Energy-saving poly-generation synthesis gas purification process 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 medium-pressure 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 while effective gas is desorbed; the gas stripping process is optimized, and the H2S-rich gas generated by gas stripping is subjected to multi-stage series absorption, so that the device has the characteristic of low 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] H2 and CO in the synthetic gas produced by the pulverized coal gasification technology are called effective gas, and the synthetic gas also contains a large amount of CO2 and a small amount of H2S, COS, NH3, HCN and other components. The acid gases CO2 and H2S are generally poisons of the synthesis catalyst, so they must be removed before the synthesis process.

[0003] The low-temperature methanol washing technology is to absorb and remove the acid gases such as H2S and CO2 in the synthetic gas by using low-temperature methanol as the absorption solvent, and to remove the trace components such as HCN and NH3. In the multi-production low-temperature methanol washing process, the non-shift CO2-rich methanol solution has the characteristics of not containing H2S gas and low CO2 content, and the non-shift H2S-rich methanol has the characteristics of low CO2 content and relatively high CO gas content, and both of the two rich methanol have the potential for reuse, which is the key to energy saving of the multi-production low-temperature methanol washing process. The washing of the tail gas of the reabsorption tower needs a large amount of CO2-rich methanol, and if the tail gas washing process can be optimized and improved, the use amount of the CO2-rich methanol can be saved, and the energy consumption of the multi-production low-temperature methanol washing device can be reduced.

[0004] CN201110260570.0 discloses a low-temperature methanol washing process, which uses CO2-rich methanol to wash the synthetic gas in the H2S absorption tower, increases the generation amount of H2S-rich methanol, and the H2S-rich methanol can be recycled only after being heated and regenerated, which has high energy consumption. In the CO2 flashing section of the reabsorption tower, the CO2-rich methanol is directly mixed with the H2S-rich methanol while washing the H2S-rich methanol flashing gas, and the CO2-rich methanol is polluted by the H2S-rich methanol, and the low-concentration H2S methanol produced is not fully used, which has high energy consumption. The tail gas washing is not set reasonably, and different H2S content methanol is not selectively used for washing according to the H2S content in the tail gas, so as to reduce the heat regeneration energy consumption of the whole low-temperature methanol washing. The medium-pressure flashing process is not set reasonably, and the H2S-rich methanol of the washing flashing gas is directly mixed with the washing liquid, which is not conducive to the low temperature in the reabsorption tower.

[0005] CN201810994082.4 discloses a low-temperature methanol washing system and a synthetic gas providing method. The technology performs secondary utilization on the non-shift H2S-rich methanol after the non-shift gas is washed, but only uses the H2S-rich methanol after the medium-pressure flashing of the H2S-rich methanol as the flashing gas washing methanol, which is not efficient enough, and there is still room for improvement and energy consumption reduction. SUMMARY

[0006] The present application aims to overcome the problems of the prior art, such as the unreasonable process setting of the pressure flash tower and the reabsorption tower, the unreasonable use of non-shift rich CO2 methanol and non-shift rich H2S methanol, and provides an energy-saving multi-generation synthetic gas purification method matched with a pulverized coal gasification device and an energy-saving multi-generation synthetic gas purification device matched with a pulverized coal gasification device. The method optimizes the configuration of the medium-pressure flash process, uses non-shift rich H2S methanol to wash CO2 flash gas and H2S flash gas, and realizes the secondary absorption of the flash gas while desorbing the effective gas; by optimizing the setting of the gas stripping process, the rich H2S gas generated by the gas stripping is subjected to multi-stage series absorption, and the method 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 multi-generation synthetic gas purification method matched with a pulverized coal gasification device, which comprises:

[0008] The non-shift gas is subjected to three-stage purification to obtain pre-purified non-shift rich H2S methanol, two groups of non-shift rich H2S methanol, two groups of non-shift rich CO2 methanol, and purified non-shift gas; the synthetic gas is subjected to two-stage H2S absorption to obtain primary rich H2S methanol, two groups of secondary rich H2S methanol, and desulfurized gas; the desulfurized gas is subjected to two-stage CO2 absorption to obtain two groups of primary rich CO2 methanol, secondary rich CO2 methanol, and purified gas;

[0009] The second group of primary rich CO2 methanol is subjected to CO2 flashing to obtain CO2 flash gas and CO2 flash liquid; the first group of secondary rich H2S methanol is subjected to H2S flashing to obtain H2S flash gas and H2S flash liquid; the CO2 flash liquid is subjected to first flashing to obtain three groups of semi-lean liquid methanol, the second group of semi-lean liquid methanol and the H2S flash liquid are subjected to second flashing and third flashing, respectively, to obtain low H2S methanol and first rich H2S methanol;

[0010] The first group of non-shift rich H2S methanol is subjected to fourth flashing to obtain fourth flash liquid, which is subjected to first washing with the CO2 flash gas and the H2S flash gas, respectively, to obtain second rich H2S methanol and third group of semi-lean liquid methanol, which are subjected to first gas stripping, respectively, to obtain first gas stripping liquid; the first rich H2S methanol and the third rich H2S methanol are subjected to second gas stripping, respectively, to obtain second gas stripping gas and the first gas stripping liquid is subjected to second washing to obtain the third rich H2S methanol;

[0011] The second non-shift H2S-rich methanol and the second non-shift CO2-rich methanol are returned to the third purification respectively; the second H2S-rich methanol, the low H2S methanol and the first CO2-rich methanol are returned to the two-stage H2S absorption respectively; the first non-shift CO2-rich methanol, the first semi-lean liquid methanol and the second CO2-rich methanol are returned to the two-stage CO2 absorption respectively.

[0012] The second aspect of the present application provides an energy-saving multi-production synthesis gas purification device matched with a pulverized coal gasification device, the device comprising: a non-shift gas purification tower, an H2S absorption tower, a CO2 absorption tower, an H2S medium-pressure flash tower, a CO2 medium-pressure flash tower and a reabsorption tower connected;

[0013] The non-shift gas purification tower is used for purifying non-shift gas in three stages to obtain pre-purified non-shift H2S-rich methanol, two groups of non-shift H2S-rich methanol, two groups of non-shift CO2-rich methanol and purified non-shift gas;

[0014] The H2S absorption tower is used for absorbing H2S in two stages to obtain first H2S-rich methanol, two groups of second H2S-rich methanol and desulfurized gas;

[0015] The CO2 absorption tower is used for absorbing CO2 in two stages to obtain two groups of first CO2-rich methanol, second CO2-rich methanol and purified gas;

[0016] The CO2 medium-pressure flash tower is used for flashing CO2 from the second group of first CO2-rich methanol to obtain CO2 flash gas and CO2 flash liquid; the H2S medium-pressure flash tower comprises a washing section arranged on the upper part and an H2S flash section arranged on the lower part, and the H2S flash section is used for flashing H2S from the first group of second H2S-rich methanol to obtain H2S flash gas and H2S flash liquid;

[0017] The reabsorption tower comprises an upper tower and a lower tower, the upper tower is divided into a first flash section, a second flash section and a third flash section from top to bottom, and the lower tower is divided into a first gas stripping section and a second gas stripping section from top to bottom; the first flash section is used for first flashing the CO2 flash liquid to obtain three groups of semi-lean liquid methanol; the second flash section and the third flash section are respectively used for second flashing and third flashing the second group of semi-lean liquid methanol and the H2S flash liquid to obtain low H2S methanol and first H2S-rich methanol;

[0018] The fourth flash liquid obtained by the fourth flashing of the first non-shift H2S-rich methanol is subjected to first washing with the CO2 flash gas and the H2S flash gas respectively to obtain second H2S-rich methanol; the first gas stripping unit is used for subjecting the second H2S-rich methanol and the third group of semi-lean liquid methanol to first gas stripping respectively to obtain first gas stripping liquid; the second gas stripping unit is used for subjecting the first H2S-rich methanol and the third H2S-rich methanol to second gas stripping respectively to obtain second gas stripping gas which is sent to the first gas stripping unit through a rising hole and subjected to second washing with the first gas stripping liquid to obtain the third H2S-rich methanol;

[0019] The second group of non-shift H2S-rich methanol and the second group of non-shift CO2-rich methanol are returned to the non-shift gas purification tower respectively; the second group of secondary H2S-rich methanol, the low H2S methanol and the first group of primary CO2-rich methanol are returned to the H2S absorption tower respectively; the first group of non-shift CO2-rich methanol, the first group of semi-lean liquid methanol and the secondary CO2-rich methanol are returned to the CO2 absorption tower respectively.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] (1) The method provided by the present application uses the first group of non-shift H2S-rich methanol to perform first washing on the flash gas (i.e., the CO2 flash gas and the H2S flash gas), and the first group of non-shift H2S-rich methanol desorbs its own effective gas while realizing secondary absorption of the flash gas, and the washing liquid and the washed liquid are not mixed; compared with the prior art, the reduction of the H2S flash liquid concentration is avoided, and lower temperature can be generated in the reabsorption tower; at the same time, the second H2S-rich methanol obtained by the first washing is fully utilized, which has a lower sulfur content, and is sent to the reabsorption tower for washing of tail gas, which is beneficial to reducing the energy consumption of the device;

[0022] (2) The present application adopts a three-stage tail gas washing technology, and selectively sets the third group of semi-lean liquid methanol, the second H2S-rich methanol and the first H2S-rich methanol according to the different H2S contents in the tail gas, and the three groups of methanol with different H2S contents are sequentially washed from high to low, so that the tail gas emission meets the standard, and the third group of semi-lean liquid methanol is used as little as possible, thereby reducing the heat regeneration energy consumption of the entire low-temperature methanol washing;

[0023] (3) The method provided by the present application optimizes the reabsorption process, realizes the absorption of the sulfur-containing gas phase (for example, H2S) generated by the third flashing of the H2S flash liquid by the second flash liquid obtained by the second flashing of the second group of semi-lean liquid methanol, and the first H2S-rich methanol after the third flashing is not mixed with each other;

[0024] (4) The method provided by the application optimizes the CO2 absorption tower absorption process, fully utilizes the low carbon content feature of the non-shift CO2-rich methanol, carries out CO2 absorption, reduces the use amount of lean methanol, and is beneficial to reducing the energy consumption of the device. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a structural schematic diagram of an energy-saving multi-production syngas purification device matched with a pulverized coal gasification device.

[0026] REFERENCE SIGNS

[0027] T-1, non-shift gas purification tower; T-2, H2S absorption tower; T-3, CO2 absorption tower; T-4, H2S medium-pressure flash tower; T-5, CO2 medium-pressure flash tower; T-6, reabsorption tower;

[0028] 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-1, first heat exchanger; Q-2, second heat exchanger;

[0029] 1, non-shift gas; 2, non-shift H2S-rich methanol; 2-i, first non-shift H2S-rich methanol; 2-ii, second non-shift H2S-rich methanol; 3, lean methanol; 3-i, first lean methanol; 3-ii, second lean methanol; 4, pre-purified non-shift H2S-rich methanol; 5, purified non-shift gas; 6, syngas; 7, primary H2S-rich methanol; 8, non-shift CO2-rich methanol; 8-i, first non-shift CO2-rich methanol; 8-ii, second non-shift CO2-rich methanol; 9, primary CO2-rich methanol; 9-i, first primary CO2-rich methanol; 9-ii, second primary CO2-rich methanol; 10, secondary H2S-rich methanol; 10-i, first secondary H2S-rich methanol; 10-ii, second secondary H2S-rich methanol; 11, desulfurized gas; 12, secondary CO2-rich methanol; 13, semi-lean liquid methanol; 13-i, first semi-lean liquid methanol; 13-ii, second semi-lean liquid methanol; 13-iii, third semi-lean liquid methanol; 14, purified gas; 15, tail gas; 16, third H2S-rich methanol; 17, H2S-rich methanol after gas stripping; 18, flash gas after washing; 19, H2S flash liquid; 20, first H2S-rich methanol; 21, low H2S methanol; 22, CO2 product gas; 23, CO2 flash gas; 24, CO2 flash liquid; 25, second H2S-rich methanol; 26, nitrogen. DETAILED DESCRIPTION

[0030] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numeric range recited is intended to include all values between the recited upper and lower values, inclusive of the recited values. In this context, combinations of the above-mentioned ranges are also part of the disclosure.

[0031] In the present invention, without special circumstances, "first", "second", "third", "fourth", "fifth" and "sixth" neither represent the order of precedence, nor represent the limitation of each material or step, but only for distinguishing or indicating that it is not the same step or material.

[0032] In the present invention, without special circumstances, the "top" of the container refers to the height of 0-10% from top to bottom of the container; the "upper part" of the container refers to the height of 10-40% from top to bottom of the container; the "middle part" of the container refers to the height of 40-60% from top to bottom of the container; the "lower part" of the container refers to the height of 60-90% from top to bottom of the container; the "bottom" of the container refers to the height of 90-100% from top to bottom of the container.

[0033] The first aspect of the present invention provides an energy-saving multi-generation syngas purification method matched with a pulverized coal gasification device, the method comprising:

[0034] The non-shift gas is subjected to three-stage purification to obtain pre-purified non-shift H2S-rich methanol, two streams of non-shift H2S-rich methanol, two streams of non-shift CO2-rich methanol, and purified non-shift gas; the syngas is subjected to two-stage H2S absorption to obtain first-stage H2S-rich methanol, two streams of second-stage H2S-rich methanol, and desulfurized gas; the desulfurized gas is subjected to two-stage CO2 absorption to obtain two streams of first-stage CO2-rich methanol, second-stage CO2-rich methanol, and purified gas;

[0035] The second stream of first-stage CO2-rich methanol is subjected to CO2 flashing to obtain CO2 flashing gas and CO2 flashing liquid; the first stream of second-stage H2S-rich methanol is subjected to H2S flashing to obtain H2S flashing gas and H2S flashing liquid; the CO2 flashing liquid is subjected to first flashing to obtain three streams of semi-lean liquid methanol, the second stream of semi-lean liquid methanol is subjected to second flashing, and the H2S flashing liquid is subjected to third flashing to obtain low-H2S methanol and first H2S-rich methanol;

[0036] The first non-shift H2S-rich methanol is fourth flashed to obtain a fourth flash liquid, the fourth flash liquid is first washed with the CO2 flash gas and the H2S flash gas respectively to obtain a second H2S-rich methanol and a third semi-lean liquid methanol, the first H2S-rich methanol and the third H2S-rich methanol are respectively second gas stripped to obtain a second gas stripping gas and a first gas stripping liquid, and the first gas stripping liquid is second washed to obtain the third H2S-rich methanol.

[0037] The second non-shift H2S-rich methanol and the second non-shift CO2-rich methanol are returned to the third purification respectively, the second secondary H2S-rich methanol, the low H2S methanol and the first primary CO2-rich methanol are returned to the two-stage H2S absorption respectively, and the first non-shift CO2-rich methanol, the first semi-lean liquid methanol and the secondary CO2-rich methanol are returned to the two-stage CO2 absorption respectively.

[0038] In some embodiments of the present application, preferably, the non-shift gas and the synthesis gas are both derived from a pulverized coal gasification device, wherein the synthesis gas is prepared from the non-shift gas through a shift process.

[0039] In the present application, preferably, the mole content of H2S in the synthesis gas is 0.3-0.35%, the mole content of CO2 is 40-50%, the temperature is-25 to-15℃, and the pressure is 3.12-3.15 MPa (G); the mole content of H2S in the non-shift gas is 0.4-0.6%, the mole content of CO2 is 5-10%, the temperature is-35 to-25℃, and the pressure is 3.5-3.6 MPa (G).

[0040] In some embodiments of the present application, preferably, the third purification comprises a first purification, a second purification and a third purification; the non-shift gas and the second non-shift H2S-rich methanol are subjected to the first purification to obtain a pre-purified non-shift H2S-rich methanol and a pre-desulfurized non-shift gas; the pre-desulfurized non-shift gas and the second non-shift CO2-rich methanol are subjected to the second purification to obtain the non-shift H2S-rich methanol and a desulfurized non-shift gas; and the desulfurized non-shift gas and a first lean methanol are subjected to the third purification to obtain the non-shift CO2-rich methanol and a purified non-shift gas.

[0041] In the present application, the first purification aims to remove HCN, NH3 and other impurities as well as 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.

[0042] In the present application, preferably, the molar flow ratio of the non-reformed gas and the second non-reformed H2S-rich methanol is 50-60:1; further preferably, the molar content of H2S in the pre-purified non-reformed H2S-rich methanol is 0.8-1.2%, the molar content of CO2 is 3-6%; the temperature is -30 to -25℃, and it is sent to the subsequent process for treatment.

[0043] In some embodiments of the present application, preferably, the molar content of H2S in the non-reformed H2S-rich methanol is 0.5-0.9%, the molar content of CO2 is 3-7%; the temperature is -32 to -28℃; the pressure is 3.5-3.55 MPa (G).

[0044] In the present application, the non-reformed H2S-rich methanol is divided into two streams, the first stream is subjected to the fourth flash and then the first washing, and the second stream is subjected to the first purification. Further preferably, the molar flow ratio of the first non-reformed H2S-rich methanol and the second non-reformed H2S-rich methanol is 37-42:1.

[0045] In some embodiments of the present application, preferably, the molar content of H2S in the non-reformed CO2-rich methanol is 0.5-1 ppm, the molar content of CO2 is 3-8%; the temperature is -40 to -33℃.

[0046] In the present application, the non-reformed CO2-rich methanol is divided into two streams, the first stream is subjected to the secondary CO2 absorption, and the second stream is subjected to the second purification. Further preferably, the molar flow ratio of the first non-reformed CO2-rich methanol and the second non-reformed CO2-rich methanol is 1:1-1.1.

[0047] In the present application, preferably, the molar flow ratio of the second non-reformed CO2-rich methanol and the non-reformed gas is 1:1-2; the molar flow ratio of the first methanol-lean stream and the non-reformed gas is 1.5-2.5:1-2.

[0048] In some embodiments of the present application, preferably, the molar content of H2S in the methanol-lean stream is 0%, the molar content of CO2 is 0%. In the present application, the methanol-lean stream is selected from the subsequent process. In the present application, unless otherwise specified, the methanol-lean stream is divided into a first methanol-lean stream and a second methanol-lean stream; the present application does not limit the molar flow ratio of the first methanol-lean stream and the second methanol-lean stream.

[0049] In the present application, preferably, the molar content of H2S in the purified non-reformed 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).

[0050] In some embodiments of the present application, preferably, the two-stage H2S absorption comprises a first-stage H2S absorption and a second-stage H2S absorption; wherein the first-stage H2S absorption is performed on the synthesis gas and a second stream of second-stage H2S-rich methanol to obtain the first-stage H2S-rich methanol and a pre-desulfurized gas; and the second-stage H2S absorption is performed on the pre-desulfurized gas, low-H2S methanol and a first stream of first-stage CO2-rich methanol to obtain the desulfurized gas and second-stage H2S-rich methanol.

[0051] In the present application, the first-stage H2S absorption is intended to remove HCN, NH3 and other impurities in the synthesis gas, as well as a small amount of H2S and CO2; and the second-stage H2S absorption is intended to further remove H2S and CO2 in the synthesis gas.

[0052] In the present application, preferably, the molar flow ratio of the synthesis gas to the second stream of second-stage H2S-rich methanol is 50-54:1; further preferably, the molar content of H2S in the first-stage H2S-rich methanol is 0.6-0.8%, and the molar content of CO2 is 30-36%; and the temperature is -25 to -15℃, which is sent to subsequent processes.

[0053] In the present application, preferably, the molar flow ratio of the low-H2S methanol to the synthesis gas is 1:3-4; and the molar flow ratio of the first stream of first-stage CO2-rich methanol to the synthesis gas is 1:2-3.

[0054] In some embodiments of the present application, preferably, the molar content of H2S in the second-stage H2S-rich methanol is 0.3-0.6%, and the molar content of CO2 is 30-34%; and the temperature is -22 to -18℃.

[0055] In the present application, the second-stage H2S-rich methanol is divided into two streams, the first stream is subjected to the H2S flashing; and the second stream is subjected to the first-stage H2S absorption. Further preferably, the molar flow ratio of the first stream of second-stage H2S-rich methanol to the second stream of second-stage H2S-rich methanol is 1:40-45.

[0056] In some embodiments of the present application, preferably, the molar content of H2S in the desulfurized gas is 0.5-1 ppm, and the molar content of CO2 is 34-38%; the temperature is -30 to -20℃; and the pressure is 3.05-3.1 MPa(G).

[0057] In some embodiments of the present application, preferably, the low-H2S methanol is subjected to the second-stage H2S absorption after being first pressurized to 3.6-4 MPa(G) in the direction of material flow.

[0058] In some embodiments of the present application, preferably, the two-stage CO2 absorption comprises: a first-stage CO2 absorption and a second-stage CO2 absorption; wherein the desulfurized gas and the second-stage CO2-rich methanol are subjected to the first-stage CO2 absorption to obtain the first-stage CO2-rich methanol and a pre-purified gas; the pre-purified gas, the first stream of semi-lean liquid methanol, the first stream of non-shift CO2-rich methanol and the second stream of lean methanol are subjected to the second-stage CO2 absorption to obtain the second-stage CO2-rich methanol and a purified gas.

[0059] In the present application, both the first-stage CO2 absorption and the second-stage CO2 absorption are intended to further remove CO2 in the desulfurized gas. Preferably, the molar flow ratio of the desulfurized gas to the second-stage CO2-rich methanol is 1:1.5-2.5; the molar flow ratio of the purified gas to the first stream of semi-lean liquid methanol is 1-2:1, the molar flow ratio of the purified gas to the first stream of non-shift CO2-rich methanol is 3-5:1; and the molar flow ratio of the purified gas to the second stream of lean methanol is 1:1-2.

[0060] In some embodiments of the present application, preferably, the first-stage CO2-rich methanol has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 20-25%, a temperature of -24 to -20°C and a pressure of 3.05-3.09 MPa (G).

[0061] In some embodiments of the present application, further preferably, the first stream of first-stage CO2-rich methanol and the second stream of first-stage CO2-rich methanol have a molar flow ratio of 1:2-4.

[0062] In some embodiments of the present application, preferably, the first stream of non-shift CO2-rich methanol is subjected to the second-stage CO2 absorption after being cooled to -48 to -43°C.

[0063] In some embodiments of the present application, preferably, the first stream of first-stage CO2-rich methanol is subjected to the second-stage H2S absorption after being sequentially subjected to a second pressurization to 3.6-4 MPa (G) and a second cooling to -46 to -43°C.

[0064] In some embodiments of the present application, preferably, the second-stage CO2-rich methanol is subjected to the first-stage CO2 absorption after being subjected to a third cooling to -36 to -33°C.

[0065] In some embodiments of the present application, preferably, the first stream of semi-lean liquid methanol is subjected to the second-stage CO2 absorption after being subjected to a third pressurization to 3.6-4 MPa (G).

[0066] In some embodiments of the present application, preferably, the H2S molar content in the purified gas is ≤0.1 ppm, the CO2 molar content is ≤20 ppm; the temperature is -55 to -50℃, and the pressure is 3-3.05 MPa (G).

[0067] In the present application, the second primary CO2-rich methanol is subjected to CO2 flashing to obtain CO2 flashing gas and CO2 flashing liquid; the first secondary H2S-rich methanol is subjected to H2S flashing to obtain H2S flashing gas and H2S flashing liquid.

[0068] In some embodiments of the present application, preferably, the CO2 flashing and H2S flashing are carried out at a pressure of 0.8-1 MPa (G) respectively.

[0069] In some embodiments of the present application, preferably, the first secondary H2S-rich methanol is subjected to the H2S flashing after being cooled to -36 to -33℃ by the fourth cooling.

[0070] In some embodiments of the present application, preferably, the H2S molar content in the CO2 flashing liquid is 0.1-0.5 ppm, the CO2 molar content is 18.5-23.5%, and the temperature is -26.5 to -22.5℃.

[0071] In some embodiments of the present application, preferably, the H2S molar content in the H2S flashing liquid is 0.25-0.55%, the CO2 molar content is 29.5-33.5%, and the temperature is -40 to -34℃.

[0072] In some embodiments of the present application, preferably, the CO2 flashing liquid is subjected to the first flashing to obtain semi-lean liquid methanol and a first CO2 product gas; the second semi-lean liquid methanol is subjected to the second flashing to obtain a second flashing liquid and a second CO2 product gas; the H2S flashing liquid is subjected to the third flashing to obtain the first H2S-rich methanol and a sulfur-containing gas phase; wherein the second flashing liquid and the sulfur-containing gas phase are contacted to obtain low-H2S methanol and a third CO2 product gas; 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.

[0073] In some embodiments of the present application, preferably, the CO2 flashing liquid is subjected to the first flashing after being cooled to -50 to -46℃ by the fifth cooling.

[0074] In some embodiments of the present application, preferably, after the fifth cooling of the CO2 flash liquid, the first flash is performed to obtain the semi-lean liquid methanol and a first stream of CO2 product gas; the second flash is performed on the second stream of semi-lean liquid methanol to obtain a second flash liquid and a second stream of CO2 product gas; the third flash is performed on the H2S flash liquid to obtain the first H2S-rich methanol and a sulfur-containing gas phase; wherein the second flash liquid and the sulfur-containing gas phase are contacted to obtain low-H2S methanol 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 the CO2 product gas.

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

[0076] 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 15-19%, the temperature is -62 to -58℃, and the pressure is 0.05-0.08 MPa (G); further preferably, the molar flow ratio of the first stream of semi-lean liquid methanol, the second stream of semi-lean liquid methanol and the third stream of semi-lean liquid methanol is 1.5-2.5:1:1-2.

[0077] In some embodiments of the present application, preferably, the molar content of H2S in the low-H2S methanol is 0.1-0.3%, the molar content of CO2 is 17-21%, the temperature is -58 to -54℃, and the pressure is 0.12-0.16 MPa (G).

[0078] 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 -65 to -55℃, and the pressure is 0.05-0.08 MPa (G).

[0079] In some embodiments of the present application, preferably, the molar content of H2S in the first H2S-rich methanol is 0.25-0.55%, the molar content of CO2 is 19-22%, the temperature is -68 to -64℃, and the pressure is 0.13-0.17 MPa (G).

[0080] In some embodiments of the present application, preferably, the process of the first washing comprises: subjecting the first non-shift H2S-rich methanol to the fourth flash to obtain a fourth flash liquid, contacting the fourth flash liquid with the CO2 flash gas and the H2S flash gas respectively and subjecting to the first washing to obtain second H2S-rich methanol and a post-washing flash gas. In the present application, preferably, the pressure of the fourth flash is 0.8-1 MPa (G).

[0081] In some embodiments of the present application, further preferably, the molar content of H2S in the second H2S-rich methanol is 0.4-0.8%, the molar content of CO2 is 11-16%, and the temperature is -12 to -16℃.

[0082] In some embodiments of the present application, further preferably, the molar content of H2S in the post-washing flash gas is 0.6-0.8%, the molar content of CO2 is 28-32%, the molar content of CO is 16-20%, the molar content of H2 is 48-52%, the temperature is -30 to -20℃, and the pressure is 0.8-1 MPa (G).

[0083] In some embodiments of the present application, preferably, the second H2S-rich methanol and the third semi-lean liquid methanol are contacted with nitrogen respectively and subjected to the first stripping to obtain first stripping gas and first stripping liquid; the first H2S-rich methanol and the third H2S-rich methanol are contacted with nitrogen respectively and subjected to the second stripping to obtain second stripping gas and post-stripping H2S-rich methanol.

[0084] In some embodiments of the present application, preferably, the second H2S-rich methanol is subjected to the first stripping after being cooled to -52 to -50℃ by the sixth cooling.

[0085] In some embodiments of the present application, preferably, the first H2S-rich methanol is subjected to the second stripping after being cooled to -40 to -36℃ by the first heat exchange.

[0086] In some embodiments of the present application, preferably, the third H2S-rich methanol is subjected to the second stripping after being cooled to -40 to -36℃ by the second heat exchange.

[0087] In some embodiments of the present application, preferably, the first stripping liquid and the second stripping gas are subjected to the second washing to obtain the third H2S-rich methanol, and the obtained second washing gas is mixed with the first stripping gas to obtain tail gas.

[0088] In some embodiments of the present application, preferably, the molar content of H2S in the third H2S-rich methanol is 0.1-0.3%, the molar content of CO2 is 10-16%, and the temperature is -60 to -55℃.

[0089] In some embodiments of the present application, further preferably, the molar content of H2S in the tail gas is ≤1 ppm, the molar content of CO2 is 73-78%, and the temperature is -66 to -62℃.

[0090] The second aspect of the present application provides a structural diagram of an energy-saving multi-production syngas purification device matched with a pulverized coal gasification device, as shown in the figure. Figure 1 As can be seen, the device comprises a connected non-shift gas purification tower T-1, an H2S absorption tower T-2, a CO2 absorption tower T-3, an H2S medium-pressure flash tower T-4, a CO2 medium-pressure flash tower T-5, and a reabsorption tower T-6. Figure 1 The non-shift gas purification tower T-1 is used for three-stage purification of non-shift gas 1 to obtain pre-purified non-shift H2S-rich methanol 4, two streams of non-shift H2S-rich methanol 2, two streams of non-shift CO2-rich methanol 8, and purified non-shift gas 5.

[0091] The H2S absorption tower T-2 is used for two-stage H2S absorption of syngas 6 to obtain first-stage H2S-rich methanol 7, two streams of second-stage H2S-rich methanol 10, and desulfurized gas 11.

[0092] The CO2 absorption tower T-3 is used for two-stage CO2 absorption of the desulfurized gas 11 to obtain two streams of first-stage CO2-rich methanol 9, second-stage CO2-rich methanol 12, and purified gas 14.

[0093] The CO2 medium-pressure flash tower T-5 is used for CO2 flashing of the second stream of first-stage CO2-rich methanol 9-ii to obtain CO2 flashing gas 23 sent to the H2S flashing section through a pipeline, and CO2 flashing liquid 24; the H2S medium-pressure flash tower T-4 comprises a washing section arranged on the top and an H2S flashing section arranged on the bottom, and the H2S flashing section is used for H2S flashing of the first stream of second-stage H2S-rich methanol 10-i to obtain H2S flashing liquid 19 and H2S flashing gas sent to the washing section through a riser, respectively.

[0094] The reabsorption tower T-6 comprises an upper tower and a lower tower, the upper tower is divided into a first flashing part, a second flashing part, and a third flashing part from top to bottom, and the lower tower is divided into a first stripping part and a second stripping part from top to bottom; the first flashing part is used for first flashing of the CO2 flashing liquid 24 to obtain three streams of semi-lean liquid methanol 13; the second flashing part and the third flashing part are used for second flashing and third flashing of the second stream of semi-lean liquid methanol 13-ii and the H2S flashing liquid 19, respectively, to obtain low-H2S methanol 21 and first H2S-rich methanol 20.

[0095]

[0096] ​The washing section is used for fourth flash evaporation of the first non-shift H2S-rich methanol 2-i, and the obtained fourth flash evaporation liquid is respectively subjected to first washing with the CO2 flash gas 23 and the H2S flash gas to obtain second H2S-rich methanol 25; the first gas stripping part is used for first gas stripping of the second H2S-rich methanol 25 and the third group of semi-lean liquid methanol 13-iii respectively to obtain first gas stripping liquid; the second gas stripping part is used for second gas stripping of the first H2S-rich methanol 20 and the third H2S-rich methanol 16 respectively, and the second gas stripping gas is sent to the first gas stripping part through a riser hole and subjected to second washing with the first gas stripping liquid to obtain the third H2S-rich methanol 16.

[0097] The second group of non-shift H2S-rich methanol 2-ii and the second group of non-shift CO2-rich methanol 8-ii are returned to the non-shift gas purification tower T-1 respectively; the second group of secondary H2S-rich methanol 10-ii, low H2S-rich methanol 21 and the first group of primary CO2-rich methanol 9-i are returned to the H2S absorption tower T-2 respectively; the first group of non-shift CO2-rich methanol 8-i, the first group of semi-lean liquid methanol 13-i and the secondary CO2-rich methanol 12 are returned to the CO2 absorption tower T-3 respectively.

[0098] In the present application, as shown in Figure 1 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 and communicated through a riser hole.

[0099] In the present application, as shown in Figure 1 In the non-shift gas purification tower T-1, the first purification section is used for first purification of the non-shift gas 1 and the second group of non-shift H2S-rich methanol 2-ii to obtain pre-purified non-shift H2S-rich methanol 4 and pre-desulfurized non-shift gas; the second purification section is used for the second purification of the pre-desulfurized non-shift gas and the second group of non-shift CO2-rich methanol 8-ii to obtain the non-shift H2S-rich methanol 2 and the desulfurized non-shift gas; and the third purification section is used for the third purification of the desulfurized non-shift gas and the first group of lean methanol 3-i to obtain the non-shift CO2-rich methanol 8 and the purified non-shift gas 5.

[0100] In the present application, as shown in Figure 1 The H2S absorption tower T-2 is divided into a first H2S absorption section and a second H2S absorption section from bottom to top and communicated through a riser hole.

[0101] In the present application, as shown in Figure 1As shown, the H2S absorption tower T-2, a first H2S absorption section, is used for first H2S absorption of the synthesis gas 6 and a second stream of secondary H2S-rich methanol 10-ii to obtain the first H2S-rich methanol 7 and a pre-desulfurized gas; a second H2S absorption section is used for second H2S absorption of the pre-desulfurized gas, low H2S methanol 21 and a first stream of primary CO2-rich methanol 9-i to obtain desulfurized gas 11 and secondary H2S-rich methanol 10.

[0102] According to the present application, preferably, as shown in Figure 1 As shown, according to the material flow direction, a first pump P-1 is arranged on the pipeline connecting the second flash evaporation section and the second H2S absorption section, which is used for first pressurization of the low H2S methanol 21 before the second H2S absorption.

[0103] 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 through a gas lift hole.

[0104] In the present application, as shown in Figure 1 As shown, the CO2 absorption tower T-3, wherein the first CO2 absorption section is used for first CO2 absorption of the desulfurized gas and secondary CO2-rich methanol 12 to obtain the first CO2-rich methanol 9 and a pre-purified gas; the second CO2 absorption section is used for second CO2 absorption of the pre-purified gas, a first stream of semi-lean liquid methanol 13-i, a first stream of non-shift CO2-rich methanol 8-i and a second stream of lean methanol 3-ii to obtain the secondary CO2-rich methanol 12 and purified gas 14.

[0105] 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 third purification section and the second CO2 absorption section, which is used for first cooling of the first stream of non-shift CO2-rich methanol 8-i before the second CO2 absorption.

[0106] According to the present application, preferably, as shown in Figure 1 As shown, according to 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, which are used for second pressurization and second cooling of the first stream of primary CO2-rich methanol 9-i in sequence before the second H2S absorption.

[0107] According to the present application, preferably, as shown in Figure 1 As shown, according to 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, which is used for third cooling of the secondary CO2-rich methanol 12 before the first CO2 absorption.

[0108] According to the present application, preferably, as shown in Figure 1 According to the present application, preferably, as shown in

[0109] According to the present application, preferably, as shown in Figure 1 According to the present application, preferably, as shown in

[0110] According to the present application, preferably, as shown in Figure 1 According to the present application, preferably, as shown in

[0111] According to the present application, preferably, as shown in Figure 1 According to the present application, preferably, as shown in

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

[0113] According to the present application, preferably, as shown in Figure 1As shown, in the lower tower of the reabsorption tower T-6, a first stripping section is used for contacting the second H2S-rich methanol 25 and the third semi-lean liquid methanol 13-iii with nitrogen 26 respectively and performing first stripping to obtain first stripping liquid and first stripping gas; a second stripping section is used for contacting the first H2S-rich methanol 20 and the third H2S-rich methanol 16 with nitrogen 26 respectively and performing second stripping to obtain second stripping gas which is sent to the first stripping section through a riser and performs second washing with the first stripping liquid to obtain the third H2S-rich methanol 16, and the obtained second washing gas is mixed with the first stripping gas to obtain tail gas 15.

[0114] 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 CO2 medium-pressure flash tower T-5 and the first flash section, which is used for performing the first flash after the fifth cooling of the CO2 flash liquid 24.

[0115] According to the present application, preferably, as shown in Figure 1 As shown, a sixth cooler E-6 is arranged on the pipeline connecting the washing section and the first stripping section, which is used for performing the first stripping after the sixth cooling of the second H2S-rich methanol 25.

[0116] According to the present application, preferably, as shown in Figure 1 As shown, a first heat exchanger Q-1 is arranged on the pipeline connecting the third flash section and the second stripping section, which is used for performing the second stripping after the first heat exchange of the first H2S-rich methanol 20.

[0117] According to the present application, preferably, as shown in Figure 1 As shown, a second heat exchanger Q-2 is arranged on the pipeline connecting the first stripping section and the second stripping section, which is used for performing the second stripping after the second heat exchange of the third H2S-rich methanol 16.

[0118] The present application will be described in detail through examples below.

[0119] In the present application, without special circumstances, the synthesis gas and the non-shift gas are both derived from a pulverized coal gasification device.

[0120] Example 1

[0121] The device is as shown in Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 Figure 1 FigureAs shown, the device comprises: a non-reformed gas purification tower T-1, an H2S absorption tower T-2, a CO2 absorption tower T-3, an H2S medium-pressure flash tower T-4, a CO2 medium-pressure flash tower T-5, a reabsorption tower T-6, and a first cooler E-1, a second cooler E-2, a third cooler E-3, a fourth cooler E-4 and a fifth cooler E-5, a sixth cooler E-6, and a first pump P-1, a second pump P-2, a third pump P-3, and a first heat exchanger Q-1, a second heat exchanger Q-2;

[0122] The method is carried out in the above device, comprising:

[0123] The non-reformed gas 1 (molar content of H2S: 0.4-0.6%, molar content of CO2: 5-10%; temperature: -35 to -25°C, pressure: 3.5-3.6 MPa(G)) and the second non-reformed H2S-rich methanol 2-ii are contacted at a molar flow ratio of 50-60:1 and subjected to first purification, to obtain pre-purified non-reformed H2S-rich methanol 4 (molar content of H2S: 0.8-1.2%, molar content of CO2: 3-6%; temperature: -30 to -25°C) and pre-desulfurized non-reformed gas; the above pre-desulfurized non-reformed gas and the second non-reformed CO2-rich methanol 8-ii are contacted and subjected to second purification, to obtain non-reformed H2S-rich methanol 2 (molar content of H2S: 0.5-0.9%, molar content of CO2: 3-7%; temperature: -32 to -28°C; pressure: 3.5-3.55 MPa(G)) and desulfurized non-reformed gas; the above desulfurized non-reformed gas and the first lean methanol 3-i are contacted and subjected to third purification, to obtain non-reformed CO2-rich methanol 8 (molar content of H2S: 0.5-1 ppm, molar content of CO2: 3-8%; temperature: -40 to -33°C) and purified non-reformed gas 5 (molar content of H2S: ≤0.1 ppm, molar content of CO2: ≤20 ppm; temperature: -55 to -45°C, pressure: 3.4-3.5 MPa(G));

[0124] Wherein the above non-reformed H2S-rich methanol 2 is divided into a first non-reformed H2S-rich methanol 2-i and a second non-reformed H2S-rich methanol 2-ii at a molar flow ratio of 37-41:1; wherein the above non-reformed CO2-rich methanol 8 is divided into a first non-reformed CO2-rich methanol 8-i and a second non-reformed CO2-rich methanol 8-ii at a molar flow ratio of 1:1-1.1;

[0125] Wherein the molar flow ratio of the above second non-reformed CO2-rich methanol 8-ii and non-reformed gas 1 is 1:1-2; the molar flow ratio of the above first lean methanol 3-i and non-reformed gas 1 is 1.5-2.5:1-2;

[0126] 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 second stream of secondary H2S-rich methanol 10-ii are contacted at a molar flow ratio of 50-54:1 and subjected to primary H2S absorption, to obtain pre-desulfurized gas and primary H2S-rich methanol 7 (molar content of H2S is 0.6-0.8%, molar content of CO2 is 30-36%; temperature is -25 to -15°C); the above pre-desulfurized gas, low-H2S methanol 21 (first pressurized to 3.6-4 MPa(G)), and the first stream of primary CO2-rich methanol 9-i (second pressurized to 3.6-4 MPa(G) and second cooled to -46 to -43°C) are contacted and subjected to secondary H2S absorption, to obtain desulfurized gas 11 (molar content of H2S is 0.5-1 ppm, molar content of CO2 is 34-38%; temperature is -30 to -20°C; pressure is 3.05-3.1 MPa(G)) and secondary H2S-rich methanol 10 (molar content of H2S is 0.3-0.6%, molar content of CO2 is 30-34%; temperature is -22 to -18°C);

[0127] wherein the molar flow ratio of the above low-H2S methanol 21 and synthesis gas 6 is 1:3-4; the molar flow ratio of the first stream of primary CO2-rich methanol 9-i and synthesis gas 6 is 1:2-3; the molar flow ratio of the first stream of secondary H2S-rich methanol 10-i and the second stream of secondary H2S-rich methanol 10-ii is 1:40-45;

[0128] The above desulfurized gas 11 and secondary CO2-rich methanol 12 (third cooled to -36 to -33°C) are contacted at a molar flow ratio of 1:1.5-2.5 and subjected to primary CO2 absorption, to obtain primary CO2-rich methanol 9 (molar content of H2S is 0.1-0.5 ppm, molar content of CO2 is 20-25%, temperature is -24 to -20°C, pressure is 3.05-3.09 MPa(G)) and pre-purified gas; the above pre-purified gas, the first stream of semi-lean liquid methanol 13-i (third pressurized to 3.6-4 MPa(G)), the first stream of non-shift CO2-rich methanol 8-i (first cooled to -48 to -43°C), and the second stream of lean methanol 3-ii are subjected to secondary CO2 absorption, to obtain secondary CO2-rich methanol 12 and purified gas 14 (molar content of H2S is ≤0.1 ppm, molar content of CO2 is ≤20 ppm; temperature is -55 to -50°C, pressure is 3-3.05 MPa(G));

[0129] wherein the molar flow ratio of the purified gas 14 to the first stream of semi-lean methanol 13-i is 1-2:1; the molar flow ratio of the purified gas 14 to the first stream of non-shifted rich CO2methanol 8-i is 3-5:1; the molar flow ratio of the purified gas 14 to the second stream of lean methanol 3-ii is 1:1-2; wherein the first rich CO2methanol 9 is divided into a first stream of first rich CO2methanol 9-i and a second stream of first rich CO2methanol 9-ii in a molar flow ratio of 1:2-4;

[0130] The second stream of first rich CO2methanol 9-ii is subjected to CO2 flashing (at a pressure of 0.8-1 MPa (G)) to obtain a CO2 flashing gas and a CO2 flashing liquid 24 (having a molar H2S content of 0.1-0.5 ppm, a molar CO2 content of 18.5-23.5%, and a temperature of -26.5 to -22.5°C);

[0131] The first stream of second rich H2S methanol 10-i (cooled to -36 to -33°C) is subjected to H2S flashing (at a pressure of 0.8-1 MPa (G)) to obtain a H2S flashing gas and a H2S flashing liquid 19 (having a molar H2S content of 0.25-0.55%, a molar CO2 content of 29.5-33.5%, and a temperature of -40 to -34°C);

[0132] The CO2 flashing liquid 24 (cooled to -50 to -46°C) is subjected to first flashing (at a pressure of 0.05-0.08 MPa (G)) to obtain a semi-lean methanol 13 (having a molar H2S content of 0.1-0.5 ppm, a molar CO2 content of 15-19%, and a temperature of -62 to -58°C; and a pressure of 0.05-0.08 MPa (G)) and a first stream of CO2 product gas; the second stream of semi-lean methanol 13-ii is subjected to second flashing (at a pressure of 0.06-0.09 MPa (G)) to obtain a second flashing liquid and a second stream of CO2 product gas; and the H2S flashing liquid 19 is subjected to third flashing (at a pressure of 0.12-0.16 MPa (G)) to obtain the first rich H2S methanol 20 (having a molar H2S content of 0.25-0.55%, a molar CO2 content of 19-22%, and a temperature of -68 to -64°C; and a pressure of 0.13-0.17 MPa (G)) and a sulfur-containing gas phase; wherein the second flashing liquid and the sulfur-containing gas phase are contacted to obtain a low H2S methanol 21 (having a molar H2S content of 0.1-0.3%, a molar CO2 content of 17-21%, and a temperature of -58 to -54°C; and a pressure of 0.12-0.16 MPa (G)) and a third stream of CO2 product gas;

[0133] The first, second and third CO2 product gas are mixed to obtain CO2 product gas 22 (molar content of H2S ≤ 1 ppm, molar content of CO2 99.4-99.7%; temperature -65 to -55°C, pressure 0.05-0.08 MPa (G));

[0134] The semi-lean methanol 13 is divided into first, second and third semi-lean methanols 13-i, 13-ii and 13-iii in a molar flow ratio of 1.5-2.5:1:1-2;

[0135] The first non-shift H2S-rich methanol 2-i is subjected to fourth flashing (pressure 0.8-1 MPa (G)) to obtain fourth flash liquid, which is contacted with CO2 flash gas 23 and H2S flash gas and subjected to first washing to obtain second H2S-rich methanol 25 (molar content of H2S 0.4-0.8%, molar content of CO2 11-16%; temperature -12 to -16°C) and washed flash gas 18 (molar content of H2S 0.6-0.8%, molar content of CO2 28-32%; molar content of CO 16-20%, molar content of H2 48-52%; temperature -30 to -20°C, pressure 0.8-1 MPa (G));

[0136] The second H2S-rich methanol 25 (cooled to -52 to -50°C) and the third semi-lean methanol 13-iii are contacted with nitrogen gas 26 and subjected to first stripping to obtain first stripping gas and first stripping liquid; the first H2S-rich methanol 20 (first heat exchange -40 to -36°C) and the third H2S-rich methanol 16 (second heat exchange -40 to -36°C) are contacted with nitrogen gas 26 and subjected to second stripping to obtain second stripping gas and stripped H2S-rich methanol 17 (molar content of H2S 0.2-0.6%, molar content of CO2 2-3%; temperature -54 to -50°C);

[0137] The first stripping liquid and the second stripping gas are subjected to second washing to obtain third H2S-rich methanol 16 (molar content of H2S 0.1-0.3%, molar content of CO2 10-16%; temperature -60 to -55°C), and the obtained second washing gas is mixed with the first stripping gas to obtain tail gas 15 (molar content of H2S ≤ 1 ppm, molar content of CO2 73-78%; temperature -66 to -62°C).

[0138] Comparative Example 1

[0139] 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-mentioned baseline, as shown in Table 1.

[0140] Table 1

[0141]

[0142] 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 synthesis gas purification process provided by Example 1 for the supporting pulverized coal gasification device, the lean methanol circulation amount is 86.2% of the lean liquid methanol circulation amount in Comparative Example 1 (lean liquid-semi-lean liquid process), the semi-lean methanol circulation amount is 69.2% of the semi-lean liquid 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 1100 KW / h, and the overall energy-saving effect is remarkable.

[0143] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for purifying syngas from a multi-product coal gasification unit, characterized in that, The method includes: The non-conversion gas (1) is purified in three stages to obtain pre-purified non-conversion H2S-rich methanol (4), non-conversion H2S-rich methanol (2) split into two streams, non-conversion CO2-rich methanol (8) split into two streams, and purified non-conversion gas (5); the synthesis gas (6) is subjected to two-stage H2S absorption to obtain first-stage H2S-rich methanol (7), second-stage H2S-rich methanol (10) split into two streams, and desulfurized gas (11); the desulfurized gas (11) is subjected to two-stage CO2 absorption to obtain first-stage CO2-rich methanol (9) split into two streams, second-stage CO2-rich methanol (12), and purified gas (14); The second primary CO2-rich methanol (9-ii) was subjected to CO2 flash evaporation to obtain CO2 flash vapor (23) and CO2 flash liquid (24); the first secondary H2S-rich methanol (10-i) was subjected to H2S flash evaporation to obtain H2S flash vapor and H2S flash liquid (19); the CO2 flash liquid (24) was subjected to first flash evaporation to obtain semi-lean methanol (13), which was divided into three streams. The second semi-lean methanol (13-ii) and H2S flash liquid (19) were subjected to second and third flash evaporation respectively to obtain low H2S methanol (21) and primary H2S-rich methanol (20); The first non-conversion H2S-rich methanol (2-i) undergoes a fourth flash evaporation, and the resulting fourth flash liquid is washed with the CO2 flash vapor (23) and H2S flash vapor respectively. The resulting second H2S-rich methanol (25) and third semi-lean methanol (13-iii) are then subjected to a first gas stripping to obtain a first gas stripping liquid. The first H2S-rich methanol (20) and the third H2S-rich methanol (16) are then subjected to a second gas stripping to obtain a second gas stripping gas. The first gas stripping liquid is then washed with the second gas stripping liquid to obtain the third H2S-rich methanol (16). Among them, the second non-conversion H2S-rich methanol (2-ii) and the second non-conversion CO2-rich methanol (8-ii) are returned to the three-stage purification, respectively; the second secondary H2S-rich methanol (10-ii), the low H2S methanol (21), and the first primary CO2-rich methanol (9-i) are returned to the two-stage H2S absorption, respectively; the first non-conversion CO2-rich methanol (8-i), the first semi-lean methanol (13-i), and the secondary CO2-rich methanol (12) are returned to the two-stage CO2 absorption, respectively.

2. The method according to claim 1, wherein, The non-conversion gas (1) and syngas (6) both originate from the pulverized coal gasification unit; Preferably, the three-stage purification includes: a first purification, a second purification, and a third purification; wherein, the non-conversion gas (1) and the second stream of non-conversion H2S-rich methanol (2-ii) are subjected to the first purification to obtain pre-purified non-conversion H2S-rich methanol (4) and pre-desulfurized non-conversion gas; the pre-desulfurized non-conversion gas and the second stream of non-conversion CO2-rich methanol (8-ii) are subjected to the second purification to obtain the non-conversion H2S-rich methanol (2) and desulfurized non-conversion gas; the desulfurized non-conversion gas and the first stream of lean methanol (3-i) are subjected to the third purification to obtain the non-conversion CO2-rich methanol (8) and purified non-conversion gas (5); Preferably, the non-conversion H2S-rich methanol (2) has a molar content of 0.5-0.9% for H2S and a molar content of 3-7% for CO2; a temperature of -32 to -28°C; and a pressure of 3.5-3.55 MPa(G). Preferably, the molar flow ratio of the first non-conversion H2S-rich methanol (2-i) and the second non-conversion H2S-rich methanol (2-ii) is 37-41:1; Preferably, the non-conversion CO2-rich methanol (8) has a molar content of H2S of 0.5-1 ppm and a molar content of CO2 of 3-8%; and a temperature of -40 to -33°C. Preferably, the molar flow ratio of the first non-conversion CO2-rich methanol (8-i) and the second non-conversion CO2-rich methanol (8-ii) is 1:1-1.

1.

3. The method according to claim 1 or 2, wherein, The two-stage H2S absorption includes primary H2S absorption and secondary H2S absorption; wherein, the synthesis gas (6) and the second secondary H2S-rich methanol (10-ii) are subjected to the primary H2S absorption to obtain the primary H2S-rich methanol (7) and pre-desulfurized gas; the pre-desulfurized gas, low H2S methanol (21) and the first primary CO2-rich methanol (9-i) are subjected to the secondary H2S absorption to obtain the desulfurized gas (11) and secondary H2S-rich methanol (10); Preferably, the molar content of H2S in the secondary H2S-rich methanol (10) is 0.3-0.6%, the molar content of CO2 is 30-34%, and the temperature is -22 to -18°C; More preferably, the molar flow ratio of the first secondary H2S-rich methanol (10-i) to the second secondary H2S-rich methanol (10-ii) is 1:40-45; Preferably, the desulfurization gas (11) has a molar content of H2S of 0.5-1 ppm and a molar content of CO2 of 34-38%; a temperature of -30 to -20°C; and a pressure of 3.05-3.1 MPa(G). Preferably, the low-H2S methanol (21) is pressurized to 3.6-4 MPa (G) in the first stage according to the material flow direction before the secondary H2S absorption is carried out.

4. The method according to any one of claims 1-3, wherein, The two-stage CO2 absorption includes: primary CO2 absorption and secondary CO2 absorption; wherein, the desulfurized gas (11) and secondary CO2-rich methanol (12) are subjected to the primary CO2 absorption to obtain primary CO2-rich methanol (9) and pre-purified gas; the pre-purified gas, the first semi-lean methanol (13-i), the first non-conversion CO2-rich methanol (8-i), and the second lean methanol (3-ii) are subjected to the secondary CO2 absorption to obtain secondary CO2-rich methanol (12) and purified gas (14); Preferably, the molar content of H2S in the first-grade CO2-rich methanol (9) is 0.1-0.5 ppm, the molar content of CO2 is 20-25%, the temperature is -24 to -20℃, and the pressure is 3.05-3.09 MPa(G); Preferably, the molar flow ratio of the first primary CO2-rich methanol (9-i) and the second primary CO2-rich methanol (9-ii) is 1:2-4; Preferably, the first non-conversion CO2-rich methanol (8-i) is cooled to -48 to -43°C before the secondary CO2 absorption is performed; Preferably, in accordance with the material flow direction, the first primary CO2-rich methanol (9-i) is sequentially pressurized to 3.6-4 MPa (G) and cooled to -46 to -43°C before undergoing the secondary H2S absorption; Preferably, the secondary CO2-rich methanol (12) is cooled to -36 to -33°C in the third stage according to the material flow direction before the primary CO2 absorption is carried out; Preferably, the first semi-lean methanol (13-i) is pressurized to 3.6-4 MPa (G) in the third pressurization process according to the material flow direction for the secondary CO2 absorption.

5. The method according to any one of claims 1-4, wherein, The pressures for CO2 flash evaporation and H2S flash evaporation are 0.8-1 MPa(G); Preferably, the first secondary H2S-rich methanol (10-i) is cooled to -36 to -33°C in a fourth cooling process before the H2S flash evaporation is performed; Preferably, the CO2 flash liquid (24) has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 18.5-23.5%, and a temperature of -26.5 to -22.5°C; Preferably, the H2S flash liquid (19) has a molar content of 0.25-0.55% for H2S and a molar content of 29.5-33.5% for CO2; and a temperature of -40 to -34°C. Preferably, the first non-conversion H2S-rich methanol (2-i) is subjected to the fourth flash evaporation, and the resulting fourth flash liquid is contacted with the CO2 flash vapor (23) and H2S flash vapor and subjected to the first washing to obtain the second H2S-rich methanol (25) and the washed flash vapor (18). Preferably, the molar content of H2S in the second H2S-rich methanol (25) is 0.4-0.8%, the molar content of CO2 is 11-16%, and the temperature is -12 to -16℃.

6. The method according to any one of claims 1-5, wherein, The CO2 flash liquid (24) is cooled to -50 to -46°C in the fifth stage before the first flash evaporation is performed. Preferably, the CO2 flash liquid (24) is subjected to a fifth cooling process, followed by the first flash evaporation to obtain the semi-lean methanol (13) and the first CO2 product gas; the second semi-lean methanol (13-ii) is subjected to the second flash evaporation to obtain the second flash liquid and the second CO2 product gas; the H2S flash liquid (19) is subjected to the third flash evaporation to obtain the first H2S-rich methanol (20) and the sulfur-containing gas phase; wherein the second flash liquid and the sulfur-containing gas phase are contacted to obtain low-H2S methanol (21) and the third CO2 product gas; wherein the first CO2 product gas, the second CO2 product gas and the third CO2 product gas are mixed to obtain CO2 product gas (22); Preferably, the semi-lean methanol (13) has a molar content of H2S of 0.1-0.5 ppm, a molar content of CO2 of 15-19%, a temperature of -62 to -58°C, and a pressure of 0.05-0.08 MPa(G). Preferably, the molar flow ratio of the first semi-lean methanol stream (13-i), the second semi-lean methanol stream (13-ii), and the third semi-lean methanol stream (13-iii) is 1.5-2.5:1:1-2; Preferably, the low-H2S methanol (21) has a molar content of H2S of 0.1-0.3% and a molar content of CO2 of 17-21%; the temperature is -58 to -54°C and the pressure is 0.12-0.16 MPa (G).

7. The method according to any one of claims 1-6, wherein, The second H2S-rich methanol (25) and the third semi-lean methanol (13-iii) were respectively contacted with nitrogen (26) and subjected to the first gas stripping to obtain the first gas stripping gas and the first gas stripping liquid; the first H2S-rich methanol (20) and the third H2S-rich methanol (16) were respectively contacted with nitrogen (26) and subjected to the second gas stripping to obtain the second gas stripping gas and the gas stripped H2S-rich methanol (17); Preferably, the second H2S-rich methanol (25) is cooled to -52 to -50°C in a sixth cooling process before the first gas stripping is performed; Preferably, the first H2S-rich methanol (20) is subjected to a first heat exchange to a temperature of -40 to -36°C before the second gas stripping is performed; Preferably, the third H2S-rich methanol (16) is subjected to a second heat exchange to a temperature of -40 to -36°C before the second gas stripping is performed; Preferably, the first stripping liquid and the second stripping gas are subjected to the second washing to obtain the third H2S-rich methanol (16), and the obtained second washing gas is mixed with the first stripping gas to obtain tail gas (15). Preferably, the molar content of H2S in the third H2S-rich methanol (16) is 0.1-0.3%, the molar content of CO2 is 10-16%, and the temperature is -60 to -55°C.

8. An energy-saving polygeneration syngas purification device for supporting a pulverized coal gasification device, characterized in that, The device includes: a non-shift gas purification tower (T-1), an H2S absorption tower (T-2), a CO2 absorption tower (T-3), an H2S medium-pressure flash evaporator (T-4), a CO2 medium-pressure flash evaporator (T-5), and a reabsorption tower (T-6) connected together; The non-conversion gas purification tower (T-1) is used to perform three-stage purification of non-conversion gas (1) to obtain pre-purified non-conversion H2S-rich methanol (4), non-conversion H2S-rich methanol (2) split into two streams, non-conversion CO2-rich methanol (8) split into two streams and purified non-conversion gas (5). The H2S absorption tower (T-2) is used to absorb H2S from the synthesis gas (6) in two stages to obtain first-stage H2S-rich methanol (7), second-stage H2S-rich methanol (10) in two streams and desulfurization gas (11). The CO2 absorption tower (T-3) is used to absorb the desulfurized gas (11) in two stages to obtain a first-stage CO2-rich methanol (9) divided into two streams, a second-stage CO2-rich methanol (12) and purified gas (14); The CO2 medium-pressure flash distillation tower (T-5) is used to perform CO2 flash distillation on the second primary CO2-rich methanol (9-ii), and the resulting CO2 flash vapor (23) is sent to the H2S flash distillation section through a pipeline, and a CO2 flash liquid (24) is obtained; the H2S medium-pressure flash distillation tower (T-4) includes a washing section set at the top and an H2S flash distillation section set at the bottom. The H2S flash distillation section is used to perform H2S flash distillation on the first secondary H2S-rich methanol (10-i), and the resulting H2S flash vapor and the CO2 flash vapor (23) are sent to the washing section through the riser holes, and an H2S flash liquid (19) is obtained; The reabsorption tower (T-6) includes an upper tower and a lower tower. The upper tower is divided into a first flash section, a second flash section and a third flash section from top to bottom, and the lower tower is divided into a first stripping section and a second stripping section from top to bottom. The first flash section is used to perform a first flash evaporation on the CO2 flash liquid (24) to obtain a semi-lean methanol (13) that is divided into three streams. The second flash section and the third flash section are used to perform a second flash evaporation on the second semi-lean methanol (13-ii) and a third flash evaporation on the H2S flash liquid (19) to obtain a low-H2S methanol (21) and a first H2S-rich methanol (20). The washing section is used to flash the first non-conversion H2S-rich methanol (2-i) for a fourth time, and the resulting fourth flash liquid is washed with the CO2 flash vapor (23) and H2S flash vapor to obtain the second H2S-rich methanol (25); the first stripping section is used to strip the second H2S-rich methanol (25) and the third semi-lean methanol (13-iii) for a first time to obtain the first stripping liquid; the second stripping section is used to strip the first H2S-rich methanol (20) and the third H2S-rich methanol (16) for a second time, and the resulting second stripping gas is sent to the first stripping section through the gas riser and washed with the first stripping liquid to obtain the third H2S-rich methanol (16); The second non-conversion H2S-rich methanol (2-ii) and the second non-conversion CO2-rich methanol (8-ii) are returned to the non-conversion gas purification tower (T-1); the second secondary H2S-rich methanol (10-ii), low H2S methanol (21) and the first primary CO2-rich methanol (9-i) are returned to the H2S absorption tower (T-2); the first non-conversion CO2-rich methanol (8-i), the first semi-lean methanol (13-i) and the secondary CO2-rich methanol (12) are returned to the CO2 absorption tower (T-3).

9. The apparatus according to claim 8, wherein, The non-shifting gas purification tower (T-1) is divided into a first purification section, a second purification section, and a third purification section connected by air risers from bottom to top; the H2S absorption tower (T-2) is divided into a first H2S absorption section and a second H2S absorption section connected by air risers from bottom to top; the CO2 absorption tower (T-3) is divided into a first CO2 absorption section and a second CO2 absorption section connected by air risers from bottom to top. Preferably, a first pump (P-1) is installed on the pipeline connecting the second flash section and the second H2S absorption section, according to the material flow direction; Preferably, a first cooler (E-1) is installed on the pipe connecting the third purification section and the second CO2 absorption section; Preferably, a second pump (P-2) and a second cooler (E-2) are sequentially installed on the pipeline connecting the second H2S absorption section and the first CO2 absorption section, according to the material flow direction; Preferably, a third cooler (E-3) is installed on the pipe connecting the first CO2 absorption section and the second CO2 absorption section, according to the material flow direction; Preferably, a third pump (P-3) is installed on the pipeline connecting the first flash section and the second CO2 absorption section, according to the material flow direction.

10. The apparatus according to claim 9, wherein, A fourth cooler (E-4) is installed on the pipe connecting the second H2S absorption section and the H2S flash section; Preferably, a fifth cooler (E-5) is installed on the pipe connecting the CO2 medium-pressure flash tower (T-5) and the first flash section; Preferably, a sixth cooler (E-6) is provided on the pipe connecting the washing section and the first air lifting section; Preferably, a first heat exchanger (Q-1) is provided on the pipe connecting the third flash section and the second stripping section; Preferably, a second heat exchanger (Q-2) is provided on the pipe connecting the first air lift section and the second air lift section.

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