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

Abstract

The invention discloses a low-temperature low-sulfur methanol washing technology matched with a coal water slurry gasification device. 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. By optimizing the medium-pressure flash evaporation process, the method has the advantages that only a second stream of CO2-rich methanol is flashed in first-stage flash evaporation, first-stage flash evaporation gas does not need to be washed, the flash evaporation gas pressure is high and the like; in the second-stage flash evaporation, the semi-barren solution methanol is used for washing, the low H2S semi-barren solution methanol generated by washing can be continuously used, and the method also has the advantages of high use efficiency of the low H2S methanol and the low H2S semi-barren solution methanol and low comprehensive energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature methanol washing, and particularly relates to a low-temperature and low-sulfur methanol washing method for a coal water slurry gasification device and a low-temperature and low-sulfur methanol washing device 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 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 flashing. The typical process flow mainly has 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 and optimization 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 flashing, 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 generate and make full use of low-sulfur methanol is the direction and key factor of technological innovation. Specifically, it is necessary to achieve that before the thermal regeneration of the low-sulfur methanol, its absorption of H 2 S gas in the syngas reaches the upper limit, so as to reduce the amount of rich H 2 S-containing methanol that needs to be thermally regenerated and reduce the overall energy consumption of the low-temperature methanol washing process flow.

[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 rich CO 2Methanol is used to wash the syngas, and the low-sulfur methanol solution existing in the system is not studied and recycled, allowing it to undertake part of the potential of absorbing H 2 S gas in the syngas. Because the methanol dissolved with H 2 S gas needs to be regenerated in the thermal regeneration system before it can be recycled, so the energy consumption is relatively high; second, in the CO 2 flashing section of the reabsorption tower, the CO 2 rich 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, which is generally not conducive to reducing the comprehensive energy consumption of the cold methanol washing unit. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above technical problems, and provide a low-temperature and low-sulfur methanol washing method for a supporting water coal gasification device and a low-temperature and low-sulfur methanol washing device for a supporting water coal gasification device. By optimizing the medium-pressure flashing process, this method has the advantages that only the second rich CO 2 methanol is flashed in the first-stage flashing, the first-stage flash gas does not need to be washed, and the flash gas pressure is high; in the second-stage flashing, semi-lean methanol is used for washing, and the low-H 2 S semi-lean methanol generated by washing can be used continuously. This method also has the advantages of high utilization efficiency of low-H 2 S methanol and low-H 2 S semi-lean methanol and low comprehensive energy consumption.

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

[0008] Performing H 2 S absorption on the syngas to obtain the first rich H 2 S methanol and the desulfurized gas; performing CO 2 absorption on the desulfurized gas, and dividing the obtained rich CO 2 methanol into two streams. The first stream of rich CO 2 methanol returns and performs the above-mentioned H 2 S absorption, and the second stream of rich CO 2 methanol undergoes the first-stage CO 2 flashing to obtain the rich CO 2 methanol after the first-stage flashing. After the first cooling, it undergoes the second-stage CO 2 flashing to obtain the rich CO 2 methanol after flashing, which is divided into two streams. The first stream of rich CO 2 methanol after flashing undergoes the first flashing to obtain semi-lean methanol, which is divided into two streams. The second stream of rich CO 2 methanol after flashing undergoes the second cooling and then the second flashing;

[0009] After the first rich H 2 S methanol is cooled for the third time, H 2 S flash evaporation is carried out, and the rich H 2 S methanol after flash evaporation is subjected to a third flash evaporation, and the sulfur-containing gas phase obtained and the solution after flash evaporation obtained from the second flash evaporation are subjected to a first washing, and the low H 2 S methanol returns and undergoes the H 2 S absorption;

[0010] Among them, the first semi-lean methanol is divided into A-share semi-lean methanol, B-share semi-lean methanol and C-share semi-lean methanol, and they are respectively returned to the CO 2 absorption, secondary CO 2 flash evaporation and H 2 S flash evaporation; among them, the C-share semi-lean methanol and the H 2 H 2 S flash vapor obtained from S flash evaporation is subjected to a second washing, and the low H 2 S semi-lean methanol returns and undergoes 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, and the device includes: an H 2 S absorption tower, a CO 2 absorption tower, a first-stage medium-pressure flash evaporation tower, a second-stage medium-pressure flash evaporation tower and a re-absorption tower, as well as a first cooler, a second cooler and a third cooler; the second-stage medium-pressure flash evaporation tower includes a CO 2 flash evaporation section arranged on the upper part and an H 2 S flash evaporation section arranged on the lower part;

[0012] The syngas enters the H 2 S absorption tower for H 2 S absorption, and the first rich H 2 S methanol and desulfurized gas are obtained; the desulfurized gas enters the CO 2 absorption tower for CO 2 absorption, and the obtained rich CO 2 methanol is divided into two streams, the first stream of rich CO 2 methanol is recycled and used in the H 2 S absorption tower, and the second stream of rich CO 2 methanol enters the first-stage medium-pressure flash evaporation tower for first-stage CO 2 flash evaporation, and the obtained rich CO 2 methanol after the first-stage flash evaporation enters the CO 2 flash evaporation section after passing through the first cooler for second-stage CO 2 flash evaporation, and the obtained rich CO 2 methanol after flash evaporation is divided into two streams, the first stream of rich CO2 Methanol enters the upper part of the reabsorption tower for the first flash evaporation. The semi-lean methanol obtained is divided into two streams. After the second flash evaporation, the rich CO 2 After passing through the second cooler, methanol enters the middle part of the reabsorption tower for the second flash evaporation;

[0013] The first rich H 2 S methanol enters the H 2 S flash evaporation section for H 2 S flash evaporation. The rich H 2 S methanol enters the lower part of the reabsorption tower for the third flash evaporation. The sulfur-containing gas phase obtained and the flashed solution obtained from the second flash evaporation are subjected to the first washing. The low H 2 S methanol is recycled and used in the H 2 S absorption tower;

[0014] Among them, the first stream of semi-lean methanol is divided into stream A semi-lean methanol, stream B semi-lean methanol, and stream C semi-lean methanol, and they are respectively recycled and used in the CO 2 absorption tower, CO 2 flash evaporation section, and H 2 S flash evaporation section; among them, in the H 2 S flash evaporation section, the H 2 S flashed by the H 2 S flash vapor and stream C semi-lean methanol are subjected to the second washing. The low H 2 S semi-lean methanol is recycled and used in the 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 adopts a two-stage medium-pressure flash evaporation process. In the first stage, only the second stream of rich CO 2 methanol is flashed. The flash evaporation pressure is relatively high, and the effective gas flashed out is directly sent to the compression process without washing, which can reduce the power consumption of the compressor; in the second stage, the rich CO 2 methanol after the first flash evaporation and the first rich H 2 S methanol are flashed simultaneously, and the second flash evaporation pressure is relatively low, ensuring that their effective gases are flashed out thoroughly and sent to the fuel gas pipeline network for use as fuel gas;

[0017] At the same time, stream B semi-lean methanol is used to wash the CO 2 flash vapor obtained from the second-stage CO 2 flash evaporation. Compared with the prior art, while reducing the CO 2 component in the CO 2 flash vapor, it is not contaminated by the rich H 2 S methanol; stream C semi-lean methanol is used to wash the H 2 flash vapor obtained from the H 2The S flash vapor is washed. Compared with the prior art, while reducing the H 2 in the S flash vapor, the CO 2 component is not contaminated by the rich H 2 S methanol; thus, after the first flash, the separate flashing and separate washing of the rich CO 2 methanol and the first rich H 2 S methanol are realized, avoiding the technical problem that the CO 2 in the flash vapor is transferred to the rich H 2 S methanol after flashing. At the same time, the low H 2 S semi-lean methanol after washing is reused, which is beneficial to reducing the energy consumption of the device; 2

[0018] (2) The present invention also optimizes the reabsorption process, realizing the absorption of the sulfur-containing gas phase generated by the third flash by the flashed solution obtained by the second flash, obtaining low H(2) The present invention also optimizes the reabsorption process, realizing the absorption of the sulfur-containing gas phase generated by the third flash by the flashed solution obtained by the second flash, obtaining low H 2 S methanol, but not mixing with the third rich H 2 S methanol after flashing;

[0019] (3) In the H 2 S absorption process of the present invention, by introducing low H 2 S methanol and low H 2 S semi-lean methanol to jointly absorb the H 2 S and CO 2 gases in the syngas, realizing the recycling of low H 2 S methanol and low H 2 S semi-lean methanol, reducing the usage amount of the first rich CO 2 methanol in the H 2 S absorption, which is equivalent to reducing the first rich H 2 S methanol that needs to be thermally regenerated; at the same time, by pre-absorbing the CO 2 gas in the syngas with low H 2 S methanol and low H 2 S semi-lean methanol, the subsequent CO 2 absorption work load is correspondingly reduced, and the diameter of the CO 2 absorption tower is reduced. Brief Description of the Drawings

[0020] Figure 1 Figure is a schematic structural diagram of a low-temperature and low-sulfur methanol washing device supporting a water coal gasification device provided by the present invention.

[0021] Description of the Reference Numerals in the Drawings

[0022] T-1, H 2 S absorption tower; T-2, CO 2Absorption tower; T-3, primary medium-pressure flash tower; T-4, secondary medium-pressure 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;

[0023] 1. Synthesis gas; 2. Low-H 2 S methanol; 2-i. First stream of low-H 2 S methanol; 2-ii. Second stream of low-H 2 S methanol; 3. Second H-rich 2 S methanol; 4. First H-rich 2 S 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-lean methanol; 8-i. First stream of semi-lean methanol; 8-ii. Second stream of semi-lean methanol; 8-i-A. A-stream of semi-lean methanol; 8-i-B. B-stream of semi-lean methanol; 8-i-C. C-stream of semi-lean methanol; 9. Lean methanol; 10. Purified gas; 11. CO-rich after primary flash 2 Methanol; 12. Primary 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. First stream of secondary flash gas; 14-ii. Second stream of secondary flash gas; 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 semi-lean methanol. Detailed implementation mode

[0024] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the values between the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values 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.

[0025] In the present invention, without special instructions, "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.

[0026] In the present invention, without special instructions, 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.

[0027] The first aspect of the present invention provides a low-temperature and low-sulfur methanol washing method for a supporting coal water slurry gasification device, and the method includes:

[0028] Subject the syngas to H 2 S absorption to obtain first rich H 2 S methanol and desulfurized gas; subject the desulfurized gas to CO 2 absorption, and divide the obtained rich CO 2 methanol into two streams. The first stream of rich CO 2 methanol returns and is subjected to the above-mentioned H 2 S absorption, and the second stream of rich CO 2 methanol undergoes primary CO 2 flashing to obtain the rich CO 2 methanol after primary flashing. After being cooled by the first cooling, it undergoes secondary CO 2 flashing to obtain the rich CO 2 methanol after flashing. Divide the rich CO 2 methanol after flashing into two streams. The first stream of rich CO 2 methanol after flashing undergoes first flashing to obtain semi-lean liquid methanol divided into two streams. The second stream of rich CO

[0029] methanol after flashing is cooled by the second cooling and then undergoes second flashing; 2 Subject the first rich H 2 S methanol to H 2 S flashing after being cooled by the third cooling. The obtained rich H 2 S methanol after flashing undergoes third flashing to obtain a sulfur-containing gas phase, and the obtained flashing solution after the second flashing undergoes first washing to obtain low H 2 S methanol returns and is subjected to the above-mentioned H

[0030] Among them, the first semi-lean methanol is divided into A-share semi-lean methanol, B-share semi-lean methanol and C-share semi-lean methanol, and they are respectively returned to the CO 2 absorption, secondary CO 2 flashing and H 2 S flashing; among them, the C-share semi-lean methanol and the H 2 S vapor obtained by S flashing are subjected to a second washing to obtain low-H 2 S semi-lean methanol, which is returned and subjected to the above-mentioned H 2 S absorption. 2

[0031] In some embodiments of the present invention, preferably, the H 2 S absorption includes: first H 2 S absorption and second H 2 S absorption; among them, the process of the first H 2 S absorption includes: contacting the syngas with the first stream of low-H 2 S methanol and performing the first H 2 S absorption to obtain pre-washed syngas and second rich-H 2 S methanol; the process of the second H 2 S absorption includes: sequentially contacting the pre-washed syngas with the second stream of low-H 2 S methanol, low-H 2 S semi-lean 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.

[0032] In the present invention, the low-H 2 S methanol is divided into two streams, the first stream is subjected to the first H 2 S absorption, and the second stream is subjected to the second H 2 S absorption. Preferably, the low-H 2 S methanol is divided into the first stream of low-H 2 S methanol and the second stream of low-H 2 S methanol with a molar flow rate ratio of 1:13-15.

[0033] 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).

[0034] 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.​

[0035] In some embodiments of the present invention, preferably, the molar flow rate ratio of the syngas to the first stream of low-H 2 S methanol is 70-80:1.

[0036] In the present invention, the first H 2 S absorption is intended 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 2-4%, and the molar content of CO 2 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).

[0037] In some embodiments of the present invention, preferably, the molar flow rate ratio of the syngas to the second stream of low-H 2 S methanol is 5-6:1.

[0038] In some embodiments of the present invention, preferably, the molar flow rate ratio of the syngas to the low-H 2 S semi-lean methanol is 17-19:1.

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

[0040] In the present invention, the second H 2 S absorption is intended to further remove H 2 S in the syngas, as well as a small amount of CO 2 . Preferably, the molar content of H 2 S in the first rich-H 2 S methanol is 1.25-1.55%, and the molar content of CO 2 is 35-40%; the temperature is -20 to -10 °C; the pressure is 5.3-5.4 MPa(G).

[0041] 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 36-40%; the temperature is -20 to -10 °C; the pressure is 5.3-5.4 MPa(G).

[0042] In some embodiments of the present invention, preferably, the low-H2 After the methanol is pressurized to 5.8 - 6 MPa(G) for the first time, it is divided into two streams and returned for the said H 2 S absorption.

[0043] In a specific embodiment of the present invention, the low H 2 After the methanol is pressurized to 5.8 - 6 MPa(G) for the first time, it is divided into a first stream of low H 2 methanol and a second stream of low H 2 methanol with a molar flow rate ratio of 1:13 - 15.

[0044] In some embodiments of the present invention, preferably, in the direction of material flow, the first stream of CO 2 methanol is successively pressurized to 5.8 - 6 MPa(G) for the second time, cooled to -35 to -25 °C for the fourth time, and then returned for the said H 2 S absorption.

[0045] In some embodiments of the present invention, preferably, the low H 2 methanol of semi-lean liquid is pressurized to 5.8 - 6 MPa(G) for the fourth time and then returned for the said H 2 S absorption.

[0046] In some embodiments of the present invention, preferably, the CO 2 absorption includes: the first CO 2 absorption and the second CO 2 absorption; wherein, the process of the first CO 2 absorption includes: bringing the desulfurized gas into contact with the CO 2 methanol and performing the first CO 2 absorption to obtain the CO 2 rich methanol and the pre-purified gas; the process of the second CO 2 absorption includes: successively bringing the pre-purified gas into contact with the A-share semi-lean liquid methanol and the lean methanol and performing the second CO 2 absorption to obtain the purified gas and the CO 2 methanol.

[0047] In some embodiments of the present invention, preferably, the CO 2 rich methanol is divided into the first stream of CO 2 rich methanol and the second stream of CO 2 rich methanol with a molar flow rate ratio of 1:2 - 2.3.

[0048] In the present invention, the first CO 2 absorption aims to further remove CO 2 from the desulfurized gas. Preferably, the CO 2 in the CO2 The molar content is 30 - 33%, H 2 The molar content of S is 0.1 - 0.5 ppm; the temperature is -15 to -10 °C, and the pressure is 5.2 - 5.4 MPa(G).

[0049] In some embodiments of the present invention, preferably, the molar flow ratio of the desulfurized gas to the CO-containing 2 methanol is 1:1.2 - 1.4.

[0050] In some embodiments of the present invention, preferably, after the CO-containing 2 methanol is cooled to -36 to -33 °C in the fifth cooling, the first CO 2 absorption is carried out.

[0051] In some embodiments of the present invention, preferably, the molar flow ratio of the purified gas to the A-share semi-lean methanol is 1.4 - 1.6:1.

[0052] In some embodiments of the present invention, preferably, the molar flow ratio of the purified gas to the lean methanol is 1:1.1 - 1.2. In the present invention, the lean methanol comes from the subsequent process, and the molar content of H 2 S in the lean methanol is 0%, and the CO 2 molar content is 0%.

[0053] In some embodiments of the present invention, preferably, the molar content of H 2 S in the purified gas is ≤0.1 ppm, and the CO 2 molar content is ≤20 ppm; the temperature is -55 to -50 °C, and the pressure is 5.2 - 5.3 MPa(G).

[0054] In the present invention, the process of the first-stage CO 2 flashing includes: flashing the second rich CO 2 methanol for the first-stage CO 2 flashing to obtain the rich CO 2 methanol after the first-stage flashing and the first-stage flash gas.

[0055] In some embodiments of the present invention, preferably, the pressure of the first-stage CO 2 flashing is 3.5 - 3.7 MPa(G).

[0056] In some embodiments of the present invention, preferably, the molar content of H 2 S in the rich CO 2 methanol after the first-stage flashing is 0.1 - 0.5 ppm, and the CO 2 molar content is 29.5 - 32.5%; the temperature is -15.5 to -10.5 °C.

[0057] In some embodiments of the present invention, preferably, the primary CO 2 The molar content of H in the primary flash gas obtained by flash evaporation is 2 53 - 58%, the molar content of CO 2 is 40 - 45%, and the molar content of CO is 0.5 - 0.9%; the temperature is -15.5 to -10.5 °C.

[0058] In the present invention, the first cooling is achieved by reducing the temperature of the CO-rich 2 methanol after primary flash evaporation, aiming to reduce the total amount of medium-pressure flash gas and lay a foundation for obtaining low temperature (high-quality cold energy) for the reabsorption tower. Preferably, the temperature of the material after the first cooling is -36 to -33 °C.

[0059] In some embodiments of the present invention, preferably, the process of the secondary CO 2 flash evaporation includes: subjecting the material after the first cooling to secondary CO 2 flash evaporation to obtain the CO-rich 2 methanol after flash evaporation, and the obtained CO 2 flash gas and the B-stream semi-lean methanol are subjected to a third washing to obtain the first stream of secondary flash gas.

[0060] In the present invention, unless otherwise specified, the CO-rich 2 methanol after flash evaporation also includes the washing liquid obtained after the third washing.

[0061] In some embodiments of the present invention, preferably, the pressure of the secondary CO 2 flash evaporation < the pressure of the primary CO 2 flash evaporation; more preferably, the pressure of the secondary CO 2 flash evaporation is 1.6 - 2 MPa(G).

[0062] In some embodiments of the present invention, preferably, the molar content of H 2 S in the CO-rich 2 methanol after flash evaporation is 0.1 - 0.5 ppm, and the molar content of CO 2 is 29 - 32%; the temperature is -36.5 to -33.5 °C.

[0063] In some embodiments of the present invention, preferably, the CO-rich 2 methanol after flash evaporation 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 3 - 4:1.

[0064] In the present invention, the third cooling is achieved by reducing the first H-rich2 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 column. Preferably, the temperature of the material after the third cooling is -33 to -30 °C.

[0065] In some embodiments of the present invention, preferably, the H 2 The process of H2S flash evaporation includes: subjecting the material after the third cooling to H2S 2 flash evaporation to obtain the H2S-rich methanol after flash evaporation, and the H2S 2 flash gas obtained is subjected to the second washing with the C-stream semi-lean methanol to obtain the low-H2S 2 semi-lean methanol and the second stream of secondary flash gas. 2 Semi-lean methanol and the second stream of secondary flash gas.

[0066] In some embodiments of the present invention, preferably, the H2S 2 flash evaporation pressure is 1.6 - 2 MPa (G).

[0067] In some embodiments of the present invention, preferably, the molar content of H2S in the H2S-rich methanol after flash evaporation is 1.3 - 1.5%, and the molar content of CO2 is 35 - 40%; the temperature is -33.5 to -30.5 °C. 2 The molar content of H2S in 2 the H2S-rich methanol is 1.3 - 1.5%, and the molar content of CO2 is 35 - 40%; the temperature is -33.5 to -30.5 °C. 2 is 35 - 40%; the temperature is -33.5 to -30.5 °C.

[0068] In some embodiments of the present invention, preferably, the molar content of H2S in the low-H2S 2 semi-lean methanol is < 0.1%, and the molar content of CO2 is 24 - 26%; the temperature is -53 to -48 °C. 2 The molar content of H2S in 2 the low-H2S semi-lean methanol is < 0.1%, and the molar content of CO2 is 24 - 26%; the temperature is -53 to -48 °C.

[0069] In some embodiments of the present invention, preferably, the first stream of secondary flash gas and the second stream of secondary flash gas are mixed, and the temperature of the obtained secondary flash gas is -65 °C to -60 °C, the pressure is 1.6 - 2 MPa (G), and it is sent to the fuel gas pipeline network.

[0070] In some embodiments of the present invention, preferably, the pressure of the first flash evaporation < the pressure of the second flash evaporation < the pressure of the third flash evaporation.

[0071] In some embodiments of the present invention, preferably, the process of the first flash evaporation includes: subjecting the first stream of CO2-rich methanol after flash evaporation to the first flash evaporation to obtain the semi-lean methanol and the first CO2 2 product gas. 2 product gas.

[0072] In some embodiments of the present invention, preferably, the pressure of the first flash evaporation is 0.05 - 0.08 MPa(G).

[0073] In the present invention, the semi-lean methanol is divided into two streams. Preferably, the semi-lean methanol is divided into a first stream of semi-lean methanol and a second stream of semi-lean methanol with a molar flow rate ratio of 2.2 - 2.5:1. In the present invention, the second stream of semi-lean methanol is sent to subsequent processes for use.

[0074] In the present invention, the first stream of semi-lean methanol is divided into three streams. Stream A returns and undergoes CO 2 absorption; Stream B returns to the secondary CO 2 flash evaporation, and undergoes a third wash with the CO 2 flash vapor to obtain a first stream of secondary flash vapor; Stream C returns to the H 2 S flash evaporation, and undergoes a second wash with the H 2 S flash vapor to obtain a second stream of secondary flash vapor and low-H 2 S semi-lean methanol.

[0075] In some embodiments of the present invention, preferably, the first stream of semi-lean methanol is divided into the Stream A semi-lean methanol, Stream B semi-lean methanol, and Stream C semi-lean methanol with a molar flow rate ratio of 13 - 15:1:1.5 - 2.5.

[0076] In some embodiments of the present invention, preferably, after the first stream of semi-lean methanol is pressurized to 5.6 - 5.8 MPa(G) for the third time, it is divided into the Stream A semi-lean methanol, Stream B semi-lean methanol, and Stream C semi-lean methanol.

[0077] In a specific embodiment of the present invention, after the first stream of semi-lean methanol is pressurized to 5.6 - 5.8 MPa(G) for the third time, it is divided into the Stream A semi-lean methanol, Stream B semi-lean methanol, and Stream C semi-lean methanol with a molar flow rate ratio of 13 - 15:1:1.5 - 2.5.

[0078] In some embodiments of the present invention, preferably, the molar content of CO 2 in the semi-lean methanol is 18 - 22%, the molar content of H 2 S is ≤0.5 ppm; the temperature is -64 to -61 °C; the pressure is 0.05 - 0.08 MPa(G).

[0079] In the present invention, the second cooling reduces the temperature of the CO-rich methanol after the second flash evaporation, aiming to generate low temperature through pressure reduction flash evaporation and improve the absorption capacity of the flash liquid of the CO-rich methanol after flash evaporation for H 2 S gas, which is beneficial for washing the CO after flash evaporation 2 in the methanol, 2 ​2 H in the product gas 2 S gas. Preferably, the temperature of the material after the second cooling is -55 to -50 °C.

[0080] In some embodiments of the present invention, preferably, the process of the second flash evaporation includes: subjecting the material after the second cooling to a second flash evaporation to obtain a flashed solution and a second CO 2 Product gas.

[0081] In some embodiments of the present invention, preferably, the pressure of the second flash evaporation is 0.06 - 0.09 MPa(G).

[0082] In some embodiments of the present invention, preferably, the process of the third flash evaporation includes: subjecting the flashed rich H 2 S methanol to a third flash evaporation to obtain a sulfur-containing gas phase and a third rich H 2 S methanol, wherein the sulfur-containing gas phase and the flashed solution are subjected to the first washing to obtain the low H 2 S methanol and a third CO 2 Product gas.

[0083] In some embodiments of the present invention, preferably, the pressure of the third flash evaporation is 0.12 - 0.16 MPa(G).

[0084] In some embodiments of the present invention, preferably, the low H 2 The molar content of H in S methanol 2 S is 0.5 - 1%, and the molar content of CO 2 is 25 - 28%; the temperature is -65 to -60 °C, and the pressure is 0.12 - 0.16 MPa(G).

[0085] In some embodiments of the present invention, preferably, the low H 2 S methanol is divided into a first low H with a molar flow ratio of 1:13 - 15 2 S methanol and a second low H 2 S methanol.

[0086] In some embodiments of the present invention, preferably, the molar content of H in the third rich H 2 S in methanol 2 S is 1.3 - 1.5%, and the molar content of CO 2 is 25 - 29%; the temperature is -69 to -65 °C; the pressure is 0.13 - 0.17 MPa(G).

[0087] In some embodiments of the present invention, preferably, the first CO 2 Product gas, second CO 2Product gas and third CO 2 are mixed with the product gas to obtain CO 2 in the product gas, the molar content of H 2 S is < 1 ppm, and the molar content of CO 2 is 99.4 - 99.7%; the temperature is -65°C to -63°C, and the pressure is 0.05 - 0.08 MPa(G).

[0088] 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. It can be seen from Figure 1 that the device includes: an H 2 S absorption tower T-1, a CO 2 absorption tower T-2, a first-stage medium-pressure flash tower T-3, a second-stage medium-pressure flash tower T-4, and a reabsorption tower T-5, as well as a first cooler E-1, a second cooler E-2, and a third cooler E-3; the second-stage medium-pressure flash tower T-4 includes: a CO 2 flash section arranged on the upper part and an H 2 S flash section arranged on the lower part;

[0089] Synthesis gas 1 enters the H 2 S absorption tower T-1 for H 2 S absorption to obtain the first rich H 2 S methanol 4 and desulfurized gas 5; the desulfurized gas is sent into the CO 2 absorption tower T-2 for CO 2 absorption to obtain the rich CO 2 methanol 6, which is divided into two streams. The first stream of rich CO 2 methanol 6-i is recycled to the H 2 S absorption tower T-1, and the second stream of rich CO 2 methanol 6-ii enters the first-stage medium-pressure flash tower T-3 for the first-stage CO 2 flash to obtain the rich CO 2 methanol 11 after the first-stage flash. After passing through the first cooler E-1, it enters the CO 2 flash section for the second-stage CO 2 flash to obtain the rich CO 2 methanol 13 after the flash, which is divided into two streams. The first stream of rich CO 2 methanol 13-i enters the upper part of the reabsorption tower T-5 for the first flash to obtain the semi-lean liquid methanol 8, which is divided into two streams. The second stream of rich CO 2 methanol 13-ii enters the middle part of the reabsorption tower T-5 for the second flash after passing through the second cooler E-2;

[0090] The first rich H 2 S methanol 4 enters the H2 H is carried out in the S flash section 2 S flash is carried out to obtain the flashed rich H after flashing 2 S methanol 17 enters the lower part of the reabsorption tower T-5 for the third flash. The sulfur-containing gas phase obtained and the flashed solution obtained from the second flash are subjected to the first washing to obtain the low H 2 S methanol 2 is recycled for use in H 2 S absorption tower T-1;

[0091] Among them, the first semi-lean methanol 8-i is divided into A-share semi-lean methanol 8-i-A, B-share semi-lean methanol 8-i-B and C-share semi-lean methanol 8-i-C, and are respectively recycled for use in CO 2 absorption tower T-2, CO 2 flash section and H 2 S flash section;

[0092] Among them, H 2 In the S flash section, the H 2 H obtained by S flash 2 S flash gas and C-share semi-lean methanol 8-i-C are subjected to the second washing to obtain the low H 2 S semi-lean methanol 20 is recycled for use in H 2 S absorption tower T-1.

[0093] In the present invention, as Figure 1 shown, the H 2 S absorption tower T-1 includes a first H provided below 2 S absorption section and a second H provided above 2 S absorption section. Specifically, the first H 2 S absorption section, the first low H 2 S methanol 2-i pre-washes and absorbs H in the syngas 1 2 S, HCN, NH 3 ; the second H 2 S absorption section, by introducing the second low H 2 S methanol 2-ii and low H 2 S semi-lean methanol 20 absorbs H in the pre-washed syngas 2 S and CO 2 gas, realizing the recycling of low H 2 S methanol 2 and low H 2 S semi-lean methanol 20, reducing the usage amount of the first rich CO 2 methanol 6-i, which is equivalent to reducing the first rich H that needs to be thermally regenerated 2 S methanol; in addition, such a setting correspondingly reduces the working load of the subsequent CO 2 absorption tower, for reducing CO 2The usage amounts of lean methanol and semi-lean methanol in the absorption tower also have positive significance.

[0094] 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 riser holes; the first H 2 S absorption section is connected to the low H 2 S methanol outlet of the reabsorption tower T-5, for contacting the syngas 1 with the first stream of low H 2 S methanol 2-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 H 2 S semi-lean methanol outlet of the secondary medium-pressure flash tower T-4, and the rich CO 2 methanol outlet of the CO 2 absorption tower T-2, for sequentially contacting the pre-washed syngas with the second stream of low H 2 S methanol 2-ii, the low H 2 S semi-lean methanol 20, and the first stream of rich CO 2 methanol 6-i and performing the second H 2 S absorption to obtain the desulfurized gas 5 and the first rich H 2 S methanol 4.

[0095] In some embodiments of the present invention, preferably, in the H 2 S absorption tower T-1, the number of trays in the first H 2 S absorption section is 9-12, and the number of trays in the second H 2 S absorption section is 60-80.

[0096] In the present invention, without special description, in the first H 2 S absorption section, the contact mode between the syngas and the first stream of low H 2 S methanol 2-i is preferably countercurrent contact between the syngas 1 and the first stream of low H 2 S methanol 2-i, that is, the syngas 1 enters from the bottom of the first H 2 S absorption section, and the first stream of low H 2 S methanol 2-i enters from the upper part of the first H 2 S absorption section.

[0097] In the present invention, as Figure 1 shown, the CO 2The absorption tower T-2 includes a first CO absorption section provided at the lower part and a second CO absorption section provided at the upper part. Specifically, the first CO absorption section and the second CO absorption section are connected by riser holes. Among them, the upper part of the first CO absorption section is connected to the lower part of the second CO absorption section, which is used to contact the desulfurized gas 5 with the CO-containing methanol 7 and perform the first CO absorption to obtain the CO-rich methanol 6 and the pre-purified gas. The second CO 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-stage semi-lean liquid methanol 8-i-A and the lean methanol 9 in sequence and perform the second CO absorption to obtain the purified gas 10 and the CO-containing methanol 7. 2 The absorption tower T-2 includes a first CO absorption section provided at the lower part and a second CO absorption section provided at the upper part. 2 Specifically, the first CO absorption section and the second CO absorption section are connected by riser holes. 2 Among them, the upper part of the first CO absorption section is connected to the lower part of the second CO absorption section, which is used to contact the desulfurized gas 5 with the CO-containing methanol 7 and perform the first CO absorption to obtain the CO-rich methanol 6 and the pre-purified gas. 2 The second CO 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-stage semi-lean liquid methanol 8-i-A and the lean methanol 9 in sequence and perform the second CO absorption to obtain the purified gas 10 and the CO-containing methanol 7. 2 Among them, the upper part of the first CO absorption section is connected to the lower part of the second CO absorption section, which is used to contact the desulfurized gas 5 with the CO-containing methanol 7 and perform the first CO absorption to obtain the CO-rich methanol 6 and the pre-purified gas. 2 The second CO 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-stage semi-lean liquid methanol 8-i-A and the lean methanol 9 in sequence and perform the second CO absorption to obtain the purified gas 10 and the CO-containing methanol 7. 2 Among them, the upper part of the first CO absorption section is connected to the lower part of the second CO absorption section, which is used to contact the desulfurized gas 5 with the CO-containing methanol 7 and perform the first CO absorption to obtain the CO-rich methanol 6 and the pre-purified gas. 2 The second CO 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-stage semi-lean liquid methanol 8-i-A and the lean methanol 9 in sequence and perform the second CO absorption to obtain the purified gas 10 and the CO-containing methanol 7. 2 Among them, the upper part of the first CO absorption section is connected to the lower part of the second CO absorption section, which is used to contact the desulfurized gas 5 with the CO-containing methanol 7 and perform the first CO absorption to obtain the CO-rich methanol 6 and the pre-purified gas. 2 The second CO 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-stage semi-lean liquid methanol 8-i-A and the lean methanol 9 in sequence and perform the second CO absorption to obtain the purified gas 10 and the CO-containing methanol 7. 2 Among them, the upper part of the first CO absorption section is connected to the lower part of the second CO absorption section, which is used to contact the desulfurized gas 5 with the CO-containing methanol 7 and perform the first CO absorption to obtain the CO-rich methanol 6 and the pre-purified gas. 2 The second CO 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-stage semi-lean liquid methanol 8-i-A and the lean methanol 9 in sequence and perform the second CO absorption to obtain the purified gas 10 and the CO-containing methanol 7.

[0098] In some embodiments of the present invention, preferably, in the CO absorption tower T-2, the number of trays in the first CO absorption section is 12 - 18, and the number of trays in the second CO absorption section is 60 - 80. 2 In the CO absorption tower T-2, the number of trays in the first CO absorption section is 12 - 18, and the number of trays in the second CO absorption section is 60 - 80. 2 In the CO absorption tower T-2, the number of trays in the first CO absorption section is 12 - 18, and the number of trays in the second CO absorption section is 60 - 80. 2 In the CO absorption tower T-2, the number of trays in the first CO absorption section is 12 - 18, and the number of trays in the second CO absorption section is 60 - 80.

[0099] In the present invention, without special instructions, in the CO absorption tower T-2, for the first CO absorption section, the contact mode between the desulfurized gas 5 and the CO-containing methanol 7 is preferably countercurrent contact; that is, the desulfurized gas 5 enters from the bottom of the first CO absorption section, and the CO-containing methanol 7 enters from the upper part of the first CO absorption section. 2 In the present invention, without special instructions, in the CO absorption tower T-2, for the first CO absorption section, the contact mode between the desulfurized gas 5 and the CO-containing methanol 7 is preferably countercurrent contact; that is, the desulfurized gas 5 enters from the bottom of the first CO absorption section, and the CO-containing methanol 7 enters from the upper part of the first CO absorption section. 2 In the CO absorption tower T-2, for the first CO absorption section, the contact mode between the desulfurized gas 5 and the CO-containing methanol 7 is preferably countercurrent contact; that is, the desulfurized gas 5 enters from the bottom of the first CO absorption section, and the CO-containing methanol 7 enters from the upper part of the first CO absorption section. 2 In the CO absorption tower T-2, for the first CO absorption section, the contact mode between the desulfurized gas 5 and the CO-containing methanol 7 is preferably countercurrent contact; that is, the desulfurized gas 5 enters from the bottom of the first CO absorption section, and the CO-containing methanol 7 enters from the upper part of the first CO absorption section. 2 In the CO absorption tower T-2, for the first CO absorption section, the contact mode between the desulfurized gas 5 and the CO-containing methanol 7 is preferably countercurrent contact; that is, the desulfurized gas 5 enters from the bottom of the first CO absorption section, and the CO-containing methanol 7 enters from the upper part of the first CO absorption section. 2 In the CO absorption tower T-2, for the first CO absorption section, the contact mode between the desulfurized gas 5 and the CO-containing methanol 7 is preferably countercurrent contact; that is, the desulfurized gas 5 enters from the bottom of the first CO absorption section, and the CO-containing methanol 7 enters from the upper part of the first CO absorption section. 2 In the CO absorption tower T-2, for the first CO absorption section, the contact mode between the desulfurized gas 5 and the CO-containing methanol 7 is preferably countercurrent contact; that is, the desulfurized gas 5 enters from the bottom of the first CO absorption section, and the CO-containing methanol 7 enters from the upper part of the first CO absorption section. 2 In the CO absorption tower T-2, for the first CO absorption section, the contact mode between the desulfurized gas 5 and the CO-containing methanol 7 is preferably countercurrent contact; that is, the desulfurized gas 5 enters from the bottom of the first CO absorption section, and the CO-containing methanol 7 enters from the upper part of the first CO absorption section.

[0100] In the present invention, as shown, the first-stage medium-pressure flash tower T-3 is used to perform the first-stage CO flash evaporation on the second-stage CO-rich methanol 6-ii to obtain the first-stage flash-evaporated CO-rich methanol 11 and the first-stage flash gas 12. Figure 1 In the present invention, as shown, the first-stage medium-pressure flash tower T-3 is used to perform the first-stage CO flash evaporation on the second-stage CO-rich methanol 6-ii to obtain the first-stage flash-evaporated CO-rich methanol 11 and the first-stage flash gas 12. 2 In the present invention, as shown, the first-stage medium-pressure flash tower T-3 is used to perform the first-stage CO flash evaporation on the second-stage CO-rich methanol 6-ii to obtain the first-stage flash-evaporated CO-rich methanol 11 and the first-stage flash gas 12. 2 In the present invention, as shown, the first-stage medium-pressure flash tower T-3 is used to perform the first-stage CO flash evaporation on the second-stage CO-rich methanol 6-ii to obtain the first-stage flash-evaporated CO-rich methanol 11 and the first-stage flash gas 12. 2 In the present invention, as shown, the first-stage medium-pressure flash tower T-3 is used to perform the first-stage CO flash evaporation on the second-stage CO-rich methanol 6-ii to obtain the first-stage flash-evaporated CO-rich methanol 11 and the first-stage flash gas 12.

[0101] In the present invention, as shown, in the second-stage medium-pressure flash tower T-4, a CO flash evaporation section is provided at the upper part, which is used to perform the CO flash evaporation on the first-stage flash-evaporated CO-rich methanol. Figure 1 In the present invention, as shown, in the second-stage medium-pressure flash tower T-4, a CO flash evaporation section is provided at the upper part, which is used to perform the CO flash evaporation on the first-stage flash-evaporated CO-rich methanol. 2 In the present invention, as shown, in the second-stage medium-pressure flash tower T-4, a CO flash evaporation section is provided at the upper part, which is used to perform the CO flash evaporation on the first-stage flash-evaporated CO-rich methanol. 2After the methanol 11 is cooled for the first time, secondary CO 2 flash evaporation is carried out to obtain the CO-rich 2 methanol 13 and CO 2 flash gas after flash evaporation; an H 2 S flash section is provided below for the first H-rich 2 S methanol 4 to be cooled for the third time and then undergo H 2 S flash evaporation to obtain the H-rich 2 S methanol 17 and H 2 S flash gas after flash evaporation. Among them, the B-share semi-lean liquid methanol 8-i-B and CO 2 flash gas are subjected to the third washing to obtain the first secondary flash gas 14-i; the C-share semi-lean liquid methanol 8-i-C and H 2 S flash gas are subjected to the second washing to obtain the second secondary flash gas 14-ii and the low-H 2 S semi-lean liquid methanol 20.

[0102] In the present invention, as Figure 1 shown, the upper and middle parts of the reabsorption tower T-5 are connected through lifting holes, and the middle and lower parts are also connected through lifting holes. Specifically, the upper part is used for the first CO-rich 2 methanol 13-i after flash evaporation to undergo the first flash evaporation to obtain semi-lean liquid methanol 8 and the first CO 2 product gas; the middle part is used for the second CO-rich 2 methanol 13-ii after flash evaporation to be cooled for the second time and then undergo the second flash evaporation to obtain the flashed solution and the second CO 2 product gas; the lower part is used for the H-rich 2 S methanol 17 after flash evaporation to undergo the third flash evaporation to obtain the third H-rich 2 S methanol 17 and the sulfur-containing gas phase; among them, the sulfur-containing gas phase and the flashed solution are washed to obtain the low-H 2 S methanol 2 and the third CO 2 product gas; the CO 2 product gas 18 includes the first CO 2 product gas, the second CO 2 product gas, and the third CO 2 product gas.

[0103] In the present invention, as Figure 1 shown, the low-H 2 S methanol outlet of the reabsorption tower T-5 is respectively connected to the first H 2 S absorption section and the second H 2 S absorption section for dividing the low-H 2 S methanol 2 into two streams and respectively returning them for the first H 2 S absorption and the second H 2 S absorption.

[0104] In the present invention, as Figure 1 shown, the rich CO 2 methanol outlet of the CO 2 absorption tower T-2 is connected to the second H 2 S absorption section for returning the first stream of rich CO 2 methanol 6-i and performing the second H 2 S absorption.

[0105] In the present invention, as Figure 1 shown, in the CO 2 absorption tower T-2, the bottom of the second CO 2 absorption section is connected to the upper part of the first CO 2 absorption section for returning the CO 2 -containing methanol 7 and performing the first CO 2 absorption.

[0106] In the present invention, as Figure 1 shown, a first pump P-1 is provided on the pipeline connecting the low H 2 S methanol outlet of the reabsorption tower T-5 and the H 2 S absorption tower T-1 for dividing the low H 2 S methanol 2 into two streams after the first pressurization and recycling them respectively to the first H 2 S absorption section and the second H 2 S absorption section.

[0107] In the present invention, as Figure 1 shown, in the direction of material flow, a second pump P-2 and a fourth cooler E-4 are successively provided on the pipeline connecting the rich CO 2 methanol outlet of the absorption tower T-2 and the second H 2 S absorption section for successively subjecting the first stream of rich CO 2 methanol 6-i to second pressurization and fourth cooling and then returning it to perform the second H 2 S absorption. 2 S absorption.

[0108] In the present invention, as Figure 1 shown, in the direction of material flow, a fifth cooler E-5 is provided on the pipeline connecting the second CO 2 absorption section and the first CO 2 absorption section for cooling the CO 2 -containing methanol 7 by the fifth cooler and then returning it to perform the first CO 2 absorption.

[0109] In the present invention, as Figure 1 shown, the semi-lean liquid methanol outlet of the reabsorption tower T-5 is connected to the second CO2 Absorption section, CO 2 Flashing section and H 2 On the pipeline of the H2S flashing section, a third pump P-3 is provided, which is used to divide the first semi-lean methanol 8-i into the A-share semi-lean methanol 8-i-A, B-share semi-lean methanol 8-i-B and C-share semi-lean methanol 8-i-C after the third pressurization.

[0110] In the present invention, as Figure 1 shown, connecting the H 2 Low H2S semi-lean methanol outlet of the H2S flashing section and the second H 2 S absorption section, a fourth pump P-4 is provided on the pipeline, which is used to return the low H2S semi-lean methanol 20 after the fourth pressurization and perform the second H 2 S absorption. 2 S absorption. 2 S absorption.

[0111] The present invention will be described in detail below through embodiments.

[0112] Embodiment 1

[0113] The low-temperature and low-sulfur methanol washing device for a coal water slurry gasification device is as Figure 1 shown. It can be seen from Figure 1 that the device includes: H 2 S absorption tower T-1, CO 2 absorption tower T-2, first-stage medium-pressure flashing tower T-3, second-stage medium-pressure flashing 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, and first pump P-1, second pump P-2, third pump P-3 and fourth pump P-4;

[0114] H 2 S absorption tower T-1 includes a first H 2 S absorption section arranged at the bottom and a second H 2 S absorption section arranged at the top; 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; the second-stage medium-pressure flashing tower T-4 includes a CO 2 flashing section arranged at the top and an H 2 S flashing section arranged at the bottom.

[0115] The low-temperature and low-sulfur methanol washing method for a coal water slurry gasification device includes:

[0116] Feeding the syngas 1 (the molar content of H 2 S is 0.9-1.2%, CO 2The molar content is 40 - 50%; the temperature is -15 to -5 °C, and the pressure is 5.2 - 5.7 MPa(G)) and the first low-H 2 S methanol 2-i contacts countercurrently at a molar flow rate ratio of 70 - 80:1 and undergoes the first H 2 S absorption to obtain the second H-rich 2 S methanol 3 (H 2 The molar content of S is 2 - 4%, and the CO 2 The molar content is 70 - 75%) and the syngas after pre-washing;

[0117] The above-mentioned syngas after pre-washing is successively contacted with the second low-H 2 S methanol 2-ii, low-H 2 S semi-lean liquid methanol 20 (pressurized to 5.8 - 6 MPa(G) for the fourth time) and the first CO-rich 2 Methanol 6-i (pressurized to 5.8 - 6 MPa(G) for the second time and cooled to -35 to -25 °C for the fourth time) contacts countercurrently and undergoes the second H 2 S absorption to obtain the desulfurized gas 5 (H 2 The molar content of S is 0.5 - 1 ppm, and the CO 2 The molar content is 36 - 40%; the temperature is -20 to -10 °C; the pressure is 5.3 - 5.4 MPa(G)) and the first H-rich 2 S methanol 4 (H 2 The molar content of S is 1.25 - 1.55%, and the CO 2 The molar content is 35 - 40%; the temperature is -20 to -10 °C, and the pressure is 5.3 - 5.4 MPa(G));

[0118] Among them, the low-H 2 S methanol 2 is pressurized to 5.8 - 6 MPa(G) for the first time and then divided into the first low-H with a molar flow rate ratio of 1:11 - 13 2 S methanol 2-i and the second low-H 2 S methanol 2-ii; the molar flow rate ratio of the syngas 1 and the second low-H 2 S methanol 2-ii is 5 - 6:1; the molar flow rate ratio of the syngas 1 and the first CO-rich 2 Methanol 6-i is 2 - 3:1;

[0119] The above-mentioned desulfurized gas 5 and the CO-containing 2 Methanol 7 (cooled to -36 to -33 °C for the fifth time) contacts countercurrently at a molar flow rate ratio of 1:1.2 - 1.4 and undergoes the first CO 2 Absorption to obtain the CO-rich 2 Methanol 6 (CO 2 The molar content is 30 - 33%, and the H 2The molar content of S is 0.1 - 0.5 ppm; the temperature is -15 to -10 °C, the pressure is 5.2 - 5.4 MPa(G)) and the pre-purified gas, where the rich CO 2 The methanol 6 is divided into a first rich CO with a molar flow ratio of 1:2 - 2.3 2 Methanol 6-i and a second rich CO 2 Methanol 6-ii;

[0120] The above-mentioned pre-purified gas is successively counter-current contacted with A-stage semi-lean methanol 8-i-A and lean methanol 9 (CO 2 The molar content is 0%, H 2 The molar content of S is 0%) and a second CO absorption is carried out to obtain a purified gas 10 (H 2 The molar content of S < 0.1 ppm, CO 2 The molar content < 20 ppm; the temperature is -55 to -50 °C; the pressure is 5.2 - 5.3 MPa(G)) and the CO-containing methanol 7; 2 2

[0121] Among them, the molar flow ratio of the above-mentioned purified gas 10 to A-stage semi-lean methanol 8-i-A is 1.4 - 1.6:1; the molar flow ratio of the above-mentioned purified gas 10 to lean methanol 9 is 1:1.1 - 1.2;

[0122] The above-mentioned second rich CO 2 Methanol 6-ii is subjected to primary CO 2 Flashing (pressure is 3.5 - 3.7 MPa(G)) to obtain rich CO after primary flashing 2 Methanol 11 (H 2 The molar content of S is 0.1 - 0.5 ppm, CO 2 The molar content is 29.5 - 32.5%; the temperature is -15.5 to -10.5 °C) and primary flash gas 12;

[0123] The rich CO 2 Methanol 11 after the above primary flashing is cooled to -36 to -33 °C by the first cooler and then subjected to secondary CO 2 Flashing (pressure is 1.6 - 2 MPa(G)) to obtain rich CO after flashing 2 Methanol 13 (H 2 The molar content of S is 0.1 - 0.5 ppm, CO 2 The molar content is 29 - 32%; the temperature is 36.5 to -33.5 °C) and CO 2 Flash gas; the first rich H 2 S methanol 4 is cooled to -33 to -30 °C by the third cooler and then subjected to H 2 ​​S flashing (at a pressure of 1.6 - 2 MPa(G)) to obtain rich H after flashing 2 S methanol 17 (H 2 The molar content of S is 1.3 - 1.5%, and the molar content of CO 2 is 35 - 40%; the temperature is -33.5 to -30.5 °C) and H 2 S flash gas;

[0124] Divide the rich CO 2 methanol 13 after the above flashing into the first rich CO 2 methanol 13-i and the second rich CO 2 methanol 13-ii with a molar flow ratio of 3 - 4:1, where the first rich CO 2 methanol 13-i is subjected to 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 18 - 22%, H 2 with a molar content of S ≤ 0.5 ppm; the temperature is -64 to -61 °C; the pressure is 0.05 - 0.08 MPa(G)), where 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 ratio of 2.2 - 2.5:1; the second rich CO 2 methanol 13-ii is cooled to -55 to -50 °C and then subjected to the second flashing (at a pressure of 0.06 - 0.09 MPa(G)) to obtain the second CO 2 product gas and the flashed solution; the rich H 2 S methanol 17 is subjected to the third flashing (at a pressure of 0.12 - 0.16 MPa(G)) to obtain a sulfur-containing gas phase and the third rich H 2 S methanol 19 (H 2 with a molar content of S of 1.3 - 1.5%, and the molar content of CO 2 is 25 - 29%; the temperature is -69 to -65 °C; the pressure is 0.13 - 0.17 MPa(G)); the above sulfur-containing gas phase and the flashed solution 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 S of 0.5 - 1%, and the molar content of CO 2 is 25 - 28%; the temperature is -65 to -60 °C, and the pressure is 0.12 - 0.16 MPa(G));

[0125] Among them, the above first CO 2 product gas, the second CO 2 product gas and the third CO2 The product gas is mixed to obtain CO 2 The molar content of H 2 S in the product gas is < 1 ppm, and the molar content of CO 2 is 99.4 - 99.7%; the temperature is -68°C to -63°C, and the pressure is 0.05 - 0.08 MPa(G));

[0126] Among them, after the first semi-lean methanol 8-i is pressurized to 5.6 - 5.8 MPa(G) by the third stage, it is divided into A-share semi-lean methanol 8-i-A, B-share semi-lean methanol 8-i-B, and C-share semi-lean methanol 8-i-C with a molar flow ratio of 13 - 15:1:1.5 - 2.5, and they are respectively returned and subjected to the above-mentioned second CO 2 absorption, secondary CO 2 flashing and H 2 S flashing, among which, the B-share semi-lean methanol 8-i-B and CO 2 flashing gas are subjected to the third washing to obtain the first secondary flashing gas 14-i; the C-share semi-lean methanol 8-i-C and H 2 S flashing gas are subjected to the second washing to obtain the second secondary flashing gas 14-ii and low-H 2 S semi-lean methanol 20(H 2 The molar content of S is < 0.1%, and the molar content of CO 2 is 24 - 26%; the temperature is -53 to -48°C); the above-mentioned first secondary flashing gas 14-i and the second secondary flashing gas 14-ii are mixed to obtain the secondary flashing gas 14 (the composition includes H 2 with a molar content of 80 - 86%, CO 2 with a molar content of 12 - 17%, and the molar content of CO is 0.9 - 1.1%; the temperature is -65°C to -60°C, and the pressure is 1.6 - 2 MPa(G)) is pressurized to 5.8 - 6 MPa(G) by the fourth stage and then returned and subjected to the second H 2 S absorption.

[0127] Comparative Example 1

[0128] Taking the 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 of the lean-rich liquid process (i.e., CN201110260570.0 discloses a low-temperature methanol washing process) are compared as shown in Table 1.

[0129] Table 1

[0130]

[0131]

[0132] As can be seen from the results in Table 1, taking the hydrogen production unit based on coal water slurry gasification as an example, a low-temperature and low-sulfur methanol washing method for supporting a coal water slurry gasification unit provided in Example 1 has a lean methanol circulation rate of 90.4% of the lean methanol circulation rate in Comparative Example 1 (lean liquid - semi-lean liquid process), and the semi-lean liquid methanol circulation rate is 92.9% of the semi-lean liquid methanol circulation rate in Comparative Example 1 (lean liquid - semi-lean liquid process). The H 2 methanol usage in the rich CO 2 absorber is 86.3% of the rich CO 2 methanol usage in Comparative Example 1 (lean liquid - semi-lean liquid process). The diameter of the CO 2 absorber is reduced by 100 mm, and the cumulative reduction in external cooling consumption is 800 KW / h, showing a significant overall energy-saving effect.

[0133] 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 scope 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 to obtain first H2S-rich methanol and desulfurized gas; the desulfurized gas is subjected to CO2 absorption to obtain CO2-rich methanol, and the first CO2-rich methanol is returned and subjected to the H2S absorption, and the second CO2-rich methanol is subjected to a primary CO2 flash distillation, and the obtained CO2-rich methanol after the primary flash distillation is subjected to a first cooling and then subjected to a secondary CO2 flash distillation to obtain two CO2-rich methanol after flash distillation, and the first CO2-rich methanol after the flash distillation is subjected to a first flash distillation to obtain two semi-lean liquid methanol, and the second CO2-rich methanol after the flash distillation is subjected to a second cooling and then subjected to a second flash distillation; After the first H2S-rich methanol is subjected to a third cooling, H2S flashing is performed, the flashed H2S-rich methanol obtained is subjected to a third flashing, the sulfur-containing gas phase obtained and the flashed solution obtained by the second flashing are subjected to a first washing, and the obtained low-H2S methanol is returned and subjected to the H2S absorption; wherein the first stream of semi-lean methanol is divided into stream A of semi-lean methanol, stream B of semi-lean methanol and stream C of semi-lean methanol, which are returned to the CO2 absorption, secondary CO2 flash evaporation and H2S flash evaporation respectively; wherein the C stream of semi-lean methanol and the H2S flash gas obtained by the H2S flash evaporation are subjected to a second washing, and the obtained low-H2S semi-lean methanol is returned to undergo 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 a first stream of low H2S methanol and performing a first H2S absorption to obtain a pre-washed synthesis gas and a second H2S-rich methanol; the second H2S absorption process includes: contacting the pre-washed synthesis gas with a second stream of low H2S methanol, a low H2S semi-lean liquid methanol and a first stream of CO2-rich methanol in sequence and performing a second H2S absorption to obtain the first H2S-rich methanol and desulfurized gas; and / or, the low H2S methanol is divided into a first stream of low H2S methanol and a second stream of low H2S methanol at a molar flow ratio of 1:13-15; 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 content of H2S in the first H2S-rich methanol is 1.25-1.55%, the molar content of CO2 is 35-40%; the temperature is -20 to -10°C; the pressure is 5.3-5.4 MPa(G); And / or, the molar content of H2S in the desulfurized gas is 0.5-1 ppm, the molar content of CO2 is 36-40%; the temperature is -20 to -10°C; and the pressure is 5.3-5.4 MPa(G).

3. The method according to claim 1 or 2, wherein: The low H2S methanol is first pressurized to 5.8-6 MPa (G) and then divided into two streams, which are 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 low H2S semi-lean methanol is pressurized to 5.8-6 MPa(G) for the fourth time and then returned to perform the H2S absorption.

4. The method according to any one of claims 1 to 3, 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 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 the CO2-containing methanol; and / or, dividing the CO2-rich methanol into the first stream of CO2-rich methanol and the second stream of CO2-rich methanol at a molar flow ratio of 1:2-2.3; and / or, the molar content of CO2 in the CO2-rich methanol is 30-33%, 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); Preferably, the CO2-containing methanol is subjected to a fifth cooling to -36 to -33°C before the first CO2 absorption; Preferably, the molar flow ratio of the purified gas to the A-stream semi-lean methanol is 1.4-1.6:

1.

5. The method according to any one of claims 1 to 4, wherein: The pressure of the first-stage CO2 flash evaporation is 3.5-3.7MPa(G); and / or, the molar content of H2S in the CO2-rich methanol after the first-stage flash is 0.1-0.5 ppm, the molar content of CO2 is 29.5-32.5%; the temperature is -15.5 to -10.5°C; And / or, the temperature of the first cooled material is -36 to -33°C; And / or, the process of the secondary CO2 flash evaporation comprises: subjecting the first cooled material to secondary CO2 flash evaporation to obtain the flashed CO2-rich methanol, and subjecting the obtained CO2 flash gas and the B stream of semi-lean methanol to a third washing to obtain a first stream of secondary flash gas; and / or, the pressure of the secondary CO2 flash evaporation is less than the pressure of the primary CO2 flash evaporation; And / or, the pressure of the secondary 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 29-32%; the temperature is -36.5 to -33.5°C; And / or, the flashed CO2-rich methanol is divided into the first stream of flashed CO2-rich methanol and the second stream of flashed CO2-rich methanol with a molar flow ratio of 3-4:

1.

6. The method according to any one of claims 1 to 5, wherein: The temperature of the material after the third cooling is -33 to -30°C; And / or, the H2S flashing process comprises: performing H2S flashing on the third cooled material to obtain the flashed H2S-rich methanol, and performing the second washing on the obtained H2S flash gas and the C stream of semi-lean methanol to obtain the low-H2S semi-lean methanol and a second secondary flash gas; 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 1.3-1.5%, and the molar content of CO2 is 35-40%; the temperature is -33.5 to -30.5°C; And / or, the molar content of H2S in the low H2S semi-lean methanol is <0.1%, the molar content of CO2 is 24-26%; and the temperature is -53 to -48°C.

7. The method according to any one of claims 1 to 6, 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 first flash evaporation process includes: performing a first flash evaporation on the CO2-rich methanol after the first flash evaporation to obtain the semi-lean methanol and the first CO2 product gas; And / or, the pressure of the first flash evaporation is 0.05-0.08 MPa(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 2.2-2.5:1; and / or, dividing the first stream of semi-lean methanol into the A stream of semi-lean methanol, the B stream of semi-lean methanol and the C stream of semi-lean methanol at a molar flow ratio of 13-15:1:1.5-2.5; and / or, the first stream of semi-lean methanol is pressurized to 5.6-5.8 MPa(G) for a third time to separate into the A stream of semi-lean methanol, the B stream of semi-lean methanol and the C stream of semi-lean methanol; and / or, the molar content of CO2 in the semi-lean methanol is 18-22%, the molar content of H2S is ≤0.5ppm; the temperature is -64 to -61°C; the pressure is 0.05-0.08MPa(G); And / or, the temperature of the second cooled material is -55 to -50°C; And / or, the second flash evaporation process includes: performing a second flash evaporation on the second cooled material to obtain the flashed solution and a second CO2 product gas; And / or, the pressure of the second flash evaporation is 0.06-0.09 MPa(G); And / or, the third flash evaporation process comprises: subjecting the flashed H2S-rich methanol to a third flash evaporation to obtain a sulfur-containing gas phase and a third H2S-rich methanol, wherein the sulfur-containing gas phase and the flashed solution are subjected to the first washing to obtain the low-H2S methanol and a third CO2 product gas; And / or, the pressure of the third flash evaporation is 0.12-0.16 MPa(G); and / or, the molar content of H2S in the low H2S methanol is 0.5-1%, the molar content of CO2 is 25-28%; the temperature is -65 to -60°C, and the pressure is 0.12-0.16MPa(G); and / or, dividing the low H2S methanol into a first stream of low H2S methanol and a second stream of low H2S methanol at a molar flow ratio of 1:13-15; And / or, the first CO2 product gas, the second CO2 product gas and the third CO2 product gas are mixed, and the molar content of H2S in the obtained CO2 product gas is less than 1ppm, and the molar content of CO2 is 99.4-99.7%; the temperature is -65℃ to -63℃, and the pressure is 0.05-0.08MPa(G).

8. A low-temperature, low-sulfur methanol washing device supporting a water-coal slurry gasification device, characterized in that: The device comprises: an H2S absorption tower, a CO2 absorption tower, a first medium-pressure flash tower, a second medium-pressure flash tower and a reabsorption tower connected in sequence, as well as a first cooler, a second cooler and a third cooler; the second medium-pressure flash tower comprises a CO2 flash section arranged on the top and an H2S flash section arranged on the bottom; The synthesis gas enters the H2S absorption tower for H2S absorption to obtain the first H2S-rich methanol and the desulfurized gas; the desulfurized gas enters the CO2 absorption tower for CO2 absorption, and the obtained CO2-rich methanol is divided into two streams. The first stream of CO2-rich methanol is recycled back to the H2S absorption tower, and the second stream of CO2-rich methanol enters the first-level medium-pressure flash tower for the first-level CO2 flash evaporation. The obtained CO2-rich methanol after the first-level flash evaporation passes through the first cooler and then enters the CO2 flash section for the second-level CO2 flash evaporation. The obtained CO2-rich methanol after the flash evaporation is divided into two streams. The first stream of CO2-rich methanol after the flash evaporation enters the upper part of the reabsorption tower for the first flash evaporation. The obtained semi-lean liquid methanol is divided into two streams. The second stream of CO2-rich methanol after the flash evaporation passes through the second cooler and then enters the middle part of the reabsorption tower for the second flash evaporation. The first H2S-rich methanol passes through the third cooler and enters the H2S flash section for H2S flash evaporation. The flashed H2S-rich methanol enters the lower part of the reabsorption tower for the third flash evaporation. The sulfur-containing gas phase and the flashed solution obtained by the second flash evaporation are first washed. The low-H2S methanol is recycled to the H2S absorption tower. Among them, the first stream of semi-lean methanol is divided into stream A of semi-lean methanol, stream B of semi-lean methanol and stream C of semi-lean methanol, which are respectively recycled to the CO2 absorption tower, the CO2 flash section and the H2S flash section; wherein, in the H2S flash section, the H2S flash gas obtained by the H2S flash evaporation and stream C of semi-lean methanol are subjected to a second washing, and the obtained low-H2S semi-lean methanol is recycled to the H2S absorption tower.

9. The device according to claim 8, wherein: The H2S absorption tower comprises a first H2S absorption section arranged at the bottom and a second H2S absorption section arranged at the top; 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; Preferably, the low H2S methanol outlet of the reabsorption tower is connected to the first H2S absorption section and the second H2S absorption section respectively; Preferably, the CO2-rich methanol outlet of the CO2 absorption tower is connected to the second H2S absorption section; Preferably, in the CO2 absorption tower, the bottom of the second CO2 absorption section is connected to the upper part of the first CO2 absorption section.

10. The purification 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 H2S absorption tower, for dividing the low H2S methanol into two streams after the first pressurization, and circulating them back to the first H2S absorption section and the second H2S absorption section respectively; and / or, according to the material flow direction, a second pump and a fourth cooler are sequentially arranged on the pipeline connecting the CO2-rich methanol outlet of the CO2 absorption tower and the second H2S absorption section; and / or, a fifth 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 third pump is provided on the pipeline connecting the semi-lean liquid methanol outlet of the reabsorption tower with the second CO2 absorption section, the CO2 flash section and the H2S flash section, for separating the first stream of semi-lean liquid methanol into the A stream of semi-lean liquid methanol, the B stream of semi-lean liquid methanol and the C stream of semi-lean liquid methanol after the third pressurization; And / or, a fourth pump is provided on the pipeline connecting the low H2S semi-lean liquid methanol outlet of the H2S flash section and the second H2S absorption section.

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