Energy-saving and environment-friendly low-temperature methanol washing tail gas treatment system

Abstract

According to the energy-saving and environment-friendly low-temperature methanol washing tail gas treatment system provided by the utility model, in the system, the acid tail gas at the top of the thermal regeneration tower and the tail gas washed by the tail gas washing tower are thermally coupled at the tail gas device, so that the consumption of cooling water for cooling the acid tail gas at the top of the thermal regeneration tower can be reduced; and the energy-saving effect is achieved. Meanwhile, the temperature of the tail gas can be further increased, then the temperature of the tail gas is further increased through the heating coil, the final exhaust temperature of the tail gas is increased to 60 DEG C or above, at the moment, the amount of residual CO gas in the tail gas settling to the ground is reduced, and therefore pollution to the environment is relieved.

Description

Technical Field

[0001] The utility model relates to the technical field of low-temperature methanol washing process, and particularly relates to an energy-saving and environment-friendly low-temperature methanol washing tail gas treatment system. Background Art

[0002] In the process of producing chemical products with coal as raw material, it is necessary to purify the raw syngas generated by coal gasification, because the raw syngas contains a large amount of excess carbon dioxide, a small amount of hydrogen sulfide, COS, NH3 and other gases, and these gases are adverse to the subsequent production process. Among them, sulfides will cause poisoning of the catalyst in the downstream production reaction, so it is necessary to remove and recover them. At present, the low-temperature methanol washing system is the most mature gas purification technology and has been widely used in synthetic methanol, synthetic ammonia and coal gas purification devices. By using the characteristics of different gas solubilities in low-temperature methanol, the removal of carbon dioxide, hydrogen sulfide, COS, NH3 and other gases in the syngas is realized.

[0003] However, in the process of running the current low-temperature methanol washing system, a large amount of circulating cooling water is used; at the same time, the amount of CO settling to the ground in the tail gas treated by the current low-temperature methanol washing system is relatively large. Summary of the Utility Model

[0004] In order to solve the above problems, the utility model provides an energy-saving and environment-friendly low-temperature methanol washing tail gas treatment system.

[0005] To achieve the above technical purpose, the utility model adopts the following technical scheme:

[0006] An energy-saving and environment-friendly low-temperature methanol washing tail gas treatment system includes a methanol washing tower, the methanol washing tower is respectively connected with a CO2 product tower and an H2S concentration tower, the CO2 product tower is connected with a thermal regeneration tower, the tops of the CO2 product tower and the H2S concentration tower are both connected with a tail gas washing tower, the tail gas washing tower and the thermal regeneration tower are both connected with a tail gas heat exchanger, the tail gas heat exchanger is connected with a tail gas vent stack, and a heating coil is arranged on the outer wall of the pipeline between the tail gas heat exchanger and the tail gas vent stack.

[0007] In one or more embodiments, the middle of the methanol washing tower is connected with the top of the CO2 product tower.

[0008] In one or more embodiments, the bottom of the methanol washing tower is connected with the top of the H2S concentration tower.

[0009] In one or more embodiments, the top of the methanol washing tower is connected with a purified gas outlet through a first heat exchanger.

[0010] In one or more embodiments, the bottom of the CO2 product tower is connected to the CO2 stripping tower.

[0011] Preferably, a first low-pressure nitrogen inlet is provided at the bottom of the CO2 stripping tower.

[0012] In one or more embodiments, the top of the CO2 product tower is connected to the tail gas scrubbing tower through a first heat exchanger.

[0013] In one or more embodiments, the bottom of the CO2 product tower is connected to the middle of the H2S concentration tower.

[0014] In one or more embodiments, a second low-pressure nitrogen inlet is provided at the bottom of the H2S concentration tower, and the bottom of the H2S concentration tower is connected to the CO2 stripping tower.

[0015] In one or more embodiments, the middle of the H2S concentration tower is connected to the methanol flash tank, and the methanol flash tank is connected to the CO2 product tower.

[0016] In one or more embodiments, the top of the H2S concentration tower is connected to the tail gas scrubbing tower through a feedstock heat exchanger.

[0017] Preferably, the feedstock heat exchanger is connected to the shift gas transmission pipeline.

[0018] More preferably, the feedstock heat exchanger is connected to the bottom of the methanol scrubbing tower through a water separator.

[0019] In one or more embodiments, the bottom of the thermal regeneration tower is connected to the top of the methanol scrubbing tower.

[0020] In one or more embodiments, the tail gas heat exchanger is connected to the acid gas outlet.

[0021] The beneficial effects of the present utility model are as follows:

[0022] (1) The present utility model provides an energy-saving and environment-friendly tail gas treatment system for low-temperature methanol washing. In this system, the acid tail gas at the top of the thermal regeneration tower and the tail gas after being scrubbed by the tail gas scrubbing tower are thermally coupled at the tail gas heat exchanger, which can not only reduce the consumption of cooling water for the acid tail gas at the top of the thermal regeneration tower, achieving an energy-saving effect. At the same time, it can further increase the temperature of the tail gas. Subsequently, the temperature of the tail gas is further increased through the heating coil, so that the discharge temperature of the final tail gas is increased to above 60°C. At this time, the amount of residual CO gas in the tail gas settling to the ground will be reduced, thereby reducing environmental pollution.

[0023] (2) The purified gas generated from the top of the methanol washing tower undergoes thermal coupling with the tail gas CO2 generated from the top of the CO2 product tower at the first heat exchanger, which raises the temperature of the purified gas and further reduces the temperature of the tail gas CO2. After the temperature of the purified gas is raised, the energy consumption required for heating in the subsequent process can be reduced, and reducing the temperature of the tail gas CO2 can reduce the water consumption of the tail gas washing tower. The shifted gas to be treated undergoes thermal coupling with the tail gas H2S gas generated from the top of the H2S concentration tower at the feed exchanger, which raises the temperature of the shifted gas and reduces the temperature of the tail gas H2S gas. Raising the temperature of the shifted gas can reduce the energy consumption of the methanol washing tower, and reducing the temperature of the tail gas H2S gas can reduce the water consumption of the tail gas washing tower. Through the above two heat exchangers, the energy consumption of the system is reduced again. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The schematic diagrams forming a part of the present utility model are used to provide a further understanding of the present utility model. The schematic embodiments and descriptions thereof are used to explain the present utility model and do not unduly limit the present utility model.

[0025] Figure 1 It is a structural diagram of the energy-saving and environmental-friendly low-temperature methanol wash tail gas treatment system in Embodiment 1, where 1 - methanol washing tower, 2 - CO2 product tower, 3 - H2S concentration tower, 4 - thermal regeneration tower, 5 - CO2 stripping tower, 6 - methanol flash tank, 7 - feed heat exchanger, 8 - first heat exchanger, 9 - water separator, 10 - tail gas washing tower, 11 - tail gas heat exchanger, 12 - tail gas vent stack, 13 - acid gas outlet, 14 - heating coil, 15 - purified gas outlet. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present utility model. Unless otherwise specified, all technical and scientific terms used in the present utility model have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present utility model belongs.

[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present utility model. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] The present utility model will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations rather than limitations of the present utility model.

[0029] Embodiment 1

[0030] Reference Figure 1 Figure 1 , an energy-saving and environment-friendly tail gas treatment system for low-temperature methanol washing, includes a methanol washing tower 1, the methanol washing tower 1 is respectively connected to a CO2 product tower 2 and an H2S concentration tower 3, the CO2 product tower 2 is connected to a thermal regeneration tower 4, the tops of the CO2 product tower 2 and the H2S concentration tower 3 are both connected to a tail gas washing tower 10, the tail gas washing tower 10 and the thermal regeneration tower 4 are both connected to a tail gas heat exchanger 11, the tail gas heat exchanger 11 is connected to a tail gas vent stack 12; a heating coil 14 is arranged on the outer wall of the pipeline between the tail gas heat exchanger 11 and the tail gas vent stack 12; the tail gas heat exchanger 11 is connected to an acid gas outlet 13.

[0031] Among them, the middle of the methanol washing tower 1 is connected to the top of the CO2 product tower 2; the bottom of the methanol washing tower 1 is connected to the top of the H2S concentration tower 3; the top of the methanol washing tower 1 is connected to a purified gas outlet 15 through a first heat exchanger 8.

[0032] The bottom of the CO2 product tower 2 is connected to a CO2 stripping tower 5; a first low-pressure nitrogen inlet is arranged at the bottom of the CO2 stripping tower 5. The top of the CO2 product tower 2 is connected to the tail gas washing tower 10 through a first heat exchanger 8. The bottom of the CO2 product tower 2 is connected to the middle of the H2S concentration tower 3.

[0033] A second low-pressure nitrogen inlet is arranged at the bottom of the H2S concentration tower 3, the bottom of the H2S concentration tower 2 is connected to the CO2 stripping tower 5; the middle of the H2S concentration tower 3 is connected to a methanol flash tank 6, and the methanol flash tank 6 is connected to the bottom of the CO2 product tower 2. The top of the H2S concentration tower is connected to the tail gas washing tower 10 through a raw material heat exchanger 7; the raw material heat exchanger 7 is connected to a shift gas conveying pipeline. The raw material heat exchanger 7 is connected to the bottom of the methanol washing tower 1 through a water separator 9.

[0034] The bottom of the thermal regeneration 4 tower is connected to the top of the methanol washing tower 1.

[0035] The process flow of the present utility model:

[0036] The shifted gas feedstock undergoes thermal coupling with the acidic gas generated at the top of the H2S concentrator tower at the feedstock heat exchanger, raising the temperature of the feedstock entering the methanol scrubber tower while lowering the temperature of the acidic gas generated at the top of the H2S concentrator tower entering the tail gas scrubber tower. The heat-exchanged shifted gas feedstock enters a water separator to separate out the methanol-water mixture and then enters the bottom of the methanol scrubber tower. In the upper and lower sections of the methanol scrubber tower, lean methanol absorbs CO2 and H2S / COS in the shifted gas respectively, becoming carbon-rich methanol and sulfur-rich methanol. The scrubbed purified gas undergoes thermal coupling with the CO2 generated at the top of the CO2 product tower at the first heat exchanger, raising the temperature of the purified gas while lowering the temperature of the CO2 entering the tail gas scrubber tower.

[0037] The carbon-rich methanol in the middle section of the methanol scrubber tower enters the CO2 product tower and generates CO2 after depressurization flashing. The rich methanol from the methanol flash tank enters the bottom of the CO2 product tower to flash out CO2.

[0038] The rich methanol in the middle section of the CO2 product tower and the sulfur-rich methanol in the bottom of the methanol scrubber tower enter the upper section of the H2S concentrator tower. A large amount of CO2 is stripped from the rich methanol by low-pressure nitrogen gas at the bottom and the dissolution heat is recovered to achieve H2S concentration. To improve the stripping efficiency of the H2S concentrator tower, cold methanol is pumped out from the middle of the H2S concentrator tower by a rich methanol pump and enters the methanol flash tank.

[0039] The rich methanol from the bottom of the H2S concentrator tower enters the top of the CO2 stripper tower and is further stripped of CO2 in the rich methanol by low-pressure nitrogen gas at the bottom of the CO2 stripper tower, increasing the H2S content in the rich methanol. The mixture of CO2 and N2 returns to the H2S concentrator tower.

[0040] The rich methanol from the bottom of the CO2 stripper tower enters the thermal regeneration tower. After the rich methanol is heated, H2S, COS, and CO2 are completely desorbed from the rich methanol along with the methanol vapor. The unseparated acidic gas from the top of the thermal regeneration tower enters the tail gas heat exchanger to undergo thermal coupling with the gas from the tail gas scrubber tower, which can not only reduce the consumption of cooling water for the acidic tail gas at the top of the thermal regeneration tower, achieving an energy-saving effect. At the same time, it can further increase the temperature of the tail gas. Subsequently, the temperature of the tail gas is further increased through heating coils, raising the final tail gas emission temperature to above 60°C. At this time, the amount of residual CO gas in the tail gas settling to the ground will decrease, thereby reducing environmental pollution. The acidic gas after thermal coupling enters the subsequent process through the acidic gas outlet for separation and recovery.

[0041] The utility model provides an energy-saving and environment-friendly tail gas treatment system for low-temperature methanol washing. In this system, the acidic tail gas at the top of the thermal regeneration tower is thermally coupled with the tail gas after being washed by the tail gas washing tower at the tail gas cooler, which can not only reduce the consumption of cooling water for the acidic tail gas at the top of the thermal regeneration tower, achieving an energy-saving effect. At the same time, it can further increase the temperature of the tail gas, and then further increase the temperature of the tail gas through the heating coil, so that the final emission temperature of the tail gas is increased to above 60 °C. At this time, the amount of residual CO gas in the tail gas settling to the ground will be reduced, thus reducing the environmental pollution.

[0042] (2) The purified gas generated at the top of the methanol washing tower is thermally coupled with the tail gas CO2 generated at the top of the CO2 product tower at the first heat exchanger, which increases the temperature of the purified gas and further reduces the temperature of the tail gas CO2 at the same time; after the temperature of the purified gas is increased, the energy consumption required for subsequent heating can be reduced, and reducing the temperature of the tail gas CO2 can reduce the water consumption of the tail gas washing tower. The shift gas to be treated is thermally coupled with the tail gas H2S gas generated at the top of the H2S concentration tower at the raw material exchanger, which increases the temperature of the shift gas and reduces the temperature of the tail gas H2S gas at the same time; increasing the temperature of the shift gas can reduce the energy consumption of the methanol washing tower, and reducing the temperature of the tail gas H2S gas can reduce the water consumption of the tail gas washing tower. Through the above two heat exchangers, the energy consumption of the system is reduced again.

[0043] Finally, it should be noted that the above are only the preferred embodiments of the present utility model and are not used to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements on some of them. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included in the protection scope of the present utility model.

Claims

1. An energy-saving and environmental protection type tail gas treatment system for low-temperature methanol washing, characterized in that, It includes a methanol scrubbing column, which is respectively connected to a CO2 product column and an H2S concentration column. The CO2 product column is connected to a thermal regeneration column. The tops of the CO2 product column and the H2S concentration column are both connected to a tail gas scrubbing column. The tail gas scrubbing column and the thermal regeneration column are both connected to a tail gas heat exchanger. The tail gas heat exchanger is connected to a tail gas vent stack. A heating coil is provided on the outer wall of the pipeline between the tail gas heat exchanger and the tail gas vent stack.

2. The energy-saving and environmental protection type tail gas treatment system for low-temperature methanol washing according to claim 1, wherein The middle part of the methanol scrubbing column is connected to the top of the CO2 product column; The bottom of the methanol scrubbing column is connected to the top of the H2S concentration column.

3. The energy-saving and environment-friendly tail gas treatment system for low-temperature methanol washing according to claim 1, characterized in that, The top of the methanol scrubbing column is connected to a purified gas outlet through a first heat exchanger.

4. The energy-saving and environment-friendly tail gas treatment system for low-temperature methanol washing according to claim 1, characterized in that, The bottom of the CO2 product column is connected to a CO2 stripping column; a first low-pressure nitrogen inlet is provided at the bottom of the CO2 stripping column.

5. The energy-saving and environment-friendly tail gas treatment system for low-temperature methanol washing according to claim 1, characterized in that, The top of the CO2 product column is connected to the tail gas scrubbing column through a first heat exchanger; The bottom of the CO2 product column is connected to the middle part of the H2S concentration column.

6. The energy-saving and environment-friendly tail gas treatment system for low-temperature methanol washing according to claim 1, characterized in that, A second low-pressure nitrogen inlet is provided at the bottom of the H2S concentration column, and the bottom of the H2S concentration column is connected to the CO2 stripping column.

7. The energy-saving and environment-friendly tail gas treatment system for low-temperature methanol washing according to claim 1, characterized in that The middle part of the H2S concentration column is connected to a methanol flash tank, and the methanol flash tank is connected to the CO2 product column.

8. The energy-saving and environment-friendly tail gas treatment system for low-temperature methanol washing according to claim 1, wherein The top of the H2S concentration column is connected to the tail gas scrubbing column through a feed heat exchanger; the feed heat exchanger is connected to a shift gas pipeline; the feed heat exchanger is connected to the bottom of the methanol scrubbing column through a water separator.

9. The energy-saving and environment-friendly tail gas treatment system for low-temperature methanol washing according to claim 1, characterized in that, The bottom of the thermal regeneration column is connected to the top of the methanol scrubbing column.

10. The energy-saving and environmental-friendly tail gas treatment system for low-temperature methanol washing according to claim 1, characterized in that, The tail gas heat exchanger is connected to an acidic gas outlet.

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