Poly-generation acid gas removal process matched with coal water slurry gasification device

Abstract

The invention relates to the technical field of low-temperature methanol washing, in particular to a poly-generation acid gas removal method matched with a coal water slurry gasification device and a poly-generation acid gas removal device matched with the coal water slurry gasification device. The use amount of the first-stage CO2-rich methanol is reduced; the technical problem that CO2 gas is polluted by H2S gas in the medium-pressure flash evaporation process is solved by optimally setting the medium-pressure flash evaporation process and adopting a classified flash evaporation and classified washing technology; by optimally setting a medium-pressure flash evaporation process, low-sulfur carbon-rich methanol is generated, and meanwhile, the low-sulfur carbon-rich methanol is subjected to secondary utilization; by optimally arranging the gas stripping process of the re-absorption tower, the first semi-barren liquor methanol, the low H2S methanol, the second H2S-rich methanol and the first H2S-rich methanol are used for carrying out series absorption on the gas stripping gas, so that the method has the characteristic of low comprehensive energy consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-temperature methanol washing, in particular to a multi-production acid gas removal method matched with a coal water slurry gasification device and a multi-production acid gas removal device matched with a coal water slurry gasification device. BACKGROUND

[0002] H2 and CO in the synthesis gas produced by the coal water slurry gasification technology are called effective gas, and the synthesis gas also contains a large amount of CO2 and a small amount of H2S, COS, NH3, HCN and other components. Among them, H2 and CO are raw materials for synthesizing methanol, glycol and other chemical products after the hydrogen-carbon ratio is adjusted in the conversion unit, and the acid gases H2S and CO2 need to be removed before the synthesis process.

[0003] At present, the low-temperature methanol washing technology innovation research mainly focuses on the recycling of the reduced pressure flash of the CO2-rich methanol, and the typical process is the lean-liquid-semi-lean-liquid process. With the diversification of the demand for synthesis gas components in the downstream device, the multi-production acid gas removal technology has also developed vigorously, but there are still many technical deficiencies in the process design: first, how to effectively use the non-conversion H2S-rich methanol after the washing of the non-conversion gas in the multi-production technology still needs to be optimized; second, if the H2S absorption tower has fluctuations, H2S gas will enter the CO2 absorption tower with the desulfurization gas, which will pollute all the CO2-rich methanol in the operation of the entire acid gas device; third, the process setting of the medium-pressure flash tower is not reasonable enough, and there is a problem of secondary pollution of the CO2 gas flashed out by the H2S-rich methanol; fourth, the tail gas washing process setting of the reabsorption tower is not scientific and reasonable, and the gradient washing effect of the multi-stream sulfur-containing methanol is not fully utilized.

[0004] CN201110260570.0 discloses a low-temperature methanol washing process, which uses CO2-rich methanol to wash the synthesis gas in the H2S absorption tower, and the CO2-rich methanol is polluted while absorbing H2S gas, which increases the generation of H2S-rich methanol, and the H2S-rich methanol needs to be heat regenerated before being recycled, which is high in energy consumption; second, the CO2 gas flashed out from the upper tower of the medium-pressure flash tower is sent to the lower tower for washing and absorption by using H2S-rich methanol, which causes the CO2 gas to be transferred to the H2S-rich methanol, and the CO2 gas is also polluted; third, in the CO2 flashing section of the reabsorption tower, the CO2-rich methanol is directly mixed with the H2S-rich methanol while washing the H2S-rich methanol flash gas, and the CO2-rich methanol is polluted by the H2S-rich methanol, and the low-concentration H2S methanol produced is not fully used, which is high in energy consumption.

[0005] CN201810994082.4 discloses a low-temperature methanol washing system and a method for providing synthesis gas. The technology utilizes non-transformed H2S-rich methanol after washing of non-transformed gas, but only uses the H2S-rich methanol as flash gas after medium-pressure flashing to wash methanol, which is not fully efficient and still has room for improvement and energy consumption reduction. SUMMARY

[0006] The present application aims to overcome the low efficiency of using non-transformed H2S-rich methanol after washing of non-transformed gas in the existing poly-generation low-temperature methanol washing technology, and provides a poly-generation acid gas removal method for a coal water slurry gasification device and a poly-generation acid gas removal device for a coal water slurry gasification device. The method optimizes the H2S absorption process, uses low-sulfur carbon-rich methanol and non-transformed H2S-rich methanol to treat synthesis gas, and reduces the use of primary CO2-rich methanol. By optimizing the medium-pressure flashing process, the technology solves the technical problem of CO2 gas pollution by H2S gas in the medium-pressure flashing process through classified flashing and classified washing. By optimizing the medium-pressure flashing process, low-sulfur carbon-rich methanol is generated, and the low-sulfur carbon-rich methanol is used twice. By optimizing the reabsorption tower gas stripping process, the first semi-lean liquid methanol, low-H2S methanol, second H2S-rich methanol, and first H2S-rich methanol are used for series absorption of gas stripping gas, which has the characteristics of low comprehensive energy consumption.

[0007] To achieve the above-mentioned purpose, the first aspect of the present application provides a poly-generation acid gas removal method for a coal water slurry gasification device, which comprises:

[0008] The synthesis gas is subjected to two-stage H2S absorption to obtain primary H2S-rich methanol, secondary H2S-rich methanol, and desulfurized gas. The desulfurized gas is subjected to three-stage CO2 absorption to obtain primary CO2-rich methanol, secondary CO2-rich methanol, tertiary CO2-rich methanol, and purified gas. The first stock of secondary CO2-rich methanol is returned to the three-stage CO2 absorption, and the second stock of secondary CO2-rich methanol is subjected to CO2 flashing to obtain CO2 flashing gas and two stocks of CO2 flashing liquid. The secondary H2S-rich methanol is subjected to H2S flashing to obtain H2S flashing gas and H2S flashing liquid.

[0009] The first stock of CO2 flashing liquid, the second stock of CO2 flashing liquid, and the H2S flashing liquid are each independently subjected to first flashing, second flashing, and third flashing to obtain semi-lean liquid methanol, low-H2S methanol, first H2S-rich methanol, and CO2 product gas.

[0010] The semi-lean methanol is divided into three streams, the second stream of semi-lean methanol is returned to the third-stage CO2 absorption, and the third stream of semi-lean methanol is sequentially subjected to first washing with the CO2 flash gas and the H2S flash gas to obtain low-sulfur carbon-rich methanol which is returned to the two-stage H2S absorption;

[0011] The non-reformed H2S-rich methanol from the non-reformed gas purification process is divided into three streams, the first stream of non-reformed H2S-rich methanol is reused, the second stream of non-reformed H2S-rich methanol is returned to the two-stage H2S absorption, the third stream of non-reformed H2S-rich methanol is subjected to second washing with the washing gas obtained in the first washing to obtain second H2S-rich methanol, the first H2S-rich methanol, the third H2S-rich methanol and the low H2S methanol are each independently subjected to gas stripping to obtain post-gas stripping H2S-rich methanol, and the obtained gas stripping gas and the first stream of semi-lean methanol are subjected to third washing to obtain the third H2S-rich methanol.

[0012] The second aspect of the present application provides a multi-production acid gas removal device matched with a coal water slurry gasification device, the device comprising: connected non-reformed gas washing tower, H2S absorption tower, CO2 absorption tower, CO2 medium-pressure flash tower, H2S medium-pressure flash tower and reabsorption tower; the CO2 medium-pressure flash tower is divided into CO2 washing section and CO2 flash section which are communicated through a riser from top to bottom; the H2S medium-pressure flash tower is divided into second H2S washing section, first H2S washing section and H2S flash section which are communicated through a riser from top to bottom;

[0013] The non-reformed gas washing tower is used for two-stage purification of non-reformed gas, and the obtained non-reformed H2S-rich methanol is divided into three streams, the first stream of non-reformed H2S-rich methanol is recycled and used for the non-reformed gas washing tower, the second stream of non-reformed H2S-rich methanol is sent to the H2S absorption tower, and the third stream of non-reformed H2S-rich methanol is sent to the second H2S washing section;

[0014] The H2S absorption tower is used for two-stage H2S absorption of synthesis gas to obtain primary H2S-rich methanol, secondary H2S-rich methanol and desulfurized gas;

[0015] The CO2 absorption tower is used for three-stage CO2 absorption of the desulfurized gas to obtain primary CO2-rich methanol, secondary CO2-rich methanol, tertiary CO2-rich methanol and purified gas; wherein the primary CO2-rich methanol is reused for the H2S absorption tower, the secondary CO2-rich methanol is divided into two streams, and the first stream of secondary CO2-rich methanol and the tertiary CO2-rich methanol are each independently reused for the CO2 absorption tower;

[0016] The CO2 flash section is used for CO2 flashing of the second CO2-rich methanol, and the obtained CO2 flash gas enters the CO2 washing section, and the obtained CO2 flash liquid is divided into two streams; the H2S flash section is used for H2S flashing of the secondary H2S-rich methanol, and the obtained H2S flash gas enters the first H2S washing section, and the obtained H2S flash liquid is obtained;

[0017] The upper tower is divided into a first flash section, a second flash section and a third flash section from top to bottom and communicated through lift holes, and is used for first flashing, second flashing and third flashing of the first CO2 flash liquid, the second CO2 flash liquid and the H2S flash liquid respectively, to obtain semi-lean liquid methanol, low-H2S methanol, first H2S-rich methanol and CO2 product gas;

[0018] The semi-lean liquid methanol is divided into three streams, the second stream of semi-lean liquid methanol is used for the CO2 absorption tower, the third stream of semi-lean liquid methanol sequentially passes through the CO2 washing section and the first H2S washing section, and sequentially performs first washing with the CO2 flash gas and the H2S flash gas, and the obtained low-sulfur carbon-rich methanol is used for the H2S absorption tower, and the obtained washing gas enters the second H2S washing section and performs second washing with the third stream of non-shift H2S-rich methanol to obtain second H2S-rich methanol;

[0019] The lower tower of the reabsorption tower is divided into a washing section and a gas stripping section from top to bottom and communicated through lift holes, the gas stripping section is connected to the bottom of the washing section, the second H2S washing section, the second flash section and the third flash section, and is used for gas stripping of the third H2S-rich methanol, the second H2S-rich methanol, the low-H2S methanol and the first H2S-rich methanol respectively to obtain post-gas stripping H2S-rich methanol, and the obtained gas stripping gas enters the washing section and performs third washing with the first stream of semi-lean liquid methanol to obtain the third H2S-rich methanol used for the gas stripping section.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] (1) The method provided by the present application adopts four-stage tail gas washing technology, and selectively sets four streams of methanol with different H2S contents according to the different H2S contents in the tail gas, i.e., the first stream of semi-lean liquid methanol, the low-H2S methanol, the second H2S-rich methanol and the first H2S-rich methanol (especially the second heat-exchanged H2S-rich methanol), which are sequentially washed from high to low, to ensure that the tail gas emission meets the standard and the least semi-lean liquid methanol is used, thereby reducing the heat regeneration energy consumption of the entire low-temperature methanol washing;

[0022] (2) The method provided by the present application divides the non-shift H2S-rich methanol obtained by two-stage purification of the non-shift gas into three streams, wherein the second stream of the non-shift H2S-rich methanol is used as a pre-washing solvent to perform first H2S absorption on the synthesis gas, compared with the prior art using CO2-rich methanol, the use amount of the first CO2-rich methanol is reduced under the premise of obtaining the same washing effect, which is of positive significance to reduce the energy consumption of the low-temperature methanol washing device; meanwhile, the third stream of the non-shift H2S-rich methanol is sent into the H2S medium-pressure flash tower as a washing solvent, after the concentration of CO2 in the non-shift H2S-rich methanol is increased, nitrogen stripping is performed;

[0023] (3) The method provided by the present application, by optimizing the medium-pressure flash process, the third stream of the non-shift H2S-rich methanol is introduced to further wash the H2S flash gas, and the third stream of the semi-lean liquid methanol is introduced to wash the CO2 flash gas and the H2S flash gas in turn, compared with the prior art, the second stream of the second CO2-rich methanol and the second stream of the H2S-rich methanol are respectively flashed and washed, the technical problem of transferring CO2 gas into the H2S-rich methanol is avoided, and the device energy consumption is reduced;

[0024] (4) The method provided by the present application optimizes the reabsorption process, the absorption of the sulfur-containing gas phase (for example, H2S) in the third CO2 product gas generated by flashing the H2S flash liquid with the second stream of the CO2 flash liquid is realized, but the first H2S-rich methanol after flashing is not mixed with each other; therefore, the H2S content in the solution is lower after the sulfur-containing gas phase is absorbed by the flash liquid, and low-H2S methanol is obtained.

[0025] (5) The method provided by the present application optimizes the H2S absorption process, by introducing the low-sulfur carbon-rich methanol and the non-shift H2S-rich methanol to jointly absorb the H2S gas in the synthesis gas, the circulation use of the low-sulfur carbon-rich methanol and the non-shift H2S-rich methanol is realized, the use amount of the first CO2-rich methanol in the H2S absorption is reduced, and the second H2S-rich methanol which needs to be heat regenerated is equivalent to being reduced. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a kind of multi-production acid gas removal device structure schematic diagram provided by the present application for a complete water-coal slurry gasification device.

[0027] REFERENCE SIGNS

[0028] T-1, non-shift gas washing tower; T-2, H2S absorption tower; T-3, CO2 absorption tower; T-4, CO2 medium-pressure flash tower; T-5, H2S medium-pressure flash tower; T-6, reabsorption tower;

[0029] E-1, first cooler; E-2, second cooler; E-3, third cooler; E-4, fourth cooler; E-5, fifth cooler;

[0030] P-1, first pump; P-2, second pump; P-3, third pump;

[0031] Q-1, first heat exchanger; Q-2, second heat exchanger; Q-3, third heat exchanger;

[0032] 1, non-reformed gas; 2, lean methanol; 2-i, first lean methanol; 2-ii, second lean methanol; 3, non-reformed H2S-rich methanol; 3-i, first non-reformed H2S-rich methanol; 3-ii, second non-reformed H2S-rich methanol; 3-iii, third non-reformed H2S-rich methanol; 4, pre-purified non-reformed H2S-rich methanol; 5, purified non-reformed gas; 6, synthesis gas; 7, first H2S-rich methanol; 9, first CO2-rich methanol; 10, second H2S-rich methanol; 11, sweetened gas; 12, H2S flash liquid; 13, third CO2-rich methanol; 14, purified gas; 15, second H2S-rich methanol; 16, flash gas; 16-i, H2S flash gas after washing; 16-ii, CO2 flash gas after washing; 17, H2S-rich methanol after stripping; 18, nitrogen; 19, third H2S-rich methanol; 20, tail gas; 21, second CO2-rich methanol; 21-i, first second CO2-rich methanol; 21-ii, second second CO2-rich methanol; 22, first H2S-rich methanol; 23, CO2 flash liquid; 23-i, first CO2 flash liquid; 23-ii, second CO2 flash liquid; 24, carbon-rich methanol; 25, low-sulfur carbon-rich methanol; 26, CO2 product gas; 27, semi-lean liquid methanol; 27-i, first semi-lean liquid methanol; 27-ii, second semi-lean liquid methanol; 27-iii, third semi-lean liquid methanol; 28, low-H2S methanol; 29, CO2 flash liquid after heat exchange; 30, first H2S-rich methanol after heat exchange; 31, second H2S-rich methanol after heat exchange; 32, third H2S-rich methanol after heat exchange. DETAILED DESCRIPTION

[0033] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges and values should be construed to be approximations that allow for significant variation. Various ranges of values that are stated herein are considered to be approximate values that can vary by a small amount. It is thus understood that the endpoints of each of the ranges are not to be understood as being limited to the exact values stated, and are instead intended to show more or less, to indicate the ranges included overall, to the proper scope as is customary in the art. Likewise, any

[0034] In the present application, without special case description, "first", "second", "third", "fourth" and "fifth" neither represent the order of precedence, nor represent the limitation to each material or step, but are only used to distinguish that they are not the same material or step. For example, "first", "second" and "third" in "first pressurization", "second pressurization" and "third pressurization" are only used to represent that they are not the same pressurization; similarly, "first", "second" and "third" in "first non-reformed H2S-rich methanol", "second non-reformed H2S-rich methanol" and "third non-reformed H2S-rich methanol" are only used to represent that they are not the same non-reformed H2S-rich methanol.

[0035] In the present application, without special case description, "top" of a container refers to 0-10% of the height of the container from top to bottom; "upper part" of the container refers to 10-40% of the height of the container from top to bottom; "middle part" of the container refers to 40-60% of the height of the container from top to bottom; "lower part" of the container refers to 60-90% of the height of the container from top to bottom; and "bottom" of the container refers to 90-100% of the height of the container from top to bottom.

[0036] The first aspect of the present application provides a multi-production acid gas removal method matched with a coal water slurry gasification device, the method comprising:

[0037] The synthesis gas is subjected to two-stage H2S absorption to obtain first H2S-rich methanol, second H2S-rich methanol and desulfurized gas; the desulfurized gas is subjected to three-stage CO2 absorption to obtain first CO2-rich methanol which is returned to the two-stage H2S absorption, second CO2-rich methanol which is divided into two streams, third CO2-rich methanol which is reused, and purified gas; wherein the first stream of second CO2-rich methanol is returned to the three-stage CO2 absorption, and the second stream of second CO2-rich methanol is subjected to CO2 flashing to obtain CO2 flashing gas and CO2 flashing liquid which is divided into two streams; the second H2S-rich methanol is subjected to H2S flashing to obtain H2S flashing gas and H2S flashing liquid;

[0038] The first stream of CO2 flashing liquid, the second stream of CO2 flashing liquid and the H2S flashing liquid are each independently subjected to first flashing, second flashing and third flashing to obtain semi-lean liquid methanol, low-H2S methanol, first H2S-rich methanol and CO2 product gas;

[0039] The semi-lean liquid methanol is divided into three streams, the second stream of semi-lean liquid methanol is returned to the three-stage CO2 absorption, and the third stream of semi-lean liquid methanol is sequentially subjected to first washing with the CO2 flashing gas and the H2S flashing gas to obtain low-sulfur carbon-rich methanol which is returned to the two-stage H2S absorption;

[0040] The non-shift H2S-rich methanol from the non-shift gas purification process is divided into three streams, the first stream of non-shift H2S-rich methanol is reused, the second stream of non-shift H2S-rich methanol is returned to the two-stage H2S absorption, the third stream of non-shift H2S-rich methanol is subjected to a second washing with the scrubbing gas obtained from the first washing to obtain second H2S-rich methanol, the first H2S-rich methanol, the third H2S-rich methanol and the low H2S methanol are independently subjected to stripping to obtain post-stripping H2S-rich methanol, and the stripping gas obtained and the first stream of semi-lean liquid methanol are subjected to a third washing to obtain the third H2S-rich methanol.

[0041] In the present application, the synthesis gas and the non-shift gas are both derived from a coal slurry gasification device, unless otherwise specified.

[0042] In some embodiments of the present application, preferably, the non-shift gas washing process comprises: contacting the non-shift gas, the first stream of non-shift H2S-rich methanol and the first stream of lean methanol from a subsequent process and performing two-stage purification to obtain pre-purified non-shift H2S-rich methanol, purified non-shift gas and the non-shift H2S-rich methanol.

[0043] In some embodiments of the present application, preferably, the two-stage purification comprises a first purification and a second purification; and further preferably, the first stream of non-shift H2S-rich methanol is returned to the first purification.

[0044] In some embodiments of the present application, further preferably, the non-shift gas and the first stream of non-shift H2S-rich methanol are subjected to the first purification to obtain the pre-purified non-shift H2S-rich methanol and pre-purified non-shift gas; and the pre-purified non-shift gas and the first stream of lean methanol are subjected to the second purification to obtain the purified non-shift gas and the non-shift H2S-rich methanol.

[0045] In some embodiments of the present application, preferably, the non-shift gas has a molar content of H2S of 0.9-1.2% and a molar content of CO2 of 5-10%, a temperature of -35 to -25℃ and a pressure of 5.5-6 MPa (G). In the present application, the source of the non-shift gas has a wide selection range as long as the non-shift gas meets the above-mentioned limitations. Preferably, the non-shift gas is selected from an upstream non-shift gas cooling process.

[0046] In the present application, the first purification aims to remove impurities such as HCN and NH3 and a small amount of H2S and CO2 in the non-shift gas. Preferably, the molar flow ratio of the non-shift gas to the first stream of non-shift H2S-rich methanol is 50-60:1.

[0047] In some embodiments of the present application, preferably, the mole content of H2S in the pre-purified non-reforming H2S-rich methanol is 2.1-2.6%, and the mole content of CO2 is 3-7%. In the present application, unless otherwise specified, the pre-purified non-reforming H2S-rich methanol is sent to the subsequent process.

[0048] In the present application, the second purification is intended to further remove H2S and CO2 from the non-reforming gas. Preferably, the mole flow ratio of the non-reforming gas to the first lean methanol is 1:1-1.1.

[0049] In some embodiments of the present application, preferably, the mole content of H2S in the lean methanol is 0%, and the mole content of CO2 is 0%. In the present application, the lean methanol is from the subsequent process.

[0050] In the present application, unless otherwise specified, the lean methanol is divided into the first lean methanol and the second lean methanol. In the present application, the mole flow ratio of the first lean methanol to the second lean methanol is not limited.

[0051] In some embodiments of the present application, preferably, the mole content of H2S in the purified non-reforming gas is ≤0.1 ppm, and the mole content of CO2 is ≤20 ppm; the temperature is -55 to -50°C, and the pressure is 5.4-6 MPa(G).

[0052] In some embodiments of the present application, preferably, the mole content of H2S in the non-reforming H2S-rich methanol is 0.6-1.1%, and the mole content of CO2 is 4-9%; the temperature is -32 to -27°C; and the pressure is 5.5-6 MPa(G).

[0053] In the present application, the non-reforming H2S-rich methanol is divided into three streams. Preferably, the mole flow ratio of the first non-reforming H2S-rich methanol, the second non-reforming H2S-rich methanol, and the third non-reforming H2S-rich methanol is 1:5-7:58-62.

[0054] In some embodiments of the present application, preferably, the two-stage H2S absorption comprises a first H2S absorption and a second H2S absorption; further preferably, the second non-reforming H2S-rich methanol is returned to the first H2S absorption; and the primary CO2-rich methanol and the low-sulfur carbon-rich methanol are each independently returned to the second H2S absorption.

[0055] In some embodiments of the present application, further preferably, the synthesis gas and the second non-reforming H2S-rich methanol are subjected to the first H2S absorption to obtain the primary H2S-rich methanol and pre-desulfurization gas; and the pre-desulfurization gas, the low-sulfur carbon-rich methanol, and the primary CO2-rich methanol are subjected to the second H2S absorption to obtain the secondary H2S-rich methanol and desulfurization gas.

[0056] In some embodiments of the present application, preferably, 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 5.3-5.7 MPa (G). In the present application, the source of the synthesis gas has a wide selection range as long as the synthesis gas meets the above-mentioned limitations. Preferably, the synthesis gas is selected from the upstream synthesis gas cooling process.

[0057] In the present application, the first H2S absorption aims to remove HCN, NH3 and other impurities in the synthesis gas, as well as a small amount of H2S and CO2; the second H2S absorption aims to further remove H2S and CO2 in the synthesis gas. Preferably, the molar flow ratio of the synthesis gas to the second non-shift H2S-rich methanol is 60-70:1; the molar flow ratio of the synthesis gas to the low-sulfur carbon-rich methanol is 17-22:1; and the molar flow ratio of the synthesis gas to the primary CO2-rich methanol is 2-3:1.

[0058] In some embodiments of the present application, preferably, the molar content of H2S in the primary H2S-rich methanol is 2.4-2.9%, and the molar content of CO2 is 66-71%. In the present application, the primary H2S-rich methanol is sent to the subsequent process for treatment.

[0059] In some embodiments of the present application, preferably, the molar content of H2S in the desulfurized gas is 0.5-1 ppm, and the molar content of CO2 is 38-44%; the temperature is -20 to -13°C; and the pressure is 5.3-5.4 MPa (G).

[0060] In some embodiments of the present application, preferably, the molar content of H2S in the secondary H2S-rich methanol is 1.5-2%, and the molar content of CO2 is 40-45%; the temperature is -12 to -7°C.

[0061] In some embodiments of the present application, preferably, the primary CO2-rich methanol is sequentially subjected to first pressurization to 5.6-6 MPa (G), first cooling to -36 to -33°C in the direction of material flow, and then returned to the second H2S absorption.

[0062] In some embodiments of the present application, preferably, the low-sulfur carbon-rich methanol is subjected to second pressurization to 5.6-6 MPa (G) and then returned to the second H2S absorption.

[0063] In some embodiments of the present application, preferably, the tertiary CO2 absorption comprises: a first CO2 absorption, a second CO2 absorption and a third CO2 absorption; further preferably, the first stream of the secondary CO2-rich methanol is returned to the first CO2 absorption; the tertiary CO2-rich methanol is returned to the second CO2 absorption; the second stream of the semi-lean liquid methanol is returned to the third CO2 absorption.

[0064] In some embodiments of the present application, further preferably, the desulfurized gas and the first stream of the secondary CO2-rich methanol are subjected to the first CO2 absorption to obtain the primary CO2-rich methanol and a primary pre-purified gas; the primary pre-purified gas and the tertiary CO2-rich methanol are subjected to the second CO2 absorption to obtain the secondary CO2-rich methanol and a secondary pre-purified gas; the secondary pre-purified gas, the second stream of the semi-lean liquid methanol and the second stream of the lean methanol are subjected to the third CO2 absorption to obtain the purified gas and the tertiary CO2-rich methanol.

[0065] In the present application, the first CO2 absorption aims to remove CO2 in the desulfurized gas. Preferably, the molar flow ratio of the desulfurized gas and the first stream of the secondary CO2-rich methanol is 2-3:1, for example, 2:1, 2.5:1, 3:1, and any value in the range consisting of any two of the numerical values.

[0066] In some embodiments of the present application, preferably, the molar content of CO2 in the primary CO2-rich methanol is 38-42%, and the molar content of H2S is 0.1-0.5 ppm; the temperature is -10 to -6℃, and the pressure is 5.3-5.4 MPa(G).

[0067] In some embodiments of the present application, preferably, the molar content of CO2 in the secondary CO2-rich methanol is 29-34%, and the molar content of H2S is 0.1-0.5 ppm; the temperature is -10 to -5℃.

[0068] In the present application, the secondary CO2-rich methanol is divided into two streams, the first stream is returned to the first CO2 absorption, and the second stream is subjected to the CO2 flashing. Preferably, the molar flow ratio of the first stream of the secondary CO2-rich methanol and the second stream of the secondary CO2-rich methanol is 1:2.3-2.7, for example, 1:2.3, 1:2.5, 1:2.7, and any value in the range consisting of any two of the numerical values.

[0069] In some embodiments of the present application, preferably, the first stream of the secondary CO2-rich methanol is subjected to the first CO2 absorption after being cooled to -22 to -18℃ by a second cooling.

[0070] In some embodiments of the present application, preferably, the second stream of the secondary CO2-rich methanol is subjected to the CO2 flashing after being cooled to -36 to -33℃ by a third cooling.

[0071] In this invention, the second CO2 absorption is intended to further remove CO2 from the desulfurized gas. Preferably, the molar flow ratio of the primary pre-purified gas and the tertiary CO2-rich methanol is 1:1.1-1.2.

[0072] In some embodiments of the present invention, preferably, the third-stage CO2-rich methanol is cooled to -36 to -33°C in a fourth stage before the second CO2 absorption is performed.

[0073] In some embodiments of the present invention, preferably, the molar flow ratio of the purified gas and the second semi-lean methanol is 1.6-1.9:1; the molar flow ratio of the purified gas and the second lean methanol is 1:1-1.2.

[0074] In some embodiments of the present invention, preferably, 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 5.2-5.3MPa(G).

[0075] In this invention, the second stream of secondary CO2-rich methanol is cooled to -36 to -33°C before CO2 flash evaporation. This configuration allows for the full recovery of effective gases from the second stream of secondary CO2-rich methanol, thereby effectively reducing the energy consumption for CO2 flash liquid reabsorption.

[0076] In this invention, the second stream of CO2-rich methanol is subjected to a third cooling process followed by CO2 flash evaporation to obtain CO2 flash vapor and CO2 flash liquid. Preferably, the pressure of the CO2 flash evaporation is 1.6-2 MPa(G).

[0077] In some embodiments of the present invention, more preferably, the molar content of H2S in the CO2 flash liquid is 0.1-0.5 ppm, the molar content of CO2 is 28.5-33.5%, and the temperature is -36.5 to -33.5°C.

[0078] In this invention, the CO2 flash liquid is divided into a first CO2 flash liquid and a second CO2 flash liquid, which are then subjected to first flash evaporation and second flash evaporation, respectively. Preferably, the molar flow ratio of the first CO2 flash liquid and the second CO2 flash liquid is 3-4:1, for example, 3:1, 3.5:1, 4:1, or any value within any range of two such values.

[0079] In this invention, preferably, the secondary H2S-rich methanol is cooled to -36 to -33°C in a fifth cooling process before H2S flash evaporation. This configuration allows for the full recovery of effective gases from the secondary H2S-rich methanol, thereby effectively reducing the energy consumption for H2S flash liquid reabsorption.

[0080] In some embodiments of the present application, after the fifth cooling of the secondary H2S-rich methanol, the H2S flashing is performed to obtain the H2S flashing gas and H2S flashing liquid. Preferably, the H2S flashing is performed at a pressure of 1.6-2 MPa (G).

[0081] In some embodiments of the present application, further preferably, the H2S flashing liquid has a molar content of H2S of 1.45-1.95% and a molar content of CO2 of 39.5-44.5%, and a temperature of -36.5 to -33.5℃.

[0082] In some embodiments of the present application, preferably, the first washing process comprises: performing a primary washing on the third semi-lean liquid methanol and CO2 flashing gas to obtain carbon-rich methanol and washed CO2 flashing gas; and performing a secondary washing on the carbon-rich methanol and H2S flashing gas to obtain the low-sulfur carbon-rich methanol and washing gas.

[0083] In some embodiments of the present application, further preferably, the second semi-lean liquid methanol and the third semi-lean liquid methanol are each independently pressurized to 5.5-6 MPa (G) to perform the third CO2 absorption and the first washing, respectively.

[0084] In some embodiments of the present application, preferably, the carbon-rich methanol has a molar content of H2S of 0.1-0.5 ppm and a molar content of CO2 of 20-24%, and a temperature of -63 to -60℃; and the washed CO2 flashing gas has a temperature of -70 to -60℃ and a pressure of 1.6-2 MPa (G).

[0085] In some embodiments of the present application, preferably, the low-sulfur carbon-rich methanol has a molar content of H2S of ≤0.1% and a molar content of CO2 of 20-25%, and a temperature of -60 to -56℃.

[0086] In the present application, the third non-shift H2S-rich methanol is used as a washing solvent to perform a second washing on the washing gas obtained from the secondary washing, so as to further reduce the H2S concentration in the H2S flashing gas. Preferably, the second washing process comprises: performing the second washing on the third non-shift H2S-rich methanol and the washing gas to obtain the second H2S-rich methanol and washed H2S flashing gas.

[0087] In some embodiments of the present application, further preferably, the second H2S-rich methanol has a molar content of H2S of 0.7-1% and a molar content of CO2 of 4-8%, and a temperature of -33 to -28℃; and the washed H2S flashing gas has a temperature of -35 to -25℃ and a pressure of 1.6-2 MPa (G).

[0088] In the present application, the post-washing CO2 flash gas and the post-washing H2S flash gas are mixed, and the obtained flash gas is sent to a subsequent process for treatment.

[0089] In some embodiments of the present application, preferably, the pressure of the first flash is selected from 0.05-0.08 MPa (G); the pressure of the second flash is selected from 0.06-0.09 MPa (G); and the pressure of the third flash is selected from 0.09-0.12 MPa (G).

[0090] In the present application, the first heat exchange, on one hand, generates low temperature through pressure reduction flash, improves the absorption capacity of the second CO2 flash liquid to H2S gas, and is beneficial to the H2S gas in the post-washing flash CO2 product gas; on the other hand, recycles the cold energy of the reabsorption tower. Preferably, the second CO2 flash liquid and the first H2S-rich methanol are subjected to the first heat exchange, and the obtained heat-exchanged CO2 flash liquid and the first heat-exchanged H2S-rich methanol are subjected to the second flash and the gas stripping, respectively.

[0091] In some embodiments of the present application, further preferably, the temperature of the heat-exchanged CO2 flash liquid is -52 to -48℃; and the temperature of the first heat-exchanged H2S-rich methanol is -70 to -65℃.

[0092] In some embodiments of the present application, preferably, the first CO2 flash liquid is subjected to the first flash to obtain the semi-lean liquid methanol and the first CO2 product gas; the heat-exchanged CO2 flash liquid is subjected to the second flash to obtain a flash liquid and a second CO2 product gas; and the H2S flash liquid is subjected to the third flash to obtain the first H2S-rich methanol and a sulfur-containing gas phase; wherein the flash liquid and the sulfur-containing gas phase are contacted to obtain the low-H2S methanol and a third CO2 product gas; and the CO2 product gas comprises the first CO2 product gas, the second CO2 product gas and the third CO2 product gas.

[0093] In some embodiments of the present application, preferably, the molar content of CO2 in the semi-lean liquid methanol is 19.5-23.5%, and the molar content of H2S is ≤1 ppm; and the temperature is -66 to -61℃.

[0094] In some embodiments of the present application, preferably, the semi-lean liquid methanol is divided into a first semi-lean liquid methanol, a second semi-lean liquid methanol and a third semi-lean liquid methanol with a molar flow ratio of 7-8:5-7:1. In the present application, the semi-lean liquid methanol is divided into three streams, the first stream is subjected to the third washing, the second stream is returned and subjected to the three-stage CO2 absorption (especially the third CO2 absorption), and the third stream is returned and subjected to the first washing.

[0095] In some embodiments of the present application, preferably, the H2S molar content in the CO2 product gas is ≤1 ppm, the CO2 molar content is 99.4-99.7%, the temperature is -66 to -62℃, and the pressure is 0.05-0.08 MPa (G).

[0096] In some embodiments of the present application, preferably, the H2S molar content in the low-H2S methanol is 0.4-0.6%, the CO2 molar content is 25-29%, the temperature is -65 to -60℃, and the pressure is 0.12-0.16 MPa (G).

[0097] In some embodiments of the present application, preferably, the H2S molar content in the first H2S-rich methanol is 1.4-1.9%, the CO2 molar content is 29-34%, the temperature is -70 to -66℃, and the pressure is 0.13-0.17 MPa (G).

[0098] In the present application, the second heat exchange aims to further increase the temperature of the first H2S-rich methanol, which is conducive to reducing the solubility of CO2. Preferably, the first heat-exchanged H2S-rich methanol is subjected to a second heat exchange to obtain a second heat-exchanged H2S-rich methanol with a temperature of -30 to -37℃, which is subjected to the gas stripping.

[0099] In the present application, the third heat exchange aims to reduce the solubility of CO2. Preferably, the third H2S-rich methanol is subjected to a third heat exchange to obtain a third heat-exchanged H2S-rich methanol with a temperature of -20 to -18℃, which is subjected to the gas stripping.

[0100] In the present application, the gas stripping aims to contact the first H2S-rich methanol, the second H2S-rich methanol, the third H2S-rich methanol, and the low-H2S methanol with nitrogen and perform the gas stripping. Preferably, the second heat-exchanged H2S-rich methanol, the second H2S-rich methanol, the third heat-exchanged H2S-rich methanol, the low-H2S methanol, and nitrogen are contacted and subjected to the gas stripping to obtain the gas-stripped H2S-rich methanol and the gas stripping gas.

[0101] In some embodiments of the present application, further preferably, the H2S molar content in the gas-stripped H2S-rich methanol is 1-2%, the CO2 molar content is 2-5%, and the temperature is -48 to -40℃.

[0102] In the present application, the process of the third washing includes: subjecting the first stream of semi-lean liquid methanol and the gas stripping gas to the third washing to obtain a third H2S-rich methanol and a tail gas. Preferably, the H2S molar content in the third H2S-rich methanol is 1-4%, the CO2 molar content is 17-22%, and the temperature is -62 to -58℃. In the present application, the third H2S-rich methanol is sent back and subjected to the gas stripping.

[0103] In some embodiments of the present invention, preferably, the molar content of H2S in the tail gas obtained from the third washing is ≤1 ppm, and the molar content of CO2 is 84-89%; the temperature is -67 to -63°C. In the present invention, the tail gas is sent to the subsequent process.

[0104] The second aspect of the present invention provides a structural schematic diagram of a polygeneration acid gas removal device for a coal water slurry gasification device as Figure 1 shown, from Figure 1 it can be seen that the device includes: a connected non-shifted gas scrubbing tower T-1, H2S absorption tower T-2, CO2 absorption tower T-3, CO2 medium-pressure flash tower T-4, H2S medium-pressure flash tower T-5 and reabsorption tower T-6; the CO2 medium-pressure flash tower T-4 is divided from top to bottom into a CO2 scrubbing section and a CO2 flash section connected by lifting holes; the H2S medium-pressure flash tower T-5 is divided from top to bottom into a second H2S scrubbing section, a first H2S scrubbing section and an H2S flash section connected by lifting holes;

[0105] The non-shifted gas scrubbing tower T-1 is used to purify the non-shifted gas 1 in two stages. The obtained non-shifted H2S-rich methanol 3 is divided into three streams. The first stream of non-shifted H2S-rich methanol 3-i is recycled and used in the non-shifted gas scrubbing tower T-1. The second stream of non-shifted H2S-rich methanol 3-ii is sent to the H2S absorption tower T-2. The third stream of non-shifted H2S-rich methanol 3-iii is sent to the second H2S scrubbing section;

[0106] The H2S absorption tower T-2 is used to absorb H2S in the syngas 6 in two stages, obtaining first-stage H2S-rich methanol 7, second-stage H2S-rich methanol 10 and desulfurized gas 11;

[0107] The CO2 absorption tower T-3 is used to absorb CO2 in the desulfurized gas 11 in three stages, obtaining first-stage CO2-rich methanol 9, second-stage CO2-rich methanol 21, third-stage CO2-rich methanol 13 and purified gas 14; among them, the first-stage CO2-rich methanol 9 is recycled and used in the H2S absorption tower T-2. The second-stage CO2-rich methanol 21 is divided into two streams. The first stream of second-stage CO2-rich methanol 21-i and the third-stage CO2-rich methanol 13 are independently recycled and used in the CO2 absorption tower T-3;

[0108] Among them, the CO2 flash section is used to flash the second stream of second-stage CO2-rich methanol 21-ii to obtain CO2 flash gas, which enters the CO2 scrubbing section, and the obtained CO2 flash liquid 23 is divided into two streams; the H2S flash section is used to flash the second-stage H2S-rich methanol 10 to obtain H2S flash gas, which enters the first H2S scrubbing section, and obtain H2S flash liquid 12;

[0109] The reabsorption tower T-6 is divided into an upper tower and a lower tower, the upper tower is divided into a first flash evaporation section, a second flash evaporation section and a third flash evaporation section from top to bottom and communicated through a riser, and is used for performing first flash evaporation, second flash evaporation and third flash evaporation on the first CO2 flash liquid 23-i, the second CO2 flash liquid 23-ii and the H2S flash liquid 12 respectively to obtain the semi-lean liquid methanol 27, the low-H2S methanol 28, the first H2S-rich methanol 22 and the CO2 product gas 26.

[0110] The semi-lean liquid methanol 27 is divided into three streams, the second semi-lean liquid methanol 27-ii is used for the CO2 absorption tower T-3, the third semi-lean liquid methanol 27-iii sequentially passes through a CO2 washing section and a first H2S washing section, sequentially performs first washing with the CO2 flash gas and the H2S flash gas to obtain the low-sulfur carbon-rich methanol 25 used for the H2S absorption tower T-2, and the washing gas obtained is introduced into a second H2S washing section to perform second washing with the third non-shift H2S-rich methanol 3-iii to obtain the second H2S-rich methanol 15.

[0111] The lower tower of the reabsorption tower T-6 is divided into a washing section and a gas stripping section from top to bottom and communicated through a riser, the gas stripping section is connected with the bottom of the washing section, the second H2S washing section, the second flash evaporation section and the third flash evaporation section, and is used for independently performing gas stripping on the third H2S-rich methanol 19, the second H2S-rich methanol 15, the low-H2S methanol 28 and the first H2S-rich methanol 22 to obtain the gas-stripped H2S-rich methanol 17, and the gas stripping gas obtained is introduced into the washing section to perform third washing with the first semi-lean liquid methanol 27-i to obtain the third H2S-rich methanol 19 used for the gas stripping section.

[0112] According to the present application, as shown in Figure 1 Preferably, the non-shift gas washing tower T-1 is divided into a first purification section and a second purification section from bottom to top and communicated through a riser; the first purification section is used for performing first purification on the non-shift gas 1 and the first non-shift H2S-rich methanol 3-i to obtain the pre-purified non-shift H2S-rich methanol 4, and the pre-purified non-shift gas obtained is introduced into the second purification section to perform second purification with the first lean methanol 2-i from a subsequent process to obtain the purified non-shift gas 5 and the non-shift H2S-rich methanol 3.

[0113] In the present application, the first purification section and the second purification section are connected through a riser without special circumstances, so that the pre-purified non-shift gas from the first purification section enters the second purification section to perform second purification.

[0114] According to the present application, as shown in Figure 1As shown, preferably, the H2S absorption tower T-2 is divided into a first H2S absorption section and a second H2S absorption section from bottom to top, which are communicated by a riser; wherein the first H2S absorption section is used for carrying out first H2S absorption on the synthesis gas 6 and the second non-shift H2S-rich methanol 3-ii to obtain the first H2S-rich methanol 7, and the obtained pre-desulfurization gas enters the second H2S absorption section, sequentially carries out second H2S absorption with the low-sulfur carbon-rich methanol 25 and the first CO2-rich methanol 9 to obtain the desulfurization gas 11 and the second H2S-rich methanol 10.

[0115] In the present application, without special circumstances, the first H2S absorption section and the second H2S absorption section are connected by a riser, so that the pre-desulfurization gas from the first H2S absorption section enters the second H2S absorption section, first contacts the low-sulfur carbon-rich methanol 25 from the middle of the second H2S absorption section and carries out second H2S absorption, and then contacts the first CO2-rich methanol 9 from the upper part of the second H2S absorption section and carries out second H2S absorption.

[0116] According to the present application, as shown in Figure 1 As shown, preferably, a first pump P-1 and a first cooler E-1 are sequentially arranged on the pipeline connecting the CO2 absorption tower T-3 and the second H2S absorption section in the direction of material flow, which are used for sequentially carrying out first pressurization and first cooling on the first CO2-rich methanol 9, and then carrying out the second H2S absorption.

[0117] According to the present application, as shown in Figure 1 As shown, preferably, a second pump P-2 is arranged on the pipeline connecting the first H2S washing section and the second H2S absorption section, which is used for carrying out second pressurization on the low-sulfur carbon-rich methanol 25, and then carrying out the second H2S absorption.

[0118] According to the present application, as shown in Figure 1 As shown, preferably, the CO2 absorption tower T-3 is divided into a first CO2 absorption section, a second CO2 absorption section and a third CO2 absorption section from bottom to top, which are communicated by risers; wherein the first CO2 absorption section is connected with the second CO2 absorption section, which is used for carrying out first CO2 absorption on the desulfurization gas 11 and the first second CO2-rich methanol 21-i to obtain the first CO2-rich methanol 9 and first pre-purification gas; the second CO2 absorption section is connected with the third CO2 absorption section, which is used for carrying out second CO2 absorption on the first pre-purification gas and the third CO2-rich methanol 13 to obtain the second CO2-rich methanol 21 in two streams and second pre-purification gas; the third CO2 absorption section is connected with the first flash evaporation part of the reabsorption tower T-6 and the lean methanol from the subsequent process, which is used for carrying out third CO2 absorption on the second pre-purification gas, the second half-lean liquid methanol 27-ii and the second lean methanol 2-ii to obtain the third CO2-rich methanol 13 and the purified gas 14.

[0119] In the present application, without special circumstances, the first CO2 absorption section and the second CO2 absorption section are connected by a riser, so that the first-stage pre-purified gas from the first CO2 absorption section enters the second CO2 absorption section, and is contacted with the third-stage CO2-rich methanol from the middle of the second CO2 absorption section and performs the second CO2 absorption; the second CO2 absorption section and the third CO2 absorption section are connected by a riser, so that the second-stage pre-purified gas from the second CO2 absorption section enters the third CO2 absorption section, and is first contacted with the second semi-lean liquid methanol 27-ii from the middle of the third CO2 absorption section and performs the third CO2 absorption, and then is contacted with the second lean methanol 2-ii from the upper part of the third CO2 absorption section and performs the third CO2 absorption.

[0120] According to the present application, as shown in Figure 1 Further preferably, a second cooler E-2 is arranged on the pipeline connecting the second CO2 absorption section and the first CO2 absorption section, for performing the first CO2 absorption after the first stock of second-stage CO2-rich methanol 21-i is secondarily cooled.

[0121] According to the present application, as shown in Figure 1 Further preferably, a third cooler E-3 is arranged on the pipeline connecting the second CO2 absorption section and the CO2 flashing section, for performing the CO2 flashing after the second stock of second-stage CO2-rich methanol 21-ii is thirdly cooled.

[0122] According to the present application, as shown in Figure 1 Further preferably, a fourth cooler E-4 is arranged on the pipeline connecting the third CO2 absorption section and the second CO2 absorption section, for performing the second CO2 absorption after the third-stage CO2-rich methanol 13 is fourthly cooled.

[0123] According to the present application, as shown in Figure 1 The CO2 medium-pressure flashing tower T-4 is divided into a CO2 washing section and a CO2 flashing section from top to bottom by a riser, wherein the CO2 flashing section is used for performing the CO2 flashing after the second stock of second-stage CO2-rich methanol 21-ii is thirdly cooled, to obtain CO2 flashing gas entering the CO2 washing section, and to obtain CO2 flashing liquid 23 divided into a first stock of CO2 flashing liquid 23-i and a second stock of CO2 flashing liquid 23-ii; the CO2 washing section is used for performing the first-stage washing of the third stock of semi-lean liquid methanol 27-iii and the CO2 flashing gas, to obtain carbon-rich methanol 24 and washed CO2 flashing gas 16-ii.

[0124] According to the present application, as shown in Figure 1As shown, the H2S medium-pressure flash tower T-5 is divided into a second H2S washing section, a first H2S washing section and an H2S flash section from top to bottom and communicated through a riser; wherein the H2S flash section is used for carrying out the H2S flashing of the secondary H2S-rich methanol 10 after the fifth cooling, and the obtained H2S flash gas enters the first H2S washing section, and the obtained H2S flash liquid 12; the first H2S washing section is used for carrying out the secondary washing of the carbon-rich methanol 24 and the H2S flash gas, and the obtained washing gas enters the second H2S washing section, and the obtained low-sulfur carbon-rich methanol 25; the second H2S washing section is used for carrying out the second washing of the third non-shift H2S-rich methanol 3-iii and the washing gas, and the obtained washing H2S-rich flash gas 16-i and the secondary H2S-rich methanol 15.

[0125] According to the present application, as shown in Figure 1 Preferably, a first heat exchanger Q-1 is arranged on the pipeline connecting the CO2 flash section, the third flash part, the second flash part and the stripping part, and is used for carrying out the first heat exchange of the second CO2 flash liquid 23-ii and the first H2S-rich methanol 22, and the obtained heat-exchanged CO2 flash liquid 29 and the first heat-exchanged H2S-rich methanol 30 are subjected to the second flash and the stripping, respectively.

[0126] In the present application, as shown in Figure 1 The reabsorption tower T-6 is divided into an upper tower and a lower tower, and the upper tower is divided into a first flash part, a second flash part and a third flash part from top to bottom and communicated through a riser; wherein the first flash part is used for carrying out the first flash of the first CO2 flash liquid 23-i, and the obtained first CO2 product gas and the obtained semi-lean liquid methanol 27 are divided into three streams; the second flash part is used for carrying out the second flash of the heat-exchanged CO2 flash liquid 29 obtained by the first heat exchange of the second CO2 flash liquid 23-ii, and the obtained flash liquid and the second CO2 product gas; the third flash part is used for carrying out the third flash of the H2S flash liquid 12, and the obtained first H2S-rich methanol 22 and the sulfur-containing gas phase; wherein the sulfur-containing gas phase and the flash liquid are contacted to obtain the third CO2 product gas and the low-H2S methanol 28, and the first CO2 product gas, the second CO2 product gas and the third CO2 product gas are mixed to obtain the CO2 product gas 26.

[0127] According to the present application, as shown in Figure 1 Preferably, a second heat exchanger Q-2 is further arranged on the pipeline connecting the first heat exchanger Q-1 and the stripping part, and is used for carrying out the second heat exchange of the first heat-exchanged H2S-rich methanol 30, and the obtained second heat-exchanged H2S-rich methanol 31 is subjected to the stripping.

[0128] According to the present application, as shown in Figure 1As shown, preferably, a third heat exchanger Q-3 is arranged on the pipeline connecting the washing section and the stripping section, for performing third heat exchange on the third H2S-rich methanol 19 to obtain third heat-exchanged H2S-rich methanol 32 for the stripping.

[0129] In the present application, as shown, Figure 1 As shown, the lower tower of the reabsorption tower T-6 is divided into a washing section and a stripping section in communication through a riser, wherein the stripping section is connected with the bottom of the washing section, the second H2S washing section, the second flash section and the third flash section, for contacting and stripping the third heat-exchanged H2S-rich methanol 32 obtained by performing third heat exchange on the third H2S-rich methanol 19, the second heat-exchanged H2S-rich methanol 31 obtained by performing second heat exchange on the second H2S-rich methanol 15, the low H2S methanol 28, and the first heat-exchanged H2S-rich methanol 22 obtained by performing first heat exchange on the first H2S-rich methanol 22, respectively, with nitrogen 18 to obtain stripped H2S-rich methanol 17, and the stripping gas obtained is introduced into the washing section to perform third washing with the first stream of semi-lean liquid methanol 27-i to obtain the third H2S-rich methanol 19 for the stripping section, and tail gas 20.

[0130] The present application will be described in detail below through examples.

[0131] Example 1

[0132] The non-shift gas washing tower T-1 is divided into a first purification section and a second purification section in communication through a riser from bottom to top; the non-shift gas 1 (the molar content of H2S is 0.9-1.2%, the molar content of CO2 is 5-10%; the temperature is -35 to -25°C, and the pressure is 5.5-6 MPa(G)) sent from the upstream non-shift gas cooling process enters the first purification section, contacts with the first stream of non-shift H2S-rich methanol 3-i at a molar flow ratio of 50-60:1, and performs first purification to obtain pre-purified non-shift H2S-rich methanol 4 (the molar content of H2S is 2.1-2.6%, the molar content of CO2 is 3-7%), which is sent to the subsequent process for treatment, and the pre-purified non-shift gas enters the second purification section, contacts with the first stream of lean methanol 2-i, and performs second purification to obtain purified non-shift gas 5 (the molar content of H2S is ≤0.1 ppm, the molar content of CO2 is ≤20 ppm; the temperature is -55 to -45°C, and the pressure is 5.4-6 MPa(G)) and non-shift H2S-rich methanol 3 (the molar content of H2S is 0.6-1.1%, the molar content of CO2 is 4-9%; the temperature is -32 to -27°C; the pressure is 5.5-6 MPa(G));

[0133] The first stream of lean methanol 2-i and the non-shifted gas 1 have a molar flow ratio of 1-1.1:1; the non-shifted H2S-rich methanol 3 is divided into the first stream of non-shifted H2S-rich methanol 3-i, the second stream of non-shifted H2S-rich methanol 3-ii and the third stream of non-shifted H2S-rich methanol 3-iii with a molar flow ratio of 1:5-7:58-62;

[0134] The H2S absorption tower T-2 is divided into a first H2S absorption section and a second H2S absorption section in communication through a riser; the synthesis gas 6 (H2S molar content of 0.9-1.2%, CO2 molar content of 40-50%; temperature of -15 to -5°C, pressure of 5.3-5.7 MPa(G)) from the upstream synthesis gas cooling process enters the first H2S absorption section, contacts the second stream of non-shifted H2S-rich methanol 3-ii from the non-shifted gas washing tower T-1 with a molar flow ratio of 60-70:1 and performs first H2S absorption to obtain the first H2S-rich methanol 7 (H2S molar content of 2.4-2.9%, CO2 molar content of 66-71%) sent to the subsequent process for treatment, and the obtained pre-desulfurization gas enters the second H2S absorption section, sequentially contacts the low-sulfur carbon-rich methanol 25 (second pressurized to 5.8-6 MPa(G)) and the first CO2-rich methanol 9 (first pressurized to 5.8-6 MPa(G) in the order of material flow direction, first cooled to -36 to -33°C) and performs second H2S absorption to obtain the desulfurized gas 11 (H2S molar content of 0.5-1 ppm, CO2 molar content of 38-44%; temperature of -20 to -13°C; pressure of 5.3-5.4 MPa(G)) and the second H2S-rich methanol 10 (H2S molar content of 1.5-2%, CO2 molar content of 40-45%; temperature of -12 to -7°C);

[0135] The molar flow ratio of the low-sulfur carbon-rich methanol 25 and the synthesis gas 6 is 1:17-22; the molar flow ratio of the first CO2-rich methanol 9 and the synthesis gas 6 is 1:2-3.

[0136] The CO2 absorption tower T-3 is divided into a first CO2 absorption section, a second CO2 absorption section and a third CO2 absorption section from bottom to top, which are communicated by the riser holes; the desulfurized gas 11 from the H2S absorption tower T-2 enters the first CO2 absorption section, and is countercurrently contacted with the first secondary CO2-rich methanol 21-i (which is cooled to -22 to -18℃) from the second CO2 absorption section at a molar flow ratio of 2-3:1 to carry out the first CO2 absorption, to obtain the primary CO2-rich methanol 9 (the molar content of CO2 is 38-42%, the molar content of H2S is 0.1-0.5ppm; the temperature is -10 to -6℃, and the pressure is 5.3-5.4MPa(G)), and the primary pre-purified gas enters the second CO2 absorption section, and is contacted with the third CO2-rich methanol 13 (which is cooled to -36 to -33℃) from the third CO2 absorption section at a molar flow ratio of 1:1.1-1.2 to carry out the second CO2 absorption, to obtain the secondary CO2-rich methanol 21 (the molar content of CO2 is 29-34%, the molar content of H2S is 0.1-0.5ppm; the temperature is -10 to -5℃), and the secondary pre-purified gas enters the third CO2 absorption section, and is sequentially contacted with the second half-lean liquid methanol 27-ii and the second lean methanol 2-ii to carry out the third CO2 absorption, to obtain the purified gas 14 (the molar content of H2S is ≤0.1ppm, the molar content of CO2 is ≤20ppm; the temperature is -55 to -50℃, and the pressure is 5.2-5.3MPa(G)) and the third CO2-rich methanol 13;

[0137] wherein the molar flow ratio of the above-mentioned purified gas 14 and the second half-lean liquid methanol 27-ii is 1.6-1.9:1; and the molar flow ratio of the above-mentioned purified gas 14 and the second lean methanol 2-ii is 1:1-1.2;

[0138] The above-mentioned secondary CO2-rich methanol 21 is divided into the first secondary CO2-rich methanol 21-i and the second secondary CO2-rich methanol 21-ii at a molar flow ratio of 1:2.3-2.7;

[0139] The CO2 medium-pressure flash tower T-4 is divided into a CO2 washing section and a CO2 flash section from top to bottom, and the H2S medium-pressure flash tower T-5 is divided into a second H2S washing section, a first H2S washing section and a H2S flash section from bottom to top, which are communicated by the riser holes;

[0140] The second CO2-rich methanol 21-ii was sent to the CO2 flash section after being cooled to -36 to -33°C by the third cooling, and CO2 flash was carried out (the pressure was 1.6-2 MPa (G)), to obtain CO2 flash gas and CO2 flash liquid 23 (the molar content of H2S was 0.1-0.5 ppm, the molar content of CO2 was 28.5-33.5%, and the temperature was -36.5 to -33.5°C); and the CO2 flash liquid 23 was divided into a first CO2 flash liquid 23-i and a second CO2 flash liquid 23-ii with a molar flow ratio of 3-4:1;

[0141] The second H2S-rich methanol 10 was sent to the H2S flash section after being cooled to -36 to -33°C by the fifth cooling, and H2S flash was carried out (the pressure was 1.6-2 MPa (G)), to obtain H2S flash gas and H2S flash liquid 12 (the molar content of H2S was 1.45-1.95%, the molar content of CO2 was 39.5-44.5%, and the temperature was -36.5 to -33.5°C);

[0142] The absorption tower T-6 was divided into an upper tower and a lower tower, the upper tower was divided into a first flash section, a second flash section and a third flash section which were sequentially connected by a rising hole from top to bottom, and the lower tower was divided into a washing part and a gas stripping part which were connected by a rising hole from top to bottom;

[0143] The first flash section was used for first flash of the first CO2 flash liquid 23-i (the pressure was 0.05-0.08 MPa (G)), to obtain a first CO2 product gas and a semi-lean liquid methanol 27 (the molar content of CO2 was 19.5-23.5%, the molar content of H2S was ≤1 ppm, and the temperature was -66 to -61°C), which was divided into three parts; the second flash section was used for second flash of the second CO2 flash liquid 23-ii after first heat exchange (the pressure was 0.06-0.09 MPa (G)), to obtain a heat-exchanged CO2 flash liquid 29 with a temperature of -52 to -48°C and a second CO2 product gas; and the third flash section was used for third flash of the H2S flash liquid 12 (the pressure was 0.12-0.16 MPa (G)), to obtain a first H2S-rich methanol 22 (the molar content of H2S was 1.4-1.9%, the molar content of CO2 was 29-34%, the temperature was -70 to -66°C, and the pressure was 0.13-0.17 MPa (G)) and a sulfur-containing gas phase;

[0144] The semi-lean liquid methanol 27 was divided into a first semi-lean liquid methanol 27-i, a second semi-lean liquid methanol 27-ii and a third semi-lean liquid methanol 27-iii with a molar flow ratio of 7-8:5-7:1;

[0145] wherein the above H2S-containing gas phase and flash liquid are contacted to obtain low H2S methanol 28 (H2S molar content of 0.4-0.6%, CO2 molar content of 25-29%; temperature of -65 to -60°C, pressure of 0.12-0.16 MPa (G)), and third CO2 product gas, which is mixed with the first and second CO2 product gases to obtain CO2 product gas 26 (H2S molar content of <1 ppm, CO2 molar content of 99.4-99.7%; temperature of -66 to -62°C, pressure of 0.05-0.08 MPa (G));

[0146] wherein the above first H2S-rich methanol 22 and second H2S-rich flash liquid 23-ii are subjected to first heat exchange to obtain heat-exchanged CO2-rich flash liquid 29 and first heat-exchanged H2S-rich methanol 30 at a temperature of -70 to -65°C; and the above first heat-exchanged H2S-rich methanol 30 is subjected to second heat exchange to obtain second heat-exchanged H2S-rich methanol 31 at a temperature of -30 to -37°C;

[0147] wherein the CO2 scrubbing section is used to perform primary scrubbing of the above third semi-lean liquid methanol 27-iii (pressurized to 5.5-6 MPa (G)) and CO2 flash gas to obtain carbon-rich methanol 24 (H2S molar content of 0.1-0.5 ppm, CO2 molar content of 20-24%; temperature of -63 to -60°C) and scrubbed CO2 flash gas 16-ii (-70 to -60°C, pressure of 1.6-2 MPa (G)); the first H2S scrubbing section is used to perform secondary scrubbing of the above carbon-rich methanol 24 and H2S flash gas to obtain low-sulfur carbon-rich methanol 25 (H2S molar content of <0.1%, CO2 molar content of 20-25%; temperature of -60 to -56°C) and scrubbing gas; and the second H2S scrubbing section is used to perform second scrubbing of the above third non-shift H2S-rich methanol 3-iii and the above scrubbing gas to obtain second H2S-rich methanol 15 (H2S molar content of 0.7-1%, CO2 molar content of 4-8%; temperature of -33 to -28°C) and scrubbed H2S flash gas 16-i (temperature of -35 to -25°C, pressure of 1.6-2 MPa (G));

[0148] The gas stripping unit is used for contacting the second heat-exchanged H2S-rich methanol 31, the third heat-exchanged H2S-rich methanol 32, the second H2S-rich methanol 15, the low-H2S methanol 28 and the nitrogen 18 and performing gas stripping to obtain a gas-stripped H2S-rich methanol 17 (the molar content of H2S is 1-2%, the molar content of CO2 is 2-5%, and the temperature is -48 to -40°C) and a gas stripping gas; the washing unit is used for contacting the first semi-lean liquid methanol 27-i and the gas stripping gas and performing third washing to obtain a third H2S-rich methanol 19 (the molar content of H2S is 1-4%, the molar content of CO2 is 17-22%, and the temperature is -62 to -58°C) and a tail gas 20 (the molar content of H2S is ≤1 ppm, the molar content of CO2 is 84-89%, and the temperature is -67 to -63°C), and the third H2S-rich methanol 19 is subjected to third heat exchange to obtain the third heat-exchanged H2S-rich methanol 32 with a temperature of -20 to -18°C, which is subjected to the gas stripping.

[0149] Comparative Example 1

[0150] Taking a hydrogen production device using a coal water slurry gasification gasification device as an example, the effective gas (H2+CO) entering the low-temperature methanol washing device is 230000 Nm 3 / h, and based on this benchmark, the main technical parameters of the lean liquid-semi-lean liquid process (i.e., CN201110260570.0 discloses a low-temperature methanol washing process) are compared in Table 1.

[0151] Table 1

[0152]

[0153] As can be seen from the results in Table 1, taking a hydrogen production device based on a coal water slurry gasification gasification device as an example, the multi-production acid gas removal device of the coal water slurry gasification device provided in Example 1 has a lean methanol circulation amount of 88.9% of the lean methanol circulation amount in Comparative Example 1 (lean liquid-semi-lean liquid process), a semi-lean liquid methanol circulation amount of 80% of the semi-lean liquid methanol circulation amount in Comparative Example 1 (lean liquid-semi-lean liquid process), a CO2-rich methanol usage amount in the H2S absorption tower of 84.2% of the CO2-rich methanol usage amount in Comparative Example 1 (lean liquid-semi-lean liquid process), and a cumulative reduction of external cold consumption of 500 KW / h, and the overall energy-saving effect is remarkable.

[0154] The above describes the preferred embodiments of the present application in detail, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for removing acidic gases from a multi-generation coal-water slurry gasification unit, characterized in that, The method includes: Syngas (6) undergoes two-stage H2S absorption to obtain first-stage H2S-rich methanol (7), second-stage H2S-rich methanol (10), and desulfurized gas (11); the desulfurized gas (11) undergoes three-stage CO2 absorption to obtain first-stage CO2-rich methanol (9), which is returned to the two-stage H2S absorption, second-stage CO2-rich methanol (21) is split into two streams, third-stage CO2-rich methanol (13) is reused, and purified gas (14) is obtained; wherein, the first stream of second-stage CO2-rich methanol (21-i) is returned to the third-stage CO2 absorption, and the second stream of second-stage CO2-rich methanol (21-ii) undergoes CO2 flash evaporation to obtain CO2 flash vapor and two streams of CO2 flash liquid (23); the second-stage H2S-rich methanol (10) undergoes H2S flash evaporation to obtain H2S flash vapor and H2S flash liquid (12); Among them, the first CO2 flash liquid (23-i), the second CO2 flash liquid (23-ii) and the H2S flash liquid (12) are each subjected to the first flash, the second flash and the third flash independently to obtain semi-lean methanol (27), low H2S methanol (28), first H2S rich methanol (22) and CO2 product gas (26); The semi-lean methanol (27) is divided into three streams. The second semi-lean methanol (27-ii) is returned to the three-stage CO2 absorption process, and the third semi-lean methanol (27-iii) is subjected to a first wash with the CO2 flash vapor and H2S flash vapor in sequence to obtain low-sulfur, carbon-rich methanol (25), which is returned to the two-stage H2S absorption process. The non-shift H2S-rich methanol (3) from the non-shift gas purification process is divided into three streams. The first non-shift H2S-rich methanol (3-i) is reused, and the second non-shift H2S-rich methanol (3-ii) is used. Returning to the two-stage H2S absorption, the third non-conversion H2S-rich methanol (3-iii) undergoes a second wash with the washing gas obtained from the first wash, resulting in a second H2S-rich methanol (15). This second H2S-rich methanol (15) is then independently stripped from the first H2S-rich methanol (22), the third H2S-rich methanol (19), and the low H2S methanol (28), resulting in stripped H2S-rich methanol (17). The stripped gas and the first semi-lean methanol (27-i) are then subjected to a third wash to obtain the third H2S-rich methanol (19).

2. The method according to claim 1, wherein, The second CO2 flash liquid (23-ii) and the first H2S-rich methanol (22) are subjected to a first heat exchange to obtain a CO2 flash liquid (29) after heat exchange and a H2S-rich methanol (30) after the first heat exchange, which are then subjected to a second flash evaporation and gas stripping, respectively. Preferably, the temperature of the CO2 flash liquid (29) after heat exchange is -52 to -48°C; the temperature of the first H2S-rich methanol (30) after heat exchange is -70 to -65°C; Preferably, the H2S-rich methanol (30) after the first heat exchange is subjected to a second heat exchange to obtain the second heat-exchanged H2S-rich methanol (31) at a temperature of -30 to -37°C, which is then subjected to the gas stripping. Preferably, the third H2S-rich methanol (19) is subjected to a third heat exchange to obtain H2S-rich methanol (32) after the third heat exchange at a temperature of -20 to -18°C, which is then subjected to the gas stripping.

3. The method according to claim 1 or 2, wherein, The non-conversion gas purification process includes: contacting non-conversion gas (1), a first stream of non-conversion H2S-rich methanol (3-i) and a first stream of lean methanol (2-i) from a subsequent process and performing two-stage purification to obtain pre-purified non-conversion H2S-rich methanol (4), purified non-conversion gas (5) and the non-conversion H2S-rich methanol (3). Preferably, the two-stage purification includes a first purification and a second purification, and preferably the first non-conversion H2S-rich methanol (3-i) is returned to the first purification. More preferably, the non-conversion gas (1) and the first non-conversion H2S-rich methanol (3-i) are subjected to a first purification to obtain the pre-purified non-conversion H2S-rich methanol (4) and the pre-purified non-conversion gas; the pre-purified non-conversion gas and the first lean methanol (2-i) are subjected to a second purification to obtain the purified non-conversion gas (5) and the non-conversion H2S-rich methanol (3). Preferably, the non-shift gas (1) has a molar content of H2S of 0.9-1.2% and a molar content of CO2 of 5-10%; the temperature is -35 to -25°C and the pressure is 5.5-6 MPa(G); Preferably, the molar content of H2S in the purified non-conversion gas (5) is ≤0.1ppm, and the molar content of CO2 is ≤20ppm; the temperature is -55 to -50℃, and the pressure is 5.4-6MPa(G); Preferably, the non-conversion H2S-rich methanol (3) has a molar content of 0.6-1.1% for H2S and a molar content of 4-9% for CO2; a temperature of -32 to -27°C; and a pressure of 5.5-6 MPa(G). Preferably, the molar flow ratio of the first non-conversion H2S-rich methanol (3-i), the second non-conversion H2S-rich methanol (3-ii), and the third non-conversion H2S-rich methanol (3-iii) is 1:5-7:58-62.

4. The method according to any one of claims 1-3, wherein, The two-stage H2S absorption includes: a first H2S absorption and a second H2S absorption; Preferably, the second non-conversion H2S-rich methanol (3-ii) is returned to the first H2S absorber; the first-stage CO2-rich methanol (9) and the low-sulfur carbon-rich methanol (25) are each returned to the second H2S absorber independently. More preferably, the synthesis gas (6) and the second non-conversion H2S-rich methanol (3-ii) are subjected to a first H2S absorption to obtain the first-stage H2S-rich methanol (7) and pre-desulfurized gas; the pre-desulfurized gas, low-sulfur carbon-rich methanol (25) and first-stage CO2-rich methanol (9) are subjected to a second H2S absorption to obtain the second-stage H2S-rich methanol (10) and desulfurized gas (11); Preferably, the syngas (6) has a molar content of H2S of 0.9-1.2% and a molar content of CO2 of 40-50%; the temperature is -15 to -5℃ and the pressure is 5.3-5.7 MPa(G); Preferably, the desulfurization gas (11) has a molar content of H2S of 0.5-1 ppm and a molar content of CO2 of 38-44%; a temperature of -20 to -13°C; and a pressure of 5.3-5.4 MPa(G). Preferably, the molar content of H2S in the secondary H2S-rich methanol (10) is 1.5-2%, and the molar content of CO2 is 40-45%; the temperature is -12 to -7°C. Preferably, according to the material flow direction, the first-stage CO2-rich methanol (9) is sequentially pressurized to 5.6-6 MPa (G) and cooled to -36 to -33°C before being returned to the second H2S absorption. Preferably, the low-sulfur, carbon-rich methanol (25) is subjected to a second pressurization to 5.6-6 MPa (G) and then returned to the second H2S absorption. Preferably, the three-stage CO2 absorption includes: a first CO2 absorption, a second CO2 absorption, and a third CO2 absorption; More preferably, the first secondary CO2-rich methanol (21-i) is returned to the first CO2 absorber; the tertiary CO2-rich methanol (13) is returned to the second CO2 absorber; and the second semi-lean methanol (27-ii) is returned to the third CO2 absorber. More preferably, the desulfurized gas (11) and the first secondary CO2-rich methanol (21-i) are subjected to a first CO2 absorption to obtain the primary CO2-rich methanol (9) and the primary pre-purified gas; the primary pre-purified gas and the tertiary CO2-rich methanol (13) are subjected to a second CO2 absorption to obtain the secondary CO2-rich methanol (21) and the secondary pre-purified gas; the secondary pre-purified gas, the second semi-lean methanol (27-ii) and the second lean methanol (2-ii) are subjected to a third CO2 absorption to obtain the purified gas (14) and the tertiary CO2-rich methanol (13); Preferably, the first secondary CO2-rich methanol (21-i) is cooled to -22 to -18°C before the first CO2 absorption is performed; Preferably, the second secondary CO2-rich methanol (21-ii) is cooled to -36 to -33°C in a third cooling process before the CO2 flash evaporation is performed; Preferably, the third-stage CO2-rich methanol (13) is cooled to -36 to -33°C in a fourth cooling process before the second CO2 absorption is performed; Preferably, the CO2 molar content in the first-grade CO2-rich methanol (9) is 38-42%, the H2S molar content is 0.1-0.5 ppm, the temperature is -10 to -6℃, and the pressure is 5.3-5.4 MPa(G). Preferably, the secondary CO2-rich methanol (21) has a CO2 molar content of 29-34% and an H2S molar content of 0.1-0.5 ppm; the temperature is -10 to -5°C. Preferably, the molar flow ratio of the first secondary CO2-rich methanol stream (21-i) and the second secondary CO2-rich methanol stream (21-ii) is 1:2.3-2.7; Preferably, the purified gas (14) has a molar content of H2S ≤0.1ppm and a molar content of CO2 ≤20ppm; the temperature is -55 to -50℃ and the pressure is 5.2-5.3MPa(G).

5. The method according to any one of claims 1-4, wherein, The pressures for CO2 flash evaporation and H2S flash evaporation are each 1.6-2 MPa(G); Preferably, the molar content of H2S in the CO2 flash liquid (23) is 0.1-0.5 ppm, the molar content of CO2 is 28.5-33.5%, and the temperature is -36.5 to -33.5℃. Preferably, the molar flow ratio of the first CO2 flash liquid (23-i) and the second CO2 flash liquid (23-ii) is 3-4:1; Preferably, the secondary H2S-rich methanol (10) is cooled to -36 to -33°C in a fifth cooling process before the H2S flash evaporation is performed; Preferably, the molar content of H2S in the H2S flash liquid (12) is 1.45-1.95%, and the molar content of CO2 is 39.5-44.5%. The temperature ranges from -36.5 to -33.5℃; Preferably, the first washing process includes: performing a first-stage washing on the third semi-lean methanol (27-iii) and CO2 flash vapor to obtain carbon-rich methanol (24) and washed CO2 flash vapor (16-ii); performing a second-stage washing on the carbon-rich methanol (24) and H2S flash vapor to obtain the low-sulfur carbon-rich methanol (25) and washing gas; More preferably, the second semi-lean methanol stream (27-ii) and the third semi-lean methanol stream (27-iii) are each independently pressurized to 5.5-6 MPa(G) for the third CO2 absorption and the first washing, respectively; More preferably, the low-sulfur, carbon-rich methanol (25) has a molar content of H2S of ≤0.1% and a molar content of CO2 of 20-25%; and a temperature of -60 to -56°C. Preferably, the second washing process includes: subjecting the third non-conversion H2S-rich methanol (3-iii) and the washing gas to the second washing to obtain the second H2S-rich methanol (15) and washed H2S flash vapor (16-i); Preferably, the molar content of H2S in the second H2S-rich methanol (15) is 0.7-1%, the molar content of CO2 is 4-8%, and the temperature is -33 to -28°C.

6. The method according to any one of claims 1-5, wherein, The pressure of the first flash evaporation is selected from 0.05-0.08 MPa(G); the pressure of the second flash evaporation is selected from 0.06-0.09 MPa(G); and the pressure of the third flash evaporation is selected from 0.09-0.12 MPa(G). Preferably, the first CO2 flash liquid (23-i) is subjected to the first flash evaporation to obtain the semi-lean methanol (27) and the first CO2 product gas; the heat-exchanged CO2 flash liquid (29) is subjected to the second flash evaporation to obtain the flash liquid and the second CO2 product gas; the H2S flash liquid (12) is subjected to the third flash evaporation to obtain the first H2S-rich methanol (22) and the sulfur-containing gas phase; wherein, the flash liquid and the sulfur-containing gas phase are contacted to obtain the low-H2S methanol (28) and the third CO2 product gas; the CO2 product gas (26) includes the first CO2 product gas, the second CO2 product gas and the third CO2 product gas; Preferably, the semi-lean methanol (27) has a CO2 molar content of 19.5-23.5% and an H2S molar content of ≤1ppm; the temperature is -66 to -61℃. Preferably, the semi-lean methanol (27) is divided into a first semi-lean methanol stream (27-i), a second semi-lean methanol stream (27-ii), and a third semi-lean methanol stream (27-iii) with a molar flow ratio of 7-8:5-7:

1. Preferably, the molar content of H2S in the CO2 product gas (26) is ≤1ppm, the molar content of CO2 is 99.4-99.7%; the temperature is -66 to -62℃, and the pressure is 0.05-0.08MPa(G); Preferably, the low-H2S methanol (28) has a molar content of H2S of 0.4-0.6% and a molar content of CO2 of 25-29%; the temperature is -65 to -60°C and the pressure is 0.12-0.16 MPa(G); Preferably, the first H2S-rich methanol (22) has a molar content of 1.4-1.9% for H2S and a molar content of 29-34% for CO2; the temperature is -70 to -66°C and the pressure is 0.13-0.17 MPa(G); Preferably, the second heat-exchange H2S-rich methanol (31), the third heat-exchange H2S-rich methanol (32), the second H2S-rich methanol (15), the low H2S methanol (28), and nitrogen (18) are contacted and the gas stripping is performed to obtain the gas-stripped H2S-rich methanol (17) and the stripping gas. Preferably, the molar content of H2S in the stripped H2S-rich methanol (17) is 1-2%, and the molar content of CO2 is 2-5%; the temperature is -48 to -40°C. Preferably, the molar content of H2S in the third H2S-rich methanol (19) is 1-4%, the molar content of CO2 is 17-22%, and the temperature is -62 to -58°C; Preferably, the third washing also produces exhaust gas (20) with a molar content of H2S ≤1ppm and a molar content of CO2 of 84-89%; the temperature is -67 to -63℃.

7. A polygeneration acid gas removal device for supporting a water coal slurry gasification device, characterized in that, The apparatus includes: a non-shift gas scrubbing tower (T-1), an H2S absorption tower (T-2), a CO2 absorption tower (T-3), a CO2 medium-pressure flash tower (T-4), an H2S medium-pressure flash tower (T-5), and a reabsorption tower (T-6) connected together; the CO2 medium-pressure flash tower (T-4) is divided into a CO2 scrubbing section and a CO2 flash section connected by air risers from top to bottom; the H2S medium-pressure flash tower (T-5) is divided into a second H2S scrubbing section, a first H2S scrubbing section, and an H2S flash section connected by air risers from top to bottom; The non-shift gas scrubbing tower (T-1) is used to purify the non-shift gas (1) in two stages. The resulting non-shift H2S-rich methanol (3) is divided into three streams. The first stream of non-shift H2S-rich methanol (3-i) is recycled back to the non-shift gas scrubbing tower (T-1), the second stream of non-shift H2S-rich methanol (3-ii) is sent to the H2S absorption tower (T-2), and the third stream of non-shift H2S-rich methanol (3-iii) is sent to the second H2S scrubbing section. The H2S absorption tower (T-2) is used to absorb H2S from the synthesis gas (6) in two stages to obtain first-stage H2S-rich methanol (7), second-stage H2S-rich methanol (10) and desulfurized gas (11). The CO2 absorption tower (T-3) is used to absorb desulfurized gas (11) through three-stage CO2 absorption to obtain primary CO2-rich methanol (9), secondary CO2-rich methanol (21), tertiary CO2-rich methanol (13), and purified gas (14); wherein, the primary CO2-rich methanol (9) is recycled to the H2S absorption tower (T-2), and the secondary CO2-rich methanol (21) is divided into two streams, the first stream of secondary CO2-rich methanol (21-i) and the tertiary CO2-rich methanol (13) are each independently recycled to the CO2 absorption tower (T-3); The CO2 flash evaporation section is used to flash the second secondary CO2-rich methanol (21-ii) with CO2, and the resulting CO2 flash vapor enters the CO2 washing section, and the resulting CO2 flash liquid (23) is divided into two streams; the H2S flash evaporation section is used to flash the secondary H2S-rich methanol (10) with H2S, and the resulting H2S flash vapor enters the first H2S washing section, and the resulting H2S flash liquid (12) is obtained; The reabsorption tower (T-6) is divided into an upper tower and a lower tower. The upper tower is divided into a first flash section, a second flash section and a third flash section connected by a gas riser from top to bottom. It is used to perform the first flash evaporation, the second flash evaporation and the third flash evaporation of the first CO2 flash liquid (23-i), the second CO2 flash liquid (23-ii) and the H2S flash liquid (12) respectively to obtain semi-lean methanol (27), low H2S methanol (28), first H2S rich methanol (22) and CO2 product gas (26). The semi-lean methanol (27) is divided into three streams. The second semi-lean methanol (27-ii) is recycled to the CO2 absorption tower (T-3). The third semi-lean methanol (27-iii) passes through the CO2 washing section and the first H2S washing section in sequence, and is washed with the CO2 flash vapor and H2S flash vapor in sequence. The resulting low-sulfur carbon-rich methanol (25) is recycled to the H2S absorption tower (T-2). The resulting wash gas enters the second H2S washing section and is washed with the third non-conversion H2S-rich methanol (3-iii) in the second washing section to obtain the second H2S-rich methanol (15). The lower column of the reabsorption tower (T-6) is divided into a washing section and a stripping section connected by air risers from top to bottom. The stripping section connects the bottom of the washing section, the second H2S washing section, the second flash section and the third flash section. It is used to strip the third H2S-rich methanol (19), the second H2S-rich methanol (15), the low H2S methanol (28) and the first H2S-rich methanol (22) independently to obtain stripped H2S-rich methanol (17). The stripped gas enters the washing section and is washed with the first semi-lean methanol (27-i) for the third washing. The third H2S-rich methanol (19) is then recycled to the stripping section.

8. The apparatus according to claim 7, wherein, The non-shift gas scrubbing tower (T-1) is divided into a first purification section and a second purification section from bottom to top, which are connected by air risers. The first purification section is used to perform a first purification on the non-conversion gas (1) and the first stream of non-conversion H2S-rich methanol (3-i) to obtain pre-purified non-conversion H2S-rich methanol (4), and the obtained pre-purified non-conversion gas enters the second purification section to perform a second purification on the first stream of lean methanol (2-i) from the subsequent process to obtain purified non-conversion gas (5) and the non-conversion H2S-rich methanol (3).

9. The apparatus according to claim 8, wherein, The H2S absorption tower (T-2) is divided into a first H2S absorption section and a second H2S absorption section from bottom to top, which are connected by air risers. The first H2S absorption section is used to absorb the synthesis gas (6) and the second non-conversion H2S-rich methanol (3-ii) to obtain primary H2S-rich methanol (7), and the obtained pre-desulfurized gas enters the second H2S absorption section to absorb the low-sulfur carbon-rich methanol (25) and primary CO2-rich methanol (9) in sequence to obtain desulfurized gas (11) and secondary H2S-rich methanol (10). Preferably, according to the material flow direction, a first pump (P-1) and a first cooler (E-1) are sequentially installed on the pipeline connecting the CO2 absorption tower (T-3) and the second H2S absorption section, for sequentially pressurizing and cooling the first-stage CO2-rich methanol (9) before the second H2S absorption; Preferably, a second pump (P-2) is installed on the pipeline connecting the first H2S washing section and the second H2S absorption section, for the second H2S absorption of the low-sulfur carbon-rich methanol (25) after second pressurization; Preferably, the CO2 absorption tower (T-3) is divided into a first CO2 absorption section, a second CO2 absorption section, and a third CO2 absorption section from bottom to top, which are connected by air risers. The first CO2 absorption section is connected to the second CO2 absorption section and is used to perform first CO2 absorption on the desulfurized gas (11) and the first secondary CO2-rich methanol (21-i) to obtain the first primary CO2-rich methanol (9) and the first primary pre-purified gas; the second CO2 absorption section is connected to the third CO2 absorption section and is used to perform second CO2 absorption on the first primary pre-purified gas and the third primary CO2-rich methanol (13) to obtain the second secondary CO2-rich methanol (21) in two streams and the second primary pre-purified gas; the third CO2 absorption section is connected to the first flash section of the reabsorption tower (T-6) and the lean methanol from the subsequent process, and is used to perform third CO2 absorption on the second primary pre-purified gas, the second semi-lean methanol (27-ii) and the second lean methanol (2-ii) to obtain the third primary CO2-rich methanol (13) and purified gas (14); More preferably, a second cooler (E-2) is provided on the pipe connecting the second CO2 absorption section and the first CO2 absorption section, for cooling the first stream of secondary CO2-rich methanol (21-i) before absorbing the first CO2. More preferably, a third cooler (E-3) is provided on the pipe connecting the second CO2 absorption section and the CO2 flash evaporation section, for flash evaporation of the second secondary CO2-rich methanol (21-ii) after the second cooling process; More preferably, a fourth cooler (E-4) is provided on the pipe connecting the third CO2 absorption section and the second CO2 absorption section, for cooling the three-stage CO2-rich methanol (13) before performing the second CO2 absorption.

10. The apparatus according to any one of claims 7-9, wherein, A first heat exchanger (Q-1) is installed on the pipeline connecting the CO2 flash section, the third flash section, the second flash section and the gas stripping section. It is used to perform a first heat exchange between the second CO2 flash liquid (23-ii) and the first H2S-rich methanol (22). The resulting CO2 flash liquid (29) after heat exchange and the H2S-rich methanol (30) after the first heat exchange are respectively subjected to the second flash evaporation and gas stripping. Preferably, a second heat exchanger (Q-2) is also provided on the pipe connecting the first heat exchanger (Q-1) and the gas stripping section, for performing a second heat exchange on the H2S-rich methanol (30) after the first heat exchange, to obtain H2S-rich methanol (31) after the second heat exchange for gas stripping; Preferably, a third heat exchanger (Q-3) is provided on the pipe connecting the washing section and the gas stripping section for performing a third heat exchange on the third H2S-rich methanol (19) to obtain H2S-rich methanol (32) after the third heat exchange for gas stripping.

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