Energy-saving poly-generation synthesis gas purification technology matched with pulverized coal gasification device

Abstract

The invention relates to the technical field of low-temperature methanol washing, in particular to an energy-saving poly-generation synthesis gas purification method matched with a pulverized coal gasification device and an energy-saving poly-generation synthesis gas purification device matched with the pulverized coal gasification device. According to the method, a flash evaporation process is optimally configured, and CO2 flash steam and H2S flash steam are washed by using non-transformation H2S-rich methanol, so that secondary absorption of the flash steam is realized; the CO2 absorption process is optimized, non-conversion CO2-rich methanol, low-carbon methanol and lean methanol are used for treating desulfurized gas, the use amount of lean methanol is reduced, and the method has the advantage of being low in comprehensive energy consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-temperature methanol washing, in particular to an energy-saving multi-production synthetic gas purification method matched with a pulverized coal gasification device and an energy-saving multi-production synthetic gas purification device matched with a pulverized coal gasification device. BACKGROUND

[0002] The low-temperature methanol washing technology is to absorb and remove H2S and CO2 and other acid gases in the synthetic gas by using low-temperature methanol as the absorption solvent, and to remove HCN, NH3 and other trace components. At present, the low-temperature methanol washing technology innovation research at home and abroad mainly focuses on the pressure-reducing flash circulation use of CO2-rich methanol, mainly including lean liquid-semi-lean liquid process, but the current innovation optimization of CO2-rich methanol has reached the limit.

[0003] With the diversification of gas component requirements of downstream processes, the multi-production low-temperature methanol washing technology has also developed rapidly. In the multi-production low-temperature methanol process, the non-shift CO2-rich methanol solution has the characteristics of not containing H2S gas and low CO2 content, and how to reasonably use the non-shift CO2-rich methanol for the second time is the key consideration in the design of the multi-production low-temperature methanol washing process. In addition, the non-shift H2S-rich methanol also has utilization value, which also needs to be fully considered in the process design.

[0004] CN201810994082.4 discloses a low-temperature methanol washing system and a synthetic gas providing method. The technology utilizes the non-shift H2S-rich methanol after the non-shift gas washing, but only uses it as the flash gas washing methanol after the medium-pressure flash of the H2S-rich methanol, which is not efficient enough, and there is still room for improvement and energy consumption reduction.

[0005] CN201110260570.0 discloses a low-temperature methanol washing process. First, the process uses CO2-rich methanol to wash the synthetic gas in the H2S absorption tower, which increases the generation of H2S-rich methanol, and the H2S-rich methanol can only be recycled after heat regeneration, which is high in energy consumption. Second, in the CO2 flash section of the reabsorption tower, the CO2-rich methanol is washed with the H2S-rich methanol flash gas at the same time, and is contaminated by the H2S-rich methanol, and the low-concentration H2S methanol produced is not fully used. Third, the medium-pressure flash process is not reasonable, and the H2S-rich methanol directly mixes with the washed liquid, which is not conducive to the low temperature in the reabsorption tower. SUMMARY

[0006] The present application aims to overcome the problems of unreasonable process setting of pressure flash tower and resorption tower, unreasonable use of carbon-rich methanol after washing and absorbing non-shift gas, etc. in the prior art poly-generation low-temperature methanol washing technology, and provides an energy-saving poly-generation syngas purification method matched with a pulverized coal gasification device and an energy-saving poly-generation syngas purification device matched with a pulverized coal gasification device. The method realizes secondary absorption of flash gas by optimizing the configuration of flash process and using non-shift H2S-rich methanol to wash CO2 flash gas and H2S flash gas, and reduces the use amount of lean methanol by optimizing the setting of CO2 absorption process and using non-shift CO2-rich methanol, low-carbon methanol and lean methanol to treat desulfurized gas, and has the characteristics of low comprehensive energy consumption.

[0007] To achieve the above-mentioned purpose, the present application provides, in a first aspect, an energy-saving poly-generation syngas purification method matched with a pulverized coal gasification device, which comprises:

[0008] The syngas from the pulverized coal gasification device is sequentially subjected to primary H2S absorption, secondary H2S absorption, primary CO2 absorption and secondary CO2 absorption to obtain primary H2S-rich methanol, secondary H2S-rich methanol, two streams of primary CO2-rich methanol, secondary CO2-rich methanol and purified gas; wherein the second stream of primary CO2-rich methanol and the secondary H2S-rich methanol are subjected to CO2 flashing and H2S flashing, respectively, to obtain CO2 flashing liquid, H2S flashing liquid, CO2 flashing gas and H2S flashing gas;

[0009] The CO2 flashing liquid is divided into two streams after heat exchange, the first stream of CO2 flashing liquid, the second stream of CO2 flashing liquid and the H2S flashing liquid are subjected to first flashing, second flashing and third flashing, respectively, to obtain two streams of semi-lean liquid methanol, low-sulfur methanol and first H2S-rich methanol; wherein the first stream of semi-lean liquid methanol is subjected to stripping after the heat exchange, and the obtained low-carbon methanol is returned to the secondary CO2 absorption;

[0010] The non-shift H2S-rich methanol from the non-shift gas purification process is divided into three streams, the first stream of non-shift H2S-rich methanol and the second stream of non-shift H2S-rich methanol are returned to the primary H2S absorption and the non-shift gas purification process, respectively, and the third stream of non-shift H2S-rich methanol is subjected to first washing with the CO2 flashing gas and the H2S flashing gas; the non-shift CO2-rich methanol from the non-shift gas purification process is divided into a stream of non-shift CO2-rich methanol, b stream of non-shift CO2-rich methanol and the second stream of non-shift CO2-rich methanol, which are returned to the secondary H2S absorption, the secondary CO2 absorption and the non-shift gas purification process, respectively; wherein the first stream of primary CO2-rich methanol and the low-sulfur methanol are returned to the secondary H2S absorption, respectively.

[0011] The second aspect of the present application provides an energy-saving multi-production synthetic gas purification device matched with a pulverized coal gasification device, the device comprising: connected non-shift gas purification tower, H2S absorption tower, CO2 absorption tower, medium-pressure flash tower, reabsorption tower and low-carbon methanol stripping tower;

[0012] The H2S absorption tower is used for sequentially performing primary H2S absorption and secondary H2S absorption on the synthetic gas from the pulverized coal gasification device to obtain primary H2S-rich methanol, secondary H2S-rich methanol and desulfurized gas; the CO2 absorption tower is used for sequentially performing primary CO2 absorption and secondary CO2 absorption on the desulfurized gas to obtain two primary CO2-rich methanol, secondary CO2-rich methanol and purified gas;

[0013] The medium-pressure flash tower is divided into CO2 flash section, washing section and H2S flash section from top to bottom, the CO2 flash section is used for performing CO2 flash on the second primary CO2-rich methanol to obtain CO2 flash gas which is sent to the washing section through a pipeline, and CO2 flash liquid which is divided into two streams after a heat exchanger; the H2S flash section is used for performing H2S flash on the secondary H2S-rich methanol to obtain H2S flash gas which is sent to the washing section through a riser, and H2S flash liquid;

[0014] The reabsorption tower is divided into first flash section, second flash section and third flash section from top to bottom, and is respectively used for performing first flash, second flash and third flash on the first CO2 flash liquid, the second CO2 flash liquid and the H2S flash liquid to obtain two semi-lean liquid methanols, low-sulfur methanol and first H2S-rich methanol;

[0015] The first semi-lean liquid methanol is sent to the low-carbon methanol stripping tower for stripping after the heat exchanger, and the obtained low-carbon methanol is returned to the CO2 absorption tower;

[0016] The non-shift H2S-rich methanol from the non-shift gas purification tower is divided into three streams, the first non-shift H2S-rich methanol and the second non-shift H2S-rich methanol are respectively returned to the H2S absorption tower and the non-shift gas purification tower, and the third non-shift H2S-rich methanol is sent to the washing section to perform first washing with the CO2 flash gas and the H2S flash gas; the non-shift CO2-rich methanol from the non-shift gas purification tower is divided into a non-shift CO2-rich methanol, b non-shift CO2-rich methanol and second non-shift CO2-rich methanol which are respectively returned to the H2S absorption tower, the CO2 absorption tower and the non-shift gas purification tower; the first primary CO2-rich methanol and the low-sulfur methanol are respectively returned to the H2S absorption tower.

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

[0018] (1) The method provided by the application realizes secondary absorption of the flash gas by optimizing the medium-pressure flash process and using non-shift H2S-rich methanol to wash the CO2 flash gas and H2S flash gas, and the washing liquid is not mixed with the washed liquid; compared with the prior art, the method avoids the decrease of the H2S-rich methanol concentration after flashing, can produce lower temperature in the desorption of the reabsorption tower, and is beneficial to the reduction of the energy consumption of the device;

[0019] (2) The method provided by the application optimizes the reabsorption process, realizes the absorption of the sulfur-containing gas phase (for example, H2S) generated by the H2S flash liquid by the flash liquid of the second CO2 flash liquid, and avoids the mutual mixing of the first H2S-rich methanol after the third flash;

[0020] (3) The method provided by the application optimizes the CO2 absorption process, fully utilizes the low carbon content in the non-shift CO2-rich methanol and low-carbon methanol, and performs CO2 absorption on the desulfurized gas, thereby reducing the use amount of the lean methanol and being beneficial to the reduction of the energy consumption of the device. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The application provides an energy-saving multi-production synthetic gas purification device matched with a pulverized coal gasification device.

[0022] BRIEF DESCRIPTION OF DRAWINGS

[0023] T-1, non-shift gas purification tower; T-2, H2S absorption tower; T-3, CO2 absorption tower; T-4, medium-pressure flash tower; T-5, reabsorption tower; T-6, low-carbon methanol stripping tower;

[0024] E-1, first cooler; E-2, second cooler; E-3, third cooler; E-4, fourth cooler; E-5, fifth cooler; E-6, sixth cooler; P-1, first pump; P-2, second pump; P-3, third pump; Q, heat exchanger;

[0025] 1. non-shifted gas; 2. non-shifted H2S-rich methanol; 2-i. first stream of non-shifted H2S-rich methanol; 2-ii. second stream of non-shifted H2S-rich methanol; 2-iii. third stream of non-shifted H2S-rich methanol; 3. lean methanol; 3-i. first stream of lean methanol; 3-ii. second stream of lean methanol; 4. pre-purified non-shifted H2S-rich methanol; 5. purified non-shifted gas; 6. synthesis gas; 7. primary H2S-rich methanol; 8. non-shifted CO2-rich methanol; 8-i. first stream of non-shifted CO2-rich methanol; 8-i-a. stream a of non-shifted CO2-rich methanol; 8-i-b. stream b of non-shifted CO2-rich methanol; 8-ii. second stream of non-shifted CO2-rich methanol; 9. primary CO2-rich methanol; 9-i. first stream of primary CO2-rich methanol; 9-ii. second stream of primary CO2-rich methanol; 10. secondary H2S-rich methanol; 11. sweetened gas; 12. secondary CO2-rich methanol; 13. semi-lean liquid methanol; 13-i. first stream of semi-lean liquid methanol; 13-ii. second stream of semi-lean liquid methanol; 14. purified gas; 15. CO2 flash gas; 16. second H2S-rich methanol; 17. CO2 flash liquid; 17-i. first stream of CO2 flash liquid; 17-ii. second stream of CO2 flash liquid; 18. post-wash flash gas; 19. H2S flash liquid; 20. low-sulfur methanol; 21. first H2S-rich methanol; 22. CO2 product gas; 23. nitrogen; 24. low-carbon methanol; 25. tail gas. DETAILED DESCRIPTION

[0026] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as implicitly split by the language of the specification. The described ranges should be construed as being encompassing both the specific values recited and values close thereto. For values which are less than one, one of ordinary skill in the art will appreciate that the value is intended to mean less than one unit, and that the specific value represents the exact point. For values which are greater than one, one of ordinary skill in the art will contemplate that the value is intended to mean greater than one unit, and that the specific value represents the exact point.

[0027] In the present application, unless otherwise specified, "first", "second", "third", "fourth", "fifth" and "sixth" do not indicate any precedence or sequence, nor do they limit the respective materials or steps, but are used only to distinguish or indicate that this is not the same step or material.

[0028] In the present application, unless otherwise specified, "top" of a vessel refers to 0-10% of the height of the vessel from top to bottom; "upper" of a vessel refers to 10-40% of the height of the vessel from top to bottom; "middle" of a vessel refers to 40-60% of the height of the vessel from top to bottom; "lower" of a vessel refers to 60-90% of the height of the vessel from top to bottom; and "bottom" of a vessel refers to 90-100% of the height of the vessel from top to bottom.

[0029] The first aspect of the present application provides an energy-saving multi-production synthetic gas purification method for a complete pulverized coal gasification device, the method comprising:

[0030] The synthetic gas from the pulverized coal gasification device is sequentially subjected to first H2S absorption, second H2S absorption, first CO2 absorption, and second CO2 absorption to obtain first H2S-rich methanol, second H2S-rich methanol, two streams of first CO2-rich methanol, second CO2-rich methanol, and purified gas; wherein the second stream of first CO2-rich methanol and the second H2S-rich methanol are subjected to CO2 flashing and H2S flashing, respectively, to obtain CO2 flashing liquid, H2S flashing liquid, CO2 flashing gas, and H2S flashing gas;

[0031] The CO2 flashing liquid is divided into two streams after heat exchange, and the first stream of CO2 flashing liquid, the second stream of CO2 flashing liquid, and the H2S flashing liquid are subjected to first flashing, second flashing, and third flashing, respectively, to obtain two streams of semi-lean liquid methanol, low-sulfur methanol, and first H2S-rich methanol; wherein the first stream of semi-lean liquid methanol is subjected to stripping after heat exchange, and the obtained low-carbon methanol is returned to the second CO2 absorption;

[0032] The non-shift H2S-rich methanol from the non-shift gas purification process is divided into three streams, the first stream of non-shift H2S-rich methanol and the second stream of non-shift H2S-rich methanol are returned to the first H2S absorption and the non-shift gas purification process, respectively, and the third stream of non-shift H2S-rich methanol is subjected to first washing with CO2 flashing gas and H2S flashing gas; the non-shift CO2-rich methanol from the non-shift gas purification process is divided into a stream of non-shift CO2-rich methanol, b stream of non-shift CO2-rich methanol, and second stream of non-shift CO2-rich methanol, which are returned to the second H2S absorption, the second CO2 absorption, and the non-shift gas purification process, respectively; wherein the first stream of first CO2-rich methanol and the low-sulfur methanol are returned to the second H2S absorption, respectively.

[0033] In the present application, unless otherwise specified, the synthetic gas and the non-shift gas are both derived from a pulverized coal gasification device.

[0034] In the present application, preferably, the molar content of H2S in the synthetic gas is 0.3-0.35%, the molar content of CO2 is 40-50%, the temperature is -25 to -15℃, and the pressure is 3.12-3.15 MPa(G); the molar content of H2S in the non-shift gas is 0.4-0.6%, the molar content of CO2 is 5-10%, the temperature is -35 to -25℃, and the pressure is 3.5-3.6 MPa(G).

[0035] In some embodiments of the present application, preferably, the non-shift gas purification process comprises: subjecting the non-shift gas to three-stage purification to obtain purified non-shift gas.

[0036] In some embodiments of the present application, preferably, the three-stage purification comprises: a first purification, a second purification and a third purification; wherein the non-shift gas and the second non-shift H2S-rich methanol are contacted and subjected to the first purification to obtain pre-purified non-shift H2S-rich methanol and pre-desulfurized non-shift gas; the pre-desulfurized non-shift gas and the second non-shift CO2-rich methanol are contacted and subjected to the second purification to obtain the non-shift H2S-rich methanol and desulfurized non-shift gas; and the desulfurized non-shift gas and the first methanol-lean stream are contacted and subjected to the third purification to obtain the non-shift CO2-rich methanol and purified non-shift gas.

[0037] In the present application, the first purification aims to remove HCN, NH3 and other impurities and a small amount of H2S and CO2 in the non-shift gas; the second purification aims to further remove H2S in the non-shift gas; and the third purification aims to further remove CO2 in the non-shift gas.

[0038] In the present application, preferably, the molar flow ratio of the non-shift gas and the second non-shift H2S-rich methanol is 1:115-125; further preferably, the molar content of H2S in the pre-purified non-shift H2S-rich methanol is 0.6-1.1%, the molar content of CO2 is 2-5%, the temperature is -35 to -25℃, and it is sent to the subsequent process.

[0039] In some embodiments of the present application, preferably, the molar content of H2S in the non-shift H2S-rich methanol is 0.5-0.9%, the molar content of CO2 is 3-7%, the temperature is -32 to -28℃, and the pressure is 3.5-3.55 MPa(G).

[0040] In the present application, the non-shift H2S-rich methanol is divided into three streams, the first stream is subjected to the first H2S absorption, the second stream is subjected to the first purification, and the third stream is subjected to the first washing. Further preferably, the molar flow ratio of the first non-shift H2S-rich methanol, the second non-shift H2S-rich methanol and the third non-shift H2S-rich methanol is 4-6:1:72-76.

[0041] In some embodiments of the present application, preferably, the molar content of H2S in the non-shift CO2-rich methanol is 0.5-1 ppm, the molar content of CO2 is 3-8%, and the temperature is -40 to -33℃.

[0042] In the present application, the non-shift CO2-rich methanol is divided into a first non-shift CO2-rich methanol and a second non-shift CO2-rich methanol, and the first non-shift CO2-rich methanol is divided into an a non-shift CO2-rich methanol and a b non-shift CO2-rich methanol.

[0043] In some embodiments of the present application, further preferably, the molar flow ratio of the a-th non-shifted CO2-rich methanol, the b-th non-shifted CO2-rich methanol and the second non-shifted CO2-rich methanol is 1:1:1-3.

[0044] In the present application, preferably, the molar flow ratio of the second non-shifted CO2-rich methanol and the non-shifted gas is 1:1-2; the molar flow ratio of the first methanol-lean and the non-shifted gas is 1.5-2.5:1-2.

[0045] In some embodiments of the present application, preferably, the molar content of H2S in the methanol-lean is 0%, the molar content of CO2 is 0%. In the present application, the methanol-lean is selected from subsequent processes. In the present application, without special circumstances, the methanol-lean is divided into the first methanol-lean and the second methanol-lean; the present application does not limit the molar flow ratio of the first methanol-lean and the second methanol-lean.

[0046] In the present application, preferably, the molar content of H2S in the purified non-shifted gas is ≤0.1 ppm, the molar content of CO2 is ≤20 ppm, the temperature is -55 to -45℃, and the pressure is 3.4-3.5 MPa(G).

[0047] In some embodiments of the present application, preferably, the synthesis gas and the first non-shifted H2S-rich methanol are contacted and the primary H2S absorption is carried out to obtain the primary H2S-rich methanol and the pre-desulfurization gas; the pre-desulfurization gas, the low-sulfur methanol, the first primary CO2-rich methanol and the a-th non-shifted CO2-rich methanol are contacted and the secondary H2S absorption is carried out to obtain the desulfurization gas and the secondary H2S-rich methanol.

[0048] In the present application, the primary H2S absorption aims to remove HCN, NH3 and other impurities in the synthesis gas, as well as a small amount of H2S and CO2; the secondary H2S absorption aims to further remove H2S and CO2 in the synthesis gas.

[0049] In the present application, preferably, the molar flow ratio of the synthesis gas and the first non-shifted H2S-rich methanol is 50-54:1; further preferably, the molar content of H2S in the primary H2S-rich methanol is 0.6-0.8%, the molar content of CO2 is 30-36%; the temperature is -25 to -15℃, and it is sent to subsequent processes for treatment.

[0050] In the present application, preferably, the molar flow ratio of the low-sulfur methanol and the synthesis gas is 1:3-5; the molar flow ratio of the first primary CO2-rich methanol and the synthesis gas is 2-4:5-8; the molar flow ratio of the a-th non-shifted CO2-rich methanol and the synthesis gas is 1:5-8.

[0051] In some embodiments of the present application, preferably, the mole content of H2S in the secondary H2S-rich methanol is 0.3-0.6%, the mole content of CO2 is 25-30%, and the temperature is -20 to -16℃.

[0052] In some embodiments of the present application, preferably, the mole content of H2S in the desulfurized gas is 0.5-1 ppm, the mole content of CO2 is 30-35%, the temperature is -25 to -15℃, and the pressure is 3.05-3.1 MPa (G).

[0053] In some embodiments of the present application, preferably, the desulfurized gas and the secondary CO2-rich methanol are contacted and subjected to the primary CO2 absorption to obtain the primary CO2-rich methanol and the pre-purified gas; the pre-purified gas, the low-carbon methanol, the b-share non-shift CO2-rich methanol and the second share lean methanol are contacted and subjected to the secondary CO2 absorption to obtain the secondary CO2-rich methanol and the purified gas.

[0054] In the present application, both the primary CO2 absorption and the secondary CO2 absorption are aimed at further removing CO2 in the desulfurized gas. Preferably, the mole flow ratio of the synthesis gas to the secondary CO2-rich methanol is 1:1-3; the mole flow ratio of the purified gas to the low-carbon methanol is 1-1.3:1, the mole flow ratio of the purified gas to the b-share non-shift CO2-rich methanol is 3-5:1; and the mole flow ratio of the purified gas to the second share lean methanol is 1:1-1.5.

[0055] In some embodiments of the present application, preferably, the mole content of H2S in the primary CO2-rich methanol is 0.1-0.5 ppm, the mole content of CO2 is 16-20%, the temperature is -22 to -18℃, and the pressure is 3.05-3.09 MPa (G).

[0056] In the present application, the primary CO2-rich methanol is divided into two shares, the first share is subjected to the secondary H2S absorption, and the second share is subjected to the CO2 flashing. Further preferably, the mole flow ratio of the first share of the primary CO2-rich methanol to the second share of the primary CO2-rich methanol is 1:2-4.

[0057] In some embodiments of the present application, preferably, the mole content of H2S in the purified gas is ≤0.1 ppm, the mole content of CO2 is ≤20 ppm, the temperature is -55 to -45℃, and the pressure is 3-3.05 MPa (G).

[0058] In the present application, the second share of the primary CO2-rich methanol is subjected to CO2 flashing to obtain CO2 flashing gas and CO2 flashing liquid; and the secondary H2S-rich methanol is subjected to H2S flashing to obtain H2S flashing gas and H2S flashing liquid.

[0059] In some embodiments of the present application, preferably, the pressure of the CO2 flash liquid and the H2S flash liquid is 0.8-1 MPa (G) respectively.

[0060] In some embodiments of the present application, preferably, the molar content of H2S in the CO2 flash liquid is 0.1-0.5 ppm, the molar content of CO2 is 15-19%, and the temperature is -25 to -21℃.

[0061] In some embodiments of the present application, preferably, the heat exchange process comprises: heat exchanging the CO2 flash liquid and the first semi-lean liquid methanol to obtain a heat-exchanged CO2 flash liquid with a temperature of -30 to -25℃ and a heat-exchanged semi-lean liquid methanol with a temperature of -45 to -42℃.

[0062] In the present application, unless otherwise specified, the heat exchange process is intended to regulate the temperature of the CO2 flash liquid and the first semi-lean liquid methanol, and the content of each component in the CO2 flash liquid and the first semi-lean liquid methanol does not change.

[0063] In the present application, the CO2 flash liquid is divided into two streams, which are subjected to first flash and second flash respectively. Preferably, the molar flow ratio of the first CO2 flash liquid to the second CO2 flash liquid is 3-5:1.

[0064] In some embodiments of the present application, preferably, the molar content of H2S in the H2S flash liquid is 0.25-0.55%, the molar content of CO2 is 24.5-29.5%, and the temperature is -40 to -34℃.

[0065] In some embodiments of the present application, preferably, the first CO2 flash liquid is subjected to the first flash to obtain the semi-lean liquid methanol and a first CO2 product gas; the second CO2 flash liquid is subjected to the second flash to obtain a flash liquid and a second CO2 product gas; and the H2S flash liquid is subjected to the third flash to obtain the first H2S-rich methanol and a sulfur-containing gas phase; wherein the flash liquid and the sulfur-containing gas phase are contacted and subjected to a second washing to obtain low-sulfur methanol and a third CO2 product gas; and wherein the first CO2 product gas, the second CO2 product gas, and the third CO2 product gas are mixed to obtain a CO2 product gas.

[0066] In some embodiments of the present application, preferably, the molar content of H2S in the semi-lean liquid methanol is 0.1-0.5 ppm; the molar content of CO2 is 10-14%, the temperature is -55 to -50℃, and the pressure is 0.05-0.08 MPa (G).

[0067] In the present application, the semi-lean liquid methanol is divided into two streams, the first stream is subjected to heat exchange and then subjected to the gas stripping, and the second stream is sent to the subsequent process. Further preferably, the molar flow ratio of the first stream of semi-lean liquid methanol and the second stream of semi-lean liquid methanol is 1-2:1.

[0068] In some embodiments of the present application, preferably, the molar content of H2S in the low-sulfur methanol is 0.1-0.3%, the molar content of CO2 is 14-18%, the temperature is -56 to -52℃, and the pressure is 0.12-0.16 MPa(G).

[0069] In some embodiments of the present application, preferably, the molar content of H2S in the CO2 product gas is ≤1 ppm, the molar content of CO2 is 99.4-99.7%, the temperature is -58 to -54℃, and the pressure is 0.05-0.08 MPa(G).

[0070] In some embodiments of the present application, preferably, the molar content of H2S in the first H2S-rich methanol is 0.2-0.5%, the molar content of CO2 is 15-20%, the temperature is -65 to -60℃, and the pressure is 0.13-0.17 MPa(G), which is sent to the subsequent process for treatment.

[0071] In some embodiments of the present application, preferably, the process of the gas stripping includes: after the first stream of semi-lean liquid methanol is subjected to heat exchange, the first stream of semi-lean liquid methanol is contacted with nitrogen and subjected to the gas stripping to obtain the low-carbon methanol and the tail gas.

[0072] In some embodiments of the present application, preferably, the molar content of H2S in the low-carbon methanol is 0.1-0.5 ppm, the molar content of CO2 is 3-7%, and the temperature is -56 to -52℃.

[0073] In some embodiments of the present application, preferably, the molar content of H2S in the tail gas is 0.1-0.5 ppm, the molar content of CO2 is 84-88%, the temperature is -50 to -40℃, and the pressure is 0.12-0.14 MPa(G), which is sent to the subsequent process.

[0074] In some embodiments of the present application, preferably, the process of the first washing includes: the third stream of non-shift H2S-rich methanol is respectively contacted with the CO2 flash gas and the H2S flash gas and subjected to the first washing to obtain the second H2S-rich methanol and the washed flash gas.

[0075] In some embodiments of the present application, further preferably, the molar content of H2S in the second H2S-rich methanol is 0.6-0.8%, the molar content of CO2 is 7-11%, and the temperature is -24 to -20℃, which is sent to the subsequent process.

[0076] In some embodiments of the present invention, further preferably, the molar content of H2S in the flashed gas after washing is 0.5 - 0.8%, the molar content of CO2 is 15 - 19%; the molar content of CO is 30 - 34%, the molar content of H2 is 48 - 52%, the temperature is -36 to -26 °C, and the pressure is 0.8 - 1 MPa(G).

[0077] In some embodiments of the present invention, preferably, after the low-sulfur methanol is pressurized to 3.6 - 4 MPa(G) for the first time, the secondary H2S absorption is carried out.

[0078] In some embodiments of the present invention, preferably, after the secondary H2S-rich methanol is cooled to -36 to -33 °C for the first time, the H2S flashing is carried out.

[0079] In some embodiments of the present invention, preferably, in the direction of material flow, the first stream of CO2-rich methanol in the first stage is pressurized to 3.6 - 4 MPa(G) for the second time and cooled to -46 to -43 °C for the second time, and then the secondary H2S absorption is carried out.

[0080] In some embodiments of the present invention, preferably, in the direction of material flow, after the secondary CO2-rich methanol is cooled to -36 to -33 °C for the third time, the primary CO2 absorption is carried out.

[0081] In some embodiments of the present invention, preferably, in the direction of material flow, the low-carbon methanol is pressurized to 3.6 - 4 MPa(G) for the third time, and the secondary CO2 absorption is carried out.

[0082] In some embodiments of the present invention, preferably, the a stream of non-shifted CO2-rich methanol and the b stream of non-shifted CO2-rich methanol are respectively cooled to -46 to -43 °C for the fourth time, and then the secondary H2S absorption and the secondary CO2 absorption are respectively carried out.

[0083] In some embodiments of the present invention, preferably, after the first stream of CO2 flashing liquid is cooled to -40 to -36 °C for the fifth time, the first flashing is carried out; preferably, after the second stream of CO2 flashing liquid is cooled to -52 to -48 °C for the sixth time, the second flashing is carried out.

[0084] The second aspect of the present invention provides a structural schematic diagram of an energy-saving polygeneration syngas purification device supporting a pulverized coal gasification device as Figure 1 shown, and it can be seen from Figure 1 that the device includes: a non-shifted gas purification tower T-1, a H2S absorption tower T-2, a CO2 absorption tower T-3, a medium-pressure flashing tower T-4, a reabsorption tower T-5, and a low-carbon methanol stripping tower T-6 which are connected;

[0085] The H2S absorption tower T-2 is used for sequentially performing primary H2S absorption and secondary H2S absorption on the synthesis gas 6 from the pulverized coal gasification device to obtain primary H2S-rich methanol 7, secondary H2S-rich methanol 10 and desulfurized gas 11; and the CO2 absorption tower T-3 is used for sequentially performing primary CO2 absorption and secondary CO2 absorption on the desulfurized gas 11 to obtain two portions of primary CO2-rich methanol 9, secondary CO2-rich methanol 12 and purified gas 14;

[0086] The medium-pressure flash tower T-4 is divided into a CO2 flash section, a washing section and an H2S flash section from top to bottom, the CO2 flash section is used for performing CO2 flash on the second portion of primary CO2-rich methanol 9-ii to obtain CO2 flash gas 15 which is sent to the washing section through a pipeline, and CO2 flash liquid 17 which is divided into two portions after passing through the heat exchanger Q; and the H2S flash section is used for performing H2S flash on the secondary H2S-rich methanol 10 to obtain H2S flash gas which is sent to the washing section through a gas lift hole, and H2S flash liquid 19;

[0087] The reabsorption tower T-5 is divided into a first flash section, a second flash section and a third flash section from top to bottom, and is respectively used for performing first flash, second flash and third flash on the first CO2 flash liquid 17-i, the second CO2 flash liquid 17-ii and the H2S flash liquid 19 to obtain two portions of semi-lean liquid methanol 13, low-sulfur methanol 20 and first H2S-rich methanol 21;

[0088] The first portion of semi-lean liquid methanol 13-i is sent to the low-carbon methanol stripping tower T-6 after passing through the heat exchanger Q to obtain low-carbon methanol 24 which is returned to the CO2 absorption tower T-3;

[0089] The non-shift H2S-rich methanol 2 from the non-shift gas purification tower T-1 is divided into three portions, the first portion of non-shift H2S-rich methanol 2-i and the second portion of non-shift H2S-rich methanol 2-ii are respectively returned to the H2S absorption tower T-2 and the non-shift gas purification tower T-1, and the third portion of non-shift H2S-rich methanol 2-iii is sent to the washing section to perform first washing with the CO2 flash gas 15 and the H2S flash gas; the non-shift CO2-rich methanol 8 from the non-shift gas purification tower T-1 is divided into a portion of non-shift CO2-rich methanol 8-i-a, a portion of non-shift CO2-rich methanol 8-i-b and a second portion of non-shift CO2-rich methanol 8-ii which are respectively returned to the H2S absorption tower T-2, the CO2 absorption tower T-3 and the non-shift gas purification tower T-1; the first portion of primary CO2-rich methanol 9-i and the low-sulfur methanol 20 are respectively returned to the H2S absorption tower T-2.

[0090] In the present application, as Figure 1As shown, the non-reformed gas purification tower T-1 is divided into a first purification section, a second purification section and a third purification section from bottom to top, which are communicated by riser holes.

[0091] In the present application, as shown in Figure 1 As shown, the H2S absorption tower T-2 is divided into a first H2S absorption section and a second H2S absorption section from bottom to top, which are communicated by riser holes.

[0092] In the present application, as shown in Figure 1 As shown, the CO2 absorption tower T-3 is divided into a first CO2 absorption section and a second CO2 absorption section from bottom to top, which are communicated by riser holes.

[0093] According to the present application, preferably, as shown in Figure 1 As shown, the first non-reformed H2S-rich methanol 2-i and the second non-reformed H2S-rich methanol 2-ii are returned to the first H2S absorption section and the first purification section, respectively.

[0094] According to the present application, preferably, as shown in Figure 1 As shown, the a non-reformed CO2-rich methanol 8-i-a, the b non-reformed CO2-rich methanol 8-i-b and the second non-reformed CO2-rich methanol 8-ii are returned to the second H2S absorption section, the second CO2 absorption section and the second purification section, respectively.

[0095] According to the present application, preferably, as shown in Figure 1 As shown, the first primary CO2-rich methanol 9-i and the low-sulfur methanol 20 are returned to the second H2S absorption section.

[0096] In the present application, as shown in Figure 1 As shown, in the non-reformed gas purification tower T-1, the first purification section is used to contact the non-reformed gas 1 and the second non-reformed H2S-rich methanol 2-ii and perform first purification, to obtain pre-purified non-reformed H2S-rich methanol 4 and pre-desulfurized non-reformed gas; the second purification section is used to contact the pre-desulfurized non-reformed gas and the second non-reformed CO2-rich methanol 8-ii and perform second purification, to obtain the non-reformed H2S-rich methanol 2 and desulfurized non-reformed gas; the third purification section is used to contact the desulfurized non-reformed gas and the first methanol-lean 3-i and perform third purification, to obtain the non-reformed CO2-rich methanol 8 and purified non-reformed gas 5.

[0097] In the present application, as shown in Figure 1As shown, in the H2S absorption tower T-2, a first H2S absorption section is used for contacting the synthesis gas 6 and a first stream of non-shift H2S-rich methanol 2-i and performing first H2S absorption to obtain the first H2S-rich methanol 7 and pre-desulfurized gas; a second H2S absorption section is used for contacting the pre-desulfurized gas, low-sulfur methanol 20, a stream of non-shift CO2-rich methanol 8-i-a and a first stream of first CO2-rich methanol 9-i and performing second H2S absorption to obtain desulfurized gas 11 and second H2S-rich methanol 10.

[0098] In the present application, as shown in Figure 1 As shown, in the CO2 absorption tower T-3, a first CO2 absorption section is used for contacting the desulfurized gas 11 and second CO2-rich methanol 12 and performing first CO2 absorption to obtain first CO2-rich methanol 9 and pre-purified gas; a second CO2 absorption section is used for contacting the pre-purified gas, low-carbon methanol 24, a stream of non-shift CO2-rich methanol 8-i-b and a second stream of lean methanol 3-ii and performing second CO2 absorption to obtain second CO2-rich methanol 12 and purified gas 14.

[0099] In the present application, as shown in Figure 1 As shown, the medium-pressure flash tower T-4 is divided into a CO2 flash section, a washing section and an H2S flash section from top to bottom, the CO2 flash section is used for CO2 flashing of a second stream of first CO2-rich methanol 9-ii to obtain CO2 flash gas 15 and CO2 flash liquid 17; the H2S flash section is used for H2S flashing of the second H2S-rich methanol 10 to obtain H2S flash gas and H2S flash liquid 19; the washing section is used for first washing of a third stream of non-shift H2S-rich methanol 2-iii, CO2 flash gas 15 and H2S flash gas to obtain washed flash gas 15 and second H2S-rich methanol 19.

[0100] According to the present application, as shown in Figure 1 As shown, in the reabsorption tower T-5, a first flash section is used for first flashing of a first stream of CO2 flash liquid 17-i to obtain semi-lean liquid methanol 13 and a first stream of CO2 product gas; a second flash section is used for second flashing of a second stream of CO2 flash liquid 17-ii to obtain flash liquid and a second stream of CO2 product gas; a third flash section is used for third flashing of H2S flash liquid 19 to obtain first H2S-rich methanol 21, and the sulfur-containing gas phase obtained is contacted with the flash liquid through a rising hole to obtain low-sulfur methanol 20 and a third stream of CO2 product gas; wherein the first stream of CO2 product gas, the second stream of CO2 product gas and the third stream of CO2 product gas are mixed to obtain CO2 product gas 22.

[0101] According to the present application, as shown in Figure 1As shown, the low-carbon methanol stripping tower T-6 is used to contact and strip the first stream of semi-lean methanol 13-i with nitrogen 23 after heat exchange in the heat exchanger Q to obtain low-carbon methanol 24 and tail gas 25.

[0102] According to the present application, preferably, as shown in Figure 1 As shown, a first pump P-1 is arranged on the pipeline connecting the second flash evaporation section and the second H2S absorption section, for performing the secondary H2S absorption after first pressurizing the low-sulfur methanol 20.

[0103] According to the present application, preferably, as shown in Figure 1 As shown, a first cooler E-1 is arranged on the pipeline connecting the second H2S absorption section and the H2S flash evaporation section, for performing the H2S flash evaporation after first cooling the secondary H2S-rich methanol 10.

[0104] According to the present application, preferably, as shown in Figure 1 As shown, in the direction of material flow, a second pump P-2 and a second cooler E-2 are arranged in sequence on the pipeline connecting the second H2S absorption section and the first CO2 absorption section, for performing the secondary H2S absorption after sequentially second pressurizing and second cooling the first stream of primary CO2-rich methanol 9-i.

[0105] According to the present application, preferably, as shown in Figure 1 As shown, in the direction of material flow, a third cooler E-3 is arranged on the pipeline connecting the first CO2 absorption section and the second CO2 absorption section, for performing the primary CO2 absorption after third cooling the secondary CO2-rich methanol 12.

[0106] According to the present application, preferably, as shown in Figure 1 As shown, in the direction of material flow, a third pump P-3 is arranged on the pipeline connecting the low-carbon methanol stripping tower T-6 and the second CO2 absorption section, for performing the secondary CO2 absorption after third pressurizing the low-carbon methanol 24.

[0107] According to the present application, preferably, as shown in Figure 1 As shown, a fourth cooler E-4 is arranged on the pipeline connecting the third purification section, the second H2S absorption section and the second CO2 absorption section, for performing the secondary H2S absorption and the secondary CO2 absorption respectively after fourth cooling the a stream of non-shift CO2-rich methanol 8-i-a and the b stream of non-shift CO2-rich methanol 8-i-b respectively.

[0108] According to the present application, preferably, as shown in Figure 1 As shown, a fifth cooler E-5 is arranged on the pipeline connecting the heat exchanger Q and the first flash evaporation section, for performing the first flash evaporation after fifth cooling the first stream of CO2 flash evaporation liquid 17-i.

[0109] According to the present application, preferably, as shown in Figure 1 A sixth cooler E-6 is arranged on the pipeline connecting the heat exchanger Q and the second flash section, and the second stream of CO2 liquid 17-ii is cooled by the sixth cooler E-6 before being subjected to the second flash.

[0110] The present application will be described in detail below by way of examples.

[0111] In the present application, unless otherwise specified, the synthesis gas and the non-shift gas are both derived from a pulverized coal gasification device.

[0112] Example 1

[0113] The device, as shown in Figure 1 The device includes a non-shift gas purification tower T-1, an H2S absorption tower T-2, a CO2 absorption tower T-3, a medium-pressure flash tower T-4, a reabsorption tower T-5, a low-carbon methanol stripping tower T-6, and 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, a second pump P-2, a third pump P-3, and a heat exchanger Q.

[0114] The method is performed in the above device, and includes:

[0115] The non-shift gas 1 (the molar content of H2S is 0.4-0.6%, the molar content of CO2 is 5-10%; the temperature is -35 to -25°C, and the pressure is 3.5-3.6 MPa (G)) and the second stream of non-shift H2S-rich methanol 2-ii are contacted at a molar flow ratio of 115-125:1 to perform first purification, to obtain pre-purified non-shift H2S-rich methanol 4 (the molar content of H2S is 0.6-1.1%, the molar content of CO2 is 2-5%; the temperature is -35 to -25°C) and pre-desulfurized non-shift gas; the above pre-desulfurized non-shift gas and the second stream of non-shift CO2-rich methanol 8-ii are contacted to perform second purification, to obtain non-shift H2S-rich methanol 2 (the molar content of H2S is 0.5-0.9%, the molar content of CO2 is 3-7%; the temperature is -32 to -28°C; the pressure is 3.5-3.55 MPa (G)) and desulfurized non-shift gas; the above desulfurized non-shift gas and the first stream of methanol-lean 3-i are contacted to perform third purification, to obtain non-shift CO2-rich methanol 8 (the molar content of H2S is 0.5-1 ppm, the molar content of CO2 is 3-8%; the temperature is -40 to -33°C) and purified non-shift gas 5 (the molar content of H2S is ≤0.1 ppm, the molar content of CO2 is ≤20 ppm; the temperature is -55 to -45°C, and the pressure is 3.4-3.5 MPa (G));

[0116] wherein the above non-shift H2S-rich methanol 2 is divided into a first non-shift H2S-rich methanol 2-i, a second non-shift H2S-rich methanol 2-ii and a third non-shift H2S-rich methanol 2-iii with a molar flow ratio of 4-6:1:72-76; wherein the above non-shift CO2-rich methanol 8 is divided into a non-shift CO2-rich methanol 8-i-a, a non-shift CO2-rich methanol 8-i-b and a second non-shift CO2-rich methanol 8-ii with a molar flow ratio of 1:1:1-3;

[0117] wherein the molar flow ratio of the above second non-shift CO2-rich methanol 8-ii and non-shift gas 1 is 1:1-2; the molar flow ratio of the above first methanol-lean 3-i and non-shift gas 1 is 1.5-2.5:1-2;

[0118] The above synthesis gas 6 (molar content of H2S is 0.3-0.35%, molar content of CO2 is 40-50%; temperature is -25 to -15°C, pressure is 3.12-3.15 MPa(G)) and the first non-shift H2S-rich methanol 2-i are contacted with a molar flow ratio of 50-54:1 and a first H2S absorption is carried out to obtain a pre-desulfurization gas and a first H2S-rich methanol 7 (molar content of H2S is 0.6-0.8%, molar content of CO2 is 30-36%; temperature is -25 to -15°C); the above pre-desulfurization gas, low-sulfur methanol 20 (firstly pressurized to 3.6-4 MPa(G)), the non-shift CO2-rich methanol 8-i-a (fourthly cooled to -46 to -43°C) and the first first H2S-rich CO2 methanol 9-i (secondly pressurized to 3.6-4 MPa(G), secondly cooled to -46 to -43°C) are contacted and a second H2S absorption is carried out to obtain a desulfurization gas 11 (molar content of H2S is 0.5-1 ppm, molar content of CO2 is 30-35%; temperature is -25 to -15°C; pressure is 3.05-3.1 MPa(G)) and a second H2S-rich methanol 10 (molar content of H2S is 0.3-0.6%, molar content of CO2 is 25-30%; temperature is -20 to -16°C);

[0119] wherein the molar flow ratio of the above low-sulfur methanol 20 and synthesis gas 6 is 1:3-5; the molar flow ratio of the first first H2S-rich CO2 methanol 9-i and synthesis gas 6 is 2-4:5-8; the molar flow ratio of the non-shift CO2-rich methanol 8-i-a and synthesis gas 6 is 1:5-8;

[0120] The desulfurized gas 11 and the second-stage CO2-rich methanol 12 (cooled to -36 to -33°C by the third cooler) are contacted at a molar flow ratio of 1:1-3 and subjected to a first-stage CO2 absorption to obtain a first-stage CO2-rich methanol 9 (molar content of H2S: 0.1-0.5 ppm, molar content of CO2: 16-20%, temperature: -22 to -18°C, pressure: 3.05-3.09 MPa (G)) and a pre-purified gas; the pre-purified gas, the low-carbon methanol 24 (pressurized to 3.6-4 MPa (G) by the third pressurizer), the b-portion non-shift CO2-rich methanol 8-i-b (cooled to -46 to -43°C by the fourth cooler), and the second-portion lean methanol 3-ii are contacted and subjected to a second-stage CO2 absorption to obtain the second-stage CO2-rich methanol 12 and a purified gas 14 (molar content of H2S: ≤0.1 ppm, molar content of CO2: ≤20 ppm; temperature: -55 to -45°C, pressure: 3-3.05 MPa (G));

[0121] wherein the molar flow ratio of the purified gas 14 and the low-carbon methanol 24 is 1-1.3:1; the molar flow ratio of the purified gas 14 and the b-portion non-shift CO2-rich methanol 8-i-b is 3-5:1; the molar flow ratio of the purified gas 14 and the second-portion lean methanol 3-ii is 1:1-1.5; wherein the first-stage CO2-rich methanol 9 is divided into a first-portion first-stage CO2-rich methanol 9-i and a second-portion first-stage CO2-rich methanol 9-ii at a molar flow ratio of 1:2-4;

[0122] The second-portion first-stage CO2-rich methanol 9-ii is subjected to CO2 flashing (pressure: 0.8-1 MPa (G)) to obtain a CO2 flashing gas 15 and a CO2 flashing liquid 17 (molar content of H2S: 0.1-0.5 ppm, molar content of CO2: 15-19%, temperature: -25 to -21°C);

[0123] The second-stage H2S-rich methanol 10 (cooled to -36 to -33°C by the first cooler) is subjected to H2S flashing (pressure: 0.8-1 MPa (G)) to obtain an H2S flashing gas and an H2S flashing liquid 19 (molar content of H2S: 0.25-0.55%, molar content of CO2: 24.5-29.5%; temperature: -40 to -33°C);

[0124] wherein the third non-shift H2S-rich methanol 2-iii, the CO2 flash gas 15 and the H2S flash gas are first washed to obtain a washed flash gas 18 (molar content of H2S is 0.5-0.8%, molar content of CO2 is 15-19%, molar content of CO is 30-34%, molar content of H2 is 48-52%, temperature is -36 to -26°C, pressure is 0.8-1 MPa (G)) and a second H2S-rich methanol 16 (molar content of H2S is 0.6-0.8%, molar content of CO2 is 7-11%, temperature is -24 to -20°C);

[0125] The CO2 flash liquid 17 is heat-exchanged with the first semi-lean liquid methanol 13-i to obtain a heat-exchanged CO2 flash liquid (temperature is -30 to -25°C) which is divided into a first CO2 flash liquid 17-i and a second CO2 flash liquid 17-ii at a molar flow ratio of 3-5:1, and a heat-exchanged semi-lean liquid methanol (temperature is -45 to -42°C);

[0126] The first CO2 flash liquid 17-i (cooled to -40 to -36°C) is first flashed (pressure is 0.05-0.08 MPa (G)) to obtain the semi-lean liquid methanol 13 (molar content of H2S is 0.1-0.5 ppm, molar content of CO2 is 10-14%, temperature is -55 to -50°C, pressure is 0.05-0.08 MPa (G)) and a first CO2 product gas; the second CO2 flash liquid 17-ii (cooled to -52 to -48°C) is second flashed (pressure is 0.06-0.09 MPa (G)) to obtain a flash liquid and a second CO2 product gas; the H2S flash liquid 19 is third flashed (pressure is 0.12-0.16 MPa (G)) to obtain a first H2S-rich methanol 21 (molar content of H2S is 0.2-0.5%, molar content of CO2 is 15-20%, temperature is -65 to -60°C, pressure is 0.13-0.17 MPa (G)) and a sulfur-containing gas phase; wherein the flash liquid and the sulfur-containing gas phase are second washed to obtain a low-sulfur methanol 20 (molar content of H2S is 0.1-0.3%, molar content of CO2 is 14-18%, temperature is -56 to -52°C, pressure is 0.12-0.16 MPa (G)) and a third CO2 product gas;

[0127] wherein the first CO2 product gas, the second CO2 product gas and the third CO2 product gas are mixed to obtain a CO2 product gas 22 (molar content of H2S is ≤1 ppm, molar content of CO2 is 99.4-99.7%, temperature is -58 to -54°C, pressure is 0.05-0.08 MPa (G));

[0128] The above semi-lean methanol 13 is divided into a first semi-lean methanol 13-i and a second semi-lean methanol 13-ii with a molar flow ratio of 1-2:1;

[0129] The above heat-exchanged semi-lean methanol is contacted with nitrogen 23 and subjected to gas stripping to obtain low-carbon methanol 24 (molar content of H2S: 0.1-0.5 ppm, molar content of CO2: 3-7%; temperature: -56 to -52°C) and tail gas 25 (molar content of H2S: 0.1-0.5 ppm, molar content of CO2: 84-88%; temperature: -50 to -40°C, pressure: 0.12-0.14 MPa (G)).

[0130] Comparative Example 1

[0131] Taking a hydrogen production device using pulverized coal gasification as an example, the effective gas (H2+CO) entering the low-temperature methanol washing device is 161000 Nm 3 / h, and the main technical parameters of the lean-liquid-semi-lean liquid process (i.e., CN201110260570.0 discloses a low-temperature methanol washing process) are compared with the above baseline, as shown in Table 1.

[0132] Table 1

[0133]

[0134] As can be seen from the results in Table 1, taking a hydrogen production device based on pulverized coal gasification as an example, the energy-saving multi-generation syngas purification technology provided in Example 1 for the supporting pulverized coal gasification device, the lean methanol circulation amount is 84.6% of the lean methanol circulation amount in Comparative Example 1 (lean-liquid-semi-lean liquid process), the semi-lean / low-carbon methanol circulation amount is 66.7% of the semi-lean / low-carbon methanol circulation amount in Comparative Example 1 (lean-liquid-semi-lean liquid process), the use amount of CO2-rich methanol in the H2S absorption tower is 80% of the use amount of CO2-rich methanol in Comparative Example 1 (lean-liquid-semi-lean liquid process), and the cumulative external cold consumption is reduced by 1300 KW / h, and the overall energy-saving effect is remarkable.

[0135] The above detailed description of the preferred embodiments of the present application, however, the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. An energy-saving poly-generation syngas purification method for a complete pulverized coal gasification plant, characterized in that, The method comprises: The synthesis gas (6) from the pulverized coal gasification device is sequentially subjected to primary H2S absorption, secondary H2S absorption, primary CO2 absorption, and secondary CO2 absorption to obtain primary H2S-rich methanol (7), secondary H2S-rich methanol (10), two streams of primary CO2-rich methanol (9), secondary CO2-rich methanol (12), and purified gas (14); wherein the second stream of primary CO2-rich methanol (9-ii) and the secondary H2S-rich methanol (10) are subjected to CO2 flashing and H2S flashing, respectively, to obtain CO2 flashing liquid (17), H2S flashing liquid (19), CO2 flashing gas (15), and H2S flashing gas; The CO2 flashing liquid (17) is divided into two streams after heat exchange, the first stream of CO2 flashing liquid (17-i), the second stream of CO2 flashing liquid (17-ii), and the H2S flashing liquid (19) are subjected to first flashing, second flashing, and third flashing, respectively, to obtain two streams of semi-lean liquid methanol (13), low-sulfur methanol (20), and first H2S-rich methanol (21); wherein the first stream of semi-lean liquid methanol (13-i) is subjected to stripping after heat exchange to obtain low-carbon methanol (24) which is returned to the secondary CO2 absorption; The non-shift H2S-rich methanol (2) from the non-shift gas purification process is divided into three streams, the first stream of non-shift H2S-rich methanol (2-i) and the second stream of non-shift H2S-rich methanol (2-ii) are returned to the primary H2S absorption and the non-shift gas purification process, respectively, and the third stream of non-shift H2S-rich methanol (2-iii) is subjected to first washing with CO2 flashing gas (15) and H2S flashing gas; the non-shift CO2-rich methanol (8) from the non-shift gas purification process is divided into a stream of non-shift CO2-rich methanol (8-i-a), b stream of non-shift CO2-rich methanol (8-i-b), and second stream of non-shift CO2-rich methanol (8-ii) which are returned to the secondary H2S absorption, the secondary CO2 absorption, and the non-shift gas purification process, respectively; wherein the first stream of primary CO2-rich methanol (9-i) and the low-sulfur methanol (20) are returned to the secondary H2S absorption, respectively.

2. The method of claim 1, wherein, The non-shift gas purification process comprises: subjecting the non-shift gas (1) to three-stage purification to obtain purified non-shift gas (5); Preferably, the three-stage purification comprises: first purification, second purification, and third purification; wherein the non-shift gas (1) and the second stream of non-shift H2S-rich methanol (2-ii) are contacted and subjected to the first purification to obtain pre-purified non-shift H2S-rich methanol (4) and pre-desulfurized non-shift gas; the pre-desulfurized non-shift gas and the second stream of non-shift CO2-rich methanol (8-ii) are contacted and subjected to the second purification to obtain the non-shift H2S-rich methanol (2) and desulfurized non-shift gas; the desulfurized non-shift gas and the first stream of lean methanol (3-i) are contacted and subjected to the third purification to obtain the non-shift CO2-rich methanol (8) and the purified non-shift gas (5); Preferably, the molar flow ratio of the non-shift gas (1) and the second stream of non-shift H2S-rich methanol (2-ii) is 1:115-125; Preferably, the non-shift H2S-rich methanol (2) has a molar content of H2S of 0.5-0.9%, a molar content of CO2 of 3-7%, a temperature of -32 to -28°C, and a pressure of 3.5-3.55 MPa (G); Preferably, the first non-shift H2S-rich methanol (2-i), the second non-shift H2S-rich methanol (2-ii), and the third non-shift H2S-rich methanol (2-iii) have a molar flow ratio of 4-6:1:72-76; Preferably, the non-shift CO2-rich methanol (8) has a molar content of H2S of 0.5-1 ppm, a molar content of CO2 of 3-8%, a temperature of -40 to -33°C; Preferably, the a non-shift CO2-rich methanol (8-i-a), the b non-shift CO2-rich methanol (8-i-b), and the second non-shift CO2-rich methanol (8-ii) have a molar flow ratio of 1:1:1-3.

3. The method of claim 1 or 2, wherein, The synthesis gas (6) and the first non-shift H2S-rich methanol (2-i) are contacted and subjected to the primary H2S absorption to obtain the primary H2S-rich methanol (7) and a pre-desulfurized gas; the pre-desulfurized gas, the low-sulfur methanol (20), the first primary CO2-rich methanol (9-i), and the a non-shift CO2-rich methanol (8-i-a) are contacted and subjected to the secondary H2S absorption to obtain the desulfurized gas (11) and the secondary H2S-rich methanol (10); Preferably, the secondary H2S-rich methanol (10) has a molar content of H2S of 0.3-0.6%, a molar content of CO2 of 25-30%, a temperature of -20 to -16°C; Preferably, the desulfurized gas (11) has a molar content of H2S of 0.5-1 ppm, a molar content of CO2 of 30-35%, a temperature of -25 to -15°C, and a pressure of 3.05-3.1 MPa (G); Preferably, the desulfurized gas (11) and the secondary CO2-rich methanol (12) are contacted and subjected to the primary CO2 absorption to obtain the primary CO2-rich methanol (9) and a pre-purified gas; The pre-purified gas, the low-carbon methanol (24), the b non-shift CO2-rich methanol (8-i-b), and the second lean methanol (3-ii) are contacted and subjected to the secondary CO2 absorption to obtain the secondary CO2-rich methanol (12) and a purified gas (14); Preferably, the primary CO2-rich methanol (9) has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 16-20%, a temperature of -22 to -18°C, and a pressure of 3.05-3.09 MPa (G); Preferably, the first primary CO2-rich methanol (9-i) and the second primary CO2-rich methanol (9-ii) have a molar flow ratio of 1:2-4.

4. The method of any of claims 1-3, wherein, The CO2 flash liquid (17) has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 15-19%, and a temperature of -25 to -21°C; Preferably, the heat exchange process comprises: exchanging heat between the CO2 flash liquid (17) and the first semi-lean liquid methanol (13-i) to obtain a heat-exchanged CO2 flash liquid with a temperature of -30 to -25℃ and a heat-exchanged semi-lean liquid methanol with a temperature of -45 to -42℃; Preferably, the molar flow ratio of the first CO2 flash liquid (17-i) to the second CO2 flash liquid (17-ii) is 3-5:1; Preferably, the H2S flash liquid (19) has a molar content of H2S of 0.25-0.55% and a molar content of CO2 of 24.5-29.5%, and a temperature of -40 to -34℃; Preferably, the CO2 flash and H2S flash have a pressure of 0.8-1 MPa (G) respectively.

5. The method of any of claims 1-4, wherein, The first CO2 flash liquid (17-i) is subjected to the first flash to obtain the semi-lean liquid methanol (13) and a first CO2 product gas; the second CO2 flash liquid (17-ii) is subjected to the second flash to obtain a flash liquid and a second CO2 product gas; and the H2S flash liquid (19) is subjected to the third flash to obtain the first H2S-rich methanol (21) and a sulfur-containing gas phase; wherein the flash liquid and the sulfur-containing gas phase are contacted and subjected to a second washing to obtain low-sulfur methanol (20) and a third CO2 product gas; and the first CO2 product gas, the second CO2 product gas and the third CO2 product gas are mixed to obtain a CO2 product gas (22); Preferably, the semi-lean liquid methanol (13) has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 10-14%, a temperature of -55 to -50℃, and a pressure of 0.05-0.08 MPa (G); Preferably, the molar flow ratio of the first semi-lean liquid methanol (13-i) to the second semi-lean liquid methanol (13-ii) is 1-2:1; Preferably, the low-sulfur methanol (20) has a molar content of H2S of 0.1-0.3% and a molar content of CO2 of 14-18%, a temperature of -56 to -52℃, and a pressure of 0.12-0.16 MPa (G); Preferably, the CO2 product gas (22) has a molar content of H2S of ≤1 ppm and a molar content of CO2 of 99.4-99.7%, a temperature of -58 to -54℃, and a pressure of 0.05-0.08 MPa (G).

6. The method of any of claims 1-5, wherein, The stripping process comprises: contacting the first semi-lean liquid methanol (13-i) with nitrogen (23) after the heat exchange and subjecting to the stripping to obtain the low-carbon methanol (24) and a tail gas (25); Preferably, the low-carbon methanol (24) has a molar content of H2S of 0.1-0.5 ppm and a molar content of CO2 of 3-7%, a temperature of -56 to -52℃; Preferably, the process of the first washing comprises: contacting the third non-shift H2S-rich methanol (2-iii) with the CO2 flash gas (15) and H2S flash gas respectively and performing the first washing to obtain second H2S-rich methanol (16) and washed flash gas (18); Preferably, the molar content of H2S in the washed flash gas (18) is 0.5-0.8%, the molar content of CO2 is 15-19%, the molar content of CO is 30-34%, the molar content of H2 is 48-52%, the temperature is -36 to -26℃, and the pressure is 0.8-1 MPa (G).

7. The method of any of claims 1-6, wherein, After the low-sulfur methanol (20) is first pressurized to 3.6-4 MPa (G), the secondary H2S absorption is performed; Preferably, after the secondary H2S-rich methanol (10) is first cooled to -36 to -33℃, the H2S flashing is performed; Preferably, in the direction of material flow, the first primary CO2-rich methanol (9-i) is sequentially subjected to second pressurization to 3.6-4 MPa (G) and second cooling to -46 to -43℃, and then the secondary H2S absorption is performed; Preferably, in the direction of material flow, the secondary CO2-rich methanol (12) is subjected to third cooling to -36 to -33℃, and then the primary CO2 absorption is performed; Preferably, in the direction of material flow, the low-carbon methanol (24) is subjected to third pressurization to 3.6-4 MPa (G), and then the secondary CO2 absorption is performed; Preferably, the a non-shift CO2-rich methanol (8-i-a) and b non-shift CO2-rich methanol (8-i-b) are respectively subjected to fourth cooling to -46 to -43℃, and then the secondary H2S absorption and the secondary CO2 absorption are respectively performed; Preferably, the first CO2 flash liquid (17-i) is subjected to fifth cooling to -40 to -36℃, and then the first flashing is performed; Preferably, the second CO2 flash liquid (17-ii) is subjected to sixth cooling to -52 to -48℃, and then the second flashing is performed.

8. An energy-saving poly-generation syngas purification device of a complete pulverized coal gasification device, characterized in that, The device comprises: connected non-shift gas purification tower (T-1), H2S absorption tower (T-2), CO2 absorption tower (T-3), medium-pressure flash tower (T-4), reabsorption tower (T-5) and low-carbon methanol stripping tower (T-6); The H2S absorption tower (T-2) is used for sequentially performing primary H2S absorption and secondary H2S absorption on the synthesis gas (6) from the pulverized coal gasification device to obtain primary H2S-rich methanol (7), secondary H2S-rich methanol (10) and desulfurized gas (11); the CO2 absorption tower (T-3) is used for sequentially performing primary CO2 absorption and secondary CO2 absorption on the desulfurized gas (11) to obtain two stocks of primary CO2-rich methanol (9), secondary CO2-rich methanol (12) and purified gas (14); The medium-pressure flash tower (T-4) is divided into a CO2 flash section, a washing section and an H2S flash section from top to bottom, the CO2 flash section is used for CO2 flashing of the second primary CO2-rich methanol (9-ii), the obtained CO2 flash gas (15) is sent to the washing section through a pipeline, and the obtained CO2 flash liquid (17) is divided into two streams after a heat exchanger (Q); and the H2S flash section is used for H2S flashing of the secondary H2S-rich methanol (10), the obtained H2S flash gas is sent to the washing section through a gas riser, and the obtained H2S flash liquid (19) is obtained; The reabsorption tower (T-5) is divided into a first flash section, a second flash section and a third flash section from top to bottom, and is respectively used for first flashing, second flashing and third flashing of the first CO2 flash liquid (17-i), the second CO2 flash liquid (17-ii) and the H2S flash liquid (19) respectively, to obtain two streams of semi-lean liquid methanol (13), low-sulfur methanol (20) and first H2S-rich methanol (21); Among them, the first stream of semi-lean liquid methanol (13-i) is sent to the low-carbon methanol stripping tower (T-6) for stripping after the heat exchanger (Q), and the obtained low-carbon methanol (24) is returned to the CO2 absorption tower (T-3); Among them, the non-shift H2S-rich methanol (2) derived from the non-shift gas purification tower (T-1) is divided into three streams, the first non-shift H2S-rich methanol (2-i) and the second non-shift H2S-rich methanol (2-ii) are returned to the H2S absorption tower (T-2) and the non-shift gas purification tower (T-1) respectively, and the third non-shift H2S-rich methanol (2-iii) is sent to the washing section to be washed with the CO2 flash gas (15) and the H2S flash gas; the non-shift CO2-rich methanol (8) derived from the non-shift gas purification tower (T-1) is divided into a non-shift CO2-rich methanol (8-i-a), a non-shift CO2-rich methanol (8-i-b) and a second non-shift CO2-rich methanol (8-ii), which are returned to the H2S absorption tower (T-2), the CO2 absorption tower (T-3) and the non-shift gas purification tower (T-1) respectively; the first primary CO2-rich methanol (9-i) and the low-sulfur methanol (20) are returned to the H2S absorption tower (T-2) respectively.

9. The apparatus of claim 8, wherein, The non-shift gas purification tower (T-1) is divided into a first purification section, a second purification section and a third purification section from bottom to top, which are communicated through gas risers; the H2S absorption tower (T-2) is divided into a first H2S absorption section and a second H2S absorption section from bottom to top, which are communicated through gas risers; and the CO2 absorption tower (T-3) is divided into a first CO2 absorption section and a second CO2 absorption section from bottom to top, which are communicated through gas risers; Preferably, the first non-shift H2S-rich methanol (2-i) and the second non-shift H2S-rich methanol (2-ii) are returned to the first H2S absorption section and the first purification section respectively; Preferably, the first non-shift H2S-rich methanol (2-i) and the second non-shift H2S-rich methanol (2-ii) are returned to the first H2S absorption section and the first purification section respectively; Preferably, the a-th non-reformed CO2-rich methanol (8-i-a), b-th non-reformed CO2-rich methanol (8-i-b) and second non-reformed CO2-rich methanol (8-ii) return to the second H2S absorption section, second CO2 absorption section and second purification section respectively; Preferably, the first primary CO2-rich methanol (9-i) and low-sulfur methanol (20) return to the second H2S absorption section respectively.

10. The apparatus of claim 9, wherein, A first pump (P-1) is arranged on the pipeline connecting the second flash section and the second H2S absorption section, for performing the secondary H2S absorption after the low-sulfur methanol (20) is first pressurized. Preferably, a first cooler (E-1) is arranged on the pipeline connecting the second H2S absorption section and the H2S flash section, for performing the H2S flash after the secondary H2S-rich methanol (10) is first cooled. Preferably, in the material flow direction, a second pump (P-2) and a second cooler (E-2) are arranged in sequence on the pipeline connecting the second H2S absorption section and the first CO2 absorption section, for performing the secondary H2S absorption after the first primary CO2-rich methanol (9-i) is second pressurized and second cooled in sequence; Preferably, in the material flow direction, a third cooler (E-3) is arranged on the pipeline connecting the first CO2 absorption section and the second CO2 absorption section, for performing the primary CO2 absorption after the secondary CO2-rich methanol (12) is third cooled; Preferably, in the material flow direction, a third pump (P-3) is arranged on the pipeline connecting the low-carbon methanol stripping tower (T-6) and the second CO2 absorption section, for performing the secondary CO2 absorption after the low-carbon methanol (24) is third pressurized; Preferably, a fourth cooler (E-4) is arranged on the pipeline connecting the third purification section, the second H2S absorption section and the second CO2 absorption section, for performing the secondary H2S absorption and the secondary CO2 absorption respectively after the a-th non-reformed CO2-rich methanol (8-i-a) and b-th non-reformed CO2-rich methanol (8-i-b) are fourth cooled respectively; Preferably, a fifth cooler (E-5) is arranged on the pipeline connecting the heat exchanger (Q) and the first flash section, for performing the first flash after the first CO2 flash liquid (17-i) is fifth cooled; Preferably, a sixth cooler (E-6) is arranged on the pipeline connecting the heat exchanger (Q) and the second flash section, for performing the second flash after the second CO2 flash liquid (17-ii) is sixth cooled.

Images