen (O2), water, acetic acid, carbon dioxide, and carbon monoxide. The ODH reactor system includes the quench tower including a column vessel to receive BFW from a bottom portion of the steam drum to quench the first effluent, receive an oxygen (O2) stream introduced below a liquid level in the quench tower, and discharge liquid including water and acetic acid from a bottom portion of the quench tower through a bottoms discharge conduit.

[0114] In an aspect, combinable with any other aspect, the ODH reactor system includes including a control valve disposed along the bottoms discharge conduit to control flow rate of the liquid discharged from the bottom portion of the quench tower to control the liquid level in the quench tower.

[0115] In an aspect, combinable with any other aspect, the ODH reactor system is configured to flow the BFW or the overhead stream across a second end portion of the heat pipe.

[0116] In an aspect, combinable with any other aspect, the first end portion of the heat pipe includes a hot end of the heat pipe, and wherein the second end portion of the heat pipe includes a cold end of the heat pipe.

[0117] In an aspect, combinable with any other aspect, the steam as discharged overhead from the steam drum includes saturated steam, and wherein the steam as heated with the effluent via the heat pipe includes superheated steam.

[0118] In an aspect, combinable with any other aspect, the ODH reactor system includes the second ODH reactor to dehydrogenate ethane to ethylene via second ODH catalyst in the second ODH reactor and discharge a second effluent through a second effluent conduit, the second effluent including ethane, ethylene, water, acetic acid, carbon dioxide, and carbon monoxide, wherein the second ODH reactor is disposed operationally in series downstream of the first ODH reactor.

[0119] In an aspect, combinable with any other aspect, the ODH reactor system includes a heat exchanger disposed along the second effluent conduit to heat the first feed or the second feed with the second effluent.

[0120] In an aspect, combinable with any other aspect, the ODH reactor system includes a heat exchanger disposed along the second effluent conduit to heat water with the second effluent to generate steam from the water.

[0121] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure.

Claims

CLAIMS1. A method of operating an oxidative dehydrogenation (ODH) reactor system, the method comprising: providing a first feed comprising ethane and oxygen (O2) to a first ODH reactor; dehydrogenating ethane to ethylene via ODH catalyst in the first ODH reactor, thereby forming water and acetic acid; discharging effluent from the first ODH reactor across a first end portion of a heat pipe to a quench tower, the effluent comprising ethane, ethylene, water, acetic acid, carbon dioxide, and carbon monoxide; flowing boiler feedwater (BFW) across the heat pipe to heat the BFWwith the effluent to generate steam from the BFW in a steam drum, and discharging the steam from an upper portion of the steam drum across the heat pipe to heat the steam with the effluent; introducing BFW discharged from a bottom portion of the steam drum as quench water to the quench tower to quench the effluent that enters the quench tower, thereby reducing temperature of the effluent; introducing oxygen (O2) to a lower portion of the quench tower below a liquid level in the quench tower; and discharging as a second feed to a second ODH reactor an overhead stream from the quench tower across the heat pipe to heat the overhead stream with the effluent, the overhead stream comprising ethane, ethylene, oxygen (O2), water, acetic acid, carbon dioxide, and carbon monoxide.

2. The method of claim 1 , comprising: discharging liquid comprising water and acetic acid from a bottom portion of the quench tower through a bottoms discharge conduit; and controlling the liquid level in the quench tower by controlling flow rate of the liquid discharged via a control valve disposed along the bottoms discharge conduit.

3. The method of claim 1 , wherein the overhead stream upstream of the heat pipe as discharged from the quench tower is saturated in acetic acid and water, and wherein heating the overhead stream with the effluent via the heat pipe gives the overhead stream superheated with respect to not being saturated in acetic acid and not being saturated in water.

4. The method of claim 1, wherein temperature of the second feed comprising the overhead stream as heated via the heat pipe is less than 200°C.

5. The method of claim 1, wherein the steam as discharged from the upper portion of the steam drum comprises saturated steam, and wherein the steam as heated with the effluent via the heat pipe comprises superheated steam.

6. The method of claim 1, comprising maintaining a liquid level of BFW in the steam drum, wherein the first end portion of the heat pipe comprises a hot end of the heat pipe.

7. The method of claim 1, wherein flowing BFW across the heat pipe comprises flowing the BFW across a second end portion of the heat pipe, or wherein discharging the overhead stream from the quench tower across the heat pipe comprises flowing the overhead stream across the second end portion of the heat Pipe.

8. The method of claim 7, wherein the first end portion comprises a hot end of the heat pipe, and wherein second end portion comprises a cold end of the heat Pipe.

9. The method of claim 1 , wherein the first feed comprises diluent comprising steam, nitrogen (N2), carbon dioxide, or methane, or any combinations thereof, and wherein the effluent comprises oxygen (O2).

10. The method of claim 1, comprising dehydrogenating ethane to ethylene via ODH catalyst in the second ODH reactor.

11. The method of claim 10, comprising discharging a second effluent from the second ODH reactor, the second effluent comprising ethane, ethylene, water, carbon dioxide, and carbon monoxide.

12. The method of claim 11 , wherein the ODH reactor system comprises the first ODH reactor and the second ODH reactor, wherein the second ODH reactor is disposed operationally in series downstream of the first ODH reactor, and wherein discharging the second effluent comprises discharging the second effluent from the second ODH reactor through a heat exchanger to water to generate steam or to heat the first feed or to heat the second feed.

13. An oxidative dehydrogenation (ODH) reactor system, comprising: a first ODH reactor to receive a first feed comprising ethane and oxygen (O2), dehydrogenate ethane to ethylene via first ODH catalyst in the first ODH reactor, and discharge a first effluent through a first effluent conduit across a firstend portion of a heat pipe to a quench tower, the first effluent comprising ethane, ethylene, water, acetic acid, carbon dioxide, and carbon monoxide; the heat pipe to heat boiler feedwater (BFW) with the effluent for generation of steam from the BFW in a steam drum, heat steam discharged from the steam drum with the effluent, and heat an overhead stream from the quench tower with the effluent, wherein the overhead stream is a second feed to a second ODH reactor, the overhead stream comprising ethane, ethylene, oxygen (O2), water, acetic acid, carbon dioxide, and carbon monoxide; and the quench tower comprising a column vessel to receive BFW from a bottom portion of the steam drum to quench the first effluent, receive an oxygen (O2) stream introduced below a liquid level in the quench tower, and discharge liquid comprising water and acetic acid from a bottom portion of the quench tower through a bottoms discharge conduit.

14. The ODH reactor system of claim 13, comprising a control valve disposed along the bottoms discharge conduit to control flow rate of the liquid discharged from the bottom portion of the quench tower to control the liquid level in the quench tower.

15. The ODH reactor system of claim 13, wherein the ODH reactor system is configured to flow the BFW or the overhead stream across a second end portion of the heat pipe.

16. The ODH reactor system of claim 15, wherein the first end portion of the heat pipe comprises a hot end of the heat pipe, and wherein the second end portion of the heat pipe comprises a cold end of the heat pipe.

17. The ODH reactor system of claim 13, wherein the steam as discharged overhead from the steam drum comprises saturated steam, and wherein the steam as heated with the effluent via the heat pipe comprises superheated steam.

18. The ODH reactor system of claim 13, comprising the second ODH reactor to dehydrogenate ethane to ethylene via second ODH catalyst in the second ODH reactor and discharge a second effluent through a second effluent conduit, the second effluent comprising ethane, ethylene, water, acetic acid, carbon dioxide, and carbon monoxide, wherein the second ODH reactor is disposed operationally in series downstream of the first ODH reactor.

19. The ODH reactor system of claim 18, comprising a heat exchanger disposed along the second effluent conduit to heat the first feed or the second feed with the second effluent.

20. The ODH reactor system of claim 18, comprising a heat exchanger disposed along the second effluent conduit to heat water with the second effluent to generate steam from the water.

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