Stable absorption and separation process and absorption and separation device for methanol-to-olefin

Abstract

The invention discloses a methanol-to-olefin stable absorption and separation process and an absorption and separation device, and belongs to the technical field of petrochemical engineering, the methanol-to-olefin stable absorption and separation device comprises a water washing tower, an alkaline washing tower, a three-phase separator, an absorption tower, a regeneration tower, a depropanization tower and a deethanization tower which are connected in sequence, and the tower top of the deethanization tower is connected with an ethylene product tower; the bottom of the deethanizer is connected with a propylene product tower; the water washing tower is connected with a water washing liquid inlet pipe and a gas inlet pipe; and the upper part of the absorption tower is connected with a lean circulating liquid conveying pipe. According to the invention, the absorbent is adopted to absorb C4, so that the use amount of the absorbent is greatly reduced, and therefore, both the cyclic energy consumption and the cyclic regeneration energy consumption are reduced, and not only can the energy consumption of the device be reduced, but also the investment of the device can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of petrochemical industry, and in particular, relates to a stable absorption and separation process for producing olefins from methanol and an absorption and separation device. Background Art

[0002] Ethylene and propylene are important chemical raw materials. As basic raw materials, they are widely used in the production of fibers, plastics, high-performance materials and other industries. Due to the huge methanol production in my country, the methanol-to-ethylene and propylene process is becoming an increasingly important way to synthesize ethylene and propylene. Methanol is catalytically reacted to produce hydrogen, methane, light hydrocarbons and some by-products such as ethanol, DMF, aldehydes, acids, ketones and other oxides. To separate this complex product into industrial-grade ethylene and propylene, a complex separation process is required. In an industrial production plant for methanol to olefins, the olefin separation unit accounts for about 60% of the energy consumption of the entire plant. Therefore, it is very important to reduce the energy consumption of olefin separation.

[0003] In known industrial devices, the downstream olefin separation unit of methanol to olefins mainly obtains industrial-grade ethylene and propylene products, and produces fuel gas, C4 products, and C4+ products as by-products. Industrial method 1: first remove propanation and equip with propylene refrigeration, use the propane at the bottom of the propylene tower as an absorbent to absorb the C2 and C3 components in the methanol conversion gas, and then separate the products in the subsequent deethanizer, ethylene tower, and propylene tower. This method can be summarized as a pre-depropanization plus inter-cooling propane absorption process, which is also the most widely used process at present. Industrial method 2: pre-demethanization process, first remove methane and light components such as hydrogen, and then remove ethane and propane in turn. This method requires the operating temperature of the demethanizer to be below -100°C, so it is necessary to set up an ethylene refrigeration compressor unit for deep cold separation, which has high energy consumption and investment. Industrial method three: adopting the pre-de-ethanization and inter-cooling propane absorption process, it is necessary to set up a propylene refrigeration compressor and a propane washing process. Like the pre-de-propanization and inter-cooling propane washing process, a large amount of propane circulates in the system, resulting in the dilution of the propylene concentration in the propylene tower, causing the operating cost of the propylene tower to increase and the investment to increase.

[0004] Chinese patent CN108586180B proposes a low-energy MTO product gas separation process and system, which uses unpowered deep cooling technology to recover valuable hydrocarbons such as ethylene in the tail gas of the demethanizer of the methanol to olefins product gas. This process requires deep cooling equipment to cool the liquid phase materials rich in carbon 2 and carbon 3 to -130℃~-110℃. Therefore, it is necessary to equip equipment such as cold boxes, and the manufacturing process is difficult and the investment is large.

[0005] Chinese patent CN101353286B provides a pre-depropane and pre-cut medium-temperature propane absorption process. This process requires a propylene refrigerant at a temperature of -40°C and needs to be equipped with a cold box. Although the temperature is higher than that of the deep cold process, it still requires low-temperature equipment, resulting in high equipment manufacturing costs.

[0006] In order to solve the high manufacturing cost of deep or medium-temperature deep-cold process equipment required by known industrial devices or existing patented olefin separation devices, propylene refrigeration compressors or ethylene refrigeration compressors are required, resulting in a complex system. In addition, the medium-temperature propane absorption process uses propane as an absorbent to absorb carbon 2 and carbon 3, but the solubility of carbon 2 in propane is low, so a large amount of absorbent is required for absorption. Therefore, there is an urgent need for a stable methanol to olefin absorption process that can reduce the amount of absorbent. Summary of the invention

[0007] The purpose of the present invention is to provide a stable absorption and separation process and absorption and separation device for methanol to olefins. By adopting an absorbent to absorb carbon four, the amount of absorbent used is greatly reduced, thereby reducing the cycle energy consumption and the cycle regeneration energy consumption, which can not only reduce the energy consumption of the device, but also reduce the investment in the device.

[0008] To achieve the purpose of the present invention, the technical solution adopted is:

[0009] A stable absorption and separation process for methanol to olefins comprises the following steps:

[0010] (1) The methanol conversion gas is washed with turbine condensate water under pressure to obtain deoxidized conversion gas, and the deoxidized conversion gas is absorbed by sodium hydroxide solutions of different concentrations to obtain deoxidized and deacidified conversion gas;

[0011] (2) converting the converted gas after deoxygenation and deacidification into gas-liquid two-phase and then performing gas-oil-water three-phase separation, and the separated product gas is absorbed by lean circulating liquid containing C4 and C4+ to obtain hydrogen-methane mixed gas and rich circulating liquid that absorbs C2, C3, and C4, and C4, C4, C4+, and absorbed C3 and C4 components are separated from the rich circulating liquid;

[0012] (3) The separated C4, C4+ and absorbed C3, C4 components are separated again to obtain light hydrocarbon components containing C2 and C3 and components containing C4 and C4+; the components containing C2 and C3 light hydrocarbons are separated to obtain a mixture of ethylene, ethane, and trace acetylene and a mixture of propylene and propane; the mixture of ethylene, ethane, and trace acetylene is converted into ethylene or green oil under the action of a hydrogenation catalyst; the ethylene or green oil is distilled to obtain an industrial-grade ethylene product and liquid ethane; the mixture of propylene and propane is separated to obtain industrial-grade propylene and liquid propane; the components containing C4 and C4+ are sent out as products or refluxed as lean circulating liquid to absorb the product gas separated from the three phases.

[0013] Furthermore, in step (1), the pressure of the methanol conversion gas after pressurization is 0.05MpaG to 0.08MpaG.

[0014] Furthermore, in step (1), the temperature of the methanol conversion gas before water washing is 40°C.

[0015] Furthermore, the sodium hydroxide solutions of different concentrations in step (1) are 1 wt % sodium hydroxide solution, 4 wt % sodium hydroxide solution, and 7 wt % sodium hydroxide solution, respectively.

[0016] Furthermore, the mixed gas rich in hydrogen, methane, ethylene and ethane separated from the rich circulating liquid in step (2) is cooled to obtain hydrogen and methane, and the obtained hydrogen and methane are mixed with the gas-liquid two-phase obtained by the conversion gas after deoxygenation and deacidification.

[0017] Furthermore, a mixed gas rich in hydrogen, methane, ethylene and ethane is separated from the rich circulating liquid in step (2), and is cooled to obtain a liquid phase containing C2 and C3. A portion of the liquid phase is refluxed and absorbed again with a lean circulating liquid containing C4 and C4+ to obtain a hydrogen-methane mixed gas and a rich circulating liquid that has absorbed C2, C3 and C4. The other portion is mixed with a product liquid separated from the three phases of gas, oil and water and then separated. The separated components containing C3, C4 and C4+ are mixed with the C4, C4+ and the absorbed C3 and C4 components separated from the rich circulating liquid in step (3). The mixed gas rich in hydrogen, methane, ethylene and ethane is separated from the rich circulating liquid in step (3), and is cooled to obtain a non-condensable gas, which is mixed with the product gas separated from the three phases of gas, oil and water.

[0018] Furthermore, in step (2), the pressure of the converted gas before it becomes a gas-liquid two-phase after deoxygenation and deacidification is 3.0 MPaG to 3.4 MPaG.

[0019] Furthermore, in step (2), the temperature at which the converted gas becomes a gas-liquid two-phase after deoxygenation and deacidification is 9°C to 11°C.

[0020] Furthermore, in step (2), the operating temperature of the product gas when it is absorbed by the lean circulating liquid containing C4 and C4+ is 5°C to 10°C.

[0021] Furthermore, the separation temperature of the rich circulating liquid in step (2) is 0.8MpaG to 1.2MpaG.

[0022] A stable absorption and separation device for methanol to olefins comprises a water washing tower, an alkali washing tower, a three-phase separator, an absorption tower, a regeneration tower, a depropanizer, and a deethanizer connected in sequence, wherein the top of the deethanizer is connected to an ethylene product tower, and the bottom of the deethanizer is connected to a propylene product tower; the water washing tower is connected to a water washing liquid inlet pipe and an air inlet pipe, and the upper part of the absorption tower is connected to a lean circulating liquid delivery pipe.

[0023] Furthermore, alkali solution feeding pipes capable of conveying alkali solutions of different concentrations are sequentially installed from top to bottom in the alkali washing tower.

[0024] Furthermore, a product gas dryer is installed between the three-phase separator and the absorption tower.

[0025] Furthermore, the top of the regeneration tower is connected to a regeneration tower cryogenic cooler, the outlet of the regeneration tower cryogenic cooler is connected to a regeneration tower reflux tank, the gas phase outlet of the regeneration tower reflux tank is connected to the outlet of the product gas dryer, and the liquid phase outlet of the regeneration tower reflux tank is connected to the outlet of the alkali washing tower.

[0026] Furthermore, it also includes a stabilization tower, and the liquid phase outlet of the three-phase separator is also connected to a product liquid dryer, the outlet of the product liquid dryer and the liquid phase outlet of the regeneration tower reflux tank are connected to the inlet of the stabilization tower through a product liquid heater, and the bottom of the stabilization tower is connected to the inlet of the depropanizer through the product liquid heater.

[0027] Furthermore, the top of the stabilization tower is connected to a stabilization tower cooler, the outlet of the stabilization tower cooler is connected to a stabilization tower reflux tank, the gas phase outlet of the stabilization tower reflux tank is connected to the product gas inlet of the absorption tower, and the liquid phase outlet of the stabilization tower reflux tank is connected to the upper part of the stabilization tower.

[0028] Furthermore, a stabilization tower reboiler is installed at the lower portion of the stabilization tower, and a regeneration tower reboiler is installed at the lower portion of the regeneration tower.

[0029] Furthermore, a lean circulating liquid deep cooler is installed on the lean circulating liquid delivery pipe, and a lean-rich liquid heat exchanger is installed between the absorption tower and the regeneration tower, a lean circulating liquid feed pipe connected to the lean circulating liquid deep cooler is installed on the lean-rich liquid heat exchanger, and the bottom of the depropanizer is connected to the lean circulating liquid feed pipe.

[0030] Furthermore, a conversion gas compressor 1 and a compressor inter-stage cooler are installed on the air inlet pipe, and a conversion gas compressor 2 and a conversion gas deep cooler are installed between the alkali washing tower and the three-phase separator.

[0031] Furthermore, an acetylene hydrogenation reactor is also arranged between the depropanizer and the ethylene product tower.

[0032] The beneficial effects of the present invention are:

[0033] The present invention adopts a medium-temperature propane absorption process and carbon four absorption, which greatly reduces the amount of circulating absorbent required for absorption, thereby reducing the circulation energy consumption and the circulation regeneration energy consumption, and reducing the investment in the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings illustrate exemplary embodiments of the present invention and together with the description serve to explain the principles of the present invention. These drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification.

[0035] Figure 1 This is a flow chart of the stable absorption and separation device for methanol to olefins provided by the present invention.

[0036] Markings and corresponding parts names in the attached drawings:

[0037] 1-intake pipe; 2-conversion gas compressor 1; 3-compressor inter-stage cooler; 4-water washing tower; 5-water washing liquid inlet pipe; 6-alkali washing tower; 7-conversion gas compressor 2; 8-conversion gas deep cooler; 9-three-phase separator 9; 10-product gas dryer; 11-product liquid dryer; 12-absorption tower; 13-product gas discharge pipe; 14-lean circulating liquid deep cooler; 15-lean circulating liquid delivery pipe; 16-lean and rich liquid heat exchanger; 17-regeneration tower; 18-regeneration tower deep cooler device; 19-regeneration tower reflux tank; 20-regeneration tower reboiler; 21-stabilization tower; 22-stabilization tower cooler; 23-stabilization tower reflux tank; 24-stabilization tower reboiler; 25-product liquid heater; 26-depropanizer; 27-product delivery pipe; 28-deethanizer; 29-acetylene hydrogenation reactor; 30-ethylene product tower; 31-ethylene delivery pipe; 32-ethane delivery pipe; 33-propylene product tower; 34-propylene delivery pipe; 35-propane delivery pipe. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and implementation methods. It is understood that the specific implementation methods described herein are only used to explain the relevant content, rather than to limit the present invention. It is also necessary to explain that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings.

[0039] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0040] The present invention provides a methanol to olefins stable absorption and separation device, which is used to process the conversion gas from the methanol to olefins conversion unit. The pressure of the conversion gas is 0.05MpaG to 0.08MpaG, and the conversion gas contains hydrogen, carbon monoxide, carbon dioxide, methane, ethane, ethylene, propane, propylene, C4+, and oxygen-containing compounds such as alcohols, ketones, aldehydes, and carboxylic acids.

[0041] like Figure 1 As shown, the stable absorption and separation device for methanol to olefins includes a water washing tower 4, an alkali washing tower 6, a three-phase separator 9, an absorption tower 12, a regeneration tower 17, a stabilization tower 21, a depropanizer 26, and a deethanizer 28; the lower part of the water washing tower 4 is connected with an air inlet pipe 1, and the conversion gas enters the water washing tower 4 through the air inlet pipe 1, and a conversion gas compressor 2 and a compressor inter-stage cooler 3 are also installed on the air inlet pipe 1, and the conversion gas compressor 2 is used to compress the conversion gas to 0.8MpaG, and the compressed conversion gas is then cooled to 40°C through the compressor inter-stage cooler 3; the upper part of the water washing tower 4 is connected with a water washing liquid inlet pipe 5, and the water washing liquid inlet pipe 5 is used to send washing water into the water washing tower 4, so that the washing water entering the water washing tower 4 washes the conversion gas. In the present invention, the water washing tower 4 is a packed tower, and the packing inside the water washing tower 4 is arranged in three layers from top to bottom, and the water washing liquid inlet pipe 5 is located above the packing. The main purpose is to absorb the oxygen-containing compounds of alcohols, ketones, aldehydes, and carboxylic acids in the conversion gas with water under pressure. Therefore, the washing water entering the water washing tower 4 through the water washing liquid inlet pipe 5 can use desalted water or steam turbine condensate to replace the methanol to olefins purified water used in the conventional design. In the present invention, since the oxygen-containing compounds in the conversion gas undergo polycondensation reaction in the presence and action of sodium hydroxide in the subsequent alkali washing tower 6 to generate butter, it is very important to remove the oxygen-containing compounds from the water washing tower 4. The present invention uses desalted water or steam turbine condensate as the water washing liquid for the first time, which can reduce the amount of butter produced by 80%.

[0042] The top of the water washing tower 4 is connected to the lower part of the alkali washing tower 6 through a pipeline, so that the deoxidized conversion gas generated after the conversion gas is washed in the water washing tower 4 can be sent to the lower part of the alkali washing tower 6 through the pipeline. The alkali washing tower 6 adopts a plate tower, and the alkali washing tower 6 is divided into three sections. The alkali washing tower 6 is equipped with alkali liquid feeding pipes with different concentrations of alkali liquid corresponding to the three sections. The three alkali liquid feeding pipes are respectively fed with sodium hydroxide solutions with concentrations of about 1wt%, 4wt%, and 7wt%, wherein the 1wt% concentration sodium hydroxide solution enters from the upper section of the alkali washing tower 6, the 4wt% concentration sodium hydroxide solution enters from the middle section of the alkali washing tower 6, and the 7wt% concentration sodium hydroxide solution enters from the lower section of the alkali washing tower 6. Through the cooperation of the three sodium hydroxide alkali solutions with different concentrations, the deoxidized conversion gas entering the alkali washing tower 6 can further remove acidic substances such as carbon dioxide. The present invention adopts three different concentrations of sodium hydroxide alkali solution to absorb the deoxidized conversion gas together. Compared with the traditional alkali washing process using a single concentration of alkali solution for absorption, the carbon dioxide in the deoxidized conversion gas can be completely absorbed. In addition, this segmented and concentrated absorption method reduces the risk of condensation of oxygen-containing compounds under the action of alkali solution and reduces the amount of butter generated.

[0043] The top of the alkali washing tower 6 is connected to the three-phase separator 9 by a pipeline, and a conversion gas compressor 27 and a conversion gas deep cooler 8 are also installed between the top of the alkali washing tower 6 and the three-phase separator 9, so that the conversion gas from which oxygen-containing compounds and acidic compounds are removed by the alkali washing tower 6 can be first compressed to 3.0MpaG~3.4MpaG by the conversion gas compressor 27, and then cooled to 9℃~11℃, preferably to 10℃, by the refrigeration propylene of 7℃ in the conversion gas deep cooler 8. Under this condition, the conversion gas is in a three-phase state of gas, oil and water, and enters the three-phase separator 9 in a three-phase state of gas, oil and water for three-phase separation.

[0044] The gas phase outlet of the three-phase separator 9 is connected to the product gas dryer 10, and the liquid phase outlet of the three-phase separator 9 is connected to the product liquid dryer 11, that is, the gas phase product separated by the three-phase separator 9 enters the product gas dryer 10 for drying, and the liquid phase product separated by the three-phase separator 9 enters the product liquid dryer 11 for drying. In the present invention, the product gas dryer 10 and the product liquid dryer 11 are both filled with molecular sieves, which are used to absorb moisture in the gas phase product and the liquid phase product to prevent moisture from entering the downstream system and causing unqualified products.

[0045] Since the product gas after drying by the product gas dryer 10 contains most of hydrogen, methane and part of ethylene and ethane, the top of the product gas dryer 10 is connected to the bottom of the absorption tower 12 through a pipeline. In the present invention, the absorption tower 12 is a plate tower, and the product gas after three-phase separation enters the bottom of the absorption tower 12, and the upper part of the absorption tower 12 is also connected to a lean circulating liquid delivery pipe 15, and the lean circulating liquid delivery pipe 15 is used to deliver the lean circulating absorption liquid whose main components are C4 and C4+ from the top of the absorption tower 12, so that the C2, C3 and heavier hydrocarbon substances in the product gas are absorbed by the lean circulating absorption liquid, and the top of the absorption tower 12 is also connected to a product gas discharge pipe 13, so that the non-condensable gases such as hydrogen and methane in the product gas are discharged from the product gas discharge pipe 13 at the top of the absorption tower 12. In the present invention, the operating temperature of the absorption tower 12 is 5°C to 10°C. In order to control the temperature inside the absorption tower 12, a lean circulating liquid deep cooler 14 is also installed on the lean circulating liquid delivery pipe 15, so that the lean circulating absorption liquid entering through the top of the absorption tower 12 is cooled to 5°C to 10°C by the lean circulating liquid deep cooler 14 and then enters the absorption tower 12 to absorb carbon 2, carbon 3 and heavier hydrocarbon substances in the product gas.

[0046] After the lean circulating absorption liquid entering the absorption tower 12 absorbs C2, C3 and heavier hydrocarbons in the product gas, the bottom of the absorption tower 12 is a rich circulating absorption liquid that absorbs C2, C3 and C4. The bottom of the absorption tower 12 is connected to the middle of the regeneration tower 17, and a lean-rich liquid heat exchanger 16 is installed on the pipeline used to connect the bottom of the absorption tower 12 and the middle of the regeneration tower 17, and the lean circulating liquid delivery pipe 15 is connected to the lean-rich liquid heat exchanger 16, and the lean-rich liquid heat exchanger 16 is also connected to a lean circulating liquid inlet pipe connected to the lean circulating liquid delivery pipe 15. By providing the lean-rich liquid heat exchanger 16, the rich circulating absorption liquid sent out from the absorption tower 12 can be heated when passing through the lean-rich liquid heat exchanger 16, so that the rich circulating absorption liquid enters the regeneration tower 17 after being heated.

[0047] The main function of the regeneration tower 17 is to separate carbon two and carbon three from carbon four and carbon four +, and the operating pressure of the regeneration tower 17 is 0.8MpaG~1.2MpaG. A regeneration tower reboiler 20 is installed at the lower part of the regeneration tower 17, and the outlet and the inlet of the regeneration tower reboiler 20 are both connected to the lower part of the regeneration tower 17 through a pipeline, and the top of the regeneration tower 17 is connected to a regeneration tower cryogenic cooler 18, and the outlet of the regeneration tower cryogenic cooler 18 is connected to a regeneration tower reflux tank 19, and the gas phase outlet of the regeneration tower reflux tank 19 is connected to the inlet of the conversion gas compressor 27 through a pipeline, and the liquid phase outlet of the regeneration tower reflux tank 19 is respectively connected to the upper part of the regeneration tower 17 through a pipeline, and the liquid phase outlet of the regeneration tower reflux tank 19 and the liquid phase outlet of the product liquid dryer 11 are connected to a product liquid heater 25 through a pipeline, and are connected to the middle part of the stabilization tower 21 through the product liquid heater 25. The bottom of the regeneration tower 17 is connected to the middle of the depropanizer 26 through a pipeline.

[0048] In the present invention, the regeneration tower cryogenic cooler 18 adopts 7°C refrigeration propylene cooling, and the reflux liquid and non-condensable gas cooled by the regeneration tower cryogenic cooler 18 enter the regeneration tower reflux tank 19 together, and the non-condensable gas entering the regeneration tower reflux tank 19 is mixed with the conversion gas from which oxygen-containing compounds and acidic compounds are removed by the alkali washing tower 6 through the pipeline, and then sent to the conversion gas compressor 27 for pressurization treatment again to achieve further recovery, and the reflux liquid entering the regeneration tower reflux tank 19 is divided into two parts, one part of the reflux liquid is directly returned to the upper part of the regeneration tower 17, and the other part of the reflux liquid is mixed with the liquid phase product dried by the product liquid dryer 11 and then passes through the product liquid heater 25 to enter the stabilization tower 21.

[0049] A stabilizing tower reboiler 24 is installed at the lower part of the stabilizing tower 21, and the outlet and inlet of the stabilizing tower reboiler 24 are both connected to the stabilizing tower 21 through pipelines, and the top of the stabilizing tower 21 is connected to the stabilizing tower cooler 22 through a pipeline, and the outlet of the stabilizing tower cooler 22 is connected to the stabilizing tower reflux tank 23 through a pipeline, and the gas phase outlet of the stabilizing tower reflux tank 23 is connected to the outlet of the product gas dryer 10 through a pipeline, and the liquid phase outlet of the stabilizing tower reflux tank 23 is connected to the upper part of the stabilizing tower 21 through a pipeline. The bottom of the stabilizing tower 21 is connected to the product liquid heater 25 through a pipeline, and is connected to the middle of the depropanizer 26 through a pipeline after passing through the product liquid heater 25.

[0050] The operating pressure of the stabilization tower 21 is higher than that of the absorption tower 12. Specifically, the operating pressure of the stabilization tower 21 is 3.2MpaG to 3.5MpaG. The stabilization tower 21 is a plate tower, which adopts full reflux operation, and the non-condensable gas at the top of the stabilization tower 21 is mixed with the product gas dried by the product gas dryer 10 and enters the absorption tower 12 to achieve the recovery of light hydrocarbons. The bottom of the stabilization tower 21 is mainly C2, C3, C4, and C4+ components, which are mixed with the logistics at the bottom of the regeneration tower 17 and enter the depropanizer 26.

[0051] The top of the depropanizer 26 is connected to the middle of the deethanizer 28 through a pipeline, and the bottom of the depropanizer 26 is connected to a product delivery pipe 27, which is connected to the lean circulating liquid inlet pipe through the product delivery pipe 27. The depropanizer 26 mainly separates the mixed components of C2, C3, C4, and C4+ components sent from the regeneration tower 17 and the stabilization tower 21. Through separation, the top of the depropanizer 26 is mainly C2 and C3, the bottom of the depropanizer 26 is mainly C4 and C4+, and the by-products mainly C2 and C3 are sent to the deethanizer 28. A part of the streams mainly C4 and C4+ are used as lean circulating absorption liquid, and are cooled to 5°C by the lean-rich liquid heat exchanger 16 and the lean liquid deep freezer, and then returned to the absorption tower 12 for absorption operation. Another part of the streams mainly C4 and C4+ are sent out as C4 and C4+ products through the product delivery pipe 27. In the present invention, the deethanizer 28 adopts a plate tower, the operating pressure of the deethanizer 28 is 2.2MpaG~2.4MpaG, and acetylene, ethylene and ethane components are discharged from the top of the deethanizer 28, and propylene and propane components are discharged from the bottom of the deethanizer 28.

[0052] The stable absorption and separation device for methanol to olefins also includes an ethylene product tower 30 and a propylene product tower 33; the top of the deethanizer 28 is connected to an acetylene hydrogenation reactor 29 through a pipeline, the outlet of the acetylene hydrogenation reactor 29 is connected to the middle of the ethylene product tower 30, the top of the ethylene product tower 30 is connected to an ethylene delivery pipe 31, and the bottom of the ethylene product tower 30 is connected to an ethane delivery pipe 32; the top of the propylene product tower 33 is connected to a propylene delivery pipe 34, and the bottom of the propylene product tower 33 is connected to a propane delivery pipe 35. In the present invention, the ethylene product tower 30 is provided with a pasteurization section, using a plate tower, and the operating pressure is; the propylene product tower 33 is a plate tower, and the operating pressure is 1.8MpaG.

[0053] The acetylene, ethylene and ethane component gases discharged from the top of the deethanizer 28 are sent to the acetylene hydrogenation reactor 29 through a pipeline to further remove acetylene to ensure the purity of the ethylene product, and the ethylene and ethane gases after acetylene removal from the acetylene hydrogenation reactor 29 enter the ethylene product tower 30 for separation of ethylene and ethane, and the separated industrial-grade ethylene product is sent out through the ethylene delivery pipe 31, and the separated liquid ethane is sent out through the ethane delivery pipe 32; the propylene and propane components sent out from the bottom of the deethanizer 28 are sent to the propylene product tower 33 for separation, and the separated industrial-grade propylene product is sent out through the propylene delivery pipe 34, and the separated liquid propane is sent out through the propane delivery pipe 35.

[0054] The separation process of the methanol to olefins stable absorption separation device provided by the present invention is as follows:

[0055] (1) Water washing, alkali washing and compression:

[0056] The methanol conversion gas with a pressure of 0.05MpaG is pressurized to 0.8MpaG through the conversion gas compressor 2, and the temperature of the methanol conversion gas discharged through the conversion gas compressor 2 is controlled at 90°C. After discharging the methanol conversion gas, the conversion gas compressor 2 cools it to 40°C through the compressor inter-stage cooler 3, and then enters the water washing tower 4; at the same time, the turbine condensate is sent to the upper part of the water washing tower 4 through the water washing liquid inlet pipe 5, so as to absorb the oxygen-containing compounds such as alcohol, ketone, aldehyde, acid, etc. in the methanol conversion gas, and the deoxidized conversion gas obtained after water washing is sent to the alkali washing tower 6 through a pipeline.

[0057] When the deoxidized conversion gas enters the alkali washing tower 6, a 1wt% sodium hydroxide solution is transported to the upper section of the alkali washing tower 6 through the alkali liquid feed pipe, a 4wt% sodium hydroxide solution is transported to the middle section of the alkali washing tower 6 through the alkali liquid feed pipe, and a 7wt% sodium hydroxide solution is transported to the lower section of the alkali washing tower 6 through the alkali liquid feed pipe; the deoxidized conversion gas is alkaline washed with sodium hydroxide solution, and the acidic substances such as carbon dioxide in the deoxidized conversion gas are completely absorbed to obtain a deoxygenated and deacidified conversion gas, which is then sent out from the top of the alkali washing tower 6.

[0058] The deoxygenated and deacidified conversion gas sent out from the top of the alkali washing tower 6 is compressed to 3.2MpaG by the conversion gas compressor 2 7, and the compressed deoxygenated and deacidified conversion gas enters the conversion gas deep cooler 8 and is cooled to 9.9°C, so that the deoxygenated and deacidified conversion gas enters the three-phase separator 9 in a gas-oil-water three-phase state, and the deoxygenated and deacidified conversion gas in a gas-oil-water three-phase state is separated into gas, oil and water in the three-phase separator 9, and the separated product gas is sent out from the top of the three-phase separator 9, and the separated product liquid is sent out from the bottom of the three-phase separator 9, and the sent product gas enters the product gas dryer 10 for drying, and the sent product liquid enters the product liquid dryer 11 for drying, the molecular sieve in the product gas dryer 10 absorbs the moisture in the product gas, and the molecular sieve in the product liquid dryer 11 absorbs the moisture in the product liquid.

[0059] (2) Stable absorption and regeneration:

[0060] The product gas dried by the product gas dryer 10 contains hydrogen, methane, ethylene, ethane, etc., and the dried product gas enters the absorption tower 12. The operating temperature of the absorption tower 12 is 5°C~10°C, and the operating pressure of the absorption tower 12 is 3.1MpaG; at the same time, the lean circulating liquid mainly composed of carbon four and carbon four + components enters the lean-rich liquid heat exchanger 16 through the lean circulating liquid inlet pipe, and enters the lean circulating liquid deep freezer 14 to be cooled to 5°C after passing through the lean-rich liquid heat exchanger 16. According to the principle of like dissolves like, ethylene, ethane, propylene propane and heavier hydrocarbon substances in the product gas are absorbed by the lean circulating liquid. Therefore, what is sent out through the top of the absorption tower 12 is a hydrogen-methane mixed gas, which is discharged through the product gas discharge pipe 13, and what is sent out through the bottom of the absorption tower 12 is a rich circulating liquid that has absorbed carbon two, carbon three and other substances.

[0061] Since the absorption tower 12 is operated under high pressure, there are still non-condensable dry gases such as absorbed hydrogen and methane in the rich circulating liquid, so the rich circulating liquid first enters the middle of the regeneration tower 17 after being reheated by the lean-rich liquid heat exchanger 16, and the operating pressure of the regeneration tower 17 is 0.9MpaG; through the distillation of the regeneration tower 17, a mixed gas rich in hydrogen, methane, ethylene, and ethane is extracted from the top of the regeneration tower 17, and the mixed gas enters the regeneration tower cryogenic cooler 18 for cooling, and enters the regeneration tower reflux tank 19 after cooling. The non-condensable gas entering the regeneration tower reflux tank 19 mainly contains hydrogen and methane. These non-condensable gases are sent to the inlet of the conversion gas compressor 27 through a pipeline and enter the absorption tower 12 with the deoxygenated and deacidified conversion gas and are discharged from the product gas discharge pipe 13. The heat required for the regeneration tower 17 is provided by the regeneration tower reboiler 20.

[0062] The reflux liquid extracted from the regeneration tower reflux tank 19 is mainly carbon 2 and carbon 3. This part of the reflux liquid is divided into two parts. One part of the reflux liquid is directly returned to the upper part of the regeneration tower 17, and the other part of the reflux liquid is mixed with the liquid phase product dried by the product liquid dryer 11 and then passes through the product liquid heater 25 to enter the stabilization tower 21. The stabilization tower 21 vaporizes the non-condensable dry gas such as hydrogen and methane dissolved in the liquid phase product. The non-condensable gas at the top of the stabilization tower 21 enters the stabilization tower cooler 22 for cooling, and enters the stabilization tower reflux tank 23 after cooling. The non-condensable gas entering the stabilization tower reflux tank 23 is mixed with the product gas dried by the product gas dryer 10 and enters the absorption tower 12 to further recover useful components such as ethane and ethylene, and then is discharged out of the boundary with hydrogen and methane. The heat of the stabilization tower 21 is provided by the stabilization tower reboiler 24.

[0063] The bottom liquid of the regeneration tower 17 mainly consists of circulating C4, C4+ and absorbed C3, C4 and other components. The bottom liquid of the stabilization tower 21 mainly consists of C3, C4 and C4+. The bottom liquid of the stabilization tower 21 is heated by the product liquid heater 25 and mixed with the bottom liquid of the regeneration tower 17, and then enters the depropanizer 26 after mixing. The depropanizer 26 separates C3 and below components from C3 and above components. The separated C2 and C3 light hydrocarbon components are sent to the deethanizer 28. A part of the separated C4 and C4+ is used as the lean circulating absorption liquid and is cooled to 5°C by the lean-rich liquid heat exchanger 16 and the lean liquid deep freezer, and then returned to the absorption tower 12 for absorption operation. The other part of the flow stream, which is mainly C4 and C4+, is sent out as C4 and C4+ products through the product delivery pipe 27.

[0064] (3) Product separation:

[0065] The operating pressure of the deethanizer 28 is 2.3 MPaG. Acetylene, ethylene and ethane components are discharged from the top of the deethanizer 28, and propylene and propane components are discharged from the bottom of the deethanizer 28. The acetylene, ethylene and ethane component gases discharged from the top of the deethanizer 28 are sent to the acetylene hydrogenation reactor 29 through a pipeline to further remove acetylene. Under the action of the hydrogenation catalyst, acetylene is converted into ethylene or green oil. The ethylene and ethane gases after acetylene removal in the acetylene hydrogenation reactor 29 enter the ethylene product tower 30 for ethylene production. For the separation of ethylene and ethane, the operating pressure of the ethylene product tower 30 is 2.0 MpaG, and the separated industrial-grade ethylene product is sent out through the ethylene delivery pipe 31, and the separated liquid ethane is sent out through the ethane delivery pipe 32; the propylene and propane components sent out from the bottom of the deethanizer 28 are sent to the propylene product tower 33 for separation, and the operating pressure of the propylene product tower 33 is 1.8 MpaG, the separated industrial-grade propylene product is sent out through the propylene delivery pipe 34, and the separated liquid propane is sent out through the propane delivery pipe 35.

[0066] In the description of this specification, the description with reference to the terms "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments / methods or examples. In addition, those skilled in the art may combine and combine the different embodiments / methods or examples described in this specification and the features of the different embodiments / methods or examples, unless they are contradictory.

[0067] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0068] It should be understood by those skilled in the art that the above embodiments are only for the purpose of clearly illustrating the present invention, and are not intended to limit the scope of the present invention. For those skilled in the art, other changes or modifications may be made based on the above disclosure, and these changes or modifications are still within the scope of the present invention.

Claims

1. A stable absorption and separation process for methanol to olefins, characterized in that: The steps include: (1) The methanol conversion gas is washed with turbine condensate water under pressure to obtain deoxidized conversion gas, and the deoxidized conversion gas is absorbed by sodium hydroxide solutions of different concentrations to obtain deoxidized and deacidified conversion gas; (2) converting the converted gas after deoxygenation and deacidification into gas-liquid two-phase and then performing gas-oil-water three-phase separation, and the separated product gas is absorbed by lean circulating liquid containing C4 and C4+ to obtain hydrogen-methane mixed gas and rich circulating liquid that absorbs C2, C3, and C4, and C4, C4, C4+, and absorbed C3 and C4 components are separated from the rich circulating liquid; (3) The separated C4, C4+ and absorbed C3, C4 components are separated again to obtain light hydrocarbon components containing C2 and C3 and components containing C4 and C4+; the components containing C2 and C3 light hydrocarbons are separated to obtain a mixture of ethylene, ethane, and trace acetylene and a mixture of propylene and propane; the mixture of ethylene, ethane, and trace acetylene is converted into ethylene or green oil under the action of a hydrogenation catalyst; the ethylene or green oil is distilled to obtain an industrial-grade ethylene product and liquid ethane; the mixture of propylene and propane is separated to obtain industrial-grade propylene and liquid propane; the components containing C4 and C4+ are sent out as products or refluxed as lean circulating liquid to absorb the product gas separated from the three phases.

2. The stable absorption and separation process of methanol to olefins according to claim 1, characterized in that: The pressure of the methanol conversion gas after pressurization in step (1) is 0.05MpaG-0.08MpaG; preferably, the temperature of the methanol conversion gas before water washing in step (1) is 40°C; preferably, the sodium hydroxide solutions of different concentrations in step (1) are 1wt% sodium hydroxide solution, 4wt% sodium hydroxide solution, and 7wt% sodium hydroxide solution, respectively.

3. The stable absorption and separation process of methanol to olefins according to claim 1, characterized in that: The mixed gas rich in hydrogen, methane, ethylene and ethane separated from the rich circulating liquid in step (2) is cooled to obtain hydrogen and methane, and the obtained hydrogen and methane are mixed with the gas-liquid two-phase obtained by the conversion gas after deoxygenation and deacidification.

4. The stable absorption and separation process of methanol to olefins according to claim 1, characterized in that: In step (2), a mixed gas rich in hydrogen, methane, ethylene and ethane is separated from the rich circulating liquid, and the mixed gas is cooled to obtain a liquid phase containing C2 and C3. A part of the liquid phase is refluxed and absorbed again with a lean circulating liquid containing C4 and C4+ to obtain a hydrogen-methane mixed gas and a rich circulating liquid that has absorbed C2, C3 and C4. The other part is mixed with a product liquid separated from the three phases of gas, oil and water and then separated. The separated components containing C3, C4 and C4+ are mixed with the C4, C4+ and the absorbed C3 and C4 components separated from the rich circulating liquid in step (3). In step (3), a mixed gas rich in hydrogen, methane, ethylene and ethane is separated from the rich circulating liquid, and the non-condensable gas is cooled to obtain a mixture of the mixed gas and the product gas separated from the three phases of gas, oil and water.

5. The stable absorption and separation process of methanol to olefins according to any one of claims 1 to 4, characterized in that: The pressure of the converted gas before it becomes gas-liquid two-phase after deoxygenation and deacidification in step (2) is 3.0MpaG~3.4MpaG; preferably, the temperature at which the converted gas becomes gas-liquid two-phase after deoxygenation and deacidification in step (2) is 9°C~11°C; preferably, the operating temperature when the product gas in step (2) is absorbed by the lean circulating liquid containing C4 and C4+ is 5°C~10°C; preferably, the separation temperature of the rich circulating liquid in step (2) is 0.8MpaG~1.2MpaG.

6. A methanol to olefins stable absorption and separation device, characterized in that: The invention comprises a water washing tower (4), an alkali washing tower (6), a three-phase separator (9), an absorption tower (12), a regeneration tower (17), a depropanizer (26), and a deethanizer (28) which are connected in sequence. The top of the deethanizer (28) is connected to an ethylene product tower (30), and the bottom of the deethanizer (28) is connected to a propylene product tower (33). The water washing tower (4) is connected to a water washing liquid inlet pipe (5) and an air inlet pipe (1), and the upper part of the absorption tower (12) is connected to a lean circulating liquid delivery pipe (15).

7. The methanol to olefins stable absorption and separation device according to claim 6, characterized in that: Alkali liquid feed pipes capable of conveying alkali liquid of different concentrations are sequentially installed in the alkali washing tower (6) from top to bottom; preferably, a product gas dryer (10) is also installed between the three-phase separator (9) and the absorption tower (12); preferably, the top of the regeneration tower (17) is connected to a regeneration tower cryogenic cooler (18), the outlet of the regeneration tower cryogenic cooler (18) is connected to a regeneration tower reflux tank (19), the gas phase outlet of the regeneration tower reflux tank (19) is connected to the outlet of the product gas dryer (10), and the liquid phase outlet of the regeneration tower reflux tank (19) is connected to the outlet of the alkali washing tower (6).

8. The methanol to olefins stable absorption and separation device according to claim 6 or 7, characterized in that: The invention also comprises a stabilization tower (21), wherein the liquid phase outlet of the three-phase separator (9) is further connected to a product liquid dryer (11), the outlet of the product liquid dryer (11) and the liquid phase outlet of the regeneration tower reflux tank (19) are connected to the inlet of the stabilization tower (21) through a product liquid heater (25), and the bottom of the stabilization tower (21) is connected to the inlet of a depropanizer (26) through the product liquid heater (25); preferably, the top of the stabilization tower (21) is connected to A stabilization tower cooler (22), the outlet of the stabilization tower cooler (22) is connected to a stabilization tower reflux tank (23), the gas phase outlet of the stabilization tower reflux tank (23) is connected to the product gas inlet of the absorption tower (12), and the liquid phase outlet of the stabilization tower reflux tank (23) is connected to the upper part of the stabilization tower (21); preferably, a stabilization tower reboiler (24) is also installed at the lower part of the stabilization tower (21), and a regeneration tower reboiler (20) is also installed at the lower part of the regeneration tower (17).

9. The methanol to olefins stable absorption and separation device according to claim 6 or 7, characterized in that: A lean circulating liquid deep cooler (14) is installed on the lean circulating liquid delivery pipe (15), and a lean-rich liquid heat exchanger (16) is installed between the absorption tower (12) and the regeneration tower (17). A lean circulating liquid feed pipe connected to the lean circulating liquid deep cooler (14) is installed on the lean-rich liquid heat exchanger (16), and the bottom of the depropanizer (26) is connected to the lean circulating liquid feed pipe.

10. The methanol to olefins stable absorption and separation device according to claim 6 or 7, characterized in that: The gas pipe (1) is provided with a first conversion gas compressor (2) and a compressor inter-stage cooler (3); a second conversion gas compressor (7) and a conversion gas deep cooler (8) are provided between the alkali washing tower (6) and the three-phase separator 9; preferably, an acetylene hydrogenation reactor (29) is further provided between the depropanizer (26) and the ethylene product tower (30).

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