A hydrocarbon recovery system and method

Abstract

The present application relates to a kind of hydrocarbon recovery system and recovery method, recovery system includes methanol synthesis system and methanol rectification system, also includes: first membrane separation device, first PSA hydrogen production device, gas storage tank, booster, shift system, second PSA hydrogen production device, second membrane separation device.The present application will be in methanol device blow-by gas and tail gas H2+CO Maximum degree of recycling, blow-by gas uses membrane separation+PSA gradient recovery process, the rest low-pressure tail gas is collected after pressurization, is introduced into shift process, the unreacted CO in it is converted into H2, then is purified by membrane separation and PSA device, finally obtains the industrial hydrogen of purity 99% (volume fraction) above, fully recovers the H2+CO effective gas in it;The present application fully exploits the marginal benefit of coal chemical industry, achieves the purpose of waste resource comprehensive utilization, thereby effectively reduces the device energy consumption, improves total carbon utilization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of methanol production, and particularly relates to a carbon-hydrogen recovery system and a recovery method. BACKGROUND

[0002] Hydrogen is an important chemical raw material and an important clean energy, and the water-gas hydrogen production, the cracked petroleum gas hydrogen production, the methanol cracking hydrogen production, the ammonia cracking hydrogen production, the water electrolysis hydrogen production and the like have high energy consumption.

[0003] In view of the characteristics of coal chemical industry that carbon is more and hydrogen is less, in order to improve the utilization efficiency of raw materials in the coal-to-methanol process, the methanol production device generally recovers and reuses hydrogen in the purge gas by using membrane separation and PSA technology. After hydrogen recovery, part of the desorption gas is produced, the desorption gas is used as tail gas, and a certain amount of CO and H2 is contained in the desorption gas, and the pressure of the desorption gas is low. Traditionally, the tail gas is burned as waste gas by being led to a flare. The crude methanol is subjected to pressure reduction flash evaporation before being subjected to rectification, so as to remove non-condensable gas contained in the crude methanol. The flash evaporation gas contains part of unreacted CO and H2, and the flash evaporation gas is traditionally used as fuel gas. A part of low-pressure methanol tail gas is produced at the top of the methanol pre-distillation column, and the low-pressure methanol tail gas also contains unreacted CO and H2. The low-pressure methanol tail gas is generally burned as waste gas by being led to a flare. That is, the prior art has the problems that H2 and CO cannot be fully recovered and utilized, and resources are wasted.

[0004] In order to solve the above problems, CN 111943139A discloses a recovery and utilization system and method for methanol purge gas of a coal-to-olefin device. The method is a recovery and utilization system for methanol purge gas, that is, the purge gas is first subjected to membrane separation, and the non-permeation gas is subjected to hydrogen purification by PSA. However, the methanol tail gas recovery rate of the method is low, and the recovery and utilization problem of low-pressure methanol tail gas cannot be solved. CN 105129731A “Recovery device for hydrogen in methanol purge gas” discloses a hydrogen recovery method for methanol purge gas, and adopts a recovery mode of membrane separation+PSA+membrane separation. However, the methanol tail gas recovery rate of the method is low, and the recovery and utilization problem of low-pressure methanol tail gas cannot be solved. In addition, in the above process, whether membrane separation or PSA is used, CO in the tail gas cannot be reasonably utilized, and finally the CO is used as fuel, which leads to high energy consumption of the entire device and low total carbon utilization rate. SUMMARY

[0005] The first technical problem to be solved by the present application is to provide a carbon-hydrogen recovery system capable of fully recovering CO and H2, thereby reducing the energy consumption of the device and improving the total carbon utilization rate, in view of the current status of the prior art.

[0006] The second technical problem to be solved by the present application is to provide a recovery method for the above carbon-hydrogen recovery system, in view of the current status of the prior art.

[0007] The present application adopts the technical scheme for solving at least one of the above technical problems:

[0008] A hydrocarbon recovery system, comprising a methanol synthesis system and a methanol rectification system, the methanol synthesis system being provided with a gas phase outlet for outputting purge gas and a liquid phase outlet for outputting liquid phase to the methanol rectification system, further comprising:

[0009] A first membrane separation device, arranged downstream of the methanol synthesis system, for inputting methanol purge gas, and used for extracting hydrogen from the methanol purge gas; the first membrane separation device being provided with a first outlet for returning the extracted hydrogen to the methanol synthesis system, and a second outlet for outputting non-permeated gas;

[0010] A first PSA hydrogen production device, having an inlet connected to the second outlet for inputting non-permeated gas, and used for obtaining purified hydrogen; the first PSA hydrogen production device being provided with a first hydrogen outlet for outputting the purified hydrogen, and a third outlet for outputting desorption gas;

[0011] A gas storage tank, provided with inlets for inputting overhead tail gas from the methanol rectification system, flash gas from a methanol flash tank, and desorption gas from the first PSA hydrogen production device, respectively, and used for storing mixed tail gas;

[0012] A booster, arranged at an outlet of the gas storage tank, and used for pressurizing the tail gas output therefrom;

[0013] A shift system, arranged downstream of the booster, for inputting pressurized tail gas, and used for performing CO shift reaction;

[0014] A second PSA hydrogen production device, having an inlet connected to a gas phase outlet of the shift system, and used for obtaining purified hydrogen; the second PSA hydrogen production device being provided with a second hydrogen outlet for outputting the purified hydrogen, and a fourth outlet for outputting desorption gas;

[0015] A second membrane separation device, arranged downstream of the second PSA hydrogen production device, having an inlet connected to the fourth outlet of the second PSA hydrogen production device, and used for extracting hydrogen from the desorption gas of the second PSA hydrogen production device; the second membrane separation device being provided with a fifth outlet for returning the extracted hydrogen to the methanol synthesis system, and a sixth outlet for outputting non-permeated gas.

[0016] The present application further comprises a steam production system, arranged downstream of the second membrane separation device, for inputting non-permeated gas from the second membrane separation device as fuel gas to produce steam.

[0017] Preferably, the steam production system is a boiler system, provided with a seventh outlet for outputting combustion tail gas, and a steam outlet for outputting steam.

[0018] Preferably, the methanol rectification system comprises a methanol flash tank, a top of the methanol flash tank being provided with an outlet for outputting flash gas, and a methanol pre-rectification column, a top of the methanol pre-rectification column being provided with an outlet for outputting column top tail gas.

[0019] Preferably, the gas storage tank is used for storing the flash gas from the methanol flash tank, the column top tail gas from the methanol pre-rectification column, and the desorption gas from the first PSA hydrogen production device.

[0020] A hydrocarbon recovery method, comprising the following steps:

[0021] (1) The methanol purge gas from a methanol synthesis system enters a first membrane separation device to extract hydrogen therefrom, the hydrogen produced by the membrane separation is returned to the methanol synthesis loop as raw material gas, and the non-permeated gas is further purified by a first PSA hydrogen production device, and low-pressure desorption gas produced by the first PSA hydrogen production device is stored in a gas storage tank together with flash gas produced by a methanol flash tank and column top tail gas from a methanol pre-rectification column;

[0022] (2) The mixed tail gas in the gas storage tank enters a booster to be pressurized to 2-5 MPaG and enters a shift system for CO shift reaction, the shift system can adopt adiabatic shift or isothermal shift technology; the CO in the mixed tail gas is shifted into H2, and the equilibrium concentration of CO after the shift is 0.1%-1% (volume fraction); the CO component in the mixed tail gas is fully utilized to be shifted into high-value-added H2, and the hydrogen content after the shift is 60%-80% (volume fraction);

[0023] (3) The gas phase with a hydrogen content of 60%-80% (volume fraction) after the shift is used as raw material gas to enter a second PSA hydrogen production device, and 85%-90% (volume fraction) of the hydrogen therein is converted into high-purity hydrogen with a purity of more than 99% (volume fraction); the CO content in the desorption gas obtained by the second PSA hydrogen production device is 0.5%-2% (volume fraction), and the H2 content is 20%-40% (volume fraction);

[0024] (4) The desorption gas obtained by the second PSA hydrogen production device is input into a second membrane separation device after being pressurized, and H2 therein is further extracted; the hydrogen concentration extracted by the membrane separation is 40%-80% (volume fraction), and the hydrogen is returned to the methanol synthesis system as raw material gas; the H2 contained in the non-permeated gas obtained by the membrane separation is used as fuel gas to produce steam.

[0025] In the above scheme, the low-pressure desorption gas produced by the first PSA hydrogen production device has a pressure of 0.02-0.05 MPaG, a CO content of 10%-40% (volume fraction), and a hydrogen content of 10%-40% (volume fraction);

[0026] The flash gas pressure generated by the methanol flash tank is 0.5-1.0MpaG, wherein the CO content is 2%-10% (volume fraction) and the hydrogen content is 20%-50% (volume fraction);

[0027] The tail gas pressure at the top of the methanol pre-distillation column is 0.02-0.05MpaG, wherein the CO content is 1%-5% (volume fraction) and the hydrogen content is 1%-6% (volume fraction).

[0028] Preferably, the gas storage tank with different volumes can be set according to the size of the methanol device; the gas storage tank is set to have a residence time of 30min-60min; and the CO concentration in the mixed tail gas of the gas storage tank is less than or equal to 40% (volume fraction).

[0029] The effective gas H2+CO recovery rate of the methanol device vent gas and various tail gases after hydrocarbon recovery reaches 95%-99% (volume fraction), the final tail gas amount discharged from the device is 0.1%-2% (volume fraction) of the total amount of the original vent gas and tail gas, the CO content in the final discharged tail gas can be reduced to 0.5%-3% (volume fraction), and the H2 content is reduced to 5%-15% (volume fraction).

[0030] Compared with the prior art, the advantages of the present application are that: the H2+CO in the methanol device vent gas and tail gas is maximally recovered and utilized, the vent gas is recovered by membrane separation+PSA gradient recovery process, the remaining low-pressure tail gas is collected and pressurized, and then introduced into a shift process to convert unreacted CO into H2, and then the hydrogen is purified by membrane separation and PSA device, and finally industrial hydrogen with a purity of more than 99% (volume fraction) is obtained, and the effective H2+CO gas is fully recovered; the present application fully explores the marginal benefits of coal chemical industry, achieves the purpose of comprehensive utilization of waste resources, and thus effectively reduces the energy consumption of the device and improves the total carbon utilization rate. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a structural schematic diagram of an embodiment of the present application;

[0032] Figure 2 is Figure 1 the corresponding process flow diagram. DETAILED DESCRIPTION

[0033] The present application will be further described in detail below with reference to the embodiments of the drawings.

[0034] As Figure 1 , 2As shown, the hydrocarbon recovery system of the present embodiment is a hydrocarbon recovery system of a methanol production device, which comprises a methanol synthesis system 1 and a methanol rectification system 2. The methanol synthesis system 1 is provided with a gas phase outlet for outputting purge gas and a liquid phase outlet for outputting liquid phase to the methanol rectification system 2. The hydrocarbon recovery system further comprises:

[0035] a first membrane separation device 3, which is arranged downstream of the methanol synthesis system 1 and is configured to receive the methanol purge gas and extract hydrogen from the methanol purge gas. The first membrane separation device 3 is provided with a first outlet for returning the extracted hydrogen to the methanol synthesis system 1 and a second outlet for outputting non-permeated gas.

[0036] a first PSA hydrogen production device 4, which is connected to the second outlet and configured to receive the non-permeated gas and produce purified hydrogen. The first PSA hydrogen production device 4 is provided with a first hydrogen outlet for outputting the purified hydrogen and a third outlet for outputting desorption gas.

[0037] a gas storage tank 5, which is provided with inlets for receiving overhead tail gas from the methanol rectification system 2, flash gas from a methanol flash tank, and desorption gas from the first PSA hydrogen production device 4, and is configured to store mixed tail gas.

[0038] a booster 6, which is arranged at the outlet of the gas storage tank 5 and is configured to pressurize the tail gas output therefrom.

[0039] a shift system 7, which is arranged downstream of the booster 6 and is configured to receive the pressurized tail gas and perform CO shift reaction.

[0040] a second PSA hydrogen production device 8, which is connected to the gas phase outlet of the shift system 7 and is configured to produce purified hydrogen. The second PSA hydrogen production device 8 is provided with a second hydrogen outlet for outputting the purified hydrogen and a fourth outlet for outputting desorption gas.

[0041] a second membrane separation device 9, which is arranged downstream of the second PSA hydrogen production device 8 and is connected to the fourth outlet of the second PSA hydrogen production device 8. The second membrane separation device 9 is configured to pressurize and extract hydrogen from the desorption gas of the second PSA hydrogen production device 8. The second membrane separation device 9 is provided with a fifth outlet for returning the extracted hydrogen to the methanol synthesis system 1 and a sixth outlet for outputting non-permeated gas.

[0042] a steam production system 10, which is arranged downstream of the second membrane separation device 9 and is configured to receive the non-permeated gas of the second membrane separation device 9 as fuel gas to produce steam. The steam production system 10 can be a boiler system, which is provided with a seventh outlet for outputting combustion tail gas and a steam outlet for outputting steam.

[0043] The methanol rectification system 2 of the embodiment comprises a methanol flash tank, a methanol pre-distillation column, an outlet is arranged at the top of the methanol flash tank for output of flash gas, and an outlet is arranged at the top of the methanol pre-distillation column for output of overhead gas. The gas storage tank 5 is used for storing the flash gas from the methanol flash tank, the overhead gas from the methanol pre-distillation column and the desorption gas from the first PSA hydrogen production device 4.

[0044] The hydrocarbon recovery method of the methanol production device of the embodiment comprises the following steps:

[0045] (1) The methanol purge gas from the methanol synthesis system 1 enters the first membrane separation device 3, and hydrogen gas is extracted therefrom. The hydrogen gas produced by the membrane separation is returned to the methanol synthesis loop as raw material gas. The non-permeated gas is further purified by the first PSA hydrogen production device 4, and the low-pressure desorption gas produced is stored in the gas storage tank 5 together with the flash gas from the methanol flash tank and the overhead gas from the methanol pre-distillation column. The low-pressure desorption gas produced by the first PSA hydrogen production device 4 has a pressure of 0.02-0.05 MPaG, a CO content of 10%-40% (volume fraction) and a hydrogen content of 10%-40% (volume fraction). The flash gas from the methanol flash tank has a pressure of 0.5-1.0 MPaG, a CO content of 2%-10% (volume fraction) and a hydrogen content of 20%-50% (volume fraction). The overhead gas from the methanol pre-distillation column has a pressure of 0.02-0.05 MPaG, a CO content of 1%-5% (volume fraction) and a hydrogen content of 1%-6% (volume fraction).

[0046] (2) The gas storage tank 5 having different volumes can be arranged according to the size of the methanol device. The gas storage tank 5 is arranged to have a residence time of 30-60 min. The CO concentration in the mixed tail gas of the gas storage tank 5 is less than or equal to 40% (volume fraction). The mixed tail gas in the gas storage tank 5 enters the booster 6, is pressurized to 2-5 MPaG and enters the shift system 7 for CO shift reaction. The shift system 7 can adopt adiabatic shift or isothermal shift technology. The CO in the mixed tail gas is shifted to H2. The equilibrium concentration of CO after the shift is 0.1%-1% (volume fraction). The CO component in the mixed tail gas is fully utilized to be shifted to high-value-added H2. The hydrogen content after the shift is 60%-80% (volume fraction).

[0047] (3) The gas phase having a hydrogen content of 60%-80% (volume fraction) after the shift is used as raw material gas and is fed to the second PSA hydrogen production device 8. 85%-90% (volume fraction) of the hydrogen gas therein is converted to high-purity hydrogen having a purity of more than 99% (volume fraction). The CO content in the desorption gas obtained by the second PSA hydrogen production device 8 is 0.5%-2% (volume fraction), and the H2 content is 20%-40% (volume fraction).

[0048] (4) The desorption tail gas obtained by the second PSA hydrogen production device 8 is input into the second membrane separation device 9 after being pressurized, and H2 therein is further extracted, the hydrogen concentration extracted by membrane separation is 40% ~ 80% (volume fraction), and is returned to the methanol synthesis system 1 as a supplementary gas, the H2 contained in the non-permeate gas obtained by membrane separation is used as fuel gas to produce steam.

[0049] The embodiment can perform gradient recycling of hydrogen in the purge gas and various tail gases generated by the methanol device, and convert CO therein into hydrogen for comprehensive utilization, so that the carbon resources in the device are used to the maximum extent, and the device benefit is maximized. After the hydrogen and carbon in the methanol device purge gas and various tail gases in the embodiment are recycled, the effective gas H2+CO recovery rate reaches 95% ~ 99% (volume fraction), the final exhaust gas amount of the device is 0.1% ~ 2% (volume fraction) of the total amount of the original purge gas + tail gas, and the CO content in the final exhaust gas can be reduced to 0.5% ~ 3% (volume fraction), and the H2 content is reduced to 5% ~ 15% (volume fraction).

[0050] Taking a 600,000-ton methanol device as an example, the hydrogen-carbon ratio (H2-CO2) / (CO+CO2) in the raw gas is relatively high, which can reach ~ 2.2. In order to prevent the accumulation of inert gas, ~ 24000 Nm 3 / h of purge gas is discharged in the production process, after the hydrogen is recycled by membrane separation and PSA, 17000 Nm 3 / h of hydrogen is recycled, and 7000 Nm 3 / h of desorption gas is generated. After the hydrogen in the purge gas is recycled, the low-pressure desorption gas generated has a CO content of 35% (volume fraction) and a hydrogen content of 30%, and the pressure is 0.02 MpaG; the methanol product generated by the methanol synthesis reaction is cooled and separated, and then enters the rectification system. Before entering the rectification system, the methanol is first flashed in a methanol flash tank, and the flash gas generated has a pressure of 0.5 MpaG, a CO content of 5% (volume fraction), and a hydrogen content of 48%; the tail gas at the top of the pre-distillation column has a pressure of 0.02 MpaG, a CO content of 1.5% (volume fraction), and a hydrogen content of 4%; the desorption gas generated by the purge gas recycling is 7000 Nm 3 / h, the methanol flash gas is ~ 1100 Nm 3 / h, the pre-column tail gas is ~ 500 Nm 3 / h, and the total amount of the three tail gases of the methanol is ~ 8600 Nm 3 / h, the mixed tail gas is stored in a gas storage tank, the gas storage tank is set to have a residence time of 35 min, and the CO concentration in the mixed tail gas is 30% (volume fraction); the tail gas in the gas storage tank enters a booster to be pressurized to 3 MPaG and then enters a shift system to perform a CO shift reaction; the shift system converts CO in the mixed tail gas into H2, and the balanced CO concentration after the shift is 0.5% (volume fraction); the CO component in the tail gas is fully utilized to be converted into high-value-added H2, and the hydrogen content after the shift is 75% (volume fraction); the hydrogen with a hydrogen content of 75% (volume fraction) after the shift is used as raw material gas and is sent to a PSA hydrogen production device, 85% (volume fraction) of the hydrogen in the PSA hydrogen production device can be converted into high-purity hydrogen (the concentration can be greater than or equal to 99% (volume fraction), which is an industrial hydrogen standard), the CO content in the PSA desorption gas is 1.4% (volume fraction), and the H2 content is approximately 31% (volume fraction); the desorption gas also contains a large amount of H2, and the concentration of the H2 is relatively low, and the cost of using the PSA technology is relatively high; after the desorption gas is pressurized, a membrane separation technology is used to further extract H2 therefrom, the concentration of the hydrogen extracted by the membrane separation is 50% (volume fraction), and the hydrogen is returned to the methanol synthesis device as supplemental gas and is used as raw material gas; the non-permeated gas in the membrane separator also contains 9.8% (volume fraction) H2 and 1.6% (volume fraction) CO, and the total amount is approximately 200 Nm 3 / h, which is used as fuel gas and is used to generate steam.

[0051] In the 600,000-ton methanol device in this embodiment, the effective gas H2+CO recovery rate of the released gas and various types of tail gas after hydrocarbon recovery is 99% (volume fraction), the tail gas amount finally discharged from the device is 0.6% (volume fraction) of the total amount of the original released gas and tail gas, and the CO content in the finally discharged tail gas can be reduced to 1.6% (volume fraction) and the H2 content can be reduced to 9.8% (volume fraction).

Claims

1. A hydrocarbon recovery method using a hydrocarbon recovery system comprising a methanol synthesis system and a methanol rectification system, wherein the methanol synthesis system is provided with a gas phase outlet for discharging a purge gas and a liquid phase outlet for supplying a liquid phase to the methanol rectification system, characterized in that Also comprising: a first membrane separation device provided downstream of the methanol synthesis system, into which the methanol purge gas is input, for extracting hydrogen from the methanol purge gas; the first membrane separation device is provided with a first outlet for returning the extracted hydrogen to the methanol synthesis system, and a second outlet for outputting the obtained non-permeated gas; a first PSA hydrogen production device, the inlet of which is connected to the second outlet for inputting the non-permeated gas, for obtaining purified hydrogen; the first PSA hydrogen production device is provided with a first hydrogen outlet for outputting the purified hydrogen, and a third outlet for outputting the desorption gas; a gas storage tank provided with inlets for inputting the overhead tail gas from the methanol rectification system, the flash gas from the methanol flash tank, and the desorption gas from the first PSA hydrogen production device, for storing the mixed tail gas; a booster provided at the outlet of the gas storage tank, for pressurizing the tail gas output therefrom; a shift system provided downstream of the booster, into which the pressurized tail gas is input, for performing CO shift reaction; a second PSA hydrogen production device, the inlet of which is connected to the gas phase outlet of the shift system, for obtaining purified hydrogen; the second PSA hydrogen production device is provided with a second hydrogen outlet for outputting the purified hydrogen, and a fourth outlet for outputting the desorption gas; a second membrane separation device provided downstream of the second PSA hydrogen production device, the inlet of which is connected to the fourth outlet of the second PSA hydrogen production device, for extracting hydrogen from the desorption gas of the second PSA hydrogen production device; the second membrane separation device is provided with a fifth outlet for returning the extracted hydrogen to the methanol synthesis system, and a sixth outlet for outputting the obtained non-permeated gas; a steam production system provided downstream of the second membrane separation device, into which the non-permeated gas obtained from the second membrane separation device is input as fuel gas to produce steam; comprising the following steps: (1) the methanol purge gas from the methanol synthesis system enters the first membrane separation device to extract hydrogen therefrom, the hydrogen produced by membrane separation is returned to the methanol synthesis circuit as raw material gas, and the non-permeated gas is further purified by the first PSA hydrogen production device, and the low-pressure desorption gas produced is stored in the gas storage tank together with the flash gas produced by the methanol flash tank and the overhead tail gas from the methanol pre-distillation column; (2) the mixed tail gas in the gas storage tank enters the booster, which pressurizes it to 2-5 MPa gauge pressure to enter the shift system to perform CO shift reaction, converting CO in the mixed tail gas to H2, and the equilibrium concentration of CO after shift is 0.1%-1%, fully utilizing the CO component in the mixed tail gas to convert it into high-value H2, and the hydrogen content after shift is 60%-80%; (3) the gas phase after shift with hydrogen content of 60%-80% is used as raw material gas to enter the second PSA hydrogen production device, and 85%-90% of the hydrogen therein is converted into high-purity hydrogen with purity above 99%, and the CO content in the desorption gas obtained from the second PSA hydrogen production device is 0.5%-2%, and the H2 content is 20%-40%. (4) The desorption tail gas from the second PSA hydrogen production device is input into the second membrane separation device after being pressurized, and H2 therein is further extracted, the hydrogen concentration extracted by the membrane separation is 40% ~ 80%, and the hydrogen is returned to the methanol synthesis system as a supplementary gas; the non-permeated gas obtained by the membrane separation contains H2 as fuel gas, which is used to produce steam.

2. The hydrocarbon recovery method of claim 1, wherein: The steam production system is a boiler system, which is provided with a seventh outlet for outputting the combustion tail gas and a steam outlet for outputting steam.

3. The hydrocarbon recovery method according to claim 1 or 2, characterized in that: The methanol rectification system comprises a methanol flash tank and a methanol pre-distillation column, the top of the methanol flash tank is provided with an outlet for outputting flash gas, and the top of the methanol pre-distillation column is provided with an outlet for outputting overhead tail gas.

4. The hydrocarbon recovery method of claim 3, wherein: The gas storage tank is used for storing the flash gas from the methanol flash tank, the overhead tail gas from the methanol pre-distillation column, and the desorption gas from the first PSA hydrogen production device.

5. The hydrocarbon recovery method according to claim 1 or 2, characterized in that: The low-pressure desorption gas generated by the first PSA hydrogen production device has a pressure of 0.02 ~ 0.05 MPa (gauge pressure), wherein the CO content is 10% ~ 40%, and the hydrogen content is 10% ~ 40%; The flash gas generated by the methanol flash tank has a pressure of 0.5 ~ 1.0 MPa (gauge pressure), wherein the CO content is 2% ~ 10%, and the hydrogen content is 20% ~ 50%; The overhead tail gas of the methanol pre-distillation column has a pressure of 0.02 ~ 0.05 MPa (gauge pressure), wherein the CO content is 1% ~ 5%, and the hydrogen content is 1% ~ 6%.

6. The hydrocarbon recovery method according to claim 1 or 2, characterized by: The gas storage tank is set to have a residence time of 30 min ~ 60 min, and the CO concentration in the mixed tail gas of the gas storage tank is less than or equal to 40%.

7. The hydrocarbon recovery method according to claim 1 or 2, characterized by: The CO content in the final exhaust tail gas is reduced to 0.5% ~ 3%, and the H2 content is reduced to 5% ~ 15%.

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