A process for the oxidative dehydrogenation of ethane to ethylene

Abstract

The present invention relates to a process for oxidative dehydrogenation of ethane to ethylene applicable to multiple diluents. In the present invention, a deoxygenation bed layer and a selective hydrogenation tower are added after the drying tower to remove oxygen and unsaturated hydrocarbons such as acetylene in the reaction gas respectively, improving the safety of the process flow while increasing the purity of the product ethylene; a single light component removal tower is used to separate light components such as CO, methane and balance gas nitrogen generated by side reactions in the system from components such as ethylene and ethane, and the separation process is simple; a heavy component removal tower is added after the ethylene tower in the present invention to complete the refining treatment of the excessive ethane in the reaction and at the same time the fresh feed ethane also undergoes heavy component removal pretreatment through this tower, avoiding the accumulation of heavy components in the system, reducing the generation of other by-products and the occurrence of coking problems of the reactor catalyst; when CO2 or water vapor is used as the balance gas in the present invention, the CO2 or water vapor in the system can be separated and recycled before the product gas compression system, greatly reducing the subsequent gas treatment volume and lowering the equipment investment and operating costs.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical production, and specifically refers to a process for oxidative dehydrogenation of ethane to ethylene applicable to multiple diluents. Background Art

[0002] Ethylene is an important organic chemical raw material and is one of the indicators to measure the development level of the chemical industry in a country. The annual demand for ethylene in China is relatively large, and there is a continuous equivalent gap, relying on imports to a certain extent. Currently, common ethylene production technologies mainly include MTO technology using coal / methanol as raw materials, naphtha cracking technology, and ethane steam cracking technology. Considering various issues such as energy consumption, pollution, and investment, light alkanes have become potential low-cost raw materials for producing ethylene. Currently, the mainstream ethane-to-ethylene technology in China is ethane steam cracking technology, but this process also has problems such as complex process, large number of equipment, high reaction temperature (800 - 900 °C), high energy consumption, easy carbon deposition and coking in the cracking furnace, complex product composition, difficult separation, and high equipment investment.

[0003] The technology for oxidative dehydrogenation of ethane to ethylene has a low reaction temperature (about 200 - 500 °C), and has characteristics such as short process flow, small number of equipment, low operating cost, low energy consumption, and good economic benefits, and has good market competitiveness. Some process methods for preparing olefins using this principle have been disclosed in the prior art, for example:

[0004] "A Method and Process for Continuously Producing Ethylene from Ethane" with the publication number CN110511109A discloses a scheme, including the pre-mixing and pre-heating process of ethane, oxygen, and nitrogen raw materials, the reaction process for oxidative dehydrogenation of ethane to ethylene, the separation process of ethylene from other substances, and the recycling process of unreacted ethane; its ethane oxidative dehydrogenation reactor adopts a shell-and-tube fixed-bed reactor. After the reaction, water and the generated acetic acid are removed through a gas-liquid separator, and then the residual water and CO 2 components, and the remaining gas (N 2 , C 2 H 6 , C 2 H 4 , oxygen, and CO) are cooled through a multi-stage compressor and a heat exchanger, and the gaseous N 2 is separated to the atmosphere. The remaining material stream passes through a distillation column, and oxygen, CO, and the remaining nitrogen are separated at the top of the column. A mixture of ethane and ethylene flows out at the top of the column, and then ethylene and ethane are separated through another distillation column. Product ethylene is obtained at the top of the column, and the ethane at the bottom of the column is gasified and heat-exchanged, and then enters the next cycle together with the raw material gas ethane, oxygen, nitrogen, etc. However, the above scheme has the following defects: ① Using nitrogen as the balance gas, nitrogen needs to be multi-stage compressed and condensed and separated along with the product gas, and this compression and separation process has high energy consumption; ② Removing N 2Subsequently, the concentration of oxygen in the mixed gas increases significantly. There is no separate deoxygenation process or method in the process and method. The mixture of CO, ethylene, ethane, oxygen, etc. in the process stream poses an explosion risk, and the safety performance of the process and method is relatively low; ③N 2 The separation effect is not ideal, and another distillation column is required to separate CO, oxygen, and the remaining N 2 , resulting in high energy consumption and large investment in the light component separation process in the system; ④The balance gas N 2 After being separated, it is directly discharged into the atmosphere through a heat exchanger and an expander without recycling the balance gas, resulting in high process operation costs; ⑤There is no hydrogenation tower and heavy component removal tower in the process and method. While affecting the ethylene concentration of the product, since the heavy components enter the reactor with the recycled ethane, it is easy to cause side reactions and catalyst coking.

[0005] The "Method for Oxidative Dehydrogenation of Light Alkanes to Olefins" with the publication number CN110256186A discloses a solution. Light alkanes, an oxidant, and a diluent are introduced into a light alkane oxidative dehydrogenation reactor and undergo an oxidation reaction under the catalysis of a light alkane oxidative dehydrogenation catalyst; the reaction products are then quenched, selectively oxidized for CO, decarbonized, separated by pressure swing adsorption, and separated for olefins to obtain olefin products. However, the above solution has the following defects: ①The PSA separation method is used to separate the balance gas and light component impurities in the product gas from the product ethylene and recycled ethane. This separation method is not as mature as the cryogenic separation technology; ②There is no hydrogenation tower and heavy component removal tower in the process and method. While affecting the ethylene concentration of the product, since the heavy components enter the reactor with the recycled ethane, it is easy to cause side reactions and catalyst coking.

[0006] The "Process for Oxidative Dehydrogenation of Ethane" with the publication number CN111032600A discloses a solution. Using carbon dioxide as the balance gas, ethane, oxygen, and CO 2 The mixed gas reacts in contact with the oxide. The product gas first enters a water washing unit to remove water and acetic acid, obtaining a mixed stream of oxygen, CO, acetylene, ethylene, ethane, and CO 2 (the volume content of CO 2 is 50% - 75%). At 200 - 260 °C under the action of a copper-containing catalyst, acetylene, CO, and oxygen form CO 2 , and oxygen is added when the oxygen is insufficient. The remaining ethylene, ethane, and CO in the mixed gas 2 are separated by complexation to obtain ethylene products. However, the above solution has the following defects: ①Using a copper-based catalyst, catalytically oxidizing acetylene, CO, and oxygen to generate CO 2, there is an explosion risk in the mixture of CO, ethylene, ethane, oxygen, etc. in the process logistics, and the safety performance of the process and method is relatively low; ② The ethylene product is obtained by complex separation, and the separation technology of this process is not yet mature; ③ The de-heavy tower is not set in the process and method, which affects the ethylene concentration of the product. At the same time, due to the heavy components entering the reactor with the recycled ethane, side reactions are likely to occur and the catalyst is prone to coking.

[0007] Therefore, for the current process of preparing ethylene by oxidative dehydrogenation of ethane, further improvement is needed. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a process for oxidative dehydrogenation of ethane to ethylene applicable to various diluents in view of the current situation of the prior art. This process has strong adaptability to the equilibrium gas, simple process flow, low energy consumption, and can be compatible with common equilibrium gases such as air, nitrogen, CO 2 , water vapor, methane, etc., can effectively reduce the generation of by-products, avoid the problem of coking of the reactor catalyst, and improve the product purity.

[0009] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0010] A process for oxidative dehydrogenation of ethane to ethylene, comprising the following steps:

[0011] (1) Fresh feed ethane and equilibrium gas are mixed evenly in a first feed mixer, heated by exchanging heat with the product gas in a raw material gas preheater, reheated by a raw material gas heater, and then mixed evenly with oxygen in a second feed mixer and fed into a reaction system for reaction;

[0012] (2) After the reaction, the resulting reaction gas exchanges heat in the raw material gas preheater and then enters a reaction gas cooling system for energy recovery and cooling, and then is sent to a liquid separation tank. The acetic acid-containing liquid is discharged to a waste liquid treatment system, and the gas enters a CO 2 removal system to remove CO 2 The gas after removal is sent to a compression and caustic scrubbing system to compress the product gas and perform deep CO 2 removal;

[0013] (3) The waste water between the compression sections of the compression and caustic scrubbing system and the waste caustic liquid at the bottom of the caustic scrubbing tower go to a waste water treatment system. The compressed product gas enters a first dryer for drying, then enters an oxygen remover to remove the excessive oxygen in the reaction, and then is sent to a selective hydrogenation tower to hydrogenate and remove acetylene, and then is dehydrated by a second dryer. The dried gas enters a cold box system for cooling the product gas, and the cooled product gas enters a de-light tower;

[0014] (4) The light components such as CO, methane, N 2 separated from the top of the de-light tower are sent out after heat exchange in the cold box system. When the process uses N2 When it is the dilution gas, a light component treatment system can be adopted first. After the treated light components meet the standards, they are discharged. The ethylene, ethane and heavy components obtained at the bottom of the light removal tower enter the ethylene purification tower for the purification and separation of ethylene products;

[0015] (5) The ethylene product separated from the top of the ethylene purification tower is transported out of the battery limit, and the ethane and heavy components discharged from the bottom of the tower are sent to the heavy removal tower together with the supplemented fresh raw material ethane for ethane recovery and purification; the gaseous ethane separated from the top of the heavy removal tower is recycled back to the first feed mixer for the next reaction cycle, and the heavy components are separated from the bottom of the tower.

[0016] Preferably, the reaction system includes an ethane oxidative dehydrogenation reactor, a reactor heat removal system and a steam generation system connected in series, which are used for carrying out oxidative dehydrogenation reaction on the raw material ethane gas to generate ethylene, removing the reaction heat and by-producing steam.

[0017] Preferably, the structural form of the ethane oxidative dehydrogenation reactor is any one of fluidized bed, packed bed, fixed bed and shell-and-tube type. In the reaction section of the shell-and-tube type ethane oxidative dehydrogenation reactor, the tube box is a heat exchange tube filled with catalyst, and ethane undergoes oxidative dehydrogenation reaction under the action of the catalyst to generate ethylene and by-products;

[0018] The operating conditions in the reaction section of the ethane oxidative dehydrogenation reactor are an operating temperature of 200 - 500 °C and an operating pressure of -0.090 - 2.5 MPaG;

[0019] The raw material gas and its molar percentage content in the ethane oxidative dehydrogenation reactor are 0 - 80% of balance gas, 15% - 80% of ethane, and 5% - 35% of oxygen.

[0020] Preferably, the reactor heat removal system uses a heat exchange medium to remove the reaction heat released by ethane oxidative dehydrogenation in real time, and the working media used include molten salt, heat transfer oil and boiler water;

[0021] The steam generation system uses boiler water to exchange heat with the heat exchange medium of the reactor, and by-produces steam after heat recovery.

[0022] Preferably, the fresh raw material ethane includes 85 mol% - 99 mol% of pure ethane, 60 mol% - 85 mol% of raw material ethane gas-containing, ethane-containing tail gas (such as the tail gas from the deethanizer in the propane dehydrogenation to propylene process and method); when the fresh raw material ethane is pure ethane, the fresh raw material ethane is directly sent to the first feed mixer; when the fresh raw material ethane is raw material ethane gas-containing or ethane-containing tail gas with heavy components, the fresh raw material ethane first enters the heavy removal tower through a by-pass line for removing heavy components, and the obtained refined ethane is sent to the first feed mixer;

[0023] The balance gas is used to dilute and balance the raw material ethane and oxygen, and control the explosion limit of the mixed gas, including water vapor, CO 2 , N 2 , air, argon and methane.

[0024] Preferably, the raw material gas preheater is used to heat the mixed raw material gas to 80 - 450 °C by using the heat in the reaction gas, while the temperature of the reaction gas is reduced to 100 - 250 °C; realizing the efficient utilization of energy.

[0025] The raw material gas heater is used to further heat the raw material gas to the initial reaction temperature of 200 - 475 °C and then introduce it into the reactor. The heater types include electric heaters, heating furnaces, etc.

[0026] The first feed mixer is used to receive and mix the reaction raw material gases such as balance gas and ethane, and after mixing evenly, introduce them into the raw material gas preheater. The second feed mixer is used to receive and mix the reaction raw material gases such as oxygen, balance gas and ethane, and after mixing evenly, introduce them into the reaction system.

[0027] Preferably, the reaction gas cooling system includes multiple heat exchangers connected in series or parallel, and uses different heat transfer media to recover the medium and low temperature energy of the product gas; the number of heat exchangers is 2 - 5, and the heat transfer media include process media, boiler water, organic power generation media, warm water and circulating water;

[0028] The temperature of the reaction gas entering the reaction gas cooling system is 100 - 250 °C, and the temperature of the reaction gas leaving the reaction gas cooling system is 20 - 80 °C.

[0029] The liquid separation tank separates the acetic acid-containing condensate in the reaction gas from the product gas, and the gas enters the CO 2 removal system, and the liquid is discharged into the wastewater treatment system.

[0030] Preferably, the CO 2 removal system is used to remove and desorb the CO 2 in the product gas by using an absorbent, including a CO 2 absorption tower and a CO 2 desorption tower connected in series; realizing a CO 2 removal rate of more than 99%.

[0031] The absorbent is MEA, MDEA, mixed MEA / MDEA, potassium carbonate solution, ionic liquid, etc.;

[0032] The absorption tower uses the absorbent to absorb the CO 2 in the product gas, and the remaining product gas goes to the downstream system, and the obtained CO 2 rich liquid enters the desorption tower for CO 2Desorption: The lean absorbent liquid at the bottom of the desorption tower returns to the absorption tower, and the rich CO gas is obtained at the top of the desorption tower and sent out; when using CO as the equilibrium gas, part of the CO is recycled back to the reaction unit, and the rest is sent out. 2 When using CO 2 as the equilibrium gas, part of the CO 2 is recycled back to the reaction unit, and the rest is sent out.

[0033] Preferably, the compression and caustic scrubbing system is used to compress and caustic scrub the product gas after removing CO, and includes a product gas compressor and a caustic scrubbing tower connected in series or parallel; 2 The product gas compressor is used to compress the product gas. According to different compression ratio requirements, the number of operating stages of the product gas compressor includes 2 to 5 stages, and the operating pressure at the outlet of the product gas compressor is 1.5 to 4.5 MPaG;

[0034] The caustic scrubbing tower uses an alkali solution with a concentration of 5% to 40% to further remove acidic gases (including H2S, CO2, etc.) in the product gas, ensuring that the product gas smoothly enters the subsequent cold box system. The alkali solution used for caustic scrubbing is a NaOH solution, etc.;

[0035] The process layout position of the caustic scrubbing tower is at least one of the outlets of the first stage, second stage, third stage, and the outlet of the product gas compressor of the product gas compressor. 2 S, CO 2 etc.), ensuring that the product gas smoothly enters the subsequent cold box system. The alkali solution used for caustic scrubbing is a NaOH solution, etc.;

[0036] The process layout position of the caustic scrubbing tower is at least one of the outlets of the first stage, second stage, third stage, and the outlet of the product gas compressor of the product gas compressor.

[0037] The first dryer removes the saturated water carried in the product gas and sends the dried reaction gas into the deoxygenation bed.

[0038] The deoxygenation bed removes a small amount of excessive oxygen in the reaction, improving the safety performance of the process of the present invention. The types of deoxygenation beds include catalytic deoxygenation beds, chemical adsorption beds, activated carbon deoxygenation beds, etc. When the oxygen in the reaction system is completely reacted, this deoxygenation bed can be considered to be cancelled.

[0039] The selective hydrogenation tower converts the by-product acetylene in the reaction into olefins or alkanes, which is beneficial to the subsequent product purification and separation, reduces the acetylene content, and improves the purity of the ethylene product.

[0040] The upstream and downstream process position relationship between the deoxygenation bed and the selective hydrogenation tower can be interchanged according to the actual situation.

[0041] The second dryer removes the water that may be generated during the hydrogenation process so that the product gas can enter the cold box system for low-temperature condensation separation of the product gas.

[0042] The cold box system performs low-temperature condensation on the dried product gas and simultaneously recovers the low-temperature cold energy of the process logistics in the system.

[0043] Preferably, the light component removal column uses distillation operation to separate the CO and methane-rich light components in the reaction gas from the top of the column, and send them out as fuel gas or intermediate products; when using N 2 as the balance gas, the light components at the top of the column first enter the light component treatment system for combustion treatment to convert the organic matter into CO 2 and water, and discharge them after reaching the standard; the crude ethylene and ethane liquid obtained at the bottom of the light component removal column are discharged from the bottom of the column and sent to the ethylene refining column;

[0044] The operating pressure of the light component removal column is 0.1 - 6.0 MPaG;

[0045] The ethylene refining column is used to separate the ethylene, ethane and a small amount of heavy components discharged from the bottom of the light component removal column. The ethylene product is distilled out from the top of the column, with a concentration reaching over 99.95% wt. The ethane and other heavy components are discharged from the bottom of the column and enter the heavy component removal column; the operating pressure of the ethylene refining column is 0.1 - 4.0 MPaG;

[0046] The heavy component removal column is used to rectify and separate the ethane and other heavy components discharged from the bottom of the ethylene column. The heavy components are discharged from the bottom of the column, and the ethane is distilled out from the top of the column; when there are more heavy components in the raw material ethane, the fresh raw material ethane enters the heavy component removal column for heavy component removal through the cross line first, and the obtained raw material ethane is returned to the reaction system; the operating pressure of the heavy component removal column is 0.1 - 3.5 MPaG;

[0047] The light component treatment system is used to, when using N 2 as the balance gas, first carry out combustion treatment on the CO and methane in the light components at the top of the light component removal column to convert them into CO 2 and water, and after heat recovery, the flue gas is discharged up to the standard.

[0048] The process of the present invention is applicable to various balance gases, with strong adaptability to the balance gas and high process flexibility.

[0049] In the present invention, the reaction gas cooling system recovers the medium and low temperature energy of the product gas through multiple heat exchange devices using different heat exchange media, with high energy recovery efficiency and low process energy consumption. The CO 2 removal system uses an absorbent to remove and desorb the CO in the product gas. When using CO 2 as the balance gas, the rich CO after desorption can be recycled, reducing the consumption of fresh balance gas in the device and reducing the discharge of the three wastes of the device. The compression and caustic washing system compresses and caustic washes the product gas after removing CO 2 . While pressurizing the product gas, it removes H 2 S and CO 2 . While pressurizing the product gas, it removes H 2 S, CO 2completely remove acidic gases such as...; In the present invention, the product gas compression process is coupled with the caustic scrubbing process. The caustic scrubbing process can be arranged between different compressor stages according to the composition of the product gas, and has the characteristics of good absorption effect and strong process flexibility. The deoxygenation bed removes a small amount of excessive oxygen in the reaction to improve the safety performance of the process of the present invention. The selective hydrogenation tower removes acetylene through a hydrogenation reaction, which is beneficial to the subsequent separation of ethylene products and improves the purity of ethylene products. The light component removal tower separates light components such as CO, methane, and balance gas nitrogen (when air or nitrogen is used as the balance gas) generated by side reactions in the system from ethylene and ethane through a single distillation column. Compared with other technologies, it has the advantages of simple separation process, mature process, and simple operation. The heavy component removal tower can not only complete the refining treatment of the recycled ethane but also perform the pre-removal of heavy components on the fresh raw material ethane with a high content of heavy components. The refined ethane is sent to the raw material mixer and enters the next cycle process. The heavy component removal tower can reduce the throughput of heavy components in the reactor, avoid the accumulation of heavy components in the system, reduce the generation of other by-products, and the occurrence of coking problems of the reactor catalyst. When the process and method use CO 2 or steam as the balance gas, CO 2 or steam in the system can be removed and recycled before the compression caustic scrubbing system, greatly reducing the subsequent gas treatment volume, reducing the utility consumption of the compressor and cold box, and effectively reducing the process energy consumption, equipment investment, and operation cost of the compression system, cold box system, and refining and separation system.

[0050] Compared with the prior art, the advantages of the present invention are as follows: The present invention adds a deoxygenation bed and a selective hydrogenation tower after the drying tower to remove oxygen and unsaturated hydrocarbons such as acetylene in the reaction gas respectively. While improving the safety of the process flow, the purity of the product ethylene is improved; A single light component removal tower is used to separate light components such as CO, methane, and balance gas nitrogen (when air or nitrogen is used as the balance gas) generated by side reactions in the system from components such as ethylene and ethane, and the separation process is simple; The present invention adds a heavy component removal tower after the ethylene tower. While completing the refining treatment of the excessive ethane in the reaction, the fresh raw material ethane also undergoes pre-removal of heavy components through this tower, avoiding the accumulation of heavy components in the system, reducing the generation of other by-products, and the occurrence of coking problems of the reactor catalyst; When the present invention uses CO 2 or steam as the balance gas, CO 2 or steam in the system can be separated and recycled before the product gas compression system, greatly reducing the subsequent gas treatment volume, and reducing the equipment investment and operation cost of the compression and distillation unit systems;

[0051] The process method of the present invention can be adapted to common balance gases such as air, nitrogen, CO 2 , steam, methane, etc., with good flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Process flow chart of an embodiment of the present invention;

[0053] Figure 2 Process flow chart of Embodiment 1 of the present invention;

[0054] Figure 3 Process flow chart of Embodiment 2 of the present invention;

[0055] Figure 4 Process flow chart of Embodiment 3 of the present invention. Detailed implementation manners

[0056] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

[0057] As Figure 1 shown, the system equipment adopted in the ethane oxidative dehydrogenation process of the present invention includes a first feed mixer 4, a raw material gas preheater 5, a raw material gas heater 6, a second feed mixer 7, a reaction system 8 (reactor 8-1, reactor heat removal system 8-2, steam generation system 8-3), a reaction gas cooling system 9, a liquid separation tank 10, a CO 2 removal system 12 (CO 2 absorption tower 12-1, CO 2 desorption tower 12-2), a compression and caustic washing system 15 (product gas compressor 15-1, caustic washing tower 15-2), a first dryer 18, a deoxidation bed 19, a hydrogenation tower 21, a second dryer 22, a cold box system 23, a light component removal tower 25, an ethylene purification tower 26, a heavy component removal tower 28, and a light component treatment system 31. The specific connection structure is consistent with the following process.

[0058] The ethane oxidative dehydrogenation process of the present invention includes the following steps:

[0059] (1) Fresh raw material ethane 3 and balance gas 1 are evenly mixed in the first feed mixer 4, after heat exchange with the product gas in the raw material gas preheater 5, reheated by the raw material gas heater 6, and then evenly mixed with oxygen 2 in the second feed mixer 7 and introduced into the reaction system 8 for reaction;

[0060] (2) After the reaction, the resulting reaction gas is heat-exchanged in the raw material gas preheater 5 and then enters the reaction gas cooling system 9 for energy recovery and cooling, and then sent to the liquid separation tank 10. The acetic acid-containing liquid 11 is discharged to the waste liquid treatment system, and the gas enters the CO 2 removal system 12. After removing CO 2 , the gas is sent to the compression and caustic washing system 15 to compress the product gas and perform deep CO 2 removal;

[0061] (3) The wastewater 16 between the compression stages of the compressed caustic scrubbing system 15 and the spent caustic liquor 17 at the bottom of the caustic scrubbing tower go to the wastewater treatment system. The compressed product gas enters the first dryer 18 for drying, then passes through the deoxygenation bed 19 to remove the excessive oxygen in the reaction, and then is sent to the selective hydrogenation tower 21. After hydrogenating to remove acetylene, it is dehydrated again through the second dryer 22. The dried gas enters the cold box system 23 for cooling the product gas, and the cooled product gas then enters the de-lighting tower 25;

[0062] (4) The light components such as CO, methane, N 2 etc. separated from the top of the de-lighting tower 25 are sent out after heat exchange through the cold box system 23. When the process uses N 2 as the diluent gas, the light component treatment system 31 can be used first, and the treated light components are discharged after meeting the standards. The ethylene, ethane and heavy components obtained at the bottom of the de-lighting tower 25 enter the ethylene purification tower 26 for the purification and separation of ethylene products;

[0063] (5) The ethylene product 27 separated from the top of the ethylene purification tower 26 is transported out of the battery limit. The ethane and heavy components discharged from the bottom of the tower are sent together with the supplemented fresh raw material ethane 3 to the de-heavy tower 28 for ethane recovery and purification; the gaseous ethane separated from the top of the de-heavy tower is recycled back to the first feed mixer 4 for the next reaction cycle, and the heavy components are separated at the bottom of the tower.

[0064] Preferably, the reaction system includes an ethane oxidative dehydrogenation reactor 8-1, a reactor heat removal system 8-2, and a steam generation system 8-3 connected in series, which are used for the oxidative dehydrogenation reaction of the raw material ethane gas to produce ethylene, remove the reaction heat, and by-product steam.

[0065] Preferably, the structural type of the ethane oxidative dehydrogenation reactor 8-1 is any one of fluidized bed, packed bed, fixed bed, and shell and tube type. The tube box in the reaction section of the shell and tube type ethane oxidative dehydrogenation reactor 8-1 is a heat exchange tube filled with catalyst. Ethane undergoes oxidative dehydrogenation reaction under the action of the catalyst to produce ethylene and by-products;

[0066] The operating conditions of the reaction section of the ethane oxidative dehydrogenation reactor 8-1 are an operating temperature of 200-500 °C and an operating pressure of -0.090-2.5 MPaG;

[0067] The raw material gas and its molar percentage content in the ethane oxidative dehydrogenation reactor 8-1 are 0-80% of balance gas, 15%-80% of ethane, and 5%-35% of oxygen.

[0068] Preferably, the reactor heat removal system 8-2 uses a heat exchange medium to remove the reaction heat release of ethane oxidative dehydrogenation in real time, and the working media used include molten salt, heat transfer oil, and boiler water;

[0069] The steam generation system 8-3 uses boiler water to exchange heat with the heat exchange medium of the reactor, and by-product steam is produced after heat recovery.

[0070] Preferably, the fresh feedstock ethane includes 85 mol% to 99 mol% of pure ethane, 60 mol% to 85 mol% of ethane-containing feedstock gas, and ethane-containing tail gas (such as the tail gas from the deethanizer in the propane dehydrogenation to propylene process and method); when the fresh feedstock ethane is pure ethane, the fresh feedstock ethane is directly sent to the first feed mixer 4; when the fresh feedstock ethane is ethane-containing feedstock gas or ethane-containing tail gas with heavy components, the fresh feedstock ethane first enters the deheavy tower 28 through a by-pass line for removal of heavy components, and the refined ethane obtained is sent to the first feed mixer 4;

[0071] The balance gas is used to dilute and balance the feedstock ethane and oxygen to control the explosion limit of the mixed gas, and includes steam, CO 2 、N 2 、air, argon, and methane.

[0072] Preferably, the feedstock gas preheater 5 is used to heat the mixed feedstock gas to 80 - 450 °C by using the heat in the reaction gas, while the temperature of the reaction gas is reduced to 100 - 250 °C; to achieve efficient energy utilization.

[0073] The feedstock gas heater 6 is used to further heat the feedstock gas to the initial reaction temperature of 200 - 475 °C and then feed it into the reactor. The heater types include electric heaters, heating furnaces, etc.

[0074] The first feed mixer 4 is used to receive and mix the reaction feedstock gases such as balance gas and ethane, and after mixing evenly, feed them into the feedstock gas preheater. The second feed mixer 7 is used to receive and mix the reaction feedstock gases such as oxygen, balance gas, and ethane, and after mixing evenly, feed them into the reaction system.

[0075] Preferably, the reaction gas cooling system 9 includes multiple heat exchangers connected in series or in parallel, and uses different heat exchange media to recover the medium and low temperature energy of the product gas; the number of heat exchangers is 2 - 5, and the heat exchange media include process media, boiler water, organic power generation media, warm water, and circulating water;

[0076] The temperature of the reaction gas entering the reaction gas cooling system is 100 - 250 °C, and the temperature of the reaction gas leaving the reaction gas cooling system is 20 - 80 °C.

[0077] The liquid separation tank 10 separates the acetic acid-containing condensate in the reaction gas from the product gas, the gas enters the CO 2 removal system 12, and the liquid is discharged into the wastewater treatment system.

[0078] Preferably, the CO 2 removal system 12 is used to use an absorbent to remove CO in the product gas 2Removal and desorption are carried out, including CO in series 2 absorption tower 12-1 and CO 2 desorption tower 12-2; achieving a CO 2 removal rate of more than 99%.

[0079] The absorbent is MEA, MDEA, mixed MEA / MDEA, potassium carbonate solution, ionic liquid, etc.;

[0080] Absorption tower 12-1 uses the absorbent to absorb CO in the product gas 2 The remaining product gas goes to the downstream system, and the obtained CO 2 rich liquid enters desorption tower 12-2 for CO 2 desorption. The lean liquid of the absorbent at the bottom of desorption tower 12-2 returns to absorption tower 12-1, and rich CO is obtained at the top of desorption tower 12-2 2 gas is sent out; when using CO 2 as the balance gas, part of the CO 2 is recycled back to the reaction unit, and the rest is sent out.

[0081] Preferably, the compression and caustic washing system 15 is used to compress and caustic wash the product gas after removing CO 2 including the product gas compressor 15-1 and caustic washing tower 15-2 in series or parallel;

[0082] The product gas compressor 15-1 is used to compress the product gas. According to different compression ratio requirements, the number of operating stages of the product gas compressor 15-1 includes 2 to 5 stages, and the operating pressure at the outlet of the product gas compressor 15-1 is 1.5 to 4.5 MPaG;

[0083] The caustic washing tower 15-2 uses an alkali solution with a concentration of 5% to 40% to further remove acidic gases (including H 2 S, CO 2 etc.) in the product gas to ensure that the product gas smoothly enters the subsequent cold box system. The alkali solution used for caustic washing is NaOH solution, etc.;

[0084] The process layout position of the caustic washing tower 15-2 is at least one of the outlets of the first stage, second stage, third stage of the product gas compressor, and the outlet of the compressor.

[0085] The first dryer 18 removes the saturated water carried in the product gas and sends the dried reaction gas to the deoxygenation bed.

[0086] The deoxygenation bed 19 removes a small amount of excess oxygen in the reaction to improve the safety production performance of the process of the present invention. The types of the deoxygenation bed include catalytic deoxygenation bed, chemical adsorption bed, activated carbon deoxygenation bed, etc. When the oxygen in the reaction system is completely reacted, the deoxygenation bed 19 can be considered to be cancelled.

[0087] The selective hydrogenation tower 21 converts the acetylene by-produced in the reaction into olefins or alkanes, which is beneficial to the subsequent purification and separation of products, reduces the acetylene content, and improves the purity of ethylene products.

[0088] The upstream and downstream process position relationship between the deoxygenation bed 19 and the selective hydrogenation tower 21 can be interchanged according to the actual situation.

[0089] The second dryer 21 removes the water that may be generated during the hydrogenation process, so that the product gas can enter the cold box system for low-temperature condensation separation of the product gas.

[0090] The cold box system 24 performs low-temperature condensation on the dried product gas, and at the same time recovers the low-temperature cold energy of the process logistics in the system.

[0091] Preferably, the light component removal tower 25 uses distillation operation to separate the CO and methane-rich CO light components in the reaction gas from the top of the tower, and sends them out as fuel gas or intermediate products; when N 2 is used as the balance gas, the light components at the top of the tower first enter the light component treatment system 31 for combustion treatment, convert the organic matter into CO2 and water, and discharge them after reaching the standard; the crude liquid of ethylene and ethane obtained at the bottom of the light component removal tower is discharged from the bottom of the tower and sent to the ethylene refining tower;

[0092] The operating pressure of the light component removal tower 25 is 0.1 - 6.0 MPaG;

[0093] The ethylene refining tower 26 is used to separate the ethylene, ethane and a small amount of heavy components discharged from the bottom of the light component removal tower. The ethylene product is distilled out from the top of the tower, and the concentration reaches more than 99.95% wt. The ethane and other heavy components are discharged from the bottom of the tower and enter the heavy component removal tower; the operating pressure of the ethylene refining tower is 0.1 - 4.0 MPaG;

[0094] The heavy component removal tower 28 is used to rectify and separate the ethane and other heavy components discharged from the bottom of the ethylene tower. The heavy components are discharged from the bottom of the tower, and the ethane is distilled out from the top of the tower; when there are many heavy components in the raw material ethane, the fresh raw material ethane first enters the heavy component removal tower through the cross-line for heavy component removal, and the obtained raw material ethane is returned to the reaction system; the operating pressure of the heavy component removal tower 28 is 0.1 - 3.5 MPaG;

[0095] The light component treatment system 31 is used to, when N 2 is used as the balance gas, first perform combustion treatment on the CO and methane in the light components at the top of the light component removal tower 25, convert them into CO 2 and water, and after heat recovery, the flue gas is discharged up to the standard.

[0096] The advantages of the process of the present invention are described in detail below using different balance gases and corresponding plant production examples.

[0097] Example 1:

[0098] As shown Figure 2 in the figure, taking the ethane oxidative dehydrogenation to ethylene plant with a scale of 400,000 tons / year as an example, and using water vapor as the equilibrium gas, the process for ethane oxidative dehydrogenation to ethylene includes the following steps:

[0099] 2064 kmol / h of fresh feed ethane 3 (calculated as pure ethane), 936 kmol / h of recycled ethane and 5000 kmol / h of water vapor 1 are evenly mixed in the first feed mixer 4, and after being heat-exchanged with the product gas in the feed gas preheater 5 to 200°C - 450°C, they are reheated to 250 - 475°C by the feed gas heater 6, and then are evenly mixed with 2000 kmol / h of oxygen 2 in the second feed mixer 7 and introduced into the reaction system 8 for reaction. In the reaction system, the operating temperature in the ethane oxidative dehydrogenation reactor 8-1 is 250 - 500°C, and the operating pressure is -0.090 - 2.0 MPaG. After the reaction, the reaction gas is heat-exchanged to 150 - 250°C in the feed gas preheater 5 and then enters the reaction gas cooling system 9 for medium and low temperature energy recovery. After being cooled to 20 - 80°C, it is sent to the liquid separation tank 10, and the acetic acid-containing liquid 11 is discharged to the waste liquid treatment system. The gas enters the CO 2 removal system 12 to remove CO 2 After that, the gas is sent to the compression and caustic scrubbing system 15 to compress the product gas and deeply remove CO 2 . The wastewater 16 between the compression stages and the spent caustic liquor 17 at the bottom of the caustic scrubbing tower go to the wastewater treatment system. The number of operating stages of the product gas compressor is 4 stages, and the operating pressure at the outlet of the product gas compressor is 2.0 - 4.5 MpaG. The compressed product gas then enters the first dryer 18 for drying, and then passes through the deoxygenation bed 19 to remove the excessive oxygen in the reaction, and then is sent to the selective hydrogenation tower 21. After hydrogenating and removing acetylene, it is dehydrated again through the second dryer 22. The dried gas enters the cold box system 23 for product gas cooling. The operating temperature of the process stream in the cold box system is between -150°C and 20°C. The cooled product gas then enters the light component removal tower 25. The light components such as CO and methane separated from the top of the light component removal tower 25 are sent out after heat exchange through the cold box system 24. The ethylene, ethane and a small amount of heavy components obtained at the bottom enter the ethylene purification tower. The operating pressure of the light component removal tower is 0.4 - 5.0 MpaG. The crude ethylene liquid is then refined and separated in the ethylene purification tower 26. Ethylene product 26 with an annual output of 400,000 tons and a purity of 99.95 wt% is separated from the top and shipped out of the battery limit. The ethane and a small amount of heavy components discharged from the bottom are introduced into the heavy component removal tower 28 together with the supplemented fresh feed ethane for ethane recovery and purification. The operating pressure of the ethylene purification tower is 0.4 - 4.0 MPaG. The gaseous ethane (936 kmol / h) separated from the top of the heavy component removal tower is recycled back to the first feed mixer 4 for the next reaction cycle, and the heavy components are separated from the bottom. The operating pressure of the heavy component removal tower is 0.4 - 3.5 MpaG.

[0100] In this embodiment, water vapor is used as the equilibrium gas, and the medium-pressure steam by-produced during the reaction process is used as the source, eliminating the need to add additional power equipment for the recycling of the equilibrium gas. During the CO 2 removal process, only the CO 2 generated within the process needs to be absorbed and desorbed. The system has a small processing capacity and low energy consumption. The light-component gas obtained at the top of the light-component removal tower is a CO-rich gas, eliminating the need to equip a light-component gas treatment system. This gas can be sent out as a by-product, offering good economic benefits. Using water vapor as the equilibrium gas, the equilibrium gas is treated before the compression system. Subsequently, the gas treatment volume of the compression, cooling, and rectification separation systems is small, with low energy consumption and less equipment investment. Therefore, this embodiment has the advantages of a short process flow, fewer equipment units, mature process technology, less equipment investment, low energy consumption, and good economic benefits.

[0101] Example 2:

[0102] As Figure 3 shown, taking a 400,000-ton / year ethane oxidative dehydrogenation to ethylene plant as an example with CO 2 as the equilibrium gas, the ethane oxidative dehydrogenation to ethylene process includes the following steps:

[0103] 2064 kmol / h of fresh feed ethane 3 (in pure ethane), 936 kmol / h of recycled ethane, and 5000 kmol / h of equilibrium gas CO 2 1 are mixed evenly in the first feed mixer 4, heated to 200 °C - 450 °C in the feed gas preheater 5 by exchanging heat with the product gas, then reheated to 250 - 475 °C in the feed gas heater 6, and mixed evenly with 2000 kmol / h of oxygen 2 in the second feed mixer 7, and then introduced into the reaction system 8 for reaction. In the ethane oxidative dehydrogenation reactor 8-1 in the reaction system, the operating temperature is 250 - 500 °C, and the operating pressure is -0.090 - 2.0 MPaG. After the reaction, the reaction gas is cooled to 150 - 250 °C in the feed gas preheater 5 and then enters the reaction gas cooling system 9 for medium- and low-temperature energy recovery. After being cooled to 20 - 80 °C, it is sent to the liquid separation tank 10, where the acetic acid-containing liquid 11 is discharged to the waste liquid treatment system. The gas enters the CO 2 removal system 12, and the gas after removing CO 2 is sent to the compression and caustic washing system 15 to compress the product gas and perform deep CO 2Removal: The inter-stage wastewater 16 of the compression section and the spent caustic liquor 17 at the bottom of the caustic scrubber are sent to the wastewater treatment system. The product gas compressor has 4 operating stages, and the operating pressure at the outlet of the product gas compressor is 2.0 - 4.5 MpaG. The compressed product gas enters the first dryer 18 for drying, then passes through the deoxygenation bed 19 to remove the excessive oxygen in the reaction, and then is sent to the selective hydrogenation tower 21. After hydrogenating to remove acetylene, it is dehydrated through the second dryer 22, and the dried gas enters the cold box system 23 for product gas cooling. The operating temperature of the process logistics in the cold box system is between -150°C and 20°C. The cooled product gas then enters the light component removal tower 25. The light components such as CO and methane separated from the top of the light component removal tower 25 are sent out after heat exchange through the cold box system 24. The ethylene, ethane and a small amount of heavy components obtained at the bottom of the tower enter the ethylene purification tower. The operating pressure of the light component removal tower is 0.4 - 5.0 MpaG. The crude ethylene liquid is refined and separated for ethylene products in the ethylene purification tower 26. The ethylene product 26 with an annual output of 400,000 tons and a purity of 99.95 wt% is separated from the top of the tower and transported out of the battery limit. The ethane and a small amount of heavy components discharged from the bottom of the tower are sent to the heavy component removal tower 28 together with the supplemented fresh raw material ethane for ethane recovery and purification. The operating pressure of the ethylene purification tower is 0.4 - 4.0 MPaG. The gaseous ethane (936 kmol / h) separated from the top of the heavy component removal tower is recycled back to the first feed mixer 4 for the next reaction cycle, and the heavy components are separated at the bottom of the tower. The operating pressure of the heavy component removal tower is 0.4 - 3.5 MpaG.

[0104] In this embodiment, CO 2 is used as the equilibrium gas, and the CO 2 gas generated during the reaction process is gradually accumulated and used as the equilibrium gas for the reaction process, effectively utilizing CO 2 and reducing the process carbon emissions. The light component gas obtained from the top of the light component removal tower is a CO-rich gas, and there is no need to equip a light component gas treatment system. This gas can be sent out as a by-product, having good economic benefits. Using CO 2 as the equilibrium gas, the wastewater treatment volume of the whole process is small, and the equilibrium gas is treated before the compression system. The gas treatment volume of the subsequent compression, cooling and rectification separation systems is small, with low energy consumption and less equipment investment. Therefore, this embodiment has the advantages of short process flow, few equipment, mature process technology, less equipment investment, low energy consumption and good economic benefits.

[0105] Example 3:

[0106] As Figure 4 shown, using N 2 as the equilibrium gas, taking the ethane oxidative dehydrogenation to ethylene process with a scale of 400,000 tons / year as an example, the ethane oxidative dehydrogenation to ethylene process includes the following steps:

[0107] 2064 kmol / h of fresh feed ethane 3 (pure ethane basis), 936 kmol / h of recycled ethane and 5000 kmol / h of equilibrium gas N 2 1 are mixed evenly in the first feed mixer 4, heat-exchanged with the product gas in the feed gas preheater 5 to 200 °C to 450 °C, then reheated to 250 - 475 °C in the feed gas heater 6, and fed into the second feed mixer 7 together with 2000 kmol / h of oxygen 2 and mixed evenly, and then fed into the reaction system 8 for reaction. If N 2 in the air is used as the equilibrium gas, 2064 kmol / h of fresh feed ethane 3 (pure ethane basis) and 6410 kmol / h of air 1 are mixed evenly in the first feed mixer 4, heat-exchanged with the product gas in the feed gas preheater 5 to 200 °C to 450 °C, then reheated to 250 - 475 °C in the feed gas heater 6, and fed into the second feed mixer 7 together with an additional 654 kmol / h of oxygen 2 and mixed evenly, and then fed into the reaction system 8 for reaction.

[0108] In the reaction system, the operating temperature in the ethane oxidative dehydrogenation reactor 8-1 is 250 - 500 °C, and the operating pressure is -0.090 - 2.0 MPaG. After the reaction, the reaction gas is heat-exchanged in the feed gas preheater 5 to 150 - 250 °C and then enters the reaction gas cooling system 9 for medium and low temperature energy recovery. After being cooled to 20 - 80 °C, it is sent to the liquid separation tank 10, and the acetic acid-containing liquid 11 is discharged to the waste liquid treatment system. The gas enters the CO 2 removal system 12 to remove CO 2 The gas after removal is sent to the compression and caustic washing system 15 to compress the product gas and perform deep CO 2 removal. The inter-stage wastewater 16 of the compression section and the spent caustic liquor 17 at the bottom of the caustic washing tower go to the wastewater treatment system. The operating stage number of the product gas compressor is 4 stages, and the operating pressure at the outlet of the product gas compressor is 2.0 - 4.5 MpaG. The compressed product gas then enters the first dryer 18 for drying, passes through the deoxygenation bed 19 to remove the excessive oxygen in the reaction, and then is sent to the selective hydrogenation tower 21. After hydrogenating to remove acetylene, it is dehydrated again through the second dryer 22. The dried gas enters the cold box system 23 for product gas cooling. The operating temperature of the process streams in the cold box system is between -150 °C and 20 °C. The cooled product gas then enters the light component removal tower 25. The light components such as CO, methane, and N 2Light components such as etc. are sent to the light component treatment system after heat exchange in the cold box system 24. The treated gas can be discharged up to the standard, and the ethylene, ethane and a small amount of heavy components obtained at the bottom of the tower enter the ethylene refining tower. The operating pressure of the de-lighting tower is 0.4 - 5.0 MpaG. The crude ethylene liquid is then refined and separated into ethylene products in the ethylene refining tower 26. Ethylene products 26 with an annual output of 400,000 tons and a purity of 99.95 wt% are separated at the top of the tower and transported out of the battery limit. The ethane and a small amount of heavy components discharged at the bottom of the tower are sent to the de-heavy tower 28 together with the supplemented fresh raw material ethane for ethane recovery and refining. The operating pressure of the ethylene refining tower is 0.4 - 4.0 MPaG. The gaseous ethane (936 kmol / h) separated at the top of the de-heavy tower is recycled back to the first feed mixer 4 for the next reaction cycle, and the heavy components are separated at the bottom of the tower. The operating pressure of the de-heavy tower is 0.4 - 3.5 MpaG.

[0109] In this embodiment, N 2 is used as the balance gas, and air is used as the raw material, effectively reducing the consumption of pure oxygen raw materials and reducing the requirements for the balance gas. During the CO 2 removal process, only the CO 2 generated in the process needs to be absorbed and desorbed, and the system throughput is small. Using N 2 as the balance gas, the wastewater treatment volume of the whole process is small, but the disadvantage is that N 2 enters the subsequent compression, cooling and rectification separation processes together with the product gas, and the gas treatment volume of the post-system is large and the energy consumption is high. However, considering the advantages such as the easy availability of raw materials and the small wastewater discharge, it is taken as an alternative solution.

Claims

1. An ethane oxidative dehydrogenation process for producing ethylene, characterized in that it comprises the following steps: (1) Fresh feed ethane (3) and recycle gas (1) are evenly mixed in a first feed mixer (4). After heat exchange with the product gas in a feed gas preheater (5), they are reheated in a feed gas heater (6), and then fed into a second feed mixer (7) together with oxygen (2) for even mixing, and then fed into a reaction system (8) for reaction; (2) After the reaction, the resulting reaction gas is heat-exchanged through the feed gas preheater (5) and then enters the reaction gas cooling system (9) for energy recovery and cooling, and then is sent to the liquid separation tank (10). The acetic acid-containing liquid (11) is discharged to the waste liquid treatment system, and the gas enters the CO 2 removal system (12) to remove CO 2 from it. The gas after removal is sent to the compression and caustic washing system (15) to compress the product gas and perform deep CO 2 removal; (3) The inter-stage wastewater (16) of the compression section of the compression and caustic washing system (15) and the spent caustic liquor (17) at the bottom of the caustic washing tower are sent to a wastewater treatment system. The compressed product gas enters a first dryer (18) for drying, then passes through a deoxygenation bed (19) to remove the excessive oxygen in the reaction, and then is sent to a selective hydrogenation tower (21). After hydrogenating to remove acetylene, it is dehydrated through a second dryer (22). The dried gas enters a cold box system (23) for cooling the product gas, and the cooled product gas then enters a de-light tower (25); (4) The light components separated from the top of the de-light tower (25) are sent out after heat exchange through the cold box system (23). The ethylene, ethane and heavy components obtained at the bottom of the de-light tower (25) enter an ethylene purification tower (26) for purification and separation of ethylene products; (5) The ethylene product (27) separated from the top of the ethylene purification tower (26) is transported out of the battery limit. The ethane and heavy components discharged from the bottom of the tower are fed into a de-heavy tower (28) together with the fresh feed ethane (3) replenished for ethane recovery and purification; The gaseous ethane separated from the top of the de-heavy tower is recycled back to the first feed mixer (4) for the next reaction cycle, and the heavy components are separated at the bottom of the tower.

2. The ethane oxidative dehydrogenation process for producing ethylene according to claim 1, characterized in that: The reaction system (8) includes an ethane oxidative dehydrogenation reactor (8-1), a reactor heat removal system (8-2), and a steam generation system (8-3) connected in series, which are used for oxidative dehydrogenation reaction of the feed ethane gas to produce ethylene, removing the reaction heat, and by-product steam.

3. The ethane oxidative dehydrogenation process for producing ethylene according to claim 2, characterized in that: The structural type of the ethane oxidative dehydrogenation reactor (8-1) is any one of fluidized bed, packed bed, fixed bed, and shell-and-tube; The operating conditions of the reaction section of the ethane oxidative dehydrogenation reactor (8-1) are an operating temperature of 200~500°C and an operating pressure of -0.090~2.5MPaG; The molar percentage content of the feed gas in the ethane oxidative dehydrogenation reactor (8-1) is 0~80% of recycle gas, 15%~80% of ethane, and 5%~35% of oxygen.

4. The ethane oxidative dehydrogenation process for producing ethylene according to claim 2, characterized in that: The reactor heat removal system (8-2) uses a heat transfer medium to remove the reaction heat release of ethane oxidative dehydrogenation in real time, and the heat transfer medium used is selected from molten salt, heat transfer oil, and boiler water; The steam generation system (8-3) uses boiler water to exchange heat with the reactor heat transfer medium, and by-product steam is generated after heat recovery.

5. The ethane oxidative dehydrogenation process for producing ethylene according to any one of claims 1 to 4, characterized in that: The described fresh feedstock ethane is selected from ethane at 85 mol% - 99 mol%, ethane-containing feedstock gas at 60 mol% - 85 mol%, and ethane-containing tail gas; when the fresh feedstock ethane is ethane at 85 mol% - 99 mol%, the fresh feedstock ethane is directly sent to the first feed mixer (4); when the fresh feedstock ethane is ethane-containing feedstock gas or ethane-containing tail gas with heavy components, the fresh feedstock ethane first enters the de-heavy tower (28) through a bypass line for removal of heavy components, and the refined ethane obtained is sent to the first feed mixer (4); The balance gas is used to dilute and balance the raw material ethane and oxygen, and control the explosion limit of the mixed gas, and is selected from water vapor, CO 2 , N 2 , air, argon and methane.

6. The ethane oxidative dehydrogenation process for producing ethylene according to any one of claims 1 to 4, characterized in that: The described feedstock gas preheater (5) is used to heat the mixed feedstock gas to 80 - 450 °C by using the heat in the reaction gas, while the temperature of the reaction gas is reduced to 100 - 250 °C; The described feedstock gas heater (6) is used to further heat the feedstock gas to the initial reaction temperature of 200 - 475 °C and then feed it into the reactor.

7. The ethane oxidative dehydrogenation process for producing ethylene according to any one of claims 1 to 4, characterized in that: The described reaction gas cooling system (9) includes multiple heat exchangers connected in series or in parallel, and different heat transfer media are used for energy recovery of the product gas at medium and low temperature levels; the number of the heat exchangers is 2 - 5, and the heat transfer media are selected from boiler water, organic power generation medium, warm water, and circulating water; The temperature of the reaction gas entering the reaction gas cooling system is 100 - 250 °C, and the temperature of the reaction gas leaving the reaction gas cooling system is 20 - 80 °C.

8. The ethane oxidative dehydrogenation process for producing ethylene according to any one of claims 1 to 4, characterized in that: The described CO 2 removal system (12) is used to remove and desorb CO in the product gas by using an absorbent, and includes a CO 2 absorption tower (12-1) and a CO 2 desorption tower (12-2) connected in series; 2 ​ The described absorbent is MEA, MDEA, mixed MEA / MDEA, potassium carbonate solution, or ionic liquid; The absorption tower (12-1) uses an absorbent to absorb CO in the product gas 2 and the remaining product gas goes to the downstream system. The obtained CO 2 rich liquid enters the desorption tower (12-2) for CO 2 desorption. The lean absorbent at the bottom of the desorption tower (12-2) is returned to the absorption tower (12-1), and rich CO 2 gas is sent out from the top of the desorption tower (12-2); when using CO 2 as the balance gas, part of the CO 2 is recycled back to the reaction unit and the rest is sent out.

9. The ethane oxidative dehydrogenation process for producing ethylene according to any one of claims 1 to 4, characterized in that: The described compression and caustic scrubbing system (15) is used to compress and caustically scrub the product gas after removing CO 2 and includes a product gas compressor (15-1) and a caustic scrubbing tower (15-2) connected in series or in parallel; The described product gas compressor (15-1) is used to compress the product gas. The number of operating stages of the product gas compressor (15-1) includes 2 - 5 stages, and the operating pressure at the outlet of the product gas compressor (15-1) is 1.5 - 4.5 MPaG; The described caustic scrubber (15-2) further removes acidic gases in the product gas by using an alkali solution with a concentration of 5% - 40%. The alkali solution used for caustic scrubbing is NaOH solution; The process layout position of the described caustic scrubber (15-2) is at least one of the outlets of the first stage, second stage, and third stage of the product gas compressor.

10. The ethane oxidative dehydrogenation process for producing ethylene according to any one of claims 1 to 4, characterized in that: The described light component removal tower (25) separates light components such as CO and methane in the reaction gas from the top of the tower through rectification operation, and sends them out as fuel gas or intermediate products; when N 2 is used as the equilibrium gas, the light components at the top of the tower first enter the light component treatment system (31) for combustion treatment to convert organic substances into CO 2 and water, and then discharge them after meeting the standards; the crude ethylene and ethane liquid obtained at the bottom of the light component removal tower are discharged from the bottom of the tower and sent to the ethylene refining tower; The operating pressure of the described de-light tower (25) is 0.1 - 6.0 MPaG; The described ethylene purification tower (26) is used to separate ethylene, ethane, and a small amount of heavy components discharged from the bottom of the de-light tower. The ethylene product is distilled out from the top of the tower, with a concentration reaching more than 99.95% wt, and ethane and other heavy components are discharged from the bottom of the tower and enter the de-heavy tower; the operating pressure of the ethylene purification tower is 0.1 - 4.0 MPaG; The de - heavy - component tower (28) is used for rectifying and separating ethane and other heavy components discharged from the bottom of the ethylene tower. The heavy components are discharged from the bottom of the tower, and ethane is distilled out from the top of the tower. When there are more heavy components in the raw material ethane, the fresh raw material ethane first enters the de - heavy - component tower through a crossover line for de - heavy - component removal, and the obtained raw material ethane is returned to the reaction system. The operating pressure of the de - heavy - component tower (28) is 0.1 - 3.5 MPaG; The light component treatment system (31) is used to first burn and treat CO and methane in the light components at the top of the de-lighting tower (25) when N 2 is used as the balance gas, convert them into CO 2 and water, and after heat recovery, the flue gas meets the emission standards and is discharged.

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