Low-temperature low-sulfur methanol washing technology matched with coal water slurry gasification device

Abstract

The invention relates to the technical field of low-temperature methanol washing, in particular to a low-temperature low-sulfur methanol washing method matched with a coal water slurry gasification device and a washing device of the low-temperature low-sulfur methanol washing method. According to the method, a medium-pressure flash evaporation process is optimized, flash evaporation gas obtained by flash evaporation of a CO2 flash evaporation tower and a H2S flash evaporation tower is subjected to series-connection washing through B-strand semi-barren liquor methanol, low-sulfur carbon-rich methanol generated through washing is sent to an H2S absorption tower to continue to wash synthesis gas, compared with the prior art, the use amount of CO2-rich methanol in the H2S flash evaporation tower is reduced, and the production cost is reduced. And meanwhile, the adverse effect on the high-quality low-level cooling capacity generated by the re-absorption tower is reduced, and the energy consumption of the device is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature methanol washing, and specifically relates to a low-temperature and low-sulfur methanol washing method for a supporting water coal slurry gasification device and a low-temperature and low-sulfur methanol washing device for a supporting water coal slurry gasification device. Background Art

[0002] In the syngas produced by the water coal slurry gasification technology, H 2 and CO are called effective gases. At the same time, the syngas also contains a large amount of CO 2 and trace amounts of H 2 S, COS, NH 3 , HCN and other components. Among them, H 2 and CO are raw material gases for synthesizing chemical products such as methanol and ammonia after adjusting the hydrogen-carbon ratio through the shift unit. Acid gases CO 2 and H 2 S are generally poisons for synthesis catalysts, so they must be removed before the synthesis process.

[0003] The low-temperature methanol washing technology uses low-temperature methanol as the absorption solvent, and utilizes the characteristic that low-temperature methanol has a great solubility for acid gases to remove H 2 S and CO 2 and other acid gases in the syngas, and at the same time removes trace components such as HCN and NH 3 . At present, the innovative research on the low-temperature methanol washing technology mainly focuses on the recycling of the rich CO 2 methanol through pressure reduction and flash evaporation. The typical process flow mainly includes the lean liquid - semi-lean liquid process, but there are technical bottlenecks in further optimizing and innovating the lean liquid - semi-lean liquid process. Therefore, it is necessary to adjust the technical innovation direction of the low-temperature methanol washing process.

[0004] In the low-temperature methanol washing process flow, the rich CO 2 methanol can be recycled through pressure reduction and flash evaporation, but the H 2 S-containing methanol must be recycled through thermal regeneration, which is the main energy-consuming source of the low-temperature methanol washing. Therefore, how to enhance the use efficiency of the H 2 S-containing methanol, so as to reduce the total amount of the rich CO 2 methanol contaminated by the H 2 S-containing methanol is the key factor for technological innovation.

[0005] CN201110260570.0 discloses a low-temperature methanol washing process. First, in this low-temperature methanol washing process, the rich CO 2 methanol is used to wash the syngas in the H 2 S absorption tower, which increases the amount of the rich CO 2 methanol contaminated by the H 2The total amount of contaminated methanol needs to be regenerated by consuming steam in the thermal regeneration system before it can be recycled, resulting in high energy consumption. Secondly, in the reabsorption tower, CO 2 In the flash evaporation section, rich CO 2 Methanol washes the rich H 2 While washing the flash gas of contaminated methanol, it directly mixes with the rich H 2 Contaminated methanol, and itself is enriched with H 2 Contaminated methanol, and the resulting low-concentration H 2 Contaminated methanol is not fully utilized either. Finally, the selection of the washing methanol for the medium-pressure flash gas is not reasonable. Using rich H 2 Contaminated methanol to wash the flash gas, and after washing, the rich H 2 The CO 2 content in the contaminated methanol is relatively low, and then flashing in the reabsorption tower is not conducive to the generation of high-quality low-temperature cooling capacity, and generally is not conducive to reducing the comprehensive energy consumption of the cold methanol washing unit. Summary of the Invention

[0006] The object of the present invention is to overcome the above technical problems and provide a low-temperature and low-sulfur methanol washing method and device for a coal water slurry gasification device. This method optimizes the H 2 S absorption process, uses low-sulfur and carbon-rich methanol to wash the syngas, and reduces the usage amount of rich CO 2 Methanol; by optimizing the medium-pressure flash evaporation process, using B-share semi-lean liquid methanol to wash the CO 2 Flash gas and H 2 S flash gas respectively to obtain low-sulfur and carbon-rich methanol, and reduces the proportion of CO 2 Gas contaminated by H 2 S gas in the whole system; by optimizing the reabsorption tower process, low-H 2 Methanol is generated, and at the same time, the low-H 2 Methanol is prevented from being deeply contaminated, making the cold methanol washing unit have the characteristics of low comprehensive energy consumption.

[0007] To achieve the above object, the first aspect of the present invention provides a low-temperature and low-sulfur methanol washing method for a coal water slurry gasification device, which method includes:

[0008] Subject the syngas to H 2 S absorption, and subject the desulfurized gas obtained to CO 2 Absorption to obtain the first rich CO 2 Methanol is divided into two streams, and the second stream of rich CO 2 After the methanol is cooled for the first time, it is subjected to CO 2 Flash evaporation to obtain the rich CO 2 Methanol after flash evaporation and CO 2 Flash gas; the first rich H 2 Obtained by the H 2The methanol is divided into two streams, and the second stream is rich in H 2 The methanol is cooled for the second time and then undergoes H 2 flash evaporation to obtain the H-rich methanol after flash evaporation 2 methanol and H 2 flash vapor;

[0009] The CO-rich methanol after the flash evaporation 2 is subjected to the first flash evaporation. The semi-lean methanol obtained is divided into three streams. The second stream of semi-lean methanol is subjected to the second flash evaporation. The H-rich methanol after the flash evaporation 2 is subjected to the third flash evaporation to obtain the sulfur-containing gas phase. The solution after the second flash evaporation is subjected to the first washing to obtain the low-H 2 methanol;

[0010] Among them, the first stream of semi-lean methanol is divided into two streams. The A-stream of semi-lean methanol returns and undergoes the CO 2 absorption; the B-stream of semi-lean methanol and the CO 2 flash vapor are subjected to the second washing to obtain the second CO-rich 2 methanol, which is subjected to the third washing with the H 2 flash vapor to obtain the low-sulfur carbon-rich methanol; among them, the first stream of CO-rich 2 methanol, the first stream of H-rich 2 methanol, the low-H 2 methanol, and the low-sulfur carbon-rich methanol each independently return and undergo the H 2 S absorption.

[0011] The second aspect of the present invention provides a low-temperature and low-sulfur methanol washing device for a coal water slurry gasification device. The device includes: an H 2 S absorption tower, a CO 2 absorption tower, a CO 2 flash tower, an H 2 S flash tower, and a reabsorption tower, as well as a first cooler and a second cooler; the CO 2 flash tower includes a CO 2 washing section and a CO 2 flash section; the H 2 S flash tower includes an H 2 S washing section and an H 2 S flash section;

[0012] The syngas enters the H 2 S absorption tower for H 2 S absorption to obtain the desulfurized gas and the first H-rich 2 methanol; the desulfurized gas enters the CO 2 absorption tower for CO 2 absorption to obtain the first CO-rich 2 methanol, which is divided into two streams. The second stream of CO-rich2 After methanol passes through the first cooler, it enters CO 2 The flash evaporation section conducts CO 2 flash evaporation to obtain rich CO 2 methanol and CO 2 flash gas after flash evaporation; divide the first rich H 2 S methanol into two streams. The second stream of rich H 2 S methanol enters the H 2 S flash evaporation section to conduct H 2 S flash evaporation to obtain rich H 2 S methanol and H 2 S flash gas;

[0013] Feed the rich CO 2 methanol after flash evaporation into the upper part of the reabsorption tower for the first flash evaporation. The obtained semi-lean methanol is divided into three streams. The second stream of semi-lean methanol enters the middle part of the reabsorption tower for the second flash evaporation to obtain the solution after flash evaporation; Feed the rich H 2 S methanol into the lower part of the reabsorption tower for the third flash evaporation. The obtained sulfur-containing gas phase and the solution after flash evaporation are subjected to the first washing to obtain low H 2 S methanol;

[0014] Among them, divide the first stream of semi-lean methanol into two streams. The A stream of semi-lean methanol is recycled and used for CO 2 absorption tower, and the B stream of semi-lean methanol enters CO 2 washing section to conduct the second washing with CO 2 flash gas to obtain the second rich CO 2 methanol and recycle it to the H 2 S washing section to conduct the third washing with H 2 S flash gas to obtain low-sulfur rich-carbon methanol; Among them, the first stream of rich CO 2 methanol, the first stream of rich H 2 S methanol, low H 2 S methanol and low-sulfur rich-carbon methanol are each independently recycled and used for H 2 S absorption tower.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The method provided by the present invention, by optimizing the medium-pressure flash evaporation process flow, uses the B stream of semi-lean methanol to conduct series washing on the flash gas flashed out from the CO 2 flash evaporation tower and the H 2 S flash evaporation tower. The low-sulfur rich-carbon methanol generated by washing is sent to the H 2 S absorption tower to continue washing the syngas. Compared with the prior art, it reduces the H 2 S flash evaporation tower for rich CO 2The usage amount of methanol is reduced, and at the same time, the adverse impact on the generation of high-quality low-temperature cooling capacity in the reabsorption tower is reduced, which is beneficial to the reduction of the energy consumption of the device;

[0017] (2) The method provided by the present invention also optimizes the reabsorption process flow, and realizes that the flashed solution obtained by the second flash of the second semi-lean methanol is absorbed by the sulfur-containing gas phase generated by the flash of the flashed rich H 2 S methanol, so that the H 2 S content in the solution is lower, and low-H 2 S methanol is obtained; but it does not mix with the third rich H 2 S methanol after flashing;

[0018] (3) The method provided by the present invention also optimizes the H 2 S absorption process flow. By introducing low-H 2 S methanol and low-sulfur rich-carbon methanol to jointly absorb H 2 S and CO 2 in the syngas, the recycling of low-H 2 S methanol and low-sulfur rich-carbon methanol is realized, and the usage amount of the first rich CO 2 methanol is reduced, which is equivalent to reducing the first rich H 2 S methanol that needs to be thermally regenerated; in addition, by pre-absorbing CO 2 gas with low-H 2 S methanol and low-sulfur rich-carbon methanol, the working load of the subsequent CO 2 absorption tower is correspondingly reduced, which is also of positive significance for reducing the usage amounts of lean methanol and semi-lean methanol in the CO 2 absorption tower. Description of the Drawings

[0019] Figure 1 is a schematic structural diagram of a low-temperature and low-sulfur methanol washing device provided with a coal water slurry gasification device according to the present invention.

[0020] Description of the Reference Numerals

[0021] T-1, H 2 S absorption tower; T-2, CO 2 absorption tower; T-3, CO 2 flash tower; T-4, H 2 S flash tower; T-5, reabsorption tower; E-1, first cooler; E-2, second cooler; E-3, third cooler; E-4, fourth cooler; E-5, fifth cooler; P-1, first pump; P-2, second pump; P-3, third pump; P-4, fourth pump;

[0022] 1, syngas; 2, low-H 2 S methanol; 3, second rich H 2S Methanol; 4. First CO-rich 2 Methanol; 4-i. First CO-rich stream 2 Methanol; 4-ii. Second CO-rich stream 2 Methanol; 5. First H-rich 2 S Methanol; 5-i. First H-rich stream 2 S Methanol; 5-ii. Second H-rich stream 2 S Methanol; 6. Desulfurized gas; 7. CO-containing 2 Methanol; 8. Semi-lean methanol; 8-i. First semi-lean methanol stream; 8-ii. Second semi-lean methanol stream; 8-iii. Third semi-lean methanol stream; 8-i-A. A-stream semi-lean methanol; 8-i-B. B-stream semi-lean methanol; 9. Lean methanol; 10. Purified gas; 11. Low-sulfur CO-rich methanol; 12. Second CO-rich 2 Methanol; 13. H-rich after flashing 2 S Methanol; 14. CO-rich after flashing 2 Methanol; 15. Flash gas; 15-i. First flash gas stream; 15-ii. Second flash gas stream; 16. Third H-rich 2 S Methanol; 17. CO 2 Product gas. Detailed implementation manners

[0023] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0024] In the present invention, without special circumstances, "first", "second", "third", "fourth" and "fifth" neither represent the order nor limit each material or step, but are only used to distinguish that these are not the same material or step. For example, the "first", "second", "third", "fourth" and "fifth" in "first cooling", "second cooling", "third cooling", "fourth cooling" and "fifth cooling" are only used to indicate that these are not the same cooling.

[0025] In the present invention, without special circumstances, the "top" of a container refers to the 0-10% height of the container from top to bottom; the "upper part" of a container refers to the 10-40% height of the container from top to bottom; the "middle part" of a container refers to the 40-60% height of the container from top to bottom; the "lower part" of a container refers to the 60-90% height of the container from top to bottom; the "bottom" of a container refers to the 90-100% height of the container from top to bottom.

[0026] In the first aspect of the present invention, a low-temperature and low-sulfur methanol washing method for a supporting coal water slurry gasification device is provided. The method includes:

[0027] Subject the syngas to H 2 S absorption, and subject the desulfurized gas obtained to CO 2 absorption to obtain a first CO-rich 2 methanol, which is divided into two streams. The second CO-rich 2 methanol, after being cooled for the first time, undergoes CO 2 flashing to obtain flashed CO-rich 2 methanol and CO 2 flashed gas; the first H 2 S-rich methanol obtained from the H 2 S absorption is also divided into two streams. The second H 2 S-rich methanol, after being cooled for the second time, undergoes H 2 S flashing to obtain flashed H 2 S-rich methanol and H 2 S flashed gas;

[0028] Subject the flashed CO-rich 2 methanol to a first flash, and the semi-lean liquid methanol obtained is divided into three streams. The second semi-lean liquid methanol undergoes a second flash. Subject the flashed H 2 S-rich methanol to a third flash. The sulfur-containing gas phase obtained and the flashed solution obtained from the second flash are subjected to a first washing to obtain low-H 2 S methanol;

[0029] Among them, the first semi-lean liquid methanol is divided into two streams. The A-stream semi-lean liquid methanol returns and undergoes the above-mentioned CO 2 absorption; the B-stream semi-lean liquid methanol and the CO 2 flashed gas are subjected to a second washing to obtain a second CO-rich 2 methanol, which is subjected to a third washing with the H 2 S flashed gas to obtain low-sulfur carbon-rich methanol; among them, the first CO-rich 2 methanol, the first H 2 S-rich methanol, the low-H 2 S methanol, and the low-sulfur carbon-rich methanol each independently return and undergo the above-mentioned H 2 S absorption.

[0030] In some embodiments of the present invention, preferably, the H 2 S absorption includes a first H 2 S absorption and a second H 2 S absorption; among them, the process of the first H 2 S absorption includes: contacting the syngas with the first H 2 S-rich methanol and performing the first H 2S absorption to obtain a second H-rich 2 S methanol and pre-washed syngas; the second H 2 The process of S absorption includes: sequentially contacting the pre-washed syngas with low-H 2 S methanol, low-sulfur carbon-rich methanol, and a first stream of CO-rich 2 methanol and performing a second H 2 S absorption to obtain desulfurized gas and a first H-rich 2 S methanol.

[0031] In the present invention, the first H-rich 2 S methanol is divided into two streams. The first stream returns and undergoes H 2 S absorption, and the second stream undergoes H 2 S flash. Preferably, the first H-rich 2 S methanol is divided into the first stream of H-rich 2 S methanol and the second stream of H-rich 2 S methanol with a molar flow rate ratio of 1:60 - 65.

[0032] In some embodiments of the present invention, preferably, the molar content of H 2 S in the syngas is 0.9 - 1.2%, and the molar content of CO 2 is 40 - 50%; the temperature is -15 to -5 °C, and the pressure is 5.2 - 5.7 MPa(G).

[0033] In the present invention, there is a relatively wide selection range for the source of the syngas, as long as the syngas meets the above limitations. Preferably, the syngas is selected from the upstream syngas cooling process.

[0034] In some embodiments of the present invention, preferably, the molar flow rate ratio of the syngas to the first stream of H-rich 2 S methanol is 70 - 80:1.

[0035] In the present invention, the first H 2 S absorption aims to remove impurities such as HCN and NH 3 in the syngas, as well as a small amount of H 2 S and CO 2 . Preferably, the molar content of H 2 S in the second H-rich 2 S methanol is 2 - 4%, and the molar content of CO 2 is 70 - 75%.

[0036] In the present invention, the second H 2 S absorption aims to further remove H 2 S in the syngas, as well as a small amount of CO 2 . Preferably, the first H-rich2 The molar content of CO in methanol is 35 - 40%, and the molar content of H₂S is 1.2 - 1.5%; the temperature is -10 to -5 °C, and the pressure is 5.3 - 5.5 MPa(G). 2 of, and H₂S 2 S content is 1.2 - 1.5%; the temperature is -10 to -5 °C, and the pressure is 5.3 - 5.5 MPa(G).

[0037] In some embodiments of the present invention, preferably, the molar flow ratio of the low-H₂S methanol and syngas is 1:3.5 - 4.5. 2 S methanol and syngas is 1:3.5 - 4.5.

[0038] In some embodiments of the present invention, preferably, the molar flow ratio of the low-sulfur carbon-rich methanol and syngas is 1:15 - 20.

[0039] In some embodiments of the present invention, preferably, the molar flow ratio of the first CO-rich 2 methanol and syngas is 1:2 - 3.

[0040] In some embodiments of the present invention, preferably, the molar content of H₂S in the desulfurized gas is 0.5 - 1 ppm, and the molar content of CO 2 S is 0.5 - 1 ppm, and CO 2 is 35 - 38%; the temperature is -18 to -12 °C; the pressure is 5.3 - 5.4 MPa(G).

[0041] In some embodiments of the present invention, preferably, the CO 2 absorption includes a first CO 2 absorption and a second CO 2 absorption; wherein, the process of the first CO 2 absorption includes: contacting the desulfurized gas and the CO-containing 2 methanol and performing the first CO 2 absorption to obtain the first CO-rich 2 methanol and the pre-purified gas; the process of the second CO 2 absorption includes: sequentially contacting the pre-purified gas with the A-stage semi-lean methanol and the lean methanol and performing the second CO 2 absorption to obtain the purified gas and the CO-containing 2 methanol.

[0042] In the present invention, the first CO-rich 2 methanol is divided into two streams. The first stream returns and undergoes H₂S 2 absorption, and the second stream undergoes CO 2 flashing. Preferably, the first CO-rich 2 methanol is divided into the first stream of CO-rich 2 methanol and the second stream of CO-rich 2 methanol with a molar flow ratio of 1:1.8 - 2.2.

[0043] In the present invention, the first CO 2 Absorption is intended to further remove CO from sweetened gas 2 . Preferably, the first CO-rich 2 CO in methanol 2 The molar content of is 28-32%, H 2 The molar content of S is 0.1-0.5ppm; the temperature is -12 to -7℃, and the pressure is 5.2-5.4MPa(G).

[0044] In some embodiments of the present invention, preferably, the desulfurized gas and the CO 2 The molar flow ratio of methanol is 1:1.2-1.4.

[0045] In some embodiments of the present invention, preferably, the CO-containing 2 Methanol is cooled to -36 to -34°C and returned to the first CO 2 Absorb.

[0046] In some embodiments of the present invention, preferably, the molar flow ratio of the purified gas to the semi-lean methanol in the A stream is 1.4-1.6:1.

[0047] In some embodiments of the present invention, preferably, the molar flow ratio of the purified gas to lean methanol is 1:1.1-1.2; further preferably, H 2 S molar content <0.1ppm, CO 2 Mole content <20ppm; temperature is -55 to -50℃, pressure is 5.2-5.3MPa(G).

[0048] In the present invention, the first cooling is performed by reducing the second stream of CO-rich 2 The temperature of methanol is to reduce the total amount of medium-pressure flash gas and lay the foundation for the reabsorption tower to obtain low temperature (high-quality cooling capacity). Preferably, the temperature of the first cooled material is -36 to -34°C.

[0049] In some embodiments of the present invention, preferably, the CO 2 The flash evaporation pressure is 1.6-2MPa(G); further preferably, the flash evaporation is CO-rich 2 H in methanol 2 The molar content of S is 0.1-0.5ppm, CO 2 The molar content of is 27.5-31.5%; the temperature is -36.5 to -34.5℃.

[0050] In the present invention, the second cooling is performed by reducing the second H-rich 2 ​​​​The temperature of the methanol is to reduce the total amount of medium-pressure flash gas and at the same time lay a foundation for obtaining low temperature (high-quality cold energy) for the reabsorption tower. Preferably, the temperature of the material after the second cooling is -33 to -30 °C.

[0051] In some embodiments of the present invention, preferably, the 2 pressure of the H 2 S flash is 1.6 - 2 MPa(G); further preferably, the molar content of H 2 S in the flashed rich H 2 S methanol is 1.2 - 1.4%, and the molar content of CO

[0052] is 34.5 - 39.5%; the temperature is -33.5 to -30.5 °C.

[0053] In some embodiments of the present invention, preferably, the pressure of the first flash < the pressure of the second flash < the pressure of the third flash; further preferably, the pressure of the first flash is 0.05 - 0.08 MPa(G), the pressure of the second flash is 0.06 - 0.09 MPa(G), and the pressure of the third flash is 0.12 - 0.16 MPa(G).

[0054] In some embodiments of the present invention, preferably, the process of the first flash includes: subjecting the flashed rich CO 2 methanol to the first flash to obtain the semi-lean methanol and the first CO 2 product gas; the process of the second flash includes: subjecting the second stream of semi-lean methanol to the second flash to obtain the flashed solution and the second CO 2 product gas; the process of the third flash includes: subjecting the flashed rich H 2 S methanol to the third flash to obtain the third rich H 2 S methanol and the sulfur-containing gas phase; wherein, subjecting the sulfur-containing gas phase and the flashed solution to the first washing to obtain the low H 2 S methanol and the third CO 2 product gas, and mixing the first CO 2 product gas, the second CO 2 product gas and the third CO 2 product gas to obtain the CO 2 product gas.

[0055] In some embodiments of the present invention, preferably, the semi-lean methanol is divided into a first stream of semi-lean methanol, a second stream of semi-lean methanol, and a third stream of semi-lean methanol with a molar flow ratio of 2 - 2.5:1 - 1.2:1.In some embodiments of the present invention, further preferably, the first semi-lean methanol is divided into the A-share semi-lean methanol and the B-share semi-lean methanol with a molar flow ratio of 9-11:1.

[0056] In some embodiments of the present invention, preferably, the CO 2 molar content in the semi-lean methanol is 20-23%, and the H 2 molar content of S is ≤0.5 ppm; the temperature is -65 to -60 °C; the pressure is 0.05-0.08 MPa(G).

[0057] In some embodiments of the present invention, preferably, the H 2 molar content of S in the low-H 2 S methanol is 0.5-0.9%, and the CO 2 molar content is 20-25%; the temperature is -62 to -58 °C, and the pressure is 0.12-0.16 MPa(G).

[0058] In some embodiments of the present invention, preferably, the H 2 molar content of S in the third H 2 S-rich methanol is 1.2-1.4%, and the CO 2 molar content is 24-28%; the temperature is -68 to -64 °C; the pressure is 0.13-0.17 MPa(G).

[0059] In some embodiments of the present invention, preferably, the H 2 molar content of S in the product gas is <1 ppm, and the CO 2 molar content is 99.4-99.7%; the temperature is -65 °C to -60 °C, and the pressure is 0.05-0.08 MPa(G). 2

[0060] In some embodiments of the present invention, preferably, the process of the second washing includes: subjecting the B-share semi-lean methanol and the CO 2 flash gas to a second washing to obtain the second CO 2 rich methanol and the first flash gas.

[0061] In some embodiments of the present invention, preferably, the H 2 molar content of S in the second CO 2 rich methanol is 0.1-0.5 ppm, and the CO 2 molar content is 24-28%; the temperature is -52 to -48 °C.

[0062] In some embodiments of the present invention, preferably, the process of the third washing includes: subjecting the second CO 2Methanol and H 2 The first flash vapor and the H 2 S flash vapor are subjected to a third washing to obtain the low-sulfur carbon-rich methanol and a second flash vapor; further preferably, the molar content of H 2 S in the low-sulfur carbon-rich methanol is <0.1%, and the molar content of CO

[0063] In some embodiments of the present invention, preferably, the first flash vapor and the second flash vapor are mixed to obtain a flash vapor with a temperature of -52°C to -48°C and a pressure of 1.6 - 2 MPa(G).

[0064] In some embodiments of the present invention, preferably, the low-H 2 S methanol is first pressurized to 5.8 - 6 MPa(G) and then returned for the H 2 S absorption.

[0065] In some embodiments of the present invention, preferably, in the direction of material flow, the first CO-rich 2 methanol is sequentially pressurized to 5.8 - 6 MPa(G) for the second time and cooled to -35°C to -25°C for the third time, and then returned for the H 2 S absorption.

[0066] In some embodiments of the present invention, preferably, the CO-rich 2 methanol after flashing is cooled to -42°C to -38°C for the fifth time and then subjected to the first flashing.

[0067] In some embodiments of the present invention, preferably, the first semi-lean liquid methanol is pressurized to 5.6 - 5.8 MPa(G) for the third time and then divided into two streams, which are respectively returned for the CO 2 absorption and the second washing.

[0068] In some embodiments of the present invention, preferably, the low-sulfur carbon-rich methanol is pressurized to 5.6 - 5.8 MPa(G) for the fourth time and then returned for the H 2 S absorption.

[0069] The second aspect of the present invention provides a structural schematic diagram of a low-temperature and low-sulfur methanol washing device for a coal water slurry gasification device as shown in Figure 1 shown, and it can be seen from Figure 1 that the device includes: connected H 2 S absorption tower T-1, CO 2 absorption tower T-2, CO 2 flash tower T-3, H 2 S flash tower T-4 and reabsorption tower T-5, as well as the first cooler E-1 and the second cooler E-2; CO2 The flash tower T-3 includes: CO provided thereon 2 washing section and CO 2 flash section; H 2 The H2S flash tower T-4 includes: H2S provided thereon 2 washing section and H2S 2 flash section;

[0070] The syngas 1 enters the H2S 2 absorption tower T-1 for H2S 2 absorption to obtain the desulfurized gas 6 and the first rich H2S 2 methanol 5; The desulfurized gas 6 enters the CO 2 absorption tower T-2 for CO 2 absorption to obtain the first rich CO 2 methanol 4 is divided into two streams, and the second rich CO 2 methanol 4-ii, after passing through the first cooler E-1, enters the CO 2 flash section for CO 2 flashing to obtain the flashed rich CO 2 methanol 14 and CO 2 flashed gas; The first rich H2S 2 methanol 5 is divided into two streams, and the second rich H2S 2 methanol 5-ii, after passing through the second cooler E-2, enters the H2S 2 flash section for H2S 2 flashing to obtain the flashed rich H2S 2 methanol 13 and H2S 2 flashed gas;

[0071] The flashed rich CO 2 methanol 14 enters the upper part of the reabsorption tower T-5 for the first flashing to obtain the semi-lean liquid methanol 8 which is divided into three streams. The second semi-lean liquid methanol 8-ii enters the middle part of the reabsorption tower T-5 for the second flashing to obtain the flashed solution; The flashed rich H2S 2 methanol 13 enters the lower part of the reabsorption tower T-5 for the third flashing. The obtained sulfur-containing gas phase and the flashed solution are subjected to the first washing to obtain the low H2S 2 methanol 2;

[0072] Among them, the first semi-lean liquid methanol 8-i is divided into two streams. The A stream of semi-lean liquid methanol 8-i-A is recycled to the CO 2 absorption tower T-2, and the B stream of semi-lean liquid methanol 8-i-B enters the CO 2 washing section to carry out the second washing with the CO 2 flashed gas to obtain the second rich CO 2 methanol 12 is recycled to the H2S 2 washing section to carry out the washing with the H2S 2The S flash gas is subjected to a third washing to obtain low-sulfur, carbon-rich methanol 11;

[0073] Among them, the first rich CO 2 methanol 4-i, the first rich H 2 S methanol 5-i, low H 2 S methanol 2, and low-sulfur, carbon-rich methanol 11 are each independently recycled and reused in the H 2 S absorption tower T-1.

[0074] In the present invention, as Figure 1 shown, the H 2 S absorption tower T-1 includes a first H 2 S absorption section provided below and a second H 2 S absorption section provided above.

[0075] In the present invention, as Figure 1 shown, the first rich H 2 S methanol 5-i is recycled and reused in the first H 2 S absorption section; the first rich CO 2 methanol 4-i, low H 2 S methanol 2, and low-sulfur, carbon-rich methanol 11 are each independently recycled and reused in the second H 2 S absorption section.

[0076] In the present invention, as Figure 1 shown, the first H 2 S absorption section and the second H 2 S absorption section are connected by riser holes; the first H 2 S absorption section is connected to the first rich H 2 S methanol outlet of the second H 2 S absorption section for contacting the syngas 1 with the first rich H 2 S methanol 5-i and performing the first H 2 S absorption to obtain the second rich H 2 S methanol 3 and the pre-washed syngas; the second H 2 S absorption section is connected to the low H 2 S methanol outlet of the reabsorption tower T-5, the low-sulfur, carbon-rich methanol outlet of the H 2 S washing section, and the rich CO 2 methanol outlet of the CO 2 absorption tower T-2 for sequentially contacting the pre-washed syngas with low H 2 S methanol 2, low-sulfur, carbon-rich methanol 11, and the first rich CO 2 methanol 4-i and performing the second H 2 S absorption to obtain the desulfurized gas 6 and the first rich H 2 S methanol 5.

[0077] In some embodiments of the present invention, preferably, the H 2 In the S absorption tower T-1, the number of trays in the first H 2 S absorption section is 9 - 12 trays, and the number of trays in the second H 2 S absorption section is 60 - 80 trays.

[0078] In the present invention, without special instructions, in the first H 2 S absorption section, the contact mode between the syngas and the first rich H 2 S methanol 5-i is preferably countercurrent contact between the syngas 1 and the first rich H 2 S methanol 5-i, that is, the syngas 1 enters from the bottom of the first H 2 S absorption section, and the first rich H 2 S methanol 5-i enters from the upper part of the first H 2 S absorption section.

[0079] In the present invention, as Figure 1 shown, the CO 2 absorption tower T-2 includes a first CO 2 absorption section arranged at the bottom and a second CO 2 absorption section arranged at the top, and the bottom of the second CO 2 absorption section is connected to the upper part of the first CO 2 absorption section.

[0080] In the present invention, as Figure 1 shown, the A-share semi-lean liquid methanol (8-i-A) is recycled and used in the second CO 2 absorption section.

[0081] In the present invention, as Figure 1 shown, the first CO 2 absorption section and the second CO 2 absorption section are connected by lifting holes. Among them, the upper part of the first CO 2 absorption section is connected to the lower part of the second CO 2 absorption section, which is used to contact the desulfurized gas 6 with the CO 2 -containing methanol 7 and carry out the first CO 2 absorption to obtain the first rich CO 2 -containing methanol 4 and the pre-purified gas; the second CO 2 absorption section is connected to the semi-lean liquid methanol outlet of the reabsorption tower T-5 and the lean methanol 9 from the subsequent process, which is used to contact the pre-purified gas with the A-share semi-lean liquid methanol 8-i-A and the lean methanol 9 in sequence and carry out the second CO 2 absorption to obtain the purified gas 10 and the CO 2 -containing methanol 7.

[0082] In some embodiments of the present invention, preferably, the CO 2 absorption tower T-2, the number of trays in the first CO 2 absorption section is 12 - 18 trays, and the number of trays in the second CO 2 absorption section is 60 - 80 trays.

[0083] In the present invention, without special instructions, the CO 2 absorption tower T-2, in the first CO 2 absorption section, the contact mode between the desulfurized gas 6 and the CO 2 methanol 7 is preferably countercurrent contact between the desulfurized gas 6 and the CO 2 methanol 7; that is, the desulfurized gas 6 enters from the bottom of the first CO 2 absorption section, and the CO 2 methanol 7 enters from the upper part of the first CO 2 absorption section.

[0084] In the present invention, as Figure 1 shown, the CO 2 flash tower T-3 includes a CO 2 washing section provided above and a CO 2 flash section provided below, wherein the CO 2 flash section is used to flash the second rich CO 2 methanol 4-ii after the first cooling to obtain the flashed rich CO 2 methanol 14 and CO 2 flash gas; the CO 2 washing section is used to second-wash the B-stream semi-lean liquid methanol and the CO 2 flash gas to obtain the second rich CO 2 methanol 12 and the first flash gas 15-i. In the present invention, the CO 2 washing section and the CO 2 flash section are connected through lifting holes. 2

[0085] In the present invention, as Figure 1 shown, the H 2 S flash tower T-4 includes an H 2 S washing section provided above and an H 2 S flash section provided below, wherein the H 2 S flash section is used to flash the second rich H 2 S methanol 5-ii after the second cooling to obtain the flashed rich H 2 S methanol 13 and H 2 S flash gas; the H 2 S washing section is used to second-wash the second rich CO 2 methanol 12 and H 2 methanol 12 and Hmethanol 12 and H2 The flashed vapor is subjected to a third washing to obtain low-sulfur carbon-rich methanol 11 and a second flashed vapor 15-ii. In the present invention, H 2 The H 2 washing section and the H

[0086] In the present invention, as Figure 1 shown, the upper and middle parts of the reabsorption tower T-5 are connected through riser holes, and the middle and lower parts are also connected through riser holes. Specifically, the upper part is used for subjecting the flashed CO 2 -rich methanol 14 to a first flash to obtain semi-lean methanol 8 and a first CO 2 product gas; the middle part is used for subjecting the second semi-lean methanol 8-ii to a second flash to obtain a flashed solution and a second CO 2 product gas; the lower part is used for subjecting the flashed H 2 -rich methanol 13 to a third flash to obtain third H 2 -rich methanol 16 and a sulfur-containing gas phase; wherein, the sulfur-containing gas phase and the flashed solution are washed to obtain low-H 2 -sulfur methanol 2 and a third CO 2 product gas; the CO 2 product gas 17 includes the first CO 2 product gas, the second CO 2 product gas, and the third CO 2 product gas.

[0087] In the present invention, as Figure 1 shown, a first pump P-1 is provided on the pipeline connecting the low-H 2 -sulfur methanol outlet of the reabsorption tower T-5 and the second H 2 -sulfur absorption section, and is used for recycling the low-H 2 -sulfur methanol 2 to the second H 2 -sulfur absorption section after first pressurization.

[0088] In the present invention, as Figure 1 shown, in the direction of material flow, a second pump P-2 and a third cooler E-3 are successively provided on the pipeline connecting the first CO 2 -rich methanol outlet of the CO 2 absorption tower T-2 and the second H 2 -sulfur absorption section, and are used for recycling the first stream of CO 2 -rich methanol 4-i to the second H 2 -sulfur absorption section after second pressurization and third cooling.

[0089] In the present invention, as Figure 1 shown, on the pipeline connecting the semi-lean methanol outlet of the reabsorption tower T-5, the second CO 2 absorption section, and CO2 There is a third pump P-3 installed on the pipeline of the washing section, which is used to divide the first semi-lean methanol 8-i into two streams after being pressurized by the third stage, and recycle them back to the second CO 2 absorption section and CO 2 washing section respectively.

[0090] In the present invention, as Figure 1 shown, there is a fourth pump P-4 installed on the pipeline connecting the second H 2 S absorption section and the H 2 S flash section, which is used to recycle the second stream of rich H 2 S methanol 5-ii back to the H 2 S flash section after being pressurized by the fourth stage.

[0091] In the present invention, as Figure 1 shown, there is a fourth cooler E-4 installed on the pipeline connecting the second CO 2 absorption section and the first CO 2 absorption section, which is used to recycle the CO 2 -containing methanol back to the first CO 2 absorption section after being cooled by the fourth stage.

[0092] In the present invention, as Figure 1 shown, there is a fifth cooler E-5 installed on the pipeline connecting the CO 2 flash section and the upper part of the reabsorption tower T-5, which is used to perform the first flash on the flashed rich CO 2 -containing methanol 14 after being cooled by the fifth stage.

[0093] The present invention will be described in detail below through embodiments.

[0094] Embodiment 1

[0095] The low-temperature and low-sulfur methanol washing device for the supporting water coal slurry gasification device is as Figure 1 shown. It can be seen from Figure 1 that this device includes: H 2 S absorption tower T-1, CO 2 absorption tower T-2, CO 2 flash tower T-3, H 2 S flash tower T-4 and reabsorption tower T-5, first cooler E-1, second cooler E-2, third cooler E-3, fourth cooler E-4 and fifth cooler E-5, as well as first pump P-1, second pump P-2, third pump P-3 and fourth pump P-4;

[0096] H 2 S absorption tower T-1 includes a first H 2 S absorption section arranged at the lower part and a second H 2 S absorption section arranged at the upper part; CO2 The absorption tower T-2 includes a first CO2 absorption section provided at the lower part 2 and a second CO2 absorption section provided at the upper part 2 ; CO2 2 The flash tower T-3 includes a CO2 flash section provided at the lower part 2 and a CO2 scrubbing section provided at the upper part 2 ; H2S 2 The H2S flash tower T-3 includes an H2S flash section provided at the lower part 2 and an H2S scrubbing section provided at the upper part 2 ; H2S scrubbing section.

[0097] A low-temperature and low-sulfur methanol scrubbing method for a coal water slurry gasification device, the method comprising:

[0098] Contacting syngas 1 (the molar content of H2S is 0.9 - 1.2%, the molar content of CO2 is 40 - 50%; the temperature is -15 to -5 °C, the pressure is 5.2 - 5.7 MPa(G)) and the first rich H2S methanol 5-i countercurrently at a molar flow ratio of 70 - 80:1 and performing the first H2S 2 absorption to obtain the second rich H2S methanol 3 (the molar content of H2S is 2 - 4%, the molar content of CO2 is 70 - 75%) and the pre-scrubbed syngas; 2 2 2 2 2 2

[0099] Sequentially contacting the pre-scrubbed syngas with low-H2S methanol 2 (pressurized to 5.8 - 6 MPa(G) for the first time), low-sulfur rich-carbon methanol 11 (pressurized to 5.8 - 6 MPa(G) for the fourth time) and the first rich CO2 methanol 4-i (pressurized to 5.8 - 6 MPa(G) for the second time and cooled to -35 to -25 °C for the third time) countercurrently and performing the second H2S 2 2 absorption to obtain the desulfurized gas 6 (the molar content of H2S is 0.5 - 1 ppm, the molar content of CO2 is 36 - 40%; the temperature is -20 to -10 °C; the pressure is 5.3 - 5.4 MPa(G)) and the first rich H2S methanol 5 (the molar content of CO2 is 35 - 40%, the molar content of H2S is 1.2 - 1.5%; the temperature is -10 to -5 °C, the pressure is 5.3 - 5.5 MPa(G)); 2 2 2 2 2 2

[0100] Among them, syngas 1 and low-H2S 2 ​​​​​​​​​​​​​The molar flow rate ratio of methanol 2 is 3.5 - 4.5:1; the molar flow rate ratio of syngas 1 and low-sulfur carbon-rich methanol 11 is 15 - 20:1; the molar flow rate ratio of syngas 1 and the first stream of CO-rich 2 methanol 4-i is 2 - 3:1;

[0101] The above desulfurized gas 6 and CO-containing 2 methanol 7 (cooled to -36 to -34 °C in the fourth stage) are in countercurrent contact at a molar flow rate ratio of 1:1.2 - 1.4 and undergo the first CO 2 absorption to obtain the first CO-rich 2 methanol 4 (the molar content of CO 2 is 28 - 32%, the molar content of H 2 S is 0.1 - 0.5 ppm; the temperature is -12 to -7 °C, and the pressure is 5.2 - 5.4 MPa(G)) and pre-purified gas. Among them, the first CO-rich 2 methanol 4 is divided into the first stream of CO-rich 2 methanol 4-i and the second stream of CO-rich 2 methanol 4-ii with a molar flow rate ratio of 1:1.8 - 2.2;

[0102] The above pre-purified gas is successively in countercurrent contact with A-stage semi-lean methanol 8-i-A and lean methanol 9 (the molar content of CO 2 is 0%, the molar content of H 2 S is 0%) and undergoes the second CO 2 absorption to obtain purified gas 10 (the molar content of H 2 S < 0.1 ppm, the molar content of CO 2 < 20 ppm; the temperature is -55 to -50 °C; the pressure is 5.2 - 5.3 MPa(G)) and CO-containing 2 methanol 7;

[0103] Among them, the molar flow rate ratio of the above purified gas 10 and A-stage semi-lean methanol 8-i-A is 1.4 - 1.6:1; the molar flow rate ratio of the above purified gas 10 and lean methanol 9 is 1:1.1 - 1.2;

[0104] After the above second stream of CO-rich 2 methanol 4-ii is cooled to -36 to -34 °C in the first stage, it undergoes CO 2 flashing (the pressure is 1.6 - 2 MPa(G)) to obtain the flashed CO-rich 2 methanol 14 (the molar content of H 2 S is 0.1 - 0.5 ppm, the molar content of CO 2 is 27.5 - 31.5%; the temperature is -36.5 to -34.5 °C) and CO 2 flashed gas; the above second stream of H-rich2 After the methanol - 5 - ii is cooled to - 33 to - 30 °C for the second time, H 2 is subjected to flash evaporation (at a pressure of 1.6 - 2 MPa(G)) to obtain the H - rich methanol - 13 after flash evaporation 2 (H 2 with a molar content of 1.2 - 1.4%, and CO 2 with a molar content of 34.5 - 39.5%; at a temperature of - 33.5 to - 30.5 °C) and H 2 flash vapor;

[0105] After the above - mentioned H - rich CO 2 methanol - 14 is cooled to - 42 to - 38 °C for the fifth time, it is subjected to the first flash evaporation (at a pressure of 0.05 - 0.08 MPa(G)) to obtain the first CO 2 product gas and semi - lean methanol - 8 (CO 2 with a molar content of 18 - 22%, and H 2 with a molar content of ≤0.5 ppm; at a temperature of - 64 to - 61 °C; at a pressure of 0.05 - 0.08 MPa(G)), where the above - mentioned semi - lean methanol - 8 is divided into the first semi - lean methanol - 8 - i, the second semi - lean methanol - 8 - ii, and the third semi - lean methanol - 8 - iii with a molar flow ratio of 2 - 2.5:1 - 1.2:1; the second semi - lean methanol - 8 - ii is subjected to the second flash evaporation (at a pressure of 0.06 - 0.09 MPa(G)) to obtain the second CO 2 product gas and the solution after flash evaporation; the above - mentioned H - rich H 2 S methanol - 13 is subjected to the third flash evaporation (at a pressure of 0.12 - 0.16 MPa(G)) to obtain a sulfur - containing gas phase and the third H - rich H 2 S methanol - 16 (H 2 with a molar content of 1.2 - 1.4%, and CO 2 with a molar content of 24 - 28%; at a temperature of - 68 to - 64 °C; at a pressure of 0.13 - 0.17 MPa(G)); the above - mentioned sulfur - containing gas phase and the solution after flash evaporation are subjected to the first washing to obtain the third CO 2 product gas and low - H 2 S methanol - 2 (H 2 with a molar content of 0.5 - 0.9%, and CO 2 with a molar content of 20 - 25%; at a temperature of - 62 to - 58 °C, at a pressure of 0.12 - 0.16 MPa(G));

[0106] Among them, the above - mentioned first CO 2 product gas, the second CO 2 product gas, and the third CO 2 product gas are mixed to obtain the CO 2 product gas - 17 (H2 The molar content of S < 1 ppm, CO 2 The molar content is 99.4 - 99.7%; the temperature is -65°C to -60°C, and the pressure is 0.05 - 0.08 MPa(G));

[0107] Among them, after the first semi-lean methanol 8-i is pressurized to 5.6 - 5.8 MPa(G) through the third stage, it is divided into A-stream semi-lean methanol 8-i-A and B-stream semi-lean methanol 8-i-B with a molar flow ratio of 9 - 11:1. The A-stream semi-lean methanol 8-i-A is returned and undergoes the above-mentioned second CO 2 absorption, and the B-stream semi-lean methanol 8-i-B and CO 2 flash gas are subjected to the second washing to obtain the second CO-rich methanol 12(H 2 The molar content of S is 0.1 - 0.5 ppm, CO 2 The molar content is 24 - 28%; the temperature is -52 to -48°C) and the first flash gas 15-i; the above-mentioned second CO-rich methanol 2 12 and H 2 S flash gas are subjected to the third washing to obtain the above-mentioned low-sulfur CO-rich methanol 11(H 2 The molar content of S < 0.1%, CO 2 The molar content is 27 - 30%; the temperature is -43 to -40°C) and the second flash gas 15-ii; 2 Mix the above-mentioned first flash gas 15-i and the second flash gas 15-ii to obtain the flash gas 15 with a temperature of -52°C to -48°C and a pressure of 1.6 - 2 MPa(G).

[0108] Mix the above-mentioned first flash gas 15-i and the second flash gas 15-ii to obtain the flash gas 15 with a temperature of -52°C to -48°C and a pressure of 1.6 - 2 MPa(G).

[0109] Comparative Example 1

[0110] Taking a hydrogen production device using coal water slurry gasification for gas production as an example, the effective gas (H 2 +CO) entering the low-temperature methanol washing device is 230,000 Nm 3 / h. Based on this benchmark, the main technical parameters of the lean-semi-lean liquid process (i.e., CN201110260570.0 discloses a low-temperature methanol washing process) are compared in Table 1.

[0111] Table 1

[0112]

[0113] As can be seen from the results in Table 1, taking the hydrogen production unit based on coal water slurry gasification as an example, for the low-temperature and low-sulfur methanol washing method for the supporting coal water slurry gasification unit provided in Example 1, the lean methanol circulation rate is 92.6% of the lean methanol circulation rate in Comparative Example 1 (lean liquid - semi-lean liquid process), and the semi-lean methanol circulation rate is 95.7% of the semi-lean methanol circulation rate in Comparative Example 1 (lean liquid - semi-lean liquid process). The H 2 S absorption tower's rich CO 2 methanol usage is 78.9% of the rich CO 2 methanol usage in Comparative Example 1 (lean liquid - semi-lean liquid process), and the cumulative reduction in external cooling consumption is 500 KW / h, with a significant overall energy-saving effect.

[0114] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A low-temperature, low-sulfur methanol washing method for a water-coal slurry gasification device, characterized in that: The method comprises: The synthesis gas is subjected to H2S absorption, and the obtained desulfurized gas is subjected to CO2 absorption to obtain a first CO2-rich methanol divided into two streams, and the second CO2-rich methanol is subjected to CO2 flash distillation after a first cooling to obtain CO2-rich methanol after flash distillation and CO2 flash gas; the first H2S-rich methanol obtained by the H2S absorption is divided into two streams, and the second H2S-rich methanol is subjected to H2S flash distillation after a second cooling to obtain H2S-rich methanol after flash distillation and H2S flash gas; The flashed CO2-rich methanol is subjected to a first flash, and the obtained semi-lean liquid methanol is divided into three streams, the second stream of the semi-lean liquid methanol is subjected to a second flash, the flashed H2S-rich methanol is subjected to a third flash, and the obtained sulfur-containing gas phase and the flashed solution obtained by the second flash are subjected to a first washing to obtain low-H2S methanol; The first stream of semi-lean methanol is divided into two streams, and stream A of the semi-lean methanol is returned and subjected to the CO2 absorption; stream B of the semi-lean methanol is subjected to a second washing with the CO2 flash gas, and the obtained second CO2-rich methanol is subjected to a third washing with the H2S flash gas to obtain low-sulfur and carbon-rich methanol; the first stream of CO2-rich methanol, the first stream of H2S-rich methanol, the low H2S methanol and the low-sulfur and carbon-rich methanol are each independently returned and subjected to the H2S absorption.

2. The method according to claim 1, wherein: The H2S absorption includes a first H2S absorption and a second H2S absorption; The first H2S absorption process includes: contacting the synthesis gas with the first stream of H2S-rich methanol and performing a first H2S absorption to obtain a second H2S-rich methanol and a pre-washed synthesis gas; the second H2S absorption process includes: contacting the pre-washed synthesis gas with low H2S methanol, low-sulfur carbon-rich methanol and the first stream of CO2-rich methanol in sequence and performing a second H2S absorption to obtain a desulfurized gas and a first H2S-rich methanol; and / or, dividing the first H2S-rich methanol into the first stream of H2S-rich methanol and the second stream of H2S-rich methanol at a molar flow ratio of 1:60-65; and / or, the molar content of H2S in the synthesis gas is 0.9-1.2%, the molar content of CO2 is 40-50%; the temperature is -15 to -5°C, and the pressure is 5.2-5.7MPa(G); and / or, the molar flow ratio of the synthesis gas to the first stream of H2S-rich methanol is 70-80:1; and / or, the molar content of CO2 in the first H2S-rich methanol is 35-40%, the molar content of H2S is 1.2-1.5%; the temperature is -10 to -5°C, and the pressure is 5.3-5.5MPa(G); and / or, the molar flow ratio of the low H2S methanol to the synthesis gas is 1:3.5-4.5; and / or, the molar flow ratio of the low-sulfur and carbon-rich methanol to the synthesis gas is 1:15-20; and / or, the molar flow ratio of the first stream of CO2-rich methanol to the synthesis gas is 1:2-3; And / or, the molar content of H2S in the desulfurized gas is 0.5-1 ppm, the molar content of CO2 is 35-38%; the temperature is -18 to -12°C; and the pressure is 5.3-5.4 MPa(G).

3. The method according to claim 1 or 2, wherein: The CO2 absorption includes a first CO2 absorption and a second CO2 absorption; The first CO2 absorption process includes: contacting the desulfurized gas with CO2-containing methanol and performing a first CO2 absorption to obtain the first CO2-rich methanol and pre-purified gas; the second CO2 absorption process includes: contacting the pre-purified gas with A-share semi-lean liquid methanol and lean methanol in sequence and performing a second CO2 absorption to obtain purified gas and CO2-containing methanol; and / or, dividing the first CO2-rich methanol into the first CO2-rich methanol and the second CO2-rich methanol at a molar flow ratio of 1:1.8-2.2; and / or, the molar content of CO2 in the first CO2-rich methanol is 28-32%, the molar content of H2S is 0.1-0.5 ppm; the temperature is -12 to -7°C, and the pressure is 5.2-5.4 MPa(G); and / or, the molar flow ratio of the desulfurized gas to the CO2-containing methanol is 1:1.2-1.4; and / or, the CO2-containing methanol is cooled to -36 to -34°C for the fourth time and then returned to the first CO2 absorption process; and / or, the molar flow ratio of the purified gas to the A-stream semi-lean methanol is 1.4-1.6:1; and / or, the molar flow ratio of the purified gas to lean methanol is 1:1.1-1.2; And / or, the molar content of H2S in the purified gas is less than 0.1 ppm, and the molar content of CO2 is less than 20 ppm; the temperature is -55 to -50°C, and the pressure is 5.2-5.3 MPa(G).

4. The method according to any one of claims 1 to 3, wherein: The temperature of the material after the first cooling is -36 to -34°C; And / or, the pressure of the CO2 flash evaporation is 1.6-2MPa(G); and / or, the molar content of H2S in the CO2-rich methanol after the flash evaporation is 0.1-0.5 ppm, the molar content of CO2 is 27.5-31.5%; the temperature is -36.5 to -34.5°C; And / or, the temperature of the second cooled material is -33 to -30°C; And / or, the pressure of the H2S flash evaporation is 1.6-2MPa(G); And / or, the molar content of H2S in the H2S-rich methanol after the flash evaporation is 1.2-1.4%, the molar content of CO2 is 34.5-39.5%; the temperature is -33.5 to -30.5°C.

5. The method according to any one of claims 1 to 4, wherein: The pressure of the first flash vaporization is less than the pressure of the second flash vaporization and less than the pressure of the third flash vaporization; and / or, the pressure of the first flash evaporation is 0.05-0.08 MPa(G), the pressure of the second flash evaporation is 0.06-0.09 MPa(G), and the pressure of the third flash evaporation is 0.12-0.16 MPa(G); And / or, the first flash evaporation process includes: performing a first flash evaporation on the flashed CO2-rich methanol to obtain the semi-lean liquid methanol and the first CO2 product gas; the second flash evaporation process includes: performing a second flash evaporation on the second stream of semi-lean liquid methanol to obtain a flashed solution and a second CO2 product gas; the third flash evaporation process includes: performing a third flash evaporation on the flashed H2S-rich methanol to obtain a third H2S-rich methanol and a sulfur-containing gas phase; wherein the sulfur-containing gas phase and the flashed solution are first washed to obtain low-H2S methanol and a third CO2 product gas, and the first CO2 product gas, the second CO2 product gas and the third CO2 product gas are mixed to obtain a CO2 product gas; and / or, dividing the semi-lean methanol into a first stream of semi-lean methanol, a second stream of semi-lean methanol and a third stream of semi-lean methanol with a molar flow ratio of 2-2.5:1-1.2:1; and / or, dividing the first stream of semi-lean methanol into the A stream of semi-lean methanol and the B stream of semi-lean methanol with a molar flow ratio of 9-11:1; and / or, the molar content of CO2 in the semi-lean methanol is 20-23%, the molar content of H2S is ≤0.5ppm; the temperature is -65 to -60°C; the pressure is 0.05-0.08MPa(G); and / or, the molar content of H2S in the low H2S methanol is 0.5-0.9%, the molar content of CO2 is 20-25%; the temperature is -62 to -58°C, and the pressure is 0.12-0.16MPa(G); and / or, the molar content of H2S in the third H2S-rich methanol is 1.2-1.4%, the molar content of CO2 is 24-28%; the temperature is -68 to -64°C; the pressure is 0.13-0.17 MPa(G); And / or, the molar content of H2S in the CO2 product gas is less than 1ppm, the molar content of CO2 is 99.4-99.7%; the temperature is -65°C to -60°C, and the pressure is 0.05-0.08MPa(G).

6. The method according to any one of claims 1 to 5, wherein: The second washing process includes: performing a second washing on the B stream of semi-lean methanol and CO2 flash gas to obtain a second CO2-rich methanol and a first stream of flash gas; and / or, the molar content of H2S in the second CO2-enriched methanol is 0.1-0.5 ppm, the molar content of CO2 is 24-28%; the temperature is -52 to -48°C; And / or, the third washing process includes: performing a third washing on the second CO2-rich methanol and H2S flash gas to obtain the low-sulfur carbon-rich methanol and the second flash gas; and / or, the molar content of H2S in the low-sulfur, carbon-rich methanol is <0.1%, the molar content of CO2 is 27-30%; the temperature is -43 to -40°C; Preferably, the first flash gas and the second flash gas are mixed to obtain a flash gas having a temperature of -52°C to -48°C and a pressure of 1.6-2 MPa(G).

7. The method according to any one of claims 1 to 6, wherein: After the low H2S methanol is first pressurized to 5.8-6 MPa(G), it is returned and subjected to the H2S absorption; And / or, according to the material flow direction, the first stream of CO2-rich methanol is successively pressurized to 5.8-6 MPa(G) and cooled to -35 to -25°C, and then returned to perform the H2S absorption; and / or, the CO2-rich methanol after the flash is subjected to a fifth cooling to -42 to -38°C before the first flash; and / or, the first stream of semi-lean methanol is pressurized to 5.6-5.8 MPa(G) for the third time and then divided into two streams, which are returned to perform the CO2 absorption and the second washing respectively; And / or, the low-sulfur, carbon-rich methanol is pressurized to 5.6-5.8 MPa (G) for the fourth time and then returned to perform the H2S absorption.

8. A low-temperature, low-sulfur methanol washing device supporting a water-coal slurry gasification device, characterized in that: The device comprises: a connected H2S absorption tower, a CO2 absorption tower, a CO2 flash tower, an H2S flash tower and a reabsorption tower, as well as a first cooler and a second cooler; the CO2 flash tower comprises a CO2 washing section and a CO2 flash section arranged on the top; the H2S flash tower comprises an H2S washing section and an H2S flash section arranged on the top; The synthesis gas enters the H2S absorption tower to absorb H2S, and obtains desulfurized gas and the first H2S-rich methanol; the desulfurized gas enters the CO2 absorption tower to absorb CO2, and the obtained first CO2-rich methanol is divided into two streams, and the second stream of CO2-rich methanol passes through the first cooler and enters the CO2 flash section to flash CO2 to obtain flashed CO2-rich methanol and CO2 flash gas; the first H2S-rich methanol is divided into two streams, and the second stream of H2S-rich methanol passes through the second cooler and enters the H2S flash section to flash H2S to obtain flashed H2S-rich methanol and H2S flash gas; The CO2-rich methanol after flashing is fed into the upper part of the reabsorption tower for the first flashing, and the semi-lean liquid methanol obtained is divided into three streams, and the second stream of semi-lean liquid methanol is fed into the middle part of the reabsorption tower for the second flashing to obtain a flashed solution; the H2S-rich methanol after flashing is fed into the lower part of the reabsorption tower for the third flashing, and the obtained sulfur-containing gas phase and the flashed solution are first washed to obtain low-H2S methanol; The first stream of semi-lean methanol is divided into two streams, stream A of the semi-lean methanol is recycled back to the CO2 absorption tower, and stream B of the semi-lean methanol enters the CO2 washing section for a second washing with CO2 flash gas, and the obtained second CO2-rich methanol is recycled back to the H2S washing section for a third washing with H2S flash gas to obtain low-sulfur and carbon-rich methanol; the first stream of CO2-rich methanol, the first stream of H2S-rich methanol, the low H2S methanol and the low-sulfur and carbon-rich methanol are each independently recycled back to the H2S absorption tower.

9. The device according to claim 8, wherein: The H2S absorption tower comprises a first H2S absorption section disposed at the bottom and a second H2S absorption section disposed at the top; Preferably, the first stream of H2S-rich methanol is recycled back to the first H2S absorption stage; the first stream of CO2-rich methanol, low H2S methanol and low sulfur carbon-rich methanol are each independently recycled back to the second H2S absorption stage; And / or, the CO2 absorption tower comprises a first CO2 absorption section disposed at the bottom and a second CO2 absorption section disposed at the top, and the bottom of the second CO2 absorption section is connected to the top of the first CO2 absorption section; Preferably, the semi-lean methanol stream A is recycled back to the second CO2 absorption stage.

10. The device according to claim 9, wherein: A first pump is provided on the pipeline connecting the low H2S methanol outlet of the reabsorption tower and the second H2S absorption section, for circulating the low H2S methanol back to the second H2S absorption section after the first pressurization; And / or, according to the material flow direction, a second pump and a third cooler are sequentially arranged on the pipeline connecting the first CO2-rich methanol outlet of the CO2 absorption tower and the second H2S absorption section, so as to circulate the first CO2-rich methanol back to the second H2S absorption section after the second pressurization and the third cooling; And / or, a third pump is provided on the pipeline connecting the semi-lean liquid methanol outlet of the reabsorption tower, the second CO2 absorption section and the CO2 washing section, for dividing the first stream of semi-lean liquid methanol into two streams after the third pressurization, and circulating them back to the second CO2 absorption section and the CO2 washing section respectively; and / or, a fourth pump is provided on the pipeline connecting the second H2S absorption section and the H2S washing section, for circulating the low-sulfur and carbon-rich methanol back to the second H2S absorption section after the fourth pressurization; and / or, a fourth cooler is provided on the pipeline connecting the second CO2 absorption section and the first CO2 absorption section; And / or, a fifth cooler is provided on the pipeline connecting the CO2 flash section and the upper part of the reabsorption tower.

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