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

Abstract

The invention relates to the technical field of low-temperature methanol washing, in particular to an energy-saving poly-generation acid gas removal method matched with a coal water slurry gasification device and an energy-saving poly-generation acid gas removal device matched with the coal water slurry gasification device. The method has the characteristics of classified flash evaporation, classified washing and secondary full utilization of washing liquid by optimally setting a medium-pressure flash evaporation process; the reabsorption process is optimized, so that low-sulfur methanol is generated and is reutilized; the gas stripping process is optimized, the semi-barren solution methanol, the first H2S-rich methanol, the low-sulfur methanol and the third H2S-rich methanol are adopted, and H2S-rich gas stripping gas generated by gas stripping is subjected to series absorption, so that the method has the characteristic of low comprehensive energy consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-temperature methanol washing, in particular to 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] The low-temperature methanol washing process is a mainstream process technology for removing acid gases matched with a coal water slurry gasification. In the low-temperature methanol washing process, the methanol containing H2S must be recycled by heat regeneration, which is the main source of energy consumption of the low-temperature methanol washing. Therefore, firstly, the total amount of the methanol containing H2S generated should be optimized to reduce, and secondly, the use efficiency of the methanol containing H2S should be strengthened. At the same time, the setting of the medium-pressure flash process is also particularly important, which should not only ensure that the effective gas is recovered with less compression power, but also ensure that the washing liquid of the flash gas has the least impact on the flashed liquid, and also ensure that the washing liquid can be used twice to reduce the comprehensive energy consumption of the low-temperature methanol washing.

[0003] CN201110260570.0 discloses a low-temperature methanol washing process. Firstly, 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, and the contaminated H2S-rich methanol can only be recycled after heat regeneration, which is high in energy consumption. Secondly, the CO2 gas flashed from the upper section of the medium-pressure flash tower is sent to the lower section of the medium-pressure flash tower to be washed and absorbed by the H2S-rich methanol. The CO2 gas after washing is contaminated, and the rich liquid after washing cannot be used twice, which is high in energy consumption. Thirdly, in the CO2 flashing section of the reabsorption tower, the CO2-rich methanol is directly mixed with the H2S-rich methanol while washing the H2S-rich methanol flash gas, and the CO2-rich methanol is contaminated by the H2S-rich methanol. The low-concentration H2S methanol produced is not fully used, which is high in energy consumption.

[0004] CN201810994082.4 discloses a low-temperature methanol washing system and a method for providing synthesis gas. The technology uses the non-transformed H2S-rich methanol after washing the non-transformed gas as the washing methanol for the flash gas produced by the medium-pressure flashing of the H2S-rich methanol. Therefore, there is still room for technical improvement and energy consumption reduction. SUMMARY

[0005] The present application aims to overcome the problems of low use efficiency of non-reformed CO2-rich methanol and non-reformed H2S-rich methanol after washing of non-reformed gas, and unreasonable setting of the medium-pressure flash process in the prior art of poly-generation low-temperature methanol washing technology, and provides an energy-saving poly-generation acid gas removal method matched with a coal water slurry gasification device and an energy-saving poly-generation acid gas removal device matched with a coal water slurry gasification device. The method has the characteristics of classified flash, classified washing and secondary full use of washing liquid by optimizing the setting of the medium-pressure flash process. The low-sulfur methanol is generated by optimizing the setting of the re-absorption process and is used secondarily. The H2S-rich gas stripping gas generated by the gas stripping process is absorbed in series by using semi-lean liquid methanol, first H2S-rich methanol, low-sulfur methanol and third H2S-rich methanol, and the method has the characteristic of low comprehensive energy consumption.

[0006] In order to achieve the above-mentioned purpose, the present application provides an energy-saving poly-generation acid gas removal method matched with a coal water slurry gasification device, which comprises the following steps:

[0007] (1) sequentially performing first H2S absorption and second H2S absorption on the synthesis gas from the coal water slurry gasification device to obtain first H2S-rich methanol, second H2S-rich methanol and desulfurized gas; sequentially performing first CO2 absorption and second CO2 absorption on the desulfurized gas to obtain two groups of first CO2-rich methanol, second CO2-rich methanol and purified gas;

[0008] (2) performing CO2 flash and H2S flash on the second group of first CO2-rich methanol and second H2S-rich methanol respectively to obtain CO2 flash liquid, CO2 flash gas, H2S flash liquid and H2S flash gas; wherein the CO2 flash liquid, second semi-lean liquid methanol and H2S flash liquid are subjected to first flash, second flash and third flash respectively to obtain two groups of semi-lean liquid methanol, low-sulfur methanol and first H2S-rich methanol;

[0009] (3) performing gas stripping on the first H2S-rich methanol, low-sulfur methanol, second H2S-rich methanol and third H2S-rich methanol respectively, and performing first washing on the gas stripping gas and the first group of semi-lean liquid methanol to obtain the second H2S-rich methanol;

[0010] The non-reformed H2S-rich methanol is divided into three streams and the non-reformed CO2-rich methanol is divided into two streams; the first stream of non-reformed H2S-rich methanol and the second stream of non-reformed H2S-rich methanol are returned to the first H2S absorption and non-reformed gas purification process respectively, the third stream of non-reformed H2S-rich methanol and H2S flash gas are subjected to second washing to obtain the third H2S-rich methanol; the first stream of non-reformed CO2-rich methanol is divided into a stream of non-reformed CO2-rich methanol and a stream of non-reformed CO2-rich methanol, which are returned to the second CO2 absorption respectively and subjected to third washing with the CO2 flash gas; and the second stream of non-reformed CO2-rich methanol is returned to the non-reformed gas purification process.

[0011] 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, which comprises a non-reformed gas purification tower, an H2S absorption tower, a CO2 absorption tower, a medium-pressure flash tower and a reabsorption tower connected;

[0012] The non-reformed gas purification tower is used for sequentially performing first purification, second purification and third purification on non-reformed gas from the coal water slurry gasification device to obtain pre-purified non-reformed H2S-rich methanol, three streams of non-reformed H2S-rich methanol, two streams of non-reformed CO2-rich methanol and purified non-reformed gas;

[0013] The H2S absorption tower is used for sequentially performing first H2S absorption and second H2S absorption on synthesis gas from the coal water slurry gasification device to obtain primary H2S-rich methanol, secondary H2S-rich methanol and desulfurized gas; and the CO2 absorption tower is used for sequentially performing first CO2 absorption and second CO2 absorption on the desulfurized gas to obtain two streams of primary CO2-rich methanol, secondary CO2-rich methanol and purified gas;

[0014] The medium-pressure flash tower is divided into a CO2 washing section, a CO2 flash section, an H2S washing section and an H2S flash section from top to bottom; the CO2 flash section is used for performing CO2 flashing on the second stream of primary CO2-rich methanol to obtain CO2 flash gas and CO2 flash liquid; and the H2S flash section is used for performing H2S flashing on the secondary H2S-rich methanol to obtain H2S flash gas and H2S flash liquid;

[0015] The reabsorption tower comprises an upper tower and a lower tower, wherein the upper tower is divided into a first flash evaporation section, a second flash evaporation section and a third flash evaporation section from top to bottom, respectively used for first flash evaporation, second flash evaporation and third flash evaporation of the CO2 flash evaporation liquid, the second half-lean liquid methanol and the H2S flash evaporation liquid respectively to obtain two stocks of half-lean liquid methanol, low-sulfur methanol and first H2S-rich methanol; the lower tower is divided into a washing section and a gas stripping section from top to bottom, and the gas stripping section is used for gas stripping of the first H2S-rich methanol, the low-sulfur methanol, the second H2S-rich methanol and the third H2S-rich methanol respectively to obtain gas stripping gas sent to the washing section through a riser to perform first washing with the first stock of half-lean liquid methanol, thereby obtaining the second H2S-rich methanol;

[0016] The first stock of non-shift H2S-rich methanol and the second stock of non-shift H2S-rich methanol are returned to the first H2S absorption section and the non-shift gas purification tower respectively, and the third stock of non-shift H2S-rich methanol is sent to the H2S washing section to perform second washing with the H2S flash evaporation gas, thereby obtaining the third H2S-rich methanol; the first stock of non-shift CO2-rich methanol is divided into a stock of non-shift CO2-rich methanol and a stock of non-shift CO2-rich methanol, which are returned to the second CO2 absorption section and sent to the CO2 washing section to perform third washing with the CO2 flash evaporation gas respectively; and the second stock of non-shift CO2-rich methanol is returned to the non-shift gas purification tower.

[0017] Compared with the prior art, the present application has the following advantages:

[0018] (1) The method provided by the present application optimizes the medium-pressure flash evaporation process, absorbs the H2S flash evaporation gas by introducing non-shift H2S-rich methanol, and absorbs the CO2 flash evaporation gas by introducing non-shift CO2-rich methanol, thereby realizing classified flash evaporation and classified washing of the second stock of primary CO2-rich methanol and the secondary H2S-rich methanol, and the third H2S-rich methanol generated is subjected to gas stripping, which is beneficial to reducing the energy consumption of the device;

[0019] (2) The method provided by the present application divides the non-shift H2S-rich methanol derived from the non-shift gas purification process into three stocks, wherein the first stock of non-shift H2S-rich methanol and the second stock of non-shift H2S-rich methanol are used for treating synthesis gas and non-shift gas, and under the premise of achieving the same washing effect, the use amount of the first stock of primary CO2-rich methanol is reduced, which is of positive significance to reducing the energy consumption of the low-temperature methanol washing device;

[0020] (3) The method provided by the present application optimizes the reabsorption process, realizes the absorption of the sulfur-containing gas phase generated by the third flash evaporation of the flash evaporation liquid of the second stock of half-lean liquid methanol on the H2S flash evaporation liquid, and the first H2S-rich methanol after flash evaporation is not mixed with each other;

[0021] (4) The method provided by the application adopts four tail gas washing technologies, and according to the H2S content in the tail gas, four different H2S content methanols are selectively arranged from high to low to sequentially perform first washing, so that the least semi-lean liquid methanol is used under the premise that the tail gas emission meets the standard, and the heat regeneration energy consumption of the whole low-temperature methanol washing is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a structural schematic diagram of an energy-saving multi-production acid gas removal device matched with a coal water slurry gasification device.

[0023] BRIEF DESCRIPTION OF DRAWINGS

[0024] 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;

[0025] E-1, first cooler; E-2, second cooler; E-3, third cooler; E-4, fourth cooler; E-5, fifth cooler; P, pump; Q-1, first heat exchanger; Q-2, second heat exchanger; Q-3, third heat exchanger;

[0026] 1, non-shift gas; 2, non-shift H2S-rich methanol; 2-i, first non-shift H2S-rich methanol; 2-ii, second non-shift H2S-rich methanol; 2-iii, third non-shift H2S-rich methanol; 3, lean methanol; 3-i, first lean methanol; 3-ii, second lean methanol; 4, pre-purified non-shift H2S-rich methanol; 5, purified non-shift gas; 6, synthesis gas; 7, primary H2S-rich methanol; 8, non-shift CO2-rich methanol; 8-i, first non-shift CO2-rich methanol; 8-i-a, a non-shift CO2-rich methanol; 8-i-b, b non-shift CO2-rich methanol; 8-ii, second non-shift CO2-rich methanol; 9, primary CO2-rich methanol; 9-i, first primary CO2-rich methanol; 9-ii, second primary CO2-rich methanol; 10, secondary H2S-rich methanol; 11, desulfurized gas; 12, secondary CO2-rich methanol; 13, semi-lean liquid methanol; 13-i, first semi-lean liquid methanol; 13-ii, second semi-lean liquid methanol; 14, purified gas; 15, tail gas; 16, second H2S-rich methanol; 17, H2S-rich methanol after gas stripping; 18, H2S flash gas after washing; 19, H2S flash liquid; 20, first H2S-rich methanol; 21, low-sulfur methanol; 22, CO2 product gas; 23, CO2 flash gas after washing; 24, CO2 flash liquid; 25, third H2S-rich methanol; 26, nitrogen. DETAILED DESCRIPTION

[0027] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numeric range recited is intended to include all values from the lower value to the upper value, inclusive of both values, and to sub-ranges falling within the specified range. In this context, individual points within a range should not be dismissed from the scope of the range. For numeric ranges, the endpoints of each range, the endpoints of each range and individual point values, and individual point values can be combined with each other to generate one or more new numeric ranges, which should be considered as specifically disclosed herein.

[0028] In the present invention, without special circumstances, "first", "second", "third", "fourth" and "fifth" neither represent the order of precedence, nor represent the limitation of each material or step, but are used to distinguish or indicate that it is not the same step or material.

[0029] In the present invention, without special circumstances, 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 invention provides an energy-saving multi-generation acid gas removal method matched with a coal water slurry gasification device, the method comprising:

[0031] (1) The synthesis gas from the coal water slurry gasification device is sequentially subjected to first H2S absorption and second H2S absorption to obtain primary H2S-rich methanol, secondary H2S-rich methanol and desulfurized gas; the desulfurized gas is sequentially subjected to first CO2 absorption and second CO2 absorption to obtain two streams of primary CO2-rich methanol, secondary CO2-rich methanol and purified gas;

[0032] (2) The second stream of primary CO2-rich methanol and the secondary H2S-rich methanol are respectively subjected to CO2 flashing and H2S flashing to obtain CO2 flashing liquid, CO2 flashing gas, H2S flashing liquid and H2S flashing gas; wherein the CO2 flashing liquid, the second stream of semi-lean liquid methanol and the H2S flashing liquid are respectively subjected to first flashing, second flashing and third flashing to obtain two streams of semi-lean liquid methanol, low-sulfur methanol and first H2S-rich methanol;

[0033] (3) The first H2S-rich methanol, the low-sulfur methanol, the second H2S-rich methanol and the third H2S-rich methanol are respectively subjected to gas stripping to obtain gas stripping gas, which is subjected to first washing with the first stream of semi-lean liquid methanol to obtain the second H2S-rich methanol;

[0034] The non-shift H2S-rich methanol from the non-shift gas purification process is divided into three streams and the non-shift CO2-rich methanol is divided into two streams; the first stream of non-shift H2S-rich methanol and the second stream of non-shift H2S-rich methanol are returned to the first H2S absorption and the non-shift gas purification process respectively, the third stream of non-shift H2S-rich methanol and the H2S flash gas are subjected to a second washing to obtain the third H2S-rich methanol; the first stream of non-shift CO2-rich methanol is divided into a stream of non-shift CO2-rich methanol a and a stream of non-shift CO2-rich methanol b, which are returned to the second CO2 absorption respectively and subjected to a third washing with the CO2 flash gas; the second stream of non-shift CO2-rich methanol is returned to the non-shift gas purification process.

[0035] In the present application, the synthesis gas and the non-shift gas are both derived from a coal slurry gasification device, unless otherwise specified.

[0036] In the present application, preferably, the H2S content in the synthesis gas is 0.9-1.2% by mole, the CO2 content is 40-50% by mole, the temperature is -15 to -5℃ and the pressure is 5.4-5.6 MPa(G); the H2S content in the non-shift gas is 0.9-1.2% by mole, the CO2 content is 5-10% by mole, the temperature is -35 to -25℃ and the pressure is 5.6-6 MPa(G).

[0037] In some embodiments of the present application, preferably, the non-shift gas purification process comprises: sequentially subjecting the non-shift gas derived from a coal slurry gasification device to a first purification, a second purification and a third purification to obtain a pre-purified non-shift H2S-rich methanol, a non-shift H2S-rich methanol, a non-shift CO2-rich methanol and a purified non-shift gas.

[0038] In some embodiments of the present application, preferably, the second stream of non-shift H2S-rich methanol is returned to the first purification; the second stream of non-shift CO2-rich methanol is returned to the second purification.

[0039] In the present application, the first purification aims to remove HCN, NH3 and other impurities and a small amount of H2S and CO2 from the non-shift gas; the second purification aims to further remove H2S from the non-shift gas; and the third purification aims to further remove CO2 from the non-shift gas.

[0040] In some embodiments of the present application, further preferably, the non-reformed gas and the second non-reformed H2S-rich methanol are contacted and subjected to the first purification to obtain the pre-purified non-reformed H2S-rich methanol and 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 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 purified non-reformed gas.

[0041] In the present application, preferably, the molar flow ratio of the non-reformed gas and the second non-reformed H2S-rich methanol is 165-175:1; the molar content of H2S in the pre-purified non-reformed H2S-rich methanol is 1.8-2.2%, and the molar content of CO2 is 3-7%, which is sent to subsequent processes for treatment.

[0042] In the present application, preferably, the molar flow ratio of the second non-reformed CO2-rich methanol and the non-reformed gas is 1:1-2.

[0043] In some embodiments of the present application, preferably, the molar content of H2S in the non-reformed H2S-rich methanol is 1.4-1.8%, and the molar content of CO2 is 4-9%; the temperature is -30 to -25°C; and the pressure is 5.6-6 MPa(G).

[0044] In the present application, the non-reformed 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 second washing. Further preferably, the molar flow ratio of the first non-reformed H2S-rich methanol, the second non-reformed H2S-rich methanol, and the third non-reformed H2S-rich methanol is 5-7:1:95-100.

[0045] In the present application, preferably, the molar flow ratio of the first methanol-lean gas and the non-reformed gas is 2-3:1-2.

[0046] In some embodiments of the present application, preferably, the molar content of H2S in the methanol-lean gas is 0%, and the molar content of CO2 is 0%. In the present application, the methanol-lean gas is selected from subsequent processes. In the present application, unless otherwise specified, the methanol-lean gas is divided into a first methanol-lean gas and a second methanol-lean gas; and the present application does not limit the molar flow ratio of the first methanol-lean gas and the second methanol-lean gas.

[0047] 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 2-6%; the temperature is -42 to -38°C.

[0048] In some embodiments of the present application, further preferably, the molar flow ratio of the a non-shift CO2-rich methanol, the b non-shift CO2-rich methanol and the second non-shift CO2-rich methanol is 6-8:1:4-6.

[0049] In some embodiments of the present application, preferably, the first non-shift CO2-rich methanol is cooled to -54 to -50℃ to divide into the a non-shift CO2-rich methanol and the b non-shift CO2-rich methanol.

[0050] 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 5.5-5.9 MPa(G).

[0051] In the present application, the first H2S absorption aims to remove HCN, NH3 and other impurities in the synthesis gas, as well as a small amount of H2S and CO2; the second H2S absorption aims to further remove H2S and CO2 in the synthesis gas.

[0052] In some embodiments of the present application, preferably, the synthesis gas and the first non-shift H2S-rich methanol are contacted and the first H2S absorption is performed to obtain the primary H2S-rich methanol and the pre-desulfurization gas; the pre-desulfurization gas and the first primary CO2-rich methanol are contacted and the second H2S absorption is performed to obtain the desulfurization gas and the secondary H2S-rich methanol.

[0053] In the present application, preferably, the molar flow ratio of the synthesis gas and the first non-shift H2S-rich methanol is 60-70:1; 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 66-71%, which is sent to subsequent processes.

[0054] In the present application, preferably, the molar flow ratio of the first primary CO2-rich methanol and the synthesis gas is 1:1-3.

[0055] In some embodiments of the present application, preferably, the molar content of H2S in the secondary H2S-rich methanol is 1.4-1.9%, and the molar content of CO2 is 34-40%; the temperature is -10 to -6℃.

[0056] In some embodiments of the present application, preferably, the molar content of H2S in the desulfurization gas is 0.5-1 ppm, and the molar content of CO2 is 36-42%; the temperature is -20 to -10℃; and the pressure is 5.35-5.55 MPa(G).

[0057] In some embodiments of the present application, preferably, the first-stage CO2-rich methanol is pressurized to 5.6-6 MPa (G) in sequence, and then cooled to -46 to -43℃ in sequence, and then subjected to the second H2S absorption.

[0058] In some embodiments of the present application, 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 pre-purified gas; and the pre-purified gas, the a-stage non-shift CO2-rich methanol and the second-stage lean methanol are contacted and subjected to the second CO2 absorption to obtain the second-stage CO2-rich methanol and purified gas.

[0059] In the present application, preferably, the molar flow ratio of the desulfurized gas and the second-stage CO2-rich methanol is 1:1-1.5.

[0060] In some embodiments of the present application, preferably, the first-stage CO2-rich methanol has a H2S molar content of 0.1-0.5 ppm, a CO2 molar content of 25-30%, a temperature of -7 to -2℃ and a pressure of 5.35-5.55 MPa (G).

[0061] In some embodiments of the present application, further preferably, the molar flow ratio of the first-stage CO2-rich methanol and the second-stage CO2-rich methanol is 1:1-3.

[0062] In some embodiments of the present application, further preferably, the second-stage CO2-rich methanol is subjected to third cooling to -36 to -33℃, and then subjected to the first CO2 absorption.

[0063] In the present application, preferably, the molar flow ratio of the a-stage non-shift CO2-rich methanol and the purified gas is 1:1-2; and the molar flow ratio of the second-stage lean methanol and the purified gas is 1-1.3:1.

[0064] In some embodiments of the present application, preferably, the purified gas has a H2S molar content of ≤0.1 ppm, a CO2 molar content of ≤20 ppm, a temperature of -55 to -50℃ and a pressure of 5.25-5.45 MPa (G).

[0065] In the present application, the second-stage CO2-rich methanol is subjected to CO2 flashing to obtain CO2 flashing gas and CO2 flashing liquid; and the second-stage H2S-rich methanol is subjected to H2S flashing to obtain H2S flashing gas and H2S flashing liquid.

[0066] In some embodiments of the present application, preferably, the CO2 flashing and the H2S flashing are performed at a pressure of 1.6-2 MPa (G).

[0067] In some embodiments of the present application, preferably, the CO2 flash liquid has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 24-28%, and a temperature of -38 to -34°C.

[0068] In some embodiments of the present application, preferably, the second stream of primary CO2-rich methanol is cooled to -36 to -33°C by the fourth cooling to perform the CO2 flashing.

[0069] In some embodiments of the present application, preferably, the H2S flash liquid has a molar content of H2S of 1.4-1.9%, a molar content of CO2 of 33-39%, and a temperature of -12 to -8°C.

[0070] In some embodiments of the present application, preferably, the CO2 flash liquid is subjected to the first flashing to obtain the semi-lean liquid methanol and a first stream of CO2 product gas; the second stream of semi-lean liquid methanol is subjected to the second flashing to obtain a second flash liquid and a second stream of CO2 product gas; and the H2S flash liquid is subjected to the third flashing to obtain the first H2S-rich methanol and a sulfur-containing gas phase; wherein the second flash liquid and the sulfur-containing gas phase are contacted and subjected to a fourth washing to obtain low-sulfur methanol and a third stream of CO2 product gas; and wherein the first stream of CO2 product gas, the second stream of CO2 product gas and the third stream of CO2 product gas are mixed to obtain a CO2 product gas.

[0071] In some embodiments of the present application, preferably, the H2S flash liquid is cooled to -32 to -30°C by the fifth cooling to perform the third flashing.

[0072] 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 15-20%, and a temperature of -62 to -58°C; and a pressure of 0.05-0.08 MPa (G).

[0073] In some embodiments of the present application, further preferably, the molar flow ratio of the first stream of semi-lean liquid methanol to the second stream of semi-lean liquid methanol is 1-3:1.

[0074] In some embodiments of the present application, preferably, the low-sulfur methanol has a molar content of H2S of 0.4-0.6%, a molar content of CO2 of 16-21%, a temperature of -58 to -53°C, and a pressure of 0.12-0.16 MPa (G).

[0075] In some embodiments of the present application, preferably, the first H2S-rich methanol has a molar content of H2S of 1.4-1.9%, a molar content of CO2 of 22-27%, a temperature of -68 to -63°C, and a pressure of 0.13-0.17 MPa (G).

[0076] 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°C, and the pressure is 0.05-0.08 MPa (G).

[0077] In some embodiments of the present application, preferably, the first H2S-rich methanol, the low-sulfur methanol, the second H2S-rich methanol, and the third H2S-rich methanol are respectively contacted with nitrogen and subjected to the stripping to obtain stripping gas and H2S-rich methanol after stripping.

[0078] In some embodiments of the present application, further preferably, the first H2S-rich methanol is subjected to first heat exchange to -40 to -38°C and subjected to the stripping.

[0079] In some embodiments of the present application, further preferably, the second H2S-rich methanol is subjected to second heat exchange to -40 to -38°C and subjected to the stripping.

[0080] In some embodiments of the present application, further preferably, the low-sulfur methanol is subjected to third heat exchange to -40 to -38°C and subjected to the stripping.

[0081] In some embodiments of the present application, further preferably, the molar content of H2S in the H2S-rich methanol after stripping is 0.8-1.2%, the molar content of CO2 is 2-3%, the temperature is -50 to -45°C, and the pressure is 0.12-0.16 MPa (G), and the H2S-rich methanol after stripping is sent to a subsequent process.

[0082] In some embodiments of the present application, preferably, the first washing process comprises: first washing the stripping gas with the first semi-lean liquid methanol to obtain the second H2S-rich methanol and tail gas.

[0083] In some embodiments of the present application, further preferably, the molar content of H2S in the second H2S-rich methanol is 0.4-0.8%, the molar content of CO2 is 15-20%, and the pressure is 0.06-0.09 MPa (G).

[0084] In some embodiments of the present application, preferably, the molar content of H2S in the tail gas is 0.5-1 ppm, the molar content of CO2 is 84-88%, and the temperature is -65 to -60°C.

[0085] In some embodiments of the present application, preferably, the second washing process comprises: second washing the third non-shift H2S-rich methanol and H2S flash gas to obtain the third H2S-rich methanol and H2S flash gas after washing.

[0086] In some embodiments of the present invention, further preferably, the molar content of H2S in the third H2S-rich methanol is 1.4 - 1.8%, and the molar content of CO2 is 8 - 12%; the temperature is -22 to -18 °C.

[0087] In some embodiments of the present invention, preferably, the molar content of H2S in the H2S flash gas after washing is 1 - 1.4%, the molar content of CO2 is 16 - 20%, the molar content of CO is 58 - 62%, the molar content of H2 is 18 - 22%, the temperature is -35 to -25 °C, and the pressure is 1.6 - 2 MPa(G).

[0088] In some embodiments of the present invention, preferably, the process of the third washing includes: contacting the b-stream non-shifted CO2-rich methanol and the CO2 flash gas and performing the third washing to obtain the washed CO2 flash gas, and mixing the obtained third washing liquid into the CO2 flash liquid.

[0089] In some embodiments of the present invention, further preferably, the molar content of H2S in the washed CO2 flash gas is 0.1 - 0.5 ppm, the molar content of CO2 is 3 - 7%, the molar content of CO is 23 - 27%, the molar content of H2 is 68 - 72%; the temperature is -60 to -50 °C, and the pressure is 1.6 - 2 MPa(G).

[0090] The structural schematic diagram of an energy-saving polygeneration acid gas removal device supporting a water coal gasification device according to the second aspect of the present invention is as Figure 1 shown, and it can be seen from Figure 1 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 reabsorption tower T-5;

[0091] Among them, the non-shifted gas purification tower T-1 is used to sequentially perform the first purification, second purification, and third purification on the non-shifted gas 1 to obtain the pre-purified H2S-rich methanol 4, the non-shifted H2S-rich methanol 2 in three streams, the non-shifted CO2-rich methanol 8 in two streams, and the purified non-shifted gas 5;

[0092] The H2S absorption tower T-2 is used to sequentially perform the first H2S absorption and second H2S absorption on the syngas 6 from the water coal gasification device to obtain the first-stage H2S-rich methanol 7, the second-stage H2S-rich methanol 10, and the desulfurized gas 11; the CO2 absorption tower T-3 is used to sequentially perform the first CO2 absorption and second CO2 absorption on the desulfurized gas 11 to obtain the first-stage CO2-rich methanol 9 in two streams, the second-stage CO2-rich methanol 12, and the purified gas 14;

[0093] The medium-pressure flash tower T-4 is divided into a CO2 washing section, a CO2 flash section, an H2S washing section and an H2S flash section from top to bottom; the CO2 flash section is used for CO2 flashing of the second CO2-rich methanol 9-ii to obtain CO2 flash gas and CO2 flash liquid 24; the H2S flash section is used for H2S flashing of the second H2S-rich methanol 10 to obtain H2S flash gas and H2S flash liquid 19;

[0094] The reabsorption tower T-5 comprises an upper tower and a lower tower, wherein the upper tower is divided into a first flash section, a second flash section and a third flash section from top to bottom, and is used for first flashing, second flashing and third flashing of the CO2 flash liquid 24, the second semi-lean liquid methanol 13-ii and the H2S flash liquid 19 respectively to obtain two semi-lean liquid methanols 13, low-sulfur methanol 21 and first H2S-rich methanol 20; the lower tower is divided into a washing section and a gas stripping section from top to bottom, and the gas stripping section is used for gas stripping of the first H2S-rich methanol 20, the low-sulfur methanol 21, the second H2S-rich methanol 16 and the third H2S-rich methanol 25 respectively to obtain gas stripping gas which is sent to the washing section through a riser and is used for first washing with the first semi-lean liquid methanol 13-i to obtain the second H2S-rich methanol 16.

[0095] The first non-shift H2S-rich methanol 2-i and the second non-shift H2S-rich methanol 2-ii are returned to the first H2S absorption section and the non-shift gas purification tower T-1 respectively, and the third non-shift H2S-rich methanol 2-iii is sent to the H2S washing section and is used for second washing with the H2S flash gas to obtain the third H2S-rich methanol 25; the first non-shift CO2-rich methanol 8-i is divided into a non-shift CO2-rich methanol 8-i-a and a non-shift CO2-rich methanol 8-i-b, and is returned to the second CO2 absorption section and sent to the CO2 washing section and is used for third washing with the CO2 flash gas respectively; and the second non-shift CO2-rich methanol 8-ii is returned to the non-shift gas purification tower T-1.

[0096] In the present application, as shown in the figure, 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 through risers; the second non-shift H2S-rich methanol 2-ii is returned to the first purification section; and the second non-shift CO2-rich methanol 8-ii is returned to the second purification section.

[0097] In the present application, as shown in the figure, Figure 1As shown in the figure, in the non-shift gas purification tower T-1, a first purification section is used for contacting the non-shift gas 1 and the second non-shift H2S-rich methanol 2-ii and performing first purification to obtain pre-purified non-shift H2S-rich methanol 4 and pre-desulfurized non-shift gas; a second purification section is used for contacting the pre-desulfurized non-shift gas and the second 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 a third purification section is used for contacting the desulfurized non-shift gas and the first methanol-lean 3-i and performing third purification to obtain the non-shift CO2-rich methanol 8 and purified non-shift gas 5.

[0098] In the present application, as shown in the figure, Figure 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 in communication through a riser; wherein the first non-shift H2S-rich methanol 2-i returns to the first H2S absorption section; and the first primary CO2-rich methanol 9-i returns to the second H2S absorption section.

[0099] In the present application, as shown in the figure, Figure 1 As shown in the figure, 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 2-i and performing first H2S absorption to obtain the primary H2S-rich methanol 7 and pre-desulfurized gas; and a second H2S absorption section is used for contacting the pre-desulfurized gas and the first primary CO2-rich methanol 9-i and performing second H2S absorption to obtain desulfurized gas 11 and secondary H2S-rich methanol 10.

[0100] 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 and a second CO2 absorption section in communication through a riser; wherein the secondary CO2-rich methanol 12 returns to the first CO2 absorption section, and the a non-shift H2S-rich methanol 8-i-a and the second methanol-lean 3-ii return to the second CO2 absorption section.

[0101] In the present application, as shown in the figure, Figure 1 As shown in the figure, in the CO2 absorption tower T-3, a first CO2 absorption section is used for contacting the desulfurized gas 11 and the secondary CO2-rich methanol 12 and performing first CO2 absorption to obtain the primary CO2-rich methanol 9 and pre-purified gas; and a second CO2 absorption section is used for contacting the pre-purified gas, the a non-shift CO2-rich methanol 8-i-a and the second methanol-lean 3-ii and performing second CO2 absorption to obtain the secondary CO2-rich methanol 12 and purified gas 14.

[0102] In the present application, as shown in the figure, Figure 1As shown in the figure, the middle-pressure flash tower T-4 is divided into a CO2 washing section, a CO2 flash section, an H2S washing section and an H2S flash section from top to bottom, wherein the CO2 flash section is used for CO2 flashing of the second primary CO2-rich methanol 9-ii to obtain CO2 flash gas and CO2 flash liquid 24; the H2S flash section is used for H2S flashing of the secondary H2S-rich methanol 10 to obtain H2S flash gas and H2S flash liquid 19; the CO2 washing section is used for third washing of the b stock of non-shift CO2-rich methanol 8-i-b and the CO2 flash gas to obtain washed CO2 flash gas 23, and to obtain third washing liquid mixed into the CO2 flash liquid 24; and the H2S washing section is used for second washing of the third stock of non-shift H2S-rich methanol 2-iii and the H2S flash gas to obtain washed H2S flash gas 18 and the third H2S-rich methanol 25.

[0103] According to the present application, as shown in the figure, Figure 1 As shown in the figure, the upper tower of 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; wherein the first flash section is used for first flashing of the CO2 flash liquid 24 to obtain semi-lean liquid methanol 13 and a first stock of CO2 product gas; the second flash section is used for second flashing of the second stock of semi-lean liquid methanol 13-ii to obtain second flash liquid and a second stock of CO2 product gas; and the third flash section is used for third flashing of the H2S flash liquid 19 to obtain the first H2S-rich methanol 20, and to obtain a sulfur-containing gas phase which is contacted with the second flash liquid through a rising hole and is subjected to fourth washing to obtain low-sulfur methanol 21 and a third stock of CO2 product gas; wherein the first stock of CO2 product gas, the second stock of CO2 product gas and the third stock of CO2 product gas are mixed to obtain the CO2 product gas 22.

[0104] According to the present application, as shown in the figure, Figure 1 As shown in the figure, the lower tower of the reabsorption tower T-5 is divided into a washing section and a gas stripping section from top to bottom, wherein the gas stripping section is used for contacting the first H2S-rich methanol 20, the low-sulfur methanol 21, the second H2S-rich methanol 16 and the third H2S-rich methanol 25 with nitrogen gas 26 respectively and subjecting them to gas stripping to obtain gas stripping gas and gas-stripped H2S-rich methanol 17; and the washing section is used for contacting the first stock of semi-lean liquid methanol 13-i with the gas stripping gas and subjecting them to first washing to obtain tail gas 15 and the second H2S-rich methanol 16.

[0105] According to the present application, preferably, as shown in the figure, Figure 1 As shown in the figure, a first cooler E-1 is arranged on the pipeline connecting the third purification section, the second CO2 absorption section and the CO2 washing section, which is used for dividing the first stock of non-shift CO2-rich methanol 8-i into the a stock of non-shift CO2-rich methanol 8-i-a and the b stock of non-shift CO2-rich methanol 8-i-b after first cooling.

[0106] According to the present application, preferably, as shown in the figure,Figure 1 As shown, in the direction of material flow, a pump P and a second cooler E-2 are arranged in sequence on the pipeline connecting the first CO2 absorption section and the second H2S absorption section, for pressurizing and second cooling the first primary CO2-rich methanol 9-i in sequence, and then carrying out the second H2S absorption.

[0107] According to the present application, preferably, as shown in the drawing, Figure 1 As shown, a third cooler E-3 is arranged on the pipeline connecting the second CO2 absorption section and the first CO2 absorption section, for third cooling the secondary CO2-rich methanol 12, and then carrying out the first CO2 absorption.

[0108] According to the present application, preferably, as shown in the drawing, Figure 1 As shown, a fourth cooler E-4 is arranged on the pipeline connecting the first CO2 absorption section and the CO2 flashing section, for fourth cooling the second primary CO2-rich methanol 9-ii, and then carrying out the CO2 flashing.

[0109] According to the present application, preferably, as shown in the drawing, Figure 1 As shown, a fifth cooler E-5 is arranged on the pipeline connecting the H2S flashing section and the third flashing section, for fifth cooling the H2S flashing liquid 19, and then carrying out the third flashing.

[0110] According to the present application, preferably, as shown in the drawing, Figure 1 As shown, a first heat exchanger Q-1 is arranged on the pipeline connecting the third flashing section and the stripping section, for first heat exchanging the first H2S-rich methanol 20, and then carrying out the stripping.

[0111] According to the present application, preferably, as shown in the drawing, Figure 1 As shown, a second heat exchanger Q-2 is arranged on the pipeline connecting the washing section and the stripping section, for second heat exchanging the second H2S-rich methanol 16, and then carrying out the stripping.

[0112] According to the present application, preferably, as shown in the drawing, Figure 1 As shown, a third heat exchanger Q-3 is arranged on the pipeline connecting the second flashing section and the stripping section, for third heat exchanging the low-sulfur methanol 21, and then carrying out the stripping.

[0113] The present application will be described in detail below through examples.

[0114] In the present application, without special circumstances, the synthesis gas and the non-shift gas are both derived from a coal slurry gasification device.

[0115] Example 1

[0116] The device is as shown in the drawing ​As shown, the device comprises: a non-reformed gas purification tower T-1, an H2S absorption tower T-2, a CO2 absorption tower T-3, a medium-pressure flash tower 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, and a fifth cooler E-5, a pump P, and a first heat exchanger Q-1, a second heat exchanger Q-2, and a third heat exchanger Q-3;

[0117] The method is performed in the above device, comprising:

[0118] The non-reformed gas 1 (molar content of H2S: 0.9-1.2%, molar content of CO2: 5-10%; temperature: -35 to -25℃, pressure: 5.5-6 MPa(G)) and the second non-reformed H2S-rich methanol 2-ii are contacted at a molar flow ratio of 165-175:1 and subjected to first purification, to obtain pre-purified non-reformed H2S-rich methanol 4 (molar content of H2S: 1.8-2.2%, molar content of CO2: 3-7%) and pre-desulfurized non-reformed gas; the above pre-desulfurized non-reformed gas and the second non-reformed CO2-rich methanol 8-ii are contacted and subjected to second purification, to obtain non-reformed H2S-rich methanol 2 (molar content of H2S: 1.4-1.8%, molar content of CO2: 4-9%; temperature: -30 to -25℃; pressure: 5.6-6 MPa(G)) and desulfurized non-reformed gas; the above desulfurized non-reformed gas and the first methanol-lean 3-i are contacted and subjected to third purification, to obtain non-reformed CO2-rich methanol 8 (molar content of H2S: 0.5-1 ppm, molar content of CO2: 2-6%; temperature: -42 to -38℃) and purified non-reformed gas 5 (molar content of H2S: ≤0.1 ppm, molar content of CO2: ≤20 ppm; temperature: -55 to -45℃, pressure: 5.5-5.9 MPa(G));

[0119] Wherein, the above non-reformed H2S-rich methanol 2 is divided into a first non-reformed H2S-rich methanol 2-i, a second non-reformed H2S-rich methanol 2-ii, and a third non-reformed H2S-rich methanol 2-iii at a molar flow ratio of 5-7:1:95-100; wherein, the above non-reformed CO2-rich methanol 8 is divided into a first non-reformed CO2-rich methanol 8-i-a, a second non-reformed CO2-rich methanol 8-i-b, and a second non-reformed CO2-rich methanol 8-ii at a molar flow ratio of 6-8:1:4-6; wherein, the first non-reformed CO2-rich methanol 8-i is cooled to -54 to -50℃ by the first cooler, to obtain the a first non-reformed CO2-rich methanol 8-i-a and the b first non-reformed CO2-rich methanol 8-i-b;

[0120] wherein the molar flow ratio of the second non-shifted H2S-rich methanol 8-ii and the non-shifted gas 1 is 1:1-2; the molar flow ratio of the first lean methanol 3-i and the non-shifted gas 1 is 2-3:1-2;

[0121] 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-shifted H2S-rich methanol 2-i are contacted and subjected to first H2S absorption at a molar flow ratio of 60-70:1 to obtain pre-desulfurized gas and 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 and the first first H2S-rich CO2 methanol 9-i (are successively pressurized to 5.6-6 MPa(G), second cooled to -46 to -43°C) are contacted and subjected to the second H2S absorption to obtain desulfurized gas 11 (molar content of H2S is 0.5-1 ppm, molar content of CO2 is 36-42%; temperature is -20 to -10°C; pressure is 5.35-5.55 MPa(G)) and second H2S-rich methanol 10 (molar content of H2S is 1.4-1.9%, molar content of CO2 is 34-40%; temperature is -10 to -6°C);

[0122] wherein the molar flow ratio of the first first H2S-rich CO2 methanol 9-i and the synthesis gas 6 is 1:1-3;

[0123] The above desulfurized gas 11 and the second H2S-rich CO2 methanol 12 (third cooled to -36 to -33°C) are contacted and subjected to first CO2 absorption at a molar flow ratio of 1:1-1.5 to obtain first H2S-rich CO2 methanol 9 (molar content of H2S is 0.1-0.5 ppm, molar content of CO2 is 25-30%, temperature is -7 to -2°C, pressure is 5.35-5.55 MPa(G)) and pre-purified gas; the above pre-purified gas, the a non-shifted H2S-rich CO2 methanol 8-i-a and the second lean methanol 3-ii are contacted and subjected to second CO2 absorption to obtain second H2S-rich CO2 methanol 12 and purified gas 14 (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));

[0124] wherein the molar flow ratio of the a non-shifted H2S-rich CO2 methanol 8-i-a and the purified gas 14 is 1:1-2; the molar flow ratio of the second lean methanol 3-ii and the purified gas 14 is 1-1.3:1;

[0125] wherein the first CO2-rich methanol 9 is divided into a first first CO2-rich methanol 9-i and a second first CO2-rich methanol 9-ii in a molar flow ratio of 1:1-3;

[0126] The second first CO2-rich methanol 9-ii is subjected to CO2 flashing (at a pressure of 1.6-2 MPa (G)) to obtain a CO2 flashing gas and a CO2 flashing liquid 24 (H2S molar content of 0.1-0.5 ppm, CO2 molar content of 24-28%, temperature of -38 to -34°C);

[0127] The second H2S-rich methanol 10 is subjected to H2S flashing (at a pressure of 1.6-2 MPa (G)) to obtain a H2S flashing gas and a H2S flashing liquid 19 (H2S molar content of 1.4-1.9%, CO2 molar content of 33-39%; temperature of -12 to -8°C);

[0128] The CO2 flashing liquid 24 is subjected to first flashing (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 15-20%, temperature of -62 to -58°C; pressure of 0.05-0.08 MPa (G)) and a first CO2 product gas; the second semi-lean liquid methanol 13-ii is subjected to second flashing (at a pressure of 0.06-0.09 MPa (G)) to obtain a second flashing liquid and a second CO2 product gas; the H2S flashing liquid 19 (cooled to -32 to -30°C by a fifth cooler) is subjected to third flashing (at a pressure of 0.12-0.16 MPa (G)) to obtain a first H2S-rich methanol 20 (H2S molar content of 1.4-1.9%, CO2 molar content of 22-27%; temperature of -68 to -63°C; pressure of 0.13-0.17 MPa (G)) and a sulfur-containing gas phase; wherein the second flashing liquid and the sulfur-containing gas phase are subjected to fourth washing to obtain a low-sulfur methanol 21 (H2S molar content of 0.4-0.6%, CO2 molar content of 16-21%; temperature of -58 to -53°C, pressure of 0.12-0.16 MPa (G)) and a third CO2 product gas;

[0129] wherein the first CO2 product gas, the second CO2 product gas and the third CO2 product gas 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));

[0130] The above semi-lean methanol 13 is divided into a first semi-lean methanol 13-i and a second semi-lean methanol 13-ii with a molar flow ratio of 1-3:1;

[0131] The above first H2S-rich methanol 20 (after first heat exchange, -40 to -38℃), low-sulfur methanol 21 (after third heat exchange, -40 to -38℃), second H2S-rich methanol 16 (after second heat exchange, -40 to -38℃) and third H2S-rich methanol 25 are respectively contacted with nitrogen 26 and subjected to gas stripping to obtain gas stripping gas and H2S-rich methanol 17 after gas stripping (molar content of H2S is 0.8-1.2%, molar content of CO2 is 2-3%; temperature is -50 to -45℃, pressure is 0.12-0.16 MPa(G));

[0132] The above first semi-lean methanol 13-i and gas stripping gas are contacted and subjected to first washing to obtain tail gas 15 (molar content of H2S is 0.5-1 ppm, molar content of CO2 is 84-88%; temperature is -65 to -60℃) and second H2S-rich methanol 16 (molar content of H2S is 0.4-0.8%, molar content of CO2 is 15-20%, pressure is 0.06-0.09 MPa(G));

[0133] The above third non-shift H2S-rich methanol and H2S flash gas are subjected to second washing to obtain third H2S-rich methanol 25 (molar content of H2S is 1.4-1.8%, molar content of CO2 is 8-12%; temperature is -22 to -18℃) and H2S flash gas 18 after washing (molar content of H2S is 1-1.4%, molar content of CO2 is 16-20%, molar content of CO is 58-62%, molar content of H2 is 18-22%; temperature is -35 to -25℃, pressure is 1.6-2 MPa(G));

[0134] The above b non-shift CO2-rich methanol 8-i-b and CO2 flash gas are contacted and subjected to third washing to obtain CO2 flash gas 23 after washing (molar content of H2S is 0.1-0.5 ppm, molar content of CO2 is 3-7%, molar content of CO is 23-27%, molar content of H2 is 68-72%; temperature is -60 to -50℃, pressure is 1.6-2 MPa(G)), and the third washing liquid obtained is mixed into the above CO2 flash liquid 24.

[0135] Comparative Example 1

[0136] Taking a hydrogen production device using coal water slurry gasification for example, the effective gas (H2+CO) entering the low-temperature methanol washing device is 230000 Nm 3 / h, under this benchmark, the main technical parameters of the lean-liquor-semi-lean liquor process (i.e., CN201110260570.0 discloses a low-temperature methanol washing process) are compared in Table 1.

[0137] Table 1

[0138]

[0139]

[0140] As can be seen from the results in Table 1, taking a hydrogen production device based on water-coal slurry gasification as an example, the multi-generation acid gas removal method provided by the water-coal slurry gasification device of Example 1, the lean methanol circulation amount is 88.9% of the lean methanol circulation amount in Comparative Example 1 (lean-liquor-semi-lean liquor process), the semi-lean liquor methanol circulation amount is 80% of the semi-lean liquor methanol circulation amount in Comparative Example 1 (lean-liquor-semi-lean liquor process), the amount of CO2-rich methanol used in the H2S absorption tower is 94.7% of the amount of CO2-rich methanol used in Comparative Example 1 (lean-liquor-semi-lean liquor process), and the cumulative external cold consumption is reduced by 500 KW / h, and the overall energy-saving effect is remarkable.

[0141] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for removing acidic gases from a multi-generation combined heat and power plant (CHP) system, characterized in that: The method includes: (1) The synthesis gas (6) from the coal-water slurry gasification unit is subjected to first H2S absorption and second H2S absorption in sequence 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 first CO2 absorption and second CO2 absorption in sequence to obtain first-stage CO2-rich methanol (9) divided into two streams, second-stage CO2-rich methanol (12) and purified gas (14); (2) The second primary CO2-rich methanol (9-ii) and the secondary H2S-rich methanol (10) are subjected to CO2 flash evaporation and H2S flash evaporation respectively to obtain CO2 flash liquid (24), CO2 flash vapor, H2S flash liquid (19) and H2S flash vapor; wherein, the CO2 flash liquid (24), the second semi-lean methanol (13-ii) and the H2S flash liquid (19) are subjected to first flash evaporation, second flash evaporation and third flash evaporation respectively to obtain semi-lean methanol (13) divided into two streams, low-sulfur methanol (21) and first H2S-rich methanol (20); (3) The first H2S-rich methanol (20), low-sulfur methanol (21), second H2S-rich methanol (16) and third H2S-rich methanol (25) are stripped by gas, and the stripped gas is washed with the first semi-lean methanol (13-i) to obtain the second H2S-rich methanol (16). Specifically, the non-conversion H2S-rich methanol (2) from the non-conversion gas purification process is divided into three streams, and the non-conversion CO2-rich methanol (8) is divided into two streams; the first stream of non-conversion H2S-rich methanol (2-i) and the second stream of non-conversion H2S-rich methanol (2-ii) are returned to the first H2S absorption and non-conversion gas purification process, respectively; the third stream of non-conversion H2S-rich methanol (2-iii) and H2S flash vapor undergo a second washing to obtain the third H2S-rich methanol (25); the first stream of non-conversion CO2-rich methanol (8-i) is divided into a stream of non-conversion CO2-rich methanol (8-ia) and a stream of non-conversion CO2-rich methanol (8-ib), respectively, and returned to the second CO2 absorption and undergo a third washing with the CO2 flash vapor; the second stream of non-conversion CO2-rich methanol (8-ii) is returned to the non-conversion gas purification process.

2. The method according to claim 1, wherein, In step (1), The non-conversion gas purification process includes: sequentially performing first purification, second purification and third purification on the non-conversion gas (1) from the coal-water slurry gasification unit to obtain pre-purified non-conversion H2S-rich methanol (4), non-conversion H2S-rich methanol (2), non-conversion CO2-rich methanol (8) and purified non-conversion gas (5). Preferably, the second non-conversion H2S-rich methanol (2-ii) is returned to the first purification; the second non-conversion CO2-rich methanol (8-ii) is returned to the second purification. More preferably, the non-conversion gas (1) and the second non-conversion H2S-rich methanol (2-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 (8-ii) are contacted and subjected to the second purification to obtain the non-conversion H2S-rich methanol (2) and the desulfurized non-conversion gas; the desulfurized non-conversion gas and the first lean methanol (3-i) are contacted and subjected to the third purification to obtain the non-conversion CO2-rich methanol (8) and the purified non-conversion gas (5); Preferably, the molar flow ratio of the non-conversion gas (1) and the second non-conversion H2S-rich methanol (2-ii) is 165-175:1; Preferably, the non-conversion H2S-rich methanol (2) has a molar content of 1.4-1.8% for H2S and a molar content of 4-9% for CO2; the temperature is -30 to -25°C; and the pressure is 5.6-6 MPa(G). Preferably, the molar flow ratio of the first non-conversion H2S-rich methanol (2-i), the second non-conversion H2S-rich methanol (2-ii), and the third non-conversion H2S-rich methanol (2-iii) is 5-7:1:95-100. Preferably, the non-conversion CO2-rich methanol (8) has a molar content of H2S of 0.5-1 ppm and a molar content of CO2 of 2-6%; and a temperature of -42 to -38°C. Preferably, the first non-conversion CO2-rich methanol (8-i) is cooled to -54 to -50°C and divided into the a-strand non-conversion CO2-rich methanol (8-ia) and the b-strand non-conversion CO2-rich methanol (8-ib). Preferably, the molar flow ratio of the a-strand non-conversion CO2-rich methanol (8-ia), the b-strand non-conversion CO2-rich methanol (8-ib), and the second non-conversion CO2-rich methanol (8-ii) is 6-8:1:4-6; 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 5.5-5.9MPa(G).

3. The method according to claim 1 or 2, wherein, In step (1), The synthesis gas (6) is contacted with the first non-conversion H2S-rich methanol (2-i) and the first H2S absorption is performed to obtain the first-stage H2S-rich methanol (7) and pre-desulfurized gas; the pre-desulfurized gas is contacted with the first-stage CO2-rich methanol (9-i) and the second H2S absorption is performed to obtain the desulfurized gas (11) and the second-stage H2S-rich methanol (10); Preferably, the molar content of H2S in the secondary H2S-rich methanol (10) is 1.4-1.9%, and the molar content of CO2 is 34-40%; the temperature is -10 to -6℃. Preferably, the desulfurization gas (11) has a molar content of H2S of 0.5-1 ppm and a molar content of CO2 of 36-42%; a temperature of -20 to -10°C; and a pressure of 5.35-5.55 MPa(G). Preferably, the first primary CO2-rich methanol (9-i) is pressurized to 5.6-6 MPa (G) and cooled to -46 to -43°C in sequence according to the material flow direction to carry out the second H2S absorption.

4. The method according to any one of claims 1-3, wherein, In step (1), The desulfurized gas (11) and the secondary CO2-rich methanol (12) are contacted and the first CO2 absorption is performed to obtain the primary CO2-rich methanol (9) and the pre-purified gas; The pre-purified gas, a non-conversion CO2-rich methanol (8-ia) and a second lean methanol (3-ii) are contacted and the second CO2 absorption is performed to obtain the secondary CO2-rich methanol (12) and purified gas (14). Preferably, the secondary CO2-rich methanol (12) is cooled to -36 to -33°C in a third cooling process for the first CO2 absorption; 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 25-30%, the temperature is -7 to -2℃, and the pressure is 5.35-5.55 MPa (G); Preferably, the molar flow ratio of the first primary CO2-rich methanol (9-i) and the second primary CO2-rich methanol (9-ii) is 1:1-3.

5. The method according to any one of claims 1-4, wherein, In step (2), The second primary CO2-rich methanol (9-ii) is cooled to -36 to -33°C in a fourth cooling process to perform CO2 flash evaporation. Preferably, the CO2 flash liquid (24) has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 24-28%, and a temperature of -38 to -34°C; Preferably, the pressures for CO2 flash evaporation and H2S flash evaporation are 1.6-2 MPa(G); Preferably, the H2S flash liquid (19) has a molar content of 1.4-1.9% for H2S and a molar content of 33-39% for CO2; and the temperature is -12 to -8°C. Preferably, the CO2 flash liquid (24) is subjected to the first flash evaporation to obtain the semi-lean methanol (13) and the first CO2 product gas; the second semi-lean methanol (13-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 (20) and the sulfur-containing gas phase; wherein the second flash liquid and the sulfur-containing gas phase are contacted and subjected to a fourth wash to obtain low-sulfur methanol (21) and the 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 H2S flash liquid (19) is cooled to -32 to -30°C in the fifth stage before the third flash evaporation is performed; Preferably, the semi-lean methanol (13) has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 15-20%, a temperature of -62 to -58°C, and a pressure of 0.05-0.08 MPa(G). Preferably, the molar flow ratio of the first semi-lean methanol (13-i) and the second semi-lean methanol (13-ii) is 1-3:1; Preferably, the low-sulfur methanol (21) has a molar content of H2S of 0.4-0.6% and a molar content of CO2 of 16-21%; the temperature is -58 to -53°C and the pressure is 0.12-0.16 MPa(G); Preferably, the first H2S-rich methanol (20) has a molar content of 1.4-1.9% for H2S and a molar content of 22-27% for CO2; a temperature of -68 to -63°C; and a pressure of 0.13-0.17 MPa(G). 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).

6. The method according to any one of claims 1-5, wherein, In step (3), The first H2S-rich methanol (20), low-sulfur methanol (21), second H2S-rich methanol (16) and third H2S-rich methanol (25) are respectively contacted with nitrogen (26) and subjected to gas stripping to obtain stripped gas and stripped H2S-rich methanol (17). Preferably, the first H2S-rich methanol (20) is subjected to a first heat exchange to a temperature of -40 to -38°C for the gas stripping process; Preferably, the second H2S-rich methanol (16) is subjected to a second heat exchange to a temperature of -40 to -38°C for the gas stripping process; Preferably, the low-sulfur methanol (21) is subjected to a third heat exchange to a temperature of -40 to -38°C for the gas stripping process; Preferably, the first washing process includes: washing the stripped gas with a first semi-lean methanol (13-i) to obtain the second H2S-rich methanol (16) and tail gas (15); Preferably, the second H2S-rich methanol (16) has a molar content of 0.4-0.8% for H2S, a molar content of 15-20% for CO2, and a pressure of 0.06-0.09 MPa (G).

7. The method according to any one of claims 1-6, wherein, The second washing process includes: subjecting the third non-conversion H2S-rich methanol (2-iii) and H2S flash vapor to a second washing to obtain the third H2S-rich methanol (25) and washed H2S flash vapor (18); Preferably, the molar content of H2S in the third H2S-rich methanol (25) is 1.4-1.8%, the molar content of CO2 is 8-12%, and the temperature is -22 to -18°C; Preferably, the third washing process includes: contacting the b strands of non-conversion CO2-rich methanol (8-ib) and CO2 flash vapor and performing the third washing to obtain washed CO2 flash vapor (23), and mixing the obtained third washing liquid into the CO2 flash liquid (24).

8. An energy-saving multi-generation acid gas removal device for use with a coal-water slurry gasification unit, 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-conversion gas purification tower (T-1) is used to sequentially purify the non-conversion gas (1) from the coal-water slurry gasification unit through the first purification, the second purification and the third purification to obtain pre-purified non-conversion H2S-rich methanol (4), non-conversion H2S-rich methanol (2) divided into three streams, non-conversion CO2-rich methanol (8) divided into two streams and purified non-conversion gas (5). The H2S absorption tower (T-2) is used to sequentially absorb the syngas (6) from the coal-water slurry gasification unit through a first H2S absorption and a second H2S absorption to obtain primary H2S-rich methanol (7), secondary H2S-rich methanol (10), and desulfurized gas (11); the CO2 absorption tower (T-3) is used to sequentially absorb the desulfurized gas (11) through a first CO2 absorption and a second CO2 absorption to obtain primary CO2-rich methanol (9) divided into two streams, secondary CO2-rich methanol (12), and purified gas (14); The medium-pressure flash tower (T-4) is divided into a CO2 washing section, a CO2 flash section, an H2S washing section, and an H2S flash section from top to bottom. The CO2 flash section is used to flash the second primary CO2-rich methanol (9-ii) to obtain CO2 flash vapor and CO2 flash liquid (24). The H2S flash section is used to flash the secondary H2S-rich methanol (10) to obtain H2S flash vapor and H2S flash liquid (19). The reabsorption tower (T-5) includes an upper tower and a lower tower. The upper tower is divided into a first flash section, a second flash section and a third flash section from top to bottom. These sections are used to perform the first flash, second flash and third flash of the CO2 flash liquid (24), the second semi-lean methanol (13-ii) and the H2S flash liquid (19) respectively, to obtain two streams of semi-lean methanol (13), low-sulfur methanol (21) and first H2S-rich methanol (20). The lower tower is divided into a washing section and a stripping section from top to bottom. The stripping section is used to strip the first H2S-rich methanol (20), low-sulfur methanol (21), second H2S-rich methanol (16) and third H2S-rich methanol (25) respectively. The stripped gas is sent to the washing section through the gas riser and is washed with the first semi-lean methanol (13-i) to obtain the second H2S-rich methanol (16). The first non-conversion H2S-rich methanol (2-i) and the second non-conversion H2S-rich methanol (2-ii) are returned to the first H2S absorption section and the non-conversion gas purification tower (T-1), respectively. The third non-conversion H2S-rich methanol (2-iii) is sent to the H2S washing section for a second washing with the H2S flash vapor to obtain the third H2S-rich methanol (25). The first non-conversion CO2-rich methanol (8-i) is divided into a non-conversion CO2-rich methanol (8-ia) and b non-conversion CO2-rich methanol (8-ib), which are returned to the second CO2 absorption section and sent to the CO2 washing section for a third washing with the CO2 flash vapor. The second non-conversion CO2-rich methanol (8-ii) is returned to the non-conversion gas purification tower (T-1).

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 (2-ii) returns to the first purification section; the second non-converted CO2-rich methanol (8-ii) returns to the second purification section. Preferably, a first cooler (E-1) is provided on the pipeline connecting the third purification section, the second CO2 absorption section and the CO2 washing section, for dividing the first non-conversion CO2-rich methanol (8-i) into the a-stream non-conversion CO2-rich methanol (8-ia) and the b-stream non-conversion CO2-rich methanol (8-ib) after the first cooling. Preferably, a pump (P) and a second cooler (E-2) are sequentially installed on the pipeline connecting the first CO2 absorption section and the second H2S absorption section according to the material flow direction. This is used to pressurize and cool the first stream of primary CO2-rich methanol (9-i) sequentially before absorbing the second H2S. Preferably, a third cooler (E-3) is provided on the pipe connecting the second CO2 absorption section and the first CO2 absorption section according to the material flow direction, for the second CO2-rich methanol (12) to be cooled in the third stage before the first CO2 absorption is performed; Preferably, a fourth cooler (E-4) is provided on the pipeline connecting the first CO2 absorption section and the CO2 flash evaporation section, for flash evaporation of the second primary CO2-rich methanol (9-ii) after the second stream is cooled by the fourth cooler; Preferably, a fifth cooler (E-5) is provided on the pipeline connecting the H2S flash section and the third flash section, which is used to cool the H2S flash liquid (19) in the fifth stage before performing the third flash evaporation.

10. The apparatus according to claim 9, wherein, A first heat exchanger (Q-1) is installed on the pipeline connecting the third flash section and the stripping section, which is used to strip the first H2S-rich methanol (20) after the first heat exchange. Preferably, a second heat exchanger (Q-2) is provided on the pipeline connecting the washing section and the stripping section, for stripping the second H2S-rich methanol (16) after passing through the second heat exchanger; Preferably, a third heat exchanger (Q-3) is provided on the pipeline connecting the second flash section and the stripping section, for stripping the low-sulfur methanol (21) after the third heat exchange.

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