Energy-saving poly-generation acid gas removal technology matched with coal water slurry gasification device

Abstract

The invention relates to the technical field of low-temperature methanol washing, in particular to an energy-saving poly-generation acid gas removal method matched with a coal water slurry gasification device and energy-saving poly-generation acid matched with the coal water slurry gasification device. According to the method, a two-stage H2S absorption process is optimized, and the synthesis gas is treated by using low-sulfur carbon-rich methanol, so that the use amount of first-stage CO2-rich methanol is reduced; by optimizing the medium-pressure flash evaporation process and adopting the two-stage flash evaporation and classified washing technology, the low-temperature methanol washing device 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 an energy-saving multi-production acid gas removal method matched with a coal water slurry gasification device and an energy-saving multi-production acid gas removal device matched with a coal water slurry gasification device. BACKGROUND

[0002] Low-temperature methanol washing technology is a technology for absorbing and removing H2S and CO2 and other acid gases in synthesis gas by using low-temperature methanol as an absorbing solvent, while removing HCN, NH3 and other trace components. This technology has the advantages of high gas purification degree, good selectivity, large methanol absorption capacity and the like. In the low-temperature methanol washing process, the CO2-rich methanol can be recycled by pressure reduction flash evaporation, but the H2S-containing methanol must be recycled by rectification regeneration, which is the main source of energy consumption of low-temperature methanol washing.

[0003] With the diversification of the demand for the components of the coal water slurry gasification synthesis gas in the downstream device, the multi-production acid gas removal technology has also developed vigorously, but the efficient utilization of the non-shift CO2-rich methanol and the non-shift H2S-rich methanol in this technology still needs to be optimized. The design optimization of the medium-pressure flash evaporation process is also very critical and is closely related to the flash evaporation compression power consumption and the desorption effect of the reabsorption tower. The optimized design of the H2S absorption tower process is directly related to the use amount of the CO2-rich methanol and is also indirectly related to the total amount of the H2S-rich methanol. Therefore, there is still room for technical improvement and energy consumption reduction.

[0004] CN201110260570.0 discloses a low-temperature methanol washing process. Firstly, in this low-temperature methanol washing process, the H2S absorption tower uses CO2-rich methanol to wash the synthesis gas, and the H2S-rich methanol can be recycled only after being regenerated by heat, which is high in energy consumption. Secondly, in the CO2 flash evaporation 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, so that the CO2-rich methanol is contaminated by the H2S-rich methanol, and the low-concentration H2S methanol produced is not fully used, which is high in energy consumption. Thirdly, the medium-pressure flash evaporation process is simple in design, which increases the compression power of the subsequent flash gas, and is not conducive to the reduction of the comprehensive energy consumption of the low-temperature methanol washing device.

[0005] CN201810994082.4 discloses a low-temperature methanol washing system and a method for providing synthesis gas. This technology performs secondary utilization of the non-shift H2S-rich methanol after washing the non-shift gas, and uses the non-shift H2S-rich methanol as the flash gas of the H2S-rich methanol after medium-pressure flash evaporation to wash the methanol, and the non-shift H2S-rich methanol is completely mixed with the washed H2S-rich methanol, which is not conducive to the desorption of the low-temperature in the reabsorption tower. Therefore, there is still room for technical improvement and energy consumption reduction. SUMMARY

[0006] The present application aims to overcome the above technical problems, and provides an energy-saving multi-production acid gas removal method matched with a coal water slurry gasification device and an energy-saving multi-production acid gas removal device matched with a coal water slurry gasification device, the method reduces the amount of the first CO2-rich methanol by optimizing the two-stage H2S absorption process and using low-sulfur carbon-rich methanol to treat the synthesis gas; the low-temperature methanol washing device has the characteristics of low comprehensive energy consumption by optimizing the medium-pressure flash evaporation process and adopting two-stage flash evaporation and classified washing technology.

[0007] To achieve the above-mentioned purpose, the present application provides an energy-saving multi-production acid gas removal method matched with a coal water slurry gasification device, the method comprises:

[0008] The non-shift gas is subjected to three-stage purification to obtain pre-purified non-shift H2S-rich methanol, three groups of non-shift H2S-rich methanol, two groups of non-shift CO2-rich methanol and purified non-shift gas; 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, two groups of second CO2-rich methanol, third CO2-rich methanol and purified gas;

[0009] The first group of second CO2-rich methanol is subjected to two-stage CO2 flash evaporation to obtain first CO2 flash gas, second CO2 flash gas and two groups of second CO2 flash liquid; the second H2S-rich methanol is subjected to two-stage H2S flash evaporation to obtain first H2S flash gas, second H2S flash gas and second H2S flash liquid; wherein the first group of second CO2 flash liquid, the second group of second CO2 flash liquid and the second H2S flash liquid are subjected to first flash evaporation, second flash evaporation and third flash evaporation respectively to obtain two groups of semi-lean liquid methanol, low-sulfur methanol, first H2S-rich methanol and CO2 product gas; the low-carbon methanol obtained by gas stripping of the first group of semi-lean liquid methanol is returned to the three-stage CO2 absorption;

[0010] Wherein, the low-sulfur methanol, the first CO2 flash gas and the second CO2 flash gas are subjected to first washing to obtain low-sulfur carbon-rich methanol which is returned to the two-stage H2S absorption; the second group of non-shift H2S-rich methanol and the third group of non-shift H2S-rich methanol are subjected to second washing and third washing with the first H2S flash gas and the second H2S flash gas respectively;

[0011] Wherein, the first group of non-shift H2S-rich methanol and the second group of non-shift CO2-rich methanol are returned to the three-stage purification respectively; the first CO2-rich methanol is returned to the two-stage H2S absorption; the first group of non-shift CO2-rich methanol, the second group of second CO2-rich methanol and the third CO2-rich methanol are returned to the three-stage CO2 absorption respectively.

[0012] The second aspect of the present application provides an energy-saving multi-production acid gas removal device matched with a coal water slurry gasification device, the device comprising: connected non-shift gas purification tower, H2S absorption tower, CO2 absorption tower, first medium-pressure flash tower, second medium-pressure flash tower, reabsorption tower and low-carbon methanol stripping tower;

[0013] The non-shift gas purification tower is used for purifying the non-shift gas in three stages to obtain pre-purified non-shift H2S-rich methanol, three streams of non-shift H2S-rich methanol, two streams of non-shift CO2-rich methanol and purified non-shift gas; the H2S absorption tower is used for absorbing H2S in two stages to obtain first H2S-rich methanol, second H2S-rich methanol and desulfurized gas; the CO2 absorption tower is used for absorbing CO2 in three stages to obtain first CO2-rich methanol, two streams of second CO2-rich methanol, third CO2-rich methanol and purified gas;

[0014] The first medium-pressure flash tower is divided into first CO2 washing section, first CO2 flashing section, first H2S washing section and first H2S flashing section from top to bottom; the second medium-pressure flash tower is divided into second CO2 washing section, second CO2 flashing section, second H2S washing section and second H2S flashing section from top to bottom; wherein the first CO2 flashing section is connected with the second CO2 flashing section and is used for carrying out two-stage CO2 flashing on the first stream of second CO2-rich methanol to obtain first CO2 flashing gas, second CO2 flashing gas and two streams of second CO2 flashing liquid; the first H2S flashing section is connected with the second H2S flashing section and is used for carrying out two-stage H2S flashing on the second H2S-rich methanol to obtain first H2S flashing gas, second H2S flashing gas and second H2S flashing liquid;

[0015] The reabsorption tower is divided into first flashing section, second flashing section and third flashing section from top to bottom and is respectively used for carrying out first flashing, second flashing and third flashing on the first stream of second CO2 flashing liquid, second stream of second CO2 flashing liquid and second H2S flashing liquid to obtain two streams of semi-lean liquid methanol, low-sulfur methanol, first H2S-rich methanol and CO2 product gas; the low-carbon methanol stripping tower is used for stripping the first stream of semi-lean liquid methanol to obtain low-carbon methanol returning to the CO2 absorption tower;

[0016] Wherein, the second flashing section is connected with the first CO2 washing section and the second CO2 washing section and is used for carrying out first washing on the low-sulfur methanol, first CO2 flashing gas and second CO2 flashing gas to obtain low-sulfur carbon-rich methanol returning to the H2S absorption tower; the first H2S washing section is used for carrying out second washing on the second stream of non-shift H2S-rich methanol and first H2S flashing gas; the second H2S washing section is used for carrying out third washing on the third stream of non-shift H2S-rich methanol and second H2S flashing gas;

[0017] The first non-shift H2S-rich methanol and the second non-shift CO2-rich methanol are returned to the non-shift gas purification tower; the first-stage CO2-rich methanol is returned to the H2S absorption tower; the first non-shift CO2-rich methanol, the second-stage CO2-rich methanol and the third-stage CO2-rich methanol are returned to the CO2 absorption tower respectively.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] (1) The method provided by the present application divides the non-shift CO2-rich methanol from the non-shift gas purification process into two streams, and the first stream is used as a purification gas washing solvent. Compared with the prior art of using lean methanol / semi-lean liquid methanol for washing, the present application reduces the amount of lean methanol / semi-lean liquid methanol used under the premise of achieving the same washing effect, thereby reducing the energy consumption of the low-temperature methanol washing device.

[0020] (2) The method provided by the present application realizes the absorption of the sulfur-containing gas phase (e.g., H2S) generated by flashing the second-stage H2S flash liquid by flashing the second-stage CO2 flash liquid, without mixing with the first H2S-rich methanol after flashing, and at the same time, the low-sulfur methanol obtained is used for washing the first-stage CO2 flash gas and the second-stage CO2 flash gas in series.

[0021] (3) The method provided by the present application realizes the recycling of low-sulfur carbon-rich methanol by introducing low-sulfur carbon-rich methanol to absorb H2S gas in the synthesis gas, which reduces the amount of first-stage CO2-rich methanol used in two-stage H2S absorption compared with the prior art, and is beneficial to reducing the energy consumption of the device.

[0022] (4) The method provided by the present application uses non-shift H2S-rich methanol to wash the first-stage H2S flash gas and the second-stage H2S flash gas without mixing, which avoids diluting the carbon content of the second H2S-rich methanol and is of great significance to the low-temperature production of subsequent low-pressure desorption. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The present application provides an energy-saving multi-production acid gas removal device matched with a coal slurry gasification device.

[0024] REFERENCE SIGNS

[0025] T-1, Non-shift gas purification tower; T-2, H2S absorption tower; T-3, CO2 absorption tower; T-4, Primary medium-pressure flash evaporator; T-5, Secondary medium-pressure flash evaporator; T-6, Reabsorption tower; T-7, Low-carbon methanol stripping tower; E-1, First cooler; E-2, Second cooler; E-3, Third cooler; E-4, Fourth cooler; E-5, Fifth cooler; E-6, Sixth cooler; E-7, Seventh cooler; P-1, First pump; P-2, Second pump; P-3, Third pump; P-4, Fourth pump; Q, Heat exchanger;

[0026] 1. Non-shift gas; 2. Non-shift H2S-rich methanol; 2-i, First stream of non-shift H2S-rich methanol; 2-ii, Second stream of non-shift H2S-rich methanol; 2-iii, Third stream of non-shift H2S-rich methanol; 3. Lean methanol; 3-i, First stream of lean methanol; 3-ii, Second stream of lean methanol; 4. Pre-purified non-shift H2S-rich methanol; 5. Purified non-shift gas; 6. Syngas; 7. Primary H2S-rich methanol; 8. Non-shift CO2-rich methanol; 8-i, First stream of non-shift CO2-rich methanol; 8-ii, Second stream of non-shift CO2-rich methanol; 9. Primary CO2-rich methanol; 10. Secondary H2S-rich methanol; 11. Desulfurized gas; 12. Secondary CO2-rich methanol; 12-i, First stream of secondary CO2-rich methanol; 12-ii, Secondary CO2-rich methanol; 13. Semi-lean methanol; 13-i, First stream of semi-lean methanol ; 13-ii, Second semi-lean methanol; 14, Purified gas; 15, Tail gas; 16, Secondary CO2 flash vapor after washing; 17, Low-carbon methanol; 18, Primary H2S flash vapor after washing; 19, Primary H2S flash liquid; 20, First H2S-rich methanol; 21, Low-sulfur methanol; 22, CO2 product gas; 23, Primary CO2 flash vapor after washing; 24, Primary CO2 flash liquid; 25, Secondary H2S flash vapor after washing; 26, Nitrogen; 27, Primary washing liquid; 28, Tertiary CO2-rich methanol; 29, Secondary CO2 flash liquid; 29-i, First secondary CO2 flash liquid; 29-ii, Second secondary CO2 flash liquid; 30, Secondary H2S-rich methanol; 31, Secondary H2S flash liquid; 32, Low-sulfur carbon-rich methanol; 32-i, First low-sulfur carbon-rich methanol; 32-ii, Second low-sulfur carbon-rich methanol. Detailed Implementation

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] In the present application, "first", "second", "third", "fourth", "fifth", "sixth" and "seventh" do not indicate the order or limit the various materials or steps, but are used to distinguish or indicate that they are not the same step or material, unless otherwise specified.

[0029] In the present application, unless otherwise specified, the "top" of the container refers to the height of 0-10% from top to bottom of the container; the "upper part" of the container refers to the height of 10-40% from top to bottom of the container; the "middle part" of the container refers to the height of 40-60% from top to bottom of the container; the "lower part" of the container refers to the height of 60-90% from top to bottom of the container; the "bottom" of the container refers to the height of 90-100% from top to bottom of the container.

[0030] The first aspect of the present application provides an energy-saving multi-production acid gas removal method matched with a coal water slurry gasification device, the method comprising:

[0031] The non-shift gas is subjected to three-stage purification to obtain pre-purified non-shift H2S-rich methanol, three streams of non-shift H2S-rich methanol, two streams of non-shift CO2-rich methanol, and purified non-shift gas; the synthesis gas is subjected to two-stage H2S absorption to obtain first-stage H2S-rich methanol, second-stage H2S-rich methanol, and desulfurized gas; the desulfurized gas is subjected to three-stage CO2 absorption to obtain first-stage CO2-rich methanol, two streams of second-stage CO2-rich methanol, third-stage CO2-rich methanol, and purified gas;

[0032] The first stream of second-stage CO2-rich methanol is subjected to two-stage CO2 flashing to obtain first-stage CO2 flashing gas, second-stage CO2 flashing gas, and two streams of second-stage CO2 flashing liquid; the second-stage H2S-rich methanol is subjected to two-stage H2S flashing to obtain first-stage H2S flashing gas, second-stage H2S flashing gas, and second-stage H2S flashing liquid; wherein the first stream of second-stage CO2 flashing liquid, the second stream of second-stage CO2 flashing liquid, and the second-stage H2S flashing liquid are subjected to first flashing, second flashing, and third flashing, respectively, to obtain two streams of semi-lean liquid methanol, low-sulfur methanol, first H2S-rich methanol, and CO2 product gas; the low-carbon methanol obtained by gas stripping of the first stream of semi-lean liquid methanol is returned to the three-stage CO2 absorption;

[0033] The low-sulfur methanol, the first-stage CO2 flashing gas, and the second-stage CO2 flashing gas are subjected to first washing to obtain low-sulfur carbon-rich methanol, which is returned to the two-stage H2S absorption; the second stream of non-shift H2S-rich methanol and the third stream of non-shift H2S-rich methanol are subjected to second washing and third washing with the first-stage H2S flashing gas and the second-stage H2S flashing gas, respectively;

[0034] The first non-reformed H2S-rich methanol and the second non-reformed CO2-rich methanol are returned to the three-stage purification respectively; the first-stage CO2-rich methanol is returned to the two-stage H2S absorption; the first non-reformed CO2-rich methanol, the second-stage CO2-rich methanol and the third-stage CO2-rich methanol are returned to the three-stage CO2 absorption respectively.

[0035] In the present application, the synthesis gas and the non-reformed gas are derived from a coal water slurry gasification device without special circumstances.

[0036] In some embodiments of the present application, preferably, the three-stage purification comprises a first purification, a second purification and a third purification; the first non-reformed H2S-rich methanol is returned to the first purification; and the second non-reformed CO2-rich methanol is returned to the second purification.

[0037] In the present application, preferably, the H2S molar content in the non-reformed gas is 0.9-1.2%, the CO2 molar content is 5-10%, the temperature is -35 to -25℃ and the pressure is 5.6-6 MPa(G).

[0038] In some embodiments of the present application, further preferably, the non-reformed gas and the first non-reformed H2S-rich methanol are contacted and subjected to the first purification to obtain the pre-purified non-reformed H2S-rich methanol and the pre-desulfurized non-reformed gas; the pre-desulfurized non-reformed gas and the second non-reformed CO2-rich methanol are contacted and subjected to the second purification to obtain the non-reformed H2S-rich methanol and the desulfurized non-reformed gas; and the desulfurized non-reformed gas and the first methanol-lean gas are contacted and subjected to the third purification to obtain the non-reformed CO2-rich methanol and the purified non-reformed gas.

[0039] In the present application, the first purification aims to remove HCN, NH3 and other impurities and a small amount of H2S and CO2 in the non-reformed gas. Preferably, the molar flow ratio of the non-reformed gas to the first non-reformed H2S-rich methanol is 52-62:1; the H2S molar content in the pre-purified non-reformed H2S-rich methanol is 2.1-2.6%, the CO2 molar content is 3-7%, and it is sent to the subsequent process for treatment.

[0040] In the present application, the second purification aims to further remove H2S in the non-reformed gas. Preferably, the molar flow ratio of the second non-reformed CO2-rich methanol to the non-reformed gas is 1:1-2.

[0041] In some embodiments of the present application, preferably, the H2S molar content in the non-reformed H2S-rich methanol is 1.2-1.6%, the CO2 molar content is 4-9%, the temperature is -30 to -26℃ and the pressure is 5.6-6 MPa(G).

[0042] In some embodiments of the present application, further preferably, the molar flow ratio of the first stream of non-reformed H2S-rich methanol, the second stream of non-reformed H2S-rich methanol and the third stream of non-reformed H2S-rich methanol is 1:8-12:28-32.

[0043] In the present application, the third purification is intended to further remove CO2 in the non-reformed gas. Preferably, the molar flow ratio of the first stream of methanol-lean and the non-reformed gas is 1-2.5:1-2.

[0044] In some embodiments of the present application, preferably, the molar content of H2S in the methanol-lean is 0%, and the molar content of CO2 is 0%. In the present application, the methanol-lean is selected from subsequent processes. In the present application, without special circumstances, the methanol-lean is divided into the first stream of methanol-lean and the second stream of methanol-lean; the present application does not limit the molar flow ratio of the first stream of methanol-lean and the second stream of methanol-lean.

[0045] In some embodiments of the present application, preferably, the molar content of H2S in the non-reformed CO2-rich methanol is 0.5-1 ppm, and the molar content of CO2 is 5-9%; the temperature is -33 to -30℃; further preferably, the molar flow ratio of the first stream of non-reformed CO2-rich methanol and the second stream of non-reformed CO2-rich methanol is 1:1-2.

[0046] In some embodiments of the present application, preferably, the molar content of H2S in the purified non-reformed gas is ≤0.1 ppm, and the molar content of CO2 is ≤20 ppm; the temperature is -55 to -45℃, and the pressure is 5.5-5.9 MPa(G).

[0047] In some embodiments of the present application, preferably, the two-stage H2S absorption includes: the first H2S absorption and the second H2S absorption; wherein, the first-stage CO2-rich methanol returns to the second H2S absorption.

[0048] In the present application, the low-sulfur carbon-rich methanol is divided into two streams, which are returned to the first H2S absorption and the second H2S absorption, respectively. Preferably, the low-sulfur carbon-rich methanol is divided into the first stream of low-sulfur carbon-rich methanol and the second stream of low-sulfur carbon-rich methanol, which are returned to the second H2S absorption and the first H2S absorption, respectively.

[0049] In the present application, preferably, the molar content of H2S in the synthesis gas is 0.9-1.2%, and the molar content of CO2 is 40-50%; the temperature is -15 to -5℃, and the pressure is 5.4-5.6 MPa(G).

[0050] In some embodiments of the present application, further preferably, the synthesis gas and the second low-sulfur carbon-rich methanol are contacted and the first H2S absorption is carried out to obtain the primary H2S-rich methanol and the pre-desulfurized gas; the pre-desulfurized gas, the first low-sulfur carbon-rich methanol and the primary CO2-rich methanol are contacted and the second H2S absorption is carried out to obtain the desulfurized gas and the secondary H2S-rich methanol.

[0051] In the present application, the first H2S absorption is intended to remove HCN, NH3 and other impurities in the synthesis gas, as well as a small amount of H2S and CO2. Preferably, the molar flow ratio of the synthesis gas to the second low-sulfur carbon-rich methanol is 75-85:1; further preferably, the molar content of H2S in the primary H2S-rich methanol is 2.4-2.9%, and the molar content of CO2 is 70-75%, which is sent to subsequent processes for treatment.

[0052] In the present application, the second H2S absorption is intended to further remove H2S and CO2 in the synthesis gas. Preferably, the molar flow ratio of the first low-sulfur carbon-rich methanol to the synthesis gas is 1:2-3; and the molar flow ratio of the primary CO2-rich methanol to the synthesis gas is 1-1.3:2-3.

[0053] In some embodiments of the present application, further preferably, the low-sulfur carbon-rich methanol is first pressurized to 5.6-6 MPa (G) and divided into the first low-sulfur carbon-rich methanol and the second low-sulfur carbon-rich methanol with a molar flow ratio of 26-30:1.

[0054] In some embodiments of the present application, preferably, in the order of material flow direction, the primary CO2-rich methanol is second pressurized to 5.6-6 MPa (G), first cooled to -36 to -33℃, and subjected to the second H2S absorption.

[0055] In some embodiments of the present application, preferably, the molar content of H2S in the secondary H2S-rich methanol is 1-1.4%, and the molar content of CO2 is 36-42%; the temperature is -10 to -6℃.

[0056] 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 32-36%; the temperature is -22 to -18℃; and the pressure is 5.35-5.55 MPa (G).

[0057] In some embodiments of the present application, preferably, the three-stage CO2 absorption comprises: a first CO2 absorption, a second CO2 absorption and a third CO2 absorption; wherein the second-stage CO2-rich methanol is returned to the first CO2 absorption, and the third-stage CO2-rich methanol is returned to the second CO2 absorption; the first non-reformed CO2-rich methanol and the low-carbon methanol are returned to the third CO2 absorption.

[0058] In some embodiments of the present application, further preferably, the desulfurized gas and the second-stage CO2-rich methanol are contacted and subjected to the first CO2 absorption to obtain the first-stage CO2-rich methanol and a first pre-purified gas; the first pre-purified gas and the third-stage CO2-rich methanol are contacted and subjected to the second CO2 absorption to obtain the second-stage CO2-rich methanol and a second pre-purified gas; the second pre-purified gas, the first non-reformed CO2-rich methanol, the low-carbon methanol and the second lean methanol are contacted and subjected to the third CO2 absorption to obtain the third-stage CO2-rich methanol and a purified gas.

[0059] In the present application, preferably, the molar flow ratio of the desulfurized gas and the second-stage CO2-rich methanol is 2-3:1.

[0060] In some embodiments of the present application, preferably, the first-stage CO2-rich methanol has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 33-38%, a temperature of -15 to -10℃ and a pressure of 5.35-5.55 MPa(G).

[0061] In some embodiments of the present application, preferably, the second-stage CO2-rich methanol has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 28-33%, a temperature of -15 to -10℃; further preferably, the molar flow ratio of the first-stage second-stage CO2-rich methanol and the second-stage second-stage CO2-rich methanol is 2-3:1.

[0062] In some embodiments of the present application, further preferably, the first non-reformed CO2-rich methanol is subjected to a second cooling to -48 to -45℃ and subjected to the third CO2 absorption.

[0063] In some embodiments of the present application, preferably, the third-stage CO2-rich methanol is subjected to a third cooling to -36 to -33℃ and subjected to the second CO2 absorption.

[0064] In some embodiments of the present application, preferably, the second-stage second-stage CO2-rich methanol is subjected to a fourth cooling to -30 to -28℃ and subjected to the first CO2 absorption.

[0065] In some embodiments of the present application, preferably, the low-carbon methanol is further pressurized to 5.6-6 MPa (G) and returned to the third CO2 absorption.

[0066] In the present application, preferably, the molar flow ratio of the purified gas and the low-carbon methanol is 1-3:1; the molar flow ratio of the first non-shifted CO2-rich methanol and the purified gas is 1:7-9; and the molar flow ratio of the second lean methanol and the purified gas is 1-1.3:1.

[0067] In some embodiments of the present application, preferably, the H2S molar content in the purified gas is ≤0.1 ppm, the CO2 molar content is ≤20 ppm; the temperature is -55 to -50℃, and the pressure is 5.25-5.45 MPa (G).

[0068] In the present application, the two-stage CO2 flashing includes a first-stage CO2 flashing and a second-stage CO2 flashing. Preferably, the process of the two-stage CO2 flashing includes: subjecting the first second-stage CO2-rich methanol to the first-stage CO2 flashing to obtain a first-stage CO2 flashing gas and a first-stage CO2 flashing liquid; and subjecting the first-stage CO2 flashing liquid to the second-stage CO2 flashing to obtain the second-stage CO2 flashing gas and a second-stage CO2 flashing liquid.

[0069] In the present application, the pressure of the first-stage CO2 flashing is greater than the pressure of the second-stage CO2 flashing. Preferably, the pressure of the first-stage CO2 flashing is 3.5-3.8 MPa (G); and the pressure of the second-stage CO2 flashing is 1.6-2 MPa (G).

[0070] In some embodiments of the present application, preferably, the first second-stage CO2-rich methanol is cooled to -36 to -33℃ and subjected to the first-stage CO2 flashing.

[0071] In some embodiments of the present application, preferably, the H2S molar content in the first-stage CO2 flashing liquid is 0.1-0.5 ppm, the CO2 molar content is 22.5-27.5%, and the temperature is -38 to -34℃.

[0072] In some embodiments of the present application, preferably, the H2S molar content in the second-stage CO2 flashing liquid is 0.1-0.5 ppm, the CO2 molar content is 22-27%, and the temperature is -38.5 to -34.5℃.

[0073] In some embodiments of the present application, further preferably, the molar flow ratio of the first second-stage CO2 flashing liquid and the second second-stage CO2 flashing liquid is 2-4:1.

[0074] In the present application, the two-stage H2S flashing includes a first-stage H2S flashing and a second-stage H2S flashing. Preferably, the process of the two-stage H2S flashing includes: performing the first-stage H2S flashing on the second-stage H2S-rich methanol to obtain a first-stage H2S flashing gas and a first-stage H2S flashing liquid; performing the second-stage H2S flashing on the first-stage H2S flashing liquid to obtain the second-stage H2S flashing gas and a second-stage H2S flashing liquid.

[0075] In the present application, the pressure of the first-stage H2S flashing is greater than the pressure of the second-stage H2S flashing. Preferably, the pressure of the first-stage H2S flashing is 3.5-3.8 MPa (G); and the pressure of the second-stage H2S flashing is 1.6-2 MPa (G).

[0076] In some embodiments of the present application, preferably, the second-stage H2S-rich methanol is cooled to -31 to -28℃ by the sixth cooling to perform the first-stage H2S flashing.

[0077] In some embodiments of the present application, preferably, the first-stage H2S flashing liquid has a molar content of H2S of 0.95-1.35%, a molar content of CO2 of 35-40%, and a temperature of -33 to -28℃.

[0078] In some embodiments of the present application, preferably, the second-stage H2S flashing liquid has a molar content of H2S of 0.9-1.3%, a molar content of CO2 of 34.5-39.5%, and a temperature of -34 to -29℃.

[0079] In some embodiments of the present application, preferably, the first-stage CO2 flashing liquid is subjected to the first flashing to obtain the semi-lean liquid methanol and a first-stage CO2 product gas; the second-stage CO2 flashing liquid is subjected to the second flashing to obtain a flashing liquid and a second-stage CO2 product gas; and the H2S flashing liquid is subjected to the third flashing to obtain the first H2S-rich methanol and a sulfur-containing gas phase; wherein the flashing liquid and the sulfur-containing gas phase are contacted to obtain low-sulfur methanol and a third-stage CO2 product gas; and wherein the first-stage CO2 product gas, the second-stage CO2 product gas, and the third-stage CO2 product gas are mixed to obtain a CO2 product gas.

[0080] In some embodiments of the present application, preferably, the second-stage CO2 flashing liquid is cooled to -52 to -50℃ by the seventh cooling to perform the second flashing.

[0081] In some embodiments of the present application, preferably, the semi-lean liquid methanol has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 14-18%, a temperature of -62 to -58℃, and a pressure of 0.05-0.08 MPa (G).

[0082] In some embodiments of the present application, further preferably, the molar flow ratio of the first and second semi-lean methanol is 1-2:1.

[0083] In some embodiments of the present application, preferably, the molar content of H2S in the low-sulfur methanol is 0.3-0.5%, the molar content of CO2 is 18-23%, the temperature is -60 to -55℃, and the pressure is 0.12-0.16 MPa (G).

[0084] In some embodiments of the present application, preferably, the molar content of H2S in the first H2S-rich methanol is 0.85-1.25%, the molar content of CO2 is 24-28%, the temperature is -68 to -64℃, and the pressure is 0.13-0.17 MPa (G).

[0085] In some embodiments of the present application, preferably, the molar content of H2S in the CO2 product gas is ≤1 ppm, the molar content of CO2 is 99.4-99.7%, the temperature is -65 to -60℃, and the pressure is 0.05-0.08 MPa (G).

[0086] In some embodiments of the present application, preferably, the first semi-lean methanol is contacted with nitrogen and subjected to the gas stripping to obtain tail gas and low-carbon methanol; further preferably, the first semi-lean methanol is heat-exchanged to -50 to -48℃ before being subjected to the gas stripping.

[0087] In some embodiments of the present application, further preferably, the molar content of H2S in the low-carbon methanol is 0.1-0.5 ppm, and the molar content of CO2 is 3-7%; the temperature is -65 to -60℃.

[0088] In some embodiments of the present application, further preferably, the molar content of H2S in the tail gas is 0.1-0.5 ppm, and the molar content of CO2 is 80-85%; the temperature is -60 to -50℃, and the pressure is 0.12-0.14 MPa (G), which is sent to subsequent processes.

[0089] In some embodiments of the present application, preferably, the process of the first washing comprises: once washing the low-sulfur methanol and the primary CO2 flash gas to obtain once-washed liquid and washed primary CO2 flash gas; twice washing the once-washed liquid and the secondary CO2 flash gas to obtain the low-sulfur carbon-rich methanol and washed secondary CO2 flash gas.

[0090] In some embodiments of the present application, further preferably, the low-sulfur methanol is pressurized to 3.8-4 MPa (G) for the once washing.

[0091] In some embodiments of the present application, it is further preferred that the molar content of H2S in the first washing liquid is 0.3-0.6%, the molar content of CO2 is 18.5-23.5%, and the temperature is -60 to -55°C.

[0092] In some embodiments of the present application, it is further preferred that the molar content of H2S in the first washing liquid is 0.3-0.6%, the molar content of CO2 is 18.5-23.5%, and the temperature is -60 to -55°C.

[0093] In some embodiments of the present application, it is further preferred that the molar content of H2S in the first washing liquid is 0.3-0.6%, the molar content of CO2 is 18.5-23.5%, and the temperature is -60 to -55°C.

[0094] In some embodiments of the present application, it is further preferred that the molar content of H2S in the first washing liquid is 0.3-0.6%, the molar content of CO2 is 18.5-23.5%, and the temperature is -60 to -55°C.

[0095] In some embodiments of the present application, it is preferred that the process of the second washing comprises: contacting the second non-reformed H2S-rich methanol and the first H2S flash gas and performing the second washing to obtain the first washing H2S flash gas and the second washing liquid mixed into the first H2S flash liquid.

[0096] In some embodiments of the present application, it is further preferred that the molar content of H2S in the first washing liquid is 0.3-0.6%, the molar content of CO2 is 18.5-23.5%, and the temperature is -60 to -55°C.

[0097] In some embodiments of the present application, it is further preferred that the molar content of H2S in the first washing liquid is 0.3-0.6%, the molar content of CO2 is 18.5-23.5%, and the temperature is -60 to -55°C.

[0098] In some embodiments of the present application, it is preferred that the process of the third washing comprises: contacting the third non-reformed H2S-rich methanol and the second H2S flash gas and performing the third washing to obtain the second H2S-rich methanol and the second washing H2S flash gas.

[0099] In some embodiments of the present application, further preferably, the molar content of H2S in the post-washing secondary H2S flash gas is 0.8-1.2%, the molar content of CO2 is 14-18%, the molar content of CO is 34-38%, and the molar content of H2 is 43-48%; the temperature is -35 to -25℃, and the pressure is 1.6-2 MPa (G);

[0100] In some embodiments of the present application, further preferably, the molar content of H2S in the secondary H2S-rich methanol is 1.2-1.6%, and the molar content of CO2 is 7-12%; the temperature is -25 to -20℃, and the post-process is sent to a subsequent process.

[0101] The present application provides a structure diagram of an energy-saving multi-production acid gas removal device matched with a coal water slurry gasification device as shown in Figure 1 The device comprises a connected non-shifted gas purification tower T-1, an H2S absorption tower T-2, a CO2 absorption tower T-3, a first medium-pressure flash tower T-4, a second medium-pressure flash tower T-5, a reabsorption tower T-6, and a low-carbon methanol stripping tower T-7.

[0102] The non-shifted gas purification tower T-1 is used for purifying the non-shifted gas 1 in three stages to obtain pre-purified non-shifted H2S-rich methanol 4, non-shifted H2S-rich methanol 2 in three streams, non-shifted CO2-rich methanol 8 in two streams, and purified non-shifted gas 5; the H2S absorption tower T-2 is used for absorbing H2S in two stages from the synthesis gas 6 to obtain first H2S-rich methanol 7, second H2S-rich methanol 10, and desulfurized gas 11; the CO2 absorption tower T-3 is used for absorbing CO2 in three stages from the desulfurized gas 11 to obtain first CO2-rich methanol 9, second CO2-rich methanol 12 in two streams, third CO2-rich methanol 28, and purified gas 14.

[0103] The first medium-pressure flash tower T-4 is divided into a first CO2 washing section, a first CO2 flash section, a first H2S washing section, and a first H2S flash section from top to bottom; the second medium-pressure flash tower T-5 is divided into a second CO2 washing section, a second CO2 flash section, a second H2S washing section, and a second H2S flash section from top to bottom; wherein the first CO2 flash section is connected to the second CO2 flash section and is used for performing two-stage CO2 flashing on the first stream of second CO2-rich methanol 12-i to obtain first CO2 flash gas, second CO2 flash gas, and second CO2 flash liquid 29 in two streams; the first H2S flash section is connected to the second H2S flash section and is used for performing two-stage H2S flashing on the second H2S-rich methanol 10 to obtain first H2S flash gas, second H2S flash gas, and second H2S flash liquid 31.

[0104] The reabsorption tower T-6 is divided into a first flash evaporation section, a second flash evaporation section and a third flash evaporation section from top to bottom, respectively used for first flash evaporation, second flash evaporation and third flash evaporation of the first secondary CO2 flash liquid 29-i, the second secondary CO2 flash liquid 29-ii and the secondary H2S flash liquid 31 respectively, to obtain two groups of semi-lean liquid methanol 13, low-sulfur methanol 21, first H2S-rich methanol 20 and CO2 product gas 22; the low-carbon methanol stripping tower T-7 is used for stripping the first group of semi-lean liquid methanol 13-i to obtain low-carbon methanol 17 returned to the CO2 absorption tower T-3;

[0105] The second flash evaporation section connects the first CO2 washing section and the second CO2 washing section, and is used for first washing of the low-sulfur methanol 21, the primary CO2 flash gas and the secondary CO2 flash gas to obtain low-sulfur carbon-rich methanol 32 returned to the H2S absorption tower T-2; the first H2S washing section is used for second washing of the second group of non-shift H2S-rich methanol 2-ii and the primary H2S flash gas; and the second H2S washing section is used for third washing of the third group of non-shift H2S-rich methanol 2-iii and the secondary H2S flash gas.

[0106] The first group of non-shift H2S-rich methanol 2-i and the second group of non-shift CO2-rich methanol 8-ii are returned to the non-shift gas purification tower T-1; the primary CO2-rich methanol 9 is returned to the H2S absorption tower T-2; the first group of non-shift CO2-rich methanol 8-i, the second group of secondary CO2-rich methanol 12-ii and the tertiary CO2-rich methanol 28 are returned to the CO2 absorption tower T-3 respectively.

[0107] In the present application, as shown in Figure 1 Preferably, the non-shift gas purification tower T-1 is divided into a first purification section, a second purification section and a third purification section from bottom to top, which are communicated by gas lift holes; the first group of non-shift H2S-rich methanol 2-i is returned to the first purification section; and the second group of non-shift CO2-rich methanol 8-ii is returned to the second purification section.

[0108] In the present application, as shown in Figure 1 In the non-shift gas purification tower T-1, the first purification section is used for contacting the non-shift gas 1 and the first group of non-shift H2S-rich methanol 2-i and performing first purification to obtain pre-purified non-shift H2S-rich methanol 4 and pre-desulfurized non-shift gas; the second purification section is used for contacting the pre-desulfurized non-shift gas and the second group of non-shift CO2-rich methanol 8-ii and performing second purification to obtain the non-shift H2S-rich methanol 2 and desulfurized non-shift gas; and the third purification section is used for contacting the desulfurized non-shift gas and the first group of lean methanol 3-i and performing third purification to obtain the non-shift CO2-rich methanol 8 and purified non-shift gas 5.

[0109] In the present application, as shown inFigure 1 As shown in the figure, the H2S absorption tower T-2 is divided into a first H2S absorption section and a second H2S absorption section communicated by a riser hole from bottom to top; wherein the second low-sulfur carbon-rich methanol 32-ii returns to the first H2S absorption section; the primary CO2-rich methanol 9 and the first low-sulfur carbon-rich methanol 32-i return to the second H2S absorption section respectively.

[0110] In the present application, as shown in the figure, Figure 1 As shown in the figure, in the H2S absorption tower T-2, the first H2S absorption section is used for contacting the synthesis gas 6 and the second low-sulfur carbon-rich methanol 32-ii and carrying out first H2S absorption to obtain the primary H2S-rich methanol 7 and the pre-desulfurization gas; the second H2S absorption section is used for contacting the pre-desulfurization gas, the primary CO2-rich methanol 9 and the first low-sulfur carbon-rich methanol 32-i and carrying out second H2S absorption to obtain the desulfurization gas 11 and the secondary H2S-rich methanol 10.

[0111] In the present application, as shown in the figure, Figure 1 As shown in the figure, 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 communicated by a riser hole from bottom to top; wherein the second secondary CO2-rich methanol 12-ii returns to the first CO2 absorption section, and the tertiary CO2-rich methanol 28 returns to the second CO2 absorption section; the first non-shift CO2-rich methanol 8-i and the low-carbon methanol 17 return to the third CO2 absorption section.

[0112] In the present application, as shown in the figure, Figure 1 As shown in the figure, in the CO2 absorption tower T-3, the first CO2 absorption section is used for contacting the desulfurization gas 11 and the second secondary CO2-rich methanol 12-ii and carrying out first CO2 absorption to obtain the primary CO2-rich methanol 9 and the first pre-purification gas; the second CO2 absorption section is used for contacting the first pre-purification gas and the tertiary CO2-rich methanol 28 and carrying out second CO2 absorption to obtain the secondary CO2-rich methanol 12 and the second pre-purification gas; the third CO2 absorption section is used for contacting the second pre-purification gas, the first non-shift CO2-rich methanol 8-i, the low-carbon methanol 17 and the second lean methanol 3-ii and carrying out third CO2 absorption to obtain the tertiary CO2-rich methanol 28 and the purified gas 14.

[0113] In the present application, as shown in the figure, Figure 1As shown in the figure, the primary medium-pressure flash tower T-4 is divided into a first CO2 washing section, a first CO2 flash section, a first H2S washing section and a first H2S flash section from top to bottom; wherein the first CO2 flash section is used for carrying out primary CO2 flashing on the first secondary CO2-rich methanol 12-i, to obtain primary CO2 flash liquid 24 and primary CO2 flash gas; the first H2S flash section is used for carrying out primary H2S flashing on the secondary H2S-rich methanol 10, to obtain primary H2S flash liquid 19 and primary H2S flash gas; the first CO2 washing section is used for carrying out primary washing on the low-sulfur methanol 21 and the primary CO2 flash gas, to obtain primary washing liquid 27 and washed primary CO2 flash gas 23; and the first H2S washing section is used for carrying out secondary washing on the second non-shift H2S-rich methanol 2-ii and the primary H2S flash gas, to obtain washed primary H2S flash gas 18, and the obtained secondary washing liquid is mixed into the primary H2S flash liquid 19.

[0114] In the present application, as shown in the figure, Figure 1 As shown in the figure, the secondary medium-pressure flash tower T-5 is divided into a second CO2 washing section, a second CO2 flash section, a second H2S washing section and a second H2S flash section from top to bottom; wherein the second CO2 flash section is used for carrying out secondary CO2 flashing on the primary CO2 flash liquid 24, to obtain secondary CO2 flash liquid 29 and secondary CO2 flash gas; the second H2S flash section is used for carrying out secondary H2S flashing on the primary H2S flash liquid 19, to obtain secondary H2S flash liquid 31 and secondary H2S flash gas; the second CO2 washing section is used for carrying out secondary washing on the primary washing liquid 27 and the secondary CO2 flash gas, to obtain low-sulfur carbon-rich methanol 32 and washed secondary CO2 flash gas 16; and the second H2S washing section is used for carrying out tertiary washing on the third non-shift H2S-rich methanol 2-iii and the secondary H2S flash gas, to obtain washed secondary H2S flash gas 25 and second H2S-rich methanol 30.

[0115] According to the present application, as shown in the figure, Figure 1 As shown in the figure, the reabsorption tower T-6 is divided into a first flash section, a second flash section and a third flash section from top to bottom; wherein the first flash section is used for carrying out first flashing on the first secondary CO2 flash liquid 29-i, to obtain semi-lean liquid methanol 13 and a first CO2 product gas; the second flash section is used for carrying out second flashing on the second secondary CO2 flash liquid 29-ii, to obtain flash liquid and a second CO2 product gas; and the third flash section is used for carrying out third flashing on the secondary H2S flash liquid 31, to obtain first H2S-rich methanol 20, and the sulfur-containing gas phase obtained is contacted with the flash liquid through a rising hole, to obtain low-sulfur methanol 21 and a third CO2 product gas; wherein the first CO2 product gas, the second CO2 product gas and the third CO2 product gas are mixed to obtain CO2 product gas 22.

[0116] According to the present application, as shown in the figure,Figure 1 As shown, the low-carbon methanol stripping column T-7 is used to contact and strip the first stream of semi-lean methanol 13-i and nitrogen 26 to obtain tail gas 15 and low-carbon methanol 17.

[0117] According to the present application, preferably, as shown in the figure, a first pump P-1 is arranged on the pipeline connecting the second CO2 washing section, the second H2S absorption section and the first H2S absorption section in the direction of material flow, for dividing the low-sulfur carbon-rich methanol 32 into the first stream of low-sulfur carbon-rich methanol 32-i and the second stream of low-sulfur carbon-rich methanol 32-ii after first pressurization, and returning them to the second H2S absorption section and the first H2S absorption section, respectively. Figure 1 According to the present application, preferably, as shown in the figure, a second pump P-2 and a first cooler E-1 are arranged in sequence on the pipeline connecting the second H2S absorption section and the first CO2 absorption section in the direction of material flow, for sequentially performing second pressurization and first cooling on the primary CO2-rich methanol 9 after the second H2S absorption.

[0118] Figure 1 According to the present application, preferably, as shown in the figure, a second cooler E-2 is arranged on the pipeline connecting the third purification section and the third CO2 absorption section, for performing the third CO2 absorption on the first stream of non-shift CO2-rich methanol 8-i after second cooling.

[0119] According to the present application, preferably, as shown in the figure, a third pump P-3 is arranged on the pipeline connecting the low-carbon methanol stripping column T-7 and the third CO2 absorption section, for performing the third CO2 absorption on the low-carbon methanol 17 after third pressurization. Figure 1 According to the present application, preferably, as shown in the figure, a third cooler E-3 is arranged on the pipeline connecting the third CO2 absorption section and the second CO2 absorption section in the direction of material flow, for performing the second CO2 absorption on the tertiary CO2-rich methanol 28 after third cooling.

[0120] Figure 1 According to the present application, preferably, as shown in the figure, a fourth cooler E-4 is arranged on the pipeline connecting the second CO2 absorption section and the first CO2 absorption section in the direction of material flow, for performing the first CO2 absorption on the second stream of secondary CO2-rich methanol 12-ii after fourth cooling.

[0121] According to the present application, preferably, as shown in the figure, a fourth cooler E-4 is arranged on the pipeline connecting the second CO2 absorption section and the first CO2 absorption section in the direction of material flow, for performing the first CO2 absorption on the second stream of secondary CO2-rich methanol 12-ii after fourth cooling. Figure 1 According to the present application, preferably, as shown in the figure, a fourth cooler E-4 is arranged on the pipeline connecting the second CO2 absorption section and the first CO2 absorption section in the direction of material flow, for performing the first CO2 absorption on the second stream of secondary CO2-rich methanol 12-ii after fourth cooling.

[0122] Figure 1 According to the present application, preferably, as shown in the figure, a fourth cooler E-4 is arranged on the pipeline connecting the second CO2 absorption section and the first CO2 absorption section in the direction of material flow, for performing the first CO2 absorption on the second stream of secondary CO2-rich methanol 12-ii after fourth cooling.

[0123] According to the present application, preferably, as shown in the figure, a fourth cooler E-4 is arranged on the pipeline connecting the second CO2 absorption section and the first CO2 absorption section in the direction of material flow, for performing the first CO2 absorption on the second stream of secondary CO2-rich methanol 12-ii after fourth cooling. Figure 1 ​​​As shown, a fifth cooler E-5 is installed on the pipeline connecting the second CO2 absorption section and the first CO2 flash evaporation section. This cooler is used to cool the first stream of secondary CO2-rich methanol 12-i before performing the primary CO2 flash evaporation.

[0124] According to the present invention, preferably, such as Figure 1 As shown, a sixth cooler E-6 is installed on the pipeline connecting the second H2S absorption section and the first H2S flash evaporation section, which is used to cool the secondary H2S-rich methanol 10 in the sixth cooling process before performing the primary H2S flash evaporation.

[0125] According to the present invention, preferably, such as Figure 1 As shown, a seventh cooler E-7 is installed on the pipeline connecting the second CO2 flash section and the second flash section, which is used to cool the second secondary CO2 flash liquid 29-ii before performing the second flash evaporation.

[0126] According to the present invention, preferably, such as Figure 1 As shown, a heat exchanger Q is installed on the pipeline connecting the first flash section and the low-carbon methanol stripping tower T-7, which is used to strip the first semi-lean methanol 13-i after heat exchange.

[0127] The present invention will be described in detail below through embodiments.

[0128] In this invention, unless otherwise specified, both the syngas and the non-conversion gas are derived from the coal-water slurry gasification unit.

[0129] Example 1

[0130] Devices such as Figure 1 As shown, the apparatus includes: a non-shift gas purification tower T-1, an H2S absorption tower T-2, a CO2 absorption tower T-3, a primary medium-pressure flash evaporator T-4, a secondary medium-pressure flash evaporator T-5, a reabsorption tower T-6, a low-carbon methanol stripping tower T-7, a first cooler E-1, a second cooler E-2, a third cooler E-3, a fourth cooler E-4, a fifth cooler E-5, a sixth cooler E-6, and a seventh cooler E-7, a first pump P-1, a second pump P-2, a third pump P-3, and a fourth pump P-4, and a heat exchanger Q;

[0131] The method is carried out in the above-described apparatus and includes:

[0132] The non-shifted gas 1 (molar content of H2S is 0.9-1.2%, molar content of CO2 is 5-10%; temperature is -35 to -25℃, pressure is 5.6-6 MPa(G)) and the first stream of non-shifted H2S-rich methanol 2-i are contacted at a molar flow ratio of 52-62:1 and subjected to first purification, to obtain pre-purified non-shifted H2S-rich methanol 4 (molar content of H2S is 2.1-2.6%, molar content of CO2 is 3-7%) and pre-desulfurized non-shifted gas; the above pre-desulfurized non-shifted gas and the second stream of non-shifted CO2-rich methanol 8-ii are contacted and subjected to second purification, to obtain non-shifted H2S-rich methanol 2 (molar content of H2S is 1.2-1.6%, molar content of CO2 is 4-9%; temperature is -30 to -26℃; pressure is 5.6-6 MPa(G)) and desulfurized non-shifted gas; the above desulfurized non-shifted gas and the first stream of methanol-lean 3-i are contacted and subjected to third purification, to obtain non-shifted CO2-rich methanol 8 (molar content of H2S is 0.5-1 ppm, molar content of CO2 is 5-8%; temperature is -33 to -30℃) and purified non-shifted gas 5 (molar content of H2S is ≤0.1 ppm, molar content of CO2 is ≤20 ppm; temperature is -55 to -45℃, pressure is 5.5-5.9 MPa(G));

[0133] wherein the above non-shifted H2S-rich methanol 2 is divided into the first stream of non-shifted H2S-rich methanol 2-i, the second stream of non-shifted H2S-rich methanol 2-ii and the third stream of non-shifted H2S-rich methanol 2-iii at a molar flow ratio of 1:8-12:28-32; wherein the above non-shifted CO2-rich methanol 8 is divided into the first stream of non-shifted CO2-rich methanol 8-i and the second stream of non-shifted CO2-rich methanol 8-ii at a molar flow ratio of 1:1-2;

[0134] wherein the molar flow ratio of the above second stream of non-shifted CO2-rich methanol 8-ii and non-shifted gas 1 is 1:1-2; the molar flow ratio of the above first stream of methanol-lean 3-i and non-shifted gas 1 is 1-1.5:1-2;

[0135] The above synthesis gas 6 (molar content of H2S is 0.9-1.2%, molar content of CO2 is 40-50%; temperature is -15 to -5°C, pressure is 5.4-5.6 MPa(G)) and the second low-sulfur carbon-rich methanol 32-ii are contacted at a molar flow ratio of 75-85:1 and subjected to a first H2S absorption to obtain a pre-desulfurized gas and a primary H2S-rich methanol 7 (molar content of H2S is 2.4-2.9%, molar content of CO2 is 70-75%); the above pre-desulfurized gas, the first low-sulfur carbon-rich methanol 32-i and the primary CO2-rich methanol 9 (in turn subjected to a second pressurization to 5.6-6 MPa(G), a first cooling to -36 to -33°C) are contacted and subjected to a second H2S absorption to obtain a desulfurized gas 11 (molar content of H2S is 0.5-1 ppm, molar content of CO2 is 32-36%; temperature is -22 to -18°C; pressure is 5.35-5.55 MPa(G)) and a secondary H2S-rich methanol 10 (molar content of H2S is 1-1.4%, molar content of CO2 is 36-42%; temperature is -12 to -8°C);

[0136] The molar flow ratio of the above first low-sulfur carbon-rich methanol 32-i and the synthesis gas 6 is 1:2-3; the molar flow ratio of the primary CO2-rich methanol 9 and the synthesis gas 6 is 1-1.3:2-3; the above low-sulfur carbon-rich methanol 32 is subjected to a first pressurization to 5.6-6 MPa(G) and is divided into the first low-sulfur carbon-rich methanol 32-i and the second low-sulfur carbon-rich methanol 32-ii at a molar flow ratio of 26-30:1;

[0137] The desulfurized gas 11 and the second CO2-rich methanol 12-ii (cooled to -30 to -28°C) are contacted at a molar flow ratio of 2-3:1 and a first CO2 absorption is carried out to obtain a first CO2-rich methanol 9 (H2S molar content of 0.1-0.5 ppm, CO2 molar content of 33-38%, temperature of -15 to -10°C, pressure of 5.35-5.55 MPa (G)) and a first pre-purified gas; the first pre-purified gas and the third CO2-rich methanol 28 (cooled to -36 to -33°C) are contacted and a second CO2 absorption is carried out to obtain a second CO2-rich methanol 12 (H2S molar content of 0.1-0.5 ppm, CO2 molar content of 23-28%, temperature of -15 to -10°C) and a second pre-purified gas; the second pre-purified gas, the first non-shift CO2-rich methanol 8-i (cooled to -48 to -45°C), the low carbon methanol 17 (pressurized to 5.6-6 MPa (G)) and the second lean methanol 3-ii are contacted and a third CO2 absorption is carried out to obtain a third CO2-rich methanol 28 and a purified gas 14 (H2S molar content of ≤0.1 ppm, CO2 molar content of ≤20 ppm; temperature of -55 to -50°C, pressure of 5.25-5.45 MPa (G));

[0138] wherein the molar flow ratio of the low carbon methanol 17 and the purified gas 14 is 1:1-3; the molar flow ratio of the first non-shift CO2-rich methanol 8-i and the purified gas 14 is 1:7-9; the molar flow ratio of the second lean methanol 3-ii and the purified gas 14 is 1-1.3:1;

[0139] wherein the second CO2-rich methanol 12 is divided into a first second CO2-rich methanol 12-i and a second second CO2-rich methanol 12-ii at a molar flow ratio of 2-3:1;

[0140] The first second CO2-rich methanol 12-i (cooled to -36 to -33°C) is subjected to a first CO2 flashing (pressure of 3.5-3.8 MPa (G)) to obtain a first CO2 flashing gas and a first CO2 flashing liquid 24 (H2S molar content of 0.1-0.5 ppm, CO2 molar content of 22.5-27.5%, temperature of -38 to -34°C); the first CO2 flashing liquid 24 is subjected to a second CO2 flashing (pressure of 1.6-2 MPa (G)) to obtain a second CO2 flashing gas and a second CO2 flashing liquid 29 (H2S molar content of 0.1-0.5 ppm, CO2 molar content of 22-27%, temperature of -38.5 to -34.5°C);

[0141] wherein the above secondary CO2 flash liquid 29 is divided into a first secondary CO2 flash liquid 29-i and a second secondary CO2 flash liquid 29-ii in a molar flow ratio of 2-4:1;

[0142] The above secondary H2S-rich methanol 10 (cooled to -31 to -28°C) is subjected to a primary H2S flash (at a pressure of 3.5-3.8 MPa(G)) to obtain a primary H2S flash gas and a primary H2S flash liquid 19 (H2S molar content of 0.95-1.35%, CO2 molar content of 35-40%, temperature of -33 to -28°C); the above primary H2S flash liquid 19 is subjected to a secondary H2S flash (at a pressure of 1.6-2 MPa(G)) to obtain a secondary H2S flash gas and a secondary H2S flash liquid 31 (H2S molar content of 0.9-1.3%, CO2 molar content of 34.5-39.5%; temperature of -34 to -29°C);

[0143] The above first secondary CO2 flash liquid 29-i is subjected to a first flash (at a pressure of 0.05-0.08 MPa(G)) to obtain a semi-lean liquid methanol 13 (H2S molar content of 0.1-0.5 ppm; CO2 molar content of 14-18%, temperature of -62 to -58°C, pressure of 0.05-0.08 MPa(G)) and a first CO2 product gas; the above second secondary CO2 flash liquid 29-ii (cooled to -52 to -50°C) is subjected to a second flash (at a pressure of 0.06-0.09 MPa(G)) to obtain a flash liquid and a second CO2 product gas; the above secondary H2S flash liquid 31 is subjected to a third flash (at a pressure of 0.12-0.16 MPa(G)) to obtain a first H2S-rich methanol 20 (H2S molar content of 0.85-1.25%, CO2 molar content of 24-28%; temperature of -68 to -64°C; pressure of 0.13-0.17 MPa(G)) and a sulfur-containing gas phase; wherein the flash liquid and the sulfur-containing gas phase are contacted to obtain a low-sulfur methanol 21 (H2S molar content of 0.3-0.5%, CO2 molar content of 18-23%; temperature of -60 to -55°C, pressure of 0.12-0.16 MPa(G)) and a third CO2 product gas;

[0144] wherein the above first, second and third CO2 product gases are mixed to obtain a CO2 product gas 22 (H2S molar content of ≤1 ppm, CO2 molar content of 99.4-99.7%; temperature of -65 to -60°C, pressure of 0.05-0.08 MPa(G));

[0145] wherein the above semi-lean methanol 13 is divided into a first semi-lean methanol 13-i and a second semi-lean methanol 13-ii in a molar flow ratio of 1-2:1;

[0146] The above first semi-lean methanol 13-i (after heat exchange, -50 to -48°C) is contacted with nitrogen 26 and subjected to gas stripping to obtain tail gas 15 (molar content of H2S: 0.1-0.5 ppm, molar content of CO2: 80-85%; temperature: -60 to -50°C, pressure: 0.12-0.14 MPa (G)) and low-carbon methanol 17 (molar content of H2S: 0.1-0.5 ppm, molar content of CO2: 3-7%; temperature: -65 to -60°C);

[0147] wherein the above low-sulfur methanol 21 (after fourth pressurization to 3.8-4 MPa (G)) is subjected to primary washing with the primary CO2 flash gas to obtain primary washing liquid 27 (molar content of H2S: 0.3-0.6%, molar content of CO2: 18.5-23.5%; temperature: -60 to -55°C) and washed primary CO2 flash gas 23 (molar content of H2S: 0.04-0.06%, molar content of CO2: 6-10%, molar content of CO: 0.01-0.02%, molar content of H2: 90-93%; temperature: -65 to -55°C, pressure: 3.5-3.8 MPa (G)); and the above primary washing liquid 27 is subjected to secondary washing with the secondary CO2 flash gas to obtain low-sulfur carbon-rich methanol 32 (molar content of H2S: 0.3-0.6%, molar content of CO2: 19-24%; temperature: -60 to -55°C, pressure: 1.6-2 MPa (G)) and washed secondary CO2 flash gas 16 (molar content of H2S: 0.08-0.12%, molar content of CO2: 15-20%, molar content of CO: 0.1-0.3%, molar content of H2: 80-85%; temperature: -62 to -52°C, pressure: 1.6-2 MPa (G));

[0148] wherein the above second non-shift H2S-rich methanol 2-ii and the primary H2S flash gas are contacted and subjected to second washing to obtain washed primary H2S flash gas 18 (molar content of H2S: 0.4-0.6%, molar content of CO2: 7-12%, molar content of CO: 23-28%, molar content of H2: 62-66%) and to obtain second washing liquid mixed into the primary H2S flash liquid 19;

[0149] The third non-shift H2S-rich methanol 2-iii and the secondary H2S flash gas are contacted and subjected to a third washing to obtain washed secondary H2S flash gas 25 (the molar content of H2S is 0.8-1.2%, the molar content of CO2 is 14-18%, the molar content of CO is 34-38%, and the molar content of H2 is 43-48%; the temperature is -35 to -25°C, and the pressure is 1.6-2 MPa (G)) and secondary H2S-rich methanol 30 (the molar content of H2S is 1.2-1.6%, and the molar content of CO2 is 7-12%; the temperature is -25 to -20°C).

[0150] Comparative Example 1

[0151] Taking a hydrogen production device using a coal slurry gasification gasification device as an example, the effective gas (H2+CO) entering the low-temperature methanol washing device is 230000 Nm3 / 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. 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.

[0152] Table 1

[0153] Figure 1 Comparative Example 1 Example 1 Lean methanol recycle amount 13500 kmol / h 12000 kmol / h Low carbon / semi-lean liquid methanol recycle amount 7500 kmol / h [Use of CO2-rich methanol in H2S absorber] 5500 kmol / h 9500 kmol / h 7800 kmol / h External cold consumption 8500 KW / h [Pre-washing of methanol in H2S absorber tower] CO2-rich methanol 7700 KW / h Low sulfur rich carbon methanol Medium pressure flash tower flash and washing mode Classification flash, mixed washing Classification flash, classification washing Medium pressure flash tower flash stage One stage CO2 medium pressure flash wash methanol Two stages Flash gas sent down tower washing H2S medium pressure flash wash methanol H2S-rich methanol non-transformed h2s-rich methanol Low sulfur methanol Reabsorption tower Liquid phase complete mixing washing technology Liquid phase non-mixing washing technology

[0154] As can be seen from the results in Table 1, taking a hydrogen production device based on a coal slurry gasification gasification device as an example, the energy-saving multi-generation acid gas removal method provided by Example 1 for the supporting coal slurry gasification device, the lean methanol circulation amount is 88.9% of the lean methanol circulation amount in Comparative Example 1 (lean liquid-semi-lean liquid process), the low-carbon / semi-lean liquid methanol circulation amount is 73.3% of the low-carbon methanol circulation amount in Comparative Example 1 (lean liquid-semi-lean liquid process), the use amount of CO2-rich methanol in the H2S absorption tower is 82.1% of the use amount of CO2-rich methanol in Comparative Example 1 (lean liquid-semi-lean liquid process), and the cumulative external cold consumption is reduced by 800 KW / h, and the overall energy-saving effect is remarkable.

[0155] The above describes the preferred embodiments of the present application, 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. An energy-saving multi-generation acid gas removal method for a complete coal water slurry gasification plant, characterized in that, The method comprises: The non-shift gas (1) is subjected to three-stage purification to obtain pre-purified non-shift H2S-rich methanol (4), three streams of non-shift H2S-rich methanol (2), two streams of non-shift CO2-rich methanol (8) and purified non-shift gas (5); the synthesis gas (6) is subjected to 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) is subjected to three-stage CO2 absorption to obtain first-stage CO2-rich methanol (9), two streams of second-stage CO2-rich methanol (12), third-stage CO2-rich methanol (28) and purified gas (14); The first stream of second-stage CO2-rich methanol (12-i) is subjected to two-stage CO2 flashing to obtain first-stage CO2 flashing gas, second-stage CO2 flashing gas and two streams of second-stage CO2 flashing liquid (29); the second-stage H2S-rich methanol (10) is subjected to two-stage H2S flashing to obtain first-stage H2S flashing gas, second-stage H2S flashing gas and second-stage H2S flashing liquid (31); wherein the first stream of second-stage CO2 flashing liquid (29-i), the second stream of second-stage CO2 flashing liquid (29-ii) and the second-stage H2S flashing liquid (31) are subjected to first flashing, second flashing and third flashing respectively to obtain two streams of semi-lean liquid methanol (13), low-sulfur methanol (21), first H2S-rich methanol (20) and CO2 product gas (22); the low-carbon methanol (17) obtained by stripping the first stream of semi-lean liquid methanol (13-i) is returned to the three-stage CO2 absorption; Wherein the low-sulfur methanol (21), the first-stage CO2 flashing gas and the second-stage CO2 flashing gas are subjected to first washing to obtain low-sulfur carbon-rich methanol (32) which is returned to the two-stage H2S absorption; the second stream of non-shift H2S-rich methanol (2-ii) and the third stream of non-shift H2S-rich methanol (2-iii) are subjected to second washing and third washing with the first-stage H2S flashing gas and the second-stage H2S flashing gas respectively; Wherein the first stream of non-shift H2S-rich methanol (2-i) and the second stream of non-shift CO2-rich methanol (8-ii) are returned to the three-stage purification respectively; the first-stage CO2-rich methanol (9) is returned to the two-stage H2S absorption; the first stream of non-shift CO2-rich methanol (8-i), the second stream of second-stage CO2-rich methanol (12-ii) and the third-stage CO2-rich methanol (28) are returned to the three-stage CO2 absorption respectively.

2. The method of claim 1, wherein, The three-stage purification comprises first purification, second purification and third purification; wherein the first stream of non-shift H2S-rich methanol (2-i) is returned to the first purification; the second stream of non-shift CO2-rich methanol (8-ii) is returned to the second purification; Preferably, the non-shifted gas (1) and the first non-shifted H2S-rich methanol (2-i) are contacted and subjected to the first purification to obtain the pre-purified non-shifted H2S-rich methanol (4) and pre-desulfurized non-shifted gas; the pre-desulfurized non-shifted gas and the second non-shifted CO2-rich methanol (8-ii) are contacted and subjected to the second purification to obtain the non-shifted H2S-rich methanol (2) and desulfurized non-shifted gas; the desulfurized non-shifted gas and the first lean methanol (3-i) are contacted and subjected to the third purification to obtain the non-shifted CO2-rich methanol (8) and purified non-shifted gas (5); Preferably, the non-shifted H2S-rich methanol (2) has a molar content of H2S of 1.2-1.6% and a molar content of CO2 of 4-9%; the temperature is -30 to -26℃; and the pressure is 5.6-6 MPa (G); Preferably, the molar flow ratio of the first non-shifted H2S-rich methanol (2-i), the second non-shifted H2S-rich methanol (2-ii) and the third non-shifted H2S-rich methanol (2-iii) is 1:8-12:28-32; Preferably, the non-shifted CO2-rich methanol (8) has a molar content of H2S of 0.5-1 ppm and a molar content of CO2 of 5-9%; the temperature is -33 to -30℃; Preferably, the molar flow ratio of the first non-shifted CO2-rich methanol (8-i) and the second non-shifted CO2-rich methanol (8-ii) is 1:1-2; Preferably, the non-shifted CO2-rich methanol (8) has a molar content of H2S of 0.5-1 ppm and a molar content of CO2 of 5-9%; the temperature is -33 to -30℃; 3. The method of claim 1 or 2, wherein, The two-stage H2S absorption comprises a first H2S absorption and a second H2S absorption; wherein the primary CO2-rich methanol (9) is returned to the second H2S absorption; Preferably, the low-sulfur carbon-rich methanol (32) is divided into a first low-sulfur carbon-rich methanol (32-i) and a second low-sulfur carbon-rich methanol (32-ii) which are returned to the second H2S absorption and the first H2S absorption, respectively; Preferably, the synthesis gas (6) and the second low-sulfur carbon-rich methanol (32-ii) are contacted and subjected to the first H2S absorption to obtain the primary H2S-rich methanol (7) and pre-desulfurized gas; the pre-desulfurized gas, the first low-sulfur carbon-rich methanol (32-i) and the primary CO2-rich methanol (9) are contacted and subjected to the second H2S absorption to obtain the desulfurized gas (11) and the secondary H2S-rich methanol (10); Further preferably, the low-sulfur carbon-rich methanol (32) is first pressurized to 5.6-6 MPa (G) and divided into a first low-sulfur carbon-rich methanol (32-i) and a second low-sulfur carbon-rich methanol (32-ii) with a molar flow ratio of 26-30:1; Preferably, in the direction of material flow, the primary CO2-rich methanol (9) is sequentially subjected to the second pressurization to 5.6-6 MPa (G), the first cooling to -36 to -33℃ and the second H2S absorption. Preferably, the mole content of H2S in the secondary H2S-rich methanol (10) is 1-1.4%, the mole content of CO2 is 36-42%, the temperature is -10 to -6℃; Preferably, the mole content of H2S in the desulfurized gas (11) is 0.5-1ppm, the mole content of CO2 is 32-36%, the temperature is -22 to -18℃, and the pressure is 5.35-5.55MPa(G).

4. The method of any of claims 1-3, wherein, The third CO2 absorption includes a first CO2 absorption, a second CO2 absorption and a third CO2 absorption; the second secondary CO2-rich methanol (12-ii) returns to the first CO2 absorption, and the tertiary CO2-rich methanol (28) returns to the second CO2 absorption; the first non-shift CO2-rich methanol (8-i) and the low-carbon methanol (17) return to the third CO2 absorption; Preferably, the desulfurized gas (11) and the second secondary CO2-rich methanol (12-ii) are contacted and subjected to the first CO2 absorption to obtain the primary CO2-rich methanol (9) and a first pre-purified gas; the first pre-purified gas and the tertiary CO2-rich methanol (28) are contacted and subjected to the second CO2 absorption to obtain the secondary CO2-rich methanol (12) and a second pre-purified gas; the second pre-purified gas, the first non-shift CO2-rich methanol (8-i), the low-carbon methanol (17) and the second lean methanol (3-ii) are contacted and subjected to the third CO2 absorption to obtain the tertiary CO2-rich methanol (28) and a purified gas (14); Preferably, the mole content of H2S in the primary CO2-rich methanol (9) is 0.1-0.5ppm, the mole content of CO2 is 33-38%, the temperature is -15 to -10℃, and the pressure is 5.35-5.55MPa(G); Preferably, the mole content of H2S in the secondary CO2-rich methanol (12) is 0.1-0.5ppm, the mole content of CO2 is 23-28%, and the temperature is -15 to -10℃; Preferably, the mole flow ratio of the first secondary CO2-rich methanol (12-i) to the second secondary CO2-rich methanol (12-ii) is 2-3:1; Preferably, the first non-shift CO2-rich methanol (8-i) is cooled to -48 to -45℃ for the third CO2 absorption; Preferably, the tertiary CO2-rich methanol (28) is cooled to -36 to -33℃ for the second CO2 absorption; Preferably, the second secondary CO2-rich methanol (12-ii) is cooled to -30 to -28℃ for the first CO2 absorption; Preferably, the low-carbon methanol (17) is pressurized to 5.6-6MPa(G) for the third CO2 absorption.

5. The method of any of claims 1-4, wherein, The two-stage CO2 flashing process comprises: subjecting the first secondary CO2-rich methanol (12-i) to primary CO2 flashing to obtain primary CO2 flashing gas and primary CO2 flashing liquid (24); subjecting the primary CO2 flashing liquid (24) to secondary CO2 flashing to obtain the secondary CO2 flashing gas and secondary CO2 flashing liquid (29); Preferably, the pressure of the primary CO2 flashing is 3.5-3.8 MPa (G); the pressure of the secondary CO2 flashing is 1.6-2 MPa (G); Preferably, the first secondary CO2-rich methanol (12-i) is subjected to the fifth cooling to be -36 to -33 ℃ before the primary CO2 flashing; Preferably, the molar content of H2S in the secondary CO2 flashing liquid (29) is 0.1-0.5 ppm, the molar content of CO2 is 22-27%, and the temperature is -38.5 to -34.5 ℃; Preferably, the molar flow ratio of the first secondary CO2 flashing liquid (29-i) to the second secondary CO2 flashing liquid (29-ii) is 2-4:1; Preferably, the two-stage H2S flashing process comprises: subjecting the secondary H2S-rich methanol (10) to primary H2S flashing to obtain primary H2S flashing gas and primary H2S flashing liquid (19); subjecting the primary H2S flashing liquid (19) to secondary H2S flashing to obtain the secondary H2S flashing gas and secondary H2S flashing liquid (31); Preferably, the pressure of the primary H2S flashing is 3.5-3.8 MPa (G); the pressure of the secondary H2S flashing is 1.6-2 MPa (G); Preferably, the secondary H2S-rich methanol (10) is subjected to the sixth cooling to be -31 to -28 ℃ before the primary H2S flashing; Preferably, the molar content of H2S in the secondary H2S flashing liquid (31) is 0.9-1.3%, the molar content of CO2 is 34.5-39.5%, and the temperature is -34 to -29 ℃.

6. The method of any of claims 1-5, wherein, The first secondary CO2 flashing liquid (29-i) is subjected to the first flashing to obtain the semi-lean liquid methanol (13) and the first CO2 product gas; the second secondary CO2 flashing liquid (29-ii) is subjected to the second flashing to obtain a flashing liquid and the second CO2 product gas; and the secondary H2S flashing liquid (31) is subjected to the third flashing to obtain the first H2S-rich methanol (20) and a sulfur-containing gas phase; The flashing liquid and the sulfur-containing gas phase are contacted to obtain low-sulfur methanol (21) and the third CO2 product gas; and the first CO2 product gas, the second CO2 product gas and the third CO2 product gas are mixed to obtain CO2 product gas (22); Preferably, the second secondary CO2 flashing liquid (29-ii) is subjected to the seventh cooling to be -52 to -50 ℃ before the second flashing. Preferably, the semi-lean liquid methanol (13) has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 14-18%, a temperature of -62 to -58℃, and a pressure of 0.05-0.08 MPa (G); Preferably, the first semi-lean liquid methanol (13-i) and the second semi-lean liquid methanol (13-ii) have a molar flow ratio of 1-2:1; Preferably, the low-sulfur methanol (21) has a molar content of H2S of 0.3-0.5%, a molar content of CO2 of 18-23%, a temperature of -60 to -55℃, and a pressure of 0.12-0.16 MPa (G); Preferably, the CO2 product gas (22) has a molar content of H2S of ≤1 ppm, a molar content of CO2 of 99.4-99.7%, a temperature of -65 to -60℃, and a pressure of 0.05-0.08 MPa (G); Preferably, the first semi-lean liquid methanol (13-i) is contacted with nitrogen (26) and subjected to the gas stripping to obtain tail gas (15) and low-carbon methanol (17); Further preferably, the first semi-lean liquid methanol (13-i) is subjected to heat exchange to a temperature of -50 to -48℃ and then subjected to the gas stripping; Preferably, the low-carbon methanol (17) has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 3-7%, and a temperature of -65 to -60℃.

7. The method of any of claims 1-6, wherein, The first washing process comprises: washing the low-sulfur methanol (21) and the primary CO2 flash gas once to obtain a first washing liquid (27) and washed primary CO2 flash gas (23); and washing the first washing liquid (27) and the secondary CO2 flash gas twice to obtain the low-sulfur carbon-rich methanol (32) and washed secondary CO2 flash gas (16); Preferably, the low-sulfur methanol (21) is subjected to a fourth pressurization to a pressure of 3.8-4 MPa (G) and then subjected to the first washing; Preferably, the low-sulfur carbon-rich methanol (32) has a molar content of H2S of 0.3-0.6%, a molar content of CO2 of 19-24%, a temperature of -60 to -55℃, and a pressure of 1.6-2 MPa (G); Preferably, the second washing process comprises: contacting the second non-reformed H2S-rich methanol (2-ii) and the primary H2S flash gas and subjecting them to the second washing to obtain washed primary H2S flash gas (18) and a second washing liquid mixed into the primary H2S flash liquid (19); Preferably, the third washing process comprises: contacting the third non-reformed H2S-rich methanol (2-iii) and the secondary H2S flash gas and subjecting them to the third washing to obtain washed secondary H2S flash gas (25) and a second H2S-rich methanol (30).

8. An energy-saving multi-product acid gas removal device for a complete coal water slurry gasification plant, characterized in that, The device comprises: connected non-reformed gas purification tower (T-1), H2S absorption tower (T-2), CO2 absorption tower (T-3), primary medium-pressure flash tower (T-4), secondary medium-pressure flash tower (T-5), reabsorption tower (T-6), and low-carbon methanol gas stripping tower (T-7). The non-shift gas purification tower (T-1) is used for three-stage purification of non-shift gas (1) to obtain pre-purified non-shift H2S-rich methanol (4), three streams of non-shift H2S-rich methanol (2), two streams of non-shift CO2-rich methanol (8) and purified non-shift gas (5); the H2S absorption tower (T-2) is used for two-stage H2S absorption of synthesis gas (6) 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 for three-stage CO2 absorption of the desulfurized gas (11) to obtain first-stage CO2-rich methanol (9), two streams of second-stage CO2-rich methanol (12), third-stage CO2-rich methanol (28) and purified gas (14); The first medium-pressure flash tower (T-4) is divided into a first CO2 washing section, a first CO2 flashing section, a first H2S washing section and a first H2S flashing section from top to bottom; the second medium-pressure flash tower (T-5) is divided into a second CO2 washing section, a second CO2 flashing section, a second H2S washing section and a second H2S flashing section from top to bottom; wherein the first CO2 flashing section is connected to the second CO2 flashing section and is used for two-stage CO2 flashing of the first stream of second-stage CO2-rich methanol (12-i) to obtain first-stage CO2 flashing gas, second-stage CO2 flashing gas and two streams of second-stage CO2 flashing liquid (29); the first H2S flashing section is connected to the second H2S flashing section and is used for two-stage H2S flashing of the second-stage H2S-rich methanol (10) to obtain first-stage H2S flashing gas, second-stage H2S flashing gas and second-stage H2S flashing liquid (31); The reabsorption tower (T-6) is divided into a first flashing section, a second flashing section and a third flashing section from top to bottom and is used for first flashing, second flashing and third flashing of the first stream of second-stage CO2 flashing liquid (29-i), the second stream of second-stage CO2 flashing liquid (29-ii) and the second-stage H2S flashing liquid (31) respectively to obtain two streams of semi-lean liquid methanol (13), low-sulfur methanol (21), first H2S-rich methanol (20) and CO2 product gas (22); the low-carbon methanol stripping tower (T-7) is used for stripping of the first stream of semi-lean liquid methanol (13-i) to obtain low-carbon methanol (17) returned to the CO2 absorption tower (T-3); Wherein, the second flashing section is connected to the first CO2 washing section and the second CO2 washing section and is used for first washing of the low-sulfur methanol (21), the first-stage CO2 flashing gas and the second-stage CO2 flashing gas to obtain low-sulfur carbon-rich methanol (32) returned to the H2S absorption tower (T-2); the first H2S washing section is used for second washing of the second stream of non-shift H2S-rich methanol (2-ii) and the first-stage H2S flashing gas; and the second H2S washing section is used for third washing of the third stream of non-shift H2S-rich methanol (2-iii) and the second-stage H2S flashing gas. The first non-shift H2S-rich methanol (2-i) and the second non-shift CO2-rich methanol (8-ii) return to the non-shift gas purification tower (T-1); the first-stage CO2-rich methanol (9) returns to the H2S absorption tower (T-2); the first non-shift CO2-rich methanol (8-i), the second-stage CO2-rich methanol (12-ii) and the third-stage CO2-rich methanol (28) return to the CO2 absorption tower (T-3) respectively.

9. The apparatus of claim 8, wherein, The non-shift gas purification tower (T-1) is divided into a first purification section, a second purification section and a third purification section from bottom to top and communicated by a riser; the first non-shift H2S-rich methanol (2-i) returns to the first purification section; the second non-shift CO2-rich methanol (8-ii) returns to the second purification section; 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 and communicated by a riser; the second-stage low-sulfur carbon-rich methanol (32-ii) returns to the first H2S absorption section; the first-stage CO2-rich methanol (9) and the first-stage low-sulfur carbon-rich methanol (32-i) return to the second H2S absorption section respectively; 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 and communicated by a riser; the second-stage CO2-rich methanol (12-ii) returns to the first CO2 absorption section, and the third-stage CO2-rich methanol (28) returns to the second CO2 absorption section; the first non-shift CO2-rich methanol (8-i) and the low-carbon methanol (17) return to the third CO2 absorption section.

10. The apparatus of claim 9, wherein, A first pump (P-1) is arranged on a pipeline connecting the second CO2 washing section, the second H2S absorption section and the first H2S absorption section in the material flow direction, for dividing the low-sulfur carbon-rich methanol (32) into the first-stage low-sulfur carbon-rich methanol (32-i) and the second-stage low-sulfur carbon-rich methanol (32-ii) after first pressurization, and returning them to the second H2S absorption section and the first H2S absorption section respectively; Preferably, a second pump (P-2) and a first cooler (E-1) are arranged in sequence on a pipeline connecting the second H2S absorption section and the first CO2 absorption section in the material flow direction, for sequentially performing second pressurization and first cooling on the first-stage CO2-rich methanol (9) after second pressurization, and performing the second H2S absorption; Preferably, a second cooler (E-2) is arranged on a pipeline connecting the third purification section and the third CO2 absorption section, for performing the third CO2 absorption on the first non-shift CO2-rich methanol (8-i) after second cooling; Preferably, a third pump (P-3) is arranged on a pipeline connecting the low-carbon methanol stripping tower (T-7) and the third CO2 absorption section, for performing the third CO2 absorption on the low-carbon methanol (17) after third pressurization; Preferably, a second cooler (E-2) is arranged on a pipeline connecting the third purification section and the third CO2 absorption section, for performing the third CO2 absorption on the first non-shift CO2-rich methanol (8-i) after second cooling; Preferably, a third cooler (E-3) is arranged on the pipeline connecting the third CO2 absorption section and the second CO2 absorption section, for carrying out the second CO2 absorption after the third cooling of the third CO2-rich methanol (28) in the direction of material flow; Preferably, a fourth cooler (E-4) is arranged on the pipeline connecting the second CO2 absorption section and the first CO2 absorption section, for carrying out the first CO2 absorption after the fourth cooling of the second second CO2-rich methanol (12-ii) in the direction of material flow; Preferably, a fifth cooler (E-5) is arranged on the pipeline connecting the second CO2 absorption section and the first CO2 flashing section, for carrying out the first CO2 flashing after the fifth cooling of the first second CO2-rich methanol (12-i); Preferably, a sixth cooler (E-6) is arranged on the pipeline connecting the second H2S absorption section and the first H2S flashing section, for carrying out the first H2S flashing after the sixth cooling of the second H2S-rich methanol (10); Preferably, a seventh cooler (E-7) is arranged on the pipeline connecting the second CO2 flashing section and the second flashing section, for carrying out the second flashing after the seventh cooling of the second second CO2 flashing liquid (29-ii); Preferably, a heat exchanger (Q) is arranged on the pipeline connecting the first flashing section and the low-carbon methanol stripping tower (T-7), for carrying out the stripping after the heat exchange of the first half-lean liquid methanol (13-i).

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