Vacuum generation using low pressure steam generated by oxidative dehydrogenation

Abstract

A method and reactor system for producing acetic acid in a selective oxidation (SO) reactor are provided. An exemplary method includes providing a fresh feed stream to the SO reactor, wherein the fresh feed stream comprises a light hydrocarbon feed stream, a carbon dioxide feed stream, and a steam feed stream. Acetic acid is formed in the SO reactor. An acetic acid product stream is separated from the reactor effluent stream in a scrubber. A recirculated gas stream is obtained from the scrubber. At least a portion of the recirculated gas stream is combined with the fresh feed stream entering the SO reactor.

Description

Technical Field

[0001] The present invention generally relates to oxidative dehydrogenation, and more specifically, to vacuum generation using low-pressure steam from oxidative dehydrogenation. Background Technology

[0002] Olefins, such as ethylene, propylene, and butene, are the basic building blocks of many commercially viable polymers. Since there are no commercially available sources of naturally occurring olefins, polymer producers rely on methods that convert the more abundant lower alkanes into olefins. The preferred method for commercial-scale producers today is steam cracking, a highly endothermic process in which alkanes diluted with steam are subjected to temperatures of at least 800°C for a very short time. The fuel required to generate the desired temperatures, and the equipment required to withstand them, significantly increase the overall cost. Furthermore, the high temperatures promote the formation of coke that accumulates within the system, necessitating periodic and costly reactor shutdowns for maintenance and decoking.

[0003] Selective oxidation processes, such as oxidative dehydrogenation (ODH), are an alternative to steam cracking. This process is exothermic and produces little to no coke. In ODH, lower alkanes (e.g., ethane) are mixed with oxygen in the presence of a catalyst and optionally an inert diluent (e.g., carbon dioxide (CO2), nitrogen (N2), or steam). This process can be carried out at temperatures as low as 300°C to produce the corresponding olefins. Invention Overview One embodiment described herein provides a processing method comprising: separating oxygen (O2) from air in a pressure swing adsorption (PSA) process; feeding the O2 and ethane into an oxidative dehydrogenation (ODH) reactor containing an ODH catalyst; dehydrogenating ethane to ethylene using the O2 in the ODH reactor, generating heat; recovering the heat generated in the ODH reactor using a heat transfer fluid to generate a hot heat transfer fluid; generating high-pressure (HP) steam from the hot heat transfer fluid to generate a cooled heat transfer fluid; operating a steam turbine using the HP steam to generate low-pressure (LP) steam; and generating a vacuum using the LP steam.

[0005] Details of one or more embodiments are set forth in the accompanying drawings and the following description. Other features and advantages will become apparent from the description, the drawings, and the claims. Brief description of the attached diagram Figure 1 It is a simplified block diagram of oxidative dehydrogenation (ODH) coupled with air separation and vacuum.

[0007] Figure 2 This is a block diagram of the ODH reactor system.

[0008] Figure 3 This is a simplified process flow diagram of a method for generating vacuum using low-pressure steam from the ODH process.

[0009] Figure 4 This is a simplified process flow diagram for vacuum generation used in ASPEN Plus® simulations.

[0010] Implementation Plan Description Catalytic oxidative dehydrogenation (ODH) of alkanes to the corresponding olefins is an alternative to steam cracking. Compared to steam cracking, ODH can operate at lower temperatures (e.g., below 450°C) and typically does not produce coke. For ethylene production, ODH offers selectivity exceeding 85% and higher ethylene yields than steam cracking. ODH can be carried out in reactor vessels equipped with catalysts for converting alkanes to the corresponding olefins. Acetic acid may be produced during the conversion of lower alkanes (e.g., ethane) to the corresponding olefins (e.g., ethylene).

[0011] For low-temperature ODH reactions, the oxidant can be provided as air or oxygen. To utilize oxygen (O2), an air separation unit may be required at the front end of the ODH process. Pressure swing adsorption (PSA) is a method of separating gases based on the varying degrees of adsorption of gases on adsorbent materials such as zeolites and activated carbon. In a PSA process, pressure conditions are varied between adsorption and desorption conditions for the target gas. Various PSA techniques can be used to purify O2 from air, including pressure swing adsorption (VSA) using zeolite molecular sieves as adsorbents and vacuum pressure swing adsorption (VPSA). Using vacuum or reduced pressure conditions in air separation for ODH process purposes may require a dedicated vacuum pump and could increase process costs.

[0012] The embodiments described herein provide an integrated method and system for vacuum generation using low-pressure (LT) steam (e.g., 450 kPa or lower) from an ODH process. The exothermic nature of ODH allows for the recovery of heat generated by the ODH process. The recovered heat can be used to generate steam. The steam is introduced into a vacuum vessel, and as the steam cools, it condenses into water, thereby creating a vacuum within the vacuum vessel.

[0013] In various embodiments, air separation to provide O2 for the ODH process utilizes a vacuum generated by the method. Furthermore, in some embodiments, the method uses LT steam. While high-pressure (HT) steam can be used to operate steam turbines, the resulting LT steam is considered low-grade and has little value other than heating the feed stream in the process. The vacuum generation described herein can provide an alternative or additional use for LT steam from the ODH process, thereby contributing to improved process efficiency and reduced costs.

[0014] In the following text, see references Figure 1 and Figure 2 Describe a vacuum generation method and system coupled with ODH. Figure 3 This is an exemplary process flow diagram of a vacuum generation method. Then refer to... Figure 4 Table 1 describes an exemplary heat and material balance simulated using ASPEN Plus®.

[0015] Figure 1 This is a simplified block diagram of oxidative dehydrogenation (ODH) coupled with air separation and vacuum generation. In various embodiments, the ODH process 100 integrates three process stages: air separation 102, ODH reaction 104, and vacuum generation 106. In this example, air 108 is supplied to air separation 102 (e.g., a VPSA process) to separate O2 gas 110. The O2 gas can then be used for ODH reaction 104. In this disclosure, the O2 gas is a gaseous composition containing 95% or more O2. Therefore, the O2 may contain some other gaseous components.

[0016] ODH reaction 104 is a catalytic process that can be used to convert one or more alkanes into corresponding olefins using O2 gas 110. A feed gas 112 containing alkane is provided to ODH reaction 104. In various embodiments, feed gas 112 contains alkanes with 2 to 6 carbon atoms, such as ethane. Since the reaction is exothermic, heat can be recovered to generate steam from water. In some embodiments, the steam is low-pressure (LT) steam 114, for example, about 450 kPa or lower, which can then be fed to vacuum generator 106. In other embodiments, ODH reaction 104 can produce first high-pressure (HT) steam, for example, about 4 MPa (about 580 psi) or higher, and this HT steam is used by a process (e.g., operating a steam turbine) to produce LT steam.

[0017] Vacuum 116, generated using steam 114, can be used to assist the entire ODH process. Specifically, in various embodiments, vacuum 116 can be used for air separation 102. Further details of each stage—air separation 102, ODH reaction 104, and vacuum generation 106—will be provided in [reference needed]. Figure 2 As described below.

[0018] Air separation Figure 2 This is a block diagram of the ODH reactor system 200. It should be understood that each shown unit and component may include one or more containers and auxiliary equipment, such as valves, pumps, sensors, and related control equipment, such as distributed control systems.

[0019] As mentioned above, the first stage of the ODH process can be air separation to generate O2 that can be used for the ODH reaction. Figure 2 As shown, air 108 may first be fed to filter 202 to prevent any liquid or solid particles from entering the next unit. Air 108 is then compressed using air compressor 204. In some embodiments, air 108 is atmospheric air and contains approximately 78.1% nitrogen (N2), approximately 21.0% O2, and other components such as argon and CO2.

[0020] Air 108 can be fed to air separation unit 206 to generate O2 gas 110. Air separation can be performed using a pressure swing adsorption (PSA) process. In various embodiments, air 108 is introduced into a bed of solid adsorbent that selectively adsorbs N2 relative to O2. As N2 is captured by the solid adsorbent, O2 can pass through the bed as O2 gas 110. Figure 2 In one embodiment, air separation unit 206 is illustrated as a two-tower PSA system having a first tower 208 and a second tower 210. Typically, more than one adsorbent tower can be used in a PSA process to achieve a continuous process with minimal downtime, where one tower is used for adsorption and the other tower is regenerated by desorption.

[0021] exist Figure 2 In this configuration, the first tower 208 is used for adsorption, while the second tower 210 is regenerated. When the first tower 208 becomes saturated with adsorbed N2 and requires regeneration, the flow of air 108 can be switched from the first tower 208 to the second tower 210, allowing adsorption to continue using the second tower 210 while the first tower 208 can be regenerated. Regeneration can be achieved by flowing purge gas, reducing tower pressure, or both. The dashed lines indicating entry into the second tower 210 and exit from the first tower 208 represent temporary separation of these airflow patterns from those shown by solid lines. In some embodiments, although... Figure 2 As not specifically shown, the air separation unit 206 may have only one tower or more than two towers.

[0022] For typical PSA systems requiring a vacuum, a vacuum blower can be used to reduce the desorption pressure in the column. It also reduces the required inlet pressure of the column. In various embodiments, the vacuum 116 required for air separation is generated using low-pressure (LT) steam 114 from the ODH process. In various embodiments, any PSA process for separating O2 from air can be used, including pressure swing adsorption (VSA) and vacuum pressure swing adsorption (VPSA). In various embodiments, the PSA process is carried out at near-ambient temperatures, for example, between about 10°C and about 40°C. In another embodiment, the PSA process can be carried out at cryogenic conditions.

[0023] In various embodiments, the towers (e.g., first tower 208 and second tower 210) are filled with adsorbents for adsorbing N2 from air 108. A variety of molecular sieve materials can be used as adsorbents. Examples of N2 adsorbents include low silica X (LSX), zeolite 5A, ion-exchange LSX (Li-LSX, AgLi-LSX, Ca-LSX), Ingelhardt titanium silicates (Na-ETS-10, Ag-ETS-10), and SSZ-13.

[0024] In some embodiments, the O2 gas 110 generated by air separation has an O2 purity of at least 95% and N2 content of less than 0.15%, with the balance being argon. The O2 gas 110 can be sent to an oxygen reservoir 212 for storage.

[0025] Oxidative dehydrogenation (ODH) In various implementation schemes, such as Figure 2 As shown, O2 gas 110 stored in oxygen reservoir 212 can be sent to oxygen compressor 214 and then to mixer 216, where it is mixed with feed gas 112 (e.g., ethane) and optional dilution gas 218 to form mixed feed gas 220. Dilution gas 218 can include, for example, CO2, N2, or vapor. Dilution gas 218 can be added to reduce the flammability of the gas mixture during the ODH reaction. Furthermore, dilution gas 218 can also provide a quenching effect to absorb the heat generated by the exothermic ODH reaction. In some embodiments, mixing in mixer 216 can be carried out using a non-flammable liquid (e.g., water), with each gas component bubbled into the liquid.

[0026] The mixed feed gas 220 can be sent to the ODH reactor 222. In the illustrated embodiment, the ODH reactor 222 is a tubular reactor with an additional cooling jacket 224. The ODH reactor 222 can be a fixed-bed reactor or a fluidized-bed reactor. The ODH reaction takes place in the presence of oxygen supplied by O2 gas 110. Although Figure 2 A single feed line is shown for supplying mixed feed gas 220 to ODH reactor 222, but combinations of feed lines are possible.

[0027] ODH reactor 222 contains a catalyst (e.g., a fixed bed of catalyst) for converting alkanes (e.g., ethane) into the corresponding olefins (ethylene). The ODH catalyst may be a metal oxide catalyst. In some embodiments, the ODH catalyst comprises oxides containing molybdenum (Mo), vanadium (V), tellurium (Te), niobium (Nb), or mixtures thereof. In some embodiments, the catalyst contains Mo, V, Te, and Nb, wherein the Mo:V molar ratio is from 1:0.12 to 1:0.49, the Mo:Te molar ratio is from 1:0.01 to 1:0.30, the Mo:Nb molar ratio is from 1:0.01 to 1:0.30, and oxygen is present at least in an amount sufficient to satisfy the valence of any present metal oxide. The molar ratios of Mo, V, Te, and Nb can be determined by inductively coupled plasma mass spectrometry (ICP-MS).

[0028] This catalyst allows the ODH reaction to proceed at temperatures below 400°C. An exemplary catalyst is one having the formula Mo. a V b Te c Nb d Pd e O f The mixture of metal oxides, where subscripts a, b, c, d, e, and f are the relative atomic weights of elements Mo, V, Te, Nb, Pd, and O, respectively. When a = 1, then b = 0.01 to 1.0, c = 0.01 to 1.0, d = 0.01 to 1.0, 0.00 ≤ e ≤ 0.10, and f is the number of catalyst valence states. Various embodiments of the method described herein are not necessarily dependent on the type of ODH catalyst, as well as various catalyst formulations and process temperatures, such as moderate temperatures of 400°C to 500°C or high temperatures above 500°C.

[0029] The ODH reaction produces a product stream 226 containing an olefin (e.g., ethylene). In embodiments where ethane is converted to ethylene, acetic acid is also produced and present in product stream 226. Other components of product stream 226 may include CO2, carbon monoxide (CO), oxygen-containing compounds, and water.

[0030] Product stream 226 can then be sent to quench tower QT 228, where water stream 232 is used to quench product stream 226 and remove acetic acid and other oxygen-containing compounds as effluent 230. First purified product stream 234 can exit quench tower 228 as a gaseous stream. First purified product stream 234 may contain the target olefin product, unconverted alkanes, unreacted oxygen, CO2, CO, and a diluent.

[0031] The first purified product stream 234 can be further processed by absorber AR 236 to remove CO2, forming a second purified product stream 240. In various embodiments, absorber AR 236 is an amine washing system in which the first purified product stream 234 is contacted with a lean amine stream (e.g., diethanolamine, monoethanolamine, or methyldiethanolamine). Most of the CO2 present in the first purified product stream 234 can be captured by reacting with the lean amine stream. A caustic tower can be located downstream for further purification and removal of trace amounts of CO2 that may have passed through absorber AR 236. The second purified product stream 240 can be sent for further purification and processing, such as by product compressor 242, followed by cryogenic separation to further purify ethylene.

[0032] Figure 2 The processes and systems shown are merely examples, and other reactor configurations and different process flows are feasible. Depending on the installation environment, not all of the units shown may be present. Furthermore, additional units, such as additional reactors and compressors, may be present. In some embodiments, although not specifically shown, ODH reaction 104 is carried out using two or more ODH reactors, for example, those arranged in series. In such embodiments, subsequent ODH reactors can receive product feed streams from previous reactors to further react unreacted alkanes. Process parameters can also be selected and controlled for each reactor. In one embodiment, for subsequent ODH reactors arranged in series, the reaction temperature can be gradually increased.

[0033] Heat transfer and high-pressure (HP) steam generation The heat generated by the oxidative dehydrogenation (ODH) reaction can be recovered to produce steam, which can be used to power equipment or for other applications. Figure 2 In this process, heat transfer fluid 244 is supplied from fluid reservoir 246 to cooling jacket 224. In various embodiments, heat transfer fluid 244 may be treated water (e.g., softened water, boiler feedwater, etc.), glycol (e.g., ethylene glycol, propylene glycol, etc.), molten salt, or other types of heat transfer fluid.

[0034] In various implementations, molten salt is used as the heat transfer fluid 244. For example, nitrates such as potassium nitrate, sodium nitrate, and calcium nitrate, as well as chloride salts such as lithium chloride-potassium chloride mixtures and sodium chloride-potassium chloride mixtures, can be used. Due to their excellent heat capacity, molten salt can effectively remove heat from the exothermic ODH reaction and help manage reaction runaway.

[0035] Examples of non-molten salt heat transfer fluids 244 include DOWTHERM® heat transfer fluids (Dow Chemical Company, Midland, Michigan, USA), which may typically contain glycols or synthetic organic compounds. Other examples include DW-Therm HT products (Huber USA, Gary, North Carolina, USA), SYLTHERM® silicone fluids (e.g., SYLTHERM 800) (Dow Chemical Company, Midland, Michigan, USA), and SantoLubes® products (e.g., OS-750 or OS-124) (SantoLubes LLC, Spartanburg, South Carolina, USA).

[0036] Heat transfer fluid 244 absorbs the heat generated by the ODH reaction and cools the ODH reactor 222, producing heated heat transfer fluid 248. Heated heat transfer fluid 248 may first be sent to a flow bypass conduit 250 to divide it into several portions. In some embodiments, a first fluid portion 252 may be sent to a first heat exchanger 254, and a second fluid portion 256 may be sent to a second heat exchanger 258. For example, the second fluid portion 256 may account for approximately 20-80% by weight of the total flow rate of heated heat transfer fluid 248.

[0037] For steam generation, water 260 is supplied to the first heat exchanger 254 and heated by the first fluid section 252. The heated water 262 is then sent to a flash container 264, where it flashes into steam 266. The cooled first fluid section 268 can then be returned to the fluid reservoir 246.

[0038] In various embodiments, steam 266 is saturated steam. Steam 266 can be further heated by using a second fluid portion 256 through a second heat exchanger 258, and can form high-pressure (HP) steam 270. The cooled second fluid portion 272 can be returned to the fluid reservoir 246 for reuse. Therefore, the ODH reactor system 200 may include a circulation system to circulate the heat transfer fluid 244 between the fluid reservoir 246, the cooling jacket 224, and the heat exchangers (e.g., the first heat exchanger 254 and the second heat exchanger 258). In some embodiments, a T-joint 274 may be used to combine the cooled first fluid portion 268 and the cooled second fluid portion 272, and then the combined fluid is returned to the fluid reservoir 246.

[0039] HP Steam 270 may have a pressure of about 4 MPa (about 580.2 psi) or higher. In some embodiments, HP Steam 270 is very high pressure (VHP) steam with a pressure of about 9 MPa (about 1305.3 psi) or higher. HP Steam 270 may have a temperature between 300°C and 450°C.

[0040] The temperature and pressure of steam 266 and HP steam 270 depend on the configuration of the ODH reactor system 200, such as the number of reactors and the process temperature. Furthermore, the heat recovery process used to generate steam can be varied, for example, by changing the split ratio of the first fluid section 252 and the second fluid section 256, as well as the design and operation of the flash vessel 264.

[0041] The HP steam 270 generated at this stage can be used as part of the ODH process or for other applications in the plant. For example, it can be used to drive a compressor (e.g., Figure 2 The turbine of the product compressor 242).

[0042] Low-pressure (LP) steam generation In various implementations, HP Steam 270 was initially used for applications other than vacuum generation. For example, in Figure 2 In this process, HP steam 270 can be used to operate a steam turbine 276 connected to a product compressor 242. After operating the steam turbine 276, HP steam 270 can be converted into low-pressure (LP) steam 114. In various embodiments, the pressure of LP steam 114 is about 450 kPa (about 65.3 psi) or lower. In some embodiments, the pressure can be between about 100 kPa (about 14.5 psi) and 300 kPa (about 43.5 psi). In one embodiment, the pressure is about 344.7 kPa (about 50 psi). LP steam 114 can have a temperature between 100°C and 150°C. In some embodiments, LP steam 114 is saturated steam. Typically, this steam has a low grade, limiting its applications (e.g., heating purposes). In various embodiments, on the other hand, LP steam 114 can be used for vacuum generation as part of an ODH process, as described below.

[0043] Vacuum generation and applications exist Figure 2 In this process, LP vapor 114 is introduced into vacuum container 278. In various embodiments, the temperature of vacuum container 278 is maintained at approximately 25°C or lower. LP vapor 114 condenses in vacuum container 278, creating a vacuum 116 and condensate 280. Condensate 280 can be discharged from vacuum container 278 through a discharge port. In some embodiments, the pressure of LP vapor 114 can be reduced before entering vacuum container 278, for example, using regulator 282. In one embodiment, the pressure of LP vapor 114 can be reduced from approximately 344.7 kPa (approximately 50 psi) to approximately 100 kPa (approximately 14.5 psi).

[0044] In various implementations, the generated vacuum 116 is used as part of the ODH process. Figure 2 In the illustrated embodiment, it is used for the desorption step of air separation. Therefore, vacuum container 278 can be connected to the outlets of the first column 208 and the second column 210 via appropriate valves and gas regulators. As previously described, the two-column PSA system can achieve continuous air separation by allowing adsorption in one column while regenerating the other. Vacuum 116 can be used to reduce the pressure on the column to be regenerated (e.g., by operating valves) Figure 2 The pressure in the second tower (210) of the tower. Figure 2 In this configuration, the first tower 208 is used for adsorption, therefore the valve between the first tower 208 and the vacuum container 278 is closed. Due to the pressure reduction, the adsorbed material (e.g., N2) in the second tower 210 desorbs and is removed from the second tower 210 along with the residual gas. These gases (e.g., N2, CO2, and moisture) flow into the vacuum container 278 and can then be released into the atmosphere. In some embodiments, the gas flow can be released directly into the atmosphere without entering the vacuum container 278. Although Figure 2 Only one container for vacuum generation is shown in the figure, but in some implementations, more than one vacuum container may exist, depending on the size of the tower in the PSA system.

[0045] In some embodiments, the ODH reactor system 200 also includes an alternative vacuum pump 284, which is connected to the outlets of the first column 208 and the second column 210 via appropriate valves and gas regulators. The alternative vacuum pump 284 can serve as a backup and allows the desorption step to be performed even if the vacuum vessel 278 is unable to generate a vacuum due to, for example, a lack of LP vapor 114.

[0046] Figure 3 This is a simplified process flow diagram of a method for generating vacuum using low-pressure steam from the ODH process. Figure 3 In this process, method 300 begins by separating oxygen (O2) from air 302 in a pressure swing adsorption (PSA) process, then feeding the O2 and ethane 304 into an oxidative dehydrogenation (ODH) reactor containing an ODH catalyst. Method 300 then proceeds to dehydrogenate ethane 306 to ethylene using O2 in the ODH reactor, generating heat. The heat generated in the ODH reactor is recovered using a heat transfer fluid 308, producing a hot heat transfer fluid. Next, high-pressure (HP) steam 310 is generated from the hot heat transfer fluid, producing a cooled heat transfer fluid. The HP steam is then used to run a steam turbine 312, producing low-pressure (LP) steam. The LP steam is used to generate a vacuum 314.

[0047] Except as provided in the operational examples or otherwise, all figures or expressions indicating quantities of ingredients, reaction conditions, etc., used in the specification and claims should in all cases be understood to be modified by the term “about.” Therefore, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximate values ​​that may vary depending on the desired characteristics expected to be obtained in this disclosure. At least, and without attempting to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be interpreted based on at least the number of significant figures reported and by applying conventional rounding techniques.

[0048] Although the numerical ranges and parameters described in this disclosure are approximate, the numerical values ​​illustrated in specific examples are reported as precisely as possible. However, any numerical value inherently contains some error that must be caused by the standard deviation present in its respective test measurement.

[0049] Furthermore, it should be understood that any numerical range referenced herein is intended to include all subranges contained therein. For example, the range "1 to 10" is intended to include all subranges between the referenced minimum value of 1 and the referenced maximum value of 10, inclusive; that is, a minimum value equal to or greater than 1 and a maximum value equal to or less than 10. Because the disclosed numerical ranges are continuous, they include every value between the minimum and maximum values. Unless otherwise expressly stated, the various numerical ranges specified in this application are approximate values.

[0050] As used herein, the term "alkane" refers to a saturated hydrocarbon. In many cases, alkanes consist of hydrogen and carbon atoms arranged in a straight-chain structure, where all carbon-carbon bonds are single bonds. Alkanes have the general chemical formula C1. n H 2n+2 In many embodiments of this disclosure, the alkane is one or more of methyl methethane, ethane, propane, butane, pentane, hexane, octane, decane, and dodecane. In certain embodiments, the alkane refers to ethane and propane.

[0051] As used herein, the term "olefin" refers to an unsaturated hydrocarbon containing at least one carbon-carbon double bond. In many embodiments, olefin refers to α-olefin. In many embodiments of this disclosure, olefin refers to one or more of ethylene, propylene, 1-butene, pentene, pentadiene, hexene, octene, decene, and dodecene. Furthermore, as used herein, the term includes other compounds having carbon-carbon double bonds, such as butadiene, etc. In certain embodiments, olefin refers to ethylene and propylene, and in some embodiments, it refers to ethylene.

[0052] As used herein, the term "fixed-bed reactor" refers to one or more reactors connected in series or parallel, typically comprising cylindrical tubes packed with catalyst particles, through which reactants flow through the bed and are converted into products. The catalyst in the reactor can have various configurations, including but not limited to a large bed, several horizontal beds, several parallel packed tubes, and multiple beds within its own shell.

[0053] As used herein, the term “fluidized bed reactor” refers to one or more reactors connected in series or in parallel, typically comprising a fluid (gas or liquid) passing at sufficiently high speeds through a solid particulate catalyst (which may be shaped into tiny spheres) to suspend the solid and make it move like a fluid.

[0054] Example ASPEN Plus® simulations were performed to evaluate the vacuum generation method. The heat and material balance of the method were simulated based on ideal equations of state, and the properties of the vapor were obtained using STEAMNBS. Figure 4 This is a simplified vacuum generation process flow diagram 400 for ASPEN Plus® simulations. Figure 4 In this simulation, cooling inflow 402 enters heat exchanger 404 and discharges effluent 406. Heat exchanger 404 is used to maintain the temperature of vacuum vessel 408. First low-pressure (LP) vapor 410 (at 584.0 kPa) is processed to reduce its pressure, and second LP vapor 412 (at 100 kPa) is fed into vacuum vessel 408. In this simulation, residual gas inflow 414 is assumed to be negligible. Condensation in vacuum vessel 408 produces condensate 416 and resulting vapor 420. The parameters and simulated heat and material balance are summarized in Table 1 below.

[0055] Table 1: Heat and Material Balance Based on Aspen Plus® Simulation Cooling inflow 402 Effluent 406 First LP Steam 410 Second LP Steam 412 Condensate 416 temperature ℃ 30 40 158 158 45 pressure kPa 200.0 185.0 584.0 100.0 9.6 mole fraction - 0 0 1 1 0 mass density <![CDATA[kg / m 3 ]]> 989.1 978.9 2.9 0.5 974.5 enthalpy flow MW -264.1 -263.3 -3.7 -3.7 -4.4 Average molecular weight - 18.0 18.0 18.0 18.0 18.0 Molar flow kmol / h 3330.5 3330.5 55.5 55.5 55.5 <![CDATA[H2O]]> kmol / h 3330.5 3330.5 55.5 55.5 55.5 <![CDATA[O2]]> kmol / h 0 0 0 0 0 <![CDATA[N2]]> kmol / h 0 0 0 0 0 mass flow kg / h 60000 60000 1000 1000 1000 <![CDATA[H2O]]> kg / h 60000 60000 1000 1000 1000 <![CDATA[O2]]> kg / h 0 0 0 0 0 <![CDATA[N2]]> kg / h 0 0 0 0 0 Volumetric flow rate <![CDATA[m 3 / h]]> 60.7 61.3 340.6 1989.2 1.0 .

[0056] As a result of condensation, the volume of the second LP vapor 412 is reduced to approximately 1 / 1938, generating a vacuum pressure of 9.6 kPa (approximately 1.4 psi or 0.09 atm) (the pressure of the resulting vapor 420). This demonstrates the ability of LT vapor to generate a vacuum through condensation, with a relatively small energy input required for cooling.

[0057] Implementation One embodiment described herein provides an oxidative dehydrogenation method comprising: separating oxygen (O2) from air in a pressure swing adsorption (PSA) process; feeding the O2 and ethane into an oxidative dehydrogenation (ODH) reactor containing an ODH catalyst; dehydrogenating ethane to ethylene using the O2 in the ODH reactor, generating heat; recovering the heat generated in the ODH reactor using a heat transfer fluid to generate a hot heat transfer fluid; generating high-pressure (HP) steam from the hot heat transfer fluid to generate a cooled heat transfer fluid; operating a steam turbine using the HP steam to generate low-pressure (LP) steam; and generating a vacuum using the LP steam.

[0058] In one aspect, and in combination with any other aspect, the PSA process includes: compressed air; delivering the compressed air to a PSA tower containing a molecular sieve; selectively adsorbing nitrogen (N2) from the air onto the molecular sieve to generate O2; and desorbing N2 from the molecular sieve using a vacuum generated by LP vapor.

[0059] In one aspect, and in combination with any other aspect, generating a vacuum includes: introducing LP vapor into a container; and condensing the LP vapor in the container to produce liquid water.

[0060] In one aspect, creating a vacuum also includes discharging liquid water from the container through an outlet.

[0061] In one aspect, creating a vacuum also includes maintaining the temperature of the container at 25°C or lower during condensation.

[0062] In one aspect, and in combination with any other aspect, the method also includes reducing the pressure of the LP vapor before creating a vacuum.

[0063] In one aspect, and in combination with any other aspect, the heat transfer fluid includes molten salt.

[0064] In one aspect, and in combination with any other aspect, heat recovery includes feeding heat transfer fluid into a heat transfer jacket connected to the ODH reactor.

[0065] In one aspect, and in combination with any other aspect, the method also includes feeding a cooled heat transfer fluid into a heat transfer jacket connected to the ODH reactor while recovering heat.

[0066] In one aspect, and in combination with any other aspect, the method also includes using a steam turbine to power the compressor.

[0067] In one aspect, and in combination with any other aspect, the pressure of HP steam is 4 MPa or higher.

[0068] In one aspect, and in combination with any other aspect, the pressure of HP steam is between 4 MPa and 9 MPa.

[0069] In one aspect, or in combination with any other aspect, the pressure of LP steam is 450 kPa or lower.

[0070] In one aspect, and in combination with any other aspect, the pressure of LP steam is between 100 kPa (14.5 psi) and 300 kPa (43.5 psi).

[0071] In one aspect, and in combination with any other aspect, the temperature of HP steam is between 300°C and 450°C.

[0072] In one aspect, and in combination with any other aspect, the temperature of LP steam is between 100°C and 150°C.

[0073] In one respect, and in combination with any other respect, LP steam is saturated steam.

[0074] Another embodiment described herein provides an air separation system comprising: a pressure swing adsorption (PSA) tower including a molecular sieve for selectively adsorbing nitrogen (N2) from air and releasing oxygen (O2); an oxidative dehydrogenation (ODH) reactor including an ODH catalyst reactor for dehydrogenating ethane using O2; a heat exchanger coupled to the ODH reactor and configured to recover heat from dehydrogenation by converting a heat transfer fluid into a hot heat transfer fluid; a steam generator coupled to the heat exchanger to generate high-pressure (HP) steam using the hot heat transfer fluid and discharge cooled heat transfer fluid; a steam turbine for receiving HP steam and discharging low-pressure (LP) steam; and a vacuum generator for generating a vacuum using LP steam, the vacuum generator including a port connected to the outlet of the PSA tower.

[0075] In one aspect, and in combination with any other aspect, the vacuum generator includes a vessel for receiving and condensing LP vapor.

[0076] In one aspect, and in combination with any other aspect, the system also includes a gas regulator located between the steam turbine and the vacuum generator, which is configured to reduce the pressure of the LP steam.

[0077] In one aspect, and in combination with any other aspect, the system also includes a steam drum for generating HP steam using a heat transfer fluid with heat.

[0078] In one aspect, and in combination with any other aspect, the heat exchanger includes a circulation system for receiving and circulating a cooled heat transfer fluid from a steam generator.

[0079] In one aspect, and in combination with any other aspect, the reactor includes a fixed-bed reactor.

[0080] Another embodiment described herein provides an ethylene production system comprising: an air separator for separating oxygen (O2) from air; an oxidative dehydrogenation (ODH) reactor containing an ODH catalyst to dehydrogenate ethane to ethylene using O2 from the air separator and discharge a product stream containing ethylene; a heat exchanger for recovering heat from the ODH; a steam generator for generating HP steam using the recovered heat; a heat engine for receiving the HP steam and generating LP steam at a pressure lower than the HP steam; and a vacuum vessel for receiving the LP steam and generating a vacuum by condensing the LP steam, the vacuum vessel including a vacuum port for applying a vacuum to the air separator.

[0081] In one aspect, and in combination with any other aspect, the air separator includes first and second pressure swing adsorption (PSA) towers, wherein the gas outlet of each PSA tower is connected to a vacuum port.

[0082] In one aspect, and in combination with any other aspect, the first and second PSA towers are filled with molecular sieves to selectively adsorb nitrogen (N2) from the air.

[0083] In one aspect, and in combination with any other aspect, the vacuum container includes a discharge port for venting condensate generated by LP vapor.

Claims

1. An oxidative dehydrogenation method, the method comprising: Oxygen (O2) is separated from the air in the pressure swing adsorption (PSA) process. The O2 and ethane are fed into an oxidative dehydrogenation (ODH) reactor containing an ODH catalyst; In the ODH reactor, the O2 is used to dehydrogenate ethane to ethylene, generating heat. The heat generated in the ODH reactor is recovered using a heat transfer fluid, which generates the heat; High-pressure (HP) steam is generated from the hot heat transfer fluid, resulting in a cooled heat transfer fluid; The HP steam is used to operate a steam turbine, producing low-pressure (LP) steam; and The LP vapor is used to generate a vacuum.

2. The method according to claim 1, wherein the PSA process comprises: Compress air; Compressed air is delivered to a PSA tower containing molecular sieves; Nitrogen (N2) in the air is selectively adsorbed onto the molecular sieve to generate O2; as well as The N2 is desorbed from the molecular sieve using the vacuum generated by the LP vapor.

3. The method of claim 1, wherein generating the vacuum comprises: The LP vapor is fed into a container; as well as The LP vapor is condensed in the container to produce liquid water.

4. The method of claim 3, wherein generating the vacuum further comprises discharging the liquid water from the container through an outlet.

5. The method of claim 3, wherein generating the vacuum further comprises maintaining the temperature of the container at 25°C or lower during the condensation.

6. The method of claim 1, further comprising reducing the pressure of the LP vapor before generating the vacuum.

7. The method of claim 1, wherein the heat transfer fluid comprises molten salt.

8. The method of claim 1, wherein recovering the heat comprises feeding the heat transfer fluid into a heat transfer jacket connected to the ODH reactor.

9. The method of claim 1, further comprising feeding the cooled heat transfer fluid into a heat transfer jacket connected to the ODH reactor while recovering the heat.

10. The method of claim 1, further comprising using the steam turbine to power the compressor.

11. The method of claim 1, wherein the pressure of the HP steam is 4 MPa or higher.

12. The method of claim 1, wherein the pressure of the HP steam is between 4 MPa and 9 MPa.

13. The method of claim 1, wherein the pressure of the LP steam is 450 kPa or lower.

14. The method of claim 1, wherein the pressure of the LP steam is between 100 kPa (14.5 psi) and 300 kPa (43.5 psi).

15. The method of claim 1, wherein the temperature of the HP steam is between 300°C and 450°C.

16. The method of claim 1, wherein the temperature of the LP steam is between 100°C and 150°C.

17. The method of claim 1, wherein the LP steam is saturated steam.

18. An air separation system, the system comprising: A pressure swing adsorption (PSA) tower containing molecular sieves for selectively adsorbing nitrogen (N2) from the air and releasing oxygen (O2); This includes an oxidative dehydrogenation (ODH) reactor, which utilizes the O2 to dehydrogenate ethane using an ODH catalyst reactor; A heat exchanger coupled to the ODH reactor and configured to recover heat from dehydrogenation by converting the heat transfer fluid into a hot heat transfer fluid. A steam generator coupled to the heat exchanger to generate high-pressure (HP) steam using the heat transfer fluid and discharge cooled heat transfer fluid. A steam turbine for receiving the high-pressure (HP) steam and discharging low-pressure (LP) steam; and A vacuum generator for generating a vacuum using the LP vapor, the vacuum generator including a port connected to the outlet of the PSA tower.

19. The system of claim 18, wherein the vacuum generator includes a container for receiving and condensing the LP vapor.

20. The system of claim 18 further includes a gas regulator located between the steam turbine and the vacuum generator, configured to reduce the pressure of the LP steam.

21. The system of claim 18, further comprising a steam drum for generating the HP steam using the heat transfer fluid of the heat.

22. The system of claim 18, wherein the heat exchanger includes a circulation system for receiving and circulating the cooled heat transfer fluid from the steam generator.

23. The system of claim 18, wherein the reactor comprises a fixed-bed reactor.

24. An ethylene production system, comprising: An air separator used to separate oxygen (O2) from the air; An oxidative dehydrogenation (ODH) reactor containing an ODH catalyst to dehydrogenate ethane to ethylene using the O2 from the air separator and discharge a product stream containing the ethylene. Heat exchangers used to recover heat from the ODH; Steam generator for producing HP steam using recovered heat; A heat engine for receiving the HP steam and generating LP steam at a pressure lower than the HP steam; and A vacuum container for receiving the LP vapor and generating a vacuum by condensing the LP vapor, the vacuum container including a vacuum port for applying the vacuum to the air separator.

25. The ethylene production system of claim 24, wherein the air separator comprises a first pressure swing adsorption (PSA) tower and a second PSA tower, and wherein the gas outlet of each PSA tower is connected to the vacuum port.

26. The ethylene production system of claim 25, wherein the first PSA tower and the second PSA tower are packed with molecular sieves to selectively adsorb nitrogen (N2) from the air.

27. The ethylene production system of claim 24, wherein the vacuum vessel includes a discharge port for discharging condensate generated by the LP vapor.

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