Gas purification and separation method and device

Abstract

The invention provides a gas purification and separation method and device, and belongs to the technical field of gas purification. The method comprises the following steps: mixing process gas and methanol, and sequentially carrying out condensation treatment and gas-liquid separation treatment to obtain gas-liquid separation process gas and acidic gas condensate; carrying out methanol washing on the gas-liquid separation process gas to realize desulfurization and decarbonization so as to obtain purified gas and rich methanol (including first sulfur-containing methanol and carbon-rich methanol); carrying out first flash separation treatment on the acidic gas condensate to respectively obtain acidic gas, second sulfur-containing methanol and solid carbon dioxide; washing the solid carbon dioxide with methanol, dissolving the solid carbon dioxide in methanol, and carrying out second flash separation treatment on the obtained methanol rich in carbon dioxide to respectively obtain gas carbon dioxide and cold methanol containing carbon dioxide; the carbon dioxide-containing cold methanol can be reused for dissolving the washed solid carbon dioxide after being heated; heat exchange is carried out between the second flash separation treatment and the condensation treatment. The method has a good process gas purification and separation effect, and has the advantages of energy conservation and consumption reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of gas purification, and in particular, to a gas purification and separation method and device. Background Art

[0002] Process gas generated in the coal chemical industry generally contains components such as hydrogen, carbon monoxide, carbon dioxide, and hydrogen sulfide. If it is to be effectively utilized, purification and separation must be carried out, especially acidic gases such as carbon dioxide and hydrogen sulfide need to be separated out.

[0003] There are endless gas purification technologies. The low-temperature methanol washing purification process has become the preferred technology for gas purification in the coal chemical industry due to its high purification degree. The traditional low-temperature methanol washing purification process usually uses lean methanol to absorb carbon dioxide in the process gas to obtain carbon-rich methanol. Part of the carbon-rich methanol is used to further absorb hydrogen sulfide in the process gas, thus completing the purification process of the process gas. The remaining carbon-rich methanol is also used to absorb hydrogen sulfide in the exhaust gas. However, in the traditional low-temperature methanol washing purification process, the amount of methanol used is relatively large, so the power consumption for transporting methanol and the cold loss caused by the power heat work conversion for transporting methanol are relatively large, resulting in a relatively high overall energy consumption of the process. Summary of the Invention

[0004] The purpose of the present invention is to provide a gas purification and separation method and device. The method provided by the present invention has a good purification and separation effect on process gas and uses less methanol, having the advantages of energy conservation and consumption reduction.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a gas purification and separation method, including the following steps:

[0007] Mix the process gas with methanol to obtain a mixture of the process gas and methanol;

[0008] Conduct condensation treatment on the mixture of the process gas and methanol to obtain condensed process gas, and the process gas contains carbon dioxide and hydrogen sulfide;

[0009] Conduct gas-liquid separation treatment on the condensed process gas to respectively obtain gas-liquid separated process gas and acidic gas condensate;

[0010] Subject the gas-liquid separated process gas to methanol washing for desulfurization treatment to respectively obtain desulfurized process gas and first sulfur-containing methanol; subject the desulfurized process gas to methanol washing for decarbonization treatment to respectively obtain purified gas and carbon-rich methanol, and part of the carbon-rich methanol is recycled for the desulfurization treatment;

[0011] Conduct first flash separation treatment on the acidic gas condensate to respectively obtain acidic gas, second sulfur-containing methanol, and solid carbon dioxide;

[0012] The solid carbon dioxide is washed with methanol, and the washed solid carbon dioxide is dissolved in methanol to obtain carbon dioxide-rich methanol; the carbon dioxide-rich methanol is subjected to a second flash separation treatment to obtain gaseous carbon dioxide and carbon dioxide-containing cold methanol respectively; the carbon dioxide-containing cold methanol is heated and then recycled to dissolve the washed solid carbon dioxide;

[0013] Heat exchange is carried out between the second flash separation treatment and the condensation treatment.

[0014] Further, the temperature of the condensed process gas is -57 to -56 °C.

[0015] Further, before the condensation treatment, it also includes: cooling the mixture of the process gas and methanol to -36 to -10 °C for the first time, and then cooling it to -40 to -36 °C for the second time; heat exchange is carried out between the first cooling and the heating.

[0016] Further, in the mixture of the process gas and methanol, the mass ratio of the process gas to methanol is based on the molar ratio of carbon dioxide to methanol in the acid gas condensate being 100:0.5 to 1.

[0017] Further, the pressure of the first flash separation treatment is 0.40 to 0.52 MPa, and the temperature is -57 to -56 °C.

[0018] Further, the pressure of the second flash separation treatment is 0.15 to 0.52 MPa.

[0019] Further, the temperature of the carbon dioxide-containing hot methanol is -36 to 40 °C.

[0020] The present invention provides a gas purification and separation device, including a condensation heat exchanger 3, a gas-liquid separator 4, a desulfurization tower 5, a decarbonization tower 6, a flash separator 7, a three-way pipe 8 and a dissolver 9;

[0021] The condensation heat exchanger 3 is provided with a first feed port and a second feed port, which are respectively used for feeding the mixture of the process gas and methanol and the carbon dioxide-rich feed; it is also provided with a first discharge port, a second discharge port and a third discharge port, which are respectively used for discharging the condensed process gas, the carbon dioxide-containing cold methanol and the gaseous carbon dioxide; the first discharge port is communicated with the gas-liquid separator 4;

[0022] The gas-liquid separator 4 is provided with a third feed port for feeding the condensed process gas; it is also provided with a fourth discharge port and a fifth discharge port, which are respectively used for discharging the gas-liquid separated process gas and the acid gas condensate; the fourth discharge port is communicated with the desulfurization tower 5, and the fifth discharge port is communicated with the flash separator 7;

[0023] The desulfurization tower 5 is provided with a fourth feed inlet and a fifth feed inlet, which are respectively used for feeding process gas for gas-liquid separation and feeding methanol; it is also provided with a sixth discharge outlet and a seventh discharge outlet, which are respectively used for discharging the first sulfur-containing methanol and discharging the desulfurized process gas; the seventh discharge outlet is communicated with the decarbonization tower 6;

[0024] The decarbonization tower 6 is provided with a sixth feed inlet and a seventh feed inlet, which are respectively used for feeding desulfurized gas and feeding methanol; it is also provided with an eighth discharge outlet and a ninth discharge outlet, which are respectively used for discharging purified gas and discharging rich-carbon methanol; the ninth discharge outlet is communicated with the fifth feed inlet;

[0025] The flash separator 7 is provided with an eighth feed inlet for feeding acid gas condensate; it is also provided with a tenth discharge outlet and an eleventh discharge outlet, which are respectively used for discharging acid gas and discharging the second sulfur-containing methanol; it is also provided with a first inlet / outlet for feeding washing liquid and discharging solid carbon dioxide; the first inlet / outlet is communicated with the three-way pipe 8;

[0026] The three-way pipe 8 is provided with a second inlet / outlet for feeding solid carbon dioxide and discharging washing liquid; it is also provided with a ninth feed inlet for feeding methanol; it is also provided with a twelfth discharge outlet for discharging washed solid carbon dioxide; the ninth feed inlet is communicated with the ninth discharge outlet, and the twelfth discharge outlet is communicated with the dissolver 9;

[0027] The dissolver 9 is provided with a tenth feed inlet and an eleventh feed inlet, which are respectively used for feeding washed solid carbon dioxide and feeding methanol; it is also provided with a thirteenth discharge outlet for discharging carbon dioxide-rich material; the thirteenth discharge outlet is communicated with the second feed inlet.

[0028] Preferably, the gas purification and separation device further includes a first heat exchanger 1, a second heat exchanger 2 and a transfer pump 10;

[0029] The first heat exchanger 1 is provided with a twelfth feed inlet and a thirteenth feed inlet, which are respectively used for feeding a mixture of process gas and methanol and feeding cold methanol containing carbon dioxide; it is also provided with a fourteenth discharge outlet and a fifteenth discharge outlet, which are respectively used for discharging the mixture of process gas and methanol and discharging hot methanol containing carbon dioxide; the fourteenth discharge outlet is communicated with the first feed inlet via the second heat exchanger 2, the thirteenth feed inlet is communicated with the second discharge outlet via the transfer pump 10, and the fifteenth discharge outlet is communicated with the eleventh feed inlet.

[0030] Preferably, a condensation heat exchanger pressure control valve 31 is provided at the third discharge outlet, and a condensation heat exchanger liquid level control valve 32 is provided between the first heat exchanger 1 and the dissolver 9;

[0031] A gas-liquid separator liquid level control valve 41 is provided between the gas-liquid separator 4 and the flash separator 7;

[0032] A desulfurization tower liquid level control valve 51 is arranged at the sixth discharge port, and a desulfurization tower flow control valve 52 is arranged between the fifth feed port and the ninth discharge port;

[0033] A lean methanol flow control valve 61 is arranged at the seventh feed port, the ninth discharge port is communicated with a rich carbon methanol discharge pipeline, a decarbonization tower liquid level control valve 62 is arranged on the rich carbon methanol discharge pipeline, and the desulfurization tower flow control valve 52 is located between the ninth discharge port and the decarbonization tower liquid level control valve 62;

[0034] A flash separator pressure control valve 71 is arranged at the tenth discharge port, and a flash separator liquid level control valve 72 is arranged at the eleventh discharge port;

[0035] A three-way pipe flow control valve 81 is arranged between the ninth feed port and the ninth discharge port, and the three-way pipe flow control valve 81 is located between the desulfurization tower flow control valve 52 and the decarbonization tower liquid level control valve 62;

[0036] A dissolver flow control valve 91 is arranged between the thirteenth discharge port and the second feed port.

[0037] Beneficial effects: In the present invention, the process gas is mixed with methanol and then subjected to condensation treatment, which can condense acidic gases such as carbon dioxide and hydrogen sulfide in the process gas. Methanol can dissolve the solid carbon dioxide generated when the process gas is cooled, prevent the formation of carbon dioxide hydrate solids, and prevent blockage of equipment pipelines; after the condensation treatment, the obtained condensed process gas is subjected to gas-liquid separation treatment to respectively obtain a gas-liquid separation process gas and an acidic gas condensate. The acidic gas condensate is a condensate containing methanol, carbon dioxide, and hydrogen sulfide; the gas-liquid separation process gas is successively subjected to desulfurization treatment and decarbonization treatment to obtain a purified gas that meets the requirements of downstream production processes, and at the same time, rich carbon methanol will also be obtained; the acidic gas condensate is subjected to a first flash separation treatment to respectively obtain an acidic gas (specifically a mixed gas containing carbon dioxide and hydrogen sulfide), a second sulfur-containing methanol (specifically a mixed liquid containing methanol, carbon dioxide, and hydrogen sulfide), and solid carbon dioxide. The solid carbon dioxide is purified by methanol washing, and the washed solid carbon dioxide is dissolved in methanol (specifically, hot methanol containing carbon dioxide) to obtain carbon dioxide-rich methanol. The carbon dioxide-rich methanol is subjected to a second flash separation treatment to respectively obtain gaseous carbon dioxide and carbon dioxide-containing cold methanol, thereby realizing the separation of gaseous carbon dioxide; then the carbon dioxide-containing cold methanol is heated and reused to dissolve the washed solid carbon dioxide.

[0038] The method of the present invention can achieve efficient separation of acid gas, especially carbon dioxide, in process gas, and the cooling capacity during the condensation process of process gas can be recycled during the gasification process of solid carbon dioxide, which is beneficial to cost reduction. At the same time, since the acid gas in the process gas is separated by condensation, the amount of methanol required for absorption and purification is reduced, thus achieving the effect of energy conservation and consumption reduction. After the process gas is condensed and separated to remove the acid gas, the present invention then performs purification by low-temperature methanol washing (i.e., desulfurization treatment and decarbonization treatment), which has a good purification effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic structural diagram of the gas purification and separation device in the embodiment of the present invention;

[0040] Among them, 1 is the first heat exchanger, 2 is the second heat exchanger, 3 is the condensation heat exchanger, 4 is the gas-liquid separator, 5 is the desulfurization tower, 6 is the decarbonization tower, 7 is the flash separator, 8 is the three-way pipe, 9 is the dissolver, and 10 is the transfer pump;

[0041] 31 is the pressure control valve of the condensation heat exchanger, 32 is the liquid level control valve of the condensation heat exchanger, 41 is the liquid level control valve of the gas-liquid separator, 51 is the liquid level control valve of the desulfurization tower, 52 is the flow control valve of the desulfurization tower, 61 is the lean methanol flow control valve, 62 is the liquid level control valve of the decarbonization tower, 71 is the pressure control valve of the flash separator, 72 is the liquid level control valve of the flash separator, 81 is the flow control valve of the three-way pipe, and 91 is the flow control valve of the dissolver;

[0042] 101 is the process gas, 102 is the methanol, 103 is the mixture of the process gas and methanol, 104 is the condensed process gas, 105 is the gas-liquid separated process gas, 106 is the desulfurized process gas, 107 is the purified gas; 201 is the lean methanol, 202 is the carbon-rich methanol, 203 is the first sulfur-containing methanol; 301 is the acid gas condensate, 302 is the acid gas, 303 is the second sulfur-containing methanol, 304 is the solid carbon dioxide, 305 is the washed solid carbon dioxide, 306 is the carbon dioxide-rich methanol, 307 is the gaseous carbon dioxide, 308 is the carbon dioxide-containing cold methanol, and 309 is the carbon dioxide-containing hot methanol. DETAILED DESCRIPTION OF THE INVENTION

[0043] The present invention provides a gas purification and separation method, including the following steps:

[0044] Mix the process gas with methanol to obtain a mixture of the process gas and methanol;

[0045] Perform condensation treatment on the mixture of the process gas and methanol to obtain the condensed process gas, and the process gas contains carbon dioxide and hydrogen sulfide;

[0046] Perform gas-liquid separation treatment on the condensed process gas to respectively obtain the gas-liquid separated process gas and the acid gas condensate;

[0047] The gas-liquid separation process gas is subjected to methanol wash for desulfurization treatment to obtain desulfurized process gas and first sulfur-containing methanol respectively; the desulfurized process gas is subjected to methanol wash for decarbonization treatment to obtain purified gas and rich carbon methanol respectively, and part of the rich carbon methanol is recycled for the desulfurization treatment;

[0048] The acid gas condensate is subjected to first flash separation treatment to obtain acid gas, second sulfur-containing methanol and solid carbon dioxide respectively;

[0049] The solid carbon dioxide is washed with methanol, and the washed solid carbon dioxide is dissolved in methanol to obtain carbon dioxide-rich methanol; the carbon dioxide-rich methanol is subjected to second flash separation treatment to obtain gaseous carbon dioxide and carbon dioxide-containing cold methanol respectively; the carbon dioxide-containing cold methanol is heated and recycled for dissolving the washed solid carbon dioxide;

[0050] Heat exchange is carried out between the second flash separation treatment and the condensation treatment.

[0051] The traditional low-temperature methanol wash purification process has relatively high energy consumption. The inventor's research found that the high energy consumption in the traditional low-temperature methanol wash purification process is affected by various factors. Among them, the power consumption for transporting methanol and the loss of cold energy in the conversion of the power consumed for transporting methanol account for a relatively large proportion, about 50-85% of the energy consumption in the entire purification process. Reducing the amount of methanol used in the low-temperature methanol wash purification process can save energy and reduce consumption. Therefore, reducing the content of acidic gases such as carbon dioxide and hydrogen sulfide in the gas during the coal chemical process can reduce the amount of methanol used for purification absorption, thereby saving energy and reducing consumption. To solve the problem of high energy consumption in gas separation and purification, especially in the low-temperature methanol wash purification process, the present invention provides a gas purification and separation method. Specifically, it combines the condensation and separation of some acidic gases in the process gas with the separation of carbon dioxide from the acidic gas condensate, which can reduce the content of acidic gases in the process gas and the tail gas emissions, thereby reducing the amount of methanol used in the low-temperature methanol wash purification process and further reducing the energy consumption in the process gas purification process. The relevant principles involved in the gas purification and separation method of the present invention are as follows: The critical point temperature and pressure of carbon dioxide are 30.9782°C and 7.3773 MPa respectively, and the triple point temperature and pressure are -56.558°C and 0.51792 MPa respectively. That is, gaseous carbon dioxide can be liquefied in the temperature range of -56.558-30.9782°C and can only be solidified below the temperature of -56.558°C. Methanol has a lower freezing point than carbon dioxide and has a certain solubility for solid carbon dioxide. Liquid carbon dioxide has a certain absorption solubility for hydrogen sulfide and carbonyl sulfide gases. The present invention pre-condenses and separates the process gas that needs to be treated by low-temperature methanol wash, condensing and separating some acidic gases such as carbon dioxide and hydrogen sulfide. The lower the condensation temperature, the less the remaining acidic gases such as carbon dioxide and hydrogen sulfide, and the less the amount of methanol required for low-temperature methanol wash purification, which is more conducive to saving energy and reducing consumption. Carbon dioxide solids will be produced near the triple point temperature of carbon dioxide. The process gas contains trace amounts of water, which will form solid carbon dioxide hydrate with carbon dioxide under high-pressure and low-temperature conditions. The present invention mixes a certain amount of methanol in the process gas to prevent the blockage of carbon dioxide solidification during the low-temperature condensation of the process gas and can also prevent the blockage of solid carbon dioxide hydrate, thereby ensuring the continuous progress of production. The method of the present invention will be described in detail below.

[0052] In the present invention, unless otherwise specified, the raw materials used are commercially available products well-known to those skilled in the art or are prepared by methods well-known to those skilled in the art.

[0053] The present invention condenses a mixture of process gas and methanol to obtain a condensed process gas, and the process gas contains carbon dioxide and hydrogen sulfide. As an embodiment of the present invention, specifically, the process gas is mixed with methanol to obtain a mixture of the process gas and methanol. The present invention places no special limitation on the source of the process gas, and any process gas well-known to those skilled in the art can be used. The process gas of the present invention contains carbon dioxide and hydrogen sulfide, and specifically can be a mixed gas of hydrogen, carbon monoxide, methane, carbon dioxide, hydrogen sulfide, and carbonyl sulfide. As an embodiment of the present invention, the pressure of the process gas can be 3.0 - 8.0 MPa, the molar content of carbon dioxide can be 25 - 45%, and the molar contents of hydrogen sulfide and carbonyl sulfide can independently be 0.05 - 2%. In the embodiment of the present invention, the flow rate of the process gas is specifically 10060 kmol / h, the pressure is specifically 5.6 MPa, and the temperature is specifically -12°C; the process gas specifically includes 4376 kmol / h of carbon dioxide, 20 kmol / h of hydrogen sulfide, and 0.042 kmol / h of carbonyl sulfide.

[0054] As an embodiment of the present invention, in the mixture of the process gas and methanol, the mass ratio of the process gas to methanol is based on the molar ratio of carbon dioxide to methanol in the acid gas condensate being 100:0.5 - 1. In the present invention, a certain amount of methanol is incorporated into the process gas to prevent the clogging caused by the solidification of carbon dioxide and to prevent the clogging caused by the solidification of carbon dioxide hydrate. The more methanol is incorporated, the less likely it is to clog, but it is not conducive to the subsequent separation of solid carbon dioxide. Therefore, the amount of methanol incorporated is selected as the minimum amount that does not cause clogging, and the molar content of methanol in the acid gas condensate is preferably 0.5 - 1%.

[0055] After obtaining the mixture of the process gas and methanol, the present invention condenses the mixture of the process gas and methanol to obtain a condensed process gas. As an embodiment of the present invention, before the condensation treatment, it further includes: cooling the mixture of the process gas and methanol to -36 to -10°C through a first cooling, and then cooling it to -40 to -36°C through a second cooling; the first cooling exchanges heat with the heating involved in the subsequent processes, which will be described in detail later; the second cooling is achieved by introducing an external refrigerant. As an embodiment of the present invention, the temperature of the condensed process gas can be -57 to -56°C, and specifically can be -56.5°C. The present invention specifically cools and condenses the process gas to a temperature lower than the condensation temperature of the acid gas in the process gas, preferably close to the carbon dioxide triple point temperature (-56.558°C). As an embodiment of the present invention, external cooling can be supplemented as needed during the condensation treatment for the heat balance of the condensation treatment process.

[0056] After obtaining the condensed process gas, the present invention performs gas-liquid separation on the condensed process gas to separately obtain a gas-liquid separation process gas and an acid gas condensate. The present invention has no special limitation on the conditions of the gas-liquid separation treatment, and the conditions well-known to those skilled in the art can be adopted. In the embodiments of the present invention, the flow rate of the gas-liquid separation process gas is specifically 6508.84 kmol / h; the gas-liquid separation process gas specifically includes 884.9 kmol / h of carbon dioxide, 3.818 kmol / h of hydrogen sulfide, and 0.00154 kmol / h of carbonyl sulfide. As an implementation manner of the present invention, the flow rate of the acid gas condensate is specifically 3571.16 kmol / h; the acid gas condensate specifically includes 3482.1 kmol / h of carbon dioxide, 16.182 kmol / h of hydrogen sulfide, and 0.04046 kmol / h of carbonyl sulfide. The treatment methods of the gas-liquid separation process gas and the acid gas condensate are described in detail below.

[0057] After obtaining the gas-liquid separation process gas, the present invention performs desulfurization treatment on the gas-liquid separation process gas by methanol washing to separately obtain a desulfurized process gas and a first sulfur-containing methanol; the desulfurized process gas is subjected to methanol washing for decarbonization treatment to separately obtain a purified gas and a carbon-rich methanol, and a part of the carbon-rich methanol is recycled for the desulfurization treatment. The present invention has no special limitation on the conditions of the desulfurization treatment, and the conditions well-known to those skilled in the art can be adopted; the present invention removes hydrogen sulfide in the gas-liquid separation process gas through the desulfurization treatment. The present invention separately obtains a desulfurized process gas and a first sulfur-containing methanol through the desulfurization treatment, and the first sulfur-containing methanol is sent to a downstream regeneration treatment process. The present invention has no special limitation on the conditions of the decarbonization treatment, and the conditions well-known to those skilled in the art can be adopted; the present invention removes carbon dioxide in the desulfurized process gas through the decarbonization treatment to obtain a purified gas. The methanol used in the decarbonization treatment of the present invention can specifically be lean methanol, and the lean methanol can specifically be a commercially available product well-known to those skilled in the art; in the embodiments of the present invention, the temperature of the lean methanol is specifically -56°C, and the flow rate is specifically 225000 kg / h. The present invention separately obtains a purified gas and a carbon-rich methanol through the decarbonization treatment; in the embodiments of the present invention, the flow rate of the purified gas is specifically 5554 kmol / h, the carbon dioxide content is less than 1 ppm, and the purified gas is sent to a downstream production process; the carbon-rich methanol does not contain sulfur, and can specifically be divided into three parts. The first part of the carbon-rich methanol is recycled for the desulfurization treatment, the second part of the carbon-rich methanol can be used for washing the solid carbon dioxide obtained in the subsequent process, which will be described in detail later, and the remaining carbon-rich methanol can be sent to a downstream regeneration treatment process.

[0058] After obtaining the acidic condensate, the present invention performs a first flash separation treatment on the acidic condensate to obtain acidic gas, second sulfur-containing methanol, and solid carbon dioxide respectively. As an embodiment of the present invention, the temperature is controlled by the flash pressure during the first flash separation treatment; the pressure of the first flash separation treatment is 0.40 - 0.52 MPa, and the corresponding flash temperature at this time is -57 - -56 °C, which is near the triple point temperature of carbon dioxide -56.558 °C. In the embodiments of the present invention, specifically, the pressure of the first flash separation treatment of the acidic condensate is controlled below the triple point pressure of carbon dioxide 0.51795 MPa, so as to control the temperature of the first flash separation treatment near the triple point temperature of carbon dioxide -56.558 °C, and finally obtain acidic gas, second sulfur-containing methanol, and solid carbon dioxide. In the present invention, the acidic condensate (a mixed liquid of carbon dioxide and methanol) can output a low-temperature cold source during the low-pressure flash (i.e., the first flash separation treatment), thereby providing a low-temperature cold source for the condensation treatment of the mixture of process gas and methanol. When the high-pressure and low-temperature mixed liquid of carbon dioxide, hydrogen sulfide, and carbonyl sulfide is depressurized, only gas and solid two-phase substances are obtained when the pressure is reduced below 0.51795 MPa. All hydrogen sulfide, all carbonyl sulfide, and part of carbon dioxide in the liquid flash into a gas mixture, and part of carbon dioxide forms solid carbon dioxide, and the ratio of gaseous carbon dioxide to solid carbon dioxide is about 0.361:0.639. The density of solid carbon dioxide is greater than that of liquid carbon dioxide, and greater than the mixed liquid of methanol and carbon dioxide, that is, solid carbon dioxide can settle by gravity in liquid carbon dioxide and also in the mixed liquid of methanol and carbon dioxide. In the embodiments of the present invention, the flow rate of the acidic gas is specifically 1503.56 kmol / h; the acidic gas specifically includes 1236.44 kmol / h of carbon dioxide, 15.166 kmol / h of hydrogen sulfide, and 0.0331 kmol / h of carbonyl sulfide; the acidic gas is sent to the downstream regeneration treatment process. In the embodiments of the present invention, the flow rate of the second sulfur-containing methanol is specifically 72.873 kmol / h; the second sulfur-containing methanol specifically includes 51.973 kmol / h of carbon dioxide, 10163 kmol / h of hydrogen sulfide, and 0.00737 kmol / h of carbonyl sulfide; the second sulfur-containing methanol is sent to the downstream regeneration treatment process. In the embodiments of the present invention, the flow rate of the solid carbon dioxide can specifically be 2193.72 kmol / h (i.e., 96545 kg / h). In the present invention, the densities of the second sulfur-containing methanol and solid carbon dioxide are different. As described in the embodiments, the density of the second sulfur-containing methanol is 1112.95 kg / m 3 , and the density of the solid carbon dioxide is 15125 kg / m 3 , and the two can be separated by gravity sedimentation.

[0059] After obtaining solid carbon dioxide, the present invention uses methanol to wash the solid carbon dioxide, dissolves the washed solid carbon dioxide in methanol to obtain carbon dioxide-rich methanol; performs a second flash separation treatment on the carbon dioxide-rich methanol to separately obtain gaseous carbon dioxide and carbon dioxide-containing cold methanol; heats the carbon dioxide-containing cold methanol and recycles it to dissolve the washed solid carbon dioxide; the second flash separation treatment exchanges heat with the condensation treatment. As an embodiment of the present invention, the washing method can be rinsing, specifically, it can be rinsed based on the gravity sedimentation process of solid carbon dioxide and the reverse flow of methanol to obtain the washed solid carbon dioxide. As an embodiment of the present invention, the methanol used for washing the solid carbon dioxide is sulfur-free methanol. For example, part of the carbon-rich methanol can be used to wash the solid carbon dioxide; the carbon-rich methanol in the present invention does not contain sulfur, and hydrogen sulfide in the solid carbon dioxide can be removed through washing. As an embodiment of the present invention, the pressure of the second flash separation treatment can be 0.10 - 0.52 MPa, specifically 0.18 MPa. As an embodiment of the present invention, gaseous carbon dioxide is obtained through the second flash separation treatment, and the gaseous carbon dioxide is sent to the downstream treatment process. As an embodiment of the present invention, the heating exchanges heat with the first temperature reduction; the temperature of the carbon dioxide-containing hot methanol obtained after heating can be -36 to 40 °C, specifically -16 °C. The present invention performs a second flash separation treatment on the carbon dioxide-rich methanol obtained after dissolving solid carbon dioxide, which is beneficial to the recycling of cold energy during the recycling process and maintaining the heat balance of the process.

[0060] The present invention provides a gas purification and separation device, including a condensation heat exchanger 3, a gas-liquid separator 4, a desulfurization tower 5, a decarbonization tower 6, a flash separator 7, a three-way pipe 8, and a dissolver 9. Each component will be described in detail below.

[0061] The condensation heat exchanger 3 of the present invention is provided with a first feed port and a second feed port, which are respectively used for feeding a mixture of process gas and methanol and carbon dioxide-rich feed; it is also provided with a first discharge port, a second discharge port, and a third discharge port, which are respectively used for discharging condensed process gas, carbon dioxide-containing cold methanol, and gaseous carbon dioxide; the first discharge port is communicated with the gas-liquid separator 4. The condensation heat exchanger 3 of the present invention is used for condensation treatment and the second flash separation treatment. Specifically, the mixture of process gas and methanol is subjected to condensation treatment to obtain condensed process gas, and at the same time, the carbon dioxide-rich methanol is subjected to the second flash separation treatment to separately obtain gaseous carbon dioxide and carbon dioxide-containing cold methanol.

[0062] The gas-liquid separator 4 of the present invention is provided with a third feed port for feeding the condensed process gas; and also provided with a fourth discharge port and a fifth discharge port for discharging the gas-liquid separated process gas and the acidic gas condensate respectively; the fourth discharge port is communicated with the desulfurization tower 5, and the fifth discharge port is communicated with the flash separator 7. The gas-liquid separator 4 of the present invention is used for gas-liquid separation treatment, specifically separating the condensed process gas through gas-liquid separation treatment to obtain the gas-liquid separated process gas and the acidic gas condensate respectively.

[0063] The desulfurization tower 5 of the present invention is provided with a fourth feed port and a fifth feed port for feeding the gas-liquid separated process gas and methanol respectively; and also provided with a sixth discharge port and a seventh discharge port for discharging the first sulfur-containing methanol and the desulfurized process gas respectively; the seventh discharge port is communicated with the decarbonization tower 6. The desulfurization tower 5 of the present invention is used for desulfurization treatment, specifically desulfurizing the gas-liquid separated process gas to obtain the desulfurized process gas. As an embodiment of the present invention, the fourth feed port is located at the lower part of the side wall of the desulfurization tower 5, the fifth feed port is located at the upper part of the side wall of the desulfurization tower 5, the sixth discharge port is located at the bottom of the desulfurization tower 5, and the seventh discharge port is located at the top of the desulfurization tower 5.

[0064] The decarbonization tower 6 of the present invention is provided with a sixth feed port and a seventh feed port for feeding the desulfurized gas and methanol respectively; and also provided with an eighth discharge port and a ninth discharge port for discharging the purified gas and the rich carbon methanol respectively; the ninth discharge port is communicated with the fifth feed port. The decarbonization tower 6 of the present invention is used for decarbonization treatment, specifically decarbonizing the desulfurized process gas to obtain the purified gas. As an embodiment of the present invention, the sixth feed port is located at the lower part of the side wall of the decarbonization tower 6, the seventh feed port is located at the upper part of the side wall of the decarbonization tower 6, the eighth discharge port is located at the top of the decarbonization tower 6, and the ninth discharge port is located at the bottom of the decarbonization tower 6.

[0065] The flash separator 7 of the present invention is provided with an eighth feed port for feeding acid gas condensate; it is also provided with a tenth discharge port and an eleventh discharge port for discharging acid gas and second sulfur-containing methanol respectively; it is also provided with a first feed and discharge port for feeding washing liquid and discharging solid carbon dioxide; the first feed and discharge port is communicated with a three-way pipe 8. The flash separator 7 of the present invention is used for performing a first flash separation treatment, specifically for performing a first flash separation treatment on acid gas condensate to obtain acid gas, second sulfur-containing methanol and solid carbon dioxide respectively. As an implementation manner of the present invention, the eighth feed port and the eleventh discharge port are located in the middle of the side wall of the flash separator 7, and the eighth feed port is lower than the eleventh discharge port, the tenth discharge port is located at the top of the flash separator 7, the first feed and discharge port is located at the bottom of the flash separator 7, and the bottom of the flash separator 7 is conical to facilitate the discharge of solid carbon dioxide; at the same time, the washing liquid after washing the solid carbon dioxide can enter the flash separator 7 through the first feed and discharge port.

[0066] The three-way pipe 8 of the present invention is provided with a second feed and discharge port for feeding solid carbon dioxide and discharging washing liquid; it is also provided with a ninth feed port for feeding methanol; it is also provided with a twelfth discharge port for discharging the washing liquid of solid carbon dioxide; the ninth feed port is communicated with the ninth discharge port, and the twelfth discharge port is communicated with a dissolver 9. The three-way pipe 8 of the present invention is used for washing solid carbon dioxide, and specifically, rich carbon methanol can be used to wash the solid carbon dioxide. As an implementation manner of the present invention, the second feed and discharge port is located at the top of the three-way pipe 8, the ninth feed port is located in the middle of the side wall of the three-way pipe 8, and the twelfth discharge port is located at the bottom of the three-way pipe 8. In the present invention, the solid carbon dioxide descends in the three-way pipe 8 based on the gravity sedimentation effect, and the rich carbon methanol without hydrogen sulfide introduced in the three-way pipe 8 prevents the downward movement of hydrogen sulfide during the upward movement, and the two meet to achieve the purification of the solid carbon dioxide. The washed solid carbon dioxide gravitates to the dissolver 9, and the washed washing liquid can enter the flash separator 7 through the second feed and discharge port. The present invention controls the feeding amount of the rich carbon methanol through the three-way pipe 8, so as to fully remove the hydrogen sulfide entrained in the solid carbon dioxide.

[0067] The dissolver 9 of the present invention is provided with a tenth feed port and an eleventh feed port, which are respectively used for feeding washed solid carbon dioxide and feeding methanol; it is also provided with a thirteenth discharge port for discharging carbon dioxide-rich material; the thirteenth discharge port is communicated with the second feed port. The dissolver 9 of the present invention is used for dissolving the washed solid carbon dioxide. As an embodiment of the present invention, the tenth feed port is located at the top of the dissolver 9, the eleventh feed port is located in the middle of the side wall of the dissolver 9, and the thirteenth discharge port is located at the bottom of the dissolver 9. In the present invention, methanol is introduced into the dissolver 9 to dissolve solid carbon dioxide to obtain carbon dioxide-rich methanol, and the carbon dioxide-rich methanol enters the condensation heat exchanger 3 for the second flash separation treatment to obtain gaseous carbon dioxide and methanol with low carbon dioxide content (i.e., cold methanol containing carbon dioxide), and the cold methanol containing carbon dioxide is heated and then continues to dissolve solid carbon dioxide for recycling.

[0068] As an embodiment of the present invention, the gas purification and separation device further includes a first heat exchanger 1, a second heat exchanger 2 and a transfer pump 10; the first heat exchanger 1 is provided with a twelfth feed port and a thirteenth feed port, which are respectively used for feeding a mixture of process gas and methanol and feeding cold methanol containing carbon dioxide; it is also provided with a fourteenth discharge port and a fifteenth discharge port, which are respectively used for discharging the mixture of process gas and methanol and discharging hot methanol containing carbon dioxide; the fourteenth discharge port is communicated with the first feed port through the second heat exchanger 2, the thirteenth feed port is communicated with the second discharge port through the transfer pump 10, and the fifteenth discharge port is communicated with the eleventh feed port.

[0069] The present invention controls the flash pressure on the flash side of the condensation heat exchanger 3 and simultaneously controls the cooling capacity of the second heat exchanger 2, so as to control the temperature of the process gas condensation at about -56.558°C, the triple point of carbon dioxide; by controlling the amount of methanol admixed in the process gas, it is ensured that no carbon dioxide solidification blockage occurs during the process gas condensation.

[0070] In the present invention, the gas purification and separation device further includes pipelines connecting various components and process control valves. The following will detail each of the process control valves involved.

[0071] As an embodiment of the present invention, a condensation heat exchanger pressure control valve 31 is provided at the third discharge port, and a condensation heat exchanger liquid level control valve 32 is provided between the first heat exchanger 1 and the dissolver 9. The present invention controls the carbon dioxide flash pressure in the condensation heat exchanger 3 through the condensation heat exchanger pressure control valve 31, so as to control the temperature of the process gas condensation close to -56.558°C.

[0072] As an embodiment of the present invention, a gas-liquid separator liquid level control valve 41 is provided between the gas-liquid separator 4 and the flash separator 7. The present invention controls the entry of acid gas condensate into the flash separator 7 through the gas-liquid separator liquid level control valve 41 for the first flash separation treatment.

[0073] As an embodiment of the present invention, a desulfurization tower liquid level control valve 51 is provided at the sixth discharge port, and a desulfurization tower flow control valve 52 is provided between the fifth feed port and the ninth discharge port. The present invention controls the flow rate of the rich carbon methanol used in the desulfurization treatment through the desulfurization tower flow control valve 52, thereby minimizing the hydrogen sulfide content in the obtained desulfurized process gas.

[0074] As an embodiment of the present invention, a lean methanol flow control valve 61 is provided at the seventh feed port, the ninth discharge port is connected to a rich carbon methanol discharge pipeline, a decarbonization tower liquid level control valve 62 is provided on the rich carbon methanol discharge pipeline, and the desulfurization tower flow control valve 52 is located between the ninth discharge port and the decarbonization tower liquid level control valve 62. The present invention controls the lean methanol flow rate through the lean methanol flow control valve 61, thereby controlling the carbon dioxide content in the purified gas.

[0075] As an embodiment of the present invention, a flash separator pressure control valve 71 is provided at the tenth discharge port, and a flash separator liquid level control valve 72 is provided at the eleventh discharge port. The present invention controls the flash pressure and temperature of the flash separator 7 through the flash separator pressure control valve 71, thereby controlling the content of solid carbon dioxide. During the first flash separation process, part of the carbon dioxide gasifies while part of the carbon dioxide solidifies to form solid carbon dioxide, obtaining a mixed gas containing carbon dioxide and hydrogen sulfide, i.e., acid gas, and also obtaining a mixed liquid containing carbon dioxide, hydrogen sulfide, and methanol, i.e., the second sulfur-containing methanol, and at the same time obtaining solid carbon dioxide.

[0076] As an embodiment of the present invention, a three-way pipe flow control valve 81 is provided between the ninth feed port and the ninth discharge port, and the three-way pipe flow control valve 81 is located between the desulfurization tower flow control valve 52 and the decarbonization tower liquid level control valve 62. The present invention controls the flow rate of the rich carbon methanol used to dissolve solid carbon dioxide through the three-way pipe flow control valve 81, thereby minimizing the hydrogen sulfide content in the subsequent dissolver 9.

[0077] As an embodiment of the present invention, a dissolver flow control valve 91 is provided between the thirteenth discharge port and the second feed port. The present invention controls the flow rate of the carbon dioxide-rich methanol through the dissolver flow control valve 91, thereby controlling the complete dissolution of the solid carbon dioxide in the dissolver 9.

[0078] Figure 1This is a schematic structural diagram of the gas purification and separation device in the embodiments of the present invention. Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0079] Embodiment 1

[0080] As Figure 1 shown, in this embodiment, the process gas of a coal gasification process with an annual output of 500,000 tons of synthetic ammonia is taken as an example for purification treatment. The index parameters of the process gas include: a flow rate of 10060 kmol / h, a pressure of 5.6 MPa, a temperature of -12 °C, containing 4376 kmol / h of carbon dioxide (CO 2 ), 20 kmol / h of hydrogen sulfide (H 2 S), and 0.042 kmol / h of carbonyl sulfide (COS); the specific purification treatment steps are as follows:

[0081] Mix the process gas 101 with methanol 102 with a flow rate of 20 kmol / h. Cool the mixture of the process gas and methanol 103 through the first heat exchanger 1, then pre-cool it through the second heat exchanger 2, and then condense it through the condensation heat exchanger 3 to reduce the temperature to -56.5 °C to obtain the condensed process gas 104; wherein the temperature of the condensed process gas 104 obtained at the outlet of the condensation heat exchanger 3 is controlled to be close to -55.558 °C by the cooling capacity of the second heat exchanger 2 and the pressure on the shell side of the condensation heat exchanger 3;

[0082] The condensed process gas 104 is subjected to gas-liquid separation through the gas-liquid separator 4. The gas-liquid separated process gas 105 is output from the top of the gas-liquid separator 4, and the acidic gas condensate 301 is output from the bottom; the flow rate of the gas-liquid separated process gas 105 is 6508.84 kmol / h, containing 884.9 kmol / h of carbon dioxide, 3.818 kmol / h of hydrogen sulfide, and 0.00154 kmol / h of carbonyl sulfide; the flow rate of the acidic gas condensate 301 is 3571.16 kmol / h, containing 3482.1 kmol / h of carbon dioxide, 16.182 kmol / h of hydrogen sulfide, and 0.04046 kmol / h of carbonyl sulfide;

[0083] The gas-liquid separation process gas 105 is desulfurized in the desulfurization tower 5, and then the obtained desulfurized process gas 106 is decarbonized in the decarbonization tower 6. The purified gas 107 is output from the top of the decarbonization tower 6, and the carbon-rich methanol 202 is output from the bottom; the flow rate of the purified gas 107 is 5554 kmol / h, and the carbon dioxide content is less than 1 ppm. The purified gas 107 is sent to the downstream production process; during the decarbonization process, lean methanol 201 is introduced into the decarbonization tower 6 through the lean methanol flow control valve 61. The temperature of the lean methanol 201 is -56°C and the flow rate is 225000 kg / h; the carbon-rich methanol 202 does not contain sulfur and is divided into three parts. The first part of the carbon-rich methanol 202 is transported to the desulfurization tower 5 through the desulfurization tower flow control valve 52 to participate in desulfurization. The second part of the carbon-rich methanol 202 is transported to the three-way pipe 8 through the three-way pipe flow control valve 81. The remaining carbon-rich methanol 202 is transported to the downstream regeneration treatment process through the decarbonization tower liquid level control valve 62; during the desulfurization process, the first sulfur-containing methanol 203 is output from the bottom of the desulfurization tower 5, and the first sulfur-containing methanol 203 is transported to the downstream regeneration treatment process through the desulfurization tower liquid level control valve 51;

[0084] The acidic gas condensate 301 is transported to the flash separator 7 through the gas-liquid separator liquid level control valve 41. The pressure in the flash separator 7 is controlled by the flash separator pressure control valve 71. Flash separation is carried out under the conditions of a pressure of 0.51 MPa and a temperature of -57°C to obtain acidic gas 302, the second sulfur-containing methanol 303 and solid carbon dioxide respectively; the flow rate of the acidic gas 302 is 1503.56 kmol / h, containing 1236.44 kmol / h of carbon dioxide, 15.166 kmol / h of hydrogen sulfide and 0.0331 kmol / h of carbonyl sulfide. The acidic gas 302 is transported to the downstream regeneration treatment process through the flash separator pressure control valve 71; the flow rate of the second sulfur-containing methanol 303 is 72.873 kmol / h, containing 51.973 kmol / h of carbon dioxide, 10163 kmol / h of hydrogen sulfide and 0.00737 kmol / h of carbonyl sulfide. The second sulfur-containing methanol 303 is transported to the downstream regeneration treatment process through the flash separator liquid level control valve 72; the flow rate of the solid carbon dioxide is 2193.72 kmol / h (i.e., 96545 kg / h); among them, the density of the second sulfur-containing methanol 303 is 1112.95 kg / m 3 , and the density of the solid carbon dioxide 304 is 15125 kg / m 3 , and the solid carbon dioxide 304 is separated from the second sulfur-containing methanol 303 by gravity sedimentation;

[0085] The solid carbon dioxide 304 descends to the three-way pipe 8, and is flushed by the upward flow of the second part of the carbon-rich methanol 202 in the three-way pipe 8. The washing liquid after flushing ascends to the flash separator 7. Through flushing, it can be ensured that the solid carbon dioxide 304 does not contain hydrogen sulfide, and the washed solid carbon dioxide 305 is obtained.

[0086] The washed solid carbon dioxide 305 descends to the dissolver 9 for dissolution treatment, and carbon dioxide-rich methanol 306 is obtained. The carbon dioxide-rich methanol 306 is transported to the shell side of the condensation heat exchanger 3 through the dissolver flow control valve 91 for flashing. Through flashing, the final cooling capacity is provided for the condensation of the mixture 103 of process gas and methanol. The pressure of the flashing is controlled by the condensation heat exchanger pressure control valve 31 to be 0.18 MPa. During the flashing process, gaseous carbon dioxide 307 is output from the top of the shell side of the condensation heat exchanger 3, and the gaseous carbon dioxide 307 is transported to the downstream treatment process through the condensation heat exchanger pressure control valve 31. During the flashing process, carbon dioxide-containing cold methanol 308 is output from the bottom of the shell side of the condensation heat exchanger 3. The carbon dioxide-containing cold methanol 308 is boosted to 0.8 MPa by the transfer pump 10 and then transported to the first heat exchanger 1 to be heated to -16°C to obtain carbon dioxide-containing hot methanol 309. The carbon dioxide-containing hot methanol 309 is transported to the dissolver 9 through the condensation heat exchanger liquid level control valve 32 to participate in the dissolution treatment.

[0087] According to the purification treatment results of this embodiment, the process gas 101 undergoes condensation treatment and gas-liquid separation. 79.73% of carbon dioxide, 80.91% of hydrogen sulfide, and 96.33% of carbonyl sulfide are condensed and separated in the acidic gas condensate 301, reducing the loads of the desulfurization tower 5 and the decarbonization tower 6, and reducing the consumption of methanol for absorbing hydrogen sulfide and carbon dioxide, thereby achieving the purpose of energy conservation and consumption reduction. In addition, 2193.72 kmol / h of carbon dioxide in the acidic gas condensate 301 is solidified and separated, increasing the concentration of the acidic gas 302 obtained after flash separation and reducing the output of the acidic gas 302, which is beneficial to reducing the energy consumption of the subsequent treatment of the acidic gas 302.

[0088] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A gas purification and separation method, comprising the following steps: mixing the process gas with methanol to obtain a mixture of the process gas and methanol; Condensing the mixture of the process gas and methanol to obtain a condensed process gas, wherein the process gas contains carbon dioxide and hydrogen sulfide; The condensed process gas is subjected to gas-liquid separation treatment to obtain gas-liquid separation process gas and acidic gas condensate respectively; The gas-liquid separation process gas is washed with methanol to perform desulfurization treatment, and desulfurized process gas and first sulfur-containing methanol are obtained respectively; The desulfurization process gas is washed with methanol to perform decarbonization treatment, thereby obtaining purified gas and carbon-rich methanol, and part of the carbon-rich methanol is recycled for the desulfurization treatment; The acidic gas condensate is subjected to a first flash separation treatment to obtain acidic gas, a second sulfur-containing methanol and solid carbon dioxide respectively; The solid carbon dioxide is washed with methanol, and the washed solid carbon dioxide is dissolved in methanol to obtain carbon dioxide-rich methanol; the carbon dioxide-rich methanol is subjected to a second flash separation treatment to obtain gaseous carbon dioxide and cold methanol containing carbon dioxide, respectively; the cold methanol containing carbon dioxide is heated and then reused to dissolve the washed solid carbon dioxide; The second flash separation process exchanges heat with the condensation process.

2. The gas purification and separation method according to claim 1, characterized in that: The temperature of the condensed process gas is -57 to -56°C.

3. The gas purification and separation method according to claim 1 or 2, characterized in that: Before the condensation treatment, the process gas and methanol mixture is further included: cooling the mixture to -36 to -10°C by a first process, and then cooling the mixture to -40 to -36°C by a second process; the first cooling and the heating are heat exchanged.

4. The gas purification and separation method according to claim 1, characterized in that: In the mixture of the process gas and methanol, the mass ratio of the process gas to the methanol is based on a molar ratio of carbon dioxide to methanol in the acidic gas condensate of 100:0.5-1.

5. The gas purification and separation method according to claim 1, characterized in that: The pressure of the first flash separation treatment is 0.40 to 0.52 MPa, and the temperature is -57 to -56°C.

6. The gas purification and separation method according to claim 1, characterized in that: The pressure of the second flash separation treatment is 0.15-0.52 MPa.

7. The gas purification and separation method according to claim 1, characterized in that: The temperature of the hot methanol containing carbon dioxide is -36 to 40°C.

8. A gas purification and separation device, comprising a condensing heat exchanger (3), a gas-liquid separator (4), a desulfurization tower (5), a decarbonization tower (6), a flash separator (7), a three-way pipe (8) and a dissolver (9); The condensing heat exchanger (3) is provided with a first feed port and a second feed port, which are respectively used for feeding a mixture of process gas and methanol and feeding carbon dioxide-rich material; and is also provided with a first discharge port, a second discharge port and a third discharge port, which are respectively used for discharging condensed process gas, discharging carbon dioxide-containing cold methanol and discharging gaseous carbon dioxide; the first discharge port is connected to the gas-liquid separator (4); The gas-liquid separator (4) is provided with a third feed port for condensing process gas feed; and is also provided with a fourth discharge port and a fifth discharge port for respectively discharging gas-liquid separation process gas and acidic gas condensate; the fourth discharge port is connected to the desulfurization tower (5), and the fifth discharge port is connected to the flash separator (7); The desulfurization tower (5) is provided with a fourth feed port and a fifth feed port, which are used for feeding gas-liquid separation process gas and methanol respectively; and is also provided with a sixth discharge port and a seventh discharge port, which are used for discharging the first sulfur-containing methanol and the desulfurization process gas respectively; the seventh discharge port is connected to the decarbonization tower (6); The decarbonization tower (6) is provided with a sixth feed port and a seventh feed port, which are used for feeding desulfurized gas and methanol respectively; and an eighth discharge port and a ninth discharge port, which are used for discharging purified gas and carbon-rich methanol respectively; the ninth discharge port is connected to the fifth feed port; The flash separator (7) is provided with an eighth feed port for feeding acidic gas condensate; a tenth discharge port and an eleventh discharge port for discharging acidic gas and second sulfur-containing methanol, respectively; a first feed port and a first discharge port for feeding washing liquid and discharging solid carbon dioxide; the first feed port and the first discharge port are connected to a three-way pipe (8); The three-way pipe (8) is provided with a second inlet and outlet for feeding solid carbon dioxide and discharging washing liquid; a ninth inlet is provided for feeding methanol; and a twelfth outlet is provided for discharging washed solid carbon dioxide; the ninth inlet is connected to the ninth outlet, and the twelfth outlet is connected to the dissolver (9); The dissolver (9) is provided with a tenth feed port and an eleventh feed port, which are respectively used for washing solid carbon dioxide feed and methanol feed; and is also provided with a thirteenth discharge port, which is used for discharging carbon dioxide-rich material; the thirteenth discharge port is connected to the second feed port.

9. The gas purification and separation device according to claim 8, characterized in that: The gas purification and separation device further comprises a first heat exchanger (1), a second heat exchanger (2) and a delivery pump (10); The first heat exchanger (1) is provided with a twelfth feed port and a thirteenth feed port, which are respectively used for feeding a mixture of process gas and methanol and feeding cold methanol containing carbon dioxide; it is also provided with a fourteenth discharge port and a fifteenth discharge port, which are respectively used for discharging a mixture of process gas and methanol and discharging hot methanol containing carbon dioxide; the fourteenth discharge port is connected to the first feed port via the second heat exchanger (2), the thirteenth feed port is connected to the second discharge port via a delivery pump (10), and the fifteenth discharge port is connected to the eleventh feed port.

10. The gas purification and separation device according to claim 9, characterized in that: The third discharge port is provided with a condensing heat exchanger pressure control valve (31), and a condensing heat exchanger liquid level control valve (32) is provided between the first heat exchanger (1) and the dissolver (9); A gas-liquid separator liquid level control valve (41) is provided between the gas-liquid separator (4) and the flash separator (7); The sixth discharge port is provided with a desulfurization tower liquid level control valve (51), and a desulfurization tower flow control valve (52) is provided between the fifth feed port and the ninth discharge port; The seventh feed port is provided with a lean methanol flow control valve (61), the ninth discharge port is connected to a carbon-rich methanol discharge pipeline, the carbon-rich methanol discharge pipeline is provided with a decarbonization tower liquid level control valve (62), and the desulfurization tower flow control valve (52) is located between the ninth discharge port and the decarbonization tower liquid level control valve (62); The tenth discharge port is provided with a flash separator pressure control valve (71), and the eleventh discharge port is provided with a flash separator liquid level control valve (72); A three-way pipe flow control valve (81) is provided between the ninth feed port and the ninth discharge port, and the three-way pipe flow control valve (81) is located between the desulfurization tower flow control valve (52) and the decarbonization tower liquid level control valve (62); A dissolver flow control valve (91) is provided between the thirteenth outlet and the second feed inlet.

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