Low-temperature low-sulfur low-carbon methanol washing device matched with pulverized coal gasification device and method thereof

Abstract

The invention relates to the technical field of low-temperature methanol washing, in particular to a low-temperature low-sulfur low-carbon methanol washing device matched with a pulverized coal gasification device and a method of the low-temperature low-sulfur low-carbon methanol washing device. And the low-temperature methanol washing device is low in comprehensive energy consumption.

Description

Technical Field

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

[0002] In the syngas produced by 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 the raw material gases for synthesizing chemical products such as methanol and ammonia after adjusting the hydrogen-carbon ratio through the conversion 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 the absorption solvent. Utilizing the excellent property that low-temperature methanol has a great solubility for acid gases, it uses physical absorption to 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 acid gases is achieved through staged pressure reduction flashing and thermal regeneration.

[0004] At present, the innovative research on the low-temperature methanol washing technology mainly focuses on the recycling of the pressure reduction flashing of rich CO 2 methanol. The typical process is the lean liquid - semi-lean liquid process, which 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, rich CO 2 methanol can be recycled through flashing, but H 2 S-containing methanol must be recycled through thermal regeneration, which is the main energy-consuming source of low-temperature methanol washing. Therefore, improving the utilization efficiency of H 2 S-containing methanol and reducing the total amount of thermal regeneration of H 2 S-containing methanol are the direction and key factors for future technological innovation.

[0005] CN201110260570.0 discloses a low-temperature methanol washing process. First, in this low-temperature methanol washing process, the entire H 2 S absorption tower uses rich CO 2 methanol to wash the syngas, increasing the production amount of rich H 2 S methanol, rich H2 The methanol needs to be thermally regenerated before it can be recycled, resulting in high energy consumption. Second, in the reabsorption tower, the CO 2 flash evaporation section, the rich CO 2 methanol washes the rich H 2 S methanol while directly mixing with the rich H 2 S methanol, and itself is contaminated by the rich H 2 S methanol, producing low-concentration H 2 S methanol is not fully utilized, resulting in high energy consumption. Third, the semi-lean liquid methanol CO 2 used in the carbon dioxide absorption tower has a relatively high 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 technical problems, and provide a cold methanol washing unit for supporting a pulverized coal gasification unit and a cold methanol washing method for supporting a pulverized coal gasification unit. This method has the characteristics that the recycled low-carbon methanol has strong absorption energy for CO 2 gas, the recycled low-H 2 S methanol has high utilization efficiency and strong absorption energy, and the overall energy consumption of the cold methanol washing unit is low.

[0007] To achieve the above object, in the first aspect of the present invention, a cold methanol washing unit for supporting a pulverized coal gasification unit is provided. The unit includes: an absorption tower, a medium-pressure flash evaporation tower, a reabsorption tower, and a stripping tower connected in sequence; the absorption tower includes an H 2 S absorption section arranged below and a CO 2 absorption section arranged above; the medium-pressure flash evaporation tower includes an H 2 S flash evaporation section arranged below and a CO 2 flash evaporation section arranged above, and the H 2 S flash evaporation section is divided into an H 2 S flash evaporation part and a washing part from bottom to top;

[0008] Among them, the syngas enters the H 2 S absorption section for H 2 S absorption, and the obtained first rich H 2 S methanol is divided into two streams. The second stream of rich H 2 S methanol enters the H 2 S flash evaporation part for H 2 S flash evaporation, obtaining H 2 S flash evaporation gas and rich H 2 S methanol after flash evaporation; the desulfurized gas obtained from the H 2 S absorption also enters the CO 2 absorption section for CO 2 absorption, obtaining the rich CO2 The methanol is divided into two streams, and the second stream is rich in CO 2 The methanol enters the CO 2 flash section for CO 2 flash, obtaining CO 2 flash gas and CO-rich methanol after flashing 2 methanol; wherein, the CO 2 flash gas and the flash gas are mixed and then subjected to a first washing with the second stream of low-carbon methanol from the stripping column in the washing section to obtain low-sulfur CO-rich methanol;

[0009] The CO-rich methanol after flashing 2 methanol is successively passed through a heat exchanger and a sixth cooler and then divided into two streams. The first stream of CO-rich methanol after flashing 2 methanol enters the upper part of the reabsorption column for a first flash, and the resulting semi-lean liquid methanol is divided into two streams. The first stream of semi-lean liquid methanol passes through a heat exchanger and then enters the stripping column for stripping, and the resulting low-carbon methanol is divided into two streams; The second stream of CO-rich methanol after flashing 2 methanol, after passing through a first cooler, and the low-sulfur CO-rich methanol independently enter the middle part of the reabsorption column for a second flash; The H-rich methanol after flashing 2 S methanol, after passing through a second cooler, enters the middle part of the reabsorption column for a third flash, and the resulting sulfur-containing gas phase is subjected to a second washing with the flash liquid obtained from the second flash to obtain low-H 2 S methanol; The first stream of H-rich 2 S methanol, the first stream of CO-rich 2 methanol and low-H 2 S methanol are independently recycled to the H 2 S absorption section; The first stream of low-carbon methanol is recycled to the CO 2 absorption section.

[0010] The second aspect of the present invention provides a low-temperature, low-sulfur, and low-carbon methanol washing method for a supporting pulverized coal gasification device, and the method includes:

[0011] Subject the syngas to H 2 S absorption, and the resulting desulfurized gas is subjected to CO 2 absorption, obtaining CO-rich 2 methanol, which is divided into two streams, and the second stream is rich in CO 2 methanol is subjected to CO 2 flash, obtaining CO 2 flash gas and CO-rich methanol after flashing 2 methanol; The first rich H 2 S methanol obtained from the H 2 S absorption is also divided into two streams, and the second stream is rich in H 2 S methanol is subjected to H 2 S flash, obtaining H 2 S flash gas and H-rich methanol after flashing 2S methanol; After mixing the flash gas and H 2 S flash gas, perform the first washing with the second stream of low-carbon methanol to obtain low-sulfur rich-carbon methanol; 2

[0012] After subjecting the flash gas-rich CO 2 methanol to heat exchange and the sixth cooling in sequence, divide it into two streams. The first stream of flash gas-rich CO 2 methanol undergoes the first flash to obtain semi-lean liquid methanol which is divided into two streams; The second stream of flash gas-rich CO 2 methanol, after the first cooling, is mixed with the low-sulfur rich-carbon methanol and then undergoes the second flash; After subjecting the flash gas-rich H 2 S methanol to the second cooling, perform the third flash. The sulfur-containing gas phase obtained is subjected to the second washing with the flash liquid obtained from the second flash to obtain low-H 2 S methanol; After subjecting the first stream of semi-lean liquid methanol to the heat exchange, perform stripping to obtain low-carbon methanol which is divided into two streams; Among them, the first stream of H 2 S-rich methanol, the first stream of CO 2 -rich methanol, and the low-H 2 S methanol independently return and perform the said H 2 S absorption; Return the first stream of low-carbon methanol and perform the said CO 2 absorption.

[0013] Through the above technical solution, in the device provided by the present invention, in order to further reduce the CO 2 content in the semi-lean liquid methanol and maximize the CO 2 absorption capacity of the semi-lean liquid methanol, the optimized re-absorption process performs nitrogen stripping on the first stream of semi-lean liquid methanol, so that the CO 2 molar content in the semi-lean liquid methanol is further reduced to 5 - 7%, becoming low-carbon methanol. This can produce two positive effects: First, with the improvement of the absorption capacity of low-carbon methanol and the reduction of the circulation volume, the operating cost of the pump can be reduced by about 15%, and the diameter of the CO 2 absorption section can be reduced by about 5%; Second, low-carbon methanol can replace part of the lean methanol, so that the circulation amount of lean methanol in the CO 2 absorption section also decreases. The reduction of the lean methanol flow rate will be transmitted to the H 2 S-rich methanol. The flow rate of the H 2 S-rich methanol that needs to be thermally regenerated will also decrease, and the energy consumption of the corresponding thermal regeneration system will also decrease accordingly.

[0014] The device provided by the present invention divides the absorption tower into an H 2 S absorption section arranged below and a CO 2 absorption section arranged above, and further optimizes the H 2 S absorption section and the CO 2 ​Absorption section; specifically, by introducing low-H 2 S methanol and the first rich-H 2 S methanol to pre-absorb H 2 S and CO 2 in the syngas, not only realizes the recycling of low-H 2 S methanol, but also reduces the usage amount of the first rich-CO 2 methanol, which is equivalent to reducing the second rich-H 2 S methanol that needs to be thermally regenerated; in addition, such a setting correspondingly reduces the working load of the subsequent CO 2 absorption section, and at the same time reduces the usage amounts of the first low-carbon methanol and lean methanol in the CO 2 absorption section.

[0015] The device provided by the present invention optimizes the flash gas washing process in the medium-pressure flash tower, realizes the absorption of CO 2 gas in the flash gas of the second rich-CO 2 methanol and the second rich-H 2 S methanol by low-carbon methanol, and at the same time avoids the pollution of low-carbon methanol by rich-H 2 S methanol after flashing. The low-carbon methanol (i.e., low-sulfur rich-carbon methanol) that has absorbed the flash gas is sent to the middle section of the re-absorption tower to continue absorbing and washing the CO 2 product gas, reduces the usage amount of rich-CO 2 methanol for washing the CO 2 product gas, and correspondingly reduces the energy consumption of the device.

[0016] The device provided by the present invention divides the re-absorption tower into an upper part, a middle part and a lower part. By optimizing the internal structuring of the re-absorption tower, it realizes the absorption of the sulfur-containing gas phase (e.g., H 2 S) in the third CO 2 product gas generated by the flashing of the rich-H 2 S methanol after the second flashing by the flash liquid obtained from the second flashing, but does not mix with the third rich-H 2 S methanol, and obtains low-H 2 S methanol with a lower sulfur content. Brief Description of the Drawings

[0017] Figure 1 is a schematic structural diagram of a low-temperature, low-sulfur and low-carbon methanol washing device for a supporting pulverized coal gasification device provided by the present invention.

[0018] Description of the Reference Numerals

[0019] T-1, Absorption Tower; T-2, Medium-pressure Flash Tower; T-3, Re-absorption Tower; T-4, 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; E-6, Sixth Cooler; P-1, First Pump; P-2, Second Pump; 1, Syngas; 2, Low H 2 S Methanol; 3, Second Hydrogen-rich 2 S Methanol; 4, CO-rich 2 Methanol; 4-i, First CO-rich 2 Methanol; 4-ii, Second CO-rich 2 Methanol; 5, First Hydrogen-rich 2 S Methanol; 5-i, First Hydrogen-rich 2 S Methanol; 5-ii, Second Hydrogen-rich 2 S Methanol; 6, Desulfurized Gas; 7, CO-containing 2 Methanol; 8, Low-carbon Methanol; 8-i, First Low-carbon Methanol; 8-ii, Second Low-carbon Methanol; 9, Lean Methanol; 10, CO 2 Flash Vapor; 11, Flash Vapor; 12, CO-rich after Flash 2 Methanol; 12-i, First CO-rich after Flash 2 Methanol; 12-ii, Second CO-rich after Flash 2 Methanol; 13, Low-sulfur Carbon-rich Methanol; 14, Hydrogen-rich after Flash 2 S Methanol; 15, Semi-lean Methanol; 15-i, First Semi-lean Methanol; 15-ii, Second Semi-lean Methanol; 16, Third Hydrogen-rich 2 S Methanol; 17, CO 2 Product Gas; 18, Tail Gas; 19, Nitrogen. Detailed Embodiments

[0020] The endpoints and any values 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, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered specifically disclosed herein.

[0021] In the present invention, without special circumstances, "first", "second", "third", "fourth", "fifth", and "sixth" 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", "fifth", and "sixth" in "first cooling", "second cooling", "third cooling", "fourth cooling", "fifth cooling", and "sixth cooling" are only used to indicate that these are not the same cooling.

[0022] 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.

[0023] The first aspect of the present invention provides a structural schematic diagram of a low-temperature, low-sulfur, and low-carbon methanol washing device for a coal-water slurry gasification device as Figure 1 shown, and it can be seen from Figure 1 that the device includes: an absorption tower T-1, a medium-pressure flash tower T-2, a reabsorption tower T-3, and a stripping tower T-4 connected in sequence; the absorption tower T-1 includes an H 2 S absorption section arranged at the bottom and a CO 2 absorption section arranged at the top; the medium-pressure flash tower T-2 includes an H 2 S flash section arranged at the bottom and a CO 2 flash section arranged at the top, and the H 2 S flash section is divided into an H 2 S flash part and a washing part from bottom to top;

[0024] Among them, synthesis gas 1 enters the H 2 S absorption section for H 2 S absorption, and the obtained first rich H 2 S methanol 5 is divided into two streams, and the second rich H 2 S methanol 5-ii enters the H 2 S flash part for H 2 S flash, obtaining H 2 S flash gas and rich H 2 S methanol 14 after flashing; the desulfurized gas obtained from the H 2 S absorption also enters the CO 2 absorption section for CO 2 absorption, and the obtained rich CO 2 methanol 4 is divided into two streams, and the second rich CO 2 methanol 4-ii enters the CO 2Flash evaporation section performs CO 2 flash evaporation to obtain CO 2 flash vapor 10 and CO-rich methanol 12 after flash evaporation; wherein, the CO 2 flash vapor 10 and H 2 S flash vapor are mixed and then subjected to first washing with the second low-carbon methanol 8-ii from the stripping column T-4 in the washing section to obtain low-sulfur carbon-rich methanol 13; 2

[0025] The CO-rich methanol 12 after flash evaporation 2 is successively passed through heat exchanger Q and the sixth cooler E-6 and then divided into two streams. The first stream of CO-rich methanol 12-i after flash evaporation 2 enters the upper part of the reabsorption column T-3 for first flash evaporation. The obtained semi-lean liquid methanol 15 is divided into two streams. The first stream of semi-lean liquid methanol 15-i passes through heat exchanger Q and then enters the stripping column T-4 for stripping. The obtained low-carbon methanol 8 is divided into two streams; the second stream of CO-rich methanol 12-ii after flash evaporation 2 enters the middle part of the reabsorption column T-3 for second flash evaporation after passing through the first cooler E-1, independently of the low-sulfur carbon-rich methanol 13; the H 2 S-rich methanol 14 enters the middle part of the reabsorption column T-3 for third flash evaporation after passing through the second cooler E-2. The obtained sulfur-containing gas phase and the flash liquid obtained from the second flash evaporation are subjected to second washing to obtain low-H 2 S methanol 2; the first stream of H 2 S-rich methanol 5-i, the first stream of CO-rich methanol 4-i, and the low-H 2 S methanol 2 are independently recycled to the H 2 S absorption section; the first stream of low-carbon methanol 8-i is recycled to the CO 2 absorption section. 2

[0026] In the present invention, as Figure 1 shown, the H 2 S absorption section is divided into a first H 2 S absorption part and a second H 2 S absorption part from bottom to top. Specifically, the first H 2 S absorption part introduces the first stream of H 2 S-rich methanol 5-i to pre-wash and absorb H 2 S, HCN, NH 3 in the syngas 1; the second H 2 S absorption part realizes the recycling of the low-H 2 S methanol 2 by introducing the low-H 2 S methanol to absorb H 2 S and CO 2 in the pre-desulfurized gas, reducing the first stream of CO-rich 2 ​​The usage amount of methanol 4-i is equivalent to reducing the second rich H stream that needs thermal regeneration 2 S methanol 5-ii; in addition, such a setting correspondingly reduces the subsequent CO 2 absorption section's working load, and correspondingly also reduces the CO 2 usage amounts of lean methanol and the first low-carbon methanol in the absorption section.

[0027] In the present invention, as Figure 1 shown, preferably, the first rich H 2 S methanol 5-i is recycled to the first H 2 S absorption section; preferably, the first rich CO 2 methanol 4-i and low H 2 S methanol 2 are each independently recycled to the second H 2 S absorption section.

[0028] In the present invention, as Figure 1 shown, in the absorption tower T-1, the H 2 S absorption section is divided into a first H 2 S absorption section and a second H 2 S absorption section from bottom to top, and the first H 2 S absorption section and the second H 2 S absorption section are connected by lifting pores. Specifically, the first H 2 S absorption section is connected to the bottom of the second H 2 S flash section, and is used to contact the syngas 1 with the first rich H 2 S methanol 5-i and perform the first H 2 S absorption to obtain the second rich H 2 S methanol 3 and the pre-desulfurized gas; the second H 2 S absorption section is connected to the low H 2 S methanol outlet of the re-absorption tower T-3 and the rich CO 2 methanol outlet of the CO 2 absorption section, and is used to sequentially contact the pre-desulfurized gas with low H 2 S methanol 2 and the first rich CO 2 methanol 4-i and perform the second H 2 S absorption to obtain the desulfurized gas and the first rich H 2 S methanol 5.

[0029] In the present invention, without special circumstances, in the first H 2 S absorption section, the contact mode between the syngas and the first rich H 2 S methanol 5-i is preferably the countercurrent contact between the syngas 1 and the first rich H 2 S methanol 5-i, that is, the syngas 1 enters from the bottom of the first H 2 S absorption section, and the first rich H2 S methanol 5-i enters from the upper part of the first H 2 and enters the upper part of the S absorption section.

[0030] In the present invention, as Figure 1 shown, the CO 2 absorption section is divided into a first CO 2 absorption section and a second CO 2 absorption section from bottom to top, and the bottom of the second CO 2 absorption section is connected to the upper part of the first CO 2 absorption section.

[0031] In the present invention, as Figure 1 shown, preferably, the first stream of low-carbon methanol 8-i is recycled to the second CO 2 absorption section.

[0032] In the present invention, as Figure 1 shown, the CO 2 absorption section includes a first CO 2 absorption section arranged below and a second CO 2 absorption section arranged above; the first CO 2 absorption section and the second CO 2 absorption section are connected by an upflow hole, wherein the upper part of the first CO 2 absorption section is connected to the lower part of the second CO 2 absorption section for contacting the desulfurized gas with CO 2 -containing methanol 7 and performing the first CO 2 absorption to obtain the CO 2 -rich methanol 4 and the pre-purified gas; the second CO 2 absorption section is connected to the low-carbon methanol outlet of the stripping column T-4 and the lean methanol 9 from the subsequent process for contacting the pre-purified gas with the first stream of low-carbon methanol 8-i and the lean methanol 9 in sequence and performing the second CO 2 absorption to obtain the purified gas 6 and the CO 2 -containing methanol 7.

[0033] In the present invention, without special description, in the CO 2 absorption section, for the first CO 2 absorption section, the contact mode between the desulfurized gas and the CO 2 -containing methanol 7 is preferably selected from the countercurrent contact between the desulfurized gas and the CO 2 -containing methanol 7; that is, the desulfurized gas enters from the bottom of the first CO 2 absorption section, and the CO 2 -containing methanol 7 enters from the upper part of the first CO 2 absorption section.

[0034] In the present invention, as Figure 1As shown, the medium-pressure flash tower T-2 includes an H 2 S flash section and CO set on top 2 Flash stage, and H 2 S flash section is divided into H from bottom to top 2 S flash section and washing section, H 2 The S flash section and the scrubbing section are connected via a gas lift hole. Specifically, CO 2 The flash section is used to convert the second stream of CO-rich 2 Methanol 4-ii for CO 2 Flash evaporation to obtain CO 2 Flash gas 10 and rich CO after flash evaporation 2 Methanol 12; H 2 S flash section is used to transfer the second H-rich 2 S methanol 5-ii was subjected to H 2 S flashes to obtain H 2 S flash gas and H-rich after flash evaporation 2 S methanol 14; among which, CO 2 Flash gas 10 enters H 2 S flash section and H 2 After the flash gas is mixed, it enters the washing section and undergoes the first washing with the second stream of low-carbon methanol 8-ii from the stripping tower T-4 to obtain low-sulfur carbon-rich methanol 13 and flash gas 11.

[0035] In the present invention, if Figure 1 As shown, the heat exchanger Q is used to convert the flash-evaporated rich CO 2 Methanol 12 is heat exchanged with the first stream of semi-lean methanol 15-i to obtain a CO-rich 2 methanol and semi-lean methanol after heat exchange; the sixth cooler E-6 is used to heat the CO-rich 2 After the sixth cooling, the methanol is divided into two streams, i.e., the first stream is rich in CO after flash evaporation 2 Methanol 12-i and the first stream after flash distillation and rich in CO 2 Methanol 12-ii.

[0036] In the present invention, if Figure 1 As shown in FIG. 1 , the upper and middle parts of the reabsorption tower T-3 are connected through a gas riser, and the middle and lower parts are also connected through a gas riser. Specifically, the upper part is used to transfer the first stream of flashed CO-rich 2 Methanol 12-i is subjected to a first flash distillation to obtain semi-lean liquid methanol 15 and a first CO 2 Product gas; the middle part is used to flash the second stream of CO-rich 2 After the first cooling, methanol 12-ii and low-sulfur carbon-rich methanol 13 are independently subjected to a second flash distillation to obtain a flash liquid and a second CO 2 Product gas; the lower part is used to transfer the H-rich gas after flash evaporation 2 ​​​​​The S - methanol 14 is subjected to a third flash after the second cooling to obtain a third H - rich 2 S - methanol 16 and a sulfur - containing gas phase; wherein, the sulfur - containing gas phase and the flash liquid are subjected to a second washing to obtain low - H 2 S - methanol 2 and a third CO 2 product gas; the CO 2 product gas 17 includes a first CO 2 product gas, a second CO 2 product gas and a third CO 2 product gas.

[0037] In the present invention, as Figure 1 shown, preferably, a first pump P - 1 is provided on the pipeline connecting the low - H 2 S - methanol outlet of the re - absorption tower T - 3 and the second H 2 S absorption section, for pressurizing the low - H 2 S - methanol 2 by the first stage and recycling it to the second H 2 S absorption section.

[0038] In the present invention, as Figure 1 shown, preferably, in the direction of material flow, a third cooler E - 3 is provided on the pipeline connecting the bottom of the second CO 2 absorption section and the upper part of the first CO 2 absorption section, for cooling the CO - containing 2 methanol 7 by the third stage and recycling it to the first CO 2 absorption section.

[0039] In the present invention, as Figure 1 shown, preferably, in the direction of material flow, a fourth cooler E - 4 is provided on the pipeline connecting the bottom of the first CO 2 absorption section and the upper part of the second H 2 S absorption section, for cooling the first rich - CO 2 methanol 4 - i by the fourth stage and recycling it to the second H 2 S absorption section.

[0040] In the present invention, as Figure 1 shown, preferably, a second pump P - 2 is provided on the pipeline connecting the low - carbon methanol outlet of the stripping tower T - 4 and the second CO 2 absorption section, for pressurizing the low - carbon methanol 8 by the second stage and dividing it into two streams, the first stream of low - carbon methanol 8 - i is recycled to the second CO 2 absorption section, and the second stream of low - carbon methanol 8 - ii is recycled to the washing section.

[0041] In the present invention, as Figure 1As shown, preferably, a fifth cooler E-5 is provided on the pipeline connecting the low-sulfur and carbon-rich methanol outlet of the medium-pressure flash column T-2 and the reabsorption column T-3, for second flash of the low-sulfur and carbon-rich methanol 13 after being cooled by the fifth cooler.

[0042] In the present invention, as Figure 1 shown, preferably, the stripping column T-4 is used to make the first semi-lean methanol 15-i contact with nitrogen 19 and perform stripping after heat exchange to obtain the low-carbon methanol 8 and the tail gas 18.

[0043] The second aspect of the present invention provides a low-temperature, low-sulfur and low-carbon methanol washing method for a supporting pulverized coal gasification device, and the method includes:

[0044] Performing H 2 S absorption on the syngas, and performing CO 2 absorption on the obtained desulfurized gas to obtain the CO-rich 2 methanol, which is divided into two streams. The second stream of CO-rich 2 methanol performs CO 2 flash to obtain the CO 2 flash gas and the CO-rich 2 methanol after flashing; the first H-rich 2 S methanol obtained by the H 2 S absorption is also divided into two streams. The second stream of H-rich 2 S methanol performs H 2 S flash to obtain the H 2 S flash gas and the H-rich 2 S methanol after flashing; mixing the CO 2 flash gas and the H 2 S flash gas, and performing first washing with the second stream of low-carbon methanol to obtain the low-sulfur and carbon-rich methanol;

[0045] The CO-rich 2 methanol after flashing is successively subjected to heat exchange and sixth cooling and then divided into two streams. The first stream of CO-rich 2 methanol after flashing performs first flash to obtain semi-lean methanol divided into two streams; the second stream of CO-rich 2 methanol after flashing is cooled by the first cooler and then independently performs second flash with the low-sulfur and carbon-rich methanol; the H-rich 2 S methanol after flashing is cooled by the second cooler and then performs third flash, and the obtained sulfur-containing gas phase is subjected to second washing with the flash liquid obtained by the second flash to obtain the low-H 2 S methanol; the first stream of semi-lean methanol is stripped after heat exchange to obtain low-carbon methanol divided into two streams; among them, the first stream of H-rich 2 S methanol, the first stream of CO-rich 2 methanol and the low-H 2The S methanol independently returns and undergoes the said H 2 S absorption; the first low-carbon methanol is returned and undergoes the said CO 2 absorption.

[0046] In some embodiments of the present invention, preferably, the said H 2 S absorption includes: the first H 2 S absorption and the second H 2 S absorption; wherein, the process of the said first H 2 S absorption includes: contacting the syngas and the first rich H 2 S methanol and undergoing the said first H 2 S absorption to obtain the second rich H 2 S methanol and the pre-desulfurized gas; the process of the said second H 2 S absorption includes: contacting the pre-desulfurized gas, low H 2 S methanol and the first rich CO 2 methanol and undergoing the said second H 2 S absorption to obtain the desulfurized gas and the first rich H 2 S methanol.

[0047] In some embodiments of the present invention, 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 - 46%; the temperature is -25°C to -15°C, and the pressure is 3.12 - 3.15 MPa(G). In the present invention, there is a relatively wide selection range for the source of the syngas, as long as the syngas meets the above limitations. Preferably, the syngas is selected from the pulverized coal gasification waste heat boiler process or the pulverized coal gasification quench process.

[0048] In some embodiments of the present invention, preferably, the molar flow ratio of the syngas and the first rich H 2 S methanol is 50 - 60:1.

[0049] In the present invention, the said first 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 said second rich H 2 S methanol is 0.6 - 0.9%, and the molar content of CO 2 is 30 - 36%.

[0050] In some embodiments of the present invention, preferably, the said first rich H 2The S methanol is divided into a first rich-H 2 S methanol and a second rich-H 2 S methanol with a molar flow rate ratio of 1:45 - 55. In the present invention, the first rich-H 2 S methanol is divided into two streams. The first stream returns and undergoes the first H 2 S absorption, and the second stream undergoes H 2 S flash evaporation.

[0051] In the present invention, the second H 2 S absorption aims to further remove H 2 S and a small amount of CO 2 from the syngas. Preferably, the molar content of H 2 S in the first rich-H 2 S methanol is 0.3 - 0.5%, and the molar content of CO 2 is 27 - 32%.

[0052] In some embodiments of the present invention, preferably, the molar flow rate ratio of the syngas to the low-H 2 S methanol is 2.5 - 3:1; the molar flow rate ratio of the syngas to the first rich-CO 2 methanol is 1.8 - 2.2:1.

[0053] In some embodiments of the present invention, preferably, the CO 2 absorption includes a first CO 2 absorption and a second CO 2 absorption; wherein, the process of the first CO 2 absorption includes: contacting the desulfurized gas with the CO 2 -containing methanol and performing the first CO 2 absorption to obtain the rich-CO 2 methanol and the pre-purified gas; the process of the second CO 2 absorption includes: contacting the pre-purified gas, the first stream of low-carbon methanol, and the lean methanol and performing the second CO 2 absorption to obtain the purified gas and the CO 2 -containing methanol.

[0054] In the present invention, the rich-CO 2 methanol is divided into two streams. The first stream returns and undergoes the second H 2 S absorption, and the second stream undergoes CO 2 flash evaporation. Preferably, the rich-CO 2 methanol is divided into a first rich-CO 2 methanol and a second rich-CO 2 methanol with a molar flow rate ratio of 1:2.3 - 2.8.

[0055] In the present invention, the first CO 2 absorption is intended to further remove CO in the desulfurized gas 2 . Preferably, the molar content of CO in the CO-rich 2 methanol is 16 - 20%, and the molar content of H 2 S is 0.1 - 0.5 ppm; the pressure is 3.05 - 3.1 MPa(G). 2 In some embodiments of the present invention, preferably, the molar flow ratio of the purified gas to the CO-containing

[0056] methanol is 1:2.6 - 3.1. 2 In some embodiments of the present invention, preferably, the molar flow ratio of the purified gas to the first stream of low-carbon methanol is 1:1 - 1.2; the molar flow ratio of the purified gas to the lean methanol is 1:1.4 - 1.6.

[0057] In some embodiments of the present invention, preferably, the molar content of H

[0058] S in the purified gas is < 0.1 ppm, and the molar content of CO 2 is < 20 ppm; the temperature is -55 to -50 °C, and the pressure is 3 - 3.05 MPa(G). 2 In some embodiments of the present invention, preferably, the molar content of H

[0059] S in the CO-containing 2 methanol is 0.1 - 0.5 ppm, and the molar content of CO 2 is 9 - 14%; further preferably, in the direction of material flow, after cooling the CO-containing 2 methanol to -36 to -33 °C by the third cooler, it is returned and the first CO 2 absorption is carried out. 2 In some embodiments of the present invention, preferably, after cooling the first stream of CO-rich

[0060] methanol to -48 to -44 °C by the fourth cooler, it is returned and the H 2 S absorption is carried out. 2 In the present invention, the process of CO

[0061] flashing includes: the second stream of CO-rich 2 methanol undergoes CO 2 flashing to obtain CO 2 flashed gas and CO-rich 2 methanol after flashing; the process of H 2 S flashing includes: the second stream of H 2 S-rich methanol undergoes H 2 S flashing to obtain H 2 flashed gas and H 2S flash vapor and H-rich methanol after flashing 2 S methanol.

[0062] In some embodiments of the present invention, preferably, the CO 2 flashing and H 2 The pressures of S flashing are each independently 0.8 - 1 MPa(G).

[0063] In some embodiments of the present invention, preferably, the H content in the CO-rich methanol after flashing 2 is 0.1 - 0.5 ppm in terms of molar content, and the CO 2 molar content is 15.5 - 19.5%. 2

[0064] In some embodiments of the present invention, more preferably, the CO-rich methanol after flashing 2 is divided into the first stream of CO-rich methanol after flashing and the second stream of CO-rich methanol after flashing with a molar flow rate ratio of 3.4 - 3.8:1 2 2 methanol.

[0065] In some embodiments of the present invention, preferably, the temperature of the CO 2 flash vapor is -25°C to -20°C, and the pressure is 0.8 - 1 MPa(G).

[0066] In some embodiments of the present invention, preferably, the H content in the H-rich methanol after flashing 2 is 0.3 - 0.5% in terms of molar content, and the CO 2 molar content is 26.5 - 31.5%; the temperature is -25 to -20°C. 2

[0067] In the present invention, the process of the first washing includes: mixing the CO 2 flash vapor and H 2 S flash vapor, and then performing the first washing with the second stream of low-carbon methanol to obtain low-sulfur carbon-rich methanol and flash vapor.

[0068] In some embodiments of the present invention, preferably, the H content in the low-sulfur carbon-rich methanol 2 is 0.6 - 1.2‰ in terms of molar content, and the CO 2 molar content is 18 - 22%.

[0069] In some embodiments of the present invention, more preferably, after the low-sulfur carbon-rich methanol is cooled to -52 to -48°C by the fifth cooling, the second flashing is carried out.

[0070] In some embodiments of the present invention, preferably, the temperature of the flash vapor obtained from the first washing is -25 to -20 °C, and the pressure is 0.8 - 1 MPa(G), which is sent to subsequent processes for treatment.

[0071] In some embodiments of the present invention, preferably, the heat exchange process includes: subjecting the flash-rich CO 2 methanol and the first semi-lean methanol to the heat exchange to obtain heat-exchanged flash-rich CO 2 methanol and heat-exchanged semi-lean methanol; wherein, the temperature of the heat-exchanged flash-rich CO 2 methanol is -30 to -26 °C; the temperature of the heat-exchanged semi-lean methanol is -46 to -42 °C.

[0072] In some embodiments of the present invention, preferably, the temperature of the material after the sixth cooling is -36 to -33 °C.

[0073] In the present invention, the first cooling is achieved by reducing the temperature of the second flash-rich CO 2 methanol, generating low temperature through pressure-reducing flash evaporation, improving the absorption capacity of the flash liquid for H 2 S gas, and being beneficial to washing H 2 S gas in the flash CO 2 product gas. Preferably, the temperature of the material after the first cooling is -55 to -50 °C.

[0074] In the present invention, the process of the first flash evaporation includes: subjecting the first flash-rich CO 2 methanol 12-i to the first flash evaporation to obtain semi-lean methanol and the first CO 2 product gas; the process of the second flash evaporation includes: subjecting the second flash-rich CO 2 methanol after the first cooling and the low-sulfur rich-carbon methanol to the second flash evaporation independently to obtain flash liquid and the second CO 2 product gas; the process of the third flash evaporation includes: subjecting the flash-rich H 2 S methanol after the second cooling to the third flash evaporation to obtain the third flash-rich H 2 S methanol and sulfur-containing gas phase.

[0075] In some embodiments of the present invention, preferably, the pressure of the first flash evaporation is 0.05 - 0.08 MPa(G), the pressure of the second flash evaporation is 0.06 - 0.09 MPa(G), and the pressure of the third flash evaporation is 0.12 - 0.16 MPa(G).

[0076] In some embodiments of the present invention, preferably, the molar content of CO 2 in the semi-lean methanol is 10 - 14%, and the H 2The molar content of S is ≤0.5 ppm; the temperature is -53 to -48 °C; the pressure is 0.05 - 0.08 MPa(G).

[0077] In the present invention, the semi-lean methanol is divided into two streams. The first stream is stripped after heat exchange, and the second stream is sent to subsequent processes for treatment. Preferably, the semi-lean methanol is divided into the first semi-lean methanol and the second semi-lean methanol with a molar flow ratio of 3 - 3.5:1.

[0078] In some embodiments of the present invention, preferably, the low-H 2 S in the methanol 2 The molar content of S is 1.5 - 2.5 ‰, and the molar content of CO 2 is 15 - 20%; the temperature is -56 to -53 °C, and the pressure is 0.12 - 0.16 MPa(G).

[0079] In some embodiments of the present invention, preferably, after the low-H 2 S methanol is pressurized to 3.5 - 3.6 MPa(G) for the first time, it is returned and the H 2 S absorption is carried out.

[0080] In some embodiments of the present invention, preferably, the temperature of the material after the second cooling is -34 to -30 °C.

[0081] In some embodiments of the present invention, preferably, the third rich-H 2 S in the methanol 2 The molar content of S is 0.3 - 0.4%, and the molar content of CO 2 is 15 - 20%; the temperature is -62 to -58 °C; the pressure is 0.13 - 0.17 MPa(G).

[0082] In some embodiments of the present invention, preferably, the first CO 2 product gas obtained from the first flash, the second CO 2 product gas obtained from the second flash, and the third CO 2 product gas obtained from the second wash are mixed to obtain a CO 2 product gas in which the molar content of H 2 S is <1 ppm, and the molar content of CO 2 is 99.4 - 99.7%; the temperature is -56 to -53 °C, and the pressure is 0.05 - 0.08 MPa(G).

[0083] In some embodiments of the present invention, preferably, the stripping process includes: after the first semi-lean methanol is heat-exchanged, it contacts with nitrogen and is stripped to obtain the low-carbon methanol and tail gas.

[0084] In some embodiments of the present invention, preferably, the molar content of H 2 S in the low-carbon methanol is ≤ 0.5 ppm, and the molar content of CO 2 is 5 - 7%; the temperature is -55 to -50 °C; the pressure is 0.15 - 0.25 MPa(G).

[0085] In some embodiments of the present invention, preferably, the low-carbon methanol is divided into a first stream of low-carbon methanol and a second stream of low-carbon methanol with a molar flow ratio of 7.5 - 8.5:1; further preferably, after the low-carbon methanol is pressurized to 3.5 - 3.6 MPa(G) for the second time, it is divided into the first stream of low-carbon methanol and the second stream of low-carbon methanol, and then they are respectively returned and subjected to the CO 2 absorption and the first washing.

[0086] In some embodiments of the present invention, preferably, the molar content of H 2 S in the tail gas is ≤ 0.5 ppm, and the molar content of CO 2 is 83 - 88%; the temperature is -48 to -44 °C; the pressure is 0.15 - 0.25 MPa(G).

[0087] The present invention will be described in detail below through examples.

[0088] Example 1

[0089] The low-temperature and low-sulfur low-carbon methanol washing device supporting the pulverized coal gasification device is as Figure 1 shown. The device includes: an absorption tower T-1, a medium-pressure flash tower T-2, a reabsorption tower T-3, and a stripping tower T-4 connected in sequence, as well as a heat exchanger Q, a first cooler E-1, a second cooler E-2, a third cooler E-3, a fourth cooler E-4, a fifth cooler E-5, a sixth cooler E-6, a first pump P-1, and a second pump P-2;

[0090] The absorption tower T-1 includes an H 2 S absorption section arranged below and a CO 2 absorption section arranged above; the medium-pressure flash tower T-2 includes an H 2 S flash section arranged below and a CO 2 flash section arranged above, and the H 2 S flash section is divided into an H 2 S flash part and a washing part from bottom to top; the H 2 S absorption section is divided into a first H 2 S absorption part and a second H 2 S absorption part from bottom to top; the CO 2 absorption section is divided into a first CO 2Absorption section and second CO 2 Absorption section, and second CO 2 The bottom of the absorption section is connected to the first CO 2 The upper part of the absorption section.

[0091] Low-temperature, low-sulfur and low-carbon methanol washing method for a coal powder gasification device, the method comprising:

[0092] Mixing syngas 1 (H 2 The molar content of S is 0.3 - 0.4%, and the molar content of CO 2 is 40 - 46%; the temperature is -25°C to -15°C, and the pressure is 3.12 - 3.15 MPa(G)) and the first rich H 2 S methanol 5-i in a molar flow ratio of 50 - 60:1 for contact and perform the first H 2 S absorption to obtain the second rich H 2 S methanol 3 (H 2 The molar content of S is 0.6 - 0.9%, and the molar content of CO 2 is 30 - 36%) and pre-desulfurized gas; Mixing the above pre-desulfurized gas, low-H 2 S methanol 2 (pressurized to 3.5 - 3.6 MPa(G) for the first time) and the first rich CO 2 Methanol 4-i (cooled to -48 to -44°C for the fourth time) for contact and perform the second H 2 S absorption to obtain desulfurized gas and the first rich H 2 S methanol 5 (H 2 The molar content of S is 0.3 - 0.5%, and the molar content of CO 2 is 27 - 32%);

[0093] Dividing the above first rich H 2 S methanol 5 into a first rich H 2 S methanol 5-i and a second rich H 2 S methanol 5-ii with a molar flow ratio of 1:45 - 55;

[0094] Among them, the molar flow ratio of syngas 1 and low-H 2 S methanol 2 is 2.5 - 3:1; the molar flow ratio of syngas 1 and the first rich CO 2 Methanol 4-i is 1.8 - 2.2:1;

[0095] Mixing the above desulfurized gas and CO-containing 2 Methanol 7 (cooled to -36 to -33°C for the third time) for contact and perform the first CO 2 Absorption to obtain rich CO 2 Methanol 4 (CO 2 The molar content of is 16 - 20%, H 2The molar content of S is 0.1 - 0.5 ppm; the pressure is 3.05 - 3.1 MPa(G)) and the pre-purified gas; the second CO 2 The absorption process includes: contacting the pre-purified gas, the first low-carbon methanol 8-i and the lean methanol 9 and performing the second CO 2 absorption to obtain the purified gas 6 (H 2 S molar content < 0.1 ppm, CO 2 molar content < 20 ppm; the temperature is -55 to -50 °C, the pressure is 3 - 3.05 MPa(G)) and the above-mentioned CO-containing 2 methanol 7 (H 2 The molar content of S is 0.1 - 0.5 ppm, CO 2 molar content is 9 - 14%);

[0096] Dividing the above-mentioned CO-rich 2 methanol 4 into a first CO-rich 2 methanol 4-i and a second CO-rich 2 methanol 4-ii with a molar flow rate ratio of 1:2.3 - 2.8; the molar flow rate ratio of the purified gas 6 to the first low-carbon methanol 8-i is 1:1 - 1.2; the molar flow rate ratio of the purified gas 6 to the lean methanol 9 is 1:1.4 - 1.6; the molar flow rate ratio of the purified gas 6 to the CO-containing 2 methanol 7 is 1:2.6 - 3.1; subjecting the above-mentioned second CO-rich 2 methanol 4-ii to CO 2 flashing (pressure is 0.8 - 1 MPa(G)) to obtain CO 2 flash gas 10 (temperature is -25 °C to -20 °C, pressure is 0.8 - 1 MPa(G)) and the CO-rich 2 methanol 12 (H 2 The molar content of S is 0.1 - 0.5 ppm, CO 2 molar content is 15.5 - 19.5%); subjecting the above-mentioned second H-rich 2 S methanol 5-ii to H 2 S flashing (pressure is 0.8 - 1 MPa(G)) to obtain H 2 S flash gas and the H-rich 2 S methanol 14 (H 2 S molar content is 0.3 - 0.5%, CO 2 molar content is 26.5 - 31.5%; temperature is -25 to -20 °C); mixing the above-mentioned CO 2 flash gas 10 and H 2 S flash gas, and performing the first washing with the second low-carbon methanol 8-ii to obtain low-sulfur CO-rich methanol 13 (H 2 S molar content is 0.6 - 1.2 ‰, CO2 with a molar content of 18 - 22%) and flash vapor 11 (temperature of -25°C to -20°C, pressure of 0.8 - 1 MPa(G));

[0097] After the above-mentioned flash evaporation, the CO-rich 2 methanol 12 is heat-exchanged with the first semi-lean methanol 15-i to obtain heat-exchanged CO-rich 2 methanol (temperature of -30 to -26°C) and heat-exchanged semi-lean methanol (temperature of -46 to -42°C). Among them, after the heat-exchanged CO-rich 2 methanol is cooled to -36 to -33°C by the sixth cooler, and then divided into a first flash-evaporated CO-rich 2 methanol 12-i and a second flash-evaporated CO-rich 2 methanol 12-ii with a molar flow ratio of 3.4 - 3.8:1;

[0098] The above-mentioned first flash-evaporated CO-rich 2 methanol 12-i is subjected to the first flash evaporation (pressure of 0.05 - 0.08 MPa(G)) to obtain the first CO 2 product gas and semi-lean methanol 15 (CO 2 with a molar content of 10 - 14%, H 2 with a molar content of S ≤ 0.5 ppm; temperature of -53 to -48°C; pressure of 0.05 - 0.08 MPa(G)). Among them, the above-mentioned semi-lean methanol 15 is divided into a first semi-lean methanol 15-i and a second semi-lean methanol 15-ii with a molar flow ratio of 3 - 3.5:1; The second flash-evaporated CO-rich 2 methanol 12-ii is cooled to -55 to -50°C by the first cooler, and then independently subjected to the second flash evaporation (pressure of 0.06 - 0.09 MPa(G)) with the low-sulfur carbon-rich methanol 13 (cooled to -52 to -48°C by the fifth cooler) to obtain the second CO 2 product gas and flash liquid; After the above-mentioned flash-evaporated H-rich 2 S methanol 14 is cooled to -34 to -30°C by the second cooler, and then subjected to the third flash evaporation (pressure of 0.12 - 0.16 MPa(G)) to obtain a sulfur-containing gas phase and a third H-rich 2 S methanol 16 (H 2 with a molar content of S of 0.3 - 0.4%, CO 2 with a molar content of 15 - 20%; temperature of -62 to -58°C; pressure of 0.13 - 0.17 MPa(G)); The above-mentioned sulfur-containing gas phase and flash liquid are subjected to the second washing to obtain the third CO 2 product gas and low-H 2 S methanol 2 (H 2 with a molar content of S of 1.5 - 2.5‰, CO 2The molar content is 15 - 20%; the temperature is -56 to -53 °C, and the pressure is 0.12 - 0.16 MPa(G));

[0099] Mix the above-mentioned first CO 2 product gas, second CO 2 product gas and third CO 2 product gas to obtain CO 2 product gas 17 (H 2 The molar content of S < 1 ppm, and the molar content of CO 2 is 99.4 - 99.7%; the temperature is -56 to -53 °C, and the pressure is 0.05 - 0.08 MPa(G));

[0100] Contact the post-heat-exchanged semi-lean methanol with nitrogen 19 and carry out stripping to obtain low-carbon methanol 8 (H 2 The molar content of S ≤ 0.5 ppm, and the molar content of CO 2 is 5 - 7%; the temperature is -55 to -50 °C; the pressure is 0.15 - 0.25 MPa(G)) and tail gas 18 (H 2 The molar content of S is ≤ 0.5 ppm, and the molar content of CO 2 is 83 - 88%; the temperature is -48 to -44 °C; the pressure is 0.15 - 0.25 MPa(G)). After pressurizing the low-carbon methanol 8 to 3.5 - 3.6 MPa(G) for the second time, it is divided into the first low-carbon methanol 8-i and the second low-carbon methanol 8-ii with a molar flow ratio of 7.5 - 8.5:1, and then they are respectively returned and the above-mentioned CO 2 absorption and first washing are carried out.

[0101] Comparative Example 1

[0102] Taking a hydrogen production device using pulverized coal gasification for gas production as an example, the effective gas (H 2 + CO) entering the low-temperature methanol washing device 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 pulverized coal gasification device) are compared in Table 1.

[0103] Table 1

[0104]

[0105] As can be seen from the results in Table 1, taking the hydrogen production device based on pulverized coal gasification as an example, for the syngas purification process of the supporting pulverized coal gasification device provided in Example 1, the lean methanol circulation rate is 94.62% of that in Comparative Example 1 (lean liquid - semi-lean liquid process), and the low-carbon methanol circulation rate is 75% of the semi-lean liquid methanol circulation rate in Comparative Example 1 (lean liquid - semi-lean liquid process). The H 2 S absorption process, the rich CO 2 methanol usage is 88.57% of the rich CO 2 methanol usage in Comparative Example 1 (lean liquid - semi-lean liquid process), and the cumulative reduction in external cooling consumption is 1100 KW / h, with a significant overall energy-saving effect.

[0106] 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 low-temperature, low-sulfur, low-carbon methanol washing device supporting a pulverized coal gasification device, characterized in that: The device comprises: an absorption tower, a medium-pressure flash tower, a reabsorption tower and a stripping tower connected in sequence; the absorption tower comprises an H2S absorption section arranged at the bottom and a CO2 absorption section arranged at the top; the medium-pressure flash tower comprises an H2S flash section arranged at the bottom and a CO2 flash section arranged at the top, and the H2S flash section is divided into an H2S flash section and a washing section from bottom to top; The synthesis gas enters the H2S absorption section for H2S absorption, and the first H2S-rich methanol obtained is divided into two streams, and the second stream of H2S-rich methanol enters the H2S flash section for H2S flash distillation to obtain H2S flash gas and H2S-rich methanol after flash distillation; the desulfurized gas obtained by the H2S absorption enters the CO2 absorption section for CO2 absorption, and the CO2-rich methanol obtained is divided into two streams, and the second stream of CO2-rich methanol enters the CO2 flash distillation section for CO2 flash distillation to obtain CO2 flash gas and CO2-rich methanol after flash distillation; wherein, the CO2 flash gas and the H2S flash gas are mixed, and then subjected to the first washing in the washing section with the second stream of low-carbon methanol from the stripping tower to obtain low-sulfur carbon-rich methanol; The CO2-rich methanol after flashing is passed through a heat exchanger and a sixth cooler in sequence and is divided into two streams. The first stream of CO2-rich methanol after flashing enters the upper part of the reabsorption tower for the first flash, and the semi-lean liquid methanol obtained is divided into two streams. The first stream of semi-lean liquid methanol passes through a heat exchanger and enters a stripping tower for stripping, and the low-carbon methanol obtained is divided into two streams; the second stream of CO2-rich methanol after flashing passes through the first cooler and enters the middle part of the reabsorption tower independently with the low-sulfur and carbon-rich methanol for the second flash; the H2S-rich methanol after flashing passes through the second cooler and enters the middle part of the reabsorption tower for the third flash, and the sulfur-containing gas phase obtained is subjected to a second washing with the flash liquid obtained by the second flash to obtain low-H2S methanol; the first stream of H2S-rich methanol, the first stream of CO2-rich methanol and the low-H2S methanol are independently reused in the H2S absorption section; the first stream of low-carbon methanol is reused in the CO2 absorption section.

2. The device according to claim 1, wherein: The H2S absorption section is divided into a first H2S absorption section and a second H2S absorption section from bottom to top; Preferably, the first stream of H2S-rich methanol is recycled to the first H2S absorption section; Preferably, the first stream of CO2-rich methanol and low H2S methanol are independently recycled to the second H2S absorption section; And / or, the CO2 absorption section is divided into a first CO2 absorption section and a second CO2 absorption section from bottom to top, and the bottom of the second CO2 absorption section is connected to the upper part of the first CO2 absorption section; Preferably, the first stream of low-carbon methanol is recycled to the second CO2 absorption section.

3. The device according to claim 2, wherein: A first pump is provided on the pipeline connecting the low H2S methanol outlet of the reabsorption tower and the second H2S absorption part, for returning the low H2S methanol to the second H2S absorption part after first pressurization; and / or, a third cooler is provided on the pipeline connecting the bottom of the second CO2 absorption part and the upper part of the first CO2 absorption part according to the material flow direction; And / or, according to the material flow direction, a fourth cooler is provided on the pipeline connecting the bottom of the first CO2 absorption part and the upper part of the second H2S absorption part, for recycling the first stream of CO2-rich methanol to the second H2S absorption part after the fourth cooling; And / or, a second pump is provided on the pipeline connecting the low-carbon methanol outlet of the stripping tower and the second CO2 absorption section, for dividing the low-carbon methanol into two streams after the second pressurization, the first stream of low-carbon methanol is returned to the second CO2 absorption section, and the second stream of low-carbon methanol is returned to the washing section.

4. The device according to any one of claims 1 to 3, wherein: A fifth cooler is provided on the pipeline connecting the low-sulfur and carbon-rich methanol outlet of the medium-pressure flash tower and the reabsorption tower, for cooling the low-sulfur and carbon-rich methanol through the fifth cooling before performing the second flash distillation; And / or, the stripping tower is used to contact the first stream of semi-lean liquid methanol with nitrogen after the heat exchange and perform the stripping to obtain the low-carbon methanol and tail gas.

5. A low-temperature, low-sulfur, low-carbon methanol washing method for a pulverized coal gasification device, characterized in that: The method comprises: subjecting synthesis gas to H2S absorption, subjecting the obtained desulfurized gas to CO2 absorption, dividing the obtained CO2-rich methanol into two streams, subjecting the second stream of CO2-rich methanol to CO2 flash evaporation, obtaining CO2 flash gas and CO2-rich methanol after flash evaporation; subjecting the first H2S-rich methanol obtained by the H2S absorption to H2S flash evaporation, obtaining H2S flash gas and H2S-rich methanol after flash evaporation; mixing the CO2 flash gas and the H2S flash gas, and then subjecting the mixed gas to a first washing with the second stream of low-carbon methanol, obtaining low-sulfur carbon-rich methanol; The CO2-rich methanol after flashing is sequentially subjected to heat exchange and the sixth cooling and is divided into two streams. The first stream of CO2-rich methanol after flashing is subjected to the first flash, and the obtained semi-lean liquid methanol is divided into two streams; the second stream of CO2-rich methanol after flashing is subjected to the first cooling, and is independently subjected to the second flash with the low-sulfur carbon-rich methanol; the H2S-rich methanol after flashing is subjected to the third flash after the second cooling, and the obtained sulfur-containing gas phase is subjected to the second washing with the flash liquid obtained by the second flash to obtain low-H2S methanol; the first stream of semi-lean liquid methanol is subjected to stripping after the heat exchange, and the obtained low-carbon methanol is divided into two streams; wherein, the first stream of H2S-rich methanol, the first stream of CO2-rich methanol and the low-H2S methanol are independently returned and subjected to the H2S absorption; the first stream of low-carbon methanol is returned and subjected to the CO2 absorption.

6. The method according to claim 5, wherein: The H2S absorption includes: a first H2S absorption and a second H2S absorption; The first H2S absorption process includes: contacting the synthesis gas with the first stream of H2S-rich methanol and performing the first H2S absorption to obtain the second H2S-rich methanol and the pre-desulfurized gas; the second H2S absorption process includes: contacting the pre-desulfurized gas, the low H2S methanol and the first stream of CO2-rich methanol and performing the second H2S absorption to obtain the desulfurized gas and the first H2S-rich methanol; and / or, the molar content of H2S in the synthesis gas is 0.3-0.4%, the molar content of CO2 is 40-46%; the temperature is -25 to -15°C, and the pressure is 3.12-3.15MPa(G); and / or, the molar flow ratio of the synthesis gas to the first stream of H2S-rich methanol is 50-60:1; and / or, the molar content of H2S in the second H2S-rich methanol is 0.6-0.9%, and the molar content of CO2 is 30-36%; and / or, dividing the first H2S-rich methanol into the first stream of H2S-rich methanol and the second stream of H2S-rich methanol at a molar flow ratio of 1:45-55; and / or, the molar content of H2S in the first H2S-rich methanol is 0.3-0.5%, and the molar content of CO2 is 27-32%; And / or, the molar flow ratio of the synthesis gas to the low H2S methanol is 2.5-3:1; the molar flow ratio of the synthesis gas to the first stream of CO2-rich methanol is 1.8-2.2:

1.

7. The method according to claim 5 or 6, wherein: The CO2 absorption includes a first CO2 absorption and a second CO2 absorption; The first CO2 absorption process includes: contacting the desulfurized gas with CO2-containing methanol and performing the first CO2 absorption to obtain the CO2-rich methanol and pre-purified gas; the second CO2 absorption process includes: contacting the pre-purified gas, the first stream of low-carbon methanol and lean methanol and performing the second CO2 absorption to obtain purified gas and the CO2-containing methanol; and / or, dividing the CO2-rich methanol into the first stream of CO2-rich methanol and the second stream of CO2-rich methanol at a molar flow ratio of 1:2.3-2.8; And / or, the molar content of CO2 in the CO2-rich methanol is 16-20%, the molar content of H2S is 0.1-0.5 ppm; the pressure is 3.05-3.1 MPa(G); and / or, the molar flow ratio of the purified gas to the CO2-containing methanol is 1:2.6-3.1; and / or, the molar flow ratio of the purified gas to the first stream of low-carbon methanol is 1:1-1.2; the molar flow ratio of the purified gas to lean methanol is 1:1.4-1.6; and / or, the molar content of H2S in the purified gas is less than 0.1ppm, the molar content of CO2 is less than 20ppm; the temperature is -55 to -50°C, and the pressure is 3-3.05MPa(G); and / or, the molar content of H2S in the CO2-containing methanol is 0.1-0.5 ppm, and the molar content of CO2 is 9-14%; and / or, according to the material flow direction, the CO2-containing methanol is cooled to -36 to -33°C for the third time and then returned to the first CO2 absorption; And / or, the first stream of CO2-rich methanol is cooled to -48 to -44°C for the fourth time and then returned to perform the H2S absorption.

8. The method according to any one of claims 5 to 7, wherein: The pressures of the CO2 flash evaporation and the H2S flash evaporation are independently 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, and the molar content of CO2 is 15.5-19.5%; and / or, dividing the flashed CO2-rich methanol into the first stream of flashed CO2-rich methanol and the second stream of flashed CO2-rich methanol at a molar flow ratio of 3.4-3.8:1; and / or, the temperature of the CO2 flash gas is -25°C to -20°C and the pressure is 0.8-1MPa(G); and / or, the molar content of H2S in the H2S-rich methanol after the flash evaporation is 0.3-0.5%, and the molar content of CO2 is 26.5-31.5%; the temperature is -25 to -20°C; and / or, the molar content of H2S in the low-sulfur and carbon-rich methanol is 0.6-1.2‰, and the molar content of CO2 is 18-22%; and / or, the low-sulfur and carbon-rich methanol is subjected to a fifth cooling to -52 to -48°C, and then subjected to the second flash distillation; And / or, the flash gas obtained by the first washing has a temperature of -25 to -20°C and a pressure of 0.8 to 1 MPa(G).

9. The method according to any one of claims 5 to 8, wherein: The heat exchange process includes: performing heat exchange on the CO2-rich methanol after flash evaporation and the first stream of semi-lean methanol to obtain CO2-rich methanol after heat exchange and semi-lean methanol after heat exchange; Wherein, the temperature of CO2-rich methanol after the heat exchange is -30 to -26°C; the temperature of semi-lean methanol after the heat exchange is -46 to -42°C; And / or, the temperature of the material after the sixth cooling is -36 to -33°C; And / or, the temperature of the first cooled material is -55 to -50°C; and / or, the pressure of the first flash evaporation is 0.05-0.08 MPa(G), the pressure of the second flash evaporation is 0.06-0.09 MPa(G), and the pressure of the third flash evaporation is 0.12-0.16 MPa(G); and / or, the molar content of CO2 in the semi-lean methanol is 10-14%, 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, dividing the semi-lean methanol into the first stream of semi-lean methanol and the second stream of semi-lean methanol at a molar flow ratio of 3-3.5:1; and / or, the molar content of H2S in the low H2S methanol is 1.5-2.5‰, the molar content of CO2 is 15-20%; the temperature is -56 to -53°C, and the pressure is 0.12-0.16MPa(G); and / or, the low H2S methanol is first pressurized to 3.5-3.6 MPa(G) and then returned to perform the H2S absorption; And / or, the temperature of the second cooled material is -34 to -30°C; And / or, the third H2S-rich methanol obtained by the third flash evaporation has a molar content of H2S of 0.3-0.4%, a molar content of CO2 of 15-20%, a temperature of -62 to -58°C, and a pressure of 0.13-0.17 MPa(G); And / or, the first CO2 product gas obtained by the first flash evaporation, the second CO2 product gas obtained by the second flash evaporation and the third CO2 product gas obtained by the second washing are mixed, and the molar content of H2S in the obtained CO2 product gas is less than 1ppm, and the molar content of CO2 is 99.4-99.7%; the temperature is -56 to -53°C, and the pressure is 0.05-0.08MPa(G).

10. The method according to any one of claims 5 to 9, wherein: The stripping process comprises: contacting the first stream of semi-lean methanol with nitrogen after heat exchange and performing stripping to obtain the low-carbon methanol and tail gas; And / or, the molar content of H2S in the low-carbon methanol is ≤0.5ppm, the molar content of CO2 is 5-7%; the temperature is -55 to -50°C; the pressure is 0.15-0.25MPa(G); and / or, dividing the low-carbon methanol into the first stream of low-carbon methanol and the second stream of low-carbon methanol at a molar flow ratio of 7.5-8.5:1; and / or, after the low-carbon methanol is pressurized to 3.5-3.6 MPa(G) for the second time, it is divided into the first stream of low-carbon methanol and the second stream of low-carbon methanol, which are then returned to perform the CO2 absorption and the first washing respectively; And / or, the molar content of H2S in the tail gas is ≤0.5ppm, the molar content of CO2 is 83-88%; the temperature is -48 to -44°C; and the pressure is 0.15-0.25MPa(G).

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