Integration for feed dilution in oxidative dehydrogenation (ODH) reactor systems

Abstract

A system and method for producing ethylene, comprising: dehydrogenating ethane to ethylene in the presence of oxygen over an ODH catalyst in an ODH reactor; discharging an effluent from the ODH reactor (comprising at least ethylene, water, and acetic acid); recovering heat from the effluent to treat an ethane-containing feed for the ODH reactor; recovering water from the effluent as recycle water to add to the feed during water dilution of the feed; and adding oxygen to the feed to obtain a mixed feed to the ODH reactor comprising ethane, oxygen, and recycle water.

Description

Technical Field

[0001] (Technical Field) This disclosure relates to oxidative dehydrogenation (ODH) for producing ethylene.

[0002] (Claims of Priority) This application claims priority based on U.S. Provisional Application No. 63 / 181,086, filed on April 28, 2021, the entire content of which is incorporated herein by reference.

Background Art

[0003] The catalytic oxidative dehydrogenation of an alkane to the corresponding alkene is an alternative to steam cracking. In contrast to steam cracking, oxidative dehydrogenation (ODH) can be operated at low temperatures and generally does not produce coke. In the case of ethylene production, ODH can provide a higher ethylene yield than steam cracking. This ODH can be carried out in a reaction vessel having a catalyst for converting an alkane to the corresponding alkene. Acetic acid can be produced when converting a lower alkane (e.g., ethane) to the corresponding alkene (e.g., ethylene).

[0004] Carbon dioxide is the main greenhouse gas emitted by human activities. Carbon dioxide (CO2) can be generated in various industrial and chemical plant facilities, including ODH facilities. In such facilities, by using energy more efficiently, the CO2 emissions in the facility can be reduced, and as a result, the CO2 footprint of the facility may be decreased.

Summary of the Invention

[0005] One embodiment relates to a method for producing ethylene, comprising the steps of: adding water to ethane to obtain a mixture; passing the mixture through a feed heat exchanger and heating the mixture using heat from the effluent from the ODH reactor; and adding oxygen to the mixture to obtain a mixed feed for the ODH reactor. This method includes the steps of dehydrogenating ethane to ethylene via an ODH catalyst in the presence of oxygen in an ODH reactor, and discharging effluent from the ODH reactor, the effluent containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and unreacted ethane.

[0006] Another embodiment relates to a method for producing ethylene, comprising the steps of: dehydrogenating ethane to ethylene via an ODH catalyst in the presence of oxygen in an ODH reactor, thereby forming acetic acid in the ODH reactor; and discharging an effluent from the ODH reactor containing ethylene, acetic acid, and water. The method comprises the steps of separating the effluent into gas and raw material acetic acid in a flash drum, the gas containing ethylene, water, acetic acid, ethane, carbon dioxide, and carbon monoxide, and the raw material acetic acid containing acetic acid and water. The method comprises the steps of removing acetic acid and water from the gas in an acetic acid scrubber container, and utilizing the bottom flow discharged from the acetic acid scrubber container as recycled water for diluting the feed to the ODH reactor.

[0007] Another embodiment relates to an ethylene production system comprising an oxidative dehydrogenation (ODH) reactor having an ODH catalyst for dehydrogenating ethane to ethylene and discharging an effluent containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and ethane. The ethylene production system comprises a flash drum for separating the effluent from the ODH reactor into gas and feedstock acetic acid, the gas containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and ethane, and the feedstock acetic acid containing acetic acid and water. The ethylene production system comprises an acetic acid scrubber vessel for removing acetic acid and water from the gas and discharging the bottom flow as recycled water for diluting the feedstock to the ODH reactor, the bottom flow containing acetic acid and water. The ethylene production system may also comprise a cross exchanger for heating the recycled water using the effluent, and / or a cross exchanger for receiving a mixture of recycled water and ethane and heating this mixture using the effluent. The ethylene production system may also comprise a cross exchanger for receiving a mixture of recycled water and oxygen and heating the mixture using the effluent for feed to the ODH reactor.

[0008] Another embodiment relates to a method for producing ethylene, comprising the steps of: dehydrogenating ethane to ethylene via an ODH catalyst in the presence of oxygen in an ODH reactor; discharging effluent from the ODH reactor (including ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and unreacted ethane); recovering heat from the effluent in order to process a feed containing ethane for the ODH reactor; recovering water from the effluent as recycled water for addition to the feed when diluting the feed with water; and adding oxygen to the feed to obtain a mixed feed containing ethane and oxygen for the ODH reactor, wherein the mixed feed includes water recovered as recycled water from the effluent, and the recycled water is added to the feed.

[0009] Another embodiment relates to a method for producing ethylene, comprising the step of discharging effluent (containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and unreacted ethane) from an ODH reactor that dehydrogenates ethane to ethylene. The method comprises the step of diluting a feed containing ethane for the ODH reactor with water. This dilution includes adding recycled water to the ethane. The method comprises the step of recovering water from the effluent to obtain recovered water as recycled water for dilution. The method comprises the steps of passing the feed downstream of the dilution through a feed heat exchanger and heating the feed with the effluent, and adding oxygen to the feed to obtain a mixed feed for the ODH reactor.

[0010] Details of one or more embodiments are described in the accompanying drawings and the following specification. Other features and advantages will be apparent from the specification and drawings, as well as the claims. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows an ethylene production system. [Figure 1A] Figure 1 shows one embodiment of the acetic acid unit in an ethylene production system. [Figure 2] This figure shows an embodiment of an ethylene production system. [Figure 3] This figure shows an embodiment of an ethylene production system. [Figure 4] This figure shows an embodiment of an ethylene production system. [Figure 5] This figure shows an embodiment of an ethylene production system. [Figure 6] This figure shows an embodiment of an ethylene production system. [Figure 7] This figure shows an embodiment of an ethylene production system. [Figure 8] This figure shows an embodiment of an ethylene production system. [Figure 9] This figure shows an embodiment of an ethylene production system. [Figure 10] This is a plot of the flammability limit as a function of inert concentration. [Figure 11] This is a block flow diagram of the ethylene production method. Similar reference numbers and notations in the various diagrams above indicate the same elements. [Modes for carrying out the invention]

[0012] The embodiments relate to the integration of an oxidative dehydrogenation (ODH) reactor system and an ODH reactor feed facility, including feed dilution. This integration includes both energy integration and water recycling. Energy integration may include supplying heat from the ODH reactor effluent to heat the feed to the ODH reactor and to supply heat for diluting the feed to the ODH reactor. Feed dilution may include adding a water (steam) diluent to the feed.

[0013] The integration of water recycling in an ODH reactor system for diluting the ODH reactor feed can be referred to as water recovery or system water circulation. Water recycling may include supplying water recovered from the ODH reactor effluent to the ODH reactor feed as recovered or recycled water for addition as a water diluent. In some embodiments, using water recovered from the ODH reactor effluent to dilute the ODH reactor feed can approximate a closed-circuit water system that uses little to no external water for diluting the feed.

[0014] This disclosure includes the dehydrogenation of ethane to ethylene via an ODH catalyst in the presence of oxygen within an ODH reactor. Acetic acid may also be formed within the ODH reactor. Evaporates discharged from the ODH reactor include at least ethylene, acetic acid, water, carbon dioxide (CO2), carbon monoxide (CO), and unreacted ethane. As previously stated, some embodiments relate to processing feed for an ODH reactor, including adding a diluent (e.g., water) to the feed.

[0015] The advantages of ODH reactor technology for producing ethylene are that it has less CO2 emissions and higher energy efficiency compared to steam cracking for producing ethylene. To further advance these advantages, embodiments herein can include process integration within the ODH reactor plant to incorporate beneficial utilization of process streams within the ODH reactor system.

[0016] The feed mixture to the ODH reactor typically contains at least ethane and oxygen. To maintain the mixed feed outside the range of flammable conditions (outside the flammable envelope), the mixed feed may be diluted. Steam or vaporized water can be an attractive diluent, for example, because in practice, separation of water from the ODH reactor product stream (effluent) is relatively straightforward.

[0017] To dilute the feed, a fairly large amount of water may generally be used. Thus, evaporating liquid water to produce vaporized water for addition as a diluent to the feed can potentially utilize a significant amount of heat. Further, by cooling and condensing the water vapor (added to the feed) from the ODH reactor effluent, a significant amount of cooling capacity can be used. These are reasons to improve the integration of water and heat between the feed dilution system and the cooling of the reactor effluent, acetic acid unit, and acetic acid scrubbing, as described below. These improvements in integration can reduce or eliminate the need for additional water supply and potentially reduce the load on the steam and cooling tower systems.

[0018] A closed-loop (or substantially closed-loop) water supply system can also be introduced. In this loop, water can be added to the mixed feed to the reactor, condensed with acetic acid from the reactor effluent, separated from the acetic acid, recycled to the acetic acid scrubber, and then supplied to the feed dilution system. This can potentially reduce or generally eliminate the need for external water supply in feed dilution.

[0019] In embodiments, in order to add steam to the hydrocarbon feed to the reactor, for example, a dilution steam drum or a saturation tower can be used. The dilution steam drum may be easier in supplying dilution steam, but unfortunately may rely on an expensive heat source such as medium-pressure steam. In an embodiment, instead, medium-pressure steam can be effectively utilized, for example, for driving a steam turbine. The saturation tower can saturate hydrocarbon (e.g., ethane) gas and / or oxygen gas with steam and can circulate a relatively large amount of water. In order to reduce the energy requirement of the dilution system (including the dilution steam drum or the saturation tower), ethane and / or oxygen can also be saturated with steam with respect to a heating medium such as reactor effluent or steam (e.g., low-pressure steam or medium-pressure steam) in a heat exchanger.

[0020] This disclosure captures energy integration and water integration, which provide a steam diluent. Nine option examples are shown below. These are aimed at integrating ethane / oxygen feed and water for supply to an ODH reactor plant configuration. The nine options are shown as examples. Other configurations are also applicable. Options 2-9 promote a reduction of up to 40% or more in energy consumption compared to Option 1 as the basic case. Option 1 can be considered the basic line case when integrating a hydrocarbon saturation tower into an ODH reactor plant. The figure shows a single-stage ODH reactor (e.g., with feed components added at the inlet), but the described technology is also applicable to other ODH reactor configurations, including multi-stage reactors and reactors with multiple inter-stage feed additions.

[0021] Embodiments with configurations for saturating an ethane (and oxygen) feed with water can be targeted at process integration for cooling the reactor effluent from the ODH reactor and beneficially recovering heat from the effluent. In the presented options, the reactor effluent discharged from the reactor can first be utilized for the generation or superheating of (ultra) high-pressure steam, and then the effluent is exchanged with the reactor feed, heating the reactor feed and cooling the effluent.

[0022] Embodiments may include discharging an effluent containing ethylene, acetic acid, and water from the ODH reactor, generating steam by discharging the effluent through a steam-generating heat exchanger, and heating the feed containing ethane for the ODH reactor by discharging it through a feed heat exchanger (cross-exchanger). As previously mentioned, the effluent may also contain CO2, CO, and unreacted ethane. The raw material acetic acid can be separated from the effluent. The raw material acetic acid may constitute the majority of the acetic acid and water in the effluent and may be a condensed form thereof. The raw material acetic acid can be processed in an acetic acid unit to obtain an acetic acid product. The gas containing ethylene and unreacted ethane (and possibly CO and CO2) can be separated from the effluent and scrubbed to remove acetic acid and water to obtain a process gas. The removed acetic acid and water are generally the remainder of acetic acid and water from the effluent that were not recovered in the raw material acetic acid. In embodiments, the process gas can be sent to a process gas compressor for further processing to obtain an ethylene product.

[0023] As shown, diluents are used to keep the feed and the ethane-oxygen mixture in the ODH reactor outside the range of the flammable envelope. As previously mentioned, evaporated water or steam can be used as a diluent. The target oxygen concentration may vary depending on the pressure and temperature of the mixed feed containing ethane, oxygen, and water into the ODH reactor. Several process configuration schemes (e.g., including ethane-saturated towers and oxygen-saturated towers) can be implemented to mix water as a diluent with ethane and oxygen. Different feed saturation schemes and thermal integration options, including heating by the ODH reactor effluent, were compared.

[0024] The ODH reaction, which dehydrogenates feed ethane to produce ethylene and generates acetic acid as a byproduct, can occur at temperatures of 300-450°C using, for example, a low-temperature ODH catalyst (e.g., mixed metal oxides such as MoVNbTeOx or MoVNbTeOx) and produce ethylene with high selectivity. This reaction may also involve supplying oxygen gas and ethane to the ODH reactor in a stoichiometric ratio of 0.5 or higher. This corresponds to 33.3 vol% oxygen gas and 66.6 vol% ethane in the ethane-oxygen mixture. Coincidentally, this may correspond to the flammability limit (UFL) of ethane at 66.0 vol%, i.e., 25°C and 100 kilopascals (kPa). As temperature and pressure increase, the amount of oxygen allowed in the ethane-oxygen mixture may decrease to prevent exceeding the flammability limit of the mixture. For example, at 300°C and 500kPa, the UFL of ethane in an ethane-oxygen mixture is approximately 81% by volume. This means that the allowable oxygen concentration in the mixture is less than 19% by volume, as shown in Figure 10. Since this amount of oxygen is less than what is required for the stoichiometric reaction, the ethane conversion rate will be low (for example, if the oxygen in the mixture is 19% by volume, the ethane conversion rate will decrease by approximately 40%). As a result, a large amount of unreacted ethane will be present in the ODH reactor effluent, which can place a high load on the downstream C2 splitter.

[0025] A method for increasing the oxygen-to-ethane ratio at high temperature and / or high pressure is to add a diluent to the ethane-oxygen mixture. Examples of diluents include nitrogen, CO2, vapor, helium (He), argon (Ar), and methane. Based on the quenching potential of all these diluents, CO2, with a quenching factor of 1.751 at an adiabatic flame temperature of 1600 K, is considered the most effective. Unfortunately, however, the CO2 used as a diluent and the CO2 generated during the reaction usually need to be separated from the ODH product stream. This separation can be performed, for example, using both amine and caustic columns. Depending on the amount of CO2 to be separated, amine and caustic systems can be inefficient and relatively expensive to operate. When nitrogen, He, Ar, or methane are used as diluents, the diluent passes through downstream equipment along with the process gas, resulting in larger equipment sizes. Furthermore, the utilities required to separate these gases can be expensive, potentially increasing operating costs.

[0026] Steam has a quenching potential of 1.259, which may make it more effective than the other diluents mentioned above, except for CO2. Removing steam from the ODH process gas by cooling before sending the product flow to downstream equipment makes using steam as a diluent more attractive compared to other types of diluents. However, as tests conducted in fixed-bed reactor units and other information indicate, steam may not be an inert diluent. Steam may catalyze the formation of acetic acid. Therefore, reducing the amount required for dilution can mitigate its impact on the amount of acetic acid produced.

[0027] Embodiments of this specification include diluting and mixing feed for an ODH reactor. As previously stated, several options are shown as examples.

[0028] The two main heat demands in the ODH reaction process for producing ethylene are (1) feed saturation to dilute the mixed feed, and (2) solvent recovery tower in the acetic acid (AA) unit that supplies the acetic acid (AA) product flow. The two main cooling demands in this process are (1) cooling of the reactor effluent, and (2) condensation of the overhead flow from the solvent recovery tower in the AA unit.

[0029] Energy integration and improved overall energy efficiency of the ODH reactor system, including upstream feed saturation using water, can reduce operating costs and greenhouse gas emissions such as carbon dioxide. Energy integration for reactor feed saturation, acetic acid recovery, and reactor effluent cooling is disclosed. Such integration can generally lead to reductions in operating costs for the entire ODH reactor plant, as well as reductions in capital costs for at least the steam system, cooling water system, and acetic acid unit.

[0030] Options for reactor feed saturation and reactor effluent energy integration are presented. The example of Option 1 shown below can serve as the base case. Other options presented are typically compared to Option 1 as the base line case. However, the technology of this invention is not limited to the various options summarized or characterized in the table. Instead, a variety of set options, including Options 1-9, are presented as examples.

[0031] Figures 1 through 9 (options 1 through 9) may be shown in relation to each other, and may also contain progressive differences between them. For explanations of the text, designations, and reference numbers shown in a given figure in Figures 1 through 9, please also refer to the descriptions of the other figures in Figures 1 through 9. The descriptions of all the devices shown are not fully reproduced in the descriptions of each figure. Instead, similar reference numbers and designations in different drawings refer to similar elements.

[0032] Figure 1 shows an ethylene production system 100. As illustrated, Figure 1 can be characterized as Option 1 for comparison with subsequent figures. An ethane feed saturation unit (ethane saturation tower) is installed to obtain saturated ethane by saturating ethane with water. Oxygen gas (O2) may optionally be added to the saturated ethane. If added in this way, O2 may be added at a single addition point or gradually added in stages over multiple addition points. The saturated ethane feed can be heated (e.g., superheated) by mutual exchange (cross-exchange) with the reactor effluent or other heat sources. Because the amount of water required to saturate the ethane (e.g., water circulation) is relatively large, in this configuration of Figure 1, it may be possible to utilize a heat source with lower thermal quality, such as low-pressure (LP) steam, in the circulating water heater of the ethane saturation tower. In other words, a large-scale water circulation can be implemented around the ethane saturation tower to maintain a relatively low outlet temperature of the circulating water heater, allowing for advantageous use of LP steam as a heating medium. Therefore, the entire ODH reactor process may be less energy-intensive compared to configurations that utilize medium-pressure (MP) steam for ethane saturation. As will be discussed later, the ethane feed saturation unit (ethane saturation tower) may be a tray tower or a packed-bed tower.

[0033] The ethylene production system 100 comprises an ODH reactor 102 vessel having an ODH catalyst for dehydrogenating ethane into ethylene. The operating temperature of the reactor may be, for example, in the range of 300°C to 450°C. The ODH reaction is typically exothermic. The ODH reactor 102 system may utilize a heat transfer fluid to control the temperature of the ODH reactor 102. The heat transfer fluid can be used to remove heat from (or add heat to) the ODH reactor 102. The heat transfer fluid may be, for example, steam, water (including pressurized water or supercritical water), oil, molten salt, etc. The ODH reactor 102 may be, for example, a fixed-bed reactor (operating in a fixed bed of the ODH catalyst), a fluidized-bed reactor (operating in a fluidized bed of the catalyst), or another reactor type.

[0034] The ODH reaction from ethane (C2H6) to ethylene (C2H4) via the ODH catalyst in ODH reactor 102 includes the reaction equation C2H6 + 0.5O2 → C2H4 + H2O, or may be this reaction equation. Additional reactions in ODH reactor 102 may include the following: C2H6 + 1.5O2 → CH3COOH + H2O C2H6 + 2.5O2 → 2CO + 3H2O C2H6 + 3.5O2 → 2CO2 + 3H2O C2H4 + O2 → CH3COOH C2H4 + 2O2 → 2CO + 2H2O C2H4 + 3O2 → 2CO2 + 2H2O CH3COOH + O2 → 2CO + 2H2O CH3COOH + 2O2 → 2CO2 + 2H2O CO + 0.5O2 → CO2

[0035] Therefore, in addition to the ethylene produced, water (H2O), acetic acid (CH3COOH), carbon monoxide (CO), and carbon dioxide (CO2) may also be produced in the ODH reactor 102.

[0036] In the case of an ODH reactor as a fixed-bed reactor, the reactants are introduced from one end of the reactor and can flow through an immobilized catalyst. Products are formed, and the effluent containing the products can be discharged from the other end of the reactor. Each fixed-bed reactor has a catalyst bed and may have one or more tubes (e.g., metal tubes, ceramic tubes, etc.) for flowing the reactants. In the case of ODH reactor 102, the flowing reactants may be at least ethane / oxygen. The tubes may include, for example, steel mesh. Furthermore, the reactor temperature can be controlled by a heat transfer jacket or external heat exchanger (e.g., feed heat exchanger or recirculation heat exchanger) adjacent to the heat transfer tubes. The aforementioned heat transfer fluid may flow through the jacket or external heat exchanger.

[0037] An ODH reactor as a fluidized bed reactor can be (1) a non-circulating fluidized bed, (2) a circulating fluidized bed with a regenerator, or (3) a circulating fluidized bed without a regenerator. In embodiments, the fluidized bed reactor may have a support for the ODH catalyst. The support may be a porous structure or a distributor plate and may be located at the bottom of the reactor. The reactants may flow upward through the support at a rate that fluidizes the ODH catalyst bed. The reactants (e.g., ethane, oxygen, etc., in reactor 102) are converted into products (e.g., ethylene and acetic acid, in reactor 102) upon contact with the fluidized catalyst. The effluent containing the products may be discharged from the top of the reactor. A cooling jacket may facilitate temperature control of the reactor. The fluidized bed reactor may have heat transfer tubes, a jacket, or an external heat exchanger (e.g., a feed heat exchanger or a recirculation loop heat exchanger) to facilitate temperature control of the reactor. The aforementioned heat transfer fluid may flow through the reactor tubes, jacket, or external heat exchanger.

[0038] As shown, ODH catalysts can be operated as fixed-bed or fluidized-bed reactors. ODH catalysts capable of producing the ODH reaction, which dehydrogenates ethane to ethylene and forms acetic acid as a byproduct, can be applied to this technology. Low-temperature ODH catalysts may be effective. An example of an ODH catalyst usable in an ODH reactor is a low-temperature ODH catalyst containing molybdenum, vanadium, tellurium, niobium, and oxygen, with a molar ratio of molybdenum to vanadium of 1:0.12 to 1:0.49, a molar ratio of molybdenum to tellurium of 1:0.01 to 1:0.30, a molar ratio of molybdenum to niobium of 1:0.01 to 1:0.30, and oxygen present in an amount that satisfies the valence of at least the present metal elements. The molar ratios of molybdenum, vanadium, tellurium, and niobium can be determined by inductively coupled plasma mass spectrometry (ICP-MS). The catalyst may be used at temperatures below 450°C, below 425°C, or below 400°C when providing the ODH reaction.

[0039] Acetic acid may be formed as a byproduct during the ODH reaction, which dehydrogenates ethane. As mentioned above, water, carbon dioxide, and carbon monoxide are also formed during the ODH reaction. Therefore, the effluent 104 discharged from the ODH reactor 102 may contain ethylene, acetic acid, water, carbon dioxide, carbon monoxide, and unreacted ethane. The operating temperature of the ODH reactor 102 and the temperature of the discharged effluent 104 can be, for example, within the range of 300°C to 450°C.

[0040] The effluent 104 is sent through a conduit to a steam generating heat exchanger 106, where steam can be generated using the heat from the effluent 104. The steam generating heat exchanger 106 can be, for example, a shell-and-tube heat exchanger or a finned heat exchanger (e.g., one with a bundle of finned tubes). The effluent 104 can be cooled to at least 200°C to 350°C through the steam generating heat exchanger 106.

[0041] Water is heated in the steam-generating heat exchanger 106 by the heat from the effluent 104, and can be flushed into steam. The water may be, for example, boiler feedwater, demineralized water, or steam condensate. Two or more steam-generating heat exchangers 106 can be used in series and / or in parallel. A steam generation system having steam-generating heat exchangers 106 may include additional equipment such as a vessel (e.g., a flush vessel) and a pump (e.g., a boiler feedwater pump). The generated steam may be discharged into a conduit in a steam header (or sub-header) or discharged to the user through the conduit. High-pressure steam is generally more valuable than low-pressure steam.

[0042] High-pressure steam (e.g., above 500 pounds per square inch gauge (psig) or above 1500 psig) can typically be more valuable than low-pressure steam (e.g., below 500 psig or below 150 psig). The pressure of the steam generated through the steam generation heat exchanger 106 may be a function of the temperature of the effluent 104, which is determined by the operating temperature of the ODH reactor 102 (ODH reaction temperature).

[0043] The ethane saturation tower 110 can supply steam for the mixed feed 108 to the ODH reactor 102 vessel. The ethane discharged from the ethane saturation tower 110 may be water-saturated ethane. The ethylene production system 100 may include an ethane saturation tower 110 vessel (e.g., a column) for taking steam into the ethane gas 112 and discharging saturated ethane 114 for the mixed feed 108.

[0044] In this embodiment, liquid water 116 may enter the upper part of the saturation column 110 and flow downward through the column 110. The column 110 may have inlets (e.g., nozzles) connected to conduits by flanges or threads, the conduits carrying the incoming water 116. Ethane gas 112 may enter the lower part of the saturation column 110 and flow upward through the column 110. The column 110 may have packing or trays to provide a contact step between the ethane gas 112 and the water 116 for mass transfer of water vapor to the ethane gas 112. The column 110 may include random packing, structured packing, or column trays (e.g., sieve trays), or any combination thereof.

[0045] Liquid water 120 is discharged from the bottom of the ethane saturated column 110 (e.g., as a bottom flow) and can be recirculated via a water recirculation pump 122 (e.g., a centrifugal pump) as a water supply to the ethane saturated column 110. Thus, the ethane saturated column 110 may have a water recirculation loop. Water can be heated in a circulating water heater 118 (e.g., a shell-and-tube heat exchanger) using a heating medium such as steam (e.g., LP steam) to obtain liquid water 116 (heated) to enter the ethane saturated column 110. Saturated ethane 114 may be discharged from the ethane saturated column 110 to the top for supply to the ODH reactor 102. As used herein, the term “saturated” ethane means that the ethane gas is saturated with water. Saturated ethane 114 generally contains water vapor but little to no liquid water.

[0046] As explained, the amount of water used to saturate the ethane gas 112 may be relatively large. In this way, the flow rate of water circulating through the circulating water heater 118 can be made relatively large, thereby maintaining a relatively low outlet temperature of the circulating water heater 118. Therefore, in this embodiment, LP steam can be advantageously used as the heating medium for the circulating water heater 118.

[0047] The discharged saturated ethane 114 (ethane gas saturated with water vapor) may be sent through a feed heat exchanger 124 to heat (superheat) the saturated ethane 114 as feed to the ODH reactor 102. The saturated ethane 114 may be hot when discharged from the feed heat exchanger 124 if the ethane 114 is superheated (above the saturation temperature of water). The feed heat exchanger 124 may be, for example, a shell-and-tube heat exchanger or a plate-fin heat exchanger. In some embodiments, the feed heat exchanger 124 may be a cross exchanger in which the effluent 104 heats the saturated ethane 114, as shown in the figure. Thus, the effluent 104 can be cooled within the feed heat exchanger 124, for example, typically to at least 200°C to 350°C. In other embodiments, the feed heat exchanger 124 may utilize steam instead of the effluent 104 as the heating medium.

[0048] Oxygen gas (O2) 126 can be added to the saturated ethane 114 upstream of the feed heat exchanger 124, downstream of the heat exchanger 124, or both. In some embodiments, liquid oxygen may be received and evaporated to form vaporized oxygen gas (O2). Oxygen gas 126 may be added to the saturated ethane at a single addition point or at multiple addition points (e.g., 2 to 5 points). In the illustrated embodiment, five addition points are shown. In certain embodiments, the reason for providing multiple addition points may be to reduce the opportunity for pockets of oxygen gas 126 to form in the flowing saturated ethane 114.

[0049] Oxygen gas 126 may be added to the conduit carrying saturated ethane 114. In embodiments, the conduit may include an inline static mixer adjacent to (downstream of) the point of addition of oxygen gas 126 to saturated ethane 114. In embodiments, the conduit carrying oxygen gas 126 may be connected to the conduit carrying saturated ethane 114 via a pipe T-joint or similar pipe fitting. The mixed feed 108 to the ODH reactor 102 may include saturated ethane gas 114 and oxygen gas 126. As shown, water in saturated ethane gas 114 may be a diluent.

[0050] The spill 104 flows from the feed heat exchanger 124 through the cooler heat exchanger 128 to the flash drum 130. The flash drum 130 is, for example, a container having a vertical or horizontal orientation. In this embodiment, the level of the liquid (for example, raw material acetic acid, which may be mainly water) in the flash drum 130 can be maintained during operation.

[0051] The cooler heat exchanger 128 cools the effluent 104 (removes heat from the effluent 104). The cooling medium may be, for example, water from the cooling tower. The cooler heat exchanger 128 may be, for example, a shell-and-tube heat exchanger, a plate-fin heat exchanger, or another type of heat exchanger. In this embodiment, the cooler heat exchanger 128 discharges the effluent 104 at a temperature in the range of, for example, 30°C to 80°C. The cooler heat exchanger 128 may also be a condenser, in that the water and acetic acid in the effluent 104 can condense within the cooler heat exchanger 128.

[0052] The operating pressure of the flash drum 130 may be a function of the back pressure of the downstream process gas treatment (described later). The operating pressure of the flash drum 130 may be a function of the discharge pressure of the effluent 104 from the ODH reactor 104. The operating pressure of the flash drum 130 may be a function of the pressure drop associated with the flow of effluent 104 from the ODH reactor 102 through the pipes and heat exchangers to the flash drum 130 and the downstream process gas compressor.

[0053] The temperature of the effluent 104 entering the flash drum 130 may be affected by the amount of cooling of the effluent 104 in the feed heat exchanger 124 and the cooler heat exchanger 128. The amount of water in the raw material acetic acid 132 discharged as a bottom flow from the flash drum 130 may be a function of the temperature of the effluent 104 entering the flash drum 130. The lower the temperature of the effluent 104 entering the flash drum 130, the more water may be contained in the raw material acetic acid 132. This is thought to be because more water condenses in the effluent 104 at lower temperatures. The raw material acetic acid 132 may be mainly water.

[0054] In one embodiment, the ODH reactor effluent 104 is cooled in the cooler heat exchanger 128 with cooling water (for example, to a temperature in the range of 30°C to 80°C) to condense most of the water and acetic acid in the ODH reactor effluent 104. Therefore, since most of the water is condensed, the raw material acetic acid 132 discharged from the flash drum 130 in this embodiment may contain a considerable amount of water. In this way, the raw material acetic acid 132 may have a low concentration of acetic acid, such as less than 1% by weight (wt%). Depending on the embodiment and the temperature of the effluent 104 entering the flash drum 130, the acetic acid concentration in the raw material acetic acid 132 can be in the range of, for example, 0.3% by weight to 45% by weight.

[0055] The flash drum 130 discharges the raw material acetic acid 132 from its bottom. The raw material acetic acid 132 contains liquid acetic acid and liquid water. The flash drum 130 may have an outlet at its bottom for discharging the raw material acetic acid 132. The outlet may be a flanged or threaded nozzle connected to a conduit for discharging the raw material acetic acid 132 from the flash drum 130 into the conduit. The flash drum 130 can discharge the raw material acetic acid 132 through the conduit to the acetic acid unit 132, for example, to an extraction column in the acetic acid unit 132.

[0056] The raw material acetic acid 132 is processed in the acetic acid unit 134 to remove water 136 from the raw material acetic acid 132 and obtain acetic acid product 138, which is a co-product of ethylene production. The acetic acid product 138 may, for example, have at least 99% by weight of acetic acid. At least a portion of the removed water 136 can be recovered as water product 140. As described later (for example with respect to Figure 1A), the acetic acid unit 134 may include an extraction column (container) for injecting a solvent to remove acetic acid, a water stripper column (container) for processing the raffinate from the extraction column to recover water, and a solvent recovery column (container) for removing the solvent from the acetic acid discharged from the extraction column to obtain acetic acid product 138.

[0057] The flash drum 130 can discharge gas 142 overhead from the top of the flash drum 130. Gas 142 may include water vapor, residual acetic acid vapor, and other gases such as ethylene, carbon dioxide, carbon monoxide, unreacted ethane, and other gases. Other gases include, for example, relatively small amounts of methane or propane that entered the system 100 together with ethane gas 112 (for example, in the pipeline supply of ethane gas 112). The flash drum 130 may include an outlet at the top of the flash drum 130 for discharging gas 142. The outlet may be a flanged or threaded nozzle for connecting to a discharge conduit for discharging gas 142. Gas 142 can flow through the discharge conduit to an acetic acid scrubber 144, which is a container such as a tower or column.

[0058] The purpose of the acetic acid scrubber 144 may also be to scrub (remove) acetic acid and water from gas 142. The acetic acid and water removed from gas 142 may generally be the residue of acetic acid and water supplied from the effluent 104. By removing acetic acid from gas 142, the concentration of acetic acid in the process gas 148 is reduced, which may therefore lessen the metallurgical requirements of downstream treatment equipment such as the process gas compressor 158 (and thus lower metallurgical costs). The concentration of acetic acid in the process gas 148 may be, for example, less than 100 ppm.

[0059] The scrubbing fluid may be scrubbing water 146, which enters the upper part of the acetic acid scrubber 144 and flows downward through the acetic acid scrubber 144. The scrubber 144 may have an inlet, such as a nozzle, for receiving the scrubbing water 146. This nozzle may be, for example, a flanged or threaded connection coupled to an inlet conduit, which carries the incoming scrubbing water 146. A pump 160 can provide the power to drive the scrubbing water 146 into the acetic acid scrubber 144. The scrubbing water 146 supplied to the acetic acid scrubber 144 may include, for example, liquid water 154 from an acetic acid unit 134 and condensed water 156 from a downstream process gas compressor (PGC) 158. The condenser heat exchanger of the PCG 158 (including interstages in some examples) can condense the water in the process gas 148 flowing through the PCG 158 (compressed within the PCG 158).

[0060] Gas 142 from the flash drum 130 may enter the lower part of the scrubber 144 container and flow upward in a countercurrent to the scrubbing water 146 through the scrubber 144. The scrubber 144 may have an inlet (e.g., a nozzle) connected to an inlet conduit by flange or threading, the inlet conduit carrying the incoming gas 142. The acetic acid scrubber 144 may have packing or trays to provide a contact step between the gas 142 and the scrubbing water 146 for mass transfer of water vapor and acetic acid vapor from the gas 142 to the scrubbing water 146. The scrubber 144 may include random packing, ordered packing, trays, or any combination thereof.

[0061] The acetate scrubber 144 may discharge a process gas 148 (e.g., an overhead flow) for downstream treatment to recover ethylene products. The process gas 148 may contain ethylene, ethane, carbon dioxide, carbon monoxide, propane, and methane. The concentration of ethylene in the process gas 148 may be in the range of, for example, 10 mol% to 90 mol%. Generally, the process gas 148 is obtained by removing acetic acid vapor and water vapor from gas 142 within the scrubber 144 from gas 142. The process gas 148 can be discharged through an outlet nozzle located at the top of the scrubber 144, which is connected to a discharge conduit.

[0062] The scrubbing water 146, containing acetic acid vapor and water vapor removed from gas 142, can be discharged as a bottom flow (through the outlet nozzle at the bottom of the scrubber 144) into the ethane saturation tower 110 as recycled water 150. The recycled water 150 can flow into the ethane saturation tower 110 through a conduit. A recycled water pump 152 is positioned along the conduit to provide power to the flow of recycled water 150. The recycled water 150 can be combined with bottom liquid water 120 from the ethane saturation tower 110 and flow through a circulating water heater 118 as a supply of liquid water 116 to the saturation tower 110.

[0063] By supplying recycled water 150 to the ethane saturation tower 110, the water recirculation circuit (e.g., a closed circuit) in system 100 can be completed. The generated water 140 discharged from this circuit may contain water produced in the ODH reaction in the ODH reactor 102. Makeup water can be added to the circuit to account for losses or process malfunctions. Water integration can be achieved in system 100 by supplying water recovered from the effluent 104 (e.g., as recycled water 150) to dilute the mixed feed 108.

[0064] The process gas 148 discharged from the acetate scrubber 144 is processed by a downstream device 162 to extract ethylene from the process gas 148 as the product ethylene 164. The downstream device 162 may include the aforementioned PGC 158 (e.g., a mechanical compressor) to increase the pressure of the process gas 148. The compressed process gas may be processed to remove lighter components such as carbon monoxide and methane. The downstream device 162 may include a C2 splitter 166 to separate ethylene from ethane. The C2 splitter 166 may be a vessel that is a distillation column having a distillation tray.

[0065] In one embodiment, the ethylene production system 100 sends process gas 142 to a downstream device 162, but does not include the downstream device 162. Instead, the product of the ethylene production system 100 is process gas 148 containing ethylene. In another embodiment, the ethylene production system 100 includes a PGC compressor 158 that discharges process gas 148 as a product. In yet another embodiment, the ethylene production system 100 includes a downstream process device 162. Regarding the downstream process device 162, the PGC 158 is considered in the energy discussions or analyses of options 1 to 9, but typically the rest of the downstream device 162 is not considered.

[0066] An ODH reactor system or ODH reactor system plant may include the apparatus shown in Figure 1 (e.g., ethane saturated column 110, flash drum 130, acetic acid unit 134, acetic acid scrubber 144, etc.) with the downstream process equipment 162 removed. In some embodiments, an ODH reactor system or ODH reactor system plant may be characterized as having a PGC 158 but not having a splitter distillation column 166.

[0067] The ethylene production system 100 in Figure 1 and the subsequent ethylene production systems in Figures 2 to 9 may include a control system that facilitates or directs the operation of the ethylene production system, which may include the supply or discharge of flow (including flow rate) and associated control valves, control of operating temperature and operating pressure, and control of columns, drums, scrubbers, and heat exchangers. The control system may include a processor and memory that stores code (e.g., logic, instructions, etc.) executed by the processor to perform calculations and direct operations of the ethylene production system. The control system may be one or more control devices, or may include one or more. The processor (hardware processor) may be one or more processors, each processor may have one or more cores. The hardware processor may include a microprocessor, a central processing unit (CPU), a graphics processing unit (GPU), a controller card, a circuit board, or other circuitry. Examples of memory include volatile memory (e.g., cache and random access memory), non-volatile memory (e.g., hard drives, solid-state drives, read-only memory), and firmware. Examples of control systems include desktop computers, laptop computers, computer servers, programmable logic controllers (PLCs), distributed computing systems (DSCs), controllers, actuators, or control cards. A controller may be a component of code stored in memory and executed by a processor. The control system may include control modules and devices distributed throughout the field.

[0068] The control system can receive user input specifying setpoints for control devices or other control components within the ethylene production system. The control system typically includes a user interface for a human to input setpoints and other objectives or constraints into the control system. In some embodiments, the control system can calculate or otherwise determine the setpoints for the control devices. The control system may be communicatively coupled to a remote computing system that performs calculations and provides instructions including the setpoint values. During operation, the control system can facilitate the process of the ethylene production system. Again, the control system can receive user input or computer input specifying setpoints for control components within the system. The control system can determine, calculate, and specify the setpoints for the control devices. This determination can be at least in part based on operating conditions of the ethylene production system, including feedback information from sensors and transmitters, etc.

[0069] In some embodiments, a control room may be included that can serve as the center of activity, facilitating the monitoring and control of a process or facility. The control room may house a human-machine interface (HMI). The HMI is, for example, a computer running specialized software that provides a user interface for the control system. HMIs may vary by vendor and present a graphical version of a remote process to the user. There may be multiple HMI consoles or workstations, each offering varying degrees of data access. The control system may also, or alternatively, employ distributed local controls within the system (e.g., distributed controllers, local control panels).

[0070] Figure 1A shows an example of the acetic acid system 134 in Figure 1 (and subsequent figures). As described, the acetic acid system 134 receives raw material acetic acid 132 from a flash drum 130 or the like. In the illustrated embodiment, the acetic acid unit 134 includes an extraction column 170 that uses a solvent to remove acetic acid from the raw material acetic acid 132, a water stripper column 172 that processes the raffinate from the extraction column 170 to recover water, and a solvent recovery column 174 that removes the solvent from the acetic acid discharged from the extraction column 170 to obtain the acetic acid product 138. Again, as described, the acetic acid unit 134 receives raw material acetic acid 132, which may be mainly water.

[0071] In the illustrated embodiment, the raw material acetic acid 132 is supplied to the extraction column 170. The raw material acetic acid 132 is introduced at the top of the extraction column 170 and can flow downward through the extraction column 170.

[0072] The extraction column 170 is generally a container having a vertical orientation. The extraction column 170 may also be a liquid-liquid extraction column. The extraction column 170 may have packing (random or structured) or a tray (e.g., a sieve tray). If packing is used, the packing may be made of metal (e.g., stainless steel) or plastic. The extraction column 170 may include a movable internal structure (e.g., an impeller) to provide better contact between the liquid-liquid phases.

[0073] During the operation, the extraction column 170 uses solvent 176 to extract acetic acid from the starting material acetic acid 132. Solvent 176 may generally be immiscible with water and therefore typically does not remove a significant amount of water from the starting material acetic acid 132. Solvent 176 can be, for example, n-butanol, isobutanol, amyl alcohol, ethyl acetate, or methyl tert-butyl ether (MTBE). Solvent 176 is introduced at the bottom of the extraction column 170 and can flow upward through the column 170 in countercurrent with the starting material acetic acid 132 flowing downward through the extraction column 170. Solvent 176 removes (absorbs, extracts) acetic acid from the starting material acetic acid 132. Packing or trays and movable parts within the extraction column 170 can facilitate the transfer of acetic acid to the solvent 176.

[0074] The extract 178, which contains acetic acid (and a relatively small amount of water) removed (absorbed, extracted) from the solvent 176 and the raw material acetic acid 132, is discharged overhead from the extraction column 170 through an extract heater 180 (heat exchanger). The extract heater 180 heats the extract 178. The heating medium may be, for example, steam. The extract heater 180 may be a shell-and-tube heat exchanger, a plate heat exchanger, a plate-fin heat exchanger, or another type of heat exchanger. The extract 178 is sent to the solvent recovery column 174.

[0075] The extraction column 170 discharges the raffinate 184 as a bottom flow from the bottom of the extraction column 170. The raffinate 184 contains most or bulk (e.g., almost all) water from the starting material acetic acid 132. The raffinate 184 is mainly water. The raffinate 184 may also contain trace amounts of organic compounds (e.g., solvent 176, acetic acid, etc.).

[0076] The raffinate 184 is discharged from the extraction column 170 to the water stripper column 172 to recover the water (to increase its purity). The water stripper column 172 (container) is a distillation column including a distillation tray or packing and can be associated with a reboiler heat exchanger (or direct steam injection to the bottom) as a heat source. The water stripper column 172 may also be associated with an overhead condenser heat exchanger. A decanter can be used to separate the aqueous and solvent phases in the condensed overhead stream from the overhead condenser. The distillation column system may include a receiver container or reflux drum to receive the condensed liquid from the overhead condenser.

[0077] During operation, the water stripper column 172 separates trace amounts of organic compounds from the raffinate 184 and discharges the bottom flow containing the organic compounds as liquid water 186. The water stripper column 172 can discharge condensed water vapor and organic compounds from the top. A portion of the water 186 may be delivered as the aqueous product 140. Another portion 154 of the water 186 may be used as scrubbing water 146 for the acetate scrubber 144.

[0078] The solvent recovery column 174 receives the extract 178 from the extract heater 180. The solvent recovery column 174 may also be a distillation column that separates the solvent 176 from the extract 178 to obtain the acetic acid product 138. The separated solvent 178 may be sent to the extraction column 170. The distillation column is a vessel equipped with a distillation tray or packing and is operated using a reboiler heat exchanger and an overhead condenser heat exchanger (and a decanter for separating the aqueous and solvent phases).

[0079] The extract 178 can be introduced as a byfeed (e.g., top) into the solvent recovery column 174. The acetic acid product 138 may be a bottom flow discharged from the solvent recovery column 174. The solvent 176 can be discharged overhead from the solvent recovery column 174 and then condensed.

[0080] Figure 2 shows an ethylene production system 200 that is identical or similar to the ethylene production system 100 in Figure 1, but with the addition of an oxygen saturation tower 202 (oxygen gas saturation tower). Figure 2 can be characterized as Option 2. For explanations of the text, terminology, and reference numbers shown in Figure 2, please also refer to the explanation of Figure 1.

[0081] The oxygen saturation tower 202 and the ethane saturation tower 110 can share recycled water 150 from the acetate scrubber 144 as a source. A portion 204 of the recycled water 150 can be combined with bottom water 120 (via the recycled water pump 152) and supplied to the ethane saturation tower 110 as liquid water 116 through the circulating water heater 118. Another portion 206 of the recycled water 150 can be combined with bottom water 208 from the oxygen saturation tower 202 (via the recycled water pump 152) and supplied to the oxygen (O2) saturation tower 202 as liquid water 210 via the circulating water heater 212.

[0082] In the illustrated embodiment, which includes an oxygen saturation tower 202, the water load taken into the mixed feed 108 (for saturation) is shared between the two saturation towers 110 and 202. This may result in a lower water circulation rate and quality of LP steam demand in the circulating water heaters 118 and 212 compared to the circulating water heater 118 of option 1, and a lower temperature of the circulating water discharged from the circulating water heaters 118 and 212. See, for example, Table 1. Here, low-pressure 60 psig LP steam is used in option 2 compared to high-pressure 70 psig LP steam. Therefore, the temperature of the circulating water in option 2 will be lower than in option 1. The oxygen saturation tower 202 (oxygen feed saturation tower) can be a tray tower or a packed-bed tower.

[0083] The oxygen saturation tower 202 can receive oxygen gas 126 (supply) and supply saturated oxygen gas 214 (saturated with water) for the mixed feed 108 to the ODH reactor 102 vessel. The ethylene production system 100 may include an oxygen saturation tower 202 vessel (e.g., a column) for taking in water vapor into the oxygen gas 126 and discharging saturated oxygen gas 214 for the mixed feed 108.

[0084] In this embodiment, liquid water 210 can enter the upper part of the saturation column 202 and flow downward through the column 202. The column 202 may have an inlet (e.g., a nozzle) that is flanged or threaded to a conduit for transporting the inflow water 210. Oxygen gas 126 can enter the lower part of the saturation column 202 and flow upward through the column 202. The column 202 may have packing or trays to provide a contact step between the oxygen gas 126 and the water 210 in order to transfer water vapor into the oxygen gas 126. The column 202 may include random packing, structured packing, or column trays (e.g., sieve trays), or any combination thereof.

[0085] The liquid water 208 is discharged from the bottom of the oxygen saturation tower 202 (e.g., as a bottom flow) and can be circulated (recirculated) via a water circulation (recirculation) pump 216 (e.g., a centrifugal pump) as a water supply to the oxygen saturation tower 202. Thus, the oxygen saturation tower 202 can have a water recirculation loop. As described above, the bottom liquid water 208 is combined with a portion 206 of the recycled water 150 to obtain liquid water 210 which is introduced into the upper part of the oxygen saturation tower 202.

[0086] The feed liquid water 210 can be heated in the circulating water heater 212 with a heating medium such as steam (e.g., LP steam) to produce heated liquid water 210 that enters the oxygen saturation tower 202. The circulating water heater 212 is a heat exchanger such as a shell-and-tube heat exchanger or a plate-fin heat exchanger. Saturated oxygen gas 214 can be discharged overhead from the oxygen saturation tower 202 for supply to the ODH reactor 102. "Saturated" oxygen or "saturated" oxygen gas means that the oxygen gas is saturated with water (water vapor) and is therefore water-saturated. Saturated oxygen gas 214 contains water vapor but little to no liquid water.

[0087] Figure 3 shows an ethylene production system 300 identical or similar to the ethylene production system 200 in Figure 2, but equipped with an ethane cross exchanger 302 and an oxygen cross exchanger 304, and with the addition of relevant water for partial saturation. Figure 3 may also be labeled as Option 3. For explanations of the text, designations, and reference numbers shown in Figure 3, please also refer to the descriptions of Figures 1 and 2.

[0088] The inclusion of ethane cross exchanger 302 and oxygen cross exchanger 304 may be beneficial in reducing the LP steam demand in the circulating water heaters 118 and 212 of the saturated towers 110 and 202, respectively, due to significant heat recovery from the reactor effluent 104. Furthermore, heat recovery (for cooling) from the reactor effluent via cross exchangers 302 and 304 may also reduce the plant's cooling water demand (e.g., reducing the load on the cooling towers). Cross exchangers 302 and 304 may be heat exchangers such as plate (and fin) heat exchangers or shell-and-tube heat exchangers with heat sources and heat sinks on both sides, respectively.

[0089] During operation, the ethane cross exchanger 302 heats a mixture 306 of ethane gas 112 and recycled water 308. The recycled water 308 may be part of the recycled water 150 from the bottom of the acetate scrubber 144. The mixture 306 downstream of the ethane cross exchanger 302 (in its heated state) may be presented as partially saturated ethane supplied to the ethane saturation tower 110. Thus, instead of supplying ethane gas 112 directly to the ethane saturation tower 110 as shown in Figures 1 and 2, the ethane gas 112 is first partially saturated with recycled water 308 before being introduced into the ethane saturation tower 110.

[0090] The oxygen cross exchanger 304 heats the mixture 310 of oxygen gas 126 and recycled water 312. The recycled water 312 may be another portion of the recycled water 150 from the bottom of the acetate scrubber 144. The remaining 314 of the recycled water 150 can be supplied (as portions 204 and 206, respectively) to the ethane saturator 110 and the oxygen saturator tower 202, as shown. The mixture 310 downstream of the oxygen cross exchanger (in a heated state) can be shown as partially saturated oxygen supplied to the oxygen saturator tower 202 to saturate the oxygen gas with water. Thus, instead of supplying the oxygen gas 126 directly to the oxygen saturator tower 202 as shown in Figure 2, the oxygen gas 126 is first partially saturated with recycled water 312 before being introduced into the oxygen saturator tower 202.

[0091] The ethane cross exchanger 302 and the oxygen cross exchanger 304 may each be a shell-and-tube heat exchanger, a plate heat exchanger, a plate-fin heat exchanger, or another type of heat exchanger. The ethane cross exchanger 302 and the oxygen cross exchanger 304 can utilize the effluent 104 as a heating medium, either in series or in parallel, as shown.

[0092] In the illustrated embodiment, the ethane cross exchanger 302 and the oxygen cross exchanger 304 receive the effluent 104 downstream of the feed heat exchanger 124. A portion 316 of the effluent 104 is supplied to the ethane cross exchanger 302. The remaining portion 318 of the effluent 104 is supplied to the oxygen cross exchanger 304. The effluent 104 can be divided into portions 316 and 318, for example, via a pipe T-tube or other pipe fittings. Thus, the conduit carrying the effluent 104 can be discharged into two conduits, each carrying portions 316 and 318. A control valve (e.g., a flow control valve) may be located in one of the two conduits. Other arrangements or configurations for dividing the effluent 104 into portions 316 and 318 are also applicable.

[0093] Downstream, portions 316 and 318 of the effluent 104 combine to form an effluent 104 that is cooled by the ethane cross exchanger 302 and the oxygen cross exchanger 304 and moves forward. Portions 316 and 318 can be combined upstream of the cooler heat exchanger 128 (as indicated by arrow 320). The (cooled) effluent 104 can then flow through the cooler heat exchanger 128 to the flash drum 130 (for additional cooling).

[0094] By incorporating two parallel cross exchangers 302 and 304, the effluent is cooled, and therefore the demand for cooling water to cool the effluent 104 is reduced compared to options 1 and 2 (e.g., reducing the demand for cooling tower water in the cooler heat exchanger 128). Furthermore, by adding the two parallel cross exchangers 302 and 304, heat is recovered from the effluent 104 for feed saturation (e.g., for water saturation of ethane gas 112 and oxygen gas 126, and therefore for diluting the mixed feed 108 with water). Therefore, the steam consumption for feed saturation (e.g., LP steam in circulating water heaters 118 and 212) may be reduced compared to option 2. However, adding two parallel cross exchangers 302 and 304 between the ODH reactor 102 and the PGC 158 may result in a lower suction pressure in the PGC 158, and therefore a higher power consumption in the PGC 158 compared to options 1 and 2.

[0095] Figure 4 shows an ethylene production system 400 that is identical or similar to the ethylene production system 300 in Figure 3, but without the oxygen saturation tower 202. Figure 4 may also be labeled as Option 4. For explanations of the text, terminology, and reference numbers shown in Figure 4, please refer to the explanation of the previous figure.

[0096] Removing the oxygen (O2) saturated tower 202 could simplify the ethylene production system compared to option 3. However, the quality of the LP steam demand in the circulating water heater 118 of the ethane saturated tower 110 may be higher than in options 2 and 3.

[0097] The remaining 314 of the recycled water 150 can be supplied to the ethane saturator 110. The remaining portion 314 of the recycled water 150 may be equivalent to the portion 204 (Figures 2-3) excluding the portion 206 used for oxygen gas saturation or the oxygen saturation tower 202.

[0098] In Figure 4, as in Figure 3, the oxygen cross exchanger 304 heats the mixture 310 of oxygen gas 126 and recycled water 312. However, in Figure 4, the heated mixture 310 (partially saturated oxygen) is added to the conduit that carries saturated ethane 114 (instead of being supplied to the oxygen saturation tower 202 as in Figure 3).

[0099] Furthermore, compared to Figure 1, instead of directly adding oxygen gas 126 to saturated ethane 114 as in Figure 1, the oxygen gas 126 in Figure 4 is first partially saturated with recycled water 312 via an oxygen cross exchanger 304 before being introduced into the conduit that transports saturated ethane 114.

[0100] The heated mixture 310 (partially saturated oxygen) may be added to the saturated ethane 114 at a single addition point or at multiple addition points (e.g., 2 to 5 addition points). The heated mixture 310 can be added to the saturated ethane 114 upstream or downstream of the feed heat exchanger 124, or both. The combination of saturated ethane 114 and the mixture 310 (heated by the cross exchanger 304) can become the mixed feed 108 introduced into the ODH reactor vessel 102.

[0101] Figure 5 shows an ethylene production system 500 that is identical or similar to the ethylene production system 400 in Figure 4, but with the addition of a recycled water cross exchanger 502 for heating the remaining 314 of the recycled water 150 using the reactor effluent 104. Figure 5 may also be labeled as Option 5. For explanations of the text, terminology, and reference numbers shown in Figure 5, please also refer to the explanation of the previous figure.

[0102] The recycled water cross exchanger 502 heats the remaining portion 314 of the recycled water 150 supplied to the ethane saturation tower 110 (using the effluent 104 as a heating medium). In this way, the recycled water cross exchanger 502 preheats the recycled water to the ethane saturation tower 110 (ethane feed saturation tower). The recycled water cross exchanger 502 further increases heat recovery from the reactor effluent 104. The use of the recycled water cross exchanger 502 reduces both the steam demand for saturating the feed and the cooling water demand for cooling the reactor effluent 104 compared to option 4. Similar to cross exchangers 302 and 304, the recycled water cross exchanger 502 can be, for example, a plate (and fin) heat exchanger or a shell-and-tube heat exchanger (with a heat sink and heat source on each side). In the illustrated embodiment, the recycled water cross exchanger 502 is positioned downstream of the cross exchangers 302 and 304 and upstream of the cooler heat exchanger 128, and is operable along the flow of the effluent 104.

[0103] As explained, the recycled water 150 is the bottom flow discharged from the acetate scrubber 144. Portions 308 and 312 of the recycled water 150 are collected to partially saturate the ethane gas 112 and oxygen gas 126, respectively, as shown in Figure 4. However, the remaining recycled water 150 passes through the recycled water cross exchanger 502 during the process of being sent from the circulating water heater 118 to the ethane saturation tower 110 (before being sent) and is sent as the remainder 314.

[0104] As shown, the cross exchangers 302, 304, and 502 may be shell-and-tube heat exchangers, plate heat exchangers, plate-fin heat exchangers, or other types of heat exchangers. Furthermore, as is generally the case with the cross exchangers described herein, the system 500 may be configured to deliver the heating medium and the cooling medium through either side of the cross exchanger, respectively. For example, a cross exchanger as a shell-and-tube heat exchanger may be configured such that the heating medium (fluid 104 from cross exchanger 502) flows through the tubes (tube bundle) and the cooling medium (remaining recycled water 314 from cross exchanger 502) flows through the shell. Alternatively, the cross exchanger may be configured such that the heating medium flows through the tubes and the cooling medium flows through the shell.

[0105] Furthermore, as shown, by employing the recycled water cross exchanger 502, steam consumption for ethane saturation (e.g., LP steam in the circulating water heater 118) can be further reduced compared to Figure 4 (Option 4). The addition of the recycled water cross exchanger 502 may also further reduce the demand for cooling water in the cooler heat exchanger 128 for cooling the effluent 104 compared to Option 4. However, adding another heat exchanger through which the effluent 104 flows (the recycled water cross exchanger 502) may increase the pressure drop between the ODH reactor 102 and the PGC 158, potentially increasing the power demand by the PGC 158.

[0106] Figure 6 shows an ethylene production system 600 identical or similar to the ethylene production system 500 in Figure 5, but including an ethane saturated heat exchanger 602 and an oxygen (O2) saturated heat exchanger 604. Compared to Figure 5, the ethane saturated heat exchanger 602 is replaced by an ethane saturated tower 110. Figure 6 can be characterized as Option 6. For explanations of the text, designations, and reference numbers shown in Figure 6, please also refer to the description of the previous figure.

[0107] The ethane saturated heat exchanger 602 and the oxygen saturated heat exchanger 604 may, for example, be plate (and fin) heat exchangers or shell-and-tube heat exchangers, respectively. The heat sink (in this case, process flow) and the heat source (utility heating medium) may pass through either side of the heat exchanger. The process side and the utility side may be either side of the heat exchanger.

[0108] In the case of an ethane saturated heat exchanger 602, the heat sink (heated mixture 306 combined with a portion of recycled water 204) and the heat source (e.g., LP steam) can each flow through either side of the ethane saturated heat exchanger 602. In the case of an oxygen saturated heat exchanger 604, the heat sink (heated mixture 310 combined with a portion of recycled water 206) and the heat source (e.g., LP steam) can each flow through either side of the oxygen saturated heat exchanger 604.

[0109] The ethane saturated heat exchanger 602 replaces the ethane saturated tower 110 and its associated water circulation pump 122 and circulating water heater 118. The ethane saturated heat exchanger 602 is employed in place of the ethane saturated tower 110 to further heat the heated mixture 306, which is ethane gas partially saturated with water (recycled water), and then saturate it with water (recycled water). Thus, the ethane saturated tower 110 system, including the tower 110, water circulation pump 122, and circulating water heater 118, can be eliminated. In this way, option 6 may be simpler and more power-efficient compared to option 5.

[0110] As explained, the main inflow of recycled water for saturating the feedstock may be the overall recycled water 150, which is the bottom flow discharged from the acetate scrubber 144. In Figure 6, as done in Figures 4 and 5, portions 308 and 312 of the recycled water 150 are taken to partially saturate the ethane gas 112 and oxygen gas 126, respectively. The remaining 314 of the recycled water 150 flows through the recycled water cross exchanger 502, as in Figure 5, but in Figure 6, the heated remaining 314 is supplied as recycled water to the ethane saturator heat exchanger 602 and the oxygen saturator heat exchanger 604. In particular, portion 204 of the remaining 314 of the recycled water 150 is supplied to the ethane saturator heat exchanger 602. Portion 206 of the remainder 314 is supplied to the oxygen saturator heat exchanger 604.

[0111] This portion 204 is combined with the heated mixture 306 (ethane gas partially saturated with water) which is sent through the ethane saturated heat exchanger 602 to obtain saturated ethane 114. The ethane saturated heat exchanger 602 uses a heating medium (e.g., LP vapor) to heat the liquid-water portion 206 and evaporate it into steam, saturating the heated mixture 306 with water (e.g., completely saturating it) and discharging saturated ethane 114. As in the previous figure, the saturated ethane 114 is sent through the feed heat exchanger 124, enters the mixed feed 108, and enters the ODH reactor 102.

[0112] A portion 206 of the remaining 314 of the recycled water 150 is combined with a heated mixture 310 (oxygen gas partially saturated with water) in a path through the oxygen saturator heat exchanger 604. This mixed flow, heated within the oxygen saturator heat exchanger 604 (e.g., via LP steam), is discharged from the heat exchanger as saturated oxygen 214. This saturated oxygen 214 may be identical or similar to the saturated oxygen 214 discharged overhead from the oxygen saturation tower 202 in Figures 2-3. In Figure 6, the oxygen saturation tower 202 is not employed. Saturated oxygen 214 is oxygen gas saturated with water vapor (e.g., fully saturated). As shown in Figures 2-3, saturated oxygen 214 is added to saturated ethane 114, enters the mixed feed 108, and is introduced into the ODH reactor 102.

[0113] Figure 7 shows an ethylene production system 700 that is identical or similar to the ethylene production system 600 in Figure 6, but without the oxygen saturator heat exchanger 604. Figure 7 can be characterized as Option 7. For explanations of the text, designations, and reference numbers shown in Figure 7, please also refer to the explanation of the previous figure. Option 7 is not much different from Option 6, but is considered slightly simpler in that it does not have the oxygen saturator heat exchanger 604. The heating demands of Option 7 and Option 6 in the facility's supply steam system may be similar.

[0114] As shown, the ethylene production system 700 does not include an oxygen saturator heat exchanger 604 (Figure 6) that completely saturates the oxygen supply to be added to the saturated ethane 114. The system 700 also does not include an oxygen saturation tower 202 (Figures 2-3). Thus, as described with respect to Figure 4, the heated mixture 310 (oxygen gas 126 partially saturated with water) discharged from the oxygen cross exchanger 304 is added to the saturated ethane 114 for the mixed feed 108.

[0115] As shown in Figures 5 and 6, the remaining 314 of the recycled water 150 heated in the recycled water cross exchanger 502 is supplied to the ethane saturator heat exchanger 602 to fully saturate the mixture 306 (ethane gas 112 partially saturated with water) to obtain saturated ethane 114. In Figure 7, since there is no oxygen saturator heat exchanger 604, the remaining 314 of the recycled water 150 is not divided into portions 204 and 206 as in Figure 6.

[0116] Figure 8 shows an ethylene production system 800 that is identical or similar to the ethylene production system 700 in Figure 7, but is equipped with a dilution steam drum 802 and lacks the ethylene saturated heat exchanger 602. Figure 8 may also be labeled as Option 8. For explanations of the text, terminology, and reference numbers shown in Figure 8, please refer to the explanation of the previous figure.

[0117] The dilution steam (DS) drum 802 supplies dilution steam to completely saturate both ethane and O2 with water. Specifically, the DS drum 802 supplies dilution steam for addition to the heated mixture 306 (partially saturated ethane) to obtain saturated ethane 114. The DS drum 802 also supplies dilution steam for addition to the heated mixture 310 (partially saturated oxygen gas) to obtain saturated oxygen gas 214. As described, saturated oxygen gas 214 is added to saturated ethane 114 to become the mixed feed 108 supplied to the ODH reactor 102.

[0118] In Figure 8, as explained in Figures 4 to 7, portions 308 and 312 of the recycled water are used to partially saturate ethane gas 112 and oxygen gas 126 in the ethane cross exchanger 302 and oxygen cross exchanger 304, respectively. In Figure 8, the remaining 314 of the recycled water 150 is sent to the DS drum 802 through the recycled water cross exchanger 502. Thus, heat is recovered from the reactor effluent 104 to the DS drum 802 through the heating of the remaining 314 of the recycled water 150 in the recycled water cross exchanger 502.

[0119] The DS drum 802 is a container that can be oriented horizontally or vertically. The DS drum 802 may have a container inlet nozzle for receiving the remaining 314 of the recycled water 150 into the DS drum 802 container. During operation, the water level is maintained in the DS drum 802 via liquid level control or the like. Liquid level control may include a liquid level control valve provided in the discharge conduit from the bottom of the DS drum 802, a liquid level sensor provided in the container of the DS drum 802, an instrument transmitter that indicates the liquid level measured by the liquid level sensor to the control system, and control logic in the control system that controls the liquid level control valve to maintain the liquid level at a set point. The operating temperature of the DS drum 802 can be, for example, in the range of 135°C to 175°C.

[0120] During operation, liquid water flashes (evaporates) within the DS drum 802 and is discharged overhead as steam from the DS drum 802. Any steam (vapor) entering the DS drum 802 in the circulating (recirculating) water 810 is also discharged overhead as a discharged vapor stream. The vapor discharged overhead from the DS drum 802 is dilution vapor and may be saturated vapor (or at a temperature slightly above the saturation temperature). The DS drum 802 may have a container discharge nozzle on or above the top of the DS drum 802 to discharge saturated dilution vapor. Dilution vapor (e.g., saturated dilution vapor or near-saturation vapor) may be discharged into a conduit that flows through the superheater 804.

[0121] Before using the dilution vapor as a diluent, it can flow through a superheater 804. The superheater 804 may be a heat exchanger such as a shell-and-tube heat exchanger or a plate-fin heat exchanger. The superheater 804 uses steam (e.g., MP steam) as a heating medium to heat the dilution vapor above its saturation temperature to obtain superheated steam.

[0122] In the illustrated embodiment, the superheated dilution vapor is divided into two parts, 806 and 808, and each is introduced into two conduits. Part 806 of the superheated dilution vapor is added to the heated mixture 306 (partially saturated ethane) to form saturated ethane 114. For example, part 806 of the superheated dilution vapor may flow through a conduit downstream of the superheater 804 and be added (e.g., via a pipe T-tube or other pipe fitting) to the conduit carrying the heated mixture 306 from the ethane cross exchanger 302.

[0123] A portion of the superheated dilution vapor 808 is added to the heated mixture 310 (partially saturated oxygen gas) to obtain saturated oxygen gas 214. For example, a portion of the superheated dilution vapor 808 may flow through a conduit downstream of the superheater 804 and be added (for example, via a pipe T-tube or other pipe fitting) to a conduit that carries the heated mixture 310 from the ethane cross exchanger 304.

[0124] The liquid water 810 is discharged from the bottom of the DS drum 802 into the discharge conduit. The aforementioned level control valve may be located along the discharge conduit. As will be described later, the liquid water 810 may be recirculated back to the DS drum 802 (e.g., via a thermosiphon, pump, etc.).

[0125] In some embodiments, to prevent or reduce the accumulation of impurities (e.g., solids) within the DS drum 802, the liquid water 810 (or slip flow of liquid water 810) discharged from the DS drum 802 can be sent to a blowdown (e.g., sewer), as shown in reference numeral 816. Blowdown may occur intermittently.

[0126] Liquid water 810 is circulated back to the DS drum 802 (e.g., via a thermosiphon) and heated in the DS generator 812 within the circulation loop. Evaporation of water 810 may occur within the circulation loop, including the DS generator 812. Thus, the flow of water 810 within the circulation loop may be a two-phase flow of liquid water and steam (water vapor). Water 810 can return to the DS drum 802 through the DS generator 812. The DS generator 812 may be a heat exchanger such as a shell-and-tube heat exchanger or a plate-fin heat exchanger. The heating medium may be, for example, MP steam 814. In some embodiments, in addition to being the utility-side fluid of the heat exchanger, the MP steam 814 can be injected into the circulating water 810 in the DS generator 814.

[0127] The DS drum 802 may have an inlet nozzle for receiving circulating liquid water 810 through a conduit from the DS generator 812. Partial steam generation may also occur in the DS generator 812. As mentioned above, in certain embodiments, some evaporation of the water 810 may occur in the circulating piping and the DS generator 812. Thus, the circulating liquid water 810 may contain steam contained downstream of the DS generator 812, and therefore become a two-phase flow.

[0128] A dilution steam configuration like Option 8 is a direct technique of adding water (for dilution) to the feed (ethane and oxygen) to obtain a mixed feed 108. However, this technique of Option 8 may utilize steam with a higher feed saturation value than Options 1-7. For example, Option 8 can use MP steam 814 (in the DS generator 812) compared to the earlier options, for example, LP steam in the circulating water heater 118 for the ethane saturated tower. Nevertheless, Option 8 can recover a considerable amount of heat favorably from the reactor effluent 104. In practice, Option 8 may be a better option in terms of energy compared to Options 1 and 2.

[0129] Figure 9 shows an ethylene production system 900 that is identical or similar to the ethylene production system 800 in Figure 8, but without the ethane cross exchanger 302 and oxygen cross exchanger 304. Figure 9 may also be labeled as Option 9. For explanations of the text, names, and reference numbers shown in Figure 9, please also refer to the explanation of the previous figure.

[0130] A portion 806 of the superheated dilution vapor is added to the ethane gas 112 to obtain saturated ethane 114. This portion 806 is transported via a conduit and can be added, for example, to a conduit carrying the ethane gas 112. Pipe fittings (e.g., pipe T-joints) can be used to connect the two conduits. The flow rate of portion 806 in option 9 may be higher than that of portion 806 in option 8 because option 9 does not employ an ethane cross exchanger 302 into which recycled water is introduced into the ethane gas for dilution that results in partial saturation.

[0131] A portion of the superheated dilution vapor 808 is added to the oxygen gas 126 to obtain saturated oxygen gas 214. This portion 808 is transported through a conduit and can be added, for example, to a conduit transporting oxygen gas 126. Pipe fittings (e.g., pipe T-joints) can be used to connect the two conduits. As described, saturated oxygen gas 214 is added to saturated ethane 114 to obtain a mixed feed 108 that is supplied to the ODH reactor 102. The flow rate of portion 808 in option 9 may be higher than that of portion 808 in option 8 because option 9 does not employ an oxygen cross exchanger 304 into which recycled water is introduced into the oxygen gas for dilution that results in partial saturation.

[0132] Recycled water 150 (for example, as a bottom flow from the acetate scrubber 144) is supplied to the DS drum 802 through the recycled water cross exchanger 502. The recycled water cross exchanger 502 heats the recycled water 150 using the reactor effluent 104 as a heating medium. In this way, heat is beneficially recovered from the effluent 104 to the DS drum 802.

[0133] Option 9 employs a direct approach of diluting the mixed feed 108 with water. However, in practice, the use of MP steam may offset the heat recovery from the reactor effluent 104 for energy integration compared to Option 1.

[0134] To be understood, the vessels and heat exchangers described with respect to Figures 1 to 9 may have at least one inlet (e.g., a nozzle) which is flanged or threaded to an inlet conduit, and at least one outlet (e.g., a nozzle) which is flanged or threaded to an outlet conduit.

[0135] Two or more ODH reactors 102 can be used in series and / or parallel. Although the ODH reactor 102 is shown as a single-stage reactor in which all feed components (mixed feed 108) are added at the reactor inlet, the described process is applicable to other reactor configurations, including multi-stage reactors and reactors with multiple inter-stage feed additions.

[0136] The steam generated or utilized may be low-pressure (LP) steam (e.g., 150 psig or less), medium-pressure (MP) steam (e.g., in the range of 150 psig to 500 psig), high-pressure (HP) steam (e.g., 500 psig or more), or very high-pressure (VHP) steam (e.g., 1500 psig or more). Again, in the steam generator 106, the generation of HP steam or VHP steam is generally more valuable than the generation of MP steam or LP steam and therefore can improve the economics of the ethylene production system 100. Steam can have a variety of uses. The use of steam by consumers or customers receiving the steam may depend on the pressure or quality of the steam. In some embodiments, the higher the vapor pressure of the generated steam, the greater the versatility in integrating the steam within the facility or plant. For example, HP steam can be used to power a turbine attached to a compressor, while LP steam is typically used for heating purposes, etc. As described in some embodiments of feed dilution, MP steam, which is a more valuable steam than LP steam, can be used. Examples of sources for LP steam and MP steam include extraction turbines or pressure reducing valves for HP or VHP steam.

[0137] As shown, the ODH reactor 102 may be a fixed-bed reactor (e.g., a tubular fixed-bed reactor), a fluidized-bed reactor, a boiling-bed reactor, or a heat exchanger-type reactor. A fixed-bed reactor may have a cylindrical tube filled with catalyst pellets as the catalyst bed. During operation, the reactants flow through the bed and are converted into products. The catalyst in the reactor may be one large bed, several horizontal beds, several parallel-filled tubes, or multiple beds in their own shells.

[0138] A fluidized bed reactor may be a vessel that suspends a solid catalyst and passes a fluid through the solid granular catalyst (e.g., in the form of spheres or particles) at a rate sufficient to cause the solid catalyst to behave as if it were a fluid. In embodiments, the fluidized bed reactor may have a support for the catalyst. The support may be a porous structure or a distributor plate and is located at the bottom of the reactor. The reactants may flow upward through the support at a rate that fluidizes the catalyst bed (e.g., the catalyst rises and begins to swirl in a fluidized state). A recirculation mode operation is available for the fluidized bed reactor.

[0139] This technique may include maintaining the operating temperature of the ODH reactor 102 below 450°C, below 425°C, or below 400°C. Regarding operating pressure, the inlet pressure of reactor 102 may be below 80 pounds / square inch gauge (psig) or below 70 psig. The reactor inlet pressure of each reactor may be in the range of 1 psig to 80 psig, or 5 psig to 75 psig. Other operating conditions for reactor 102 in embodiments of reactor 102 as a tubular fixed-bed reactor include 200 hours. -1 ~25,000 hours -1 The gas time-space velocity (GHSV) may be in the range of 5 centimeters per second (cm / second), and the linear velocity range of the feed passing through the reactor may be at least 5 centimeters per second (cm / second).

[0140] Figure 10 is a flammability diagram 1000 of a mixture of ethane gas, oxygen gas (O2), and water vapor (steam). Water is a diluent acting as an inert component. The flammability diagram 1000 plots the flammability limit, expressed as the mole percent (mol%) of O2 in the mixture, against the inert concentration, which is the mole percent of water in the mixture. Curve (line) 1002 is the lower flammability limit (mol% O2) of the mixture as a function of the O2 concentration (mol% O2) against the inert concentration (mol% water). Curve (line) 1004 is the upper flammability limit of the mixture as a function of the O2 concentration above the inert concentration. The region between curves 1002 and 1004 can be represented as the flammability zone (flammability envelope) of the mixture of ethane, O2, and water. Curve (dashed line) 1006 is the O2 concentration in stoichiometric relation to the ethane concentration above the inert concentration. Finally, as shown in Diagram 1000, the flammable envelope is narrowed by the temperature and pressure, including the presence of a diluent (e.g., water). As explained, water can be added to the feed into the ODH reactor to narrow the flammable envelope of the feed in the feedline and within the ODH reactor (and to keep the feed outside the flammable envelope). In particular, the addition of water adjusts the concentrations of ethane and oxygen, keeping the mixture outside the flammable envelope.

[0141] The following are comments on implementing options similar to options 1-9. Firstly, this technique can target an O2 concentration 0.5 mol% to 6 mol% lower than the limiting oxygen concentration (LOC), for example. In other words, the target O2 mol% in the mixed feed to the ODH reactor can be, for example, the value obtained by subtracting a value (e.g., in the range of 0.5 mol% to 6 mol%) from the LOC in the mixed feed at a given temperature and pressure. This may make it easier for the feed to remain outside the flammable zone from the time mixing of oxygen gas and ethane begins in the feed conduit until the mixed feed is introduced into the ODH reactor.

[0142] Secondly, gradually adding O2 to the ODH reactor feed (including ethane) in the conduits that transport the feed (in other words, over multiple addition points) may reduce the chance or possibility of the feed suddenly and temporarily entering the flammable zone.

[0143] Thirdly, a closed-loop (or effectively closed-loop) water circulation system can be used to supply water for diluting the reactor feedstock. This could mean that the concentrated acetic acid (AA) mixture from the reactor effluent is processed in an AA unit to separate water from the AA mixture. Some of the separated water, along with condensate from the process gas compressor area, is used to further scrub AA in a scrubber tower (acetic acid scrubber). The water at the bottom of the tower is recycled to dilute the mixed feedstock to the ODH reactor. In contrast, the water produced from the AA unit can be used directly as a dilution water source. However, the collection of water from the bottom of the AA scrubber usually needs to be found or designated. Sending water from the bottom of the AA scrubber to the AA unit places a significant load on the AA unit. Sending water from the bottom of the AA scrubber to the sewer system places a load on the wastewater treatment system. Therefore, a closed-loop water system including water from the bottom of the AA scrubber is considered a useful technique for diluting the feedstock to the reactor. Finally, regarding the water mass balance with respect to the aqueous products discharged from the AA unit, the aqueous products can comprise at least the water produced in the ODH reaction within the ODH reactor.

[0144] Fourth, by utilizing an ethane saturator (e.g., a tower or heat exchanger), it may be possible to use a lower-temperature-quality source (e.g., LP steam) instead of the high-temperature-quality source (e.g., MP steam) commonly used in DS drum options. In this way, more power can be obtained by feeding high-pressure (HP) or very high-pressure (VHP) steam generated from the ODH reactor and boiler into the turbine and operating the plant's compressor. For example (the figures are just examples and may differ or vary), if 1000 kilograms (kg / hr) of VHP passes through the turbine and is extracted as LP steam, 145 kilowatts (kW) of power can be generated. On the other hand, if 1000 kg / hr of VHP passes through the turbine and is extracted as MP steam, 105 kW of power can be generated. This means that to obtain the same output as extracting 145 kW of extracted MP steam, approximately 40% more VHP steam is consumed than when extracting LP steam in this hypothetical example. The supply sources for LP steam and MP steam may include, for example, an extraction turbine or pressure reducing valve for HP or VHP steam.

[0145] Fifth, a significant heat demand for the ODH reactor system (which may include feed treatment and effluent treatment) lies in the feed dilution region. A considerable amount of heat is required to evaporate the large volume of water added to the mixed feed. In addition, considerable cooling capacity is required to cool and condense the water added from the reactor effluent. In embodiments, thermal integration between the feed dilution system and reactor effluent cooling can advantageously reduce the load on the steam and cooling tower systems within the ODH reactor plant.

[0146] Sixth, using a heat exchanger (e.g., options 6 and 7) to saturate the feed without using a saturation tower may be a beneficial energy approach. Like saturation towers, saturation heat exchangers may utilize low-value heat sources (e.g., LP steam). However, feed saturation with a saturation heat exchanger can be achieved without pumping the relatively large flow rates (e.g., 10,000 mg per hour) of water (circulating water) required for a power-intensive saturation tower.

[0147] Finally, using a dilution steam drum allows for dilution using the simplest and most straightforward technique and approach among options 1-9. However, using a dilution steam drum (e.g., options 8 and 9) requires the use of a more valuable heat source, such as MP steam, for dilution compared to the other options.

[0148] Options 1-9 generally allow for a comparison of the energy integration of heat recovery from cooling of the ODH reactor effluent and the saturation of the ODH reactor feedstock considering acetic acid recovery. Table 1 shows the simulation results for Options 1-9 considering energy integration. In Table 1, Option 1 is used as the basic case for comparison. In other words, Options 2-9 can be compared to Option 1 as the basic line case.

[0149] Process simulations were performed using AspenPlus® V10. The SR-POLAR equation of state was used for the simulations. In the simulations, the feed inlet temperature to ODH reactor 102 (mixed feed 108) was maintained below 310°C at 465 kilopascals (kPa), and the oxygen concentration in mixed feed 108 (MIXED-FD) to ODH reactor 102 was targeted at 10 vol% to stay outside the flammable zone. The oxygen / ethane molar ratio in the mixed feed 108 stream was 0.62. The total water content of ODH reactor 102 was 74 vol%, requiring heating to evaporate the water before ODH reactor 102 and cooling to condense the water after ODH reactor 102. Table 1 shows the impact of Options 2-9 on heating, cooling, and power compared to Option 1, based on various energy integration modes and strategies. Other aspects of this technology are outside the scope of these example results.

[0150] [Table 1]

[0151] The following are examples of comments based on process simulations and the results shown in Table 1.

[0152] Option 1 uses a large volume of water circulation and a large volume of LP steam at 70 psig to dilute the mixed feed. Option 1 also uses a large volume of cooling water to cool the reactor effluent.

[0153] Option 2 has two saturation towers, but compared to Option 1, the water circulation in each saturation tower is less, so the steam output is the same but only 60 psig. However, Option 2 has a relatively higher cooling water demand than Option 1.

[0154] Option 3 has two saturated towers but also a heat recovery mode from reactor effluent. Compared to Option 1, Option 3 uses 60 psig of LPG. However, Option 3 does not significantly impact the water cycle. Option 3's LPG demand is 31% lower than Option 1, and its cooling water demand is 21% lower.

[0155] Option 4 yields relatively similar energy results to Option 3, but Option 3 is simpler and more straightforward because it uses one saturation tower instead of two (one for the ethane feed). However, because 70 psig of LPG steam is used for feed saturation, water circulation is reduced compared to Option 3.

[0156] Option 5 includes an additional heat exchanger compared to Option 4. The additional heat exchanger preheats the recycled water in the ethane saturated tower compared to Option 4. LP steam demand was reduced by 37% compared to Option 1, and cooling water demand was reduced by 29% compared to Option 1.

[0157] Option 6 uses two heat exchangers to fully saturate the supply of ethane and oxygen to 60 psig of LPG. This generally eliminates the need for a saturation tower and its associated tower water circulation pump. The amount of LPG required is reduced by 37% compared to Option 1, and the cooling water demand is reduced by 25% compared to Option 1.

[0158] Option 7 uses one heat exchanger to completely saturate the ethane feed. Therefore, the heat exchanger may be larger than the heat exchanger used for partial saturation of the ethane or the subsequent heat exchanger used for complete saturation of the ethane, compared to Option 6. However, using a heat exchanger to completely saturate the ethane feed with water means that the overall equipment is smaller compared to employing an ethane saturation tower to completely saturate the ethane. The amount of LPG required was reduced by 37% compared to Option 1, and the cooling water demand was reduced by 29% compared to Option 1.

[0159] Option 8 is one of the simplest methods for diluting the mixed feed using a dilution steam generation system. This used 200 psig of MP steam. MP steam demand was reduced by 34% compared to LP steam in Option 1, and cooling demand was reduced by 24% compared to Option 1.

[0160] Option 9 can be characterized as the simplest technique among Options 1-9 for diluting the mixed feed. Option 9 is similar to Option 8, but removes two partially saturated substances, ethane and oxygen feed, from the reactor effluent. MP steam requirements are 20% lower than Option 1 (LP steam), and cooling water demand is 12% lower compared to Option 1.

[0161] Figure 11 shows a method 1100 for producing ethylene. In block 1102, the method includes dehydrogenating ethane to ethylene via an ODH catalyst in the presence of oxygen in an ODH reactor. The ODH reactor is, for example, a fixed-bed reactor or a fluidized-bed reactor. Acetic acid may be produced in the ODH reactor as a byproduct of the ODH reaction that dehydrogenates ethane to ethylene.

[0162] In block 1104, the method includes discharging effluent from the ODH reactor. The effluent contains ethylene and water, and may also contain acetic acid, carbon dioxide, carbon monoxide, and unreacted ethane. In some embodiments, the heat from the effluent can be used to heat water (e.g., boiler feedwater) in a heat exchanger to generate steam for consumption in a facility having an ODH reactor.

[0163] In block 1106, the method includes supplying a feed containing ethane to the ODH reactor. The ethane may be ethane gas supplied from the feed pipeline, or recycled ethane from a downstream C2 splitter, etc. The ethane is liquid ethane supplied from the feed pipeline, which evaporates to ethane gas. As used herein, the term ethane generally means ethane gas. As described later (block 1110), water (e.g., recycled water) can be added to the ethane gas to dilute the feed with water. In some embodiments, the addition of water may cause the ethane gas to become saturated with water.

[0164] In block 1108, the method includes adding oxygen (O2 gas) to an ethane-containing feed to obtain a mixed feed for the ODH reactor. As used herein, the term oxygen generally means O2 gas. The oxygen may be added at a single point of addition to the conduit carrying the ethane-containing feed, or at multiple points of addition to the conduit carrying the ethane-containing feed. In some embodiments, as described later (block 1110), water (e.g., recycled water) may be added to the oxygen to dilute the feed with water before adding the oxygen to the feed. The mixed feed for the reactor contains ethane gas and oxygen gas. The mixed feed may contain water added for feed dilution (block 1110).

[0165] In block 1110, the method includes recovering water from the effluent as recycled water in order to dilute the feed to the ODH reactor with recycled water. As described (block 1106), the feed contains ethane. Diluting the feed also includes adding recycled water to the ethane. Diluting the feed includes adding recycled water to the oxygen added to the feed (block 1108). By recovering water from the effluent and adding it to the feed, the amount of water consumed in the production of ethylene can be reduced. In other words, if water is not recovered from the effluent for feed dilution, it may be necessary to consume external water for feed dilution. Recovery of water from the effluent for feed dilution can, in some embodiments, provide a substantially closed circulation of water between the effluent and the feed.

[0166] Recovering water from the effluent may involve condensing the water and acetic acid in the effluent by passing it through a heat exchanger using cooling water as a cooling medium. The condensed water and condensed acetic acid can be separated from the remaining effluent (gas) in a flash drum or similar device. The condensed water and condensed acetic acid can be combined and labeled as raw material acetic acid. The remaining effluent (gas) may contain ethylene, carbon dioxide, carbon monoxide, and unreacted ethane. The gas can be scrubbed in an acetic acid scrubber (or similar tower) to remove small amounts of acetic acid vapor and water vapor from the gas. The scrubbed gas may be sent as a process gas for further treatment to recover ethylene as an ethylene product (block 1114). The raw material acetic acid can be treated to obtain acetic acid products, similar to the scrubbing water for the acetic acid scrubber. The bottom flow from the acetic acid scrubber (or similar tower) may become recycled water used for feed dilution.

[0167] Adding recycled water to a feedstock for feedstock dilution may include adding recycled water to ethane upstream of oxygenation to the feedstock, either in the conduit, in the ethane saturated tower, or both; or adding recycled water to oxygen upstream of oxygenation to the feedstock, either in the conduit, in the oxygen saturated tower, or both; or any combination thereof. Adding recycled water to a feedstock for feedstock dilution may include evaporating recycled water in a steam dilution drum to obtain dilution steam for addition to the feedstock. Adding recycled water to a feedstock for feedstock dilution may include adding recycled water to ethane as dilution steam upstream of oxygenation to the feedstock; or adding recycled water to oxygen as dilution steam upstream of oxygenation to the feedstock; or any combination thereof.

[0168] In block 1112, the method includes recovering heat from the effluent to process the feed. For examples of feed, see above for blocks 1106 and 1108. Processing the feed includes heating the feed. The feed can be heated in a heat exchanger (cross exchanger, etc.) using the effluent as a heating medium. Thus, heat is recovered from the effluent and transferred to the feed liquid in the heat exchanger.

[0169] The processing of the feedstock includes water dilution of the feedstock (e.g., block 1110). Recovering heat from the effluent to perform water dilution may include heating the recycled water with heat from the effluent, such as in a cross exchanger. In some embodiments, recycled water (e.g., not heated by the effluent) is added to ethane to obtain a mixture that is heated (e.g., in a heat exchanger) with heat from the effluent for water dilution. In some embodiments, recycled water (e.g., not heated by the effluent) is added to oxygen to obtain a mixture that is heated (e.g., in a heat exchanger) using the effluent. In certain embodiments, adding recycled water to a feedstock containing ethane includes adding recycled water to oxygen added to the feedstock, and recovering heat from the effluent to perform water dilution includes heating the mixture of recycled water and oxygen added to the feedstock with heat from the effluent.

[0170] By recovering the heat used to process the feedstock, energy consumption during ethylene production can be reduced. For example, heating the feedstock using the effluent avoids heating it with steam, thereby reducing the energy consumption associated with steam use. Furthermore, heating recycled water (or a mixture containing recycled water) using the effluent avoids heating the recycled water or mixture with steam, thus avoiding the energy consumption associated with using steam to heat the recycled water.

[0171] In block 1114, the method includes processing the process gas described in block 1110. The processing includes increasing the pressure of the process gas, for example, by using a process gas compressor. The processing also includes removing light components (such as CO) from the process gas. The processing also includes separating ethylene from ethane in the process gas using a C2 splitter (distillation column), for example. The processing of the process gas yields an ethylene product for distribution or further processing.

[0172] One embodiment includes a method for producing ethylene. This method includes the steps of: adding water to ethane to obtain a mixture; passing the mixture through a feed heat exchanger and heating the mixture using effluent from an oxidative dehydrogenation (ODH) reactor; and adding oxygen to the mixture to obtain a mixed feed for the ODH reactor. This method includes the steps of dehydrogenating ethane to ethylene via an ODH catalyst in the presence of oxygen in the ODH reactor, and discharging effluent from the ODH reactor, the effluent containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and unreacted ethane. This method may also include introducing the mixed feed into the ODH reactor, where the water added to the ethane includes recycled water from the treatment of effluent, and the mixture upstream of the feed heat exchanger contains ethane saturated with water. The step of adding water to ethane may also include adding water to ethane in an ethane saturation tower. In this case, the water to be added to ethane may be heated in a cross-exchanger using effluent before being added to ethane in the ethane saturation tower. The step of adding water to ethane may further include adding water to ethane in a conduit upstream of a heat exchanger upstream of the ethane saturated tower, where the heat exchanger is a cross-exchanger that utilizes the effluent as a heating medium.

[0173] The step of adding water to ethane may include adding water to ethane in a conduit upstream of the heat exchanger, and the heat exchanger is a cross exchanger that uses the effluent as a heating medium. In this case, the water may be heated in a second cross exchanger using the effluent before adding water to ethane in the conduit.

[0174] The step of adding water to ethane may include adding dilution steam to a conduit that transports ethane from a dilution steam drum. In this case, the method may include heating the water in a cross exchanger using the effluent before introducing the water into the dilution steam drum. The step of adding water to ethane may further include adding water to a conduit that transports ethane upstream of a heat exchanger upstream of the ethane that receives the dilution steam, the heat exchanger being a cross exchanger that utilizes the effluent as a heating medium.

[0175] This method may include adding water to the oxygen before adding oxygen to the mixture, adding oxygen to the mixture may include adding oxygen to the conduit that carries the mixture, adding water to the oxygen may include adding water to the conduit that carries oxygen upstream of the heat exchanger, or adding water to the oxygen in the oxygen saturation tower, or a combination thereof, and the heat exchanger is equipped with a cross exchanger that utilizes the effluent as a heating medium. Adding water to the oxygen may also include adding dilution steam to the conduit that carries oxygen from a dilution steam drum.

[0176] Another embodiment relates to a method for producing ethylene, comprising the steps of: dehydrogenating ethane to ethylene via an ODH catalyst in the presence of oxygen in an ODH reactor, thereby forming acetic acid in the ODH reactor; and discharging an effluent from the ODH reactor containing ethylene, acetic acid, and water. This method includes separating the effluent into gas and raw material acetic acid in a flash drum, the gas containing ethylene, water, acetic acid, ethane, carbon dioxide, and carbon monoxide, and the raw material acetic acid containing acetic acid and water. This method includes removing acetic acid and water from the gas in an acetic acid scrubber vessel, and utilizing the bottom flow discharged from the acetic acid scrubber vessel as recycled water for diluting the feed to the ODH reactor. This method may also include heating the recycled water in a cross-exchanger using the effluent. The bottom flow from the acetic acid scrubber as recycled water may contain acetic acid in addition to water. The step of utilizing the bottom flow as recycled water for diluting the feed to the ODH reactor may include adding the recycled water to ethane. In this case, adding recycled water to ethane may include adding recycled water to ethane in an ethane saturation tower, or adding recycled water to a conduit transporting ethane upstream of the cross exchanger, or a combination thereof, and the cross exchanger utilizes the effluent as a heating medium. The process of using the bottom flow as recycled water to dilute the feed to the ODH reactor may include adding recycled water to oxygen in an oxygen saturation tower, or adding recycled water to oxygen in a conduit upstream of the cross exchanger, or a combination thereof, and the cross exchanger utilizes the effluent as a heating medium.

[0177] Another embodiment is an ethylene production system comprising an oxidative dehydrogenation (ODH) reactor having an ODH catalyst for dehydrogenating ethane to ethylene and discharging an effluent containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and ethane. The ethylene production system comprises a flash drum for separating the effluent from the ODH reactor into gas and feedstock acetic acid, the gas containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and ethane, and the feedstock acetic acid containing acetic acid and water. The ethylene production system comprises an acetic acid scrubber vessel for removing acetic acid and water from the gas and discharging the bottom flow as recycled water for diluting the feedstock to the ODH reactor, the bottom flow containing acetic acid and water. The ethylene production system may also comprise a cross exchanger for heating the recycled water with the effluent, and / or a cross exchanger for receiving a mixture of recycled water and ethane and heating this mixture with the effluent. The ethylene production system may also comprise a cross exchanger for receiving a mixture of recycled water and oxygen and heating the mixture with the effluent for feed to the ODH reactor.

[0178] The ethylene production system may include an ethane saturation tower for receiving recycled water and adding it to ethane for supply to the ODH reactor. In this case, the ethylene production system may include a cross exchange located upstream of the ethane saturation tower for heating the recycled water using the effluent before adding the recycled water to the ethane in the ethane saturation tower. In one embodiment, the ethylene production system may include a cross exchange located upstream of the ethane saturation tower for heating a mixture of recycled water and ethane using the effluent, and a conduit for transporting the mixture heated by the cross exchange to the ethane saturation tower, wherein the ethane saturation tower receiving the recycled water is composed of an ethane saturation tower receiving the mixture, and the ethane saturation tower for adding the recycled water to ethane is composed of an ethane saturation tower for adding the mixture to ethane received separately from the mixture in the ethane saturation tower. The ethylene production system may also include an oxygen saturation tower for receiving recycled water and adding it to oxygen for supply to the ODH reactor.

[0179] The ethylene production system may include a steam dilution drum for receiving and evaporating recycled water to produce dilution steam for supply to the ODH reactor, for adding dilution steam to ethane, or to oxygen, or a combination thereof. In this case, the ethylene production system may include a cross exchanger located upstream of the steam dilution drum, for heating the recycled water with the effluent before introducing the recycled water into the steam dilution drum.

[0180] Energy consumption during ethylene production can be reduced by recovering heat from the effluent to process the feed. Water consumption during ethylene production can be reduced by recovering water from the effluent to add to the feed. The process of recovering heat from the effluent to process the feed may include heating the feed using heat from the effluent. The process of recovering heat from the effluent to process the feed may include heating the feed in a heat exchanger using the effluent as a heating medium.

[0181] The process of recovering water from the effluent may include condensing the water and acetic acid in the effluent to obtain condensed water and condensed acetic acid, and separating the raw acetic acid from the effluent as condensed water and condensed acetic acid to obtain a gas containing ethylene, carbon dioxide, carbon monoxide, and unreacted ethane from the effluent. Furthermore, the process of recovering water from the effluent may include processing the raw acetic acid to obtain an acetic acid product and scrubbing water, wherein the scrubbing water is for use in an acetic acid scrubber to remove acetic acid from the gas, and the recycled water includes or is the bottom flow discharged from the acetic acid scrubber.

[0182] Adding recycled water to a feed containing ethane may include adding recycled water to the ethane before adding oxygen to the feed, or adding recycled water to the oxygen before adding oxygen to the feed, or a combination thereof. Adding recycled water to a feed containing ethane may include adding recycled water to the ethane in an upstream ethane saturation tower where oxygen is added to the feed, or adding recycled water to the oxygen in an oxygen saturation tower before adding oxygen to the feed, or a combination thereof.

[0183] Adding recycled water to a feed containing ethane may include adding recycled water to the ethane as dilution steam upstream of adding oxygen to the feed, or adding recycled water to a feed containing ethane may include adding recycled water to oxygen as dilution steam upstream of adding oxygen to the feed, or a combination thereof. Adding recycled water to a feed containing ethane may also include evaporating the recycled water in a steam dilution drum to obtain dilution steam for addition to the feed.

[0184] Processing the feed may include diluting the feed with water. In this case, recovering heat from the effluent to dilute the feed may include heating the recycled water with heat from the effluent. Adding recycled water to a feed containing ethane may include adding recycled water to the ethane to obtain a mixture, and recovering heat from the effluent to dilute the feed may include heating the mixture with heat from the effluent. Adding recycled water to a feed containing ethane may include adding recycled water to the oxygen added to the feed, and recovering heat from the effluent to dilute the feed may include heating the mixture of recycled water and the oxygen added to the feed with heat from the effluent.

[0185] Another embodiment is a method for producing ethylene, comprising the step of discharging effluent (containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and unreacted ethane) from an ODH reactor that dehydrogenates ethane to ethylene. This method includes the step of diluting the feed containing ethane for the ODH reactor with water. This dilution includes adding recycled water to the ethane. This method includes the step of recovering water from the effluent to obtain recovered water as recycled water for dilution. This method includes the steps of passing the feed downstream of the dilution through a feed heat exchanger and heating the feed with the effluent, and adding oxygen to the feed to obtain a mixed feed for the ODH reactor. The dilution step may further include adding recycled water to the oxygen. This method may include recovering heat from the effluent for dilution. Recovering heat from the effluent for dilution may include heating recycled water in a heat exchanger using the effluent as a heating medium. Recovering heat from the effluent for water dilution may include heating a mixture of ethane and recycled water in a heat exchanger using the effluent as a heating medium, or heating a mixture of oxygen and recycled water in a heat exchanger using the effluent as a heating medium, or both.

[0186] While many embodiments have been described, it will be understood that various modifications can be made without departing from the spirit and scope of this disclosure. [Industrial applicability]

[0187] This disclosure relates to a method and system for producing ethylene by oxidative dehydrogenation. The invention described in the original claims of this application is as follows: [Section 1] A method for producing ethylene, The process involves adding water to ethane to obtain a mixture, The process involves flowing the mixture through a feed heat exchanger and heating the mixture using the effluent from an oxidative dehydrogenation (ODH) reactor, A step of adding oxygen to the mixture to obtain a mixed feed for the ODH reactor, A process of dehydrogenating ethane to ethylene via an ODH catalyst in the presence of oxygen in an ODH reactor, A process of discharging effluent containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and unreacted ethane from the ODH reactor, Methods that include... [Section 2] A method according to item 1, comprising introducing a mixed feed into an ODH reactor, wherein the water added to the ethane includes recycled water from the treatment of the effluent, and the mixture upstream of the feed heat exchanger includes ethane saturated with water. [Section 3] The method according to claim 1, wherein the step of adding water to ethane includes adding water to ethane in an ethane saturated tower. [Section 4] The method according to claim 3, comprising heating the water to be added to the ethane in a cross exchanger using the effluent before adding water to the ethane in an ethane saturated tower. [Section 5] The method according to claim 3, wherein the step of adding water to ethane further includes adding water to ethane in a conduit upstream of a heat exchanger upstream of an ethane saturated tower, and the heat exchanger comprises a cross exchanger that utilizes the effluent as a heating medium. [Section 6] The method according to item 1, wherein the step of adding water to ethane includes adding water to ethane in a conduit upstream of the heat exchanger, and the heat exchanger comprises a cross exchanger that utilizes the effluent as a heating medium. [Section 7] The method according to claim 6, comprising heating the water in a second cross-exchange using the effluent before adding water to the ethane in the conduit. [Section 8] The method according to claim 1, wherein the step of adding water to ethane includes adding dilution steam to a conduit that transports ethane from a dilution steam drum. [Section 9] The method according to item 8, comprising heating the water in a cross exchanger with the effluent before introducing the water into a dilution steam drum. [Section 10] The method according to claim 8, wherein the step of adding water to ethane further includes adding water to a conduit that transports ethane upstream of a heat exchanger upstream of the ethane that receives dilution vapor, the heat exchanger comprising a cross exchanger that utilizes the effluent as a heating medium. [Section 11] The method according to claim 1, comprising adding water to oxygen before adding oxygen to the mixture, and the addition of oxygen to the mixture comprising adding oxygen to a conduit that carries the mixture. [Section 12] The method according to item 11, wherein adding water to oxygen includes adding water to a conduit that transports oxygen upstream of a heat exchanger, or adding water to oxygen in an oxygen saturation tower, or a combination thereof, and the heat exchanger comprises a cross exchanger that utilizes effluent as a heating medium. [Section 13] The method according to item 11, wherein adding water to oxygen includes adding dilution steam to a conduit that carries oxygen from a dilution steam drum. [Section 14] A method for producing ethylene, A step of dehydrogenating ethane to ethylene via an oxidative dehydrogenation (ODH) catalyst in the presence of oxygen in an ODH reactor, wherein acetic acid is formed in the ODH reactor. A process for discharging effluent containing ethylene, acetic acid, and water from the ODH reactor, A process for separating effluent into gas and raw material acetic acid in a flash drum, wherein the gas contains ethylene, water, acetic acid, ethane, carbon dioxide, and carbon monoxide, and the raw material acetic acid contains acetic acid and water. A process of removing acetic acid and water from the gas in an acetic acid scrubber container, A process in which the bottom flow discharged from the acetic acid scrubber container is used as recycled water to dilute the feed for the ODH reactor, Methods that include... [Section 15] The method according to item 14, comprising heating the recycled water in a cross-exchanger using the spilled material. [Section 16] The method according to claim 14, wherein the bottom flow contains water and acetic acid, and the step of using the bottom flow as recycled water to dilute the feed to the ODH reactor includes adding the recycled water to ethane. [Section 17] The method of paragraph 16, wherein adding recycled water to ethane includes adding recycled water to ethane in an ethane saturated tower, or adding recycled water to a conduit that transports ethane upstream of a cross exchanger, or a combination thereof, wherein the cross exchanger utilizes the effluent as a heating medium. [Section 18] The method according to item 14, wherein the step of using the bottom flow as recycled water to dilute the feed to the ODH reactor includes adding recycled water to oxygen in an oxygen-saturated tower, or adding recycled water to oxygen in a conduit upstream of a cross exchanger, or a combination thereof, and the cross exchanger utilizes the effluent as a heating medium. [Section 19] An oxidative dehydrogenation (ODH) reactor comprising an ODH catalyst for dehydrogenating ethane to ethylene and discharging effluent containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and ethane, A flash drum for separating effluent from an ODH reactor into gas and raw material acetic acid, wherein the gas contains ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and ethane, and the raw material acetic acid contains acetic acid and water. An acetic acid scrubber vessel for removing acetic acid and water from a gas and discharging the bottom flow as recycled water for diluting the feed to the ODH reactor, wherein the bottom flow contains acetic acid and water, An ethylene production system equipped with the following features. [Section 20] The system according to paragraph 19, comprising a cross exchanger for heating recycled water using spillage. [Section 21] The system according to paragraph 19, comprising an ethane saturation tower for receiving recycled water and adding the recycled water to ethane for supply to the ODH reactor. [Section 22] The system as described in paragraph 21, which is located upstream of the ethane saturation tower and includes a cross exchanger for heating the recycled water with the effluent before adding the recycled water to the ethane in the ethane saturation tower. [Section 23] The system described in item 21, Located upstream of the ethane saturation tower, it includes a cross-exchanger for heating a mixture of recycled water and ethane using the effluent, A conduit for transporting the mixture heated by the cross exchange to the ethane saturation tower, Equipped with, A system in which an ethane saturation tower that receives recycled water is composed of an ethane saturation tower that receives a mixture, and an ethane saturation tower that adds recycled water to ethane is composed of an ethane saturation tower that adds the mixture to ethane received separately from the mixture within the ethane saturation tower. [Section 24] The system according to paragraph 19, comprising a cross exchanger for receiving a mixture of recycled water and ethane and heating the mixture using the effluent. [Section 25] The system described in paragraph 19, comprising an oxygen saturation tower for receiving recycled water and adding the recycled water to the oxygen supplied to the ODH reactor. [Section 26] The system according to paragraph 19, comprising a cross exchanger for receiving a mixture of recycled water and oxygen and heating the mixture with the effluent for supply to an ODH reactor. [Section 27] The system according to item 19, comprising a steam dilution drum for receiving and evaporating recycled water to produce dilution steam for supply to an ODH reactor, for adding dilution steam to ethane, or to oxygen, or a combination thereof. [Section 28] The system according to paragraph 27, further comprising a cross exchanger located upstream of the steam dilution drum for heating the recycled water using the effluent before introducing the recycled water into the steam dilution drum. [Section 29] A method for producing ethylene, A process of dehydrogenating ethane to ethylene via an oxidative dehydrogenation (ODH) catalyst in the presence of oxygen in an ODH reactor, A process of discharging effluent containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and unreacted ethane from the ODH reactor, A process to recover heat from the effluent in order to process the feed containing ethane for the ODH reactor, The process involves recovering water from the effluent as recycled water for adding to the supply when diluting it with water, A step to obtain a mixed feed containing ethane and oxygen for an ODH reactor, comprising adding oxygen to the feed, wherein the mixed feed contains water recovered as recycled water from the effluent, and the recycled water is added to the feed. Methods that include... [Section 30] The method according to claim 29, wherein the step of recovering heat to process the feed reduces energy consumption in the production of ethylene, and the step of recovering water to be added to the feed reduces water consumption in the production of ethylene. [Section 31] The method according to paragraph 29, wherein the step of recovering heat from the spill for processing the feed includes heating the feed using heat from the spill. [Section 32] The method according to paragraph 29, wherein the step of recovering heat from the effluent in order to process the feed comprises heating the feed in a heat exchanger using the effluent as a heating medium. [Section 33] The method according to claim 29, wherein the step of recovering water from the effluent comprises condensing water and acetic acid in the effluent to obtain condensed water and condensed acetic acid, and separating raw acetic acid containing the condensed water and condensed acetic acid from the effluent to obtain a gas containing ethylene, carbon dioxide, carbon monoxide and unreacted ethane from the effluent. [Section 34] The method according to item 33, wherein the step of recovering water from the spill is to process raw acetic acid to obtain an acetic acid product and scrubbing water, the scrubbing water being for use in an acetic acid scrubber to remove acetic acid from the gas, and the recycled water comprising the bottom flow discharged from the acetic acid scrubber. [Section 35] The method according to paragraph 29, wherein the addition of recycled water to a feed containing ethane includes adding recycled water to ethane before adding oxygen to the feed, or the addition of recycled water to a feed containing ethane includes adding recycled water to oxygen before adding oxygen to the feed, or a combination thereof. [Section 36] The method of paragraph 29, wherein the addition of recycled water to a feed containing ethane includes adding recycled water to ethane in an upstream ethane saturation tower where oxygen is added to the feed, or the addition of recycled water to a feed containing ethane includes adding recycled water to oxygen in an oxygen saturation tower before oxygen is added to the feed, or a combination thereof. [Section 37] The method according to paragraph 29, wherein the addition of recycled water to a feed containing ethane includes adding recycled water to ethane as diluent steam upstream of the addition of oxygen to the feed, or the addition of recycled water to a feed containing ethane includes adding recycled water to oxygen as diluent steam upstream of the addition of oxygen to the feed, or a combination thereof. [Section 38] The method according to claim 29, wherein adding recycled water to a feed containing ethane comprises evaporating the recycled water in a steam dilution drum to obtain dilution steam for addition to the feed. [Section 39] The method according to paragraph 29, wherein processing the feed includes diluting the feed with water. [Section 40] The method according to paragraph 39, wherein the recovery of heat from the effluent for water dilution includes heating the recycled water with heat from the effluent. [Section 41] The method according to claim 39, comprising adding recycled water to a feed containing ethane to obtain a mixture, and recovering heat from the effluent to perform water dilution, comprising heating the mixture with heat from the effluent. [Section 42] The method according to paragraph 39, wherein adding recycled water to a feed containing ethane includes adding recycled water to oxygen added to the feed, and recovering heat from the effluent to perform water dilution includes heating a mixture of recycled water and oxygen added to the feed with heat from the effluent. [Section 43] A method for producing ethylene, A step of discharging effluent from an oxidative dehydrogenation (ODH) reactor that dehydrogenates ethane to ethylene, wherein the effluent contains ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and unreacted ethane. A step of diluting a feed containing ethane for an ODH reactor, wherein the dilution includes adding recycled water to the ethane. The process involves recovering water from the spilled material and obtaining recovered water as recycled water for water dilution, The process involves passing the feed material downstream of the water dilution through a feed material heat exchanger and heating the feed material with the effluent, A step of adding oxygen to the feed to obtain the feed as a mixed feed for the ODH reactor, Methods that include... [Section 44] The method according to item 43, wherein the step of diluting with water further includes adding recycled water to the oxygen. [Section 45] The method according to item 43, comprising recovering heat from the effluent in order to perform water dilution. [Section 46] The method according to paragraph 45, wherein the recovery of heat from the effluent for water dilution includes heating recycled water in a heat exchanger using the effluent as a heating medium. [Section 47] The method according to paragraph 45, wherein the recovery of heat from the effluent for water dilution includes heating a mixture of ethane and recycled water in a heat exchanger using the effluent as a heating medium, or heating a mixture of oxygen and recycled water in a heat exchanger using the effluent as a heating medium, or both.

Claims

1. A method for producing ethylene, The process involves adding water to ethane in an ethane saturated tower to obtain a mixture, The process involves passing the mixture through a feed heat exchanger and heating the mixture using the effluent from an oxidative dehydrogenation (ODH) reactor, A step of adding oxygen to the mixture to obtain a mixed feed for the ODH reactor, The process of introducing the mixed feed into the ODH reactor, A process of dehydrogenating ethane to ethylene via an ODH catalyst in the presence of oxygen in an ODH reactor, A process of discharging effluent containing ethylene, water, acetic acid, carbon dioxide, carbon monoxide, and unreacted ethane from the ODH reactor, Includes, The water added to the ethane includes recycled water from the treatment of effluent. The feed mixture upstream of the heat exchanger contains ethane saturated with water. method.

2. The method according to claim 1, comprising heating the water to be added to the ethane in a cross exchange using the effluent before adding water to the ethane in an ethane saturated tower.

3. The method according to claim 1, wherein the step of adding water to ethane further includes adding water to ethane in a conduit upstream of a heat exchanger upstream of an ethane saturated tower, and the heat exchanger comprises a cross exchanger that utilizes the effluent as a heating medium.

4. The method according to claim 1, wherein the step of adding water to ethane includes adding water to ethane in a conduit upstream of another heat exchanger, and the other heat exchanger comprises a cross exchanger that utilizes the effluent as a heating medium.

5. The method according to claim 4, comprising heating the water in a second cross-exchange using the effluent before adding water to the ethane in the conduit.

6. The method according to claim 1, wherein the step of adding water to ethane includes adding dilution steam to a conduit that transports ethane from a dilution steam drum.

7. The method according to claim 6, comprising heating the water in a cross exchanger using the effluent before introducing the water into a dilution steam drum.

8. The method according to claim 6, wherein the step of adding water to ethane further includes adding water to a conduit that transports ethane upstream of a heat exchanger upstream of the ethane that receives dilution vapor, and the heat exchanger comprises a cross exchanger that utilizes the effluent as a heating medium.

9. The method according to claim 1, comprising adding water to oxygen before adding oxygen to the mixture, wherein adding oxygen to the mixture comprises adding oxygen to a conduit for transporting the mixture.

10. The method according to claim 9, wherein adding water to oxygen includes adding water to a conduit that transports oxygen upstream of the heat exchanger, or adding water to oxygen in an oxygen saturation tower, or a combination thereof, and the heat exchanger comprises a cross exchanger that utilizes effluent as a heating medium.

11. The method according to claim 9, wherein adding water to oxygen includes adding dilution steam to a conduit that transports oxygen from a dilution steam drum.

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