Low-temperature methanol washing method and device matched with pulverized coal gasification device

Abstract

The invention relates to the technical field of low-temperature methanol washing, in particular to a low-temperature methanol washing method matched with a pulverized coal gasification device and a low-temperature methanol washing device matched with the pulverized coal gasification device. The method has the characteristics of scientific and efficient arrangement of a tail gas washing process, no mutual pollution in medium-pressure flash evaporation and classified flash evaporation, small graded desorption compression power of CO2 product gas, high use efficiency of methanol in non-conversion gas washing, low comprehensive energy consumption and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-temperature methanol washing, in particular to a low-temperature methanol washing method matched with a pulverized coal gasification device and a low-temperature methanol washing device matched with the pulverized coal gasification device. BACKGROUND

[0002] In the low-temperature methanol washing process, the H2S-rich methanol needs to be recycled by heat regeneration, which is the main energy consumption source of the low-temperature methanol washing. In addition, the CO2-rich methanol and the H2S-rich methanol are flashed in the medium-pressure flash tower to recover the effective gas, and a large amount of CO2 gas is also flashed out. Therefore, it is also very important to select an absorption medium to absorb the CO2 gas.

[0003] Specifically, first, the medium-pressure flash process needs to be optimized, so that the CO2 flash gas generated by the CO2 medium-pressure flashing is not polluted by the H2S-containing flash gas generated by the H2S medium-pressure flashing; second, the secondary absorption medium after the flashing of the H2S-rich methanol is reasonably selected; third, the process flow of the reabsorption tower and the desorption pressure are optimized, so that the pressure of the flashed CO2 product gas is as high as possible, the compression power of the subsequent process is reduced, the low-H2S methanol is fully utilized, and the total amount of the H2S-rich methanol for heat regeneration is reduced; fourth, the characteristics of the non-shift CO2-rich methanol solution, which does not contain H2S gas and has a low CO2 content, and the characteristics of the non-shift H2S-rich methanol, which has a low CO2 content and a relatively high CO gas content, are utilized, and the two kinds of rich methanol are reasonably reused.

[0004] CN201110260570.0 discloses a low-temperature methanol washing process. The CO2-rich methanol is flashed in the upper section of the medium-pressure flash tower, the flashed CO2 gas is transported to the lower section of the medium-pressure flash tower through a pipeline, and is washed and absorbed by the H2S-rich methanol sent from the reabsorption tower. As a result, the CO2 gas in the CO2-rich methanol is transferred to the H2S-rich methanol, and the CO2 gas is also polluted. In the CO2 flashing section of the reabsorption tower, the flashing stage number and the pressure need to be optimized. The CO2-rich methanol is directly mixed with the H2S-rich methanol while washing the H2S-rich methanol flash gas, and is deeply polluted by the H2S-rich methanol. The low-concentration H2S methanol after mixing is also not fully utilized. The tail gas washing process of the reabsorption tower is not reasonable enough. Different H2S contents of the methanol are not selectively set for washing according to the H2S content in the tail gas, so as to reduce the heat regeneration energy consumption of the whole low-temperature methanol washing. SUMMARY

[0005] The present application aims to overcome the above technical problems, and provides a rectisol method matched with a pulverized coal gasification device and a rectisol device matched with the pulverized coal gasification device, which has the advantages of scientific and efficient tail gas washing process, non-pollution between medium pressure flash evaporation classification flash evaporation, small compression power of CO2 product gas fractional desorption, high methanol use efficiency of non-shift gas washing, and low comprehensive energy consumption.

[0006] To achieve the above-mentioned purpose, the present application provides a rectisol method matched with a pulverized coal gasification device, which comprises:

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

[0008] Among them, the non-shift H2S-rich methanol and the non-shift CO2-rich methanol from the non-shift gas purification process are divided into three groups and two groups respectively; the first group of non-shift H2S-rich methanol is returned to the primary H2S absorption; the first group of non-shift CO2-rich methanol and the second group of non-shift CO2-rich methanol are returned to the secondary H2S absorption and the primary purification respectively;

[0009] (2) performing CO2 flash evaporation on the second group of primary CO2-rich methanol to obtain CO2 flash evaporation gas and two groups of CO2 flash evaporation liquid; performing H2S flash evaporation on the secondary H2S-rich methanol to obtain H2S flash evaporation gas and H2S flash evaporation liquid;

[0010] (3) performing first flash evaporation, second flash evaporation and third flash evaporation on the first group of CO2 flash evaporation liquid, the second group of CO2 flash evaporation liquid and the H2S flash evaporation liquid respectively to obtain primary semi-lean liquid methanol, low H2S methanol, first H2S-rich methanol and first CO2 product gas; performing fourth flash evaporation on the primary semi-lean liquid methanol to obtain two groups of secondary semi-lean liquid methanol, and the second group of secondary semi-lean liquid methanol is returned to the secondary CO2 absorption;

[0011] Among them, the second group of non-shift H2S-rich methanol and the low H2S methanol are respectively subjected to first washing with the CO2 flash evaporation gas to obtain low-sulfur carbon-rich methanol which is returned to the secondary H2S absorption; the third group of non-shift H2S-rich methanol and the H2S flash evaporation gas are subjected to second washing to obtain second H2S-rich methanol; the first H2S-rich methanol, the second H2S-rich methanol and the third H2S-rich methanol are respectively subjected to gas stripping, and the gas stripping gas and the first group of secondary semi-lean liquid methanol are subjected to third washing to obtain the third H2S-rich methanol.

[0012] The second aspect of the present application provides a low-temperature methanol washing device matched with a pulverized coal gasification device, the device comprising: a connected non-shifted gas washing tower, an H2S absorption tower, a CO2 absorption tower, a medium-pressure flash tower, a reabsorption tower and an H2S concentration tower;

[0013] The non-shifted gas washing tower is divided into a first purification section and a second purification section from bottom to top, and is used for sequentially performing primary purification and secondary purification on the non-shifted gas to obtain three streams of non-shifted H2S-rich methanol and two streams of non-shifted CO2-rich methanol;

[0014] The H2S absorption tower is divided into a first H2S absorption section and a second H2S absorption section from bottom to top, and is used for sequentially performing primary H2S absorption and secondary H2S absorption on the synthesis gas to obtain primary H2S-rich methanol, secondary H2S-rich methanol and desulfurized gas;

[0015] The CO2 absorption tower is divided into a first CO2 absorption section and a second CO2 absorption section from bottom to top, and is used for sequentially performing primary CO2 absorption and secondary CO2 absorption on the desulfurized gas to obtain two streams of primary CO2-rich methanol, secondary CO2-rich methanol and purified gas;

[0016] The medium-pressure flash tower is divided into a first washing section, a CO2 flashing section, a second washing section and an H2S flashing section from top to bottom; the CO2 flashing section is used for performing CO2 flashing on the second stream of primary CO2-rich methanol to obtain two streams of CO2 flashing gas and CO2 flashing liquid; and the H2S flashing section is used for performing H2S flashing on the secondary H2S-rich methanol to obtain H2S flashing gas and H2S flashing liquid;

[0017] The reabsorption tower is divided into a first flashing section, a second flashing section and a third flashing section from top to bottom, and is respectively used for performing first flashing, second flashing and third flashing on the first stream of CO2 flashing liquid, the second stream of CO2 flashing liquid and the H2S flashing liquid to obtain primary semi-lean liquid methanol, low-H2S methanol, first H2S-rich methanol and first CO2 product gas;

[0018] The first stream of non-shifted H2S-rich methanol is returned to the first H2S absorption section; the first stream of non-shifted CO2-rich methanol and the second stream of non-shifted CO2-rich methanol are respectively returned to the second H2S absorption section and the first purification section;

[0019] The first washing section is used for performing first washing on the second stream of non-shifted H2S-rich methanol, the low-H2S methanol and the CO2 flashing gas to obtain low-sulfur carbon-rich methanol which is returned to the second H2S absorption section; and the second washing section is used for performing second washing on the third stream of non-shifted H2S-rich methanol and the H2S flashing gas to obtain second H2S-rich methanol;

[0020] The H2S concentration tower is divided into a flash evaporation part, a washing part and a gas stripping part from top to bottom, the flash evaporation part is used for carrying out fourth flash evaporation on the first-stage semi-lean liquid methanol to obtain two groups of second-stage semi-lean liquid methanol; the gas stripping part is used for carrying out gas stripping on the first H2S-rich methanol, the second H2S-rich methanol and the third H2S-rich methanol respectively, and the obtained gas stripping gas is sent to the washing part through a rising hole to carry out third washing on the first group of second-stage semi-lean liquid methanol to obtain the third H2S-rich methanol.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] (1) The present application adopts a three-stage tail gas washing technology, according to the different H2S content in the tail gas, three groups of methanol with different H2S content are selectively set, and the washing is carried out from high to low, so that the least second-stage semi-lean liquid methanol is used under the premise of ensuring that the tail gas emission meets the standard, thereby reducing the heat regeneration energy consumption of the whole device;

[0023] (2) The present application adopts a two-stage desorption technology of CO2 flash evaporation liquid, the first CO2 product gas desorbed is directly sent to the second stage of the CO2 product gas compressor, thereby reducing the power consumption of the compressor;

[0024] (3) The present application uses classified medium-pressure flash evaporation and classified washing technology, realizes the separate flash evaporation and separate washing of the second group of first-stage CO2-rich methanol and the second-stage H2S-rich methanol, avoids the technical difficulty of transferring CO2 flash evaporation gas to H2S flash evaporation liquid, and is beneficial to reducing the energy consumption of the device;

[0025] (4) The present application uses low-sulfur carbon-rich methanol to absorb H2S from synthesis gas, thereby saving the amount of the first group of first-stage CO2-rich methanol and reducing the energy consumption of the device;

[0026] (5) The present application optimizes the reabsorption process, realizes the absorption of the second flash evaporation liquid of the second group of CO2 flash evaporation liquid on the sulfur-containing gas phase generated by the third flash evaporation of the H2S flash evaporation liquid, and returns the obtained low-H2S methanol to wash the CO2 flash evaporation gas, thereby reducing the amount of the second group of non-shift H2S-rich methanol. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The present application provides a structure schematic diagram of a low-temperature methanol washing device matched with a pulverized coal gasification device.

[0028] REFERENCE SIGNS

[0029] T-1, non-shift gas washing tower; T-2, H2S absorption tower; T-3, CO2 absorption tower; T-4, medium-pressure flash evaporation tower; T-5, reabsorption tower; T-6, H2S concentration tower;

[0030] 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; P-4, fourth pump; Q, heat exchanger;

[0031] 1, non-shifted gas; 2, non-shifted H2S-rich methanol; 2-i, first stream of non-shifted H2S-rich methanol; 2-ii, second stream of non-shifted H2S-rich methanol; 2-iii, third stream of non-shifted H2S-rich methanol; 3, lean methanol; 3-i, first stream of lean methanol; 3-ii, second stream of lean methanol; 4, second CO2product gas; 5, purified non-shifted gas; 6, synthesis gas; 7, primary H2S-rich methanol; 8, non-shifted CO2-rich methanol; 8-i, first stream of non-shifted CO2-rich methanol; 8-ii, second stream of non-shifted CO2-rich methanol; 9, primary CO2-rich methanol; 9-i, first stream of primary CO2-rich methanol; 9-ii, second stream of primary CO2-rich methanol; 10, secondary H2S-rich methanol; 11, sweetened gas; 12, secondary CO2-rich methanol; 13, primary semi-lean liquid methanol; 14, purified gas; 15, low-sulfur carbon-rich methanol; 16, second H2S-rich methanol; 17, CO2flash liquid; 17-i, first stream of CO2flash liquid; 17-ii, second stream of CO2flash liquid; 18, H2S flash gas after washing; 19, H2S flash liquid; 20, low-H2S methanol; 21, first H2S-rich methanol; 22, first CO2product gas; 23, CO2flash gas after washing; 24, third H2S-rich methanol; 25, nitrogen gas; 26, secondary semi-lean liquid methanol; 26-i, first stream of secondary semi-lean liquid methanol; 26-ii, second stream of secondary semi-lean liquid methanol; 27, tail gas; 28, H2S-rich methanol after stripping. DETAILED DESCRIPTION

[0032] 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 can vary depending on desired properties sought to be obtained by the compositions and methods disclosed herein. For example, the ranges and values can vary without departing from the scope of the present disclosure. The endpoints of the ranges and values are provided as a separate point for the convenience of the reader. The ranges and values are approximate values that can vary depending on desired properties sought to be obtained by the compositions and methods disclosed herein.

[0033] In the present disclosure, "first", "second", "third", "fourth", "fifth" and "sixth" do not indicate any sequential order or define the respective materials or steps, but are used only to distinguish or indicate that this is not the same step or material.

[0034] In the present application, unless otherwise specified, the "top" of the container refers to the height of 0-10% from top to bottom of the container; the "upper part" of the container refers to the height of 10-40% from top to bottom of the container; the "middle part" of the container refers to the height of 40-60% from top to bottom of the container; the "lower part" of the container refers to the height of 60-90% from top to bottom of the container; and the "bottom" of the container refers to the height of 90-100% from top to bottom of the container.

[0035] The first aspect of the present application provides a method for supporting a low-temperature methanol washing device of a pulverized coal gasification device, the method comprising:

[0036] (1) sequentially performing primary H2S absorption and secondary H2S absorption on the synthesis gas derived from the pulverized coal gasification device to obtain primary H2S-rich methanol, secondary H2S-rich methanol, and desulfurized gas; sequentially performing primary CO2 absorption and secondary CO2 absorption on the desulfurized gas to obtain two streams of primary CO2-rich methanol, secondary CO2-rich methanol, and purified gas;

[0037] Among them, the non-shift H2S-rich methanol and the non-shift CO2-rich methanol derived from the non-shift gas purification process are divided into three streams and two streams, respectively; wherein the first stream of non-shift H2S-rich methanol is returned to the primary H2S absorption; the first stream of non-shift CO2-rich methanol and the second stream of non-shift CO2-rich methanol are returned to the secondary H2S absorption and the primary purification, respectively;

[0038] (2) performing CO2 flashing on the second stream of primary CO2-rich methanol to obtain two streams of CO2 flashing gas and CO2 flashing liquid; performing H2S flashing on the secondary H2S-rich methanol to obtain H2S flashing gas and H2S flashing liquid;

[0039] (3) performing first flashing, second flashing, and third flashing on the first stream of CO2 flashing liquid, the second stream of CO2 flashing liquid, and the H2S flashing liquid, respectively, to obtain primary semi-lean liquid methanol, low-H2S methanol, first H2S-rich methanol, and first CO2 product gas; performing fourth flashing on the primary semi-lean liquid methanol to obtain two streams of secondary semi-lean liquid methanol, and the second stream of secondary semi-lean liquid methanol is returned to the secondary CO2 absorption;

[0040] Among them, the second stream of non-shift H2S-rich methanol and the low-H2S methanol are respectively subjected to first washing with the CO2 flashing gas to obtain low-sulfur carbon-rich methanol, which is returned to the secondary H2S absorption; the third stream of non-shift H2S-rich methanol and the H2S flashing gas are subjected to second washing to obtain second H2S-rich methanol; the first H2S-rich methanol, the second H2S-rich methanol, and the third H2S-rich methanol are respectively subjected to gas stripping, and the gas stripping gas and the first stream of secondary semi-lean liquid methanol are subjected to third washing to obtain the third H2S-rich methanol.

[0041] In the present application, the syngas and the non-shift gas are both derived from a pulverized coal gasification device, and the syngas is prepared from the non-shift gas by a shift process.

[0042] In some embodiments of the present application, preferably, the non-shift gas purification process comprises sequentially subjecting the non-shift gas derived from the pulverized coal gasification device to primary purification and secondary purification to obtain non-shift H2S-rich methanol, non-shift CO2-rich methanol and purified non-shift gas.

[0043] In the present application, preferably, the molar content of H2S in the non-shift gas is 0.4-0.6%, the molar content of CO2 is 5-10%, the temperature is -35 to -25℃, and the pressure is 3.5-3.6 MPa (G).

[0044] In the present application, the primary purification aims to remove HCN, NH3 and other impurities, H2S and a small amount of CO2 in the non-shift gas, and the secondary purification aims to further remove CO2 in the non-shift gas.

[0045] In some embodiments of the present application, preferably, the non-shift gas and the second stream of non-shift CO2-rich methanol are subjected to the primary purification to obtain the non-shift H2S-rich methanol and desulfurized non-shift gas, and the desulfurized non-shift gas and the first stream of methanol-lean are subjected to the secondary purification to obtain the non-shift CO2-rich methanol and the purified non-shift gas.

[0046] In the present application, preferably, the molar flow ratio of the non-shift gas to the second stream of non-shift CO2-rich methanol is 1.3-1.5:1.

[0047] In some embodiments of the present application, preferably, the molar content of H2S in the non-shift H2S-rich methanol is 0.5-0.9%, the molar content of CO2 is 3-7%, the temperature is -33 to -28℃, and the pressure is 3.5-3.55 MPa (G).

[0048] In the present application, the non-shift H2S-rich methanol is divided into three streams, the first stream is subjected to primary H2S absorption, the second stream is subjected to first washing, and the third stream is subjected to second washing. Further preferably, the molar flow ratio of the first stream of non-shift H2S-rich methanol, the second stream of non-shift H2S-rich methanol and the third stream of non-shift H2S-rich methanol is 1:1-2:3-5.

[0049] 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, the molar content of CO2 is 4-7%, and the temperature is -40 to -33℃.

[0050] In the present application, the non-shifted CO2-rich methanol is divided into two streams, the first stream is subjected to secondary H2S absorption, and the second stream is subjected to primary purification. Further preferably, the molar flow ratio of the first stream of non-shifted CO2-rich methanol and the second stream of non-shifted CO2-rich methanol is 1:1-1.1.

[0051] In the present application, preferably, the molar flow ratio of the first stream of methanol-lean and non-shifted gas is 1.5-2:1.

[0052] In some embodiments of the present application, preferably, the molar content of H2S in the methanol-lean is 0%, and the molar content of CO2 is 0%. In the present application, the methanol-lean is selected from subsequent processes. In the present application, without special circumstances, the methanol-lean is divided into a first stream of methanol-lean and a second stream of methanol-lean; the present application does not limit the molar flow ratio of the first stream of methanol-lean and the second stream of methanol-lean.

[0053] In the present application, preferably, the molar content of H2S in the purified non-shifted gas is ≤0.1 ppm, the molar content of CO2 is ≤20 ppm, the temperature is -55 to -45℃, and the pressure is 3.4-3.5 MPa(G).

[0054] In the present application, the primary H2S absorption aims to remove impurities such as HCN, NH3, and a small amount of H2S, CO2 in the synthesis gas, and the secondary H2S absorption aims to further remove H2S, CO2 in the synthesis gas.

[0055] In some embodiments of the present application, preferably, the molar content of H2S in the synthesis gas is 0.3-0.35%, the molar content of CO2 is 40-50%, the temperature is -25 to -15℃, and the pressure is 3.12-3.15 MPa(G).

[0056] In some embodiments of the present application, preferably, the synthesis gas and the first stream of non-shifted H2S-rich methanol are subjected to the primary H2S absorption to obtain the primary H2S-rich methanol and pre-desulfurization gas; the pre-desulfurization gas, low-sulfur carbon-rich methanol, the first stream of non-shifted CO2-rich methanol, and the first stream of primary CO2-rich methanol are subjected to the secondary H2S absorption to obtain the secondary H2S-rich methanol and desulfurization gas.

[0057] In the present application, preferably, the molar flow ratio of the synthesis gas and the first stream of non-shifted H2S-rich methanol is 40-50:1; further preferably, the molar content of H2S in the primary H2S-rich methanol is 0.6-0.8%, the molar content of CO2 is 30-36%, the temperature is -25 to -15℃, and it is sent to subsequent processes for treatment.

[0058] In the present application, preferably, the molar flow ratio of the low-sulfur carbon-rich methanol and the synthesis gas is 1:7-9; the molar flow ratio of the first non-shifted CO2-rich methanol and the synthesis gas is 1:6-7; and the molar flow ratio of the first primary CO2-rich methanol and the synthesis gas is 1-3:6-7.

[0059] In some embodiments of the present application, preferably, the molar content of H2S in the secondary H2S-rich methanol is 0.4-0.6%, the molar content of CO2 is 27-31%, and the temperature is -20 to -10°C.

[0060] In some embodiments of the present application, preferably, the first primary CO2-rich methanol is sequentially subjected to first pressurization to 3.6-4 MPa (G) and first cooling to -46 to -43°C in the order of material flow direction, and then subjected to the secondary H2S absorption.

[0061] In some embodiments of the present application, preferably, the low-sulfur carbon-rich methanol is subjected to second pressurization to 3.6-4 MPa (G) and then subjected to the secondary H2S absorption.

[0062] In some embodiments of the present application, preferably, the desulfurized gas and the secondary CO2-rich methanol are subjected to the primary CO2 absorption to obtain the primary CO2-rich methanol and pre-purified gas; and the pre-purified gas, the second secondary semi-lean liquid methanol, and the second lean methanol are subjected to the secondary CO2 absorption to obtain the secondary CO2-rich methanol and purified gas.

[0063] In the present application, the primary CO2 absorption and the secondary CO2 absorption are intended to further remove CO2 in the desulfurized gas. Preferably, the molar flow ratio of the desulfurized gas and the secondary CO2-rich methanol is 1:1.5-2.5; the molar flow ratio of the purified gas and the second secondary semi-lean liquid methanol is 1:1.1-1.3; and the molar flow ratio of the purified gas and the second lean methanol is 1:1.5-1.7.

[0064] In some embodiments of the present application, preferably, the molar content of H2S in the primary CO2-rich methanol is 0.1-0.5 ppm, the molar content of CO2 is 21-26%, the temperature is -24 to -18°C, and the pressure is 3.05-3.09 MPa (G).

[0065] In some embodiments of the present application, further preferably, the molar flow ratio of the first primary CO2-rich methanol and the second primary CO2-rich methanol is 1:4-5.

[0066] In some embodiments of the present application, preferably, the secondary CO2-rich methanol is subjected to second cooling to -36 to -33°C and then subjected to the primary CO2 absorption.

[0067] In some embodiments of the present application, preferably, the second stream of the secondary semi-lean liquid methanol is subjected to a third pressurization to 3.6-4 MPa (G) before the secondary CO2 absorption.

[0068] In some embodiments of the present application, preferably, the purified gas has a H2S molar content of ≤0.1 ppm and a CO2 molar content of 2-3%, a temperature of -48 to -44℃, and a pressure of 3-3.05 MPa (G).

[0069] In the present application, the process of CO2 flashing comprises: subjecting the second stream of the primary CO2-rich methanol to CO2 flashing to obtain a CO2 flashing gas and a CO2 flashing liquid; wherein the CO2 flashing liquid is divided into two streams and subjected to a first flashing and a second flashing, respectively.

[0070] In some embodiments of the present application, preferably, the CO2 flashing liquid has a H2S molar content of 0.1-0.5 ppm, a CO2 molar content of 15-20%, and a temperature of -26 to -21℃; further preferably, the first stream of the CO2 flashing liquid and the second stream of the CO2 flashing liquid have a molar flow ratio of 18-22:1.

[0071] In the present application, the process of H2S flashing comprises: subjecting the secondary H2S-rich methanol to H2S flashing to obtain a H2S flashing gas and a H2S flashing liquid; wherein the H2S flashing liquid is subjected to a third flashing.

[0072] In some embodiments of the present application, preferably, the H2S flashing liquid has a H2S molar content of 0.35-0.55%, a CO2 molar content of 26.5-30.5%, and a temperature of -40 to -33℃.

[0073] In some embodiments of the present application, preferably, the first stream of the CO2 flashing liquid is subjected to the first flashing to obtain a primary semi-lean liquid methanol and a first stream of a CO2 product gas; the second stream of the CO2 flashing liquid is subjected to the second flashing to obtain a flashing liquid and a second stream of a CO2 product gas; and the H2S flashing liquid is subjected to the third flashing to obtain the first H2S-rich methanol and a sulfur-containing gas phase; wherein the flashing liquid and the sulfur-containing gas phase are contacted to obtain a low-H2S methanol and a third stream of a CO2 product gas; and wherein the first CO2 product gas comprises the first stream of the CO2 product gas, the second stream of the CO2 product gas, and the third stream of the CO2 product gas.

[0074] In some embodiments of the present application, further preferably, the first stream of the CO2 flashing liquid is subjected to the first flashing after being subjected to a third cooling to -40 to -36℃; and the second stream of the CO2 flashing liquid is subjected to the second flashing after being subjected to a fourth cooling to -52 to -48℃.

[0075] In some embodiments of the present application, preferably, the pressure of the first flash is 0.45-0.55 MPa (G), the pressure of the second flash is 0.46-0.56 MPa (G), and the pressure of the third flash is 0.5-0.6 MPa (G).

[0076] In some embodiments of the present application, preferably, the mole content of H2S in the first semi-lean liquid methanol is 0.1-0.5 ppm, the mole content of CO2 is 20-24%, the temperature is -44 to -38℃, and the pressure is 0.45-0.55 MPa (G).

[0077] In some embodiments of the present application, preferably, the mole content of H2S in the low-H2S methanol is 0.1-0.3%, the mole content of CO2 is 24-28%, the temperature is -45 to -40℃, and the pressure is 0.46-0.56 MPa (G).

[0078] In some embodiments of the present application, preferably, the mole content of H2S in the first H2S-rich methanol is 0.3-0.5%, the mole content of CO2 is 24-28%, and the temperature is -46 to -42℃.

[0079] In some embodiments of the present application, preferably, the mole content of H2S in the first CO2 product gas is ≤1 ppm, the mole content of CO2 is 99-99.5%, the temperature is -45 to -40℃, and the pressure is 0.45-0.55 MPa (G).

[0080] In the present application, the fourth flash process comprises: fourth flashing the first semi-lean liquid methanol to obtain second semi-lean liquid methanol and second CO2 product gas. Preferably, the pressure of the fourth flash is 0.05-0.08 MPa (G).

[0081] In some embodiments of the present application, preferably, the fourth flash is performed after the first semi-lean liquid methanol is cooled to -52 to -48℃ by the sixth cooling.

[0082] In some embodiments of the present application, preferably, the mole content of H2S in the second semi-lean liquid methanol is 0.1-0.5 ppm, the mole content of CO2 is 16-21%, and the temperature is -63 to -48℃.

[0083] In the present application, the second semi-lean liquid methanol is divided into two streams, the first stream is subjected to third washing, and the second stream is returned to the second CO2 absorption. Further preferably, the mole flow ratio of the first stream of second semi-lean liquid methanol to the second stream of second semi-lean liquid methanol is 1:1-1.5.

[0084] In some embodiments of the present application, preferably, the fourth flash also obtains a second CO2 product gas with a molar content of H2S ≤ 1 ppm and a molar content of CO2 of 99.4-99.7%, at a temperature of -65 to -55 ℃ and a pressure of 0.05-0.08 MPa (G).

[0085] In the present application, the first washing process comprises: performing the first washing on the second non-reformed H2S-rich methanol, low-H2S methanol and CO2 flash gas to obtain washed CO2 flash gas and low-sulfur carbon-rich methanol.

[0086] In some embodiments of the present application, preferably, the low-H2S methanol is sequentially subjected to fourth pressurization to 1-1.2 MPa (G) and fifth cooling to -50 to -45 ℃ in the direction of material flow, and then subjected to the first washing.

[0087] In some embodiments of the present application, further preferably, the low-sulfur carbon-rich methanol has a molar content of H2S of 0.2-0.4% and a molar content of CO2 of 24-28%, at a temperature of -30 to -24 ℃ and a pressure of 0.8-1 MPa (G).

[0088] In some embodiments of the present application, further preferably, the first washing also obtains washed CO2 flash gas with a molar content of H2 of 34-38%, a molar content of CO of 5-10% and a molar content of CO2 of 53-58%, at a temperature of -35 to -30 ℃ and a pressure of 0.8-1 MPa (G), which is sent to a subsequent process.

[0089] In the present application, the second washing process comprises: performing the second washing on the third non-reformed H2S-rich methanol and H2S flash gas to obtain washed H2S flash gas and second H2S-rich methanol.

[0090] In some embodiments of the present application, preferably, the second H2S-rich methanol has a molar content of H2S of 0.6-0.8% and a molar content of CO2 of 6-9%, at a temperature of -28 to -23 ℃.

[0091] In some embodiments of the present application, preferably, the second washing also obtains washed H2S flash gas with a molar content of H2 of 45-49%, a molar content of CO of 33-37% and a molar content of CO2 of 14-19%, at a temperature of -32 to -28 ℃ and a pressure of 0.8-1 MPa (G), which is sent to a subsequent process.

[0092] In some embodiments of the present invention, preferably, the stripping process includes: independently contacting the first H2S-rich methanol, the second H2S-rich methanol, and the third H2S-rich methanol with nitrogen and performing the stripping to obtain stripping gas and H2S-rich methanol after stripping.

[0093] In some embodiments of the present invention, preferably, the molar content of H2S in the H2S-rich methanol after stripping is 2-5%, and the molar content of CO2 is 5-10%; the temperature is -70 to -62 °C.

[0094] In some embodiments of the present invention, preferably, the molar content of H2S in the third H2S-rich methanol is 3-6%, and the molar content of CO2 is 13-18%; the temperature is -63 to -58 °C; further preferably, after the third H2S-rich methanol is heat-exchanged to -40 to -38 °C, the stripping is performed.

[0095] In the present invention, the process of the third washing includes: performing the third washing on the first stream of semi-lean methanol and the stripping gas to obtain tail gas and the third H2S-rich methanol.

[0096] In some embodiments of the present invention, preferably, the molar content of H2S in the tail gas obtained by the third washing is ≤1 ppm, and the molar content of CO2 is 7-8%; the temperature is -70 to -60 °C.

[0097] A schematic structural diagram of a low-temperature methanol washing device for supporting a pulverized coal gasification device according to the second aspect of the present invention is as follows Figure 1 as shown, and it can be seen from Figure 1 that the device includes: a connected non-shift gas washing tower T-1, H2S absorption tower T-2, CO2 absorption tower T-3, medium-pressure flash tower T-4, re-absorption tower T-5, and H2S concentration tower T-6;

[0098] Among them, the non-shift gas washing tower T-1 is divided into a first purification section and a second purification section from bottom to top, and is used to perform primary purification and secondary purification on the non-shift gas 1 in sequence, obtaining three streams of non-shift H2S-rich methanol 2 and two streams of non-shift CO2-rich methanol 8;

[0099] The H2S absorption tower T-2 is divided into a first H2S absorption section and a second H2S absorption section from bottom to top, and is used to perform primary H2S absorption and secondary H2S absorption on the syngas 6 in sequence, obtaining primary H2S-rich methanol 7, secondary H2S-rich methanol 10, and desulfurized gas 11;

[0100] The CO2 absorption tower T-3 is divided into a first CO2 absorption section and a second CO2 absorption section from bottom to top, and is used for sequentially performing primary CO2 absorption and secondary CO2 absorption on the desulfurized gas 11 to obtain two groups of primary CO2-rich methanol 9, secondary CO2-rich methanol 12 and purified gas 14;

[0101] The medium-pressure flash tower T-4 is divided into a first washing section, a CO2 flash section, a second washing section and an H2S flash section from top to bottom; the CO2 flash section is used for performing CO2 flash on the second group of primary CO2-rich methanol 9-ii to obtain two groups of CO2 flash gas and CO2 flash liquid 17; and the H2S flash section is used for performing H2S flash on the secondary H2S-rich methanol 10 to obtain H2S flash gas and H2S flash liquid 19.

[0102] 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, and is used for performing first flash, second flash and third flash on the first group of CO2 flash liquid 17-i, the second group of CO2 flash liquid 17-ii and the H2S flash liquid 19 respectively to obtain primary semi-lean liquid methanol 13, low-H2S methanol 20, first H2S-rich methanol 21 and first CO2 product gas 22.

[0103] Among them, the first group of non-shift H2S-rich methanol 2-i returns to the first H2S absorption section; the first group of non-shift CO2-rich methanol 8-i and the second group of non-shift CO2-rich methanol 8-ii return to the second H2S absorption section and the first purification section respectively.

[0104] Among them, the first washing section is used for performing first washing on the second group of non-shift H2S-rich methanol 2-ii, low-H2S methanol 20 and the CO2 flash gas to obtain low-sulfur carbon-rich methanol 15 which returns to the second H2S absorption section; and the second washing section is used for performing second washing on the third group of non-shift H2S-rich methanol 2-iii and the H2S flash gas to obtain second H2S-rich methanol 16.

[0105] Among them, the H2S concentration tower T-6 is divided into a flash section, a washing section and a gas stripping section from top to bottom; the flash section is used for performing fourth flash on the primary semi-lean liquid methanol 13 to obtain two groups of secondary semi-lean liquid methanol 26; and the gas stripping section is used for performing gas stripping on the first H2S-rich methanol 21, the second H2S-rich methanol 16 and the third H2S-rich methanol 24 respectively, and the stripping gas obtained is sent to the washing section through a riser to perform third washing on the first group of secondary semi-lean liquid methanol 26-i to obtain the third H2S-rich methanol 24.

[0106] In the present application, as shown in the figure, Figure 1 In the non-shift gas washing tower T-1, the first purification section and the second purification section are communicated through a riser.

[0107] In the present application, as shown in Figure 1 In the present application, as shown in

[0108] In the present application, as shown in Figure 1 In the present application, as shown in

[0109] In the present application, as shown in Figure 1 In the present application, as shown in

[0110] In the present application, as shown in Figure 1 In the present application, as shown in

[0111] In the present application, as shown in Figure 1 In the present application, as shown in

[0112] According to the present application, preferably, as shown in Figure 1 In the present application, as shown in

[0113] According to the present application, preferably, as shown in Figure 1As shown, a second cooler E-2 is arranged on the pipeline connecting the first CO2 absorption section and the second CO2 absorption section, for cooling the second-stage CO2-rich methanol 12, and then the first-stage CO2 absorption is performed.

[0114] According to the present application, preferably, as shown in Figure 1 As shown, a second pump P-2 is arranged on the pipeline connecting the first washing section and the second H2S absorption section, for pressurizing the low-sulfur carbon-rich methanol 15, and then the second-stage H2S absorption is performed.

[0115] According to the present application, preferably, as shown in Figure 1 As shown, a third pump P-3 is arranged on the pipeline connecting the flash evaporation section and the second CO2 absorption section, for pressurizing the second-stage second-stage semi-lean liquid methanol 26-ii, and then the second-stage CO2 absorption is performed.

[0116] According to the present application, preferably, as shown in Figure 1 As shown in the medium-pressure flash evaporation tower T-4, a CO2 flash evaporation section is used for CO2 flash evaporation of the second-stage first-stage CO2-rich methanol 9-ii, and the obtained CO2 flash evaporation gas is sent to the first washing section through a riser, and the CO2 flash evaporation liquid 17 is obtained; a H2S flash evaporation section is used for H2S flash evaporation of the second-stage H2S-rich methanol 10, and the obtained H2S flash evaporation gas is sent to the second washing section through a riser, and the H2S flash evaporation liquid 19 is obtained; a first washing section is used for first washing of the second-stage non-shift H2S-rich methanol 2-ii, the low-H2S methanol 20 and the CO2 flash evaporation gas, and the washed CO2 flash evaporation gas 23 and the low-sulfur carbon-rich methanol 15 are obtained; and a second washing section is used for second washing of the third-stage non-shift H2S-rich methanol 2-iii and the H2S flash evaporation gas, and the washed H2S flash evaporation gas 18 and the second-stage H2S-rich methanol 16 are obtained.

[0117] According to the present application, preferably, as shown in Figure 1 As shown in the reabsorption tower T-5, a first flash evaporation section is used for the first flash evaporation of the first-stage CO2 flash evaporation liquid 17-i, and the first-stage semi-lean liquid methanol 13 and the first-stage CO2 product gas are obtained; a second flash evaporation section is used for the second flash evaporation of the second-stage CO2 flash evaporation liquid 17-ii, and the flash evaporation liquid and the second-stage CO2 product gas are obtained; and a third flash evaporation section is used for the third flash evaporation of the H2S flash evaporation liquid 19, and the first-stage H2S-rich methanol 21 is obtained, and the sulfur-containing gas phase is sent to the flash evaporation liquid through a riser, and the low-H2S methanol 20 and the third-stage CO2 product gas are obtained; wherein the first-stage CO2 product gas 22 includes the first-stage CO2 product gas, the second-stage CO2 product gas and the third-stage CO2 product gas.

[0118] According to the present application, preferably, as shown in Figure 1 A third cooler E-3 is arranged on the pipeline connecting the CO2 flash section and the first flash section, for performing the first flash after the third cooling of the first CO2 flash liquid 17-i.

[0119] According to the present application, preferably, as shown in Figure 1 A fourth pump P-4 and a fifth cooler E-5 are arranged in sequence on the pipeline connecting the second flash section and the first washing section in the material flow direction, for performing the first washing after the fourth pressurization and the fifth cooling of the low H2S methanol 20.

[0120] According to the present application, preferably, as shown in Figure 1 In the H2S concentration tower T-6, a flash section is used for performing the fourth flash of the primary semi-lean liquid methanol 13 to obtain the second CO2 product gas 4 and the secondary semi-lean liquid methanol 26; a washing section is used for performing the third washing of the first secondary semi-lean liquid methanol 26-i and the stripping gas to obtain the tail gas 27 and the third H2S-rich methanol 24; and a stripping section is used for contacting the first H2S-rich methanol 21, the second H2S-rich methanol 16, the third H2S-rich methanol 24 and the nitrogen gas 25 and performing the stripping to obtain the stripping gas and the post-stripping H2S-rich methanol 28.

[0121] According to the present application, preferably, as shown in Figure 1 A sixth cooler E-6 is arranged on the pipeline connecting the first flash section and the flash section, for performing the fourth flash after the sixth cooling of the primary semi-lean liquid methanol 13.

[0122] According to the present application, preferably, as shown in Figure 1 A heat exchanger Q is arranged on the pipeline connecting the washing section and the stripping section, for performing the stripping after the heat exchange of the third H2S-rich methanol 24.

[0123] The present application will be described in detail through examples.

[0124] In the present application, the synthesis gas and the non-shift gas are both derived from the pulverized coal gasification device without special circumstances.

[0125] Example 1

[0126] The device is as shown in ​As shown, the device comprises: a non-reforming gas washing 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 and an H2S concentration tower T-6, and 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 and a sixth cooler E-6, and a first pump P-1, a second pump P-2, a third pump P-3 and a fourth pump P-4, and a heat exchanger Q;

[0127] The method is carried out in the above device, comprising:

[0128] The non-reforming gas 1 (the molar content of H2S is 0.4-0.6%, the molar content of CO2 is 5-10%; the temperature is -35 to -25℃, and the pressure is 3.5-3.6 MPa(G)) and the second non-reforming CO2-rich methanol 8-ii are contacted at a molar flow ratio of 1.3-1.5:1 and subjected to primary purification to obtain non-reforming H2S-rich methanol 2 (the molar content of H2S is 0.5-0.9%, the molar content of CO2 is 3-7%; the temperature is -33 to -28℃; the pressure is 3.5-3.55 MPa(G)) and desulfurized non-reforming gas; the above desulfurized non-reforming gas and the first lean methanol 3-i are contacted and subjected to secondary purification to obtain non-reforming CO2-rich methanol 8 (the molar content of H2S is 0.5-1 ppm, the molar content of CO2 is 4-7%; the temperature is -40 to -33℃) and purified non-reforming gas 5 (the molar content of H2S is ≤0.1 ppm, the molar content of CO2 is ≤20 ppm; the temperature is -55 to -45℃, and the pressure is 3.4-3.5 MPa(G));

[0129] The above non-reforming H2S-rich methanol 2 is divided into the first non-reforming H2S-rich methanol 2-i, the second non-reforming H2S-rich methanol 2-ii and the third non-reforming H2S-rich methanol 2-iii at a molar flow ratio of 1:1-2:3-5;

[0130] The above non-reforming CO2-rich methanol 8 is divided into the first non-reforming CO2-rich methanol 8-i and the second non-reforming CO2-rich methanol 8-ii at a molar flow ratio of 1:1-1.1;

[0131] The molar flow ratio of the above second non-reforming CO2-rich methanol 8-ii and the non-reforming gas 1 is 1:1.3-1.5; the molar flow ratio of the above first lean methanol 3-i and the non-reforming gas 1 is 1.5-2:1;

[0132] The above synthesis gas 6 (molar content of H2S is 0.3-0.35%, molar content of CO2 is 40-50%; temperature is -25 to -15°C, pressure is 3.12-3.15 MPa(G)) and the first non-shift H2S-rich methanol 2-i are contacted at a molar flow ratio of 40-50:1 and subjected to primary H2S absorption to obtain pre-desulfurization gas and primary H2S-rich methanol 7 (molar content of H2S is 0.6-0.8%, molar content of CO2 is 30-36%; temperature is -25 to -15°C); the above pre-desulfurization gas, low-sulfur carbon-rich methanol 15 (second pressurized to 3.6-4 MPa(G)), the first non-shift CO2-rich methanol 8-i and the first primary CO2-rich methanol 9-i (first pressurized to 3.6-4 MPa(G) in turn, first cooled to -46 to -43°C) are contacted and subjected to secondary H2S absorption to obtain desulfurization gas 11 and secondary H2S-rich methanol 10 (molar content of H2S is 0.4-0.6%, molar content of CO2 is 27-31%; temperature is -20 to -16°C);

[0133] The molar flow ratio of the low-sulfur carbon-rich methanol 15 and the synthesis gas 6 is 1:7-9; the molar flow ratio of the first non-shift CO2-rich methanol 8-i and the synthesis gas 6 is 1:6-7; the molar flow ratio of the first primary CO2-rich methanol 9-i and the synthesis gas 6 is 1-3:6-7;

[0134] The above desulfurization gas 11 and the secondary CO2-rich methanol 12 (second cooled to -36 to -33°C) are contacted at a molar flow ratio of 1:1.5-2.5 and subjected to primary CO2 absorption to obtain primary CO2-rich methanol 9 (molar content of H2S is 0.1-0.5 ppm, molar content of CO2 is 21-26%, temperature is -24 to -18°C, pressure is 3.05-3.09 MPa(G)) and pre-purified gas; the above pre-purified gas, the second secondary semi-lean liquid methanol 26-ii (third pressurized to 3.6-4 MPa(G)) and the second lean methanol 3-ii are subjected to secondary CO2 absorption to obtain secondary CO2-rich methanol 12 and purified gas 14 (molar content of H2S is ≤0.1 ppm, molar content of CO2 is 2-3%; temperature is -48 to -44°C, pressure is 3-3.05 MPa(G));

[0135] The molar flow ratio of the above purified gas 14 and the second secondary semi-lean liquid methanol 26-ii is 1:1.1-1.3, and the molar flow ratio of the purified gas 14 and the second lean methanol 3-ii is 1:1.5-1.7;

[0136] The above primary CO2-rich methanol 9 is divided into the first primary CO2-rich methanol 9-i and the second primary CO2-rich methanol 9-ii at a molar flow ratio of 1:4-5;

[0137] The second stream of the first CO2-rich methanol 9-ii is subjected to a CO2 flash (at a pressure of 0.8-1 MPa (G)) to obtain a CO2 flash gas and a CO2 flash liquid 17 (having a molar H2S content of 0.1-0.5 ppm and a molar CO2 content of 15-20%, at a temperature of -26 to -21°C);

[0138] The second H2S-rich methanol 10 is subjected to an H2S flash (at a pressure of 0.8-1 MPa (G)) to obtain an H2S flash gas and an H2S flash liquid 19 (having a molar H2S content of 0.35-0.55% and a molar CO2 content of 26.5-30.5%, at a temperature of -40 to -33°C);

[0139] The CO2 flash liquid 17 is divided into a first CO2 flash liquid 17-i and a second CO2 flash liquid 17-ii in a molar flow ratio of 18-22:1; the first CO2 flash liquid 17-i (cooled to a temperature of -40 to -36°C) is subjected to a first flash (at a pressure of 0.45-0.55 MPa (G)) to obtain a first semi-lean liquid methanol 13 (having a molar H2S content of 0.1-0.5 ppm and a molar CO2 content of 20-24%, at a temperature of -44 to -38°C) and a first CO2 product gas; the second CO2 flash liquid 17-ii (cooled to a temperature of -52 to -48°C) is subjected to a second flash (at a pressure of 0.46-0.56 MPa (G)) to obtain a flash liquid and a second CO2 product gas;

[0140] The H2S flash liquid 19 is subjected to a third flash (at a pressure of 0.5-0.6 MPa (G)) to obtain the first H2S-rich methanol 21 (having a molar H2S content of 0.3-0.5% and a molar CO2 content of 24-28%, at a temperature of -46 to -42°C) and a sulphur-containing gas phase; wherein the flash liquid and the sulphur-containing gas phase are contacted to obtain a low H2S methanol 20 (having a molar H2S content of 0.1-0.3% and a molar CO2 content of 24-28%, at a temperature of -45 to -40°C, at a pressure of 0.46-0.56 MPa (G)) and a third CO2 product gas; wherein the first CO2 product gas, the second CO2 product gas and the third CO2 product gas are combined to obtain a first CO2 product gas 22 (having a molar H2S content of <1 ppm and a molar CO2 content of 99-99.5%, at a temperature of -45 to -40°C, at a pressure of 0.45-0.55 MPa (G));

[0141] The first-stage semi-lean liquid methanol 13 (cooled to -52 to -48°C) is subjected to a fourth flash (pressure 0.05-0.08 MPa (G)) to obtain a second CO2 product gas 4 (molar content of H2S < 1 ppm, molar content of CO2 99.4-99.7%; temperature -65 to -55°C, pressure 0.05-0.08 MPa (G)) and a second-stage semi-lean liquid methanol 26 (molar content of H2S 0.1-0.5 ppm, molar content of CO2 16-21%; temperature -63 to -48°C);

[0142] wherein the second-stage semi-lean liquid methanol 26 is divided into a first portion of second-stage semi-lean liquid methanol 26-i and a second portion of second-stage semi-lean liquid methanol 26-ii in a molar flow ratio of 1 : 1-1.5;

[0143] The second portion of non-shifted H2S-rich methanol 2-ii, low-H2S methanol 20 (successively pressurized to 1-1.2 MPa (G), cooled to -50 to -45°C) are each independently subjected to a first washing with CO2 flash gas to obtain washed CO2 flash gas 23 (molar content of H2 34-38%, molar content of CO 5-10%, molar content of CO2 53-58%; temperature -35 to -30°C) and low-sulfur carbon-rich methanol 15 (molar content of H2S 0.2-0.4%, molar content of CO2 24-28%; temperature -30 to -24°C, pressure 0.8-1 MPa (G));

[0144] The third portion of non-shifted H2S-rich methanol 2-iii and H2S flash gas are subjected to a second washing to obtain washed H2S flash gas 18 (molar content of H2 45-49%, molar content of CO 33-37%, molar content of CO2 14-19%; temperature -32 to -28°C) and second H2S-rich methanol 16 (molar content of H2S 0.6-0.8%, molar content of CO2 6-9%, temperature -28 to -23°C);

[0145] The first H2S-rich methanol 21, the second H2S-rich methanol 16, the third H2S-rich methanol 24 (cooled to -40 to -38°C) are each independently contacted with nitrogen 25 and subjected to stripping to obtain a stripping gas and a stripped H2S-rich methanol 28 (molar content of H2S 2-5%, molar content of CO2 5-10%; temperature -70 to -62°C); the stripping gas and the first portion of second-stage semi-lean liquid methanol 26-i are subjected to a third washing to obtain a tail gas 27 (molar content of H2S < 1 ppm, molar content of CO2 72-78%; temperature -70 to -60°C) and a third H2S-rich methanol 24 (molar content of H2S 3-6%, molar content of CO2 13-18%; temperature -63 to -58°C).

[0146] Comparative Example 1

[0147] Taking a hydrogen production device using gasification of pulverized coal as an example, the effective gas (H2+CO) entering the low-temperature methanol washing device is 161000 Nm 3 / h, and based on this benchmark, the main parameters of CN201110260570.0 (a low-temperature methanol washing process and) are compared in Table 1.

[0148] Table 1

[0149]

[0150] As can be seen from the results in Table 1, taking a hydrogen production device based on gasification of pulverized coal as an example, the low-temperature methanol washing method of the supporting pulverized coal gasification device provided in Example 1 has a lean methanol circulation amount of 84.6% of the lean methanol circulation amount in Comparative Example 1 (lean liquid-semi-lean liquid process), a semi-lean liquid methanol circulation amount of 75% of the semi-lean / low-carbon methanol circulation amount in Comparative Example 1 (lean liquid-semi-lean liquid process), a rich CO2 methanol usage amount in the H2S absorption tower of 71.4% of the rich CO2 methanol usage amount in Comparative Example 1 (lean liquid-semi-lean liquid process), and an accumulated reduction of external cold consumption of 1300 KW / h, and the overall energy-saving effect is remarkable.

[0151] 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 rectisol process for a coal gasification plant, characterized in that, The method comprises: (1) sequentially subjecting synthesis gas (6) derived from a pulverized coal gasification device to primary H2S absorption and secondary H2S absorption to obtain primary H2S-rich methanol (7), secondary H2S-rich methanol (10) and desulfurized gas (11); sequentially subjecting the desulfurized gas (11) to primary CO2 absorption and secondary CO2 absorption to obtain primary CO2-rich methanol (9) in two streams, secondary CO2-rich methanol (12) and purified gas (14); wherein non-shift H2S-rich methanol (2) derived from a non-shift gas purification process is divided into three streams and non-shift CO2-rich methanol (8) is divided into two streams; wherein the first stream of non-shift H2S-rich methanol (2-i) is returned to the primary H2S absorption; the first stream of non-shift CO2-rich methanol (8-i) and the second stream of non-shift CO2-rich methanol (8-ii) are returned to the secondary H2S absorption and primary purification, respectively; (2) subjecting the second stream of primary CO2-rich methanol (9-ii) to CO2 flashing to obtain CO2 flashing gas and CO2 flashing liquid (17) in two streams; subjecting the secondary H2S-rich methanol (10) to H2S flashing to obtain H2S flashing gas and H2S flashing liquid (19); (3) subjecting the first stream of CO2 flashing liquid (17-i), the second stream of CO2 flashing liquid (17-ii) and the H2S flashing liquid (19) to first flashing, second flashing and third flashing, respectively, to obtain primary semi-lean liquid methanol (13), low-H2S methanol (20), first H2S-rich methanol (21) and first CO2 product gas (22); subjecting the primary semi-lean liquid methanol (13) to fourth flashing to obtain secondary semi-lean liquid methanol (26) in two streams, and the second stream of secondary semi-lean liquid methanol (26-ii) is returned to the secondary CO2 absorption; wherein the second stream of non-shift H2S-rich methanol (2-ii) and the low-H2S methanol (20) are subjected to first washing with the CO2 flashing gas to obtain low-sulfur carbon-rich methanol (15) which is returned to the secondary H2S absorption; the third stream of non-shift H2S-rich methanol (2-iii) and the H2S flashing gas are subjected to second washing to obtain second H2S-rich methanol (16); the first H2S-rich methanol (21), the second H2S-rich methanol (16) and the third H2S-rich methanol (24) are subjected to gas stripping, respectively, to obtain gas stripping gas and the first stream of secondary semi-lean liquid methanol (26-i) which are subjected to third washing to obtain the third H2S-rich methanol (24).

2. The method of claim 1, wherein, The non-shift gas purification process comprises: sequentially subjecting non-shift gas (1) derived from a pulverized coal gasification device to primary purification and secondary purification to obtain non-shift H2S-rich methanol (2), non-shift CO2-rich methanol (8) and purified non-shift gas (5); Preferably, the non-shift gas (1) and the second stream of non-shift CO2-rich methanol (8-ii) are subjected to the primary purification to obtain the non-shift H2S-rich methanol (2) and desulfurized non-shift gas; the desulfurized non-shift gas and the first stream of lean methanol (3-i) are subjected to the secondary purification to obtain the non-shift CO2-rich methanol (8) and the purified non-shift gas (5); Preferably, the non-reformed H2S-rich methanol (2) has a molar content of H2S of 0.5-0.9% and a molar content of CO2 of 3-7%; a temperature of -33 to -28℃; and a pressure of 3.5-3.55 MPa (G); Preferably, the first, second and third non-reformed H2S-rich methanols (2-i, 2-ii and 2-iii) have a molar flow ratio of 1:1-2:3-5; Preferably, the non-reformed CO2-rich methanol (8) has a molar content of H2S of 0.5-1 ppm and a molar content of CO2 of 4-7%; a temperature of -40 to -33℃; Preferably, the first and second non-reformed CO2-rich methanols (8-i and 8-ii) have a molar flow ratio of 1:1-1.

1.

3. The method of claim 1 or 2, wherein, In step (1), The first-stage H2S absorption is performed on the synthesis gas (6) and the first non-reformed H2S-rich methanol (2-i) to obtain the first-stage H2S-rich methanol (7) and a pre-desulfurized gas; the second-stage H2S absorption is performed on the pre-desulfurized gas, the low-sulfur carbon-rich methanol (15), the first non-reformed CO2-rich methanol (8-i) and the first first-stage CO2-rich methanol (9-i) to obtain the second-stage H2S-rich methanol (10) and a desulfurized gas (11); Preferably, the second-stage H2S-rich methanol (10) has a molar content of H2S of 0.4-0.6% and a molar content of CO2 of 27-31%; a temperature of -20 to -10℃; Preferably, the first first-stage CO2-rich methanol (9-i) is sequentially subjected to a first pressurization to 3.6-4 MPa (G) and a first cooling to -46 to -43℃ in the order of material flow direction, and then subjected to the second-stage H2S absorption; Preferably, the low-sulfur carbon-rich methanol (15) is subjected to a second pressurization to 3.6-4 MPa (G) before the second-stage H2S absorption; Preferably, the desulfurized gas (11) and the second-stage CO2-rich methanol (12) are subjected to the first-stage CO2 absorption to obtain the first-stage CO2-rich methanol (9) and a pre-purified gas; The second-stage CO2 absorption is performed on the pre-purified gas, the second second-stage semi-lean liquid methanol (26-ii) and the second lean methanol (3-ii) to obtain the second-stage CO2-rich methanol (12) and a purified gas (14); Preferably, the first-stage CO2-rich methanol (9) has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 21-26%, a temperature of -24 to -18℃ and a pressure of 3.05-3.09 MPa (G); Preferably, the first and second first-stage CO2-rich methanols (9-i and 9-ii) have a molar flow ratio of 1:4-5; Preferably, the second-stage CO2-rich methanol (12) is subjected to a second cooling to -36 to -33℃ before the first-stage CO2 absorption; Preferably, the second stream of the secondary semi-lean methanol (26-ii) is subjected to the third pressurization to 3.6-4 MPa (G) before the secondary CO2 absorption.

4. The method of any of claims 1-3, wherein, In step (2), The molar content of H2S in the CO2 flash liquid (17) is 0.1-0.5 ppm, the molar content of CO2 is 15-20%, and the temperature is -26 to -21℃; Preferably, the molar flow ratio of the first stream of the CO2 flash liquid (17-i) and the second stream of the CO2 flash liquid (17-ii) is 18-22:1; Preferably, the molar content of H2S in the H2S flash liquid (19) is 0.35-0.55%, the molar content of CO2 is 26.5-30.5%, and the temperature is -40 to -33℃.

5. The method of any of claims 1-4, wherein, In step (3), The first stream of the CO2 flash liquid (17-i) is subjected to the first flash after being cooled to -40 to -36℃ by the third cooling, and the second stream of the CO2 flash liquid (17-ii) is subjected to the second flash after being cooled to -52 to -48℃ by the fourth cooling; Preferably, the pressure of the first flash is 0.45-0.55 MPa (G), the pressure of the second flash is 0.46-0.56 MPa (G), and the pressure of the third flash is 0.5-0.6 MPa (G); Preferably, the molar content of H2S in the primary semi-lean methanol (13) is 0.1-0.5 ppm, the molar content of CO2 is 20-24%, and the temperature is -44 to -38℃; Preferably, the molar content of H2S in the low-H2S methanol (20) is 0.1-0.3%, the molar content of CO2 is 24-28%, the temperature is -45 to -40℃, and the pressure is 0.46-0.56 MPa (G); Preferably, the molar content of H2S in the first H2S-rich methanol (21) is 0.3-0.5%, the molar content of CO2 is 24-28%, and the temperature is -46 to -42℃; Preferably, the molar content of H2S in the first CO2 product gas (22) is ≤1 ppm, the molar content of CO2 is 99-99.5%, the temperature is -45 to -40℃, and the pressure is 0.45-0.55 MPa (G); Preferably, the pressure of the fourth flash is 0.05-0.08 MPa (G); Preferably, the primary semi-lean methanol (13) is subjected to the fourth flash after being cooled to -52 to -48℃ by the sixth cooling; Preferably, the molar content of H2S in the secondary semi-lean methanol (26) is 0.1-0.5 ppm, the molar content of CO2 is 16-21%, and the temperature is -63 to -48℃; further preferably, the molar flow ratio of the first stream of the secondary semi-lean methanol (26-i) and the second stream of the secondary semi-lean methanol (26-ii) is 1:1-1.

5. Preferably, the fourth flash also obtains the second CO2 product gas (4) with a molar content of H2S ≤1 ppm and a molar content of CO2 of 99.4-99.7%, a temperature of -65 to -55 ℃, and a pressure of 0.05-0.08 MPa (G).

6. The method of any of claims 1-5, wherein, The low-H2S methanol (20) is sequentially subjected to fourth pressurization to 1-1.2 MPa (G) and fifth cooling to -50 to -45 ℃ in the direction of material flow, and then subjected to the first washing; Preferably, the low-sulfur carbon-rich methanol (15) has a molar content of H2S of 0.2-0.4% and a molar content of CO2 of 24-28%, a temperature of -30 to -24 ℃, and a pressure of 0.8-1 MPa (G). Preferably, the second H2S-rich methanol (16) has a molar content of H2S of 0.6-0.8% and a molar content of CO2 of 6-9%, a temperature of -28 to -23 ℃.

7. The method of any of claims 1-6, wherein, The stripping process includes: contacting the first H2S-rich methanol (21), the second H2S-rich methanol (16), and the third H2S-rich methanol (24) with nitrogen (25) independently and performing the stripping to obtain stripping gas and H2S-rich methanol (28) after stripping; Preferably, the H2S-rich methanol (28) after stripping has a molar content of H2S of 2-5% and a molar content of CO2 of 5-10%, a temperature of -70 to -62 ℃; Preferably, the third H2S-rich methanol (24) has a molar content of H2S of 3-6% and a molar content of CO2 of 13-18%, a temperature of -63 to -58 ℃; Preferably, the third H2S-rich methanol (24) is subjected to heat exchange to -40 to -38 ℃ before being subjected to the stripping. Preferably, the third washing also obtains tail gas (27) with a molar content of H2S ≤1 ppm and a molar content of CO2 of 72-78%, a temperature of -70 to -60 ℃.

8. A rectisol unit of a coal gasification plant, characterized in that, The device comprises: connected non-reformed gas washing tower (T-1), H2S absorption tower (T-2), CO2 absorption tower (T-3), medium-pressure flash tower (T-4), reabsorption tower (T-5), and H2S concentration tower (T-6); The non-reformed gas washing tower (T-1) is divided into a first purification section and a second purification section from bottom to top, and is used for sequentially performing primary purification and secondary purification on the non-reformed gas (1) to obtain three streams of non-reformed H2S-rich methanol (2) and two streams of non-reformed CO2-rich methanol (8); The H2S absorption tower (T-2) is divided into a first H2S absorption section and a second H2S absorption section from bottom to top, and is used for sequentially performing primary H2S absorption and secondary H2S absorption on the synthesis gas (6) to obtain primary H2S-rich methanol (7), secondary H2S-rich methanol (10), and desulfurized gas (11); The CO2 absorption tower (T-3) is divided into a first CO2 absorption section and a second CO2 absorption section from bottom to top, and is used for sequentially performing primary CO2 absorption and secondary CO2 absorption on the desulfurized gas (11) to obtain two streams of primary CO2-rich methanol (9), secondary CO2-rich methanol (12), and purified gas (14); The medium-pressure flash tower (T-4) is divided into a first washing section, a CO2 flash section, a second washing section, and an H2S flash section from top to bottom; the CO2 flash section is used for CO2 flashing of the second primary CO2-rich methanol (9-ii) to obtain two streams of CO2 flash gas and CO2 flash liquid (17); 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 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 for first flashing, second flashing, and third flashing of the first CO2 flash liquid (17-i), the second CO2 flash liquid (17-ii), and the H2S flash liquid (19) respectively to obtain the primary semi-lean liquid methanol (13), the low-H2S methanol (20), the first H2S-rich methanol (21), and the first CO2 product gas (22); Among them, the first non-shift H2S-rich methanol (2-i) returns to the first H2S absorption section; the first non-shift CO2-rich methanol (8-i) and the second non-shift CO2-rich methanol (8-ii) return to the second H2S absorption section and the first purification section respectively; Among them, the first washing section is used for first washing of the second non-shift H2S-rich methanol (2-ii), the low-H2S methanol (20), and the CO2 flash gas to obtain low-sulfur carbon-rich methanol (15) which returns to the second H2S absorption section; the second washing section is used for second washing of the third non-shift H2S-rich methanol (2-iii) and the H2S flash gas to obtain the second H2S-rich methanol (16); Among them, the H2S concentration tower (T-6) is divided into a flash section, a washing section, and a gas stripping section from top to bottom; the flash section is used for fourth flashing of the primary semi-lean liquid methanol (13) to obtain two streams of secondary semi-lean liquid methanol (26); the gas stripping section is used for gas stripping of the first H2S-rich methanol (21), the second H2S-rich methanol (16), and the third H2S-rich methanol (24) respectively; the stripping gas obtained is sent to the washing section through a riser and is used for third washing of the first secondary semi-lean liquid methanol (26-i) to obtain the third H2S-rich methanol (24).

9. The apparatus of claim 8, wherein, A first pump (P-1) is arranged on a pipeline connecting the second H2S absorption section and the first CO2 absorption section in sequence in the direction of material flow; Preferably, a second cooler (E-2) is arranged on a pipeline connecting the first CO2 absorption section and the second CO2 absorption section in the direction of material flow; Preferably, a second pump (P-2) is arranged on a pipeline connecting the first washing section and the second H2S absorption section in the direction of material flow; Preferably, a third pump (P-3) is arranged on a pipeline connecting the flash section and the second CO2 absorption section in the direction of material flow.

10. The apparatus of claim 8 or 9, wherein, A third cooler (E-3) is arranged on a pipeline connecting the CO2 flash section and the first flash section. Preferably, a fourth cooler (E-4) is arranged on the pipeline connecting the CO2 flash section and the second flash section; Preferably, a fourth pump (P-4) and a fifth cooler (E-5) are arranged in sequence on the pipeline connecting the second flash section and the first washing section in the direction of material flow; Preferably, a sixth cooler (E-6) is arranged on the pipeline connecting the first flash section and the flash section; Preferably, a heat exchanger (Q) is arranged on the pipeline connecting the washing section and the gas stripping section.

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