Synthesis gas purification method matched with coal water slurry gasification device and purification 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 coal water slurry gasification device and a purification device thereof. According to the method, the medium-pressure flash evaporation process is optimally configured, the method has the advantages of small occupied area of first-stage flash evaporation equipment, low flash evaporation gas recovery energy consumption and the like, flash evaporation gas generated by second-stage flash evaporation is washed and absorbed by low H2S methanol, absorption of H2S methanol to CO2 gas in the synthesis gas in an H2S absorption tower can be effectively reduced, pollution of H2S-rich methanol to CO2 gas in the synthesis gas is reduced, and the method is suitable for industrial production. The comprehensive energy consumption of the low-temperature methanol washing device is favorably 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 coal water slurry gasification device and a device for purifying syngas for a coal water slurry gasification device. Background Art

[0002] In the syngas produced by using the coal water slurry 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. The acidic 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, and utilizes the characteristic that low-temperature methanol has a great solubility for acidic gases to physically absorb and remove H 2 S and CO 2 and other gases in the syngas, and at the same time removes trace components such as HCN and NH 3 to purify the syngas and create good prerequisites for subsequent synthesis reactions.

[0004] The innovative research on acidic gas removal technology mainly focuses on two aspects. Firstly, it is on strengthening heat and mass transfer, and secondly, it is on the optimized utilization of rich CO 2 methanol. In recent years, the research and optimization work in these two aspects have played an active role in reducing the comprehensive energy consumption of low-temperature methanol washing, but there are technical bottlenecks in the continuous optimized utilization of rich CO 2 methanol. Therefore, it is necessary to adjust the innovation and optimization direction of the low-temperature methanol washing process system. Since rich CO 2 methanol can optimize and reduce the comprehensive energy consumption, does the H 2 S-containing methanol also have this potential and possibility.

[0005] CN201110260570.0 discloses a low-temperature methanol washing process. Firstly, in this low-temperature methanol washing process, the entire H 2 S absorption tower uses rich CO 2 methanol to wash the syngas, and does not study and recycle the low H 2 S-containing methanol solution existing in the system, and does not allow it to undertake part of the potential of absorbing H 2 S gas in the syngas. Because the rich CO 2 methanol that has absorbed H2 The methanol becomes rich in H 2 S methanol and cannot be regenerated by simple pressure reduction flashing. Instead, it requires steam consumption in a thermal regeneration system for regeneration. The regenerated lean methanol has a relatively high temperature and needs to consume cooling water and other low-temperature cooling capacities for cooling before it can be recycled. Therefore, in H 2 S absorption tower, rich in CO 2 A large consumption of methanol necessarily results in high energy consumption; secondly, in the CO 2 flashing section of the reabsorption tower, rich in CO 2 methanol directly mixes with the rich H 2 S methanol flash gas while washing the rich H 2 S methanol, and itself is deeply contaminated by the rich H 2 S methanol. The mixed low-concentration H 2 S methanol is not fully utilized either and is sent to the thermal regeneration system for regeneration. Generally, it 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 syngas purification method for a coal water slurry gasification device and a syngas purification device for a coal water slurry gasification device. By optimizing the configuration of the medium-pressure flashing process, this method has the advantages of a small footprint of the primary flashing equipment and low energy consumption for flash gas recovery. The flash gas generated by the secondary flashing is washed and absorbed using low H 2 S methanol, which can effectively reduce H 2 S methanol in the H 2 S absorption tower for absorbing CO 2 in the syngas, reducing the pollution of the rich H 2 S methanol to CO 2 in the syngas, and is conducive to reducing the overall energy consumption of the cold methanol washing unit.

[0007] To achieve the above object, the first aspect of the present invention provides a syngas purification method for a coal water slurry gasification device, and the purification method includes:

[0008] Performing H 2 S absorption on the syngas to obtain first rich H 2 S methanol and desulfurized gas; performing CO 2 absorption on the desulfurized gas to obtain rich CO 2 methanol in two streams; cooling the second stream of rich CO 2 methanol by the first cooler and then performing primary CO 2 flashing and secondary CO 2 flashing to obtain the flashed rich CO 2 methanol in two streams, the first stream of flashed rich CO 2The methanol undergoes a first flash evaporation to obtain semi-lean methanol; the second stream of rich CO 2 The methanol undergoes a second flash evaporation after the second cooling;

[0009] The first rich H 2 S methanol undergoes a third cooling and then successively undergoes a first-stage H 2 S flash evaporation and a second-stage H 2 S flash evaporation, and the flashed rich H 2 S methanol undergoes a third flash evaporation to obtain the H 2 S-containing gas phase and the flashed solution obtained from the second flash evaporation are subjected to a first washing to obtain low-H 2 S methanol;

[0010] Among them, the second-stage CO 2 flash evaporation also obtains the second-stage CO 2 flash gas and the second-stage H 2 S flash evaporation also obtains the second-stage H 2 S flash gas. After mixing, they are subjected to a second washing with the low-H 2 S methanol, and the obtained H 2 S-containing methanol returns and undergoes the H 2 S absorption.

[0011] The second aspect of the present invention provides a syngas purification device for a coal water slurry gasification device. The purification device includes: an H 2 S absorption tower, a CO 2 absorption tower, a first-stage flash evaporation tower, a second-stage flash evaporation tower, and a reabsorption tower, as well as a first cooler, a second cooler, and a third cooler; the first-stage flash evaporation tower includes a first-stage CO 2 flash evaporation section provided thereon and a first-stage H 2 S flash evaporation section provided below; the second-stage flash evaporation tower includes a second-stage CO 2 flash evaporation section provided thereon and a second-stage H 2 S flash evaporation section provided below;

[0012] Among them, the syngas enters the H 2 S absorption tower to obtain the first rich H 2 S methanol and the desulfurized gas; the desulfurized gas enters the CO 2 absorption tower, and the obtained rich CO 2 methanol is divided into two streams. The second stream of rich CO 2 methanol, after passing through the first cooler, successively enters the first-stage CO 2 flash evaporation section and the second-stage CO 2 flash evaporation section, and the flashed rich CO 2 methanol is divided into two streams. The first stream of flashed rich CO 2Methanol enters the upper part of the reabsorption tower for the first flash evaporation to obtain semi-lean methanol; the second flash evaporation produces rich CO 2 After passing through the second cooler, the methanol enters the middle part of the reabsorption tower for the second flash evaporation;

[0013] The first rich H 2 S methanol, after passing through the third cooler, sequentially enters the first-stage H 2 S flash evaporation section and the second-stage H 2 S flash evaporation section, and the flash-evaporated rich H 2 S methanol enters the lower part of the reabsorption tower for the third flash evaporation, and the obtained H 2 S-containing gas phase is subjected to the first washing with the flash-evaporated solution obtained from the second flash evaporation, and the obtained low H 2 S methanol enters the second-stage H 2 S flash evaporation section, and is subjected to the second washing with the second-stage CO 2 flash gas and the second-stage H 2 S flash gas obtained from the second-stage H 2 S flash evaporation. The obtained H 2 S-containing methanol is recycled and used for the H 2 S absorption tower. 2 Compared with the prior art, the present invention has the following advantages:

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] (1) In the method provided by the present invention, the two-stage medium-pressure flash evaporation technology is adopted. The pressure of the first-stage flash evaporation (i.e., the first-stage CO 2 flash evaporation and the first-stage H 2 S flash evaporation) is relatively high, and more effective gas is flashed out. The first-stage flash gas can be directly sent to the second stage of the compressor in the compression process, reducing the power consumption of the compressor; the pressure of the second-stage flash evaporation (i.e., the second-stage CO 2 flash evaporation and the second-stage H 2 S flash evaporation) is relatively low, ensuring the recovery of the effective gas in the second rich CO 2 methanol and the first rich H 2 S methanol;

[0016] (2) In the method provided by the present invention, the reabsorption process is optimized, realizing the absorption of the flash liquid of the second rich CO 2 methanol after the second flash evaporation on the H 2 S-containing gas phase generated by the flash-evaporated rich H 2 S methanol, making the H 2 S content in the solution lower, which is called low H 2 S methanol, but without mixing with the third rich H 2 S methanol after flash evaporation;

[0017] At the same time, the introduction of low H 2S methanol is used to absorb the secondary flash gas, and the content of CO gas is increased with a slight increase in the H2S concentration in the S methanol. Since the increase in the CO gas concentration in the H2S-containing methanol reduces the absorption of CO gas in the H2S absorption process, as much CO gas as possible is absorbed in the CO absorption process. Correspondingly, the CO gas flashed out from the first rich H2S methanol is reduced, so the amount of the solution used for washing the H2S-containing gas phase after flashing is also reduced accordingly, and the rich H2S methanol for heat regeneration is also reduced, which has a positive significance for reducing the comprehensive energy consumption of the low-temperature methanol washing unit. 2 H2S in S methanol 2 With a slight increase in the H2S concentration in the S methanol, the content of CO gas is increased. 2 Since the increase in the CO gas concentration in the H2S-containing methanol reduces the absorption of CO gas in the H2S absorption process, as much CO gas as possible is absorbed in the CO absorption process. 2 CO gas in H2S-containing methanol 2 With the increase in the CO gas concentration, the absorption of CO gas in the H2S absorption process is reduced. 2 CO gas in the H2S absorption process 2 As much CO gas as possible is absorbed in the CO absorption process. 2 CO gas 2 In the CO absorption process, correspondingly, the CO gas flashed out from the first rich H2S methanol is reduced. 2 CO gas flashed out from the first rich H2S methanol 2 Then, the amount of the solution used for washing the H2S-containing gas phase after flashing is also reduced accordingly. 2 The rich H2S methanol for heat regeneration is also reduced, which has a positive significance for reducing the comprehensive energy consumption of the low-temperature methanol washing unit. 2

[0018] (3) The method provided by the present invention preferably uses the H2S absorption process. By introducing the H2S-containing methanol to absorb H2S and CO gas in the syngas, the recycling of the H2S-containing methanol is realized, the usage amount of the first rich CO methanol is reduced, which is equivalent to reducing the rich H2S methanol that needs heat regeneration. 2 H2S absorption process 2 By introducing the H2S-containing methanol to absorb H2S and CO gas in the syngas 2 H2S and CO gas 2 The recycling of the H2S-containing methanol is realized. 2 The usage amount of the first rich CO methanol is reduced. 2 Which is equivalent to reducing the rich H2S methanol that needs heat regeneration. 2 H2S methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. is a schematic structural diagram of a syngas purification device supporting a water coal gasification device provided by the present invention.

[0020] DESCRIPTION OF THE REFERENCE NUMERALS

[0021] T-1, H2S absorption tower; T-2, CO absorption tower; T-3, first flash tower; T-4, second flash tower; T-5, reabsorption tower; 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; P-4, fourth pump; 2 T-1, H2S absorption tower; T-2, CO absorption tower; 2 T-3, first flash tower; T-4, second flash tower; T-5, reabsorption tower; 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; P-4, fourth pump;

[0022] 1, syngas; 2, H2S-containing methanol; 2-i, the first H2S-containing methanol; 2-ii, the second H2S-containing methanol; 3, the second rich H2S methanol 2 H2S-containing methanol 2 The first H2S-containing methanol 2 The second H2S-containing methanol 2 ​S Methanol; 4, Rich in CO 2 Methanol; 4-i, The first rich CO 2 Methanol; 4-ii, The second rich CO 2 Methanol; 5, The first rich in H 2 S Methanol; 6, Desulfurized gas; 7, Containing CO 2 Methanol; 8, Semi-lean liquid methanol; 8-i, The first semi-lean liquid methanol; 8-ii, The second semi-lean liquid methanol; 9, Lean methanol; 10, Rich CO after the first-stage flash evaporation 2 Methanol; 11, First-stage flash evaporation gas; 11-i, First-stage CO 2 Flash evaporation gas; 11-ii, First-stage H 2 S Flash evaporation gas; 12, Rich CO after flash evaporation 2 Methanol; 12-i, The first rich CO after flash evaporation 2 Methanol; 12-ii, The second rich CO after flash evaporation 2 Methanol; 13, Second-stage CO 2 Flash evaporation gas; 14, Rich H after the first-stage flash evaporation 2 S Methanol; 15, Second-stage flash evaporation gas; 16, Rich H after flash evaporation 2 S Methanol; 17, The third rich in H 2 S Methanol; 18, CO 2 Product gas; 19, Purified gas; 20, Low in H 2 S Methanol. Detailed implementation manners

[0023] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and 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.

[0024] 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, in "first cooling", "second cooling", "third cooling", "fourth cooling" and "fifth cooling", "first", "second", "third", "fourth" and "fifth" are only used to indicate that these are not the same cooling.

[0025] In the present invention, unless otherwise specified, 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.

[0026] The first aspect of the present invention provides a method for purifying syngas for a coal water slurry gasification device, and the purification method includes:

[0027] Subjecting the syngas to H 2 S absorption to obtain first-stage H 2 S-rich methanol and desulfurized gas; subjecting the desulfurized gas to CO 2 absorption to obtain two streams of CO 2 -rich methanol; subjecting the second stream of CO 2 -rich methanol to first cooling and then successively to first-stage CO 2 flashing and second-stage CO 2 flashing to obtain two streams of flashed CO 2 -rich methanol; subjecting the first stream of flashed CO 2 -rich methanol to first flashing to obtain semi-lean methanol; subjecting the second stream of flashed CO 2 -rich methanol to second cooling and then to second flashing;

[0028] Subjecting the first-stage H 2 S-rich methanol to third cooling and then successively to first-stage H 2 S flashing and second-stage H 2 S flashing to obtain flashed H 2 S-rich methanol, subjecting the obtained H 2 S-containing gas phase to first washing with the flashed solution obtained from the second flashing to obtain low-H 2 S methanol;

[0029] Among them, the second-stage CO 2 flashing also obtains second-stage CO 2 flashed gas, and the second-stage H 2 S flashing also obtains second-stage H 2 S flashed gas. After mixing, the mixture is subjected to second washing with the low-H 2 S methanol to obtain H 2 S-containing methanol, which is returned and subjected to the above-mentioned H 2 S absorption.

[0030] In some embodiments of the present invention, preferably, the first stream of CO 2 -rich methanol is returned and subjected to the above-mentioned H 2H₂S Absorption. In the present invention, the CO-rich 2 methanol is divided into two streams. The first stream returns and undergoes the H 2 ₂S absorption; the second stream successively undergoes primary CO 2 flash evaporation and secondary CO 2 flash evaporation.

[0031] In some embodiments of the present invention, preferably, the H 2 ₂S-containing methanol is first pressurized to 5.8 - 6 MPa(G) and then returns to undergo the H 2 ₂S absorption.

[0032] In some embodiments of the present invention, preferably, the semi-lean methanol is divided into two streams. The first stream of semi-lean methanol returns to undergo the CO 2 absorption. In the present invention, the second stream of semi-lean methanol is sent to subsequent processes for treatment.

[0033] In some embodiments of the present invention, preferably, the process of H 2 ₂S absorption includes: contacting the syngas with the first stream of H 2 ₂S-containing methanol and performing the first H 2 ₂S absorption to obtain pre-washed syngas and a second H 2 ₂S-rich methanol; contacting the pre-washed syngas, the second stream of H 2 ₂S-containing methanol, and the first stream of CO 2 -rich methanol and performing the second H 2 ₂S absorption to obtain the first H 2 ₂S-rich methanol and desulfurized gas.

[0034] In the present invention, without special instructions, the H 2 ₂S-containing methanol is divided into two streams. Preferably, the H 2 ₂S-containing methanol is divided into the first stream of H 2 ₂S-containing methanol and the second stream of H 2 ₂S-containing methanol with a molar flow rate ratio of 1:11 - 13.

[0035] In some embodiments of the present invention, preferably, the molar content of H 2 ₂S in the syngas is 0.9 - 1.2%, and the molar content of CO 2 is 40 - 50%; the temperature is -15 to -5 °C, and the pressure is 5.2 - 5.7 MPa(G).

[0036] 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 upstream syngas cooling process.

[0037] In some embodiments of the present invention, preferably, the molar flow rate ratio of the syngas and the first stream of H 2 S-containing methanol is 70-80:1.

[0038] In the present invention, the first H 2 S absorption is intended 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 second H 2 S-containing methanol is 2.5-3.5%, and the molar content of CO 2 is 70-75%. In the present invention, the temperature of the second H 2 S-containing methanol is -15 to -5 °C, and the pressure is 5.2-5.7 MPa(G).

[0039] In some embodiments of the present invention, preferably, the molar flow rate ratio of the syngas and the second stream of H 2 S-containing methanol is 5-7:1.

[0040] In some embodiments of the present invention, preferably, the molar flow rate ratio of the syngas and the first stream of CO 2 -rich methanol is 2-3:1.

[0041] In the present invention, the second H 2 S absorption is intended 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 first H 2 S-rich methanol is 1.5-2%, and the molar content of CO 2 is 40-45%; the temperature is -20 to -10 °C, and the pressure is 5.3-5.4 MPa(G).

[0042] In some embodiments of the present invention, preferably, the molar content of H 2 S in the desulfurized gas is 0.5-1 ppm, and the molar content of CO 2 is 36-40%; the temperature is -20 to -10 °C; the pressure is 5.3-5.4 MPa(G).

[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 the first CO 2 absorption to obtain a pre-purified gas and a CO 2Methanol; bringing the pre-purified gas, the first semi-lean methanol, and lean methanol into contact for a second CO 2 absorption to obtain a purified gas and the CO 2 -containing methanol.

[0044] In some embodiments of the present invention, preferably, the molar flow rate ratio of the desulfurized gas to the CO 2 -containing methanol is 1:1.2 - 1.5.

[0045] In the present invention, the first CO 2 absorption aims to further remove CO from the desulfurized gas 2 . Preferably, the molar content of CO in the CO-rich 2 methanol is 30 - 36%, the molar content of H 2 S is 0.1 - 0.5 ppm; the temperature is -15 to -10 °C, and the pressure is 5.3 - 5.4 MPa(G). 2 S is 0.1 - 0.5 ppm; the temperature is -15 to -10 °C, and the pressure is 5.3 - 5.4 MPa(G).

[0046] In some embodiments of the present invention, preferably, the molar flow rate ratio of the first CO-rich 2 methanol to the second CO-rich 2 methanol is 1:2 - 2.4.

[0047] In some embodiments of the present invention, preferably, after the first CO-rich 2 methanol is sequentially pressurized to 5.8 - 6 MPa(G) for the second time and cooled to -36 to -33 °C for the fourth time, it is returned for the H 2 S absorption.

[0048] In some embodiments of the present invention, preferably, after the CO 2 -containing methanol is cooled to -36 to -33 °C for the fifth time, it is returned for the first CO 2 absorption.

[0049] In some embodiments of the present invention, preferably, the molar flow rate ratio of the purified gas to the first semi-lean methanol is 1.5 - 1.7:1.

[0050] In some embodiments of the present invention, preferably, the molar flow rate ratio of the purified gas to the lean methanol is 1:1 - 1.2.

[0051] In some embodiments of the present invention, preferably, the molar content of H 2 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 5.2 - 5.3 MPa(G).

[0052] In the present invention, the first cooling is achieved by lowering the temperature of the second stream of CO-rich 2 methanol, aiming to reduce the total amount of medium-pressure flash gas and lay a foundation for obtaining low temperature (high-quality cold energy) for the reabsorption column. Preferably, the temperature of the material after the first cooling is -36 to -33 °C.

[0053] In some embodiments of the present invention, preferably, the process of the first-stage CO 2 flash evaporation includes: subjecting the material after the first cooling to the first-stage CO 2 flash evaporation to obtain CO-rich 2 methanol after the first-stage flash evaporation.

[0054] In the present invention, the third cooling is achieved by lowering the temperature of the first H-rich 2 S methanol, aiming to reduce the total amount of medium-pressure flash gas and lay a foundation for obtaining low temperature (high-quality cold energy) for the reabsorption column. Preferably, the temperature of the material after the third cooling is -33 to -30 °C.

[0055] In some embodiments of the present invention, preferably, the process of the first-stage H 2 S flash evaporation includes: subjecting the material after the third cooling to the first-stage H 2 S flash evaporation to obtain H-rich 2 S methanol after the first-stage flash evaporation.

[0056] In some embodiments of the present invention, preferably, the pressures of the first-stage CO 2 flash evaporation and the first-stage H 2 S flash evaporation are each independently 3.5 - 3.7 MPa (G). In the present invention, the first-stage CO 2 flash evaporation and the first-stage H 2 S flash evaporation can be carried out in the same flash column or in different flash columns.

[0057] In some embodiments of the present invention, preferably, the molar content of H 2 S in the CO-rich 2 methanol after the first-stage flash evaporation is 0.1 - 0.5 ppm, and the molar content of CO 2 is 29.5 - 35.5%; the temperature is -36.5 to -33.5 °C.

[0058] In some embodiments of the present invention, preferably, the molar content of H 2 S in the H-rich 2 S methanol after the first-stage flash evaporation is 1.5 - 2%, and the molar content of CO 2 is 39.5 - 43.5%; the temperature is -33.5 to -30.5 °C.

[0059] In some embodiments of the present invention, preferably, the primary flash gas includes the primary CO 2 The primary CO obtained by flash evaporation 2 The flash gas and the primary H 2 The primary H obtained by flash evaporation of S 2 The flash gas of S, and the molar content of H 2 in the primary flash gas is 0.1-0.2%, and the molar content of CO 2 is 23-28%, and the molar content of H 2 is 68-75%; the temperature is -40 to -30 °C, and the pressure is 3.5-3.7 MPa(G).

[0060] In some embodiments of the present invention, preferably, the process of the secondary CO 2 flash evaporation includes: subjecting the CO-rich methanol after the primary flash evaporation to the secondary CO 2 flash evaporation to obtain the CO-rich methanol after flash evaporation and the secondary CO 2 flash gas 2 methanol and the secondary CO 2 flash gas

[0061] In some embodiments of the present invention, preferably, the process of the secondary H 2 S flash evaporation includes: subjecting the H-rich methanol after the primary flash evaporation to the secondary H 2 S flash evaporation to obtain the H-rich methanol after flash evaporation and the secondary H 2 S flash gas 2 methanol and the secondary H 2 S flash gas

[0062] In some embodiments of the present invention, preferably, the pressures of the secondary CO 2 flash evaporation and the secondary H 2 S flash evaporation are each independently selected from 1.6-2 MPa(G). In the present invention, the secondary CO 2 flash evaporation and the secondary H 2 S flash evaporation can be carried out in the same flash tower or in different flash towers

[0063] In some embodiments of the present invention, preferably, the molar content of H 2 in the CO-rich methanol after flash evaporation is 0.1-0.5 ppm, and the molar content of CO 2 is 29-35%; the temperature is -40 to -30 °C 2

[0064] In some embodiments of the present invention, preferably, the molar content of H 2 in the H-rich methanol after flash evaporation is 1.5-2%, and the molar content of CO 2 is 2 ​The molar content is 38 - 42%; the temperature is -35 to -30 °C.

[0065] In the invention, the second washing is carried out by increasing the low H 2 CO in HS methanol 2 content, so that its absorption of CO in syngas is reduced during the H 2 S absorption process. Preferably, the molar content of H 2 S in the HS methanol is 0.9 - 1.1%, and the molar content of CO 2 is 28 - 32%; the temperature is -65 to -60 °C. 2 S in the HS methanol is 0.9 - 1.1%, and the molar content of CO 2 is 28 - 32%; the temperature is -65 to -60 °C.

[0066] In some embodiments of the present invention, preferably, the temperature of the secondary flash gas obtained by the second washing is -65 °C to -60 °C, and the pressure is 1.6 - 2 MPa(G).

[0067] In some embodiments of the present invention, preferably, the molar flow ratio of the CO 2 rich methanol after the first flash and the CO 2 rich methanol after the second flash is 3.5 - 4:1.

[0068] In the present invention, the first flash aims to flash the CO 2 rich methanol after the first flash to obtain the first CO 2 product gas and semi-lean methanol. Preferably, the pressure of the first flash is 0.05 - 0.08 MPa(G).

[0069] In some embodiments of the present invention, preferably, the molar content of CO 2 in the semi-lean methanol is 22 - 25%, and the molar content of H 2 S is ≤0.5 ppm; the temperature is -66 to -63 °C; the pressure is 0.05 - 0.08 MPa(G).

[0070] In some embodiments of the present invention, further 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 ratio of 1.2 - 1.5:1. In the present invention, the first stream of semi-lean methanol returns and undergoes the CO 2 absorption, and the second stream of semi-lean methanol is sent to the subsequent process.

[0071] In some embodiments of the present invention, further preferably, after the first stream of semi-lean methanol is pressurized to 5.8 - 6 MPa(G) by the third stage, it returns and undergoes the CO 2 absorption.

[0072] In the present invention, the second cooling reduces the temperature of the second rich CO methanol after flashing, generates low temperature through pressure reduction flashing, improves the absorption capacity of the rich CO methanol after flashing for H₂S gas, and is conducive to washing H₂S gas in the CO product gas after flashing. Preferably, the temperature of the material after the second cooling is -55 to -50 °C. 2 In the present invention, the second flashing aims to flash the cooled material to obtain a second CO product gas and a solution after flashing. Preferably, the pressure of the second flashing is 0.06 - 0.09 MPa (G). 2 2 2 2

[0073] In the present invention, the second flashing aims to flash the cooled material to obtain a second CO product gas and a solution after flashing. Preferably, the pressure of the second flashing is 0.06 - 0.09 MPa (G). 2 In the present invention, the second flashing aims to flash the cooled material to obtain a second CO product gas and a solution after flashing. Preferably, the pressure of the second flashing is 0.06 - 0.09 MPa (G).

[0074] In some embodiments of the present invention, preferably, the molar content of H₂S in the low-H₂S methanol is 0.9 - 1.1%, the molar content of CO is 25 - 28%; the temperature is -65 to -60 °C, and the pressure is 0.12 - 0.16 MPa (G). 2 2 2

[0075] In some embodiments of the present invention, further preferably, the low-H₂S methanol is pressurized to 2 - 2.4 MPa (G) for the fourth time and then subjected to the second washing. 2

[0076] In the present invention, the third flashing aims to flash the rich-H₂S methanol after flashing to obtain an H₂S-containing gas phase and a third rich-H₂S methanol. Preferably, the pressure of the third flashing is 0.12 - 0.16 MPa (G). 2 2 2 In the present invention, the third flashing aims to flash the rich-H₂S methanol after flashing to obtain an H₂S-containing gas phase and a third rich-H₂S methanol. Preferably, the pressure of the third flashing is 0.12 - 0.16 MPa (G).

[0077] In some embodiments of the present invention, preferably, the molar content of H₂S in the third rich-H₂S methanol obtained by the third flashing is 1.5 - 2%, the molar content of CO is 25 - 35%; the temperature is -69 to -65 °C; the pressure is 0.13 - 0.17 MPa (G). 2 2 2

[0078] In some embodiments of the present invention, preferably, the first CO product gas obtained by the first flashing, the second CO product gas obtained by the second flashing, and the third CO product gas obtained by the first washing are mixed to obtain a CO product gas; the CO 2 2 2 2 ​​​​​​​​​​​​​​​​​2 The molar content of H 2 S in the product gas is < 1 ppm, and the molar content of CO 2 is 99.4 - 99.7%; the temperature is -68°C to -63°C, and the pressure is 0.05 - 0.08 MPa(G).

[0079] The second aspect of the present invention provides a syngas purification device for a coal water slurry gasification device. The purification device includes: an H 2 S absorption tower T-1, a CO 2 absorption tower T-2, a first flash tower T-3, a second flash tower T-4, and a reabsorption tower T-5, as well as a first cooler E-1, a second cooler E-2, and a third cooler E-3;

[0080] The first flash tower T-3 includes a first-stage CO 2 flash section provided thereon and a first-stage H 2 S flash section provided below; the second flash tower T-4 includes a second-stage CO 2 flash section provided thereon and a second-stage H 2 S flash section provided below;

[0081] Among them, the syngas 1 enters the H 2 S absorption tower T-1 to obtain a first rich H 2 S methanol 5 and desulfurized gas 6; the desulfurized gas 6 enters the CO 2 absorption tower T-2 to obtain rich CO 2 methanol 4, which is divided into two streams. The second stream of rich CO 2 methanol 4-ii, after passing through the first cooler E-1, successively enters the first-stage CO 2 flash section and the second-stage CO 2 flash section to obtain the flashed rich CO 2 methanol 12, which is divided into two streams. The first stream of flashed rich CO 2 methanol 12-i enters the upper part of the reabsorption tower T-5 for the first flash to obtain semi-lean liquid methanol 8; the second stream of flashed rich CO 2 methanol 12-ii, after passing through the second cooler E-2, enters the middle part of the reabsorption tower T-5 for the second flash;

[0082] The first rich H 2 S methanol 5, after passing through the third cooler E-3, successively enters the first-stage H 2 S flash section and the second-stage H 2 S flash section to obtain the flashed rich H 2 S methanol 16, which enters the lower part of the reabsorption tower T-5 for the third flash to obtain the H 2 S-containing gas phase for the first washing with the flashed solution obtained from the second flash to obtain the low-H2 S methanol 20 enters the secondary H 2 S flash section, and reacts with the secondary CO 2 The secondary CO obtained from the flash evaporation is also 2 The flash gas 13 and the secondary H 2 The secondary H obtained from the flash evaporation is also 2 The flash gas undergoes a second washing to obtain the H-containing 2 S methanol 2 is recycled and reused in H 2 S absorption tower T-1.

[0083] In the present invention, as Figure 1 shown, the H 2 S absorption tower T-1 includes a first H disposed below 2 S absorption section and a second H disposed above 2 S absorption section. Specifically, the first H 2 S absorption section, the first stream of H-containing 2 S methanol 2-i pre-washes and absorbs H 2 S, HCN, NH 3 in the syngas 1; the second H 2 S absorption section absorbs H 2 S and CO in the pre-washed syngas by introducing a second stream of H-containing 2 S methanol 2-ii, realizing the recycling of H-containing 2 S methanol, reducing the usage amount of the first rich CO 2 methanol 4-i, which is equivalent to reducing the 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 tower, which is also of positive significance for reducing the usage amounts of lean methanol and semi-lean methanol in the CO 2 absorption tower. 2 absorption tower.

[0084] In the present invention, as Figure 1 shown, the H 2 S absorption tower T-1, the first H 2 S absorption section and the second H 2 S absorption section are connected by lift holes; the first H 2 S absorption section is connected to the H-containing 2 S methanol outlet of the secondary flash tower T-4, for contacting the syngas 1 with the first stream of H-containing 2 S methanol 2-i and performing the first H 2 S absorption to obtain the second rich H 2 S methanol 5 and the pre-washed syngas; the second H 2 S absorption section is connected to the H-containing 2The methanol outlet for S is in connection with the CO 2 rich in CO of the absorption tower T-2 2 methanol outlet, for successively bringing the pre-washed syngas into contact with a second stream containing H 2 methanol for S 2-ii, the first rich in CO 2 methanol 4-i and performing a second H 2 S absorption to obtain the desulfurized gas 6 and the first rich in H 2 methanol for S 5.

[0085] In some embodiments of the present invention, preferably, the H 2 In the S absorption tower T-1, the number of trays in the first H 2 S absorption section is 12 - 18 trays, and the number of trays in the second H 2 S absorption section is 60 - 80 trays.

[0086] In the present invention, without special description, in the first H 2 S absorption section, the contact mode between the syngas and the first stream containing H 2 methanol for S 2-i is preferably countercurrent contact between the syngas 1 and the first stream containing H 2 methanol for S 2-i, that is, the syngas 1 enters from the bottom of the first H 2 S absorption section, and the first stream containing H 2 methanol for S 2-i enters from the upper part of the first H 2 S absorption section.

[0087] In the present invention, as Figure 1 shown, the CO 2 absorption tower T-2 is divided into a first CO 2 absorption section and a second CO 2 absorption section from bottom to top.

[0088] In the present invention, as Figure 1 shown, the CO 2 absorption tower T-2 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 through riser holes, 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 bringing the desulfurized gas 6 into contact with the methanol 7 containing CO 2 and performing the first CO 2 absorption to obtain the rich in CO 2 methanol 4 and the pre-purified gas; the second CO 2The absorption section is connected to the semi-lean methanol outlet of the reabsorption tower T-5 and the lean methanol 9 from the subsequent process, and is used to successively contact the pre-purified gas with the first stream of semi-lean methanol 8-i and lean methanol 9 and perform a second CO 2 absorption to obtain the purified gas 19 and the CO 2 -containing methanol 7.

[0089] In some embodiments of the present invention, preferably, in the CO 2 absorption tower T-2, the number of trays in the first CO 2 absorption section is 9-12, and the number of trays in the second CO 2 absorption section is 60-80.

[0090] In the present invention, without special instructions, in the CO 2 absorption tower T-2, in the first CO 2 absorption section, the contact mode between the desulfurized gas 6 and the CO 2 -containing methanol 7 is preferably selected from the countercurrent contact between the desulfurized gas 6 and the CO 2 -containing methanol 7; that is, the desulfurized gas 6 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.

[0091] In the present invention, as Figure 1 shown, in the primary flash tower T-3, the primary CO 2 flash section is used to perform a primary CO 2 flash on the second stream of CO 2 -rich methanol 4-ii after the first cooling to obtain the CO 2 -rich methanol 10 after the primary flash and the primary CO 2 flash gas 11-i; the primary H 2 S flash section is used to perform a primary H 2 S flash on the first H 2 S-rich methanol 5 after the third cooling to obtain the H 2 S-rich methanol 14 after the primary flash and the primary H 2 S flash gas 11-ii, where the primary flash gas 11 includes the primary CO 2 flash gas 11-i and the primary H 2 S flash gas 11-ii.

[0092] In the present invention, as Figure 1 shown, in the secondary flash tower T-4, the secondary CO 2 flash section is used to perform a secondary CO 2 flash on the CO 2 -rich methanol 10 after the primary flash to obtain the CO2 Methanol 12 and secondary CO 2 Flash vapor 13; secondary H 2 The S flash section is used to subject the H-rich methanol 14 after the first-stage flash to a secondary H 2 S flash to obtain the H-rich methanol 16 and secondary H 2 S flash vapor after the flash. Among them, the secondary CO 2 S methanol 16 and secondary H 2 S flash vapor are mixed, and then mixed with the low-H 2 Flash vapor 13 and secondary H 2 S flash vapor, and then subjected to a second washing with the low-H 2 S methanol 20 to obtain the H-containing 2 S methanol 2 and secondary flash vapor 15.

[0093] In the present invention, as Figure 1 shown, the upper and middle parts of the reabsorption tower T-5 are connected by lifting holes, and the middle and lower parts are also connected by lifting holes. Specifically, the upper part is used to subject the first flash H-rich CO 2 Methanol 12-i to the first flash to obtain semi-lean liquid methanol 8 and the first CO 2 Product gas; the middle part is used to subject the second flash H-rich CO 2 Methanol 12-ii to the second flash after the second cooling to obtain the flashed solution and the second CO 2 Product gas; the lower part is used to subject the H-rich methanol 16 after the flash to a third flash to obtain the third H-rich 2 S methanol 17 and the H-containing 2 S gas phase; among them, the H-containing 2 S gas phase and the flashed solution are washed to obtain the low-H 2 S methanol 20 and the third CO 2 Product gas; the CO 2 Product gas 18 includes the first CO 2 Product gas, the second CO 2 Product gas, and the third CO 2 Product gas. 2 Product gas.

[0094] In the present invention, as Figure 1 shown, preferably, the H-containing 2 S methanol outlet of the secondary flash tower T-4 is respectively connected to the first H 2 S absorption section and the second H 2 S absorption section, and is used to divide the H-containing 2 S methanol 2 into two streams, which are respectively returned and subjected to the first H 2 S absorption and the second H 2 S absorption.

[0095] In the present invention, as Figure 1As shown, preferably, the CO 2 rich CO of the absorption tower T-2 2 methanol outlet is connected to the second H 2 S absorption section for returning the first stream of rich CO 2 methanol 4-i and performing the second H 2 S absorption.

[0096] In the present invention, as Figure 1 shown, preferably, the CO 2 in the absorption tower T-2, the bottom of the second CO 2 absorption section is connected to the upper part of the first CO 2 absorption section for returning the CO-containing 2 methanol 7 and performing the first CO 2 absorption.

[0097] In the present invention, as Figure 1 shown, preferably, the semi-lean liquid methanol outlet of the reabsorption tower T-5 is connected to the second CO 2 absorption section for returning the first stream of semi-lean liquid methanol 8-i and performing the second CO 2 absorption.

[0098] In the present invention, as Figure 1 shown, preferably, on the pipeline connecting the H 2 S methanol outlet of the secondary flash tower T-4 and the H 2 S absorption tower T-1, a first pump P-1 is provided for dividing the H 2 S-containing methanol 2 into two streams after the first pressurization, and respectively recycling them back to the first H 2 S absorption section and the second H 2 S absorption section.

[0099] In the present invention, as Figure 1 shown, preferably, in the direction of material flow, on the pipeline connecting the rich CO 2 methanol outlet of the absorption tower T-2 and the second H 2 S absorption section, a second pump P-2 and a fourth cooler E-4 are successively provided for successively pressurizing and cooling the first stream of rich CO 2 methanol 4-i by the second pressurization and the fourth cooling, and then returning it to perform the second H 2 S absorption. 2 S absorption.

[0100] In the present invention, as Figure 1 shown, preferably, in the direction of material flow, on the pipeline connecting the second CO 2 absorption section and the first CO 2 absorption section, a fifth cooler E-5 is provided for cooling the CO-containing2 After the methanol 7 is cooled for the fifth time, it returns and undergoes the first CO 2 absorption.

[0101] In the present invention, as Figure 1 shown, preferably, a third pump P-3 is provided on the pipeline connecting the semi-lean liquid methanol outlet of the reabsorption tower T-5 and the second CO 2 absorption section, for returning the first stream of semi-lean liquid methanol 8-i after being pressurized for the third time and undergoing the second CO 2 absorption.

[0102] In the present invention, as Figure 1 shown, preferably, a fourth pump P-4 is provided on the pipeline connecting the low-H 2 S methanol outlet of the reabsorption tower T-5 and the secondary H 2 S flash evaporation section, for returning the low-H 2 S methanol after being pressurized for the fourth time and undergoing the second washing.

[0103] The present invention will be described in detail below through embodiments.

[0104] The syngas purification device for a coal water slurry gasification device, as Figure 1 shown, from Figure 1 it can be seen that this device includes: H 2 S absorption tower T-1, CO 2 absorption tower T-2, primary flash evaporation tower T-3, secondary flash evaporation tower T-4 and reabsorption tower T-5, first cooler E-1, second cooler E-2, third cooler E-3, fourth cooler E-4 and fifth cooler E-5, and first pump P-1, second pump P-2, third pump P-3 and fourth pump P-4;

[0105] H 2 S absorption tower T-1 includes a first H 2 S absorption section provided at the lower part and a second H 2 S absorption section provided at the upper part; CO 2 absorption tower T-2 includes a first CO 2 absorption section provided at the lower part and a second CO 2 absorption section provided at the upper part; primary flash evaporation tower T-3 includes a primary CO 2 flash evaporation section provided at the upper part and a primary H 2 S flash evaporation section provided at the lower part; secondary flash evaporation tower T-4 includes a secondary CO 2 flash evaporation section provided at the upper part and a secondary H 2 S flash evaporation section provided at the lower part.

[0106] The syngas purification method for a coal water slurry gasification device, this method includes:

[0107] The syngas 1 (H 2 with a molar content of H₂S being 0.9 - 1.2%, and a molar content of CO 2 being 40 - 50%; at a temperature of -15 to -5 °C and a pressure of 5.2 - 5.7 MPa(G)) is in countercurrent contact with the first stream of H₂S - containing methanol 2 - i at a molar flow rate ratio of 70 - 80:1 and undergoes the first H₂S absorption to obtain the second H₂S - rich methanol 3 (H₂S 2 with a molar content of H₂S being 2.5 - 3.5%, and a molar content of CO 2 being 70 - 75%) and the pre - washed syngas; 2 The above - mentioned pre - washed syngas is successively in countercurrent contact with the second stream of H₂S - containing methanol 2 - ii and the first CO - rich methanol 4 - i and undergoes the second H₂S absorption to obtain the desulfurized gas 6 (H₂S 2 with a molar content of H₂S being 0.5 - 1 ppm, and a molar content of CO 2 being 36 - 40%; at a temperature of -20 to -10 °C; at a pressure of 5.3 - 5.4 MPa(G)) and the first H₂S - rich methanol 5 (H₂S

[0108] wherein, the H₂S - containing methanol 2 is first pressurized to 5.8 - 6 MPa(G) and then divided into the first stream of H₂S - containing methanol 2 - i and the second stream of H₂S - containing methanol 2 - ii at a molar flow rate ratio of 1:11 - 13; the molar flow rate ratio of the syngas 1 and the second stream of H₂S - containing methanol 2 - ii is 5 - 7:1; the molar flow rate ratio of the syngas 1 and the first CO - rich methanol 4 - i is 2 - 3:1; 2 The above - mentioned desulfurized gas 6 and the CO - containing methanol 7 (cooled to -36 to -33 °C in the fifth cooling) are in countercurrent contact at a molar flow rate ratio of 1:1.2 - 1.5 and undergo the first CO 2 absorption to obtain the CO - rich methanol 4 (CO 2 with a molar content of CO being 30 - 36%, H₂ 2 with a molar content of H₂S being 1.5 - 2%, and a molar content of CO 2 being 40 - 45%; at a temperature of -20 to -10 °C, at a pressure of 5.3 - 5.4 MPa(G)); 2 The above - mentioned desulfurized gas 6 and the CO - containing methanol 7 (cooled to -36 to -33 °C in the fifth cooling) are in countercurrent contact at a molar flow rate ratio of 1:1.2 - 1.5 and undergo the first CO 2 absorption to obtain the CO - rich methanol 4 (CO 2 with a molar content of CO being 30 - 36%, H₂

[0109] wherein, the H₂S - containing methanol 2 is first pressurized to 5.8 - 6 MPa(G) and then divided into the first stream of H₂S - containing methanol 2 - i and the second stream of H₂S - containing methanol 2 - ii at a molar flow rate ratio of 1:11 - 13; the molar flow rate ratio of the syngas 1 and the second stream of H₂S - containing methanol 2 - ii is 5 - 7:1; the molar flow rate ratio of the syngas 1 and the first CO - rich methanol 4 - i is 2 - 3:1; 2 The above - mentioned desulfurized gas 6 and the CO - containing methanol 7 (cooled to -36 to -33 °C in the fifth cooling) are in countercurrent contact at a molar flow rate ratio of 1:1.2 - 1.5 and undergo the first CO 2 absorption to obtain the CO - rich methanol 4 (CO 2 with a molar content of CO being 30 - 36%, H₂ 2 with a molar content of H₂S being 1.5 - 2%, and a molar content of CO 2 being 40 - 45%; at a temperature of -20 to -10 °C, at a pressure of 5.3 - 5.4 MPa(G));

[0110] The above - mentioned desulfurized gas 6 and the CO - containing methanol 7 (cooled to -36 to -33 °C in the fifth cooling) are in countercurrent contact at a molar flow rate ratio of 1:1.2 - 1.5 and undergo the first CO 2 absorption to obtain the CO - rich methanol 4 (CO 2 with a molar content of CO being 30 - 36%, H₂ 2 with a molar content of CO being 30 - 36%, H₂ 2 with a molar content of CO being 30 - 36%, H₂ 2The molar content of S is 0.1 - 0.5 ppm; the temperature is -15 to -10 °C, the pressure is 5.3 - 5.4 MPa(G)) and the pre-purified gas, where the rich CO 2 Methanol 4 is divided into a first rich CO with a molar flow ratio of 1:2 - 2.4 2 Methanol 4-i and a second rich CO 2 Methanol 4-ii; the first rich CO 2 Methanol 4-i is secondarily pressurized to 5.8 - 6 MPa(G), fourth cooled to -36 to -33 °C, and sent to the second H 2 S absorption section;

[0111] The above-mentioned pre-purified gas is successively countercurrently contacted with the first semi-lean methanol 8-i (pressurized to 5.8 - 6 MPa(G) by the third stage), lean methanol 9 (CO 2 The molar content is 0%, H 2 The molar content of S is 0%) and second CO 2 absorption is carried out to obtain purified gas 19 (H 2 The molar content of S < 0.1 ppm, CO 2 The molar content < 20 ppm; the temperature is -55 to -50 °C; the pressure is 5.2 - 5.3 MPa(G));

[0112] Among them, the molar flow ratio of the above-mentioned purified gas 19 to the first semi-lean methanol 8-i is 1.5 - 1.7:1; the molar flow ratio of the above-mentioned purified gas 19 to lean methanol 9 is 1:1.4 - 1.6;

[0113] The above-mentioned second rich CO 2 Methanol 4-ii is first cooled to -36 to -33 °C and then undergoes primary CO 2 flashing (pressure is 3.5 - 3.7 MPa(G)) to obtain rich CO after primary flashing 2 Methanol 10 (H 2 The molar content of S is 0.1 - 0.5 ppm, CO 2 The molar content is 29.5 - 35.5%; the temperature is -36.5 to -33.5 °C) and primary CO 2 flash gas 11-i; the first rich H 2 S methanol 5 is third cooled to -33 to -30 °C and then undergoes primary H 2 S flashing (pressure is 3.5 - 3.7 MPa(G)) to obtain rich H 2 S methanol 14 (H 2 The molar content of S is 1.5 - 2.0%, CO 2 The molar content is 39.5 - 43.5%; the temperature is -33.5 to -30.5 °C) and primary H 2S flash vapor 11-ii; the above-mentioned primary CO 2 flash vapor 11-i and primary H 2 S flash vapor 11-ii are mixed to obtain the H in the primary flash vapor 11 2 The molar content of S is 0.1 - 0.2%; CO 2 The molar content of is 23 - 28%; H 2 The molar content of is 68 - 75%; the temperature is -40 to -30 °C, and the pressure is 3.5 - 3.7 MPa(G).

[0114] The CO-rich methanol 10 after the above-mentioned primary flash evaporation is subjected to secondary CO 2 flash evaporation (pressure is 1.6 - 2 MPa(G)) to obtain the CO-rich methanol 12 after flash evaporation 2 (the molar content of H 2 S is 0.1 - 0.5 ppm, the molar content of CO 2 is 29 - 35%; the temperature is -40 to -30 °C) and the secondary CO 2 flash vapor; the H-rich methanol 14 after the above-mentioned primary flash evaporation is subjected to secondary H 2 S flash evaporation (pressure is 1.6 - 2 MPa(G)) to obtain the H-rich methanol 16 after flash evaporation 2 (the molar content of H 2 S is 1.5 - 2%, the molar content of CO 2 is 38 - 42%; the temperature is -35 to -30 °C) and the secondary H 2 S flash vapor; 2 2 2 The CO-rich methanol 12 after the above-mentioned flash evaporation is divided into a first stream of CO-rich methanol 12-i and a second stream of CO-rich methanol 12-ii with a molar flow rate ratio of 3.5 - 4:1. Among them, the first stream of CO-rich methanol 12-i is subjected to a first flash evaporation (pressure is 0.05 - 0.08 MPa(G)) to obtain the first CO

[0115] product gas and semi-lean methanol 8 (the molar content of CO 2 is 22 - 25%, the molar content of H 2 S is ≤0.5 ppm; the temperature is -66 to -63 °C; the pressure is 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 rate ratio of 1.2 - 1.5:1; the second stream of CO-rich methanol 12 after flash evaporation 2 2 2 2 2 2 2 2 2 2 2After methanol 12-ii is secondarily cooled to -55 to -50 °C, secondary flash evaporation is carried out (pressure is 0.06 - 0.09 MPa(G)) to obtain secondary CO 2 product gas and the solution after flash evaporation; the rich H 2 S methanol 16 after the above flash evaporation is subjected to tertiary flash evaporation (pressure is 0.12 - 0.16 MPa(G)) to obtain H 2 S gas phase and tertiary rich H 2 S methanol 17 (the molar content of H 2 S is 1.5 - 2%, and the molar content of CO 2 is 25 - 35%; the temperature is -69 to -65 °C; the pressure is 0.13 - 0.17 MPa(G)); the above H 2 S gas phase and the solution after flash evaporation are subjected to primary washing to obtain tertiary CO 2 product gas and low H 2 S methanol 20 (the molar content of H 2 S is 0.9 - 1.1%, and the molar content of CO 2 is 25 - 28%; the temperature is -65 to -60 °C, and the pressure is 0.12 - 0.16 MPa(G));

[0116] Among them, the above low H 2 S methanol 20 is pressurized to 2 - 2.4 MPa(G) for the fourth time and then subjected to secondary washing with secondary CO 2 flash gas and secondary H 2 S flash gas to obtain H 2 S methanol 2 (the molar content of H 2 S is 0.9 - 1.1%, and the molar content of CO 2 is 28 - 32%; the temperature is -65 to -60 °C) and secondary flash gas 15 (the temperature is -65 °C to -60 °C, and the pressure is 1.6 - 2 MPa(G));

[0117] Among them, the above primary CO 2 product gas, secondary CO 2 product gas and tertiary CO 2 product gas are mixed to obtain CO 2 product gas 18 (the molar content of H 2 S < 1 ppm, and the molar content of CO 2 is 99.4 - 99.7%; the temperature is -68 °C to -63 °C, and the pressure is 0.05 - 0.08 MPa(G)).

[0118] Comparative Example 1

[0119] Taking a hydrogen production device using coal water slurry gasification for gas production as an example, the effective gas (H 2+CO) is 230,000 Nm 3 / h. Based on this benchmark, the main technical parameters of the lean-rich solution process (i.e., CN201110260570.0 discloses a low-temperature methanol washing process) are compared as shown in Table 1.

[0120] Table 1

[0121] Comparative Example 1 Example 1 Lean methanol recycle flow rate 13500 kmol / h 12500 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 9500 kmol / h 8500 kmol / h External cooling consumption 8500 KW / h 7900 KW / h <![CDATA[H 2 Methanol for washing in the S absorption tower <![CDATA[Rich in CO 2 methanol]]> <![CDATA[Rich in CO 2 methanol, containing H 2 S methanol]]> Washing medium for the secondary medium-pressure flash column <![CDATA[Rich in H 2 S methanol]]> <![CDATA[Low H 2 S methanol]]>

[0122] From the results in Table 1, taking the hydrogen production device based on coal water slurry gasification as an example, for the syngas purification process of the supporting coal water slurry gasification device provided in Example 1, the lean methanol circulation rate is 92.6% of the lean methanol circulation rate in Comparative Example 1 (lean-rich solution process), and the H 2 The amount of rich CO in the S absorption tower 2 The methanol consumption is 89.5% of the rich CO 2 The methanol consumption in Comparative Example 1 (lean-rich solution process), and the cumulative reduction of external cold energy consumption is 600 KW / h, with a significant overall energy-saving effect.

[0123] 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 water-coal slurry gasification device, characterized in that: The purification method comprises: subjecting the synthesis gas to H2S absorption to obtain first H2S-rich methanol and desulfurized gas; subjecting the desulfurized gas to CO2 absorption to obtain CO2-rich methanol, which is divided into two streams; subjecting the second stream of CO2-rich methanol to first cooling and then sequentially subjecting the second stream of CO2-rich methanol to first CO2 flash evaporation and second CO2 flash evaporation, and subjecting the obtained flashed CO2-rich methanol to two streams, subjecting the first stream of flashed CO2-rich methanol to first flash evaporation to obtain semi-lean liquid methanol; subjecting the second stream of flashed CO2-rich methanol to second cooling and then subjecting the second stream of flashed CO2-rich methanol to second flash evaporation; The first H2S-rich methanol is subjected to a first H2S flash evaporation and a second H2S flash evaporation in sequence after the third cooling, the obtained flashed H2S-rich methanol is subjected to a third flash evaporation, and the obtained H2S-containing gas phase and the flashed solution obtained by the second flash evaporation are subjected to a first washing to obtain low-H2S methanol; The secondary CO2 flash gas obtained by the secondary CO2 flash evaporation and the secondary H2S flash gas obtained by the secondary H2S flash evaporation are mixed and then subjected to a second washing with the low-H2S methanol, and the obtained H2S-containing methanol is returned and subjected to the H2S absorption.

2. The purification method according to claim 1, wherein: Returning the first stream of CO2-rich methanol and performing the H2S absorption; and / or, the H2S-containing methanol is first pressurized to 5.8-6 MPa(G) and then returned to perform the H2S absorption; And / or, the semi-lean methanol is divided into two streams, and the first stream of semi-lean methanol is returned to perform the CO2 absorption.

3. The purification method according to claim 1 or 2, wherein: The H2S absorption process comprises: contacting the synthesis gas with a first stream of H2S-containing methanol and performing a first H2S absorption to obtain a pre-washed synthesis gas and a second H2S-rich methanol; contacting the pre-washed synthesis gas, the second stream of H2S-containing methanol and the first stream of CO2-rich methanol and performing a second H2S absorption to obtain the first H2S-rich methanol and desulfurized gas; and / or, dividing the H2S-containing methanol into the first stream of H2S-containing methanol and the second stream of H2S-containing methanol at a molar flow ratio of 1:11-13; and / or, the molar content of H2S in the synthesis gas is 0.9-1.2%, the molar content of CO2 is 40-50%; the temperature is -15 to -5°C, and the pressure is 5.2-5.7MPa(G); and / or, the molar content of H2S in the first H2S-rich methanol is 1.5-2%, the molar content of CO2 is 40-45%; the temperature is -20 to -10°C, and the pressure is 5.3-5.4MPa(G); And / or, the molar content of H2S in the desulfurized gas is 0.5-1 ppm, the molar content of CO2 is 36-40%; the temperature is -20 to -10°C; and the pressure is 5.3-5.4 MPa(G).

4. The purification method according to any one of claims 1 to 3, wherein: The CO2 absorption process includes: contacting the desulfurized gas with CO2-containing methanol and performing a first CO2 absorption to obtain pre-purified gas and CO2-rich methanol; contacting the pre-purified gas, the first stream of semi-lean liquid methanol and lean methanol and performing a second CO2 absorption to obtain purified gas and the CO2-containing methanol; and / or, the molar content of CO2 in the CO2-rich methanol is 30-36%, the molar content of H2S is 0.1-0.5 ppm; the temperature is -15 to -10°C, and the pressure is 5.3-5.4 MPa(G); and / or, the molar flow ratio of the first stream of CO2-rich methanol to the second stream of CO2-rich methanol is 1:2-2.4; and / or, according to the material flow direction, the first stream of CO2-rich methanol is successively pressurized to 5.8-6 MPa(G) and cooled to -36 to -33°C in sequence, and then returned to perform the H2S absorption; and / or, the CO2-containing methanol is cooled to -36 to -33°C for the fifth time and then returned to the first CO2 absorption process; and / or, the molar flow ratio of the purified gas to the first stream of semi-lean methanol is 1.5-1.7:1; and / or, the molar flow ratio of the purified gas to lean methanol is 1:1-1.2; 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 5.2-5.3 MPa(G).

5. The method according to any one of claims 1 to 4, wherein: The pressure of the first-stage CO2 flash evaporation is greater than the pressure of the second-stage CO2 flash evaporation; the pressure of the first-stage H2S flash evaporation is greater than the pressure of the second-stage H2S flash evaporation; And / or, the temperature of the first cooled material is -36 to -33°C; And / or, the process of the primary CO2 flash evaporation comprises: subjecting the first cooled material to the primary CO2 flash evaporation to obtain primary flash evaporation CO2-rich methanol; And / or, the temperature of the material after the third cooling is -33 to -30°C; And / or, the process of the primary H2S flash evaporation comprises: subjecting the third cooled material to the primary H2S flash evaporation to obtain primary flash evaporation-rich H2S methanol; And / or, the pressure of the first-stage CO2 flash and the first-stage H2S flash is independently 3.5-3.7 MPa(G); and / or, the molar content of H2S in the CO2-rich methanol after the first-stage flash is 0.1-0.5 ppm, the molar content of CO2 is 29.5-35.5%; the temperature is -36.5 to -33.5°C; and / or, the molar content of H2S in the H2S-rich methanol after the first-stage flash is 1.5-2%, and the molar content of CO2 is 39.5-43.5%; the temperature is -33.5 to -30.5°C; And / or, the first-stage flash steam includes the first-stage CO2 flash steam obtained by the first-stage CO2 flash and the first-stage H2S flash steam obtained by the first-stage H2S flash; the molar content of H2S in the first-stage flash steam is 0.1-0.2%; the molar content of CO2 is 23-28%; the molar content of H2 is 68-75%; the temperature is -40 to -30°C, and the pressure is 3.5-3.7MPa(G).

6. The purification method according to claim 5, wherein: The process of the secondary CO2 flash evaporation comprises: subjecting the CO2-rich methanol after the primary flash evaporation to the secondary CO2 flash evaporation to obtain the CO2-rich methanol after the flash evaporation and the secondary CO2 flash gas; And / or, the process of the secondary H2S flash evaporation comprises: subjecting the H2S-rich methanol after the primary flash evaporation to the secondary H2S flash evaporation to obtain the H2S-rich methanol after the flash evaporation and the secondary H2S flash gas; and / or, the pressures of the secondary CO2 flash and the secondary H2S flash are each independently selected from 1.6-2 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 29-35%; the temperature is -40 to -30°C; and / or, the molar content of H2S in the H2S-rich methanol after the flash evaporation is 1.5-2%, and the molar content of CO2 is 38-42%; the temperature is -35 to -30°C; and / or, the molar content of H2S in the H2S-containing methanol is 0.9-1.1%, the molar content of CO2 is 28-32%; the temperature is -65 to -60°C; And / or, the temperature of the secondary flash gas obtained by the second washing is -65°C to -60°C, and the pressure is 1.6-2 MPa(G).

7. The purification method according to any one of claims 1 to 6, wherein: The molar flow ratio of the first flash CO2-rich methanol to the second flash 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 22-25%, the molar content of H2S is ≤0.5ppm; the temperature is -66 to -63°C; the pressure is 0.05-0.08MPa(G); and / or, dividing the semi-lean methanol into a first stream of semi-lean methanol and a second stream of semi-lean methanol at a molar flow ratio of 1.2-1.5:1; and / or, the first stream of semi-lean methanol is pressurized to 5.8-6 MPa(G) for the third time and then returned to perform the CO2 absorption; 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 molar content of H2S in the low H2S methanol is 0.9-1.1%, the molar content of CO2 is 25-28%; the temperature is -65 to -60°C, and the pressure is 0.12-0.16MPa(G); and / or, the low H2S methanol is pressurized to 2-2.4 MPa(G) for the fourth time and then subjected to the second washing; And / or, the pressure of the third flash evaporation is 0.12-0.16 MPa(G); And / or, the third H2S-rich methanol obtained by the third flash evaporation has a molar content of H2S of 1.5-2%, a molar content of CO2 of 25-35%, a temperature of -69 to -65°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 first washing are mixed to obtain CO2 product gas, wherein the molar content of H2S in the CO2 product gas is less than 1ppm, and the molar content of CO2 is 99.4-99.7%; the temperature is -68°C to -63°C, and the pressure is 0.05-0.08MPa(G).

8. A synthesis gas purification device supporting a water-coal slurry gasification device, characterized in that: The purification device comprises: an H2S absorption tower, a CO2 absorption tower, a primary flash tower, a secondary flash tower and a reabsorption tower connected in sequence, as well as a first cooler, a second cooler and a third cooler; the primary flash tower comprises a primary CO2 flash section arranged on the top and a primary H2S flash section arranged on the bottom; the secondary flash tower comprises a secondary CO2 flash section arranged on the top and a secondary H2S flash section arranged on the bottom; The synthesis gas enters the H2S absorption tower to obtain the first H2S-rich methanol and the desulfurized gas; the desulfurized gas enters the CO2 absorption tower, and the obtained CO2-rich methanol is divided into two streams. The second stream of CO2-rich methanol passes through the first cooler and then enters the primary CO2 flash section and the secondary CO2 flash section in sequence. The obtained flashed CO2-rich methanol is divided into two streams. The first stream of flashed CO2-rich methanol enters the upper part of the reabsorption tower for the first flash to obtain semi-lean liquid methanol; the second stream of flashed CO2-rich methanol passes through the second cooler and then enters the middle part of the reabsorption tower for the second flash. The first H2S-rich methanol passes through the third cooler and then enters the primary H2S flash section and the secondary H2S flash section in sequence. The flashed H2S-rich methanol obtained enters the lower part of the reabsorption tower for the third flash. The H2S-containing gas phase obtained is first washed with the flashed solution obtained by the second flash. The low-H2S methanol obtained enters the secondary H2S flash section and is secondly washed with the secondary CO2 flash gas obtained by the secondary CO2 flash and the secondary H2S flash gas obtained by the secondary H2S flash. The H2S-containing methanol is recycled back to the H2S absorption tower.

9. The purification device according to claim 8, wherein: The H2S absorption tower is divided into a first H2S absorption section and a second H2S absorption section from bottom to top; And / or, the CO2 absorption tower is divided into a first CO2 absorption section and a second CO2 absorption section from bottom to top; Preferably, the H2S-containing methanol outlet of the secondary flash tower is connected to the first H2S absorption section and the second H2S absorption section respectively; Preferably, the CO2-rich methanol outlet of the CO2 absorption tower is connected to the second H2S absorption section; Preferably, in the CO2 absorption tower, the bottom of the second CO2 absorption section is connected to the upper part of the first CO2 absorption section; Preferably, the semi-lean liquid methanol outlet of the reabsorption tower is connected to the second CO2 absorption section.

10. The purification device according to claim 9, wherein: A first pump is provided on the pipeline connecting the H2S-containing methanol outlet of the secondary flash tower and the H2S absorption tower, for dividing the H2S-containing methanol into two streams after the first pressurization, and circulating them back to the first H2S absorption section and the second H2S absorption section respectively; 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 second H2S absorption section; and / or, a fifth cooler is provided on the pipeline connecting the second CO2 absorption section and the first CO2 absorption section according to the material flow direction; and / or, a third pump is provided on the pipeline connecting the semi-lean liquid methanol outlet of the reabsorption tower and the second CO2 absorption section; And / or, a fourth pump is provided on the pipeline connecting the low H2S methanol outlet of the reabsorption tower and the secondary H2S flash section.

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