Synthesis gas purification method matched with pulverized coal gasification device and device thereof

Abstract

The invention relates to the technical field of low-temperature methanol washing, in particular to a synthesis gas purification method matched with a pulverized coal gasification device and the pulverized coal gasification device, according to the purification method, low-H2S methanol and low-CO2 methanol are recycled and subjected to H2S absorption and CO2 absorption respectively, the use efficiency and the absorption capacity are high, and the purification effect is good. And the comprehensive energy consumption of the low-temperature methanol washing device can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature methanol washing, and specifically relates to a method for purifying syngas for a pulverized coal gasification device and a device for purifying syngas for a pulverized coal gasification device. Background Art

[0002] In the syngas produced by using the pulverized coal gasification technology, H 2 and CO are called effective gases. At the same time, the syngas also contains a large amount of CO 2 and trace amounts of H 2 S, COS, NH 3 , HCN and other components. Among them, H 2 and CO are raw material gases for synthesizing chemical products such as methanol and ammonia after adjusting the hydrogen-carbon ratio through a shift unit. Acid gases CO 2 and H 2 S are generally poisons for synthesis catalysts, so they must be removed before the synthesis process.

[0003] The low-temperature methanol washing technology uses low-temperature methanol as an absorption solvent, and utilizes the excellent property that low-temperature methanol has a great solubility for acid gases to physically absorb and remove H 2 S and CO 2 and other acid gases in the syngas, and at the same time removes trace components such as HCN and NH 3 . This process has the advantages of high gas purification degree, good selectivity, and large methanol absorption capacity. The regeneration of the methanol solvent after absorbing the acid gas is achieved through staged pressure reduction flashing and thermal regeneration.

[0004] Currently, the innovative research on the low-temperature methanol washing technology mainly focuses on the recycling of the pressure reduction flashing of the CO 2 -rich methanol. The typical process is the lean liquid-semi-lean liquid process, and this technology has played a positive role in reducing the comprehensive energy consumption of the low-temperature methanol washing process. In the low-temperature methanol washing process flow, the CO 2 -rich methanol can be recycled through flashing, but the H 2 S-rich methanol must be recycled through thermal regeneration, which is the main energy-consuming source of the low-temperature methanol washing. Therefore, improving the utilization efficiency of the H 2 S-rich methanol is the direction and key factor for future technological innovation. Specifically, it is necessary to achieve that before the thermal regeneration of the H 2 S-rich methanol, its absorption of H 2 S gas in the syngas reaches the upper limit, so as to reduce the amount of H 2 S-rich methanol that needs to be thermally regenerated.

[0005] CN201110260570.0 discloses a low-temperature methanol washing process. First, in the H 2 S absorption tower, all use CO2 Methanol is used to wash the syngas, increasing the production of H 2 -rich methanol. The H 2 -rich methanol needs to be thermally regenerated before it can be recycled, resulting in high energy consumption. Second, in the CO 2 flashing section of the reabsorption tower, the CO 2 -rich methanol directly mixes with the H 2 -rich methanol flash gas while washing the H 2 -rich methanol, and is contaminated by the H 2 -rich methanol. The resulting low-concentration H 2 -rich methanol is not effectively utilized, leading to high energy consumption. Third, the semi-lean methanol for the CO 2 absorption tower has a relatively high CO 2 content, with limited absorption capacity for CO 2 gas, which is not conducive to reducing the overall energy consumption of the cold methanol washing unit. Summary of the Invention

[0006] The object of the present invention is to overcome the above problems and provide a syngas purification method and a syngas purification device for a pulverized coal gasification unit. The purification method recycles low-H 2 -rich methanol and low-CO 2 -rich methanol and separately performs H 2 absorption and CO 2 absorption, not only having high use efficiency and absorption capacity, but also being able to effectively reduce the overall energy consumption of the cold methanol washing unit.

[0007] To achieve the above object, in the first aspect of the present invention, a syngas purification method for a pulverized coal gasification unit is provided, and the method includes:

[0008] (1) Performing H 2 absorption on the syngas to obtain first H 2 -rich methanol, second H 2 -rich methanol and desulfurized gas; performing CO 2 absorption on the desulfurized gas to obtain CO 2 -rich methanol, which is divided into first CO 2 -rich methanol and second CO 2 -rich methanol;

[0009] (2) Flashing the second CO 2 -rich methanol to obtain flashed CO 2 -rich methanol; flashing the second H 2 -rich methanol to obtain flashed H 2 -rich methanol; 2 S flashing the second H 2 -rich methanol to obtain flashed H

[0010] (3) Heat exchange the CO-rich methanol after flashing with the first semi-lean methanol to obtain heat-exchanged CO-rich methanol and heat-exchanged semi-lean methanol; cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption. 2 Heat exchange the CO-rich methanol after flashing with the first semi-lean methanol to obtain heat-exchanged CO-rich methanol and heat-exchanged semi-lean methanol; cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption. 2 Heat exchange the CO-rich methanol after flashing with the first semi-lean methanol to obtain heat-exchanged CO-rich methanol and heat-exchanged semi-lean methanol; cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption. 2 Cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption. 2 Cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption. 2 Cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption. 2 Cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption. 2 Cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption. 2 Cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption. 2 Cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption. 2 Cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption. 2 Cool the heat-exchanged CO-rich methanol for the first time to obtain cooled CO-rich methanol, which is divided into two streams. The first stream of cooled CO-rich methanol is subjected to the first flash, and the second stream of cooled CO-rich methanol is cooled for the second time and then subjected to the second flash; subject the H₂S-rich methanol after flashing to the third flash to obtain semi-lean methanol, low-H₂S methanol, and CO product gas; and return the low-H₂S methanol and perform the H₂S absorption.

[0011] (4) Contact the heat-exchanged semi-lean methanol with nitrogen and perform stripping to obtain low-CO methanol, which is returned and subjected to the CO absorption; return the low-H₂S methanol and perform the H₂S absorption. 2 Contact the heat-exchanged semi-lean methanol with nitrogen and perform stripping to obtain low-CO methanol, which is returned and subjected to the CO absorption; return the low-H₂S methanol and perform the H₂S absorption. 2 Contact the heat-exchanged semi-lean methanol with nitrogen and perform stripping to obtain low-CO methanol, which is returned and subjected to the CO absorption; return the low-H₂S methanol and perform the H₂S absorption. 2 Contact the heat-exchanged semi-lean methanol with nitrogen and perform stripping to obtain low-CO methanol, which is returned and subjected to the CO absorption; return the low-H₂S methanol and perform the H₂S absorption. 2 Contact the heat-exchanged semi-lean methanol with nitrogen and perform stripping to obtain low-CO methanol, which is returned and subjected to the CO absorption; return the low-H₂S methanol and perform the H₂S absorption.

[0012] The second aspect of the present invention provides a syngas purification device for a pulverized coal gasification device, which includes an H₂S absorption tower, a CO absorption tower, a flash tower, a reabsorption tower, and a stripping tower connected in sequence, as well as a heat exchanger, a first cooler, and a second cooler. 2 The H₂S absorption tower is used for H₂S absorption of the syngas to obtain first H₂S-rich methanol, second H₂S-rich methanol, and desulfurized gas; the CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol. 2 The H₂S absorption tower is used for H₂S absorption of the syngas to obtain first H₂S-rich methanol, second H₂S-rich methanol, and desulfurized gas; the CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol.

[0013] The H₂S absorption tower is used for H₂S absorption of the syngas to obtain first H₂S-rich methanol, second H₂S-rich methanol, and desulfurized gas; the CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol. 2 The H₂S absorption tower is used for H₂S absorption of the syngas to obtain first H₂S-rich methanol, second H₂S-rich methanol, and desulfurized gas; the CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol. 2 The H₂S absorption tower is used for H₂S absorption of the syngas to obtain first H₂S-rich methanol, second H₂S-rich methanol, and desulfurized gas; the CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol. 2 The H₂S absorption tower is used for H₂S absorption of the syngas to obtain first H₂S-rich methanol, second H₂S-rich methanol, and desulfurized gas; the CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol. 2 The H₂S absorption tower is used for H₂S absorption of the syngas to obtain first H₂S-rich methanol, second H₂S-rich methanol, and desulfurized gas; the CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol. 2 The CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol. 2 The CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol. 2 The CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol. 2 The CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol. 2 The CO absorption tower is used for CO absorption of the desulfurized gas to obtain rich CO methanol, which is divided into a first stream of rich CO methanol and a second stream of rich CO methanol.

[0014] The flash tower includes a CO flash section provided on the upper part and an H₂S flash section provided on the lower part. The CO flash section is used for CO flashing of the second stream of rich CO methanol to obtain flashed CO-rich methanol. 2 The flash tower includes a CO flash section provided on the upper part and an H₂S flash section provided on the lower part. The CO flash section is used for CO flashing of the second stream of rich CO methanol to obtain flashed CO-rich methanol. 2 The flash tower includes a CO flash section provided on the upper part and an H₂S flash section provided on the lower part. The CO flash section is used for CO flashing of the second stream of rich CO methanol to obtain flashed CO-rich methanol. 2 The flash tower includes a CO flash section provided on the upper part and an H₂S flash section provided on the lower part. The CO flash section is used for CO flashing of the second stream of rich CO methanol to obtain flashed CO-rich methanol. 2 The flash tower includes a CO flash section provided on the upper part and an H₂S flash section provided on the lower part. The CO flash section is used for CO flashing of the second stream of rich CO methanol to obtain flashed CO-rich methanol. 2 The flash tower includes a CO flash section provided on the upper part and an H₂S flash section provided on the lower part. The CO flash section is used for CO flashing of the second stream of rich CO methanol to obtain flashed CO-rich methanol.2 Methanol, H 2 The S flash section is used to subject the second H-rich 2 S methanol to H 2 S flash to obtain the flash H-rich 2 S methanol;

[0015] The flash H-rich CO 2 methanol enters the heat exchanger Q, and the heat-exchanged H-rich CO 2 methanol enters the first cooler. After the first cooling, it is divided into two streams. The first stream of the cooled H-rich CO 2 methanol enters the upper part of the reabsorption tower for the first flash. The second stream of the cooled H-rich CO 2 methanol enters the second cooler. After the second cooling, it enters the middle part of the reabsorption tower for the second flash. The flash H-rich 2 S methanol enters the lower part of the reabsorption tower for the third flash to obtain semi-lean methanol and CO 2 product gas; and the obtained low H 2 S methanol is recycled and used for the 2 S absorption tower;

[0016] The semi-lean methanol is divided into two streams. The first stream of semi-lean methanol enters the heat exchanger. The heat-exchanged semi-lean methanol enters the stripping tower for stripping to obtain the low CO 2 methanol, which is recycled and used for the 2 CO absorption tower.

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

[0018] (1) For the method provided by the present invention, in order to further reduce the CO content in the semi-lean methanol and maximize the CO absorption capacity of the semi-lean methanol, the reabsorption process is optimized to strip the semi-lean methanol with nitrogen gas, so that the molar content of CO in the semi-lean methanol is further reduced to 5-7%, and low CO 2 content, maximize the CO 2 absorption capacity of the semi-lean methanol, optimize the reabsorption process to strip the semi-lean methanol with nitrogen gas, so that the CO 2 in the semi-lean methanol is further reduced to 5-7%, and low CO 2 methanol is obtained;

[0019] (2) For the method provided by the present invention, the low CO 2 methanol is returned and subjected to CO 2 absorption. First, with the improvement of the absorption capacity of the low CO 2 methanol and the reduction of the circulation amount, the operation cost of the pump can be reduced by about 15%, and the cross-sectional area of the CO 2 absorption tower can be reduced by about 5%; second, the low CO 2 methanol can replace part of the lean methanol, so that the CO 2The amount of lean methanol circulating in the absorber also decreased. The reduction in lean methanol flow is equivalent to reducing the amount of rich H 2 S methanol flow, the corresponding heat regeneration system energy consumption also decreases;

[0020] (3) The method provided by the present invention is to convert low H 2 S methanol is returned and H 2 S absorption, not only achieves low H 2 The recycling of S methanol also reduces H 2 The first CO-rich stream in the S absorption tower 2 The amount of methanol used is equivalent to reducing the need for thermal regeneration of H-rich 2 S methanol. Brief Description of the Figures

[0021] Figure 1 This is a schematic diagram of the structure of a synthetic gas purification device supporting a pulverized coal gasification device provided by the present invention.

[0022] Description of reference numerals

[0023] T-1, H 2 S absorption tower; T-2, CO 2 Absorption tower; T-3, flash tower; T-4, reabsorption tower; T-5, stripping tower; Q, heat exchanger; E-1, first cooler; E-2, second cooler; E-3, third cooler; E-4, fourth cooler; E-5, fifth cooler; P-1, first pump; P-2, second pump; P-3, third pump;

[0024] 1. Synthesis gas; 2. Low H 2 S methanol; 2-i, first strand low H 2 S methanol; 2-ii, second strand low H 2 S methanol; 3. First H-rich 2 S methanol; 4, CO rich 2 Methanol; 4-i, first stream rich in CO 2 Methanol; 4-ii, second stream rich in CO 2 Methanol; 5, second rich H 2 S methanol; 6. desulfurized gas; 7. containing CO 2 Methanol; 8, semi-lean methanol; 8-i, first stream of semi-lean methanol; 8-ii, second stream of semi-lean methanol; 9, lean methanol; 10, rich CO after flash evaporation 2 Methanol; 11, flash gas; 11-i, CO 2 Flash gas; 12, CO-rich after cooling 2 Methanol; 12-i, first stream cooled and enriched in CO 2 Methanol; 12-ii, the second stream is cooled and enriched in CO 2 Methanol; 13, low temperature rich H2 S methanol; 14. Rich H after flash evaporation 2 S methanol; 15. CO 2 Product gas; 16. Third rich H 2 S methanol; 17. Purified gas; 18. Tail gas; 19. Nitrogen; 20. Low CO 2 Methanol; 21. Rich CO after heat exchange 2 Methanol; 22. Semi-lean liquid methanol after heat exchange. Detailed implementation manners

[0025] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0026] In the present invention, without special circumstances, "first", "second", "third", "fourth" and "fifth" neither represent the order nor limit each material or step, but are only used to distinguish that these are not the same material or step. For example, the "first", "second", "third", "fourth" and "fifth" in "first cooling", "second cooling", "third cooling", "fourth cooling" and "fifth cooling" are only used to indicate that these are not the same cooling.

[0027] In the present invention, without special circumstances, the "top" of the container refers to the 0 - 10% height of the container from top to bottom; the "upper part" of the container refers to the 10 - 40% height of the container from top to bottom; the "middle part" of the container refers to the 40 - 60% height of the container from top to bottom; the "lower part" of the container refers to the 60 - 90% height of the container from top to bottom; the "bottom" of the container refers to the 90 - 100% height of the container from top to bottom.

[0028] The first aspect of the present invention provides a synthesis gas purification method for supporting a pulverized coal gasification device, and the method includes:

[0029] (1) Subject the synthesis gas to H 2 S absorption to obtain first rich H 2 S methanol, second rich H 2 S methanol and desulfurized gas; Subject the desulfurized gas to CO 2 absorption, and the obtained rich CO 2 methanol is divided into a first stream of rich CO 2 methanol and a second stream of rich CO 2 methanol;

[0030] (2) Subject the second stream of rich CO2 The methanol is subjected to CO 2 flash evaporation to obtain the CO-rich methanol after flash evaporation 2 ; the second H2S-rich methanol is subjected to H2S 2 flash evaporation to obtain the H2S-rich methanol after flash evaporation 2 ; 2 S methanol;

[0031] (3) The CO-rich methanol after flash evaporation is heat-exchanged with the first semi-lean methanol to obtain the heat-exchanged CO-rich methanol and the semi-lean methanol after heat exchange; the heat-exchanged CO-rich methanol is cooled for the first time, and the cooled CO-rich methanol is divided into two streams. The first stream of the cooled CO-rich methanol is subjected to the first flash evaporation, and the second stream of the cooled CO-rich methanol is cooled for the second time and then subjected to the second flash evaporation; the H2S-rich methanol after flash evaporation is subjected to the third flash evaporation; semi-lean methanol, low-H2S methanol and product gas are obtained; and the low-H2S methanol is returned and subjected to the H2S 2 absorption; 2 methanol and the semi-lean methanol after heat exchange; the heat-exchanged CO-rich methanol is cooled for the first time, and the cooled CO-rich methanol is divided into two streams. The first stream of the cooled CO-rich methanol is subjected to the first flash evaporation, and the second stream of the cooled CO-rich methanol is cooled for the second time and then subjected to the second flash evaporation; the H2S-rich methanol after flash evaporation is subjected to the third flash evaporation; semi-lean methanol, low-H2S methanol and product gas are obtained; and the low-H2S methanol is returned and subjected to the H2S 2 absorption; 2 methanol is divided into two streams. The first stream of the cooled CO-rich methanol is subjected to the first flash evaporation, and the second stream of the cooled CO-rich methanol is cooled for the second time and then subjected to the second flash evaporation; the H2S-rich methanol after flash evaporation is subjected to the third flash evaporation; semi-lean methanol, low-H2S methanol and product gas are obtained; and the low-H2S methanol is returned and subjected to the H2S 2 absorption; 2 methanol is cooled for the second time and then subjected to the second flash evaporation; the H2S-rich methanol after flash evaporation is subjected to the third flash evaporation; semi-lean methanol, low-H2S methanol and product gas are obtained; and the low-H2S methanol is returned and subjected to the H2S 2 absorption; 2 methanol and CO 2 product gas; and the low-H2S 2 methanol is returned and subjected to the H2S 2 absorption;

[0032] (4) The semi-lean methanol after heat exchange is contacted with nitrogen and stripped to obtain the low-CO 2 methanol, which is returned and subjected to the CO 2 absorption.

[0033] In some embodiments of the present invention, preferably, the first CO-rich 2 methanol is returned and subjected to the H2S 2 absorption. This not only further removes the acidic gases in the syngas, but also reduces the usage amount of the second CO-rich 2 methanol, and reduces the working loads of CO 2 flash evaporation and reabsorption.

[0034] In some embodiments of the present invention, preferably, the process of H2S 2 absorption includes: contacting the syngas with the first low-H2S 2 methanol for pre-H2S 2 absorption to obtain the first H2S-rich 2 methanol and the pre-washed syngas; contacting the pre-washed syngas, the second low-H2S 2 methanol and the first CO-rich 2 methanol for main H2S 2 absorption to obtain the second H2S-rich 2 methanol and the desulfurized gas.

[0035] In the present invention, the source of the syngas has a relatively wide selection range, as long as the syngas meets the above-mentioned limitations. Preferably, the syngas is selected from the waste heat boiler process or the quench process of pulverized coal gasification. Preferably, the molar content of H 2 S in the syngas is 0.3-0.4%, and the molar content of CO 2 is 40-50%; the temperature is -25°C to -15°C, and the pressure is 3.12-3.15 MPa(G).

[0036] In some embodiments of the present invention, preferably, the molar flow ratio of the syngas to the first stream of low-H 2 S methanol is 40-60:1, for example, 40:1, 50:1, 60:1, and any value within the range composed of any two values.

[0037] In the present invention, the pre-H 2 S absorption aims to remove impurities such as HCN and NH 3 in the syngas, as well as a small amount of H 2 S and CO 2 . Preferably, the molar content of H 2 S in the first rich-H 2 S methanol is 0.6-0.8%, and the molar content of CO 2 is 30-36%. In the present invention, the temperature of the first rich-H 2 S methanol is -25 to -15°C, and the pressure is 3.12-3.15 MPa(G).

[0038] In some embodiments of the present invention, preferably, the molar flow ratio of the syngas to the second stream of low-H 2 S methanol is 3-5:1; the molar flow ratio of the syngas to the first stream of rich-CO 2 methanol is 1.5-2.5:1.

[0039] In the present invention, the main H 2 S absorption aims to further remove H 2 S in the syngas, as well as a small amount of CO 2 . Preferably, the molar content of H 2 S in the second rich-H 2 S methanol is 0.4-0.6%, and the molar content of CO 2 is 27-32%. In the present invention, the temperature of the second rich-H 2 S methanol is -25 to -15°C, and the pressure is 3.12-3.15 MPa(G).

[0040] In some embodiments of the present invention, preferably, the H2 The molar content of S is 0.5 - 1 ppm, and the molar content of CO 2 is 32 - 36%; the temperature is -30 to -20 °C; the pressure is 3.05 - 3.1 MPa(G).

[0041] In the present invention, the low-H 2 S methanol is divided into two streams. Preferably, the low-H 2 S methanol is divided into a first stream of low-H 2 S methanol and a second stream of low-H 2 S methanol with a molar flow rate ratio of 1:13 - 15.

[0042] In some embodiments of the present invention, further preferably, the low-H 2 S methanol is pressurized to 3.5 - 4 MPa(G) for the first time and then divided into two streams.

[0043] In some embodiments of the present invention, preferably, the process of CO 2 absorption includes: contacting the desulfurized gas and the CO 2 -containing methanol and performing pre-CO 2 absorption to obtain the CO 2 -rich methanol and the pre-purified gas; contacting the pre-purified gas, the low-CO 2 -containing methanol and the lean methanol and performing main CO 2 absorption to obtain the purified gas.

[0044] In the present invention, the purpose of the pre-CO 2 absorption is to further remove CO 2 from the desulfurized gas. Preferably, the molar content of CO 2 in the CO 2 -rich methanol is 15 - 20%, and the molar content of H 2 S is 0.1 - 0.5 ppm; the temperature is -23 to -18 °C, and the pressure is 3.05 - 3.1 MPa(G).

[0045] In some embodiments of the present invention, further preferably, the CO 2 -containing methanol is cooled to -36 to -33 °C for the fifth time and then the pre-CO 2 absorption is carried out.

[0046] In some embodiments of the present invention, preferably, the CO 2 -rich methanol is divided into a first stream of CO 2 -rich methanol and a second stream of CO 2 -rich methanol with a molar flow rate ratio of 1:3 - 3.5.

[0047] In the present invention, without special instructions, the first stream of CO-rich2 The methanol returns and undergoes the main H 2 S absorption, and the second rich CO 2 The methanol undergoes the CO 2 flashing.

[0048] In some embodiments of the present invention, further preferably, the first rich methanol is sequentially pressurized to 3.5 - 4 MPa(G) by a second stage, cooled to -50 to -45 °C in a fourth stage, and then undergoes the main H 2 S absorption.

[0049] In some embodiments of the present invention, preferably, the molar flow rate ratio of the desulfurized gas to the methanol containing CO 2 is 1:1.5 - 2.5.

[0050] In some embodiments of the present invention, preferably, the molar flow rate ratio of the purified gas to the low CO 2 methanol is 1:1.5 - 1.8, for example, 1.5, 1.6, 1.7, 1.8, and any value within the range composed of any two values.

[0051] In some embodiments of the present invention, preferably, the molar flow rate ratio of the purified gas to the lean methanol is 1:1.4 - 1.7.

[0052] In some embodiments of the present invention, preferably, the H 2 S molar content in the purified gas < 0.1 ppm, and the CO 2 molar content < 20 ppm; the temperature is -55 to -50 °C, and the pressure is 2.8 - 2.95 MPa(G).

[0053] In the present invention, the CO 2 flashing removes the second rich CO 2 from the methanol, and the CO 2 flashing gas, and the H 2 S flashing aims to remove the second rich H 2 S from the methanol, and the H 2 S flashing gas. Preferably, the pressures of the CO 2 flashing and the H 2 S flashing are each independently selected from 0.8 - 1 MPa(G).

[0054] In some embodiments of the present invention, preferably, the molar content of H 2 S in the flashed rich CO 2 methanol is 0.1 - 0.5 ppm, and the molar content of CO 2 is 14.5 - 19.5%; the temperature is -23.5 to -18.5 °C.

[0055] In some embodiments of the present invention, preferably, after flashing, the H-rich 2 in the H2S methanol, the 2 molar content of H2S is 0.4 - 0.6%, and the 2 molar content of CO is 23 - 28%; the temperature is -35 to -30 °C.

[0056] In some embodiments of the present invention, preferably, after the second H-rich 2 methanol is cooled to -34 to -29 °C by the third cooler, the H2S 2 flashing is carried out.

[0057] In some embodiments of the present invention, preferably, the CO 2 flash gas obtained after flashing is mixed with the H2S 2 flash gas obtained after H2S flashing, and then washed with the low-temperature H-rich 2 methanol to obtain a flash gas. With such a setting, a flash gas with a low CO 2 concentration is obtained. 2 concentration is obtained. 2 concentration is obtained.

[0058] In some embodiments of the present invention, preferably, in the flash gas, the 2 molar content of H2S is 81 - 87%, the 2 molar content of CO is 6 - 11%, and the molar content of CO is 3 - 7%; the temperature is -55 °C to -50 °C, and the pressure is 0.8 - 1 MPa(G), and it is sent to the subsequent process for treatment. In the present invention, in addition to H2S 2 , CO 2 and CO, the flash gas also contains other impurity components.

[0059] In some embodiments of the present invention, preferably, in the low-temperature H-rich 2 methanol, the 2 molar content of H2S is 0.6 - 0.9%, and the 2 molar content of CO is 1 - 5%; the temperature is -60 to -55 °C.

[0060] In the present invention, without special instructions, the CO-rich 2 methanol after flashing exchanges heat with the first semi-lean methanol to obtain the heat-exchanged CO-rich 2 methanol transformed from the CO-rich 2 methanol after flashing, and the heat-exchanged semi-lean methanol transformed from the first semi-lean methanol.

[0061] In some embodiments of the present invention, preferably, the heat-exchanged CO-rich 2The temperature of the methanol is -27 to -22 °C; the temperature of the semi-lean methanol after heat exchange is -50 to -45 °C.

[0062] In some embodiments of the present invention, preferably, the temperature of the rich CO 2 after cooling of the methanol is -36 to -33 °C.

[0063] In some embodiments of the present invention, more preferably, the first stream of rich CO 2 after cooling of the methanol and the second stream of rich CO 2 after cooling of the methanol have a molar flow rate ratio of 3.5 - 4:1.

[0064] In the present invention, the first flash evaporation is intended to flash evaporate the first stream of rich CO 2 after cooling of the methanol to obtain a first CO 2 product gas and semi-lean methanol. Preferably, the pressure of the first flash evaporation is 0.05 - 0.08 MPa(G).

[0065] In some embodiments of the present invention, preferably, the molar content of CO 2 in the semi-lean methanol is 10 - 13%, the molar content of H 2 S is ≤ 0.5 ppm; the temperature is -53 to -48 °C; the pressure is 0.05 - 0.08 MPa(G).

[0066] In the present invention, the semi-lean methanol is divided into two streams. The first stream of semi-lean methanol is stripped after heat exchange to obtain low-CO 2 methanol; the second stream of semi-lean methanol is sent to subsequent processes for use.

[0067] In some embodiments of the present invention, preferably, the semi-lean methanol is divided into a first stream of semi-lean methanol and a second stream of semi-lean methanol with a molar flow rate ratio of 3.6 - 4:1.

[0068] In the present invention, the second cooling is intended to further reduce the temperature of the second stream of rich CO 2 after cooling of the methanol. Preferably, the temperature of the material after the second cooling is -55 to -50 °C.

[0069] In the present invention, the second flash evaporation is intended to flash evaporate the material after the second cooling to obtain a second CO 2 product gas and the flashed solution. Preferably, the pressure of the second flash evaporation is 0.06 - 0.09 MPa(G).

[0070] In the present invention, the third flash evaporation is intended to flash evaporate the flashed rich H 2 S methanol to obtain a third rich H 2 S methanol and the H 2S flashing vapor. Preferably, the pressure of the third flash is 0.12 - 0.16 MPa (G).

[0071] In a specific embodiment of the present invention, the first flash yields the semi-lean methanol and the first CO 2 product gas; the second flash yields the second CO 2 product gas and the flashed solution; the third flash yields the H 2 S flashing vapor and the third H 2 S-rich methanol; wherein, the H 2 S flashing vapor and the flashed solution are washed to obtain the third CO 2 product gas and the low H 2 S methanol; wherein, the CO 2 product gas includes the first CO 2 product gas, the second CO 2 product gas and the third CO 2 product gas.

[0072] In some embodiments of the present invention, preferably, the H 2 S molar content in the CO 2 product gas < 1 ppm, and the CO 2 molar content is 99.3 - 99.7%; temperature -55°C to -50°C, pressure 0.05 - 0.08 MPa (G).

[0073] In some embodiments of the present invention, preferably, the H 2 S molar content in the low H 2 S methanol is 0.2 - 0.5%, and the CO 2 molar content is 15 - 20%; temperature is -55 to -50°C, pressure is 0.13 - 0.17 MPa (G).

[0074] In some embodiments of the present invention, preferably, the H 2 S molar content in the third H 2 S-rich methanol is 0.4 - 0.6%, and the CO 2 molar content is 13 - 17%; temperature is -60 to -55°C; pressure is 0.13 - 0.17 MPa (G).

[0075] In the present invention, the stripping aims to further reduce the CO 2 concentration in the semi-lean methanol to obtain low CO 2 methanol. Preferably, the H 2 S molar content in the low CO 2 methanol ≤ 0.5 ppm, and the CO 2The molar content is 5-7%; the temperature is -58 to -53 °C; the pressure is 0.15-0.25 MPa(G).

[0076] In some embodiments of the present invention, preferably, the molar flow ratio of the semi-lean methanol and nitrogen after heat exchange is 85-100:1, for example, 85:1, 90:1, 95:1, 100:1, and any value within the range composed of any two values.

[0077] In some embodiments of the present invention, preferably, the stripping pressure is 0.15-0.25 MPa(G).

[0078] In some embodiments of the present invention, preferably, the tail gas obtained from the stripping also has the molar content of H 2 S ≤ 0.5 ppm, and the molar content of CO 2 is 80-85%; the temperature is -53 to -48 °C; the pressure is 0.15-0.25 MPa(G).

[0079] In some embodiments of the present invention, preferably, the method further includes: boosting the low-CO 2 methanol to 3.5-4 MPa(G) through a third booster and returning it for the CO 2 absorption.

[0080] The structural schematic diagram of a syngas purification device supporting a pulverized coal gasification device provided by the second aspect of the present invention is as Figure 1 shown, and it can be seen from Figure 1 that the device includes an H 2 S absorption tower T-1, a CO 2 absorption tower T-2, a flash tower T-3, a reabsorption tower T-4, and a stripping tower T-5, which are connected in sequence, as well as a heat exchanger Q, a first cooler E-1, and a second cooler E-2;

[0081] The H 2 S absorption tower T-1 is used for H 2 S absorption of the syngas 1 to obtain a first rich H 2 S methanol 3, a second rich H 2 S methanol 5, and a desulfurized gas 6; the CO 2 absorption tower T-2 is used for CO 2 absorption of the desulfurized gas 6 to obtain the rich CO 2 methanol 4, which is divided into a first stream of rich CO 2 methanol 4-i and a second stream of rich CO 2 methanol 4-ii;

[0082] The flash tower T-3 includes a CO 2 flash section provided on it and an H2 S flash evaporation section, CO 2 The flash evaporation section is used to subject the second rich CO 2 methanol 4-ii to CO 2 flash evaporation to obtain the flash-evaporated rich CO 2 methanol 10, H 2 The S flash evaporation section is used to subject the second rich H 2 S methanol 5 to H 2 S flash evaporation to obtain the flash-evaporated rich H 2 S methanol 14;

[0083] The flash-evaporated rich CO 2 methanol 10 enters the heat exchanger Q, and the heat-exchanged rich CO 2 methanol 21 enters the first cooler E-1. After the first cooling, it is divided into two streams. The first stream is the cooled rich CO 2 methanol 12-i enters the upper part of the reabsorption tower T-4 for the first flash evaporation. The second stream is the cooled rich CO 2 methanol 12-ii enters the second cooler E-2. After the second cooling, it enters the middle part of the reabsorption tower T-4 for the second flash evaporation. The flash-evaporated rich H 2 S methanol 14 enters the lower part of the reabsorption tower T-4 for the third flash evaporation to obtain semi-lean liquid methanol 8 and CO 2 product gas 15, and the obtained low H 2 S methanol 2 is recycled and used for the H 2 S absorption tower T-1;

[0084] The semi-lean liquid methanol 8 is divided into two streams. The first stream, semi-lean liquid methanol 8-i, enters the heat exchanger Q. The heat-exchanged semi-lean liquid methanol 22 enters the stripping tower T-5 for stripping to obtain the low CO 2 methanol 20 is recycled and used for the CO 2 absorption tower T-2.

[0085] In the present invention, as Figure 1 shown, the CO 2 rich CO outlet of the absorption tower T-2 is connected to the H 2 S absorption tower T-1 for recycling the first rich CO 2 methanol 4-i to the H 2 S absorption tower T-1. 2 S absorption tower T-1.

[0086] In the present invention, as Figure 1 shown, the H 2 S absorption tower T-1 includes a pre-H 2 S absorption section provided below and a main H 2 S absorption section provided above.

[0087] In the present invention, H 2 The H 2 S absorption tower is divided into a pre-H 2 S absorption section and a main H 2 S absorption section from bottom to top; specifically, the pre-H 2 S absorption section pre-absorbs H 2 S, HCN, and NH 3 in the syngas through the first stream of low-H 2 S methanol; the main H 2 S absorption section absorbs H 2 S and CO 2 in the pre-washed syngas by introducing a second stream of low-H 2 S methanol, realizing the recycling of the low-H 2 S methanol, reducing the usage amount of the first stream of CO 2 -rich methanol in the main H 2 S absorption section, which is equivalent to reducing the second H 2 -rich S methanol that needs to be thermally regenerated; in addition, such a setting correspondingly reduces the working load of the subsequent CO 2 absorption tower, which is also of positive significance for reducing the usage amounts of lean methanol and low-CO 2 methanol in the CO

[0088] In the present invention, as Figure 1 shown, in the H 2 S absorption tower T-1, the pre-H 2 S absorption section and the main H 2 S absorption section are connected by lifting holes; the pre-H 2 S absorption section is connected to the low-H 2 S methanol outlet of the reabsorption tower T-4, used to contact the syngas 1 with the first stream of low-H 2 S methanol 2-i and perform pre-H 2 S absorption to obtain the first H 2 -rich S methanol 3 and the pre-washed syngas; the main H 2 S absorption section is connected to the low-H 2 S methanol outlet of the reabsorption tower T-4 and the CO 2 -rich methanol outlet of the CO 2 absorption tower T-2, used to sequentially contact the pre-washed syngas with the second stream of low-H 2 S methanol 2-ii and the first stream of CO 2 -rich methanol 4-i and perform main H 2 S absorption to obtain the desulfurized gas 6 and the second H 2 -rich S methanol 5.

[0089] In some embodiments of the present invention, preferably, the H2 In the S absorption tower T-1, pre-H 2 The number of trays in the S absorption section is 12 - 15 trays, main-H 2 The number of trays in the S absorption section is 60 - 80 trays.

[0090] In the present invention, without special circumstances, the pre-H 2 In the S absorption section, syngas and the first low-H 2 The contact mode between the syngas and the first low-H S methanol is preferably selected from the countercurrent contact between the syngas and the first low-H 2 S methanol, that is, the syngas enters from the bottom of the pre-H 2 S absorption section, and the first low-H 2 S methanol enters from the upper part of the pre-H 2 S absorption section.

[0091] In the present invention, as Figure 1 shown, the CO 2 Absorption tower T-2 includes a pre-CO absorption section arranged below and a main-CO absorption section arranged above; the pre-CO absorption section and the main-CO absorption section are connected by lifting holes, wherein the upper part of the pre-CO absorption section is connected to the lower part of the main-CO absorption section for contacting the desulfurized gas 6 with the CO-containing methanol 7 and performing pre-CO absorption to obtain the rich CO 2 Absorption section and the main-CO 2 Absorption section; the pre-CO 2 Absorption section and the main-CO 2 Absorption section are connected by lifting holes, where the upper part of the pre-CO absorption section is connected to the lower part of the main-CO absorption section for contacting the desulfurized gas 6 with the CO-containing methanol 7 and performing pre-CO absorption to obtain the rich CO 2 Absorption section is connected to the lower part of the main-CO 2 Absorption section to contact the desulfurized gas 6 with the CO-containing methanol 7 and perform pre-CO absorption to obtain the rich CO 2 Methanol 7 contact and perform pre-CO 2 Absorption to obtain the rich CO 2 Methanol 4 and pre-purified gas; the main-CO 2 Absorption section is connected to the low-CO methanol outlet of the stripping tower T-5 and the lean methanol 9 from the subsequent process for contacting the pre-purified gas with the low-CO 2 Methanol 20 and lean methanol 9 in sequence and performing main-CO 2 Absorption to obtain the purified gas 17 and the CO-containing 2 Methanol 7. 2 Methanol 7.

[0092] In some embodiments of the present invention, preferably, in the CO 2 Absorption tower T-2, the number of trays in the pre-CO 2 Absorption section is 8 - 10 trays, and the number of trays in the main-CO 2 Absorption section is 70 - 90 trays.

[0093] In the present invention, without special circumstances, the pre-CO absorption section of the CO absorption tower, the desulfurized gas 6 and the CO-containing 2 Absorption section of the CO absorption tower, the desulfurized gas 6 and the CO-containing 2 Absorption section, the desulfurized gas 6 and the CO-containing methanol 2The contacting mode of methanol 7 is preferably selected from the desulfurized gas 6 and the CO-containing 2 countercurrent contact with methanol 7; that is, the desulfurized gas 6 enters from the bottom of the pre-CO 2 absorption section, and the CO-containing 2 methanol 7 enters from the upper part of the pre-CO 2 absorption section.

[0094] In the present invention, as Figure 1 shown, in the flash tower T-3, the top of the CO 2 flash section is connected to the upper part of the H 2 S flash section, which is used to mix the CO 2 flash gas 11-i obtained by the CO 2 flash with the H 2 S flash gas obtained by the H 2 S flash. After mixing, it is washed with the low-temperature H-rich 2 S methanol 13 to obtain the flash gas 11.

[0095] In the device provided by the present invention, the reabsorption tower T-4 is divided into an upper part, a middle part and a lower part from top to bottom. By optimizing the internal structure of the CO 2 reabsorption, the flash solution obtained after the second flash of the second cooled CO-rich 2 methanol is realized to be absorbed by the H-containing 2 S flash gas generated by the third flash of the flash-rich H 2 S methanol, but it does not mix with the third H-rich 2 S methanol, and low-H 2 S methanol is obtained, creating conditions for the reuse of this low-H 2 S methanol.

[0096] In the present invention, as Figure 1 shown, the upper part and the middle part of the reabsorption tower T-4 are connected by lift holes, and the middle part and the lower part are also connected by lift holes. Specifically, the upper part is used for the first flash of the first cooled CO-rich 2 methanol 12-i to obtain semi-lean liquid methanol 8 and the first CO 2 product gas; the middle part is used for the second flash of the second cooled CO-rich 2 methanol 12-ii after the second cooling to obtain the flash solution and the second CO 2 product gas; the lower part is used for the third flash of the flash-rich H 2 S methanol 14 to obtain the third H-rich 2 S methanol 16 and the H-containing 2 S flash gas; among them, the H-containing 2 S flash gas and the flash solution are washed to obtain low-H 2S methanol 2 and the third CO 2 Product gas; CO 2 Product gas 15 includes the first CO 2 Product gas, the second CO 2 Product gas and the third CO 2 Product gas.

[0097] In the present invention, as Figure 1 shown, the stripping column T-5 is used for counter-current contact between the semi-lean methanol 22 after heat exchange and nitrogen 19 and stripping to obtain tail gas 18 and low-CO 2 methanol 20.

[0098] In the present invention, as Figure 1 shown, the device further includes: a first pump P-1 is provided on the pipeline connecting the low-H 2 S methanol outlet of the reabsorption column T-4 and the H 2 S absorption column T-1, and is used for boosting the low-H 2 S methanol 2 after the first pressurization and performing the H 2 S absorption.

[0099] In the present invention, as Figure 1 shown, in the direction of material flow, connecting the CO 2 rich CO outlet of the absorption column T-2 and the H 2 S absorption column T-1, a second pump P-2 and a fourth cooler E-4 are sequentially provided on the pipeline, and are used for sequentially boosting and cooling the first stream of rich CO 2 methanol 4-i after the second pressurization and the fourth cooling and performing the H 2 S absorption. 2 S absorption.

[0100] In the present invention, as Figure 1 shown, in the direction of material flow, in the CO 2 absorption column T-2, a fifth cooler E-5 is provided on the pipeline connecting the main CO 2 absorption section and the pre-CO 2 absorption section, and is used for cooling the CO-containing 2 methanol after the fifth cooling and performing the pre-CO 2 absorption.

[0101] In the present invention, as Figure 1 shown, a third cooler E-3 is provided on the pipeline connecting the main H 2 S absorption section and the H 2 S flash section, and is used for cooling the second rich H 2 S methanol 5 after the third cooling and performing the H 2 S flash.

[0102] The present invention will be described in detail below with reference to embodiments.

[0103] Embodiment 1

[0104] The syngas purification device for a coal powder gasification device is as Figure 1 shown, and it can be seen from Figure 1 that this device includes: an H 2 S absorption tower T-1, a CO 2 absorption tower T-2, a flash tower T-3, a reabsorption tower T-4, and a stripping tower T-5, which are connected in sequence, a heat exchanger Q, 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, as well as a first pump P-1, a second pump P-2, and a third pump P-3;

[0105] The H 2 S absorption tower T-1 includes a pre-H 2 S absorption section provided at the bottom and a main H 2 S absorption section provided at the top; the CO 2 absorption tower T-2 includes a pre-CO 2 absorption section provided at the bottom and a main CO 2 absorption section provided at the top; the flash tower T-3 includes a CO 2 flash section provided at the top and an H 2 S flash section provided at the bottom.

[0106] The syngas purification method for a coal powder gasification device includes:

[0107] (1) Mixing syngas 1 (the molar content of H 2 S is 0.3 - 0.4%, the molar content of CO 2 is 40 - 50%; the temperature is -25 to -15 °C, and the pressure is 3.12 - 3.15 MPa (G)) and the first stream of low-H 2 S methanol 2-i in a countercurrent contact with a molar flow ratio of 40 - 60:1 and performing pre-H 2 S absorption to obtain the first rich-H 2 S methanol 3 (the molar content of H 2 S is 0.6 - 0.8%, the molar content of CO 2 is 30 - 36%) and the pre-washed syngas;

[0108] Sequentially contacting the above pre-washed syngas with the second stream of low-H 2 S methanol 2-ii and the first stream of rich-CO 2 methanol 4-i in a countercurrent contact and performing main-H 2 S absorption to obtain the desulfurized gas 6 (the molar content of H 2 S is 0.5 - 1 ppm, the molar content of CO 2The molar content is 32 - 36%; the temperature is -30 to -20 °C; the pressure is 3.05 - 3.1 MPa(G)) and the second H-rich 2 S methanol 5 (H 2 The molar content of S is 0.4 - 0.6%, and the CO 2 The molar content is 27 - 32%);

[0109] Among them, after the low H 2 S methanol 2 is pressurized to 3.5 - 4 MPa(G), and is divided into a first low H with a molar flow ratio of 1:13 - 15 2 S methanol 2-i and a second low H 2 S methanol 2-ii; the molar flow ratio of syngas 1 and the second low H 2 S methanol 2-ii is 3 - 5:1; the molar flow ratio of syngas 1 and the first CO-rich 2 Methanol 4-i is 1.5 - 2.5:1;

[0110] The above desulfurized gas 6 and the CO-containing 2 Methanol 7 (cooled to -36 to -33 °C) is in countercurrent contact at a molar flow ratio of 1:1.5 - 2.5 and undergoes pre-CO 2 Absorption to obtain CO-rich 2 Methanol 4 (CO 2 The molar content is 15 - 20%, H 2 The molar content of S is 0.1 - 0.5 ppm; the temperature is -23 to -18 °C, and the pressure is 3.05 - 3.1 MPa(G)) and the pre-purified gas. Among them, the CO-rich 2 Methanol is divided into a first CO-rich 2 Methanol 4-i and a second CO-rich 2 Methanol 4-ii; the first CO-rich 2 Methanol 4-i is pressurized to 3.5 - 4 MPa(G), cooled to -50 to -45 °C, and sent to the main CO 2 Absorption section;

[0111] The above pre-purified gas is successively in countercurrent contact with low CO 2 Methanol 20 and lean methanol 9 (CO 2 The molar content is 0%, H 2 The molar content of S is 0%) and undergoes main CO 2 Absorption to obtain purified gas 17 (H 2 The molar content of S < 0.1 ppm, and the CO 2 The molar content < 20 ppm; the temperature is -55 to -50 °C; the pressure is 2.8 - 2.95 MPa(G));

[0112] Among them, the purified gas 17 and the low CO2 The molar flow rate ratio of methanol 20 is 1:1.5 - 1.8; the molar flow rate ratio of the purified gas 17 and the lean methanol 9 is 1:1.4 - 1.7;

[0113] (2) Subject the second rich CO 2 methanol 4-ii to CO 2 flash evaporation (at a pressure of 0.8 - 1 MPa(G)) to obtain the rich CO 2 methanol 10 (H 2 The molar content of S is 0.1 - 0.5 ppm, and the molar content of CO 2 is 14.5 - 19.5%; the temperature is -23.5 to -18.5 °C) and CO 2 flash vapor 11-i; subject the second rich H 2 S methanol 5 to the third cooling to -34 to -29 °C and then conduct H 2 S flash evaporation (at a pressure of 0.8 - 1 MPa(G)) to obtain the rich H 2 S methanol 14 (H 2 The molar content of S is 0.4 - 0.6%, and the molar content of CO 2 is 23 - 28%; the temperature is -35 to -30 °C) and H 2 S flash vapor; mix the CO 2 flash vapor and the H 2 S flash vapor, and then wash it with the low-temperature rich H 2 S methanol 13 (H 2 The molar content of S is 0.6 - 0.9%, and the molar content of CO 2 is 1 - 5%; the temperature is -60 to -55 °C) to obtain the flash vapor 11 (H 2 The molar content is 81 - 87%, the molar content of CO 2 is 6 - 11%, and the molar content of CO is 3 - 7%; the temperature is -55 °C to -50 °C, and the pressure is 0.8 - 1 MPa(G)) and send it to the subsequent process for treatment;

[0114] (3) Exchange heat between the rich CO 2 methanol 10 after the above flash evaporation and the first semi-lean liquid methanol 8-i to obtain the rich CO 2 methanol 21 (temperature is -27 to -22 °C) and the heat-exchanged semi-lean liquid methanol 22 (temperature is -50 to -45 °C);

[0115] Subject the rich CO 2 methanol 21 after the above heat exchange to the first cooling to obtain the cooled rich CO 2 methanol 12 (temperature is -36 to -33 °C), which is divided into the first cooled rich CO with a molar flow rate ratio of 3.5 - 4:1 2Methanol 12-i and the second stream of cooled CO-rich 2 Methanol 12-ii;

[0116] Subject the above-mentioned first stream of cooled CO-rich 2 Methanol 12-i to a first flash (at a pressure of 0.05 - 0.08 MPa(G)) to obtain a first CO 2 product gas and semi-lean methanol 8 (with a molar content of CO 2 of 10 - 13%, and a molar content of H 2 S of < 0.5 ppm; temperature of -53 to -48 °C; pressure of 0.05 - 0.08 MPa(G)), where the above-mentioned semi-lean methanol 8 is divided into a first stream of semi-lean methanol 8-i and a second stream of semi-lean methanol 8-ii with a molar flow ratio of 3.6 - 4:1;

[0117] Subject the above-mentioned second stream of cooled CO-rich 2 Methanol 12-ii to a second cooling (temperature of -55 to -50 °C) and then to a second flash (at a pressure of 0.06 - 0.09 MPa(G)) to obtain a second CO 2 product gas and the flashed solution; subject the above-mentioned flashed H 2 S-rich methanol 14 to a third flash (at a pressure of 0.12 - 0.16 MPa(G)) to obtain an H 2 S-containing flash gas and a third H 2 S-rich methanol 16 (with a molar content of H 2 S of 0.4 - 0.6%, and a molar content of CO 2 of 13 - 17%; temperature of -60 to -55 °C; pressure of 0.13 - 0.17 MPa(G));

[0118] Among them, wash the above-mentioned H 2 S-containing flash gas and the flashed solution to obtain a third CO 2 product gas and low-H 2 S methanol 2 (with a molar content of H 2 S of 0.2 - 0.5%, and a molar content of CO 2 of 15 - 20%; temperature of -55 to -50 °C, pressure of 0.13 - 0.17 MPa(G)); among them, the CO 2 product gas 15 (with a molar content of H 2 S of < 1 ppm, and a molar content of CO 2 of 99.3 - 99.7%; temperature of -55 °C to -50 °C, pressure of 0.05 - 0.08 MPa(G)) includes the first CO 2 product gas, the second CO 2 product gas and the third CO 2 product gas;

[0119] (4) Contact the post-heat-exchanged semi-lean methanol 22 and nitrogen 19 at a molar flow rate ratio of 85 - 100:1 and perform stripping (pressure is 0.15 - 0.25 MPa(G)) to obtain low-CO 2 methanol 20 (H 2 The molar content of S ≤ 0.5 ppm, and the molar content of CO 2 is 5 - 7%; the temperature is -58 to -53 °C; the pressure is increased from 0.15 - 0.25 MPa(G) to 3.5 - 4 MPa(G), then returned and the above main CO 2 absorption is carried out, and the obtained tail gas 18 (H 2 The molar content of S ≤ 0.5 ppm, and the molar content of CO 2 is 80 - 85%; the temperature is -53 to -48 °C; the pressure is 0.15 - 0.25 MPa(G)).

[0120] Comparative Example 1

[0121] Taking the hydrogen production unit using pulverized coal gasification for gas production as an example, the effective gas (H 2 +CO) entering the low-temperature methanol washing unit is 161000 Nm 3 / h. Based on this benchmark, the main technical parameters of the lean-semi-lean liquid process (i.e., CN201110260570.0 discloses a low-temperature methanol washing process and a syngas purification process for a supporting pulverized coal gasification unit) are compared in Table 1.

[0122] Table 1

[0123] Example 1 Comparative Example 1 Lean methanol circulation rate 11500 kmol / h 13000 kmol / h <![CDATA[Low CO 2 methanol recycle rate]]> 9500 kmol / h 12000 kmol / h <![CDATA[H 2 The amount of methanol used for the rich CO in the S absorption tower 2 in the S absorption tower 6200 kmol / h 7000 kmol / h External cold energy consumption 8800 KW / h 10000 KW / h Electric energy consumption 3000 KW / h 3500 KW / h <![CDATA[CO 2 Absorption tower diameter]]> 4500 mm 4600 mm

[0124] It can be seen from the results in Table 1 that taking the hydrogen production unit based on pulverized coal gasification for gas production as an example, for the syngas purification method of the supporting pulverized coal gasification unit provided in Example 1, the lean methanol circulation volume is 88.5% of the lean methanol circulation volume in Comparative Example 1 (lean-semi-lean liquid process), and the low-CO 2 methanol circulation volume is 79.2% of the semi-lean methanol circulation volume in Comparative Example 1 (lean-semi-lean liquid process), and the consumption of rich CO 2 methanol in the H 2 S absorption tower is 88.6% of the consumption of rich CO 2 methanol in Comparative Example 1 (lean-semi-lean liquid process), and the power consumption of the pumps is 85.7% of the consumption in Comparative Example 1 (lean-semi-lean liquid process), with a cumulative reduction in external cold energy consumption of 1200 KW / h, and the overall energy-saving effect is significant.

[0125] In addition, the diameter of the CO 2 absorption tower is that of the CO 297.8% of the diameter of the absorption tower, that is, compared with Comparative Example 1, CO is reduced 2 The cross-sectional area of the absorption tower is 4.84%.

[0126] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for purifying synthesis gas of a pulverized coal gasification device, characterized in that: The method comprises: (1) subjecting the synthesis gas to H2S absorption to obtain a first stream of H2S-rich methanol, a second stream of H2S-rich methanol and a desulfurized gas; subjecting the desulfurized gas to CO2 absorption to obtain a first stream of CO2-rich methanol and a second stream of CO2-rich methanol; (2) subjecting the second stream of CO2-rich methanol to CO2 flash evaporation to obtain flashed CO2-rich methanol; subjecting the second stream of H2S-rich methanol to H2S flash evaporation to obtain flashed H2S-rich methanol; (3) exchanging heat between the flashed CO2-rich methanol and the first stream of semi-lean methanol to obtain heat-exchanged CO2-rich methanol and heat-exchanged semi-lean methanol; subjecting the heat-exchanged CO2-rich methanol to a first cooling to obtain cooled CO2-rich methanol divided into two streams, subjecting the first stream of cooled CO2-rich methanol to a first flash, and subjecting the second stream of cooled CO2-rich methanol to a second flash after a second cooling; subjecting the flashed H2S-rich methanol to a third flash; obtaining semi-lean methanol, low H2S methanol and CO2 product gas, and returning the low H2S methanol to the H2S absorption; (4) The semi-lean liquid methanol after the heat exchange is contacted with nitrogen and stripped, and the obtained low-CO2 methanol is returned and subjected to the CO2 absorption.

2. The method according to claim 1, wherein: In step (1), Returning the first stream of CO2-rich methanol and performing the H2S absorption; And / or, the H2S absorption process includes: contacting the synthesis gas with a first stream of low H2S methanol and performing pre-H2S absorption to obtain the first H2S-rich methanol and pre-washed synthesis gas; contacting the pre-washed synthesis gas, the second stream of low H2S methanol and the first stream of CO2-rich methanol and performing main H2S absorption to obtain the second H2S-rich methanol and desulfurized gas; and / or, the molar content of H2S in the second H2S-rich methanol is 0.4-0.6%, and the molar content of CO2 is 27-32%; and / or, the molar content of H2S in the desulfurized gas is 0.5-1ppm, the molar content of CO2 is 32-36%; the temperature is -30 to -20°C; the pressure is 3.05-3.1MPa(G); and / or, the low H2S methanol is divided into a first stream of low H2S methanol and a second stream of low H2S methanol at a molar flow ratio of 1:13-15; And / or, the CO2 absorption process includes: contacting the desulfurized gas with CO2-containing methanol and performing pre-CO2 absorption to obtain the CO2-rich methanol and pre-purified gas; contacting the pre-purified gas, low-CO2 methanol and lean methanol and performing main CO2 absorption to obtain purified gas; and / or, the molar content of CO2 in the CO2-rich methanol is 15-20%, the molar content of H2S is 0.1-0.5 ppm; the temperature is -23 to -18°C, and the pressure is 3.05-3.1 MPa(G); and / or, the CO2-rich methanol is divided into a first stream of CO2-rich methanol and a second stream of CO2-rich methanol at a molar flow ratio of 1:3-3.5; And / or, the molar content of H2S in the purified gas is less than 0.1 ppm, and the molar content of CO2 is less than 20 ppm; the temperature is -55 to -50°C, and the pressure is 2.8-2.95 MPa(G).

3. The method according to claim 2, wherein: After the low H2S methanol is first pressurized to 3.5-4 MPa(G), it is divided into two streams; and / or, the first stream of rich methanol is successively pressurized to 3.5-4 MPa(G) by a second step, and cooled to -50 to -45°C by a fourth step, and then the main H2S absorption is performed; And / or, the CO2-containing methanol is cooled to -36 to -33°C for a fifth time before the pre-CO2 absorption is performed.

4. The method according to any one of claims 1 to 3, wherein: In step (2), The pressures of the CO2 flash and H2S flash are each independently selected from 0.8-1 MPa(G); and / or, the molar content of H2S in the CO2-rich methanol after the flash evaporation is 0.1-0.5 ppm, the molar content of CO2 is 14.5-19.5%; the temperature is -23.5 to -18.5°C; and / or, the molar content of H2S in the H2S-rich methanol after the flash evaporation is 0.4-0.6%, and the molar content of CO2 is 23-28%; the temperature is -35 to -30°C; and / or, subjecting the second H2S-rich methanol to a third cooling process to -34 to -29°C, and then performing the H2S flash evaporation; And / or, the CO2 flash gas obtained after the CO2 flash evaporation is mixed with the H2S flash gas obtained after the H2S flash evaporation, and then washed with low-temperature H2S-rich methanol to obtain flash gas.

5. The method according to any one of claims 1 to 4, wherein: In step (3), The temperature of the CO2-rich methanol after the heat exchange is -27 to -22°C; the temperature of the semi-lean methanol after the heat exchange is -50 to -45°C; and / or, the temperature of the CO2-rich methanol after cooling is -36 to -33°C; and / or, the molar flow ratio of the first stream of cooled CO2-rich methanol to the second stream of cooled CO2-rich methanol is 3.5-4:1; And / or, the pressure of the first flash evaporation is 0.05-0.08 MPa(G); and / or, the molar content of CO2 in the semi-lean methanol is 10-13%, the molar content of H2S is ≤0.5ppm; the temperature is -53 to -48°C; the pressure is 0.05-0.08MPa(G); and / or, the semi-lean methanol is divided into a first stream of semi-lean methanol and a second stream of semi-lean methanol with a molar flow ratio of 3.6-4:1; And / or, the temperature of the second cooled material is -55 to -50°C; And / or, the pressure of the second flash evaporation is 0.06-0.09 MPa(G); And / or, the pressure of the third flash evaporation is 0.12-0.16 MPa(G); And / or, the first flash evaporation obtains the semi-lean methanol and the first CO2 product gas; the second flash evaporation obtains the second CO2 product gas and a flashed solution; the third flash evaporation obtains H2S-containing flash gas and a third H2S-rich methanol; wherein the H2S-containing flash gas and the flashed solution are washed to obtain a third CO2 product gas and the low-H2S methanol; wherein the CO2 product gas includes the first CO2 product gas, the second CO2 product gas and the third CO2 product gas; and / or, the molar content of H2S in the CO2 product gas is less than 1ppm, the molar content of CO2 is 99.3-99.7%; the temperature is -55°C to -50°C, and the pressure is 0.05-0.08MPa(G); And / or, the molar content of H2S in the low H2S methanol is 0.2-0.5%, the molar content of CO2 is 15-20%; the temperature is -55 to -50°C, and the pressure is 0.13-0.17 MPa(G).

6. The method according to any one of claims 1 to 5, wherein: In step (4), The molar content of H2S in the low CO2 methanol is ≤0.5ppm, and the molar content of CO2 is 5-7%; the temperature is -58 to -53°C; and the pressure is 0.15-0.25MPa(G); and / or, the molar flow ratio of the semi-lean liquid methanol and nitrogen after the heat exchange is 85-100:1; And / or, the stripping pressure is 0.15-0.25 MPa(G); And / or, the tail gas obtained by the stripping has a molar content of H2S ≤0.5ppm, a molar content of CO2 of 80-85%, a temperature of -53 to -48°C, and a pressure of 0.15-0.25MPa(G).

7. The method according to any one of claims 1 to 6, wherein: The method further comprises: returning the low CO2 methanol after a third pressurization to 3.5-4 MPa(G) and performing the CO2 absorption.

8. A synthesis gas purification device supporting a pulverized coal gasification device, characterized in that: The device comprises an H2S absorption tower, a CO2 absorption tower, a flash tower, a reabsorption tower and a stripping tower connected in sequence, as well as a heat exchanger, a first cooler and a second cooler; The H2S absorption tower is used to absorb H2S from the synthesis gas to obtain the first H2S-rich methanol, the second H2S-rich methanol and the desulfurized gas; the CO2 absorption tower is used to absorb CO2 from the desulfurized gas to obtain the CO2-rich methanol, which is divided into the first CO2-rich methanol and the second CO2-rich methanol; The flash tower comprises a CO2 flash section arranged at the top and a H2S flash section arranged at the bottom, the CO2 flash section is used to perform CO2 flashing on the second CO2-rich methanol to obtain CO2-rich methanol after flashing, and the H2S flash section is used to perform H2S flashing on the second H2S-rich methanol to obtain H2S-rich methanol after flashing; The CO2-rich methanol after flashing enters the heat exchanger, and the obtained CO2-rich methanol after heat exchange enters the first cooler, and is divided into two streams after the first cooling. The first stream of CO2-rich methanol after cooling enters the upper part of the reabsorption tower for the first flashing, and the second stream of CO2-rich methanol after cooling enters the second cooler and enters the middle part of the reabsorption tower for the second flashing. The H2S-rich methanol after flashing enters the lower part of the reabsorption tower for the third flashing to obtain semi-lean liquid methanol and CO2 product gas, and the obtained low-H2S methanol is recycled to the H2S absorption tower; The semi-lean methanol is divided into two streams. The first stream of semi-lean methanol enters the heat exchanger, and the semi-lean methanol obtained after heat exchange enters the stripping tower for stripping. The obtained low-CO2 methanol is recycled and used in the CO2 absorption tower.

9. The device according to claim 8, wherein: The CO2-rich methanol outlet of the CO2 absorption tower is connected to the H2S absorption tower for recycling the first stream of CO2-rich methanol back to the H2S absorption tower; And / or, the H2S absorption tower comprises a pre-H2S absorption section disposed at the bottom and a main H2S absorption section disposed at the top; And / or, the CO2 absorption tower comprises a pre-CO2 absorption section arranged at the bottom and a main CO2 absorption section arranged at the top; And / or, in the flash tower, the top of the CO2 flash section is connected to the upper part of the H2S flash section, so as to mix the CO2 flash gas obtained by the CO2 flash and the H2S flash gas obtained by the H2S flash, and then wash them with low-temperature H2S-rich methanol to obtain flash gas.

10. The device according to claim 9, wherein: The device further comprises: a first pump is arranged on a pipeline connecting the low H2S methanol outlet of the reabsorption tower and the H2S absorption tower, for performing the H2S absorption on the low H2S methanol after a first pressurization; And / or, according to the material flow direction, a second pump and a fourth cooler are sequentially arranged on the pipeline connecting the CO2-rich methanol outlet of the CO2 absorption tower and the H2S absorption tower, for subjecting the first stream of CO2-rich methanol to the second pressurization and the fourth cooling in sequence to the H2S absorption; And / or, according to the material flow direction, a fifth cooler is provided on the pipeline connecting the main CO2 absorption section and the pre-CO2 absorption section in the CO2 absorption tower; And / or, a third cooler is provided on the pipeline connecting the main H2S absorption section and the H2S flash section.

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