System and method for extracting krypton-xenon gas from methanol synthesis and refining tail gas

Abstract

The invention discloses a system and method for extracting krypton-xenon gas from methanol synthesis and refining tail gas, and the main process is as follows: the tail gas is subjected to throttling expansion, cooling and low-temperature rectification to recover light-component fuel gas (carbon monoxide and hydrogen) which is not subjected to synthesis reaction, and then carbon dioxide is recovered; and a krypton-xenon gas mixture is obtained and separated. In the process, generally, the consumption of cooling capacity is relatively large, so that the energy consumption is reduced as much as possible by adopting comprehensive utilization of internal cooling capacity and external cooling capacity recovery of the system; compared with a method for directly extracting krypton and xenon gas from air, the method has the advantages that components are easier to separate, the content is higher than that of krypton and xenon gas in air, and the effect of comprehensively utilizing tail gas can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of rare gas recovery in a cryogenic separation process, and in particular to a system and method for extracting krypton-xenon gas from methanol synthesis and refined tail gas. Background Art

[0002] Krypton-xenon gas is an expensive rare gas widely used in industry. The content of krypton in the air is

[0003] 1.14ppm, xenon content 87ppb. The traditional method of extracting krypton and xenon gas is to use the product liquid oxygen of air separation for further distillation extraction, which has the disadvantages of low raw material content, low extraction rate, high energy consumption, high threshold, and the need to change the structure of the air separation cold box.

[0004] There are precedents for extracting krypton-xenon gas from industrial exhaust gas, but it is limited to synthetic ammonia exhaust gas and nuclear reaction waste gas. Among them, the krypton-xenon gas content in nuclear reaction exhaust gas is relatively high, but because there are many radioactive substances in the exhaust gas, there are multiple radioactive substances and different isotopes, so it cannot be directly extracted and utilized, which has great limitations.

[0005] Since krypton and xenon gases are concentrated in liquid oxygen during air separation due to their low content, they are not extracted in conventional air separation. Liquid oxygen will be discharged from the air separation system in the form of oxygen, and oxygen will be used as a raw material in the next stage. The oxygen produced by air separation is often consumed by industrial plants. The most critical part of a large-scale coal chemical plant is the coal gasification plant, and the main raw materials of the coal gasification plant are coal and oxygen. Coal chemical industry is an important pillar industry in my country, among which coal-to-methanol is one of the typical coal chemical processes, including air separation, coal gasification, water-gas shift, acid gas removal, methanol synthesis and refining units. Krypton and xenon gases in the air pass through these units and are eventually enriched in the tail gas.

[0006] At present, the domestic production capacity of coal-to-methanol is greater than that of other coal chemical products. Coal-to-methanol must first undergo a coal gasification process, which basically converts all the input oxygen into synthesis gas. Krypton-xenon gas is stable in nature and will not react in the coal-to-methanol process. It will be discharged from the system with the tail gas in the subsequent production process. It is easier to extract krypton-xenon gas from tail gas than from liquid oxygen in the air separation process, so it is considered to combine coal-to-methanol with krypton-xenon gas extraction. Summary of the invention

[0007] In order to overcome the problems of high energy consumption in the above-mentioned prior art methods for extracting krypton-xenon gas, low krypton-xenon gas content in raw materials and harsh application conditions, the purpose of the present invention is to provide a system and method for extracting krypton-xenon gas from methanol synthesis and refined tail gas. The present invention is based on a deep cold separation process to design a system and method for extracting krypton-xenon gas from a mixed tail gas composed of methanol synthesis purge gas and methanol refined tail gas (hereinafter referred to as methanol synthesis and refined tail gas). The system and method can achieve low energy consumption, no impact on the original air separation production, and comprehensive utilization of tail gas.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A system for extracting krypton-xenon gas from methanol synthesis and refined tail gas, comprising a first precooling heat exchanger 1, a hot side inlet of the first precooling heat exchanger 1 is fed with methanol synthesis and refined tail gas, a hot side outlet of the first precooling heat exchanger 1 is connected to a hot side inlet of a second precooling heat exchanger 2, a hot side outlet of the second precooling heat exchanger 2 is connected to an inlet of a pre-distillation tower 3, a bottom of the pre-distillation tower 3 is connected to a cold side inlet of the first precooling heat exchanger 1, a cold side outlet of the first precooling heat exchanger 1 is connected to an inlet of a heavy component removal distillation tower 7; a top of the pre-distillation tower 3 is connected to an inlet of a light component separation distillation tower 4; a top of the heavy component removal distillation tower 7 is connected to an inlet of a compressor heat exchanger group 8, and a heavy component removal distillation tower 7 is discharged from the bottom as a heavy component. component sewage; the top of the light component separation distillation tower 4 is connected to the inlet of the cold recovery heat exchanger 9, the outlet of the cold recovery heat exchanger 9 is connected to the cold side inlet of the second precooling heat exchanger 2, and the cold side outlet of the second precooling heat exchanger 2 is fuel gas; the bottom of the light component separation distillation tower 4 is connected to the inlet of the CO2 removal distillation tower 5, and the top of the CO2 removal distillation tower 5 is connected to the inlet of the krypton-xenon gas separation distillation tower 6; the bottom of the CO2 removal distillation tower 5 is combined with the top logistics of the heavy component removal distillation tower 7 and then passed into the compressor heat exchanger group 8 for compression and liquefaction of CO2, and the outlet of the compressor heat exchanger group 8 is liquid CO2; the top of the krypton-xenon gas separation distillation tower 6 is the krypton gas outlet, and the bottom of the krypton-xenon gas separation tower 6 is the xenon gas outlet.

[0010] All equipment except the heavy component separation distillation tower 7 and the compressor heat exchanger group 8 work under cryogenic conditions, and the reboilers of the pre-distillation tower 3, the light component separation distillation tower 4, the CO2 removal distillation tower 5, the krypton-xenon gas separation distillation tower 6 and the heavy component removal distillation tower 7 can all recover part of the cold energy, and only the condensers of the pre-distillation tower 3 and the light component separation tower 4 need cold energy input. The energy utilization within the system can be achieved, with less external input, and multi-level energy utilization can be achieved.

[0011] The first precooling heat exchanger 1 and the second precooling heat exchanger 2 are both shell and tube heat exchangers, and the cold recovery heat exchanger 9 provides cold energy for the top condensers of the CO2 removal distillation tower 5, the krypton-xenon gas separation distillation tower 6 and the heavy component removal distillation tower 7, in order to utilize the cold energy in the system.

[0012] The whole system needs a cold box to operate, and air separation is needed to produce cold energy for liquid nitrogen. An external cold box can be connected near the air separation without changing the cold box structure.

[0013] Methanol synthesis and refined tail gas is the main by-product CH4 and some unreacted H2 and CO produced by the methanol synthesis unit. The material environment of the tail gas is an oxygen-free environment. The pressure and temperature of methanol synthesis tail gas are relatively high, and the extraction of krypton and xenon gas needs to be carried out in a deep cold environment. As some impurities are easy to separate under high pressure, they are pretreated under high pressure to first remove some easily separated heavy component impurities, then remove light component impurities after decompression, and then remove the remaining CO2, and finally separate the krypton and xenon gases by distillation.

[0014] The working method of the system for extracting krypton-xenon gas from methanol synthesis and refined tail gas comprises the following steps:

[0015] Step 1: Precooling and pre-separation:

[0016] The temperature and pressure of the tail gas raw materials for methanol synthesis and refining are high, and the tail gas raw materials need to be pre-cooled and cooled, and the easily removable heavy component impurity methanol is removed at the same time; the tail gas for methanol synthesis and refining is first heat-exchanged with the liquid in the bottom of the pre-distillation tower 3 and the gas at the top of the light component separation distillation tower 4, respectively, so that the tail gas raw materials are pre-cooled and then sent to the pre-distillation tower 3 for distillation pretreatment, and the gas at the top of the pre-distillation tower 3 is throttled by a valve and expanded to cool down, and then passed into the light component separation distillation tower 4, and the liquid part extracted from the bottom of the pre-distillation tower 3 is throttled by a valve and expanded, and the temperature is reduced, and then the liquid part is heat-exchanged with the tail gas raw materials through the first pre-cooling heat exchanger 1, and then passed into the heavy component removal tower 7 to remove the heavy component methanol; the top of the heavy component removal distillation tower 7 extracts high-purity CO2 and is sent to the compressor heat exchanger group 8 for pressurized liquefaction, and the bottom of the heavy component removal distillation tower 7 is crude methanol;

[0017] Step 2: Produce byproduct fuel gas:

[0018] After removing all methanol, water and part of CO2 impurities, the remaining impurities are mostly light component impurities, and light component impurities need to be separated at relatively low pressure and temperature, so the material temperature is reduced by throttling expansion operation, on the one hand to provide cooling capacity for tail gas treatment, on the other hand to reach the pressure for subsequent extraction and separation; the gas discharged from the top of the light component separation distillation tower 4 passes through the cooling capacity recovery heat exchanger 9 and then enters the second pre-cooling heat exchanger 2 to exchange heat with the tail gas raw material and then is discharged from the system. The main components of the fuel gas stream are high calorific value combustible gases such as H2, CH4, CO, and N2, which can be used as fuel gas to produce steam; the liquid in the bottom of the light component separation distillation tower 4 is passed into the CO2 removal distillation tower 5;

[0019] Step 3: CO2 collection and krypton-xenon distillation separation:

[0020] When most of the light component impurities are processed, the remaining main components are CO2 and krypton-xenon gas; CO2 is distilled out from the bottom of the tower through distillation of the CO2 removal distillation tower 5, and the materials extracted from the top and bottom of the pre-distillation tower 3 are separated by distillation to obtain Kr and Xe; the top of the CO2 removal distillation tower 5 is extracted as a mixture of Kr and Xe and enters the krypton-xenon gas separation distillation tower 6, and the bottom of the CO2 removal distillation tower 5 is extracted as high-purity CO2 and passed into the compressor heat exchanger group 8 for pressurized cooling and liquefaction of CO2.

[0021] The precooling in step 1 needs to be above the minimum liquefaction pressure of carbon dioxide, 5.17 bar, and less than the liquefaction temperature of -56.6°C at this pressure. If the temperature here is too low below the liquefaction temperature, it will result in excessive energy consumption, which is uneconomical, but has greater operational flexibility. On the contrary, the closer to the liquefaction temperature, the less energy is consumed, the more economical, and the less operational flexibility. Similarly, when the pressure is too high above the minimum liquefaction pressure, additional work is required, which requires more energy. When the original pressure of the exhaust gas is directly used, when the pressure is higher than the liquefaction pressure, part of the pressure can be throttled and expanded to convert into cooling capacity. On the contrary, when the pressure is lower than the liquefaction pressure, some energy needs to be input.

[0022] The purity of the product extracted from the bottom of the krypton-xenon separation distillation tower 6 is 99.9% Xe; the purity of the product extracted from the top of the tower is 99.9% Kr.

[0023] In step 1, the inlet temperature of the pre-distillation tower 3 varies according to the different methanol synthesis pressures, ranging from -60 to -80° C. According to simulation calculations, this temperature range is economically sound and can meet the requirements for complete liquefaction of CO2.

[0024] In step 1, the light component impurities are separated at a pressure of 6-10 bar. According to simulation calculations, this pressure range is economical and can meet the complete liquefaction of CO2.

[0025] In step 1, the pressure of the purge gas will vary according to the synthesis pressure, but it will generally be greater than 20 bar. The separation of heavy components under high pressure has a better separation effect. The inlet temperature of the pre-distillation tower will vary according to the pressure and is about -70°C. The tail gas needs to be pre-cooled, so the material of the discharge system and the cooling capacity in the system are used for pre-cooling. If the pressure of the material is too high, the material can be throttled and expanded to cool it down.

[0026] In step 2, the light component is easier to separate than the heavy component under low pressure conditions, but the subsequent CO2 separation process needs to be comprehensively considered, so a pressure of 6-10 bar is used for separation. The temperature of the reboiler at the top of this tower is relatively low, and the cold energy can be recovered and applied.

[0027] In step 3, when CO2 is separated, the minimum liquefaction pressure of CO2 is 5.17 bar, and the liquefaction temperature under this pressure is -56.6°C; the pressure of the material containing CO2 in the entire process cannot be too low, otherwise it will cause CO2 to become solid and block the pipeline, resulting in failure of normal production. Distillation recovery of carbon dioxide can maximize the concentration of rare gases while recycling and reusing carbon dioxide.

[0028] Compared with the existing inventions, the present invention has the following advantages:

[0029] 1) The system and method of the present invention further extract krypton-xenon gas from the tail gas discharged from the methanol synthesis and methanol refining stages of coal-to-methanol. The main components of the tail gas are hydrogen, carbon dioxide, nitrogen, methane, carbon monoxide, etc. Compared with liquid oxygen in the air, the boiling point difference between krypton and xenon is relatively large, and it is easier to separate.

[0030] 2) The krypton in the tail gas used in the present invention is more than 20 times that in the air, and the xenon in the tail gas is more than 5 times that in the air; in terms of extraction rate, the krypton extraction rate of the method of the present invention is as high as 90%, and the xenon extraction rate is more than 70%.

[0031] 3) The equipment used for separating impurity gases of the present invention can all use small equipment, which can greatly reduce the equipment investment and management costs for extracting krypton-xenon gas, saving investment and reducing energy consumption. The present invention does not need to change the cold box structure in the air separation, and the required cooling capacity can be directly connected to the liquid nitrogen outlet of the air separation cold box inlet of the present invention system.

[0032] 4) The present invention can achieve comprehensive utilization of methanol synthesis and refined tail gas, not only separating the fuel gas, but also capturing CO2, reducing CO2 emissions, and extracting krypton-xenon gas through deep cold separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1It is a system schematic diagram of the present invention.

[0034] Description of reference numerals:

[0035] 1. The first precooling heat exchanger, 2. The second precooling heat exchanger, 3. The pre-distillation tower, 4. The light component separation distillation tower, 5. The CO2 removal distillation tower, 6. The krypton-xenon gas separation distillation tower, 7. The heavy component removal distillation tower, 8. The compressor heat exchanger group, 9. The cold recovery heat exchanger. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention clearer and more concise, the present invention is further described in detail below in conjunction with the accompanying drawings and an embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] like Figure 1 As shown, the high-temperature and high-pressure methanol synthesis and refined tail gas is pre-cooled by the first pre-cooling heat exchanger 1 and the second pre-cooling heat exchanger 2, and then the tail gas is passed into the pre-distillation tower 3 for pre-distillation, wherein the light component at the top of the pre-distillation tower 3 is decompressed and cooled by a valve and then sent to the light component separation distillation tower 4; the heavy component in the bottom of the pre-distillation tower 3 is decompressed and cooled by a valve and then passed into the first pre-cooling heat exchanger 1 as a cold source for pre-cooling the raw tail gas and then sent to the heavy component removal distillation tower 7 to remove the heavy component methanol, which can be sent back to the methanol refining system or directly discharged to the sewage treatment system. The light component at the top of the light component separation distillation tower 4 enters the cold recovery heat exchanger 9 to recover the cold, and then is sent to the second pre-cooling heat exchanger 2 as a cold source for heat exchange and then discharged from the system; the liquid in the bottom of the light component separation distillation tower 4 is sent to the CO2 removal distillation tower 5 for distillation. The top of CO2 removal distillation tower 5 is liquid phase, which is passed into krypton-xenon gas separation distillation tower 6; the bottom of CO2 removal distillation tower 5 is CO2, which is passed into compressor heat exchanger group 8 for pressurized liquefaction. The bottom of krypton-xenon gas separation distillation tower 6 produces xenon gas, and the top produces krypton gas. The top of heavy component removal tower 7 produces CO2, which is mixed with the material produced from the bottom of CO2 removal distillation tower 5 and then passed into compressor heat exchanger group 8; the bottom of heavy component removal distillation tower 7 produces sewage.

[0038] Example 1:

[0039] In the coal gasification unit of the pre-stage of coal-to-methanol, the gasifying agent oxygen does not undergo gas extraction of argon, krypton and xenon.

[0040] Refer to the attached Figure 1The tail gas temperature of the coal-to-methanol process in a certain factory is 44.1℃, the pressure is 30bar, the tail gas volume is 1279.53kmol / h, and the main substance is H2 with a content of up to 80%. The tail gas is first precooled to -60℃ through the first precooling heat exchanger 1 and the second precooling heat exchanger 2. Since high pressure is conducive to the pre-separation of heavy components, it directly enters the pre-distillation tower 3 to remove the easily removable heavy components, and then the separated two components are decompressed to 6bar, and the light component material is further cooled to -103℃, and the heavy component material is further cooled to 1.4℃. Among them, the light component extracted from the top of the pre-distillation tower 3 is sent to the light component separation distillation tower 4 for removing fuel gas. The outlet temperature of the top fuel gas is -88℃, and the amount of fuel gas is 1166.81kmol / h. After the cold is recovered, it enters the second precooling heat exchanger 2 that uses the remaining cold as a cold source for heat exchange and then is discharged from the system. The discharge temperature is 4℃. The liquid extracted from the bottom of the light component separation distillation tower 4 is sent to the CO2 removal distillation tower 5 to further remove CO2, and the separated CO2 is sent to the compressor heat exchanger group 8 for recovery and sealing; the light component at the top of the CO2 removal distillation tower 5 is sent to the krypton-xenon gas separation distillation tower 6 for separation of xenon and krypton. Among them, the output of xenon is 0.11kg / h; the krypton gas production capacity is 2.54kg / h. The heavy component at the bottom of the pre-distillation tower 3 is depressurized and enters the heavy component removal distillation tower 7. The CO2 discharged from the top of the tower is sent to the compressor heat exchanger group 8. The outlet temperature of the compressor heat exchanger group 8 is 20°C, the pressure is 60bar, and the amount of CO2 recovered is 90kmol / h.

[0041] The results show that the purity of CO2 in the process of Example 1 reaches 99.9%, and the recovery rate is greater than 99.9%. The recovery rate of krypton is 90%, and the recovery rate of xenon is 96.5%. If the recovery rate is reduced, energy consumption can be reduced.

[0042] The present invention extracts rare gases from the purge gas of circulating gas in the methanol synthesis process and the mixed gas of light components in the methanol refining process, recovers fuel gas, and captures CO2. The content of krypton-xenon gas in methanol synthesis and refining raw gas is high, and has a higher extraction value compared with krypton-xenon gas in air.

[0043] Krypton-xenon gas mainly comes from oxygen, a gasifying agent used in the coal gasification process. Oxygen separates nitrogen and oxygen in the air through the air separation process. In this process, krypton-xenon gas will be enriched in liquid oxygen. Krypton-xenon gas arrives at the methanol synthesis section along with the coal-to-methanol process and is discharged from the system along with the circulating gas purge gas and light component impurities. Through Aspen simulation calculations and factory sample analysis, the content of krypton-xenon gas in the tail gas is significantly higher than the content of krypton-xenon gas in the air. The main substances in the tail gas are hydrogen, methane, carbon dioxide, carbon monoxide, methanol and other substances.

Claims

1. A system for extracting krypton-xenon gas from methanol synthesis and refined tail gas, characterized in that: The invention comprises a first precooling heat exchanger (1), wherein the hot side inlet of the first precooling heat exchanger (1) is fed with methanol synthesis and refined tail gas, the hot side outlet of the first precooling heat exchanger (1) is connected to the hot side inlet of the second precooling heat exchanger (2), the hot side outlet of the second precooling heat exchanger (2) is connected to the inlet of a pre-distillation tower (3), the bottom of the pre-distillation tower (3) is connected to the cold side inlet of the first precooling heat exchanger (1), the cold side outlet of the first precooling heat exchanger (1) is connected to the inlet of a heavy component removal distillation tower (7); the top of the pre-distillation tower (3) is connected to the inlet of a light component separation distillation tower (4); the top of the heavy component removal distillation tower (7) is connected to the inlet of a compressor heat exchanger group (8), and the bottom of the heavy component removal distillation tower (7) is discharged as heavy component sewage; the light component separation distillation tower The top of the tower (4) is connected to the inlet of the cold recovery heat exchanger (9), and the outlet of the cold recovery heat exchanger (9) is connected to the cold side inlet of the second precooling heat exchanger (2), and the cold side outlet of the second precooling heat exchanger (2) is fuel gas; the bottom of the light component separation distillation tower (4) is connected to the inlet of the CO2 removal distillation tower (5), and the top of the CO2 removal distillation tower (5) is connected to the inlet of the krypton-xenon gas separation distillation tower (6); the bottom of the CO2 removal distillation tower (5) and the top of the heavy component removal distillation tower (7) are combined and then introduced into the compressor heat exchanger group (8) for compression and liquefaction of CO2, and the outlet of the compressor heat exchanger group (8) is liquid CO2; the top of the krypton-xenon gas separation distillation tower (6) is the krypton gas outlet, and the bottom of the krypton-xenon gas separation distillation tower (6) is the xenon gas outlet.

2. The system for extracting krypton-xenon gas from methanol synthesis and purification tail gas according to claim 1 is characterized in that: all equipment except the heavy component separation distillation tower (7) and the compressor heat exchanger group (8) operate under cryogenic conditions, and the reboilers of the pre-distillation tower (3), the light component separation distillation tower (4), the CO2 removal distillation tower (5), the krypton-xenon gas separation distillation tower (6) and the heavy component removal distillation tower (7) can all recover part of the cold energy, and only the condensers of the pre-distillation tower (3) and the light component separation distillation tower (4) require cold energy input.

3. The system for extracting krypton-xenon gas from methanol synthesis and refined tail gas according to claim 1 is characterized in that: the first precooling heat exchanger (1) and the second precooling heat exchanger (2) are both shell and tube heat exchangers, and the cold recovery heat exchanger (9) provides cold energy for the top condensers of the CO2 removal distillation tower (5), the krypton-xenon gas separation distillation tower (6) and the heavy component removal distillation tower (7), so as to utilize the cold energy in the system.

4. The system for extracting krypton-xenon gas from methanol synthesis and refined tail gas according to claim 1 is characterized in that: the entire system requires a cold box to operate, requires the cold capacity of liquid nitrogen produced by air separation, and an external cold box is connected near the air separation without changing the cold box structure.

5. The working method of the system for extracting krypton-xenon gas from methanol synthesis and refined tail gas according to any one of claims 1 to 4, characterized in that: The steps include: Step 1: Precooling and pre-separation: The temperature and pressure of the tail gas raw materials for methanol synthesis and refining are high, and the tail gas raw materials need to be pre-cooled and cooled, and the easily removable heavy component impurity methanol is removed at the same time. The tail gas for methanol synthesis and refining is first heat-exchanged with the liquid in the bottom of the pre-distillation tower (3) and the gas at the top of the light component separation distillation tower (4), respectively, so that the tail gas raw materials are pre-cooled and then sent to the pre-distillation tower (3) for distillation pretreatment. The gas at the top of the pre-distillation tower (3) is throttled by a valve and expanded to reduce the temperature before being passed into the light component separation distillation tower (4). The liquid part extracted from the bottom of the pre-distillation tower (3) is throttled by a valve and expanded to reduce the temperature after passing through the first pre-cooling heat exchanger (1) and the tail gas raw materials. After that, it is passed into the heavy component removal distillation tower (7) to remove the heavy component methanol. The top of the heavy component removal distillation tower (7) extracts high-purity CO2 and sends it to the compressor heat exchanger group (8) for pressurized liquefaction. The bottom of the heavy component removal distillation tower (7) is crude methanol. Step 2: Produce byproduct fuel gas: After removing all methanol, water and part of CO2 impurities, the remaining impurities are mostly light component impurities, and light component impurities need to be separated at relatively low pressure and temperature, so the material temperature is reduced by throttling expansion operation, on the one hand to provide cooling capacity for tail gas treatment, and on the other hand to reach the pressure for subsequent extraction and separation; the gas discharged from the top of the light component separation distillation tower (4) passes through the cold recovery heat exchanger (9) and then enters the second pre-cooling heat exchanger (2) and heat exchanges with the tail gas raw material before being discharged from the system. The main components of the fuel gas stream are high calorific value combustible gases such as H2, CH4, CO, and N2, which can be used as fuel gas to produce steam; the liquid in the bottom of the light component separation distillation tower (4) is passed into the CO2 removal distillation tower (5); Step 3: CO2 collection and krypton-xenon distillation separation: After most of the light impurities are processed, the remaining main components are CO2 and krypton-xenon gas; CO2 is distilled out from the bottom of the tower by distillation in a CO2 removal distillation tower (5), and the materials extracted from the top and bottom of the pre-distillation tower 3 are separated by distillation to obtain Kr and Xe; the top of the CO2 removal distillation tower (5) is extracted as a mixture of Kr and Xe and enters the krypton-xenon gas separation distillation tower (6), and the bottom of the CO2 removal distillation tower (5) is extracted as high-purity CO2 and passed into a compressor heat exchanger group (8) for pressurized cooling and liquefaction of CO2.

6. The working method according to claim 5, characterized in that: The precooling in step 1 needs to be above the minimum liquefaction pressure of carbon dioxide, 5.17 bar, and at the same time below the liquefaction temperature of -56.6°C at this pressure.

7. The working method according to claim 5, characterized in that: The purity of the product extracted from the bottom of the krypton-xenon separation distillation tower (6) is 99.9% Xe; the purity of the product extracted from the top of the tower is 99.9% Kr.

8. The working method according to claim 5, characterized in that: In step 1, the inlet temperature of the pre-distillation tower (3) varies according to the methanol synthesis pressure, and the range is -60 to -80°C.

9. The working method according to claim 5, characterized in that: In step 1, the light component impurities are separated using a pressure of 6-10 bar.

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