Low-temperature low-sulfur synthesis gas purification 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 synthesis gas purification method matched with a coal water slurry gasification device and a purification device.According to the method, the H2S absorption process is optimally set, low-sulfur carbon-rich methanol is used for washing synthesis gas, and the use amount of first CO2-rich methanol is reduced; by optimally arranging a medium-pressure flash evaporation process, the method has the advantages that primary flash evaporation equipment is efficient and simple, the equipment arrangement is flexible and convenient, the energy consumption of flash steam recovery is low, flash steam generated by secondary flash evaporation is independently washed without mutual pollution, the use efficiency of low H2S methanol is high, and the like; the low-H2S methanol is generated by optimizing the flow of the re-absorption tower, meanwhile, the low-H2S methanol is prevented from being deeply polluted, and the low-temperature methanol washing device has the characteristic of low comprehensive energy consumption.

Description

Technical Field

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

[0002] In the syngas produced by the coal water 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, ammonia, and ethylene glycol after adjusting the hydrogen-carbon ratio through a 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 an 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 pressure-reduced flash evaporation of the CO 2 -rich methanol. 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 CO 2 -rich methanol can be recycled through pressure-reduced flash evaporation, but the H 2 S-rich 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 utilization efficiency of the H 2 S-rich methanol is the key factor in technological innovation. Specifically, it is necessary to achieve that before the thermal regeneration of the H 2 S-rich methanol, its absorption of H 2 S gas in the syngas reaches the upper limit, so as to reduce the production amount of the H 2 S-rich methanol and the subsequent thermal regeneration amount.

[0005] CN201110260570.0 discloses a low-temperature methanol washing process. First, in this low-temperature methanol washing process, all of the H 2 S absorption tower uses CO 2Methanol is used to wash the syngas, increasing the production of rich H 2 S methanol. The rich H 2 S methanol needs to be thermally regenerated before it can be recycled, resulting in high energy consumption. Second, in the flash section of the reabsorption tower, the rich CO 2 methanol directly mixes with the rich H 2 S methanol flash gas while washing the rich H 2 S methanol, and itself is contaminated by the rich H 2 S methanol. The resulting low-concentration H 2 S methanol is not fully utilized either. Third, the rich H 2 S methanol contaminates the CO 2 gas while washing the CO 2 gas flashed from the upper tower of the washing absorption medium-pressure flash tower, which is not conducive to reducing the comprehensive energy consumption of the cold methanol wash unit. Summary of the Invention

[0006] In order to overcome the above technical problems, the present invention provides a method for purifying low-temperature and low-sulfur syngas for a coal water slurry gasification unit and a device for purifying low-temperature and low-sulfur syngas for a coal water slurry gasification unit. By optimizing the H 2 S absorption process and using low-sulfur and carbon-rich methanol to wash the syngas, the consumption of the first rich CO 2 methanol is reduced; by optimizing the medium-pressure flash process, it has the advantages of high efficiency and simplicity of the first-stage flash equipment, flexible and convenient equipment layout, low energy consumption for flash gas recovery, non-mutual contamination of the flash gases generated by the second-stage flash, and high utilization efficiency of low H 2 S methanol; by optimizing the reabsorption tower process, low H 2 S methanol is generated, and at the same time, the low H 2 S methanol is prevented from being deeply contaminated, featuring low comprehensive energy consumption of the cold methanol wash unit.

[0007] To achieve the above object, on the one hand, the present invention provides a method for purifying low-temperature and low-sulfur syngas for a coal water slurry gasification unit, the method comprising: subjecting the syngas to H 2 S absorption to obtain first rich H 2 S methanol and desulfurized gas; subjecting the desulfurized gas to CO 2 absorption to obtain rich CO 2 methanol in two streams; subjecting the second stream of rich CO 2 methanol to first-stage CO 2 flash and second-stage CO 2 flash to obtain rich CO 2 methanol in two streams after flashing. The first stream of rich CO 2 methanol after flashing undergoes a first flash to obtain semi-lean liquid methanol, and the second stream of rich CO 2The methanol is secondarily flashed after the first cooling;

[0008] The first H 2 S-rich methanol is divided into two streams, and the second H 2 S-rich methanol is secondarily cooled and then undergoes primary H 2 S flashing and secondary H 2 S flashing, and the flashed H 2 S-rich methanol after flashing undergoes a third flashing, and the sulfur-containing gas phase obtained is subjected to a first washing with the flashed solution obtained from the second flashing to obtain low-H 2 S methanol; wherein, the first H 2 S-rich methanol, the first CO 2 -rich methanol, and the low-sulfur carbon-rich methanol each independently return and undergo the H 2 S absorption, and the low-sulfur carbon-rich methanol is prepared by successively contacting the low-H 2 S methanol with the flashed gas phases of the secondary CO 2 flashing and secondary H 2 S flashing.

[0009] The second aspect of the present invention provides a low-temperature and low-sulfur syngas purification device for a coal water slurry gasification device, and the device includes: an H 2 S absorption tower, a CO 2 absorption tower, a primary CO 2 flashing tank, a primary H 2 S flashing tank, a secondary flashing tower, and a reabsorption tower, as well as a first cooler and a second cooler; the secondary flashing tower includes a CO 2 flashing section provided thereon and an H 2 S flashing section provided below, and the upper part of the CO 2 flashing section and the upper part of the H 2 S flashing section are connected by a pipeline;

[0010] The syngas enters the H 2 S absorption tower for H 2 S absorption, and the desulfurized gas obtained enters the CO 2 absorption tower for CO 2 absorption, and the CO 2 -rich methanol obtained is divided into two streams, and the second CO 2 -rich methanol successively enters the primary CO 2 flashing tank and the lower part of the CO 2 flashing section, and undergoes primary CO 2 flashing and secondary CO 2 flashing respectively, and the flashed CO 2 -rich methanol obtained is divided into two streams, and the first flashed CO 2Methanol enters the upper part of the reabsorption tower for the first flash evaporation to obtain semi-lean methanol, and the second flash evaporation produces rich CO 2 After passing through the first cooler, the methanol enters the middle part of the reabsorption tower for the second flash evaporation;

[0011] Regarding the H 2 The first rich H 2 S methanol obtained from H 2 S absorption is divided into two streams. The second stream of rich H 2 S methanol, after passing through the second cooler, successively enters the first-stage H 2 S flash tank and the lower part of the H 2 S flash section, where first-stage H 2 S flash evaporation and second-stage H 2 S flash evaporation are respectively carried out to obtain rich H 2 S methanol after flash evaporation enters the lower part of the reabsorption tower for the third flash evaporation. The sulfur-containing gas phase obtained is subjected to the first washing with the flash evaporation solution obtained from the second flash evaporation to obtain low-H

[0012] Among them, the low-H 2 S methanol enters the upper part of the CO 2 flash section and is subjected to the second washing with the second-stage CO 2 flash gas obtained from the second-stage CO 2 flash evaporation. The low-sulfur methanol obtained enters the upper part of the H 2 S flash section and is subjected to the third washing with the second-stage H 2 S flash gas obtained from the second-stage H 2 S flash evaporation to obtain low-sulfur rich-carbon methanol; the first stream of rich H 2 S methanol, the first stream of rich CO 2 methanol, and the low-sulfur rich-carbon methanol are each independently recycled to the H 2 S absorption tower.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] (1) In the method provided by the present invention, by optimizing the medium-pressure flash evaporation process and adopting two-stage flash evaporation, that is, the first-stage flash evaporation uses a relatively high flash evaporation pressure, and the effective gas flashed out can be directly sent to the second stage of the compressor in the compression process, reducing the power consumption of the compressor; at the same time, the first-stage flash evaporation equipment uses a horizontal container, which has a low equipment height and can be flexibly and efficiently arranged on the frame, reducing the floor area of the device; the second-stage flash evaporation uses a relatively low flash evaporation pressure to ensure that the effective gas in the rich CO 2 methanol after the first-stage flash evaporation and the rich H 2 S methanol after the first-stage flash evaporation is fully recovered, and at the same time, the intake air volume of the first-stage cylinder of the compressor in the compression process can be reduced, correspondingly reducing the power consumption of the compressor;

[0015] (2) The method provided by the present invention optimizes the secondary medium-pressure flash process flow. By using low-H2S methanol to first perform a second wash on the secondary CO flash gas, the CO component in the secondary CO flash gas is reduced without contaminating the rich CO methanol after flashing. At the same time, the low-H2S methanol performs a cascade wash on the secondary H2S flash gas, achieving hierarchical flashing and classified cascade washing, avoiding the technical problem of the CO gas in the rich CO methanol after flashing being transferred to the rich H2S methanol after flashing, which is beneficial to reducing the energy consumption of the device; 2 S methanol first performs a second wash on the secondary CO 2 flash gas to reduce the CO 2 in the secondary CO 2 flash gas without contaminating the rich CO 2 methanol after flashing; meanwhile, the low-H2S 2 methanol performs a cascade wash on the secondary H2S 2 flash gas, realizing hierarchical flashing and classified cascade washing, and avoiding the technical problem that the CO 2 gas in the rich CO 2 methanol after flashing is transferred to the rich H2S 2 methanol after flashing, which is beneficial to reducing the energy consumption of the device;

[0016] (3) The method provided by the present invention optimizes the reabsorption process flow, achieving the absorption of the sulfur-containing gas phase generated by the flashing of the flash liquid of the rich CO methanol after the second flash on the rich H2S methanol after flashing, but without mixing with the third rich H2S 2 methanol after flashing, making the H2S content in the solution lower, called low-H2S 2 methanol; 2 S methanol 2 S content is lower, called low-H2S 2 S methanol;

[0017] (4) The method provided by the present invention optimizes the H2S absorption process flow. By using low-sulfur rich-carbon methanol to absorb the H2S gas in the syngas, the recycling of the low-sulfur rich-carbon methanol is realized, and at the same time, the usage amount of the first rich CO 2 S absorption process flow, using low-sulfur rich-carbon methanol to absorb the H2S 2 gas in the syngas, realizing the recycling of the low-sulfur rich-carbon methanol, and at the same time reducing the usage amount of the first rich CO 2 methanol in the H2S absorption, which is equivalent to reducing the second rich H2S 2 methanol that needs to be thermally regenerated. 2 S methanol. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of a low-temperature and low-sulfur syngas purification device for a coal water slurry gasification device provided by the present invention.

[0019] Description of the Reference Numerals

[0020] T-1, H2S 2 absorption tower; T-2, CO 2 absorption tower; V-1, primary CO 2 flash tank; V-2, primary H2S 2S Flash Tank; T-3, Secondary Flash Tower; T-4, 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;

[0021] 1, Syngas; 2, Second H-Rich 2 S Methanol; 3, First H-Rich 2 S Methanol; 3-i, First Stream of H-Rich 2 S Methanol; 3-ii, Second Stream of H-Rich 2 S Methanol; 4, Low-Sulfur H-Rich Methanol; 5, Desulfurized Gas; 6, CO-Rich 2 Methanol; 6-i, First Stream of CO-Rich 2 Methanol; 6-ii, Second Stream of CO-Rich 2 Methanol; 7, CO-Containing 2 Methanol; 8, Semi-Poor Methanol; 8-i, First Stream of Semi-Poor Methanol; 8-ii, Second Stream of Semi-Poor Methanol; 9, Lean Methanol; 10, Purified Gas; 11, CO-Rich after First-Stage Flash 2 Methanol; 12, First-Stage Flash Gas; 12-i, First-Stage CO 2 Flash Gas; 12-ii, First-Stage H 2 S Flash Gas; 13, CO-Rich after Flash 2 Methanol; 13-i, First Stream of CO-Rich after Flash 2 Methanol; 13-ii, Second Stream of CO-Rich after Flash 2 Methanol; 14, Secondary Flash Gas; 14-i, Secondary Flash Gas-I; 14-ii, Secondary Flash Gas-II; 15, Low-Sulfur Methanol; 16, H-Rich after First-Stage Flash 2 S Methanol; 17, H-Rich after Flash 2 S Methanol; 18, CO 2 Product Gas; 19, Third H-Rich 2 S Methanol; 20, Low-H 2 S Methanol. Detailed Embodiments

[0022] The endpoints and any values disclosed herein of a range are not limited to the exact range or value, 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.

[0023] In the present invention, without special circumstances, "first", "second", "third", "fourth", and "fifth" neither indicate 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, in "first cooling", "second cooling", "third cooling", "fourth cooling", and "fifth cooling", "first", "second", "third", "fourth", and "fifth" are only used to indicate that these are not the same cooling.

[0024] In the present invention, without special circumstances, the "top" of the container refers to the 0-10% height of the container from top to bottom; the "upper part" of the container refers to the 10-40% height of the container from top to bottom; the "middle part" of the container refers to the 40-60% height of the container from top to bottom; the "lower part" of the container refers to the 60-90% height of the container from top to bottom; the "bottom" of the container refers to the 90-100% height of the container from top to bottom.

[0025] On the one hand, the present invention provides a method for purifying low-temperature and low-sulfur syngas for a supporting water coal gasification device, and the method includes: subjecting the syngas to H 2 S absorption to obtain first H 2 S-rich methanol and desulfurized gas; subjecting the desulfurized gas to CO 2 absorption to obtain the CO 2 -rich methanol in two streams; subjecting the second stream of CO 2 -rich methanol to primary CO 2 flashing and secondary CO 2 flashing to obtain the flashed CO 2 -rich methanol in two streams, the first stream of flashed CO 2 -rich methanol undergoes first flashing to obtain semi-lean liquid methanol, and the second stream of flashed CO 2 -rich methanol undergoes second flashing after first cooling;

[0026] Dividing the first H 2 S-rich methanol into two streams, the second stream of H 2 S-rich methanol undergoes second cooling and then primary H 2 S flashing and secondary H 2 S flashing to obtain the flashed H 2 S-rich methanol undergoes third flashing, and the sulfur-containing gas phase obtained is subjected to first washing with the flashed solution obtained from the second flashing to obtain low-H 2 S methanol; wherein, the first stream of H 2 S-rich methanol, the first stream of CO 2 -rich methanol, and low-sulfur carbon-rich methanol each independently return and undergo the H 2 S absorption, and the low-sulfur carbon-rich methanol is obtained by sequentially reacting the low-H 2 S methanol with the secondary CO2 Flash evaporation, secondary H 2 Obtained by contacting the flash vapor of S flash evaporation.

[0027] In some embodiments of the present invention, preferably, the H 2 The process of S absorption includes: contacting the syngas and the first stream of rich H 2 S methanol and performing the first H 2 S absorption to obtain the pre-washed syngas and the second rich H 2 S methanol; contacting the pre-washed syngas, low-sulfur rich-carbon methanol and the first stream of rich CO 2 Methanol and performing the second H 2 S absorption to obtain the first rich H 2 S methanol and desulfurized gas.

[0028] In some embodiments of the present invention, preferably, the H 2 The molar content of S in the syngas is 0.9 - 1.2%, and the CO 2 The molar content is 40 - 50%; the temperature is -15 to -5 °C, and the pressure is 5.2 - 5.7 MPa(G). In the present invention, the source of the syngas has a relatively wide selection range, as long as the syngas meets the above limitations. Preferably, the syngas is selected from the upstream syngas cooling process.

[0029] In some embodiments of the present invention, preferably, the molar flow ratio of the syngas and the first stream of rich H 2 S methanol is 70 - 80:1.

[0030] 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 rich H 2 S methanol is 0.2 - 0.4%, and the CO 2 The molar content is 70 - 75%. In the present invention, the temperature of the second rich H 2 S methanol is -15 to -5 °C, and the pressure is 5.2 - 5.7 MPa(G).

[0031] In some embodiments of the present invention, preferably, the first rich H 2 S methanol is divided into a first stream of rich H 2 S methanol and a second stream of rich H 2 S methanol with a molar flow ratio of 1:50 - 60.

[0032] In the present invention, the first rich H2 The methanol is divided into two streams. The first stream returns and undergoes the first H 2 S absorption, and the second stream undergoes the first-stage H 2 S flash evaporation after the second cooling.

[0033] In the present invention, the second H 2 S absorption aims to further remove H 2 S and a small amount of CO 2 from the syngas. Preferably, the molar content of CO 2 in the first rich H 2 S methanol is 38 - 42%, and the molar content of H 2 S is 1.5 - 1.8%; the temperature is -10 to -5 °C, and the pressure is 5.2 - 5.5 MPa(G).

[0034] In some embodiments of the present invention, preferably, the molar flow rate ratio of the low-sulfur rich-carbon methanol to the syngas is 1:5 - 7.

[0035] In some embodiments of the present invention, preferably, the molar flow rate ratio of the first stream of rich CO 2 methanol to the syngas is 1:2 - 3.

[0036] In some embodiments of the present invention, preferably, the molar content of H 2 S in the desulfurized gas is 0.5 - 1 ppm, and the molar content of CO 2 is 38 - 42%; the temperature is -20 to -10 °C; the pressure is 5.3 - 5.4 MPa(G).

[0037] In some embodiments of the present invention, preferably, after the low-sulfur rich-carbon methanol is pressurized to 5.6 - 6 MPa(G) for the first time, it returns and undergoes the second H 2 S absorption.

[0038] In some embodiments of the present invention, preferably, in the direction of material flow, the first stream of rich CO 2 methanol is sequentially pressurized to 5.8 - 6 MPa(G) for the second time and cooled to -35 to -25 °C for the third time, and then returns and undergoes the second H 2 S absorption.

[0039] In the present invention, to reduce the usage amount of lean methanol. Preferably, the semi-lean liquid methanol 8 is divided into two streams. The first stream of semi-lean liquid methanol returns and undergoes the CO 2 absorption, and the second stream of semi-lean liquid methanol 8-ii is sent to the subsequent process.

[0040] In some embodiments of the present invention, preferably, the CO 2The absorption process includes: the desulfurized gas and the CO 2 Methanol contact and first CO 2 Absorb and obtain the rich CO 2 Methanol and pre-purified gas; contacting the pre-purified gas, the first stream of semi-lean methanol and lean methanol and performing a second CO 2 Absorb to obtain purified gas and the CO 2 Methanol.

[0041] In the present invention, the first CO 2 Absorption is intended to further remove CO from sweetened gas 2 . Preferably, the CO-rich 2 CO in methanol 2 The molar content of is 31-35%, H 2 The molar content of S is 0.1-0.5ppm; the temperature is -15 to -10℃, and the pressure is 5.2-5.4MPa(G).

[0042] In the present invention, the CO-rich 2 Methanol is divided into two streams, the first stream is returned and subjected to the H 2 S absorption, the second stream for primary CO 2 Flash evaporation. Preferably, the CO-rich 2 Methanol is divided into the first stream rich in CO with a molar flow ratio of 1:1.8-2.3 2 Methanol and a second CO-rich stream 2 Methanol.

[0043] In some embodiments of the present invention, preferably, the desulfurized gas and CO 2 The molar flow ratio of methanol is 1:1.1-1.3.

[0044] In some embodiments of the present invention, preferably, the molar flow ratio of the purified gas to the first stream of semi-lean methanol is 1.4-1.6:1.

[0045] In some embodiments of the present invention, preferably, the molar flow ratio of the purified gas to lean methanol is 1:1-1.1.

[0046] In some embodiments of the present invention, preferably, H in the purified gas 2 S molar content ≤ 0.1ppm, CO 2 Mole content ≤ 20ppm; temperature -55 to -50℃, pressure 5.1-5.3MPa(G).

[0047] In some embodiments of the present invention, preferably, the CO-containing 2 After the methanol is cooled to -36 to -33°C for the fourth time, it is returned and subjected to the first CO​​​​2 Absorption

[0048] In some embodiments of the present invention, preferably, after the first semi-lean methanol is pressurized to 5.6 - 6 MPa(G) for the third time, it is returned and the second CO 2 Absorption

[0049] In some embodiments of the present invention, preferably, the pressure of the first-stage CO 2 flashing > the pressure of the second-stage CO 2 flashing; further preferably, the pressure of the first-stage CO 2 flashing is 3.5 - 3.7 MPa(G); the pressure of the second-stage CO 2 flashing is 1.6 - 2 MPa(G).

[0050] In some embodiments of the present invention, preferably, the process of the first-stage CO 2 flashing includes: subjecting the second rich CO 2 methanol to the first-stage CO 2 flashing to obtain first-stage CO 2 flashed gas and first-stage flashed rich CO 2 methanol; the process of the second-stage CO 2 flashing includes: subjecting the first-stage flashed rich CO 2 methanol to the second-stage CO 2 flashing to obtain second-stage CO 2 flashed gas and the flashed rich CO 2 methanol.

[0051] In some embodiments of the present invention, preferably, the temperature of the first-stage CO 2 flashed gas is -36.5 to -33.5 °C; the pressure is 3.5 - 3.7 MPa(G).

[0052] In some embodiments of the present invention, preferably, the molar content of H 2 S in the first-stage flashed rich CO 2 methanol is 0.1 - 0.5 ppm, and the molar content of CO 2 is 30.5 - 34.5%; the temperature is -36.5 to -33.5 °C.

[0053] In some embodiments of the present invention, further preferably, before the first-stage CO 2 flashing, the second rich CO 2 methanol is cooled to -36 to -33 °C for the fifth time.

[0054] In some embodiments of the present invention, preferably, the flashed rich CO 2H in methanol 2 The molar content of S is 0.1 - 0.5 ppm, and the molar content of CO 2 is 30 - 34%; the temperature is -37 to -34 °C.

[0055] In the present invention, the second cooling reduces the temperature of the second H 2 S-rich methanol stream, aiming to reduce the total amount of medium-pressure flash gas and lay the 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.

[0056] In some embodiments of the present invention, preferably, the pressure of the first-stage H 2 S flash > the pressure of the second-stage H 2 S flash; more preferably, the pressure of the first-stage H 2 S flash is 3.5 - 3.7 MPa(G); the pressure of the second-stage H 2 S flash is 1.6 - 2 MPa(G).

[0057] In some embodiments of the present invention, preferably, the process of the first-stage H 2 S flash includes: subjecting the second H 2 S-rich methanol stream to the first-stage H 2 S flash after the second cooling to obtain first-stage H 2 S flash gas and first-stage flash-after H 2 S-rich methanol; the process of the second-stage H 2 S flash includes: subjecting the first-stage flash-after H 2 S-rich methanol to the second-stage H 2 S flash to obtain second-stage H 2 S flash gas and the flash-after H 2 S-rich methanol.

[0058] In some embodiments of the present invention, preferably, the temperature of the first-stage H 2 S flash gas is -33.5 to -30.5 °C, and the pressure is 3.5 - 3.7 MPa(G). In the present invention, the first-stage CO 2 flash gas and the first-stage H 2 S flash gas are mixed, and the obtained first-stage flash gas is directly sent to the second stage of the compressor in the compression process, reducing the compressor energy consumption.

[0059] In the present invention, the molar content of H 2 in the first-stage flash gas is 70 - 74%, and the CO 2The molar content of is 24 - 29%, and the molar content of CO is 0.4 - 0.8%; the temperature is -36.5 to -33.5 °C; the pressure is 3.5 - 3.7 MPa(G).

[0060] In some embodiments of the present invention, preferably, after the first flash evaporation, the rich H 2 in the S methanol, the H 2 The molar content of S is 1.5 - 1.7%, and the CO 2 The molar content of is 37.5 - 41.5%; the temperature is -33.5 to -30.5 °C.

[0061] In some embodiments of the present invention, preferably, after the flash evaporation, the rich H 2 in the S methanol, the H 2 The molar content of S is 1.5 - 1.8%, and the CO 2 The molar content of is 37 - 41%; the temperature is -34 to -31 °C.

[0062] In some embodiments of the present invention, preferably, the rich CO 2 methanol after the flash evaporation is divided into the first rich CO 2 methanol after the flash evaporation and the second rich CO 2 methanol with a molar flow ratio of 3.5 - 4.5:1.

[0063] In the present invention, the first cooling reduces the temperature of the second rich CO 2 methanol after the flash evaporation, generates low temperature through pressure reduction flash evaporation, and improves the absorption capacity of the rich CO 2 methanol after the flash evaporation for H 2 S gas, which is beneficial to washing the H 2 in the product gas of the flash evaporation after CO 2 S gas. Preferably, the temperature of the material after the first cooling is -55 to -50 °C.

[0064] In some embodiments of the present invention, preferably, 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); the pressure of the third flash evaporation is 0.12 - 0.16 MPa(G).

[0065] In some embodiments of the present invention, preferably, the process of the first flash evaporation includes: subjecting the first rich CO 2 methanol after the flash evaporation to the first flash evaporation to obtain the semi-lean liquid methanol and the first CO 2 product gas; the process of the second flash evaporation includes: subjecting the material after the first cooling to the second flash evaporation to obtain the solution after the flash evaporation and the second CO 2Product gas; The process of the third flash evaporation includes: subjecting the flashed rich H 2 S methanol to a third flash evaporation to obtain a third rich H 2 S methanol and a sulfur-containing gas phase.

[0066] In some embodiments of the present invention, preferably, the molar content of CO in the semi-lean methanol is 22-25%, and the molar content of H 2 S is ≤0.5 ppm; the temperature is -66 to -60 °C; the pressure is 0.05-0.08 MPa(G). 2 In some embodiments of the present invention, preferably, the semi-lean methanol is divided into a first semi-lean methanol and a second semi-lean methanol with a molar flow ratio of 1.4-1.6:1. In the present invention, the second semi-lean methanol is sent to subsequent processes for use.

[0067] In some embodiments of the present invention, preferably, the molar content of H in the low-H

[0068] S methanol is 0.8-1.2%, and the molar content of CO 2 S is 0.8-1.2%, and the molar content of CO 2 S is 0.8-1.2%, and the molar content of CO 2 is 28-32%; the temperature is -65 to -60 °C, and the pressure is 0.12-0.16 MPa(G).

[0069] In some embodiments of the present invention, preferably, the molar content of H in the third rich H 2 S methanol is 1.5-1.7%, and the molar content of CO 2 S is 1.5-1.7%, and the molar content of CO 2 is 27-30%; the temperature is -68 to -65 °C; the pressure is 0.13-0.17 MPa(G).

[0070] In some embodiments of the present invention, preferably, the first CO 2 product gas obtained by the first flash evaporation, the second CO 2 product gas obtained by the second flash evaporation, and the third CO 2 product gas obtained by the first washing are mixed to obtain a CO 2 product gas with a molar content of H 2 S < 1 ppm and a molar content of CO 2 of 99.4-99.7%; the temperature is -66 °C to -64 °C, and the pressure is 0.05-0.08 MPa(G).

[0071] In some embodiments of the present invention, preferably, the low-H 2 S methanol and the secondary CO 2 product gas obtained by flashing the secondary CO 2The flash steam is subjected to a second washing to obtain low-sulfur methanol and secondary flash steam-I; the low-sulfur methanol is combined with the secondary H 2 S flash steam obtained from the flash evaporation of secondary H 2 S flash steam is subjected to a third washing to obtain the low-sulfur carbon-rich methanol and secondary flash steam-II.

[0072] In some embodiments of the present invention, preferably, the molar content of H 2 S in the low-sulfur carbon-rich methanol is ≤1%, and the molar content of CO 2 is 28-32%; the temperature is -63 to -60°C.

[0073] In some embodiments of the present invention, preferably, the low-H 2 S methanol is pressurized to 1.6-2 MPa(G) in the fourth stage, returned, and subjected to the second washing.

[0074] In some embodiments of the present invention, preferably, the molar content of H 2 S in the low-sulfur methanol is ≤1%, and the molar content of CO 2 is 27-31%; the temperature is -65 to -60°C.

[0075] In some embodiments of the present invention, preferably, the temperature of the secondary flash steam-I is -65°C to -60°C, the pressure is 1.6-2 MPa(G), and it is sent to subsequent processes for treatment.

[0076] In some embodiments of the present invention, preferably, the temperature of the secondary flash steam-II is -65°C to -60°C, the pressure is 1.6-2 MPa(G), and it is sent to subsequent processes for treatment.

[0077] In the present invention, the secondary flash steam-I and the secondary flash steam-II are mixed to obtain secondary flash steam, which is sent to subsequent processes for treatment.

[0078] In some embodiments of the present invention, the molar content of H 2 in the secondary flash steam is 80-85%, the molar content of CO 2 is 15-19%, and the molar content of CO is 0.05-0.15%; the temperature is -65°C to -60°C, and the pressure is 1.6-2 MPa(G).

[0079] The second aspect of the present invention provides a structural schematic diagram of a low-temperature and low-sulfur syngas purification device for a coal water slurry gasification device, as shown in Figure 1. 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, primary CO 2 flash tank V-1, primary H2 S flash tank V-2, secondary flash tower T-3 and reabsorption tower T-4, as well as the first cooler E-1 and the second cooler E-2; the secondary flash tower T-3 includes a CO 2 flash section provided thereon and an H 2 S flash section provided therebelow, and the upper part of the CO 2 flash section is connected to the upper part of the H 2 S flash section through a pipeline;

[0080] Synthesis gas 1 enters the H 2 S absorption tower T-1 for H 2 S absorption, and the desulfurized gas 5 obtained enters the CO 2 absorption tower T-2 for CO 2 absorption, and the rich CO 2 methanol 6 is divided into two streams, and the second stream of rich CO 2 methanol 6-ii sequentially enters the first-stage CO 2 flash tank V-1 and the lower part of the CO 2 flash section, and respectively perform first-stage CO 2 flash and second-stage CO 2 flash, and the rich CO 2 methanol 13 after flash is divided into two streams, and the first stream of rich CO 2 methanol 13-i enters the upper part of the reabsorption tower T-4 for the first flash, and the semi-lean liquid methanol 8 is obtained. The second stream of rich CO 2 methanol 13-ii enters the middle part of the reabsorption tower T-4 for the second flash after passing through the first cooler E-1;

[0081] The first rich H 2 S methanol 3 obtained from the H 2 S absorption is also divided into two streams, and the second stream of rich H 2 S methanol 3-ii enters the first-stage H 2 S flash tank V-2 and the lower part of the H 2 S flash section after passing through the second cooler E-2, and respectively perform first-stage H 2 S flash and second-stage H 2 S flash, and the rich H 2 S methanol 17 enters the lower part of the reabsorption tower T-4 for the third flash, and the sulfur-containing gas phase obtained is subjected to the first washing with the flashed solution obtained from the second flash, and the low H 2 S methanol 20 is obtained;

[0082] The low H 2 S methanol 20 enters the upper part of the CO 2 flash section, and is combined with the second-stage CO 2 obtained from the second-stage CO 2The flash vapor is subjected to a second washing, and the resulting low-sulfur methanol 15 enters the upper part of the H 2 S flash section, and is combined with the secondary H 2 S flash vapor obtained from the secondary H 2 S flash to perform a third washing, obtaining low-sulfur carbon-rich methanol 4; wherein, the first rich H 2 S methanol 3-i, the first rich CO 2 methanol 6-i, and the low-sulfur carbon-rich methanol 4 are each independently recycled to the H 2 S absorption tower T-1.

[0083] 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 at the lower part and a second H 2 S absorption section provided at the upper part. Specifically, for the first H 2 S absorption section, the first rich H 2 S methanol 3-i pre-washes and absorbs H 2 S, HCN, NH 3 in the syngas 1; for the second H 2 S absorption section, by introducing the low-sulfur carbon-rich methanol 4 to absorb H 2 S and CO 2 gases in the pre-washed syngas, the recycling of the low-sulfur carbon-rich methanol is realized, and the usage amount of the first rich CO 2 methanol 6-i is reduced, which is equivalent to reducing the first rich H 2 S methanol that needs to be thermally regenerated; in addition, such a setting correspondingly reduces the working load of the subsequent CO 2 absorption tower, which is also of positive significance for reducing the usage amounts of lean methanol and semi-lean methanol in the CO 2 absorption tower.

[0084] In the present invention, as Figure 1 shown, the first rich H 2 S methanol 3-i is recycled to the first H 2 S absorption section; the first rich CO 2 methanol 6-i and the low-sulfur carbon-rich methanol 4 are each independently recycled to the second H 2 S absorption section.

[0085] In the present invention, as Figure 1 shown, in the H 2 S absorption tower T-1, the first H 2 S absorption section and the second H 2 S absorption section are connected by lifting holes; the first H 2 S absorption section is connected to the second H 2The first H-rich in the S absorption section 2 The S methanol outlet is used to bring the syngas 1 into contact with the first H-rich 2 S methanol 3-i and carry out the first H 2 S absorption to obtain the second H-rich 2 S methanol 2 and the pre-washed syngas; the second H 2 The S absorption section is connected to the H 2 The low-sulfur and carbon-rich methanol outlet at the upper part of the S flash section is connected to the CO 2 The CO-rich methanol outlet of the absorption tower T-2 is used to bring the pre-washed syngas into contact with low-sulfur and carbon-rich methanol 4 and the first CO-rich 2 S methanol 6-i in sequence and carry out the second H 2 S absorption to obtain the desulfurized gas 5 and the first H-rich 2 S methanol 3. 2 S methanol 3.

[0086] In the present invention, without special description, the first H 2 In the S absorption section, the contact mode between the syngas and the first H-rich 2 S methanol 3-i is preferably countercurrent contact between the syngas 1 and the first H-rich 2 S methanol 3-i, that is, the syngas 1 enters from the bottom of the first H 2 S absorption section, and the first H-rich 2 S methanol 3-i enters from the upper part of the first H 2 S absorption section.

[0087] 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 lower part and a second CO 2 absorption section arranged at the upper part, and the lower part of the second CO 2 absorption section is connected to the upper part of the first CO 2 absorption section.

[0088] 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 lower part and a second CO 2 absorption section arranged at the upper part; the first CO 2 absorption section and the second CO 2 absorption section are connected through upflow holes, wherein the upper part of the first CO 2 absorption section is connected to the lower part of the second CO 2 absorption section for bringing the desulfurized gas 5 into contact with the CO-containing 2 methanol 7 and carrying out the first CO 2Absorption to obtain the CO-rich 2 methanol 6 and the pre-purified gas; the second CO 2 absorption section is connected to the semi-lean methanol outlet of the re-absorption tower T-4 and the lean methanol 9 from the subsequent process, and is used to successively contact the pre-purified gas with the first stream of semi-lean methanol 8-i and lean methanol 9 and perform the second CO 2 absorption to obtain the purified gas 10 and the CO-containing 2 methanol 7.

[0089] In the present invention, without special circumstances, the CO 2 in the absorption tower T-2, the first CO 2 absorption section, the desulfurized gas 5 and the CO-containing 2 methanol 7 are preferably in counter-current contact; that is, the desulfurized gas 5 enters from the bottom of the first CO 2 absorption section, and the CO-containing 2 methanol 7 enters from the upper part of the first CO 2 absorption section. 2 2

[0090] In the present invention, as Figure 1 shown, the first-stage CO 2 flash tank V-1 is used to perform the first-stage CO 2 flash on the second stream of CO-rich 2 methanol 6-ii to obtain the first-stage CO 2 flash gas 12-i and the first-stage flash CO-rich 2 methanol 11; the first-stage H 2 S flash tank V-2 is used to perform the first-stage H 2 S flash on the second stream of H-rich 2 S methanol 3-ii after the second cooling to obtain the first-stage H 2 S flash gas 12-ii and the first-stage flash H-rich 2 S methanol 16.

[0091] In the present invention, as Figure 1 shown, the second-stage flash tower T-3 includes a CO 2 flash section provided on the upper part and an H 2 S flash section provided on the lower part, and the upper part of the CO 2 flash section and the upper part of the H 2 S flash section are connected by a pipeline.

[0092] In the present invention, as Figure 1 shown, the upper and lower parts of the CO 2 flash section are connected by lifting holes, and the upper and lower parts of the H 2 S flash section are connected by lifting holes. Specifically, the CO 2The lower part of the flash evaporation section is used to subject the CO-rich methanol 11 after the first-stage flash evaporation to a second-stage CO flash evaporation to obtain the second-stage CO flash gas and the CO-rich methanol 13 after the flash evaporation. The second-stage CO flash gas enters the upper part of the CO flash evaporation section and is second-washed with the low-H2S methanol 20 to obtain the second-stage flash gas-I 14-i and the low-sulfur methanol 15. 2 The lower part of the H2S flash evaporation section is used to subject the H2S-rich methanol 16 after the first-stage flash evaporation to a second-stage H2S flash evaporation to obtain the second-stage H2S flash gas and the H2S-rich methanol 17 after the flash evaporation. The second-stage H2S flash gas enters the upper part of the H2S flash evaporation section and is third-washed with the low-sulfur methanol 15 to obtain the low-sulfur carbon-rich methanol 4 and the second-stage flash gas-II 14-ii. Among them, the second-stage flash gas-I 14-i and the second-stage flash gas-II 14-ii are mixed to obtain the second-stage flash gas 14. 2 The lower part of the flash evaporation section is used to subject the CO-rich methanol 11 after the first-stage flash evaporation to a second-stage CO flash evaporation to obtain the second-stage CO flash gas and the CO-rich methanol 13 after the flash evaporation. 2 The lower part of the flash evaporation section is used to subject the CO-rich methanol 11 after the first-stage flash evaporation to a second-stage CO flash evaporation to obtain the second-stage CO flash gas and the CO-rich methanol 13 after the flash evaporation. 2 The lower part of the flash evaporation section is used to subject the CO-rich methanol 11 after the first-stage flash evaporation to a second-stage CO flash evaporation to obtain the second-stage CO flash gas and the CO-rich methanol 13 after the flash evaporation. 2 The second-stage CO flash gas enters the upper part of the CO flash evaporation section and is second-washed with the low-H2S methanol 20 to obtain the second-stage flash gas-I 14-i and the low-sulfur methanol 15. 2 The second-stage CO flash gas enters the upper part of the CO flash evaporation section and is second-washed with the low-H2S methanol 20 to obtain the second-stage flash gas-I 14-i and the low-sulfur methanol 15. 2 The second-stage CO flash gas enters the upper part of the CO flash evaporation section and is second-washed with the low-H2S methanol 20 to obtain the second-stage flash gas-I 14-i and the low-sulfur methanol 15. 2 The lower part of the H2S flash evaporation section is used to subject the H2S-rich methanol 16 after the first-stage flash evaporation to a second-stage H2S flash evaporation to obtain the second-stage H2S flash gas and the H2S-rich methanol 17 after the flash evaporation. 2 The lower part of the H2S flash evaporation section is used to subject the H2S-rich methanol 16 after the first-stage flash evaporation to a second-stage H2S flash evaporation to obtain the second-stage H2S flash gas and the H2S-rich methanol 17 after the flash evaporation. 2 The lower part of the H2S flash evaporation section is used to subject the H2S-rich methanol 16 after the first-stage flash evaporation to a second-stage H2S flash evaporation to obtain the second-stage H2S flash gas and the H2S-rich methanol 17 after the flash evaporation. 2 The lower part of the H2S flash evaporation section is used to subject the H2S-rich methanol 16 after the first-stage flash evaporation to a second-stage H2S flash evaporation to obtain the second-stage H2S flash gas and the H2S-rich methanol 17 after the flash evaporation. 2 The lower part of the H2S flash evaporation section is used to subject the H2S-rich methanol 16 after the first-stage flash evaporation to a second-stage H2S flash evaporation to obtain the second-stage H2S flash gas and the H2S-rich methanol 17 after the flash evaporation. 2 The second-stage H2S flash gas enters the upper part of the H2S flash evaporation section and is third-washed with the low-sulfur methanol 15 to obtain the low-sulfur carbon-rich methanol 4 and the second-stage flash gas-II 14-ii. 2 The second-stage H2S flash gas enters the upper part of the H2S flash evaporation section and is third-washed with the low-sulfur methanol 15 to obtain the low-sulfur carbon-rich methanol 4 and the second-stage flash gas-II 14-ii. Among them, the second-stage flash gas-I 14-i and the second-stage flash gas-II 14-ii are mixed to obtain the second-stage flash gas 14.

[0093] In the present invention, as shown, the upper and middle parts of the reabsorption tower T-4 are connected through lifting holes, and the middle and lower parts are also connected through lifting holes. Specifically, the upper part is used to subject the first CO-rich methanol 13-i after the first-stage flash evaporation to a first-stage flash evaporation to obtain the semi-lean liquid methanol 8 and the first CO product gas; the middle part is used to subject the second CO-rich methanol 13-ii after the second-stage flash evaporation to a second-stage flash evaporation after the first cooling to obtain the solution after the flash evaporation and the second CO product gas; the lower part is used to subject the H2S-rich methanol 17 after the flash evaporation to a third-stage flash evaporation to obtain the third H2S-rich methanol 19 and the sulfur-containing gas phase. Among them, the sulfur-containing gas phase and the solution after the flash evaporation are first-washed to obtain the low-H2S methanol 20 and the third CO product gas; the CO product gas 18 includes the first CO product gas, the second CO product gas, and the third CO product gas. Figure 1 In the present invention, as shown, the upper and middle parts of the reabsorption tower T-4 are connected through lifting holes, and the middle and lower parts are also connected through lifting holes. Specifically, the upper part is used to subject the first CO-rich methanol 13-i after the first-stage flash evaporation to a first-stage flash evaporation to obtain the semi-lean liquid methanol 8 and the first CO product gas; the middle part is used to subject the second CO-rich methanol 13-ii after the second-stage flash evaporation to a second-stage flash evaporation after the first cooling to obtain the solution after the flash evaporation and the second CO product gas; the lower part is used to subject the H2S-rich methanol 17 after the flash evaporation to a third-stage flash evaporation to obtain the third H2S-rich methanol 19 and the sulfur-containing gas phase. Among them, the sulfur-containing gas phase and the solution after the flash evaporation are first-washed to obtain the low-H2S methanol 20 and the third CO product gas; the CO product gas 18 includes the first CO product gas, the second CO product gas, and the third CO product gas. 2 The upper part is used to subject the first CO-rich methanol 13-i after the first-stage flash evaporation to a first-stage flash evaporation to obtain the semi-lean liquid methanol 8 and the first CO product gas. 2 The middle part is used to subject the second CO-rich methanol 13-ii after the second-stage flash evaporation to a second-stage flash evaporation after the first cooling to obtain the solution after the flash evaporation and the second CO product gas. 2 The middle part is used to subject the second CO-rich methanol 13-ii after the second-stage flash evaporation to a second-stage flash evaporation after the first cooling to obtain the solution after the flash evaporation and the second CO product gas. 2 The lower part is used to subject the H2S-rich methanol 17 after the flash evaporation to a third-stage flash evaporation to obtain the third H2S-rich methanol 19 and the sulfur-containing gas phase. 2 The lower part is used to subject the H2S-rich methanol 17 after the flash evaporation to a third-stage flash evaporation to obtain the third H2S-rich methanol 19 and the sulfur-containing gas phase. 2 The lower part is used to subject the H2S-rich methanol 17 after the flash evaporation to a third-stage flash evaporation to obtain the third H2S-rich methanol 19 and the sulfur-containing gas phase. 2 Among them, the sulfur-containing gas phase and the solution after the flash evaporation are first-washed to obtain the low-H2S methanol 20 and the third CO product gas. 2 Among them, the sulfur-containing gas phase and the solution after the flash evaporation are first-washed to obtain the low-H2S methanol 20 and the third CO product gas. 2 The CO product gas 18 includes the first CO product gas, the second CO product gas, and the third CO product gas. 2 The CO product gas 18 includes the first CO product gas, the second CO product gas, and the third CO product gas. 2 The CO product gas 18 includes the first CO product gas, the second CO product gas, and the third CO product gas. 2 The CO product gas 18 includes the first CO product gas, the second CO product gas, and the third CO product gas.

[0094] In the present invention, as shown, preferably, the upper part of the H2S flash evaporation section is connected to the second H2S Figure 1 In the present invention, as shown, preferably, the upper part of the H2S flash evaporation section is connected to the second H2S 2 In the present invention, as shown, preferably, the upper part of the H2S flash evaporation section is connected to the second H2S 2A first pump P-1 is provided on the pipeline of the S absorption section to return the low-sulfur carbon-rich methanol 4 after the first pressurization and perform the second H 2 S absorption.

[0095] In the present invention, as Figure 1 shown, preferably, in the direction of material flow, the rich CO 2 methanol outlet of the absorption tower T-2 and the second H 2 are connected, and a second pump P-2 and a third cooler E-3 are sequentially provided on the pipeline of the S absorption section to sequentially pressurize and cool the first stream of rich CO 2 methanol 6-i, and then reuse it in the second H 2 S absorption section. 2 S absorption section.

[0096] In the present invention, as Figure 1 shown, preferably, in the direction of material flow, a fourth cooler E-4 is provided on the pipeline connecting the second CO 2 absorption section and the first CO 2 absorption section to cool the CO 2 -containing methanol 7, and then return it to perform the first CO 2 absorption.

[0097] In the present invention, as Figure 1 shown, preferably, a fifth cooler E-5 is provided on the pipeline connecting the rich CO 2 methanol outlet of the absorption tower T-2 and the first-stage CO 2 flash tank V-1 to cool the second stream of rich CO 2 methanol 6-ii, and then perform the first-stage CO 2 flash. 2 Flash.

[0098] In the present invention, as Figure 1 shown, preferably, a third pump P-3 is provided on the pipeline connecting the semi-lean liquid methanol outlet of the reabsorption tower T-4 and the second CO 2 absorption section to pressurize the first stream of semi-lean liquid methanol 8-i and then reuse it in the second CO 2 absorption section.

[0099] In the present invention, as Figure 1 shown, preferably, a fourth pump P-4 is provided on the pipeline connecting the low-H 2 S methanol outlet of the reabsorption tower T-4 and the upper part of the CO 2 flash section to pressurize the low-H 2 S methanol 20 and then perform the second washing.

[0100] The present invention will be described in detail below with reference to embodiments.

[0101] Embodiment 1

[0102] A low-temperature and low-sulfur syngas purification device for a coal water slurry gasification device, as Figure 1 shown, the device includes: H 2 S absorption tower T-1, CO 2 absorption tower T-2, primary CO 2 flash tank V-1, primary H 2 S flash tank V-2, secondary flash tower T-3 and reabsorption tower T-4, first cooler E-1, second cooler E-2, third cooler E-3, fourth cooler E-4 and fifth cooler E-5, and first pump P-1, second pump P-2, third pump P-3 and fourth pump P-4;

[0103] H 2 S absorption tower T-1 includes a first H 2 S absorption section provided at the bottom and a second H 2 S absorption section provided at the top; CO 2 absorption tower T-2 includes a first CO 2 absorption section provided at the bottom and a second CO 2 absorption section provided at the top; the secondary flash tower T-3 includes a CO 2 flash section provided at the top and an H 2 S flash section provided at the bottom, and the upper part of the CO 2 flash section and the upper part of the H 2 S flash section are connected by a pipeline.

[0104] A low-temperature and low-sulfur syngas purification method for a coal water slurry gasification device, the method includes:

[0105] Mixing syngas 1 (the molar content of H 2 S is 0.9 - 1.2%, the molar content of CO 2 is 40 - 50%; the temperature is -15 to -5 °C, the pressure is 5.2 - 5.7 MPa (G)) and the first rich H 2 S methanol 3-i in a molar flow ratio of 70 - 80:1 for countercurrent contact and performing the first H 2 S absorption to obtain the second rich H 2 S methanol 2 (the molar content of H 2 S is 0.2 - 0.4%, the molar content of CO 2 is 70 - 75%) and the pre-washed syngas; successively contacting the above-mentioned pre-washed syngas with low-sulfur rich-carbon methanol 4 (pressurized to 5.6 - 6 MPa (G) for the first time), the first rich CO 2 methanol 6-i for countercurrent contact and performing the second H2 S is absorbed to obtain desulfurized gas 5 (H 2 The molar content of S is 0.5 - 1 ppm, and that of CO 2 is 38 - 42%; the temperature is -20 to -10 °C; the pressure is 5.3 - 5.4 MPa(G)) and the first rich H 2 S methanol 3 (CO 2 has a molar content of 38 - 42%, and that of H 2 S is 1.5 - 1.8%; the temperature is -10 to -5 °C, and the pressure is 5.2 - 5.5 MPa(G));

[0106] Among them, the molar flow ratio of syngas 1 to low - sulfur rich - carbon methanol 4 is 5 - 7:1; the molar flow ratio of syngas 1 to the first rich CO 2 methanol 6 - i is 2 - 3:1;

[0107] The above - mentioned desulfurized gas 5 and CO - containing 2 methanol 7 (cooled to -36 to -33 °C in the fourth stage) are in counter - current contact at a molar flow ratio of 1:1.1 - 1.3 and undergo the first CO 2 absorption to obtain rich CO 2 methanol 6 (CO 2 has a molar content of 31 - 35%, and that of H 2 S is 0.1 - 0.5 ppm; the temperature is -15 to -10 °C, and the pressure is 5.2 - 5.4 MPa(G)) and pre - purified gas. Among them, the rich CO 2 methanol 6 is divided into the first rich CO 2 methanol 6 - i and the second rich CO 2 methanol 6 - ii at a molar flow ratio of 1:1.8 - 2.3; the first rich CO 2 methanol 6 - i is pressurized to 5.8 - 6 MPa(G) in the second stage, cooled to -35 to -25 °C in the third stage, and then sent to the second H 2 S absorption section; the above - mentioned pre - purified gas is successively in counter - current contact with the first semi - lean methanol 8 - i (pressurized to 5.6 - 6 MPa(G) in the third stage), lean methanol 9 (CO 2 has a molar content of 0%, and that of H 2 S is 0%) and undergoes the second CO 2 absorption to obtain purified gas 10 (H 2 The molar content of S ≤ 0.1 ppm, and that of CO 2 ≤ 20 ppm; the temperature is -55 to -50 °C, and the pressure is 5.1 - 5.3 MPa(G));

[0108] Among them, the molar flow rate ratio of the purified gas 10 to the first semi-lean methanol 8-i is 1.4 - 1.6:1; the molar flow rate ratio of the purified gas 10 to the lean methanol 9 is 1:1 - 1.1;

[0109] The second rich CO 2 After the methanol 6-ii is cooled to -36 to -33 °C in the fifth stage, it undergoes primary CO 2 flash evaporation (pressure is 3.5 - 3.7 MPa(G)), obtaining the rich CO 2 methanol 11 after primary flash evaporation (the molar content of H 2 S is 0.1 - 0.5 ppm, and the molar content of CO 2 is 30.5 - 34.5%; the temperature is -36.5 to -33.5 °C) and the primary CO 2 flash vapor 12-i (temperature is -36.5 to -33.5 °C; pressure is 3.5 - 3.7 MPa(G)); after the second rich H 2 S methanol 3-ii is cooled to -33 to -30 °C in the second stage, it undergoes primary H 2 S flash evaporation (pressure is 3.5 - 3.7 MPa(G)), obtaining the rich H 2 S methanol 16 after primary flash evaporation (the molar content of H 2 S is 1.5 - 1.7%, and the molar content of CO 2 is 37.5 - 41.5%; the temperature is -33.5 to -30.5 °C) and the primary H 2 S flash vapor 12-ii (temperature is -33.5 to -30.5 °C, pressure is 3.5 - 3.7 MPa(G)); mixing the above primary CO 2 flash vapor 12-i and primary H 2 S flash vapor 12-ii, obtaining the primary flash vapor 12 (the molar content of H 2 is 70 - 74%, the molar content of CO 2 is 24 - 29%, and the molar content of CO is 0.4 - 0.8%).

[0110] The rich CO 2 methanol 11 after primary flash evaporation undergoes secondary CO 2 flash evaporation (pressure is 1.6 - 2 MPa(G)), obtaining the rich CO 2 methanol 13 after flash evaporation (the molar content of H 2 S is 0.1 - 0.5 ppm, and the molar content of CO 2 is 30 - 34%; the temperature is -37 to -34 °C) and the secondary CO 2 flash vapor; the rich H 2 S methanol 16 after primary flash evaporation undergoes secondary H 2S flashing (at a pressure of 1.6 - 2 MPa(G)) to obtain the H-rich after flashing 2 S methanol 17 (H 2 The molar content of S is 1.5 - 1.8%, and the molar content of CO 2 is 37 - 41%; the temperature is -34 to -31 °C) and secondary H 2 S flash gas;

[0111] The H-rich CO 2 methanol 13 after the above flashing is divided into the first H-rich CO 2 methanol 13-i and the second H-rich CO 2 methanol 13-ii with a molar flow rate ratio of 3.5 - 4:1. Among them, the first H-rich CO 2 methanol 13-i undergoes the first flashing (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 22 - 25%, H 2 with a molar content of S ≤ 0.5 ppm; the temperature is -66 to -60 °C; the pressure is 0.05 - 0.08 MPa(G)). Among them, the above semi-lean methanol 8 is divided into the first semi-lean methanol 8-i and the second semi-lean methanol 8-ii with a molar flow rate ratio of 1.4 - 1.6:1; the second H-rich CO 2 methanol 12-ii is first cooled to -55 to -50 °C and then undergoes the second flashing (at a pressure of 0.06 - 0.09 MPa(G)) to obtain the second CO 2 product gas and the solution after flashing; the H-rich S 2 methanol 17 undergoes the third flashing (at a pressure of 0.12 - 0.16 MPa(G)) to obtain the sulfur-containing gas phase and the third H-rich S 2 methanol 19 (H 2 with a molar content of S of 1.5 - 1.7%, and the molar content of CO 2 is 27 - 30%; the temperature is -68 to -65 °C; the pressure is 0.13 - 0.17 MPa(G)); the above sulfur-containing gas phase and the solution after flashing are subjected to the first washing to obtain the third CO 2 product gas and low-H 2 S methanol 20 (H 2 with a molar content of S of 0.8 - 1.2%, and the molar content of CO 2 is 28 - 32%; the temperature is -65 to -60 °C, and the pressure is 0.12 - 0.16 MPa(G));

[0112] Among them, the above low-H 2 S methanol 20 is pressurized to 1.6 - 2 MPa(G) for the fourth time and then mixed with secondary CO2 The flash steam is subjected to a second washing to obtain secondary flash steam-I 14-i (temperature: -65°C to -60°C, pressure: 1.6 - 2 MPa(G)) and low-sulfur methanol 15; the low-sulfur methanol 15 and secondary H 2 S flash steam are subjected to a third washing to obtain secondary flash steam-II 14-ii (temperature: -65°C to -60°C, pressure: 1.6 - 2 MPa(G)) and low-sulfur carbon-rich methanol 4 (H 2 molar content of S is ≤1%, CO 2 molar content is 28 - 32%; temperature: -63 to -60°C); the above-mentioned secondary flash steam-I 14-i and secondary flash steam-II 14-ii are mixed to obtain secondary flash steam 14 (H 2 molar content is 80 - 85%, CO 2 molar content is 15 - 19%, molar content of CO is 0.05 - 0.15%);

[0113] Among them, the above-mentioned first CO 2 product gas, second CO 2 product gas and third CO 2 product gas are mixed to obtain CO 2 product gas 18 (H 2 molar content of S < 1 ppm, CO 2 molar content is 99.4 - 99.7%; temperature: -68°C to -64°C, pressure 0.05 - 0.08 MPa(G)).

[0114] Comparative Example 1

[0115] Taking a hydrogen production device using coal water slurry gasification as an example, the effective gas (H 2 +CO) entering the low-temperature methanol washing device is 230000 Nm 3 / h. Based on this benchmark, the main technical parameters are compared with those of the lean liquid - semi-lean liquid process (i.e., a low-temperature methanol washing process disclosed in CN201110260570.0) in Table 1.

[0116] Table 1

[0117]

[0118] It can be seen from the results in Table 1 that taking the hydrogen production device based on coal water slurry gasification as an example, for the low-temperature low-sulfur syngas purification method for the supporting coal water slurry gasification device provided in Example 1, the lean methanol circulation volume is 91.1% of the lean methanol circulation volume in Comparative Example 1 (lean liquid - semi-lean liquid process), and the semi-lean liquid methanol circulation volume is 90.7% of the semi-lean liquid methanol circulation volume in Comparative Example 1 (lean liquid - semi-lean liquid process), H 2 in the S absorption tower, rich in CO2 The methanol consumption is 84.2% of that in Comparative Example 1 (lean solution - semi-lean solution process) for rich CO 2 The cumulative reduction of external cooling consumption is 600 KW / h, and the overall energy-saving effect is remarkable.

[0119] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within 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 technical features. 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 method for purifying low-temperature, low-sulfur syngas from a coal-water slurry gasification device, characterized in that: The method comprises: The synthesis gas is subjected to H2S absorption to obtain first H2S-rich methanol and desulfurized gas; the desulfurized gas is subjected to CO2 absorption to obtain CO2-rich methanol, which is divided into two streams; the second stream of CO2-rich methanol is subjected to primary CO2 flash evaporation and secondary CO2 flash evaporation in sequence to obtain flashed CO2-rich methanol, which is divided into two streams, the first stream of flashed CO2-rich methanol is subjected to a first flash evaporation to obtain semi-lean liquid methanol, and the second stream of flashed CO2-rich methanol is subjected to a second flash evaporation after a first cooling; The first H2S-rich methanol is divided into two streams, and the second H2S-rich methanol is subjected to a primary H2S flash evaporation and a secondary H2S flash evaporation in sequence after a second cooling, and the flashed H2S-rich methanol obtained is subjected to a third flash evaporation, and the sulfur-containing gas phase obtained is subjected to a first washing with the flashed solution obtained by the second flash evaporation to obtain low H2S methanol; wherein the first H2S-rich methanol, the first CO2-rich methanol and the low-sulfur carbon-rich methanol are each independently returned and subjected to the H2S absorption, and the low-sulfur carbon-rich methanol is obtained by contacting the low H2S methanol with the flash gas of the secondary CO2 flash evaporation and the secondary H2S flash evaporation in sequence.

2. The method according to claim 1, wherein: The H2S absorption process comprises: contacting the synthesis gas with a first stream of H2S-rich methanol and performing a first H2S absorption to obtain a pre-washed synthesis gas and a second H2S-rich methanol; contacting the pre-washed synthesis gas, low-sulfur carbon-rich methanol and the first stream of CO2-rich methanol and performing a second H2S absorption to obtain the first H2S-rich methanol and desulfurized gas; 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, dividing the first H2S-rich methanol into a first stream of H2S-rich methanol and a second stream of H2S-rich methanol at a molar flow ratio of 1:50-60; and / or, the molar content of CO2 in the first H2S-rich methanol is 38-42%, the molar content of H2S is 1.5-1.8%; the temperature is -10 to -5°C, and the pressure is 5.2-5.5MPa(G); and / or, the molar flow ratio of the low-sulfur and carbon-rich methanol to the synthesis gas is 1:5-7; 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 0.5-1ppm, the molar content of CO2 is 38-42%; the temperature is -20 to -10°C; the pressure is 5.3-5.4MPa(G); Preferably, the low-sulfur and carbon-rich methanol is first pressurized to 5.6-6 MPa(G) and then returned to perform the second H2S absorption; Preferably, according to the material flow direction, the first stream of CO2-rich methanol is sequentially pressurized to 5.8-6 MPa (G) and cooled to -35 to -25°C for the second time, and then returned to perform the second H2S absorption.

3. The method according to claim 1 or 2, wherein: The semi-lean methanol is divided into two streams, and the first stream of the semi-lean methanol is returned to perform the CO2 absorption; And / or, the CO2 absorption process includes: contacting the desulfurized gas with CO2-containing methanol and performing a first CO2 absorption to obtain the CO2-rich methanol and pre-purified gas; The pre-purified gas, the first stream of semi-lean liquid methanol and the lean methanol are contacted and subjected to a second CO2 absorption to obtain purified gas and the CO2-containing methanol; and / or, the molar content of CO2 in the CO2-rich methanol is 31-35%, the molar content of H2S is 0.1-0.5 ppm; the temperature is -15 to -10°C, and the pressure is 5.2-5.4 MPa(G); and / or, dividing the CO2-rich methanol into a first stream of CO2-rich methanol and a second stream of CO2-rich methanol at a molar flow ratio of 1:1.8-2.3; and / or, the molar content of H2S in the purified gas is ≤0.1ppm, the molar content of CO2 is ≤20ppm; the temperature is -55 to -50°C, and the pressure is 5.1-5.3MPa(G); Preferably, the CO2-containing methanol is cooled to -36 to -33°C for the fourth time and then returned to the first CO2 absorption process; Preferably, the first stream of semi-lean methanol is pressurized to 5.6-6 MPa (G) for the third time and then returned to perform the second CO2 absorption.

4. The method according to any one of claims 1 to 3, wherein: The pressure of the first-stage CO2 flash evaporation is greater than the pressure of the second-stage CO2 flash evaporation; And / or, the pressure of the first-stage CO2 flash evaporation is 3.5-3.7 MPa(G); the pressure of the second-stage CO2 flash evaporation is 1.6-2 MPa(G); And / or, the process of the primary CO2 flash evaporation includes: subjecting the second stream of CO2-rich methanol to the primary CO2 flash evaporation to obtain primary CO2 flash gas and CO2-rich methanol after the primary flash evaporation; the process of the secondary CO2 flash evaporation includes: subjecting the CO2-rich methanol after the primary flash evaporation to the secondary CO2 flash evaporation to obtain secondary CO2 flash gas and CO2-rich methanol after the flash evaporation; Preferably, the temperature of the primary CO2 flash gas is -36.5 to -33.5°C; the pressure is 3.5-3.7 MPa(G); Preferably, the molar content of H2S in the CO2-rich methanol after the first-stage flash is 0.1-0.5 ppm, and the molar content of CO2 is 30.5-34.5%; the temperature is -36.5 to -33.5°C; and / or, before the first CO2 flash, the second stream of CO2-rich methanol is subjected to a fifth cooling to -36 to -33°C; 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 30-34%; the temperature is -37 to -34°C.

5. The method according to any one of claims 1 to 4, wherein: The temperature of the material after the second cooling is -33 to -30°C; and / or, the pressure of the first-stage H2S flash evaporation is greater than the pressure of the second-stage H2S flash evaporation; And / or, the pressure of the first-stage H2S flash evaporation is 3.5-3.7 MPa(G); the pressure of the second-stage H2S flash evaporation is 1.6-2 MPa(G); And / or, the process of the primary H2S flash evaporation includes: subjecting the second stream of H2S-rich methanol to the primary H2S flash evaporation after the second cooling to obtain primary H2S flash gas and H2S-rich methanol after the primary flash evaporation; the process of the secondary H2S flash evaporation includes: subjecting the H2S-rich methanol after the primary flash evaporation to the secondary H2S flash evaporation to obtain secondary H2S flash gas and H2S-rich methanol after the flash evaporation; Preferably, the temperature of the primary H2S flash gas is -33.5 to -30.5°C and the pressure is 3.5-3.7 MPa(G); Preferably, the molar content of H2S in the H2S-rich methanol after the first-stage flash is 1.5-1.7%, and the molar content of CO2 is 37.5-41.5%; the temperature is -33.5 to -30.5°C; And / or, the molar content of H2S in the H2S-rich methanol after the flash evaporation is 1.5-1.8%, the molar content of CO2 is 37-41%; the temperature is -34 to -31°C.

6. The method according to any one of claims 1 to 5, wherein: The flashed CO2-rich methanol is divided into the first flashed CO2-rich methanol and the second flashed CO2-rich methanol with a molar flow ratio of 3.5-4.5:1; And / or, the temperature of the first cooled material is -55 to -50°C; 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); 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 first 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 first cooled material 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; and / or, the molar content of CO2 in the semi-lean methanol is 22-25%, the molar content of H2S is ≤0.5ppm; the temperature is -66 to -60°C; the pressure is 0.05-0.08MPa(G); and / or, dividing the semi-lean methanol into a first stream of semi-lean methanol and a second stream of semi-lean methanol at a molar flow ratio of 1.4-1.6:1; and / or, the molar content of H2S in the low H2S methanol is 0.8-1.2%, the molar content of CO2 is 28-32%; the temperature is -65 to -60°C, and the pressure is 0.12-0.16MPa(G); Preferably, the molar content of H2S in the third H2S-rich methanol is 1.5-1.7%, the molar content of CO2 is 27-30%; the temperature is -68 to -65°C; the pressure is 0.13-0.17 MPa(G); And / or, the first CO2 product gas obtained by the first flash evaporation, the second CO2 product gas obtained by the second flash evaporation and the third CO2 product gas obtained by the first washing are mixed to obtain a CO2 product gas with a molar content of H2S less than 1ppm and a molar content of CO2 of 99.4-99.7%; a temperature of -66°C to -64°C, and a pressure of 0.05-0.08MPa(G).

7. The method according to any one of claims 1 to 6, wherein: The low-H2S methanol and the secondary CO2 flash gas obtained by flashing are subjected to a second washing to obtain low-sulfur methanol and secondary flash gas-I; the low-sulfur methanol and the secondary H2S flash gas obtained by flashing are subjected to a third washing to obtain the low-sulfur carbon-rich methanol and secondary flash gas-II; and / or, the molar content of H2S in the low-sulfur and carbon-rich methanol is ≤1%, the molar content of CO2 is 28-32%; the temperature is -63 to -60°C; Preferably, the low H2S methanol is pressurized to 1.6-2 MPa(G) for the fourth time, returned and subjected to the second washing; Preferably, the molar content of H2S in the low-sulfur methanol is ≤1%, the molar content of CO2 is 27-31%; the temperature is -65 to -60°C; Preferably, the temperature of the secondary flash gas-I is -65°C to -60°C, and the pressure is 1.6-2MPa(G); Preferably, the temperature of the secondary flash gas-II is -65°C to -60°C, and the pressure is 1.6-2 MPa(G).

8. A low-temperature, low-sulfur synthesis gas purification device supporting a water-coal slurry gasification device, characterized in that: The device comprises: a connected H2S absorption tower, a CO2 absorption tower, a primary CO2 flash tank, a primary H2S flash tank, a secondary flash tower and a reabsorption tower, as well as a first cooler and a second cooler; the secondary flash tower comprises a CO2 flash section arranged on the top and a H2S flash section arranged on the bottom, and the upper part of the CO2 flash section and the upper part of the H2S flash section are connected by a pipeline; The synthesis gas enters the H2S absorption tower for H2S absorption, and the obtained desulfurized gas enters the CO2 absorption tower for CO2 absorption. The obtained CO2-rich methanol is divided into two streams. The second stream of CO2-rich methanol enters the primary CO2 flash tank and the lower part of the CO2 flash section in sequence, and performs primary CO2 flash evaporation and secondary CO2 flash evaporation respectively. The obtained CO2-rich methanol after flash evaporation is divided into two streams. The first stream of CO2-rich methanol after flash evaporation enters the upper part of the reabsorption tower for the first flash evaporation to obtain semi-lean liquid methanol. The second stream of CO2-rich methanol after flash evaporation passes through the first cooler and enters the middle part of the reabsorption tower for the second flash evaporation. The first H2S-rich methanol obtained by the H2S absorption is divided into two streams, and the second H2S-rich methanol passes through the second cooler and then enters the first-stage H2S flash tank and the lower part of the H2S flash section in sequence, and respectively undergoes the first-stage H2S flash evaporation and the second-stage H2S flash evaporation, and the flashed H2S-rich methanol obtained enters the lower part of the reabsorption tower for the third flash evaporation, and the obtained sulfur-containing gas phase and the flashed solution obtained by the second flash evaporation are subjected to the first washing to obtain low-H2S methanol; Among them, the low H2S methanol enters the upper part of the CO2 flash section, and is subjected to a second washing with the secondary CO2 flash gas obtained by the secondary CO2 flash distillation. The obtained low-sulfur methanol enters the upper part of the H2S flash section, and is subjected to a third washing with the secondary H2S flash gas obtained by the secondary H2S flash distillation to obtain low-sulfur carbon-rich methanol; the first stream of H2S-rich methanol, the first stream of CO2-rich methanol and the low-sulfur carbon-rich methanol are independently recycled 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 to the first H2S absorption stage; Preferably, the first stream of CO2-rich methanol and low-sulfur carbon-rich methanol are independently recycled to the second H2S absorption stage; And / or, the CO2 absorption tower includes a first CO2 absorption section disposed at the bottom and a second CO2 absorption section disposed at the top, and the lower part of the second CO2 absorption section is connected to the upper part of the first CO2 absorption section.

10. The device according to claim 9, wherein: A first pump is provided on the pipeline connecting the upper part of the H2S flash section and the second H2S absorption section; And / or, according to the material flow direction, a second pump and a third cooler are sequentially arranged on the pipeline connecting the CO2-rich methanol outlet of the CO2 absorption tower and the second H2S absorption section, so as to return the first stream of CO2-rich methanol to the second H2S absorption section after the second pressurization and the third cooling; and / or, a fourth cooler is provided on the pipeline connecting the second CO2 absorption section and the first CO2 absorption section according to the material flow direction; And / or, a fifth cooler is provided on the pipeline connecting the CO2-rich methanol outlet of the CO2 absorption tower and the primary CO2 flash tank, for cooling the second stream of CO2-rich methanol through the fifth cooling device before performing the primary CO2 flashing; And / or, a third pump is provided on the pipeline connecting the semi-lean liquid methanol outlet of the reabsorption tower and the second CO2 absorption section, for recycling the first stream of semi-lean liquid methanol to the second CO2 absorption section after the third pressurization; And / or, a fourth pump is provided on the pipeline connecting the low H2S methanol outlet of the reabsorption tower and the upper portion of the CO2 flash section.

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