CN-120132560-B - Method and system for recycling low-temperature methanol washing exhaust gas

CN120132560BCN 120132560 BCN120132560 BCN 120132560BCN-120132560-B

Abstract

The invention belongs to the technical field of coal chemical industry and low-temperature methanol washing, and particularly relates to a method and a system for recycling low-temperature methanol washing exhaust gas, wherein the low-temperature methanol washing exhaust gas recycling system comprises a first step system and a second step system, and the first step system comprises a methanol solution mass transfer separation treatment unit and an effective gas pressurizing recovery unit; the second step system comprises a gas mixing buffer unit, a heat storage incineration unit and an energy recycling unit, wherein the first step system is used for carrying out three-time depressurization flash evaporation on the methanol solution, so that effective gas in the methanol solution is resolved as far as possible, the concentration of methanol in liquid obtained after the three-time depressurization flash evaporation is increased, and the recycling of the methanol is facilitated.

Inventors

LIU YONGJIAN
XU DEYOU
Zhang Cunchang
MA JUN
XUE JIAO
XIE YAQI
ZHONG TIE
LI QIANG
DONG ZHILI
MA XIAOLI
NING YANAN
WU BIAO
DENG YONGBIN
WANG ERCHENG
ZHANG GUOLIANG
ZHANG YONGFENG
ZHANG LEI
LI ZHICHAO
YU MINGCHENG

Assignees

内蒙古大唐国际克什克腾煤制天然气有限责任公司

Dates

Publication Date: 20260508
Application Date: 20250410

Claims (10)

1. The low-temperature methanol washing exhaust gas recycling system is characterized by comprising a first ladder system and a second ladder system, wherein: the first step system comprises a methanol solution mass transfer separation treatment unit and an effective gas pressurization recovery unit; The methanol solution mass transfer separation treatment unit comprises a flash tower and mass transfer separation equipment, wherein the flash tower comprises a first flash tower section and a second flash tower section arranged at the upper part of the first flash tower section, wherein the input end of the first flash tower section is communicated with a low-temperature methanol washing device through an external pipeline and is used for introducing the methanol solution of the low-temperature methanol washing device into the first flash tower section, and the first flash tower section is used for carrying out depressurization flash evaporation on the methanol solution to generate a first flash liquid and flash gas; In addition, the input end of the mass transfer separation device is communicated with the liquid phase output end of one section of the flash tower through a first methanol solution pipeline and is used for introducing the first flash liquid into the mass transfer separation device to perform depressurization flash evaporation again to obtain a second flash liquid and a first original gas, on the basis, the gas phase output end of the mass transfer separation device is provided with a first flash gas pipeline, the device is used for leading the first original gas out of the mass transfer separation equipment, the liquid phase output end of the mass transfer separation equipment is communicated to the second section of the flash evaporation tower through a second methanol solution pipeline, the second flash evaporation liquid is introduced into the second section of the flash evaporation tower to continue depressurization flash evaporation, and a third flash evaporation liquid and the second original gas are generated; The efficient gas pressurizing and recycling unit comprises a multistage compressor, the multistage compressor comprises a low-pressure section input end and a high-pressure section input end, wherein the low-pressure section input end of the multistage compressor is communicated with the first flash gas pipeline and is used for receiving the first original gas into the multistage compressor, the high-pressure input end of the multistage compressor is communicated with a gas phase output end of one section of the flash tower through a second flash gas pipeline and is used for receiving the flash gas into the multistage compressor, and the first original gas and the flash gas are led out to a low-temperature methanol washing high-pressure area system through a third flash gas pipeline after being pressurized in the multistage compressor; The second step system comprises a gas mixing buffer unit, a heat storage incineration unit and an energy recycling unit; The gas mixing buffer unit comprises a CO 2 washing tower and a buffer tank, wherein the CO 2 washing tower is used for absorbing methanol, the input end of the CO 2 washing tower is communicated with the gas phase output end of the second section of the flash tower through a fourth flash gas pipeline and is used for receiving second original gas, the output end of the CO 2 washing tower is communicated with the input end of the buffer tank through a CO 2 exhaust gas pipeline, so that washing gas obtained after the second original gas is washed by the CO 2 washing tower is introduced into the buffer tank, and on the basis, the gas mixing buffer unit further comprises an oxygen supplementing component and a recycle wind component, and the oxygen supplementing component and the recycle wind component are respectively communicated to the CO 2 exhaust gas pipeline and are used for respectively providing oxygen supplementing wind and recycle wind for the CO 2 exhaust gas pipeline, so that the oxygen supplementing wind, the recycle wind and the washing gas are mixed to form raw material gas and then enter the buffer tank for buffer storage; The heat storage incineration unit comprises a first heat storage incinerator and a second heat storage incinerator, wherein a first air inlet pipeline is arranged at the input end of the first heat storage incinerator, a second air inlet pipeline is arranged at the input end of the second heat storage incinerator, the first air inlet pipeline and the second air inlet pipeline are connected in parallel and then are communicated with the output end of the buffer tank, so that raw gas in the buffer tank enters the first heat storage incinerator and the second heat storage incinerator through the first air inlet pipeline and the second air inlet pipeline respectively to carry out high-temperature oxidation combustion to generate high-temperature purified smoke, in addition, a first high-temperature smoke pipe is arranged at the output end of the first heat storage incinerator, and a second high-temperature smoke pipe is arranged at the output end of the second heat storage incinerator and is used for discharging the high-temperature purified smoke; The energy recycling unit comprises a medium-pressure boiler, the medium-pressure boiler comprises a flue gas side and a water supply side, the flue gas side of the medium-pressure boiler is communicated with a first high-temperature flue gas pipe and a second high-temperature flue gas pipe and is used for receiving part of high-temperature purified flue gas generated by the first heat storage incinerator and the second heat storage incinerator, the water supply side of the medium-pressure boiler is connected with an external water source through a water supply pipeline and is used for supplying water to the water supply side of the medium-pressure boiler, the medium-pressure boiler is used for heating water on the water supply side of the medium-pressure boiler through the high-temperature purified flue gas on the flue gas side to generate medium-pressure superheated steam, the medium-pressure superheated steam is conveyed to an outer pipe network through a superheated steam pipeline to be recycled, in addition, an output end of the medium-pressure boiler is further provided with a purified flue gas pipeline, the end part of the purified flue gas pipeline is connected with a discharge cylinder, the residual flue gas after the high-temperature purified flue gas is guided into the discharge cylinder through the purified flue gas pipeline to be discharged, and CEMS analyzer is further arranged on the discharge cylinder for analyzing the content of each gas in the purified flue gas.
2. The recycling system of low-temperature methanol washing exhaust gas is characterized in that in the methanol solution mass transfer separation treatment unit, the air pressure in one section of the flash tower is 1.0-1.1Mpa, and the components of flash gas obtained by reducing pressure and flash evaporation of the methanol solution in one section of the flash tower are calculated as volume fractions CH 4 ：25.67%、H 2 ：25.63%、CO 2 ：28.38%、CO：16.38%、C 2 H 6 ：0.09%、C 2 H 4 ：0.13%、C 3 H 8 ：0.1%、N 2 ：0.74%; The air pressure in the mass transfer separation equipment is 0.36-0.44Mpa, and the component of the first original gas generated by depressurization flash evaporation is calculated as volume fraction CH 4 ：11.53%、H 2 ：0.57%、CO 2 ：80.62%、CO：2.39%、C 2 H 6 ：2.06%、C 2 H 4 ：0.03%、C 3 H 8 ：0.11%、N 2 ：2.01%; The air pressure in the second section of the flash tower is 0.08Mpa, and the components of the second original gas generated by the depressurization flash distillation are calculated as volume fractions CO 2 ：93.96%、CH 4 ：2.03%、CO：0.21%、N 2 ：1.29%、C 2 H 6 ：1.62%、C 3 H 8 ：0.11%.
3. The recycling system of low-temperature methanol washing exhaust gas of claim 2, wherein in the methanol solution mass transfer separation treatment unit, the second methanol solution pipeline is a three-way pipeline, and is also communicated with the first methanol solution pipeline on the basis that the second methanol solution pipeline is respectively communicated with mass transfer separation equipment and a flash tower; On the basis, a first control valve and a second control valve are further arranged on the second methanol solution pipeline, meanwhile, the first control valve is positioned between a three-way joint of the second methanol solution pipeline and a joint position of the second methanol solution pipeline and the first methanol solution pipeline, the second control valve is positioned between a three-way joint of the second methanol solution pipeline and a liquid phase output end of the mass transfer separation device, in addition, a third control valve is arranged on the first methanol solution pipeline, and meanwhile, the third control valve is positioned between an input end of the mass transfer separation device and a joint position of the first methanol solution pipeline and the second methanol solution pipeline; The mass transfer separation equipment is also provided with a flash gas emptying pipeline which is used for decompressing the mass transfer separation equipment when the mass transfer separation equipment has an abnormal working condition of overpressure operation and the system is stopped integrally; The liquid phase output end of the second section of the flash tower is also connected with an external pipeline, and the third flash liquid is output to subsequent process equipment through the external pipeline.
4. The recycling system of low-temperature methanol washing exhaust gas of claim 3, wherein in the effective gas pressurizing and recycling unit, the multistage compressor pressurizes the first original gas and flash gas in the effective gas pressurizing and recycling unit to 3.6Mpa, and then leads the first original gas and flash gas out to a low-temperature methanol washing high-pressure area system through a third flash gas pipeline.
5. The recycling system of low-temperature methanol washing exhaust gas of claim 4, wherein in the gas mixing buffer unit, the oxygen supplementing air component comprises an oxygen supplementing fan and a first oxygen supplementing air pipeline, the first oxygen supplementing air pipeline is used for communicating the oxygen supplementing fan with a CO 2 exhaust gas pipeline and introducing oxygen supplementing air provided by the oxygen supplementing fan into the CO 2 exhaust gas pipeline, and in addition, a first valve is arranged on the first oxygen supplementing air pipeline and used for controlling the opening and closing states of the first oxygen supplementing air pipeline; The recycle wind assembly comprises a recycle fan and a first recycle line, wherein the first recycle line is used for communicating the recycle fan with the CO 2 exhaust gas line and introducing recycle wind provided by the recycle fan into the CO 2 exhaust gas line; The second original gas is mixed with the washing gas obtained after washing by the CO 2 washing tower to form raw gas, and then the raw gas is introduced into the buffer tank for buffer storage, on the basis, an LEL detector is further arranged on the CO 2 exhaust pipeline, and the LEL detector is positioned at the downstream of the joint position of the CO 2 exhaust pipeline, the first oxygen supplementing pipeline and the first recycling pipeline and is used for detecting the content of combustible gas in the raw gas, and the combustible gas is the sum of CH 4 、H 2 、CO、C 2 H 6 、C 2 H 4 、C 3 H 8 .
6. The recycling system of low-temperature methanol washing exhaust gas is characterized in that in the heat storage incineration unit, the first heat storage incinerator and the second heat storage incinerator are arranged in parallel, the temperature of high-temperature oxidation combustion of raw material gas in the first heat storage incinerator and the second heat storage incinerator is 900-1000 ℃, CO 2 and H 2 O are generated by the high-temperature oxidation combustion of the raw material gas to form high-temperature purified flue gas, heat energy is released, in addition, a first air inlet valve is arranged on the first air inlet pipe, a second air inlet valve is arranged on the second air inlet pipe, and the first high-temperature flue gas pipe and the second high-temperature flue gas pipe are communicated with the flue gas side of the medium-pressure boiler.
7. The recycling system of low-temperature methanol washing exhaust gas is characterized by further comprising an auxiliary unit, wherein the auxiliary unit comprises a purge fan, the output end of the purge fan is connected with a first purge air pipeline and a second purge air pipeline through a three-way pipeline, the first purge air pipeline is communicated with the first heat storage incinerator, the second purge air pipeline is communicated with the second heat storage incinerator and is used for providing purge air for the first heat storage incinerator and the second heat storage incinerator respectively, a first on-off valve is arranged on the first purge air pipeline, and a second on-off valve is arranged on the second purge air pipeline and is used for controlling on-off of the first purge air pipeline and the second purge air pipeline respectively.
8. The recycling system of low-temperature methanol washing and discharging gas is characterized in that the auxiliary unit further comprises a second oxygen supplementing air pipeline and a third oxygen supplementing air pipeline, one ends of the second oxygen supplementing air pipeline and the third oxygen supplementing air pipeline are connected in parallel and then communicated with the oxygen supplementing fan, the other end of the second oxygen supplementing air pipeline is communicated with the first air inlet pipeline, the other end of the third oxygen supplementing air pipeline is communicated with the second air inlet pipeline, and the recycling system is used for providing oxygen supplementing air for the first heat accumulating incinerator and the second heat accumulating incinerator and replacing air in the first heat accumulating incinerator and the second heat accumulating incinerator, in addition, a second valve is arranged on the second oxygen supplementing air pipeline, a third valve is arranged on the third oxygen supplementing air pipeline, and the second valve and the third valve are used for respectively controlling the on-off of the second oxygen supplementing air pipeline and the third oxygen supplementing air pipeline; In addition, the auxiliary unit further comprises a straight-line pipeline, one end of the straight-line pipeline is communicated with the output end of the buffer tank, the other end of the straight-line pipeline is communicated with the discharge cylinder on the basis that the straight-line pipeline is communicated with the first air inlet pipeline and the second air inlet pipeline which are arranged in parallel, and when the LEL detector detects that the content of combustible gas in the raw gas exceeds 25% of the lowest explosion limit, the raw gas is led into the discharge cylinder from the buffer tank to be directly discharged; on this basis, the auxiliary unit still includes the first gas-out pipeline with the output intercommunication of first heat accumulation burning furnace, with the second gas-out pipeline of the output intercommunication of second heat accumulation burning furnace, just first gas-out pipeline, second gas-out pipeline all communicate with the emission section of thick bamboo for with the partial high temperature purification flue gas after the reaction in first heat accumulation burning furnace, the second heat accumulation burning furnace respectively discharges.
9. A method for recycling low-temperature methanol washing exhaust gas, which adopts the low-temperature methanol washing exhaust gas recycling system as set forth in any one of claims 1-8, and is characterized by comprising the following steps: s1, carrying out flash evaporation analysis on effective gas on a methanol solution used in a low-temperature methanol washing process, and recycling the effective gas obtained by the flash evaporation analysis; Introducing methanol solution used in a low-temperature methanol washing process into a first section of a flash tower through an external pipeline, performing depressurization flash evaporation with the air pressure of 1.0-1.1Mpa to generate first flash liquid and flash gas, wherein the flash gas is led out of the first section of the flash tower, the first flash liquid is introduced into mass transfer separation equipment through a first methanol solution pipeline, and performs depressurization flash evaporation with the air pressure of 0.36-0.44Mpa to obtain second flash liquid and first original gas, at the moment, the first original gas is led out of the mass transfer separation equipment, the second flash liquid is introduced into a second section of the flash tower through a second methanol solution pipeline, and performs depressurization flash evaporation with the air pressure of 0.08Mpa to obtain third flash liquid and second original gas, the third flash liquid enters subsequent process equipment through the external pipeline, and the second original gas is ready to enter a second ladder system; The flash gas enters a multistage compressor through a second flash gas pipeline to be pressurized to 3.6Mpa, and is led out to a low-temperature methanol washing high-pressure zone system through a third flash gas pipeline; The first original gas enters a multistage compressor through a first flash gas pipeline to be pressurized to 3.6Mpa, and is led out to a low-temperature methanol washing high-pressure area system through a third flash gas pipeline; S2, treating a second original gas obtained after the pressure reduction flash evaporation of the second flash evaporation liquid in the second section of the flash evaporation tower to obtain a raw gas; the second original gas enters a CO 2 washing tower through a fourth flash evaporation gas pipeline to be washed to obtain washing gas, and the washing gas is mixed with oxygen supplementing air and circulating air provided by an oxygen supplementing air component and a recycling air component to form raw gas, and the raw gas is introduced into a buffer tank through a CO 2 exhaust gas pipeline to be buffered and stored; s3, after the raw material gas is subjected to high-temperature oxidation combustion treatment, recycling energy sources of the products by utilizing an energy recycling unit; The method comprises the steps of dividing raw gas in a buffer tank into two paths, enabling the raw gas to enter a first heat storage incinerator and a second heat storage incinerator through a first air inlet pipeline and a second air inlet pipeline respectively, performing high-temperature oxidation combustion to generate high-temperature purified smoke, enabling the high-temperature purified smoke to enter a smoke side of a medium-pressure boiler through a first high-temperature smoke pipe and a second high-temperature smoke pipe, and on the basis of using an external water source to supply water for a water supply side of the medium-pressure boiler, enabling water on the water supply side of the medium-pressure boiler heated by the high-temperature purified smoke to generate medium-pressure superheated steam with the pressure of 4.8Mpa and the temperature of 420 ℃, and enabling the medium-pressure superheated steam to be sent to an outer pipe network through a superheated steam pipeline for utilization.
10. The method for recycling low-temperature methanol washing exhaust gas according to claim 9, wherein in the step S2, the washing gas, the oxygen supplementing air and the circulating air are mixed with each other to form raw material gas, when the content of combustible gas in the raw material gas detected at the position of the raw material gas passing through the LEL detector in the CO 2 exhaust gas pipeline exceeds 25% of the lowest explosion limit, the raw material gas is introduced into the exhaust cylinder from the buffer tank to be directly exhausted, and when the content of combustible gas in the raw material gas detected at the position of the raw material gas passing through the LEL detector in the CO 2 exhaust gas pipeline does not exceed 25% of the lowest explosion limit, the raw material gas is introduced into the heat storage incineration unit from the buffer tank to be subjected to high-temperature oxidation combustion treatment.

Description

Method and system for recycling low-temperature methanol washing exhaust gas Technical Field The invention belongs to the technical fields of coal chemical industry and low-temperature methanol washing, and particularly relates to a method and a system for recycling low-temperature methanol washing exhaust gas. Background How to reduce methane and volatile organic compounds in carbon dioxide exhaust gas in the field of coal-to-natural gasification industry and realize recovery and treatment of VOCs are currently important problems. In the coal chemical industry, the low-temperature methanol washing gas purification technology is widely applied in the field of gas purification due to the characteristics of high purification degree, high automation degree, low process energy consumption and the like, is a preferred process for gas purification in the coal chemical industry, but in the process of gas purification, methanol absorbs and removes acid gases such as carbon dioxide, hydrogen sulfide and the like, and simultaneously absorbs a certain amount of effective gases such as hydrogen, carbon monoxide, methane and the like, and the effective gases are entrained in tail gas to be discharged into the atmosphere when the methanol is regenerated, so that the effective gases are consumed, and the atmospheric environment is polluted, and the tail gas at the place is the low-temperature methanol washing gas. Disclosure of Invention In view of the above, the invention aims to provide a recycling system for low-temperature methanol washing exhaust gas, which aims to solve the problem of environmental pollution caused by direct discharge of the low-temperature methanol washing exhaust gas and also to recover and reuse effective gas in the exhaust gas. In addition, another object of the present invention is to provide a method for recycling low-temperature methanol washing effluent gas, which enables the gas discharge to reach the standard after the recycling treatment of the effective gas in the low-temperature methanol washing effluent gas on the basis of the recycling system of the effective gas in the low-temperature methanol washing effluent gas. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a low-temperature methanol washing exhaust gas recycling system comprises a first ladder system and a second ladder system, wherein: the first step system comprises a methanol solution mass transfer separation treatment unit and an effective gas pressurization recovery unit; The methanol solution mass transfer separation treatment unit comprises a flash tower and mass transfer separation equipment, wherein the flash tower comprises a first flash tower section and a second flash tower section arranged at the upper part of the first flash tower section, wherein the input end of the first flash tower section is communicated with a low-temperature methanol washing device through an external pipeline and is used for introducing the methanol solution of the low-temperature methanol washing device into the first flash tower section, and the first flash tower section is used for carrying out depressurization flash evaporation on the methanol solution to generate a first flash liquid and flash gas; In addition, the input end of the mass transfer separation device is communicated with the liquid phase output end of one section of the flash tower through a first methanol solution pipeline and is used for introducing the first flash liquid into the mass transfer separation device to perform depressurization flash evaporation again to obtain a second flash liquid and a first original gas, on the basis, the gas phase output end of the mass transfer separation device is provided with a first flash gas pipeline, the device is used for leading the first original gas out of the mass transfer separation equipment, the liquid phase output end of the mass transfer separation equipment is communicated to the second section of the flash evaporation tower through a second methanol solution pipeline, the second flash evaporation liquid is introduced into the second section of the flash evaporation tower to continue depressurization flash evaporation, and a third flash evaporation liquid and the second original gas are generated; The efficient gas pressurizing and recycling unit comprises a multistage compressor, the multistage compressor comprises a low-pressure section input end and a high-pressure section input end, wherein the low-pressure section input end of the multistage compressor is communicated with the first flash gas pipeline and is used for receiving the first original gas into the multistage compressor, the high-pressure input end of the multistage compressor is communicated with a gas phase output end of one section of the flash tower through a second flash gas pipeline and is used for receiving the flash gas into the multistage compressor, and the first original gas and the flash gas