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 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. According to the method, the H2S absorption process is optimally set, and non-conversion CO2-rich methanol, non-conversion H2S-rich methanol, low H2S methanol and first-stage CO2-rich methanol are used for treating the synthesis gas, so that the use amount of the first-stage CO2-rich methanol is reduced; by optimizing and setting a medium-pressure flash evaporation process, CO2 flash steam and H2S flash steam are washed with low-sulfur methanol to obtain low-H2S methanol, so that the utilization rate of the low-H2S methanol is increased; the reabsorption process is optimized, low-sulfur methanol is generated, meanwhile, the low-sulfur methanol is prevented from being deeply polluted, and the low-temperature methanol washing device has the advantage of being low in 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 the 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. CO2 and H2S in the acid gas are generally poisons of the synthesis catalyst, so they must be removed before the synthesis process.

[0003] 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 heat regeneration, which is the main source of energy consumption of the low-temperature methanol washing. Strengthening the use efficiency of the H2S-containing methanol is a key factor of technological innovation. In addition, the non-shift CO2-rich methanol solution does not contain H2S gas and has a low CO2 content, and the non-shift H2S-rich methanol has a low CO2 content and a relatively high CO gas content. Therefore, it is very important to reasonably use the two kinds of rich methanol again.

[0004] CN201110260570.0 discloses a low-temperature methanol washing process. First, the low-temperature methanol washing process uses CO2-rich methanol to wash the synthesis gas in the H2S absorption tower. The CO2-rich methanol is contaminated while absorbing H2S gas, which increases the generation amount of H2S-rich methanol and increases energy consumption. Second, in the CO2 flash evaporation section of the reabsorption tower, the CO2-rich methanol directly mixes with the H2S-rich methanol while washing the H2S-rich methanol flash gas, which contaminates the CO2-rich methanol itself and the low-concentration H2S methanol produced is not fully used, resulting in high energy consumption. Third, the CO2 and H2S gas flashed from the medium-pressure flash tower is washed and absorbed by the H2S-rich methanol from the bottom of the reabsorption tower, and the H2S-rich methanol after flashing is mixed, which reduces the CO2 gas concentration in the H2S-rich methanol from the medium-pressure flash tower to the reabsorption tower, which is not conducive to the desorption of low-temperature in the reabsorption tower.

[0005] CN201810994082.4 discloses a low-temperature methanol washing system and a method for providing synthesis gas. The technology uses the non-shift H2S-rich methanol after washing the non-shift gas for secondary use, but only uses the H2S-rich methanol after medium-pressure flashing to wash the methanol, which is not efficient enough, and there is still room for improvement and energy consumption reduction. SUMMARY

[0006] The present application aims to overcome the problems of low use efficiency of non-shift H2S-rich methanol and non-shift CO2-rich methanol, high energy consumption, and unreasonable medium-pressure flash tower process setting of the existing poly-generation low-temperature methanol washing technology, and provides a poly-generation acid gas removal method matched with a coal slurry gasification device and a poly-generation acid gas removal device matched with a coal slurry gasification device.

[0007] To achieve the above-mentioned purpose, the present application provides a poly-generation acid gas removal method matched with a coal slurry gasification device, which comprises the following steps:

[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 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, two groups of secondary CO2-rich methanol, tertiary CO2-rich methanol, and purified gas; wherein the first group of non-shift H2S-rich methanol, the first group of non-shift CO2-rich methanol, and the primary CO2-rich methanol are returned to the two-stage H2S absorption respectively; the second 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 group of secondary CO2-rich methanol and the tertiary CO2-rich methanol are returned to the three-stage CO2 absorption respectively;

[0009] The second group of secondary CO2-rich methanol and the secondary H2S-rich methanol are subjected to CO2 flashing and H2S flashing respectively to obtain two groups of CO2 flashing liquids, H2S flashing liquid, CO2 flashing gas, and H2S flashing gas; wherein the first group of CO2 flashing liquid, the second group of CO2 flashing liquid, and the H2S flashing liquid are subjected to first flashing, second flashing, and third flashing respectively to obtain two groups of semi-lean liquid methanol, two groups of low-sulfur methanol, and first H2S-rich methanol; wherein the first group of semi-lean liquid methanol is returned to the three-stage CO2 absorption; the first group of low-sulfur methanol, the CO2 flashing gas, and the H2S flashing gas are subjected to first washing to obtain low H2S methanol which is returned to the two-stage H2S absorption; the fourth flashing liquid obtained by fourth flashing of the third group of non-shift H2S-rich methanol is subjected to second washing with the first washing gas.

[0010] 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-shift gas purification tower, H2S absorption tower, CO2 absorption tower, medium pressure flash tower and resorption tower;

[0011] 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-stage H2S-rich methanol, second-stage H2S-rich methanol and desulfurized gas; and the CO2 absorption tower is used for absorbing CO2 in three stages to obtain first-stage CO2-rich methanol, two streams of second-stage CO2-rich methanol, third-stage CO2-rich methanol and purified gas.

[0012] Among them, the first stream of non-shift H2S-rich methanol, the first stream of non-shift CO2-rich methanol and the first-stage CO2-rich methanol are returned to the H2S absorption tower respectively; the second stream of non-shift H2S-rich methanol and the second stream of non-shift CO2-rich methanol are returned to the non-shift gas purification tower respectively; the first stream of second-stage CO2-rich methanol and the third-stage CO2-rich methanol are returned to the CO2 absorption tower respectively.

[0013] The medium pressure flash tower is divided into CO2 flash section, second washing section, first washing section and H2S flash section from top to bottom, the CO2 flash section is used for CO2 flashing of the second stream of second-stage CO2-rich methanol to obtain CO2 flash gas sent to the H2S flash section through a pipeline and two streams of CO2 flash liquid; the H2S flash section is used for H2S flashing of the second-stage H2S-rich methanol to obtain H2S flash gas and H2S flash liquid.

[0014] The resorption tower is divided into first flash section, second flash section and third flash section from top to bottom, which are used for first flashing, second flashing and third flashing of the first stream of CO2 flash liquid, the second stream of CO2 flash liquid and the H2S flash liquid respectively to obtain two streams of semi-lean liquid methanol, two streams of low-sulfur methanol and first H2S-rich methanol.

[0015] Among them, the first stream of semi-lean liquid methanol is returned to the CO2 absorption tower; the first washing section is used for first washing of the first stream of low-sulfur methanol, CO2 flash gas and H2S flash gas to obtain low-H2S methanol returned to the H2S absorption tower and first washing gas sent to the second washing section through a riser and second washed with fourth flash liquid obtained by fourth flashing of the third stream of non-shift H2S-rich methanol.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] (1) The method provided by the present application divides the non-shift H2S-rich methanol into three streams, wherein the first stream of non-shift H2S-rich methanol and the second stream of non-shift H2S-rich methanol are used as washing solvents to treat the synthesis gas and the non-shift gas respectively, compared with the prior art which uses CO2-rich methanol for pre-washing, the present application reduces the use amount of the first-stage CO2-rich methanol under the premise of obtaining the same washing effect, which has a positive significance for reducing the energy consumption of the low-temperature methanol washing device; the third stream of non-shift H2S-rich methanol is further used for washing the CO2 flash gas and the H2S flash gas during its own flashing, avoiding the recycling use of the second H2S-rich methanol;

[0018] (2) The method provided by the present application realizes the absorption of the sulfur-containing gas phase generated by the third flashing of the H2S flash liquid through the second flashing of the second stream of CO2 flash liquid, but the second stream of CO2 flash liquid is not mixed with the first H2S-rich methanol after the third flashing;

[0019] (3) The method provided by the present application optimizes the H2S absorption process by introducing low H2S methanol, non-shift H2S-rich methanol, non-shift CO2-rich methanol and first-stage CO2-rich methanol to jointly absorb H2S and CO2 gas in the synthesis gas, which not only realizes the full use of the low H2S methanol, the non-shift H2S-rich methanol and the non-shift CO2-rich methanol, but also reduces the use amount of the first-stage CO2-rich methanol, which is equivalent to reducing the second H2S-rich methanol which needs to be heat regenerated. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The present application provides a structure schematic diagram of a multi-production acid gas removal device matched with a coal water slurry gasification device.

[0021] REFERENCE SIGNS

[0022] T-1, non-shift gas purification tower; T-2, H2S absorption tower; T-3, CO2 absorption tower; T-4, medium-pressure flash tower; T-5, reabsorption tower;

[0023] E-1, first cooler; E-2, second cooler; E-3, third cooler; E-4, fourth cooler; E-5, fifth cooler; E-6, sixth cooler; P-1, first pump; P-2, second pump; P-3, third pump;

[0024] 1. non-shifted gas; 2. lean methanol; 2-i, first lean methanol stream; 2-ii, second lean methanol stream; 3. non-shifted rich H2S methanol; 3-i, first non-shifted rich H2S methanol stream; 3-ii, second non-shifted rich H2S methanol stream; 3-iii, third non-shifted rich H2S methanol stream; 4. pre-purified non-shifted rich H2S methanol; 5. purified non-shifted gas; 6. synthesis gas; 7. primary rich H2S methanol; 8. semi-lean liquid methanol; 8-i, first semi-lean liquid methanol stream; 8-ii, second semi-lean liquid methanol stream; 9. primary rich CO2methanol; 10. sweetened gas; 11. secondary rich H2S methanol; 12. secondary rich CO2methanol; 12-i, first secondary rich CO2methanol stream; 12-ii, second secondary rich CO2methanol stream; 13. tertiary rich CO2methanol; 14. non-shifted rich CO2methanol; 14-i, first non-shifted rich CO2methanol stream; 14-ii, second non-shifted rich CO2methanol stream; 15. CO2flash liquid; 15-i, first CO2flash liquid stream; 15-ii, second CO2flash liquid stream; 16. CO2flash gas; 17. second rich H2S methanol; 18. post-wash flash gas; 19. H2S flash liquid; 20. low-sulfur methanol; 20-i, first low-sulfur methanol stream; 20-ii, second low-sulfur methanol stream; 21. low-H2S methanol; 22. CO2product gas; 23. first rich H2S methanol; 24. purified gas. DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges and values are approximations that are already sufficiently accurate for practical purposes. It is not actually to be expected that the endpoints of the ranges and values will be literally exact, and thus, the endpoints of the ranges and values are included in the range where appropriate. It must be noted that as used herein and in the appended claims, the singular includes the plural unless specifically stated otherwise. As used herein and in the appended claims, the term "or" as used in the context of "A or B" is a true disjunction, unless otherwise stated. As used herein and in the appended claims, the term "comprises" and its grammatical variants, such as "comprising," "comprised of," and "comprises of," mean "including but not limited to."

[0026] In the present invention, "first," "second," "third," "fourth," "fifth," and "sixth" do not indicate any order or limitation on the various materials or steps, but are used only to distinguish or identify the steps or materials, unless otherwise specifically stated.

[0027] In the present invention, "top" of a vessel refers to the top 0-10% of the vessel from top to bottom; "upper" of a vessel refers to the top 10-40% of the vessel from top to bottom; "middle" of a vessel refers to the top 40-60% of the vessel from top to bottom; "lower" of a vessel refers to the top 60-90% of the vessel from top to bottom; and "bottom" of a vessel refers to the top 90-100% of the vessel from top to bottom, unless otherwise specifically stated.

[0028] The application provides a multi-production acid gas removal method for a water-coal slurry gasification device.

[0029] The non-shifted gas is subjected to three-stage purification to obtain pre-purified non-shifted H2S-rich methanol, three non-shifted H2S-rich methanol streams, two non-shifted CO2-rich methanol streams and purified non-shifted 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 second-stage CO2-rich methanol streams, third-stage CO2-rich methanol and purified gas; wherein the first non-shifted H2S-rich methanol stream, the first non-shifted CO2-rich methanol stream and the first-stage CO2-rich methanol are returned to the two-stage H2S absorption; the second non-shifted H2S-rich methanol stream and the second non-shifted CO2-rich methanol stream are returned to the three-stage purification; the first second-stage CO2-rich methanol stream and the third-stage CO2-rich methanol are returned to the three-stage CO2 absorption;

[0030] The second second-stage CO2-rich methanol stream and the second-stage H2S-rich methanol are subjected to CO2 flashing and H2S flashing respectively to obtain two CO2 flashing liquid streams, H2S flashing liquid, CO2 flashing gas and H2S flashing gas; wherein the first CO2 flashing liquid stream, the second CO2 flashing liquid stream and the H2S flashing liquid are subjected to first flashing, second flashing and third flashing respectively to obtain two semi-lean liquid methanol streams, two low-sulfur methanol streams and first H2S-rich methanol; wherein the first semi-lean liquid methanol stream is returned to the three-stage CO2 absorption; the first low-sulfur methanol stream, the CO2 flashing gas and the H2S flashing gas are subjected to first washing to obtain low-H2S methanol which is returned to the two-stage H2S absorption; the fourth flashing liquid obtained by fourth flashing of the third non-shifted H2S-rich methanol is subjected to second washing with the first washing gas.

[0031] In the application, the synthesis gas and the non-shifted gas are both derived from the water-coal slurry gasification device, wherein the synthesis gas is prepared from the non-shifted gas through a shift process.

[0032] In the 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 5.4-5.6 MPa(G); the molar content of H2S in the non-shifted gas 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).

[0033] In some embodiments of the application, preferably, the three-stage purification comprises first purification, second purification and third purification; wherein the second non-shifted H2S-rich methanol stream is returned to the first purification; the second non-shifted CO2-rich methanol stream is returned to the second purification.

[0034] 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-shift gas; the second purification aims to further remove H2S in the non-shift gas; and the third purification aims to further remove CO2 in the non-shift gas.

[0035] In some embodiments of the present application, further preferably, the non-shift gas and the second non-shift H2S-rich methanol are contacted and subjected to the first purification to obtain the pre-purified non-shift H2S-rich methanol and pre-desulfurized non-shift gas; the pre-desulfurized non-shift gas and the second non-shift CO2-rich methanol are contacted and subjected to the second purification to obtain the non-shift H2S-rich methanol and desulfurized non-shift gas; and the desulfurized non-shift gas and the first methanol-lean gas are contacted and subjected to the third purification to obtain the non-shift CO2-rich methanol and purified non-shift gas.

[0036] In the present application, preferably, the molar flow ratio of the non-shift gas and the second non-shift H2S-rich methanol is 50-60:1; and the molar content of H2S in the pre-purified non-shift H2S-rich methanol is 2.1-2.6%, and the molar content of CO2 is 3-7%.

[0037] In the present application, preferably, the molar flow ratio of the second non-shift CO2-rich methanol and the non-shift gas is 1:1-2.

[0038] In some embodiments of the present application, preferably, the molar content of H2S in the non-shift H2S-rich methanol is 1.2-1.6%, and the molar content of CO2 is 4-9%; the temperature is -30 to -26℃; and the pressure is 5.5-6 MPa(G).

[0039] In the present application, the non-shift H2S-rich methanol is divided into three streams, the first stream is subjected to the first H2S absorption, the second stream is subjected to the first purification, and the third stream is subjected to the fourth flash and the second washing. Further preferably, the molar flow ratio of the first non-shift H2S-rich methanol, the second non-shift H2S-rich methanol and the third non-shift H2S-rich methanol is 5-7:1:32-35.

[0040] In the present application, preferably, the molar flow ratio of the first methanol-lean gas and the non-shift gas is 1-2.5:1-2.

[0041] In some embodiments of the present application, preferably, the molar content of H2S in the non-shift CO2-rich methanol is 0.5-1 ppm, and the molar content of CO2 is 5-8%; the temperature is -40 to -33℃.

[0042] In the present application, the non-shift rich CO2 methanol is divided into two streams, the first stream is subjected to the second H2S absorption, and the second stream is subjected to the second purification. Further preferably, the molar flow ratio of the first stream of non-shift rich CO2 methanol and the second stream of non-shift rich CO2 methanol is 1:1-2.

[0043] In some embodiments of the present application, preferably, the molar content of H2S in the purified non-shift gas is ≤0.1 ppm, the molar content of CO2 is ≤20 ppm; the temperature is -55 to -45℃, and the pressure is 5.4-6 MPa (G).

[0044] In some embodiments of the present application, preferably, the two-stage H2S absorption comprises a first H2S absorption and a second H2S absorption; wherein the first stream of non-shift rich H2S methanol is returned to the first H2S absorption; the first stream of non-shift rich CO2 methanol, the first-stage rich CO2 methanol, and the low H2S methanol are returned to the second H2S absorption, respectively.

[0045] In the present application, the first H2S absorption aims to remove impurities such as HCN, NH3, and a small amount of H2S and CO2 in the synthesis gas; and the second H2S absorption aims to further remove H2S and CO2 in the synthesis gas.

[0046] In some embodiments of the present application, further preferably, the synthesis gas and the first stream of non-shift rich H2S methanol are contacted and subjected to the first H2S absorption to obtain the first-stage rich H2S methanol and pre-desulfurized gas; the pre-desulfurized gas, the low H2S methanol, the first-stage rich CO2 methanol, and the first stream of non-shift rich CO2 methanol are contacted and subjected to the second H2S absorption to obtain the desulfurized gas and the second-stage rich H2S methanol.

[0047] In the present application, preferably, the molar flow ratio of the synthesis gas and the first stream of non-shift rich H2S methanol is 60-70:1; further preferably, the molar content of H2S in the first-stage rich H2S methanol is 2.4-2.9%, and the molar content of CO2 is 66-71%, which is sent to subsequent processes.

[0048] In the present application, preferably, the molar flow ratio of the low H2S methanol and the synthesis gas is 1-3:13-17; the molar flow ratio of the first-stage rich CO2 methanol and the synthesis gas is 5-6:13-17; and the molar flow ratio of the first stream of non-shift rich CO2 methanol and the synthesis gas is 1:13-17.

[0049] In some embodiments of the present application, preferably, the molar content of H2S in the lean methanol is 0%, and the molar content of CO2 is 0%. In the present application, the lean methanol is selected from subsequent processes. In the present application, without special circumstances, the lean methanol is divided into a first lean methanol and a second lean methanol; the present application does not limit the molar flow ratio of the first lean methanol and the second lean methanol.

[0050] In some embodiments of the present application, preferably, the molar content of H2S in the secondary H2S-rich methanol is 1.3-1.7%, and the molar content of CO2 is 36-42%; the temperature is -10 to -5℃.

[0051] 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 34-40%; the temperature is -15 to -5℃; and the pressure is 5.35-5.55 MPa (G).

[0052] In some embodiments of the present application, preferably, the low-H2S methanol is pressurized to 5.6-6 MPa (G) to perform the second H2S absorption.

[0053] In some embodiments of the present application, preferably, the third CO2 absorption includes a first CO2 absorption, a second CO2 absorption, and a third CO2 absorption; the first secondary CO2-rich methanol returns to the first CO2 absorption, and the tertiary CO2-rich methanol returns to the second CO2 absorption; and the first semi-lean liquid methanol returns to the third CO2 absorption.

[0054] In some embodiments of the present application, further preferably, the desulfurized gas and the first secondary CO2-rich methanol are contacted and subjected to the first CO2 absorption to obtain the primary CO2-rich methanol and a first pre-purified gas; the first pre-purified gas and the tertiary CO2-rich methanol are contacted and subjected to the second CO2 absorption to obtain the secondary CO2-rich methanol and a second pre-purified gas; and the second pre-purified gas, the first semi-lean liquid methanol, and the second lean methanol are contacted and subjected to the third CO2 absorption to obtain the tertiary CO2-rich methanol and a purified gas.

[0055] In the present application, preferably, the molar flow ratio of the desulfurized gas and the first secondary CO2-rich methanol is 1:1.2-1.5; the molar flow ratio of the purified gas and the first semi-lean liquid methanol is 1-3:1; and the molar flow ratio of the purified gas and the second lean methanol is 1:1-1.3.

[0056] In some embodiments of the present invention, preferably, the molar content of H2S in the primary CO2-rich methanol is 0.1-0.5 ppm, the molar content of CO2 is 33-37%, the temperature is -12 to -5°C, and the pressure is 5.3-5.4 MPa(G).

[0057] In some embodiments of the present invention, preferably, the molar content of H2S in the secondary CO2-rich methanol is 0.1-0.5 ppm, the molar content of CO2 is 27-32%, the temperature is -10 to -5°C, and the pressure is 5.3-5.4 MPa(G).

[0058] In this invention, the secondary CO2-rich methanol is divided into two streams, which are subjected to a first flash evaporation and a second flash evaporation, respectively. More preferably, the molar flow ratio of the first and second streams of secondary CO2-rich methanol is 1:2-3.

[0059] In some embodiments of the present invention, more preferably, the secondary CO2-rich methanol is cooled to -20 to -18°C and divided into a first stream of secondary CO2-rich methanol and a second stream of secondary CO2-rich methanol.

[0060] In some embodiments of the present invention, preferably, the third-stage CO2-rich methanol is cooled to -36 to -33°C in the direction of material flow for the second CO2 absorption.

[0061] In some embodiments of the present invention, preferably, the first semi-lean methanol stream is pressurized to 5.6-6 MPa(G) according to the material flow direction for the third CO2 absorption.

[0062] In some embodiments of the present invention, preferably, the first-stage CO2-rich methanol is cooled to -36 to -33°C in the direction of material flow for the second H2S absorption.

[0063] 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 5.25-5.45MPa(G).

[0064] In this invention, the second secondary CO2-rich methanol is subjected to CO2 flash evaporation to obtain CO2 flash vapor and CO2 flash liquid; the secondary H2S-rich methanol is subjected to H2S flash evaporation to obtain H2S flash vapor and H2S flash liquid.

[0065] In some embodiments of the present invention, preferably, the second secondary CO2-rich methanol stream is cooled to -36 to -33°C in a fourth cooling process to perform CO2 flash evaporation.

[0066] In some embodiments of the present application, preferably, the secondary H2S-rich methanol is further cooled to -36 to -33℃ by a fifth cooling, and the H2S is flashed.

[0067] In some embodiments of the present application, preferably, the CO2 flashing and H2S flashing are performed at a pressure of 1.6-2 MPa (G) respectively.

[0068] In some embodiments of the present application, preferably, the H2S in the CO2 flashing liquid has a molar content of 0.1-0.5 ppm, the CO2 has a molar content of 26.5-31.5%, and the temperature is -36.5 to -33.5℃.

[0069] In some embodiments of the present application, preferably, the first and second CO2 flashing liquids have a molar flow ratio of 2-4:1.

[0070] In some embodiments of the present application, preferably, the H2S in the H2S flashing liquid has a molar content of 1.2-1.6%, the CO2 has a molar content of 35.5-41.5%, and the temperature is -36.5 to -33.5℃.

[0071] In some embodiments of the present application, preferably, the first CO2 flashing liquid is subjected to the first flashing to obtain the semi-lean liquid methanol and a first CO2 product gas; the second CO2 flashing liquid is subjected to the second flashing to obtain a second flashing liquid and a second 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 second flashing liquid and the sulfur-containing gas phase are contacted and subjected to a third washing to obtain low-sulfur methanol and a third CO2 product gas; and wherein the first, second and third CO2 product gases are mixed to obtain a CO2 product gas.

[0072] In the present application, the first flashing is performed at a pressure < the second flashing < the third flashing. Preferably, the first flashing is performed at a pressure of 0.05-0.08 MPa (G), the second flashing is performed at a pressure of 0.06-0.09 MPa (G), and the third flashing is performed at a pressure of 0.12-0.16 MPa (G).

[0073] In some embodiments of the present application, preferably, the semi-lean liquid methanol has a molar content of H2S ≤0.5 ppm, a molar content of CO2 of 28-32%, a temperature of -64 to -60℃, and a pressure of 0.05-0.08 MPa (G).

[0074] In the present application, the semi-lean methanol is divided into two streams, the first stream is subjected to a third CO2 absorption, and the second stream is sent to a subsequent process. Further preferably, the molar flow ratio of the first stream of semi-lean methanol and the second stream of semi-lean methanol is 1:1-1.5.

[0075] In some embodiments of the present application, preferably, the molar content of H2S in the low-sulfur methanol is 0.4-0.8%, the molar content of CO2 is 22-26%; the temperature is -64 to -60℃, and the pressure is 0.12-0.16 MPa(G).

[0076] In the present application, the low-sulfur methanol is divided into two streams, the first stream is returned to the first washing, and the second stream is sent to a subsequent process. Preferably, the molar flow ratio of the first stream of low-sulfur methanol and the second stream of low-sulfur methanol is 1-3:1.

[0077] In some embodiments of the present application, further preferably, the low-sulfur methanol is subjected to a third pressurization to 2-2.4 MPa(G) in the direction of material flow, and is divided into the first stream of low-sulfur methanol and the second stream of low-sulfur methanol.

[0078] 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).

[0079] In some embodiments of the present application, preferably, the molar content of H2S in the first H2S-rich methanol is 1.3-1.7%, the molar content of CO2 is 27-32%; the temperature is -70 to -64℃, and the pressure is 0.13-0.17 MPa(G), which is sent to a subsequent process for treatment.

[0080] In some embodiments of the present application, preferably, the first stream of low-sulfur methanol, the CO2 flash gas, and the H2S flash gas are contacted and subjected to the first washing to obtain the low-H2S methanol and the first washing gas.

[0081] In some embodiments of the present application, preferably, the molar content of H2S in the low-H2S methanol is 0.4-0.7%, the molar content of CO2 is 24-28%; and the temperature is -62 to -54℃.

[0082] In some embodiments of the present application, preferably, the pressure of the fourth flash is 1.6-2 MPa(G); further preferably, the fourth flash liquid and the first washing gas are contacted and subjected to the second washing to obtain the post-washing flash gas and the second H2S-rich methanol.

[0083] In the present invention, preferably, the molar content of H2 in the flashed vapor after washing is 59 - 63%, the molar content of CO is 19 - 23%, and the molar content of CO2 is 14 - 18%; the temperature is -35 to -25 °C, and the pressure is 1.8 - 2 MPa(G).

[0084] In the present invention, preferably, the molar content of H2S in the second H2S-rich methanol is 1.1 - 1.5%, and the molar content of CO2 is 4 - 8%; the temperature is -33 to -28 °C, and it is sent to the subsequent process for treatment.

[0085] The second aspect of the present invention provides a structural schematic diagram of a poly-generation acid gas removal device for a supporting water coal gasification device as Figure 1 shown, from Figure 1 it can be seen that the device includes: a connected non-shifted gas purification tower T-1, H2S absorption tower T-2, CO2 absorption tower T-3, medium-pressure flash tower T-4, and re-absorption tower T-5;

[0086] The non-shifted gas purification tower T-1 is used to perform three-stage purification on the non-shifted gas 1 to obtain pre-purified non-shifted H2S-rich methanol 4, non-shifted H2S-rich methanol 3 in three streams, non-shifted CO2-rich methanol 14 in two streams, and purified non-shifted gas 5; the H2S absorption tower T-2 is used to perform two-stage H2S absorption on the syngas 6 to obtain first-stage H2S-rich methanol 7, second-stage H2S-rich methanol 11, and desulfurized gas 10; the CO2 absorption tower T-3 is used to perform three-stage CO2 absorption on the desulfurized gas 10 to obtain first-stage CO2-rich methanol 9, second-stage CO2-rich methanol 12 in two streams, third-stage CO2-rich methanol 13, and purified gas 24;

[0087] Among them, the first stream of non-shifted H2S-rich methanol 3-i, the first stream of non-shifted CO2-rich methanol 14-i, and the first-stage CO2-rich methanol 9 are respectively returned to the H2S absorption tower T-2; the second stream of non-shifted H2S-rich methanol 3-ii and the second stream of non-shifted CO2-rich methanol 14-ii are respectively returned to the non-shifted gas purification tower T-1; the first stream of second-stage CO2-rich methanol 12-i and the third-stage CO2-rich methanol 13 are respectively returned to the CO2 absorption tower T-3;

[0088] The medium-pressure flash tower T-4 is divided into a CO2 flash section, a second washing section, a first washing section, and an H2S flash section from top to bottom. The CO2 flash section is used to perform CO2 flash on the second stream of second-stage CO2-rich methanol 12-ii, and the obtained CO2 flashed vapor 16 is sent to the H2S flash section through a pipeline, and the obtained CO2 flash liquid 15 is in two streams; the H2S flash section is used to perform H2S flash on the second-stage H2S-rich methanol 11, and the obtained H2S flashed vapor and the CO2 flashed vapor 16 are respectively sent to the first washing section through lifting holes, and the H2S flash liquid 19 is obtained;

[0089] The reabsorption tower T-5 is divided into a first flash section, a second flash section and a third flash section from top to bottom, respectively used for first flashing, second flashing and third flashing of the first CO2 flash liquid 15-i, the second CO2 flash liquid 15-ii and the H2S flash liquid 19 to obtain two streams of semi-lean liquid methanol 8, two streams of low-sulfur methanol 20 and first H2S-rich methanol 23.

[0090] The first stream of semi-lean liquid methanol 8-i returns to the CO2 absorption tower T-3; the first washing section is used for first washing of the first stream of low-sulfur methanol 20-i, CO2 flash gas 16 and H2S flash gas to obtain low-H2S methanol 21 which returns to the H2S absorption tower T-2, and first washing gas which is sent to the second washing section through a riser hole and second washed with fourth flash liquid obtained by fourth flashing of the third stream of non-shift H2S-rich methanol 3-iii.

[0091] In the present application, as shown in Figure 1 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 through riser holes; wherein the second stream of non-shift H2S-rich methanol 3-ii returns to the first purification section; and the second stream of non-shift CO2-rich methanol 14-ii returns to the second purification section.

[0092] 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 second stream of non-shift H2S-rich methanol 3-ii 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 stream of non-shift CO2-rich methanol 14-ii and performing second purification to obtain the non-shift H2S-rich methanol 3 and desulfurized non-shift gas; and the third purification section is used for contacting the desulfurized non-shift gas and the first stream of lean methanol 2-i and performing third purification to obtain the non-shift CO2-rich methanol 14 and purified non-shift gas 5.

[0093] In the present application, as shown in Figure 1 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 through riser holes; wherein the first stream of non-shift H2S-rich methanol 3-i returns to the first H2S absorption section; and the first stream of non-shift CO2-rich methanol 14-i, the first-stage CO2-rich methanol 9 and the low-H2S methanol 21 return to the second H2S absorption section, respectively.

[0094] In the present application, as shown in Figure 1As shown, in the H2S absorption tower T-2, a first H2S absorption section is used for contacting the synthesis gas 6 and the first non-shift H2S-rich methanol 3-i and performing first H2S absorption to obtain the primary H2S-rich methanol 7 and pre-desulfurized gas; a second H2S absorption section is used for contacting the pre-desulfurized gas, the first non-shift CO2-rich methanol 14-i, the primary CO2-rich methanol 9 and the low-H2S methanol 21 and performing second H2S absorption to obtain the desulfurized gas 10 and the secondary H2S-rich methanol 11.

[0095] In the present application, as shown in Figure 1 As shown, 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 connected by a gas lift hole; wherein the first secondary CO2-rich methanol 12-i returns to the first CO2 absorption section, the tertiary CO2-rich methanol 13 returns to the second CO2 absorption section, and the first semi-lean liquid methanol 8-i returns to the third CO2 absorption section.

[0096] In the present application, as shown in Figure 1 As shown, in the CO2 absorption tower T-3, a first CO2 absorption section is used for contacting the desulfurized gas 10 and the first secondary CO2-rich methanol 12-i and performing first CO2 absorption to obtain the primary CO2-rich methanol 9 and the first pre-purified gas; a second CO2 absorption section is used for contacting the pre-purified gas and the tertiary CO2-rich methanol 13 and performing second CO2 absorption to obtain the secondary CO2-rich methanol 12 and the second pre-purified gas; a third CO2 absorption section is used for contacting the second pre-purified gas, the first semi-lean liquid methanol 8-i and the second lean methanol 2-ii and performing third CO2 absorption to obtain the tertiary CO2-rich methanol 13 and the purified gas 24.

[0097] In the present application, as shown in Figure 1 As shown, the medium-pressure flash tower T-4 is divided into a CO2 flash section, a second washing section, a first washing section and an H2S flash section from top to bottom, wherein the CO2 flash section is used for CO2 flashing of the second secondary CO2-rich methanol 12-ii to obtain CO2 flash gas 16 and CO2 flash liquid 15; the H2S flash section is used for H2S flashing of the secondary H2S-rich methanol 11 to obtain H2S flash gas and H2S flash liquid 19; the first washing section is used for first washing of the first low-sulfur methanol 20-i, the CO2 flash gas 16 and the H2S flash gas to obtain first washing gas and low-H2S methanol 21; the second washing section is used for second washing of the fourth flash liquid obtained by fourth flashing of the third non-shift H2S-rich methanol 3-iii and the first washing gas to obtain washed flash gas 18 and the second H2S-rich methanol 17.

[0098] According to the present application, as shown in Figure 1As shown, in the reabsorption tower T-5, a first flash section is used to flash the first CO2 flash liquid 15-i to obtain the semi-lean liquid methanol 8 and a first CO2 product gas; a second flash section is used to flash the second CO2 flash liquid 15-ii to obtain a second flash liquid and a second CO2 product gas; a third flash section is used to flash the H2S flash liquid 19 to obtain the first H2S-rich methanol 23, and to obtain a sulfur-containing gas phase which is contacted with the second flash liquid through a rising hole and is subjected to a third washing to obtain the low-sulfur methanol 20 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 the CO2 product gas 22.

[0099] According to the present application, preferably, as shown in Figure 1 As shown, according to the direction of material flow, a first pump P-1 is arranged on the pipeline connecting the first washing section and the second H2S absorption section, for pressurizing the low-H2S methanol 21 after the first pressurization to carry out the second H2S absorption.

[0100] According to the present application, preferably, as shown in Figure 1 As shown, according to the direction of material flow, a first cooler E-1 is arranged on the pipeline connecting the second CO2 absorption section, the first CO2 absorption section and the CO2 flash section, for cooling the second-stage CO2-rich methanol 12 after the first cooling to divide the second-stage CO2-rich methanol 12 into the first second-stage CO2-rich methanol 12-i and the second second-stage CO2-rich methanol 12-ii, respectively, to carry out the first CO2 absorption and the CO2 flash.

[0101] According to the present application, preferably, as shown in Figure 1 As shown, according to the direction of material flow, a second cooler E-2 is arranged on the pipeline connecting the third CO2 absorption section and the second CO2 absorption section, for cooling the third-stage CO2-rich methanol 13 after the second cooling to carry out the second CO2 absorption.

[0102] According to the present application, preferably, as shown in Figure 1 As shown, according to the direction of material flow, a second pump P-2 is arranged on the pipeline connecting the first flash section and the third CO2 absorption section, for pressurizing the first semi-lean liquid methanol 8-i after the second pressurization to carry out the third CO2 absorption.

[0103] According to the present application, preferably, as shown in Figure 1 As shown, according to the direction of material flow, a third cooler E-3 is arranged on the pipeline connecting the second H2S absorption section and the first CO2 absorption section, for cooling the first-stage CO2-rich methanol 9 after the third cooling to carry out the second H2S absorption.

[0104] According to the present application, preferably, as shown in Figure 1As shown, a fourth cooler E-4 is installed on the pipeline connecting the first cooler E-1 and the CO2 flash section, which is used to perform CO2 flash evaporation on the second secondary CO2-rich methanol 12-ii after the second cooler is cooled in the fourth cooler.

[0105] According to the present invention, preferably, such as Figure 1 As shown, a fifth cooler E-5 is installed on the pipeline connecting the second H2S absorption section and the H2S flash evaporation section, which is used to perform H2S flash evaporation on the secondary H2S-rich methanol 11 after the fifth cooling.

[0106] According to the present invention, preferably, such as Figure 1 As shown, according to the material flow direction, a third pump P-3 is installed on the pipeline connecting the second flash section and the second washing section. This pump is used to divide the low-sulfur methanol 20 into the first stream of low-sulfur methanol 20-i and the second stream of low-sulfur methanol 20-ii after the material is pressurized. The second washing is performed on the first stream of low-sulfur methanol 20-i and the second stream of low-sulfur methanol 20-ii, respectively, and the second stream of low-sulfur methanol 20-ii is sent to the subsequent process.

[0107] According to the present invention, preferably, such as Figure 1 As shown, a sixth cooler E-6 is installed on the pipeline connecting the CO2 flash section and the first flash section, which is used to cool the second CO2 flash liquid 15-ii before performing the second flash evaporation.

[0108] The present invention will be described in detail below through embodiments.

[0109] In this invention, unless otherwise specified, both syngas and non-conversion gas are derived from the coal-water slurry gasification unit.

[0110] Example 1

[0111] Devices such as ​ As shown, the device includes: a non-shift gas purification tower T-1, an H2S absorption tower T-2, a CO2 absorption tower T-3, a medium-pressure flash evaporator T-4, a reabsorption tower T-5, 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, and a sixth cooler E-6, as well as a first pump P-1, a second pump P-2, and a third pump P-3;

[0112] The method is carried out in the above-described apparatus and includes:

[0113] 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 5.5-6 MPa(G)) and the second non-shifted H2S-rich methanol 3-ii are contacted at a molar flow ratio of 50-60:1 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 non-shifted CO2-rich methanol 14-ii are contacted and subjected to second purification, to obtain non-shifted H2S-rich methanol 3 (molar content of H2S is 1.2-1.6%, molar content of CO2 is 4-9%; temperature is -30 to -26℃; pressure is 5.5-6 MPa(G)) and desulfurized non-shifted gas; the above desulfurized non-shifted gas and the first methanol-lean 2-i are contacted and subjected to third purification, to obtain non-shifted CO2-rich methanol 14 (molar content of H2S is 0.5-1 ppm, molar content of CO2 is 5-8%; temperature is -35 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 5.4-6 MPa(G));

[0114] wherein the above non-shifted H2S-rich methanol 3 is divided into the first non-shifted H2S-rich methanol 3-i, the second non-shifted H2S-rich methanol 3-ii and the third non-shifted H2S-rich methanol 3-iii at a molar flow ratio of 5-7:1:32-35; wherein the above non-shifted CO2-rich methanol 14 is divided into the first non-shifted CO2-rich methanol 14-i and the second non-shifted CO2-rich methanol 14-ii at a molar flow ratio of 1:1-2;

[0115] wherein the molar flow ratio of the above second non-shifted CO2-rich methanol 14-ii and the non-shifted gas 1 is 1:1-2; the molar flow ratio of the above first methanol-lean 2-i and the non-shifted gas 1 is 1.5-2.5:1-2;

[0116] 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 first non-shift H2S-rich methanol 3-i are contacted at a molar flow ratio of 60-70:1 and a first H2S absorption is carried out to obtain a pre-desulfurized gas and a first H2S-rich methanol 7 (molar content of H2S is 2.4-2.9%, molar content of CO2 is 66-71%); the above pre-desulfurized gas, low H2S methanol 21 (first pressurized to 5.6-6 MPa(G)), first CO2-rich methanol 9 (third cooled to -36 to -33°C) and the first non-shift CO2-rich methanol 14-i are contacted and a second H2S absorption is carried out to obtain a desulfurized gas 10 (molar content of H2S is 0.5-1 ppm, molar content of CO2 is 34-40%; temperature is -15 to -5°C; pressure is 5.35-5.55 MPa(G)) and a second H2S-rich methanol 11 (molar content of H2S is 1.3-1.7%, molar content of CO2 is 36-42%)

[0117] wherein the molar flow ratio of the above low H2S methanol 21 and synthesis gas 6 is 1-3:13-17; the molar flow ratio of the first CO2-rich methanol 9 and synthesis gas 6 is 5-6:13-17; the molar flow ratio of the first non-shift CO2-rich methanol 14-i and synthesis gas 6 is 1:13-17;

[0118] The above desulfurized gas 10 and the first second CO2-rich methanol 12-i are contacted at a molar flow ratio of 1:1.2-1.5 and a first CO2 absorption is carried out to obtain a first CO2-rich methanol 9 (molar content of H2S is 0.1-0.5 ppm, molar content of CO2 is 33-37%, temperature is -12 to -5°C, pressure is 5.3-5.4 MPa(G)) and a first pre-purified gas; the above first pre-purified gas and the third CO2-rich methanol 13 (second cooled to -36 to -33°C) are contacted and a second CO2 absorption is carried out to obtain a second CO2-rich methanol 12 (molar content of H2S is 0.1-0.5 ppm, molar content of CO2 is 27-32%, temperature is -10 to -5°C, pressure is 5.3-5.4 MPa(G)) and a second pre-purified gas; the above second pre-purified gas, the first semi-lean liquid methanol 8-i (second pressurized to 5.6-6 MPa(G)) and the second lean methanol 2-ii are contacted and a third CO2 absorption is carried out to obtain a third CO2-rich methanol 13 and a purified gas 24 (molar content of H2S is ≤0.1 ppm, molar content of CO2 is ≤20 ppm; temperature is -55 to -50°C, pressure is 5.25-5.45 MPa(G));

[0119] wherein the molar flow ratio of the purified gas 24 to the first stream of semi-lean methanol 8-i is 1-3:1; the molar flow ratio of the purified gas 24 to the second stream of lean methanol 2-ii is 1:1-1.3; wherein the secondary CO2-rich methanol 12 is cooled to -20 to -18°C to form a first stream of secondary CO2-rich methanol 12-i and a second stream of secondary CO2-rich methanol 12-ii in a molar flow ratio of 1:2-3;

[0120] The second stream of secondary CO2-rich methanol 12-ii (cooled to -36 to -33°C) is subjected to CO2 flashing (at a pressure of 1.6-2 MPa (G)) to form a CO2 flash gas 16 and a CO2 flash liquid 15 (having a molar H2S content of 0.1-0.5 ppm, a molar CO2 content of 26.5-31.5%, and a temperature of -36.5 to -33.5°C); wherein the CO2 flash liquid 15 is divided into a first stream of CO2 flash liquid 15-i and a second stream of CO2 flash liquid 15-ii in a molar flow ratio of 2-4:1;

[0121] The secondary H2S-rich methanol 11 (cooled to -36 to -33°C) is subjected to H2S flashing (at a pressure of 1.6-2 MPa (G)) to form a H2S flash gas and a H2S flash liquid 19 (having a molar H2S content of 1.2-1.6%, a molar CO2 content of 35.5-41.5%, and a temperature of -36.5 to -33.5°C);

[0122] The first stream of CO2 flash liquid 15-i is subjected to first flashing (at a pressure of 0.05-0.08 MPa (G)) to form a semi-lean methanol 8 (having a molar H2S content of ≤0.5 ppm, a molar CO2 content of 28-32%, a temperature of -64 to -60°C, and a pressure of 0.05-0.08 MPa (G)) and a first stream of CO2 product gas; the second stream of CO2 flash liquid 15-ii (cooled to -52 to -48°C) is subjected to second flashing (at a pressure of 0.06-0.09 MPa (G)) to form a second flash liquid and a second stream of CO2 product gas; and the H2S flash liquid 19 is subjected to third flashing (at a pressure of 0.12-0.16 MPa (G)) to form a first H2S-rich methanol 23 (having a molar H2S content of 1.3-1.7%, a molar CO2 content of 27-32%, a temperature of -70 to -64°C, and a pressure of 0.13-0.17 MPa (G)) and a sulfur-containing gas phase; wherein the second flash liquid and the sulfur-containing gas phase are subjected to third washing to form a low-sulfur methanol 20 (having a molar H2S content of 0.4-0.8%, a molar CO2 content of 22-26%, a temperature of -64 to -60°C, and a pressure of 0.12-0.16 MPa (G)) and a third stream of CO2 product gas;

[0123] The first, second and third CO2 product gas are mixed to obtain CO2 product gas 22 (molar content of H2S≤1ppm, molar content of CO2 99.4-99.7%, temperature -65 to -60℃, pressure 0.05-0.08MPa(G));

[0124] The semi-lean methanol 8 is divided into first semi-lean methanol 8-i and second semi-lean methanol 8-ii with a molar flow ratio of 1:1-1.5; the low-sulfur methanol 20 is pressurized to 2-2.4MPa(G) by the third pressurization, and divided into first low-sulfur methanol 20-i and second low-sulfur methanol 20-ii with a molar flow ratio of 1-3:1;

[0125] The first low-sulfur methanol 20-i, CO2 flash gas 16 and H2S flash gas are contacted and subjected to first washing to obtain low-H2S methanol 21 (molar content of H2S 0.4-0.7%, molar content of CO2 24-28%, temperature -62 to -54℃) and first washing gas; the third non-shift H2S-rich methanol 3-iii is subjected to fourth flash (pressure 1.6-2MPa(G)) to obtain fourth flash liquid, which is subjected to second washing with the first washing gas to obtain washed flash gas 18 (molar content of H2 59-63%, molar content of CO 19-23%, molar content of CO2 14-18%, temperature -35 to -25℃, pressure 1.8-2MPa(G)) and second H2S-rich methanol 17 (molar content of H2S 1.1-1.5%, molar content of CO2 4-8%, temperature -33 to -28℃).

[0126] Comparative Example 1

[0127] Taking a hydrogen production device using coal water slurry gasification as an example, the effective gas (H2+CO) entering the low-temperature methanol washing device is 230000Nm 3 / h, and 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 with the above-mentioned baseline, as shown in Table 1.

[0128] Table 1

[0129]

[0130]

[0131] As can be seen from the results in Table 1, taking the hydrogen production device based on the water coal slurry gasification as an example, the multi-generation acid gas removal technology of the supporting water coal slurry gasification device provided in Example 1 has the lean methanol circulation amount of 90.4% of the lean methanol circulation amount in Comparative Example 1 (lean liquid-semi-lean liquid process), the semi-lean liquid methanol circulation amount of 73.3% of the semi-lean liquid methanol circulation amount in Comparative Example 1 (lean liquid-semi-lean liquid process), the rich CO2 methanol usage amount in the H2S absorption tower of 78.9% of the rich CO2 methanol usage amount in Comparative Example 1 (lean liquid-semi-lean liquid process), and the cumulative reduction of external cold consumption of 1100 KW / h, and the overall energy saving effect is remarkable.

[0132] 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 the disclosed content of the present application and belong to 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: The non-conversion gas (1) is purified in three stages to obtain pre-purified non-conversion H2S-rich methanol (4), non-conversion H2S-rich methanol (3) split into three streams, non-conversion CO2-rich methanol (14) split into two streams, and purified non-conversion gas (5); the synthesis gas (6) is subjected to two-stage H2S absorption to obtain primary H2S-rich methanol (7), secondary H2S-rich methanol (11), and desulfurized gas (10); the desulfurized gas (10) is subjected to three-stage CO2 absorption to obtain primary CO2-rich methanol (9), secondary CO2-rich methanol (12) split into two streams, The process consists of three stages of CO2-rich methanol (13) and purified gas (24); wherein, the first non-conversion H2S-rich methanol (3-i), the first non-conversion CO2-rich methanol (14-i), and the first-stage CO2-rich methanol (9) are returned to the two-stage H2S absorption, respectively; the second non-conversion H2S-rich methanol (3-ii) and the second non-conversion CO2-rich methanol (14-ii) are returned to the three-stage purification, respectively; and the first secondary CO2-rich methanol (12-i) and the third-stage CO2-rich methanol (13) are returned to the three-stage CO2 absorption, respectively. The second secondary CO2-rich methanol (12-ii) and the second secondary H2S-rich methanol (11) were subjected to CO2 flash evaporation and H2S flash evaporation, respectively, to obtain CO2 flash liquid (15) divided into two streams, H2S flash liquid (19), CO2 flash vapor (16), and H2S flash vapor; among them, the first CO2 flash liquid (15-i), the second CO2 flash liquid (15-ii), and the H2S flash liquid (19) were subjected to first flash evaporation, second flash evaporation, and third flash evaporation, respectively, to obtain semi-lean methanol ( 8) The methanol is divided into two streams: low-sulfur methanol (20) and first H2S-rich methanol (23); the first semi-lean methanol (8-i) is returned to the three-stage CO2 absorption; the first low-sulfur methanol (20-i), CO2 flash vapor (16) and H2S flash vapor are washed for the first time, and the resulting low-H2S methanol (21) is returned to the two-stage H2S absorption; the third non-conversion H2S-rich methanol (3-iii) is subjected to a fourth flash evaporation to obtain a fourth flash liquid and the first washing gas is washed for the second time.

2. The method according to claim 1, wherein, The three-stage purification includes: a first purification, a second purification, and a third purification; wherein, the second non-conversion H2S-rich methanol (3-ii) returns to the first purification; the second non-conversion CO2-rich methanol (14-ii) returns to the second purification; Preferably, the two-stage H2S absorption includes: a first H2S absorption and a second H2S absorption; wherein, the first non-conversion H2S-rich methanol (3-i) is returned to the first H2S absorption; the first non-conversion CO2-rich methanol (14-i), the first-stage CO2-rich methanol (9), and the low-H2S methanol (21) are respectively 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; wherein, the first secondary CO2-rich methanol (12-i) returns to the first CO2 absorption, the third CO2-rich methanol (13) returns to the second CO2 absorption, and the first semi-lean methanol (8-i) returns to the third CO2 absorption.

3. The method according to claim 2, wherein, The non-conversion gas (1) and the second non-conversion H2S-rich methanol (3-ii) are contacted and subjected to the first purification to obtain the pre-purified non-conversion H2S-rich methanol (4) and the pre-desulfurized non-conversion gas; the pre-desulfurized non-conversion gas and the second non-conversion CO2-rich methanol (14-ii) are contacted and subjected to the second purification to obtain the non-conversion H2S-rich methanol (3) and the desulfurized non-conversion gas; the desulfurized non-conversion gas and the first lean methanol (2-i) are contacted and subjected to the third purification to obtain the non-conversion CO2-rich methanol (14) and the purified non-conversion gas (5); Preferably, the non-conversion H2S-rich methanol (3) has a molar content of 1.2-1.6% for H2S and a molar content of 4-9% for CO2; a temperature of -30 to -26°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 5-7:1:32-35; Preferably, the non-conversion CO2-rich methanol (14) has a molar content of H2S of 0.5-1 ppm and a molar content of CO2 of 5-8%; and the temperature is -40 to -33°C. Preferably, the molar flow ratio of the first non-conversion CO2-rich methanol (14-i) and the second non-conversion CO2-rich methanol (14-ii) is 1:1-2; Preferably, the molar content of H2S in the purified non-conversion gas (5) is ≤0.1ppm, the molar content of CO2 is ≤20ppm, the temperature is -55 to -45℃, and the pressure is 5.4-6MPa(G).

4. The method according to claim 2, wherein, The syngas (6) and the first non-conversion H2S-rich methanol (3-i) are contacted and subjected to the first H2S absorption to obtain the first-stage H2S-rich methanol (7) and pre-desulfurized gas; the pre-desulfurized gas, low-H2S methanol (21), first-stage CO2-rich methanol (9) and the first non-conversion CO2-rich methanol (14-i) are contacted and subjected to the second H2S absorption to obtain the desulfurized gas (10) and second-stage H2S-rich methanol (11); Preferably, the molar content of H2S in the secondary H2S-rich methanol (11) is 1.3-1.7%, and the molar content of CO2 is 36-42%; the temperature is -10 to -5℃. Preferably, the desulfurization gas (10) has a molar content of H2S of 0.5-1 ppm and a molar content of CO2 of 34-40%; a temperature of -15 to -5°C; and a pressure of 5.35-5.55 MPa(G). Preferably, the low-H2S methanol (21) is pressurized to 5.6-6 MPa (G) in the first stage according to the material flow direction for the second H2S absorption; Preferably, the desulfurized gas (10) and the first secondary CO2-rich methanol (12-i) are contacted and the first CO2 absorption is performed to obtain the primary CO2-rich methanol (9) and the first pre-purified gas; The first pre-purified gas and the third-stage CO2-rich methanol (13) are contacted and the second CO2 absorption is performed to obtain the second-stage CO2-rich methanol (12) and the second pre-purified gas. The second pre-purified gas, the first semi-lean methanol (8-i), and the second lean methanol (2-ii) are contacted and the third CO2 absorption is performed to obtain the three-stage CO2-rich methanol (13) and purified gas (24). Preferably, the molar content of H2S in the first-grade CO2-rich methanol (9) is 0.1-0.5 ppm, the molar content of CO2 is 33-37%, the temperature is -12 to -5℃, and the pressure is 5.3-5.4 MPa(G); Preferably, the molar content of H2S in the secondary CO2-rich methanol (12) is 0.1-0.5 ppm, the molar content of CO2 is 27-32%, the temperature is -10 to -5℃, and the pressure is 5.3-5.4 MPa(G); Preferably, the molar flow ratio of the first secondary CO2-rich methanol (12-i) and the second secondary CO2-rich methanol (12-ii) is 1:2-3; More preferably, the secondary CO2-rich methanol (12) is cooled to -20 to -18°C and divided into a first stream of secondary CO2-rich methanol (12-i) and a second stream of secondary CO2-rich methanol (12-ii); Preferably, the third-stage CO2-rich methanol (13) is cooled to -36 to -33°C in the second cooling process according to the material flow direction for the second CO2 absorption. Preferably, the first semi-lean methanol (8-i) is pressurized to 5.6-6 MPa (G) in the second pressurization process according to the material flow direction, and then subjected to the third CO2 absorption. Preferably, the first-stage CO2-rich methanol (9) is cooled to -36 to -33°C in the third stage according to the material flow direction, and then the second H2S absorption is carried out.

5. The method according to any one of claims 1-4, wherein, The second secondary CO2-rich methanol (12-ii) is cooled to -36 to -33°C in a fourth cooling process to perform CO2 flash evaporation. Preferably, the secondary H2S-rich methanol (11) is cooled to -36 to -33°C in a fifth cooling process to perform H2S flash evaporation; Preferably, the pressures for CO2 flash evaporation and H2S flash evaporation are 1.6-2 MPa(G); Preferably, the CO2 flash liquid (15) has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 26.5-31.5%, and a temperature of -36.5 to -33.5°C; Preferably, the molar flow ratio of the first CO2 flash liquid (15-i) and the second CO2 flash liquid (15-ii) is 2-4:1; Preferably, the H2S flash liquid (19) has a molar content of 1.2-1.6% for H2S and a molar content of 35.5-41.5% for CO2; and a temperature of -36.5 to -33.5°C.

6. The method according to any one of claims 1-5, wherein, The first CO2 flash liquid (15-i) is subjected to the first flash evaporation to obtain the semi-lean methanol (8) and the first CO2 product gas; the second CO2 flash liquid (15-ii) is subjected to the second flash evaporation to obtain the second flash liquid and the second CO2 product gas; the H2S flash liquid (19) is subjected to the third flash evaporation to obtain the first H2S-rich methanol (23) and the sulfur-containing gas phase; The second flash liquid and sulfur-containing gas phase are contacted and washed a third time to obtain low-sulfur methanol (20) and a third CO2 product gas; 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 CO2 flash liquid (15-ii) is cooled to -52 to -48°C in a sixth cooling process for the second flash evaporation; Preferably, the semi-lean methanol (8) has a molar content of H2S ≤0.5ppm, a molar content of CO2 of 28-32%, a temperature of -64 to -60℃, and a pressure of 0.05-0.08MPa(G); Preferably, the molar flow ratio of the first semi-lean methanol (8-i) and the second semi-lean methanol (8-ii) is 1:1-1.5; Preferably, the low-sulfur methanol (20) has a molar content of H2S of 0.4-0.8% and a molar content of CO2 of 22-26%; the temperature is -64 to -60°C and the pressure is 0.12-0.16 MPa(G); Preferably, the molar flow ratio of the first stream of low-sulfur methanol (20-i) and the second stream of low-sulfur methanol (20-ii) is 1-3:1; Preferably, according to the material flow direction, the low-sulfur methanol (20) is pressurized to 2-2.4 MPa (G) for the third time and divided into the first stream of low-sulfur methanol (20-i) and the second stream of low-sulfur methanol (20-ii); Preferably, the molar content of H2S in the CO2 product gas (22) is ≤1ppm, the molar content of CO2 is 99.4-99.7%, the temperature is -65 to -60℃, and the pressure is 0.05-0.08MPa(G).

7. The method according to any one of claims 1-6, wherein, The first stream of low-sulfur methanol (20-i), the CO2 flash vapor (16), and the H2S flash vapor are contacted and subjected to the first wash to obtain the low-H2S methanol (21) and the first wash gas; Preferably, the low-H2S methanol (21) has a molar content of H2S of 0.4-0.7% and a molar content of CO2 of 24-28%; and the temperature is -62 to -54°C. Preferably, the pressure of the fourth flash evaporation is 1.6-2 MPa(G); Preferably, the fourth flash liquid is contacted with the first washing gas and subjected to the second washing to obtain washed flash vapor (18) and second H2S-rich methanol (17).

8. A multi-generation acid gas removal device for supporting a water coal slurry gasification device, characterized in that, The device includes: a non-shift gas purification tower (T-1), an H2S absorption tower (T-2), a CO2 absorption tower (T-3), a medium-pressure flash evaporator (T-4), and a reabsorption tower (T-5) connected together; The non-shift gas purification tower (T-1) is used to perform three-stage purification of non-shift gas (1) to obtain pre-purified non-shift H2S-rich methanol (4), non-shift H2S-rich methanol (3) split into three streams, non-shift CO2-rich methanol (14) split into two streams, and purified non-shift gas (5); the H2S absorption tower (T-2) is used to perform two-stage H2S absorption of syngas (6) to obtain first-stage H2S-rich methanol (7), second-stage H2S-rich methanol (11), and desulfurized gas (10); the CO2 absorption tower (T-3) is used to perform three-stage CO2 absorption of the desulfurized gas (10) to obtain first-stage CO2-rich methanol (9), second-stage CO2-rich methanol (12) split into two streams, third-stage CO2-rich methanol (13), and purified gas (24); Among them, the first non-conversion H2S-rich methanol (3-i), the first non-conversion CO2-rich methanol (14-i), and the first-stage CO2-rich methanol (9) are returned to the H2S absorption tower (T-2); the second non-conversion H2S-rich methanol (3-ii) and the second non-conversion CO2-rich methanol (14-ii) are returned to the non-conversion gas purification tower (T-1); the first secondary CO2-rich methanol (12-i) and the tertiary CO2-rich methanol (13) are returned to the CO2 absorption tower (T-3). The medium-pressure flash evaporator (T-4) is divided into a CO2 flash evaporation section, a second washing section, a first washing section, and an H2S flash evaporation section from top to bottom. The CO2 flash evaporation section is used to perform CO2 flash evaporation on the second secondary CO2-rich methanol (12-ii), and the resulting CO2 flash vapor (16) is sent to the H2S flash evaporation section through a pipeline, and the resulting CO2 flash liquid (15) is divided into two streams. The H2S flash evaporation section is used to perform H2S flash evaporation on the secondary H2S-rich methanol (11), and the resulting H2S flash vapor and the CO2 flash vapor (16) are sent to the first washing section through the riser holes, and the resulting H2S flash liquid (19) is obtained. The reabsorption tower (T-5) is divided into a first flash section, a second flash section and a third flash section from top to bottom, which are used to perform the first flash, second flash and third flash of the first CO2 flash liquid (15-i), the second CO2 flash liquid (15-ii) and the H2S flash liquid (19) respectively, to obtain semi-lean methanol (8) in two streams, low-sulfur methanol (20) in two streams and the first H2S rich methanol (23); The first semi-lean methanol (8-i) is returned to the CO2 absorption tower (T-3); the first washing section is used to perform a first washing on the first low-sulfur methanol (20-i), CO2 flash vapor (16) and H2S flash vapor, and the resulting low-H2S methanol (21) is returned to the H2S absorption tower (T-2), and the resulting first washing gas is sent to the second washing section through the riser hole, and is used for a second washing with the fourth flash liquid obtained by the fourth flash evaporation of the third non-conversion rich H2S methanol (3-iii).

9. The apparatus according to claim 8, wherein, The non-conversion 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 connected by air risers. Specifically, the second non-converted H2S-rich methanol (3-ii) returns to the first purification section; the second non-converted CO2-rich methanol (14-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, which are connected by air risers from bottom to top. Among them, the first non-conversion H2S-rich methanol (3-i) returns to the first H2S absorption section; the first non-conversion CO2-rich methanol (14-i), the first-level CO2-rich methanol (9) and the low H2S methanol (21) 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, which are connected by air risers. Specifically, the first secondary CO2-rich methanol (12-i) returns to the first CO2 absorption section, the tertiary CO2-rich methanol (13) returns to the second CO2 absorption section, and the first semi-lean methanol (8-i) returns to the third CO2 absorption section.

10. The apparatus according to claim 9, wherein, A first pump (P-1) is installed on the pipeline connecting the first washing section and the second H2S absorption section in accordance with the material flow direction. Preferably, a first cooler (E-1) is installed on the pipe connecting the second CO2 absorption section, the first CO2 absorption section and the CO2 flash section, according to the material flow direction; Preferably, a second cooler (E-2) is installed on the pipe connecting the third CO2 absorption section and the second CO2 absorption section, according to the material flow direction; Preferably, a second pump (P-2) is installed on the pipeline connecting the first flash section and the third CO2 absorption section, according to the material flow direction; Preferably, a third cooler (E-3) is installed on the pipe connecting the second H2S absorption section and the first CO2 absorption section, according to the material flow direction; More preferably, a fourth cooler (E-4) is provided on the pipe connecting the first cooler (E-1) and the CO2 flash section; Preferably, a fifth cooler (E-5) is provided on the pipe connecting the second H2S absorption section and the H2S flash section; Preferably, a third pump (P-3) is installed on the pipe connecting the second flash section and the second washing section, according to the material flow direction; Preferably, a sixth cooler (E-6) is provided on the pipe connecting the CO2 flash section and the second flash section.

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