Method and system for resource utilization of low-temperature methanol washing exhaust gas

Abstract

The present application belongs to the technical field of coal chemical industry and low-temperature methanol washing, and particularly relates to a method and system for resource utilization of low-temperature methanol washing exhaust gas, the system comprising a first ladder system and a second ladder system, wherein the first ladder system comprises a methanol solution mass transfer separation treatment unit and an effective gas pressurization recovery unit; the second ladder system comprises a gas mixing buffer unit, a heat accumulation incineration unit and an energy recovery and utilization unit; the present application uses the first ladder system to perform three pressure reduction flashings on the methanol solution, so that the effective gas in the methanol solution is as much as possible to be resolved out, and the concentration of methanol in the liquid obtained after the three pressure reduction flashings is increased, which is beneficial to the recycling of methanol; in addition, the present application uses the heat accumulation incineration unit in the second ladder system to perform high-temperature oxidative combustion on the raw material gas obtained by mixing the second raw gas with the oxygen-supplemented air and the circulating air, and the heat energy of the obtained gas is used for heat exchange.

Description

Technical Field

[0001] This invention belongs to the field of coal chemical industry and low-temperature methanol washing technology, specifically relating to a method and system for the resource utilization of low-temperature methanol washing exhaust gas. Background Technology

[0002] How to reduce methane and volatile organic compounds in carbon dioxide emissions and achieve VOCs recovery and treatment in the coal-to-natural gas chemical industry is an important current issue.

[0003] In the coal chemical industry, low-temperature methanol washing gas purification technology is widely used in the field of gas purification due to its high purification level, high degree of automation and low process energy consumption. It is the preferred process for gas purification in the coal chemical industry. However, during the gas purification process, while methanol absorbs and removes acidic gases such as carbon dioxide and hydrogen sulfide, it also absorbs a certain amount of effective gases such as hydrogen, carbon monoxide and methane. These effective gases will be carried into the atmosphere in the tail gas during methanol regeneration. While losing effective gases, it also pollutes the atmospheric environment. The tail gas at this point is the low-temperature methanol washing emission gas. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a low-temperature methanol wash exhaust gas resource utilization system, which aims to solve the problem of environmental pollution caused by the direct emission of low-temperature methanol wash exhaust gas, and also takes into account the recovery and reuse of effective gases in the exhaust gas.

[0005] In addition, another objective of the present invention is to provide a method for the resource utilization of low-temperature methanol wash exhaust gas. Based on the effective gas recovery and utilization system in low-temperature methanol wash exhaust gas, the effective gas in the low-temperature methanol wash exhaust gas is recovered and utilized, and the gas emission meets the standards.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A low-temperature methanol washing exhaust gas resource utilization system includes: a first-stage system and a second-stage system, wherein:

[0008] The first-stage system includes a methanol solution mass transfer and separation processing unit and an effective gas pressurization and recovery unit.

[0009] A methanol solution mass transfer and separation processing unit includes a flash tower and a mass transfer and separation device. The flash tower includes a first flash tower section and a second flash tower section located above the first flash tower section. The input end of the first flash tower section is connected to a low-temperature methanol washing device via an external pipeline to introduce the methanol solution from the low-temperature methanol washing device into the first flash tower section. The first flash tower section performs depressurization flash evaporation on the methanol solution to generate a first flash liquid and a flash vapor.

[0010] Furthermore, the input end of the mass transfer separation device is connected to the liquid phase output end of the first stage of the flash tower via a first methanol solution pipeline, which is used to pass the first flash liquid into the mass transfer separation device for depressurized flash evaporation again to obtain the second flash liquid and the first original gas. On this basis, the gas phase output end of the mass transfer separation device is provided with a first flash vapor pipeline, which is used to exit the first original gas from the mass transfer separation device. The liquid phase output end of the mass transfer separation device is connected to the second stage of the flash tower via a second methanol solution pipeline, which is used to pass the second flash liquid into the second stage of the flash tower for depressurized flash evaporation to generate the third flash liquid and the second original gas.

[0011] An effective gas pressurization and recovery unit includes a multi-stage compressor. The multi-stage compressor includes a low-pressure section input terminal and a high-pressure section input terminal. The low-pressure section input terminal of the multi-stage compressor is connected to the first flash vapor pipeline for receiving the first raw gas into the multi-stage compressor. The high-pressure input terminal of the multi-stage compressor is connected to the gas phase output terminal of a section of the flash tower through a second flash vapor pipeline for receiving flash gas into the multi-stage compressor. After being pressurized in the multi-stage compressor, the first raw gas and flash gas are discharged to the low-temperature methanol wash high-pressure zone system through a third flash vapor pipeline.

[0012] The second-stage system includes a gas mixing and buffer unit, a regenerative thermal combustion unit, and an energy recovery and utilization unit.

[0013] A gas mixing and buffer unit includes a CO2 scrubbing tower and a buffer tank. The input end of the CO2 scrubbing tower is connected to the gas phase output end of the second stage of the flash tower via a fourth flash vapor pipeline to receive the second raw gas. The output end of the CO2 scrubbing tower and the input end of the buffer tank are connected via a CO2 exhaust gas pipeline, so that the scrubbing gas obtained after the second raw gas is scrubbed by the CO2 scrubbing tower is introduced into the buffer tank. In addition, the gas mixing unit also includes an oxygen replenishment air assembly and a recirculation air assembly, which are respectively connected to the CO2 exhaust gas pipeline to provide oxygen replenishment air and recirculation air to the CO2 exhaust gas pipeline. The oxygen replenishment air, recirculation air and scrubbing gas are mixed to form raw gas, which is then buffered and stored in the buffer tank.

[0014] The regenerative thermal oxidizer unit includes a first regenerative thermal oxidizer and a second regenerative thermal oxidizer. The input ends of the first and second regenerative thermal oxidizers are respectively provided with a first air inlet pipeline and a second air inlet pipeline. The first and second air inlet pipelines are connected in parallel and connected to the output end of the buffer tank. The raw material gas in the buffer tank is divided into two paths and enters the first and second regenerative thermal oxidizers through the first and second air inlet pipelines respectively for high-temperature oxidation and combustion to generate high-temperature purified flue gas. In addition, the output ends of the first and second regenerative thermal oxidizers are respectively provided with a first high-temperature flue gas pipe and a second high-temperature flue gas pipe for discharging the high-temperature purified flue gas.

[0015] An energy recovery and utilization unit includes a medium-pressure boiler, which comprises a flue gas side and a water supply side. The flue gas side of the medium-pressure boiler is connected to a first high-temperature flue gas pipe and a second high-temperature flue gas pipe, and is used to receive part of the high-temperature purified flue gas generated by the first and second regenerative thermal oxidizers. The water supply side of the medium-pressure boiler is connected to an external water source through a water supply pipeline, and the external water source supplies water to the water supply side of the medium-pressure boiler. The medium-pressure boiler heats the water on the water supply side with the high-temperature purified flue gas on the flue gas side to generate medium-pressure superheated steam, and sends the medium-pressure superheated steam to an external pipeline network for recovery and utilization through a superheated steam pipeline. In addition, the output end of the medium-pressure boiler is also equipped with a purified flue gas pipeline, and the end of the purified flue gas pipeline is connected to an exhaust stack. The remaining flue gas after the high-temperature purified flue gas in the medium-pressure boiler heats the water is the purified flue gas. The purified flue gas is introduced into the exhaust stack through the purified flue gas pipeline for discharge. The exhaust stack is also equipped with a CEMS analyzer for analyzing the content of various gases in the purified flue gas.

[0016] Preferably, in the methanol solution mass transfer and separation processing unit, the gas pressure in the first stage of the flash tower is 1.0-1.1 MPa, and the composition of the flash gas obtained by depressurizing and flashing the methanol solution in the first stage of the flash tower, in volume fractions, is CH4: 25.67%, H2: 25.63%, CO2: 28.38%, CO: 16.38%, C2H6: 0.09%, C2H4: 0.13%, C3H8: 0.1%, N2: 0.74%.

[0017] The gas pressure in the mass transfer separation device is 0.36-0.44 MPa, and the composition of the first raw gas produced by depressurization flash evaporation, by volume fraction, is CH4: 11.53%, H2: 0.57%, CO2: 80.62%, CO: 2.39%, C2H6: 2.06%, C2H4: 0.03%, C3H8: 0.11%, N2: 2.01%.

[0018] The pressure in the second stage of the flash tower is 0.08 MPa, and the composition of the second original gas produced by the depressurization flash evaporation is as follows (by volume fraction): CO2: 93.96%, CH4: 2.03%, CO: 0.21%, N2: 1.29%, C2H6: 1.62%, C3H8: 0.11%.

[0019] Preferably, in the methanol solution mass transfer and separation processing unit, the second methanol solution pipeline is a three-way pipeline, and in addition to being connected to the mass transfer and separation equipment and the two sections of the flash tower, the second methanol solution pipeline is also connected to the first methanol solution pipeline.

[0020] Based on this, the second methanol solution pipeline is also equipped with a first control valve and a second control valve. At the same time, the first control valve is located between the tee joint of the second methanol solution pipeline and the joint between the second methanol solution pipeline and the first methanol solution pipeline. The second control valve is located between the tee joint of the second methanol solution pipeline and the liquid phase output end of the mass transfer separation device. In addition, the first methanol solution pipeline is equipped with a third control valve, which is located between the input end of the mass transfer separation device and the joint between the first methanol solution pipeline and the second methanol solution pipeline.

[0021] The mass transfer separation equipment is also equipped with a flash vapor venting pipeline, which is used to depressurize the mass transfer separation equipment when it experiences an abnormal overpressure operation or when the entire system shuts down.

[0022] The liquid output end of the second section of the flash tower is also connected to an external pipeline, through which the third flash liquid is output to the subsequent process equipment.

[0023] Preferably, in the effective gas pressurization and recovery unit, the multi-stage compressor pressurizes its internal first raw gas and flash vapor to 3.6 MPa and then exports them to the low-temperature methanol wash high-pressure zone system through the third flash vapor pipeline.

[0024] Preferably, in the gas mixing buffer unit, the oxygen replenishment air assembly includes an oxygen replenishment fan and a first oxygen replenishment air pipeline. The first oxygen replenishment air pipeline is used to connect the oxygen replenishment fan with the CO2 exhaust gas pipeline and to introduce the oxygen replenishment air provided by the oxygen replenishment fan into the CO2 exhaust gas pipeline. In addition, the first oxygen replenishment air pipeline is also provided with a first valve to control the opening and closing state of the first oxygen replenishment air pipeline.

[0025] The recirculation air assembly includes a recirculation fan and a first recirculation pipeline. The first recirculation pipeline is used to connect the recirculation fan to the CO2 emission pipeline and to introduce the recirculation air provided by the recirculation fan into the CO2 emission pipeline.

[0026] The second raw gas, after being washed by the CO2 scrubbing tower, is mixed with oxygen-supplementing air and circulating air to form raw material gas, which is then passed into a buffer tank for buffer storage. In addition, an LEL detector is installed on the CO2 emission gas pipeline, and the LEL detector is located downstream of the junction of the CO2 emission gas pipeline and the first oxygen-supplementing air pipeline and the first recirculation pipeline. It is used to detect the content of combustible gas in the raw material gas, which is the sum of CH4, H2, CO, C2H6, C2H4 and C3H8.

[0027] Preferably, in the regenerative thermal combustion unit, the first regenerative thermal combustion furnace and the second regenerative thermal combustion furnace are arranged in parallel. The temperature for high-temperature oxidation and combustion of the raw gas in the first and second regenerative thermal combustion furnaces is 900-1000℃. The high-temperature oxidation and combustion of the raw gas generates CO2 and H2O to form high-temperature purified flue gas and releases heat energy. In addition, the first and second air inlet pipelines are respectively equipped with a first air inlet valve and a second air inlet valve to control the opening and closing of the first and second air inlet pipelines respectively. The first high-temperature flue gas pipe and the second high-temperature flue gas pipe are connected to the flue gas side of the medium-pressure boiler.

[0028] Preferably, the low-temperature methanol wash exhaust gas resource utilization system further includes an auxiliary unit, which includes a purge fan. The output end of the purge fan is connected to a first purge air pipeline and a second purge air pipeline via a three-way pipeline. The first purge air pipeline is connected to the first regenerative thermal incinerator, and the second purge air pipeline is connected to the second regenerative thermal incinerator, providing purge air to the first and second regenerative thermal incinerators respectively. In addition, a first on-off valve and a second on-off valve are respectively installed on the first and second purge air pipelines to control the on-off state of the first and second purge air pipelines respectively.

[0029] Preferably, the auxiliary unit further includes a second oxygen supply air duct and a third oxygen supply air duct. One end of the second oxygen supply air duct and the third oxygen supply air duct are connected in parallel to the oxygen supply fan, and the other end is connected to the first air inlet duct and the second air inlet duct, respectively. They are used to provide oxygen supply air to the first regenerative thermal oxidizer and the second regenerative thermal oxidizer and to replace the air in the first regenerative thermal oxidizer and the second regenerative thermal oxidizer. In addition, a second valve is provided on the second oxygen supply air duct and a third valve is provided on the third oxygen supply air duct. The second valve and the third valve are used to control the opening and closing of the second oxygen supply air duct and the third oxygen supply air duct, respectively.

[0030] In addition, the auxiliary unit also includes a direct discharge pipeline. The direct discharge pipeline is connected to the first and second air inlet pipelines arranged in parallel. One end of the direct discharge pipeline is connected to the output end of the buffer tank, and the other end is connected to the discharge cylinder. When the LEL detector detects that the content of combustible gas in the raw material gas exceeds 25% of the minimum explosion limit, the raw material gas is directly discharged from the buffer tank into the discharge cylinder.

[0031] Based on this, the auxiliary unit also includes a first gas outlet pipeline and a second gas outlet pipeline that are respectively connected to the output ends of the first regenerative thermal incinerator and the second regenerative thermal incinerator, and both the first gas outlet pipeline and the second gas outlet pipeline are connected to the discharge stack, for discharging part of the high-temperature purified flue gas after reaction in the first regenerative thermal incinerator and the second regenerative thermal incinerator, respectively.

[0032] Furthermore, the present invention also provides a method for the resource utilization of low-temperature methanol wash exhaust gas, applied to the aforementioned low-temperature methanol wash exhaust gas resource utilization system, comprising the following steps:

[0033] S1: Flash evaporation of the methanol solution after the low-temperature methanol washing process is performed to remove the effective gas, and the effective gas obtained from the flash evaporation is recovered and reused.

[0034] In this process, the methanol solution used in the low-temperature methanol washing process is fed into the first stage of a flash tower through an external pipeline and undergoes depressurization flash evaporation at a pressure of 1.0-1.1 MPa to produce a first flash liquid and a flash gas. The flash gas is discharged from the first stage of the flash tower, while the first flash liquid is fed into a mass transfer separation device through a first methanol solution pipeline and undergoes depressurization flash evaporation at a pressure of 0.36-0.44 MPa to obtain a second flash liquid and a first raw gas. At this point, the first raw gas is discharged from the mass transfer separation device, while the second flash liquid is fed into the second stage of the flash tower through a second methanol solution pipeline and undergoes depressurization flash evaporation at a pressure of 0.08 MPa to obtain a third flash liquid and a second raw gas. The third flash liquid is fed into subsequent process equipment through an external pipeline, while the second raw gas is prepared to enter the second-stage system.

[0035] The flash vapor and the first raw gas enter the multi-stage compressor through the second flash vapor pipeline and the first flash vapor pipeline, respectively, and are pressurized to 3.6 MPa. Then, they are discharged to the low-temperature methanol wash high-pressure zone system through the third flash vapor pipeline.

[0036] S2: The second raw gas obtained after depressurizing and flashing the second flash liquid in the second stage of the flash tower is processed to obtain the raw material gas;

[0037] The second raw gas enters the CO2 scrubbing tower through the fourth flash vapor pipeline to obtain scrubbing gas. The scrubbing gas is mixed with the oxygen supplementation air and recirculation air provided by the oxygen supplementation air component and the recirculation air component to form raw material gas. The raw material gas is then passed into the buffer tank for buffer storage through the CO2 exhaust gas pipeline.

[0038] S3: After the raw gas is subjected to high-temperature oxidation and combustion treatment, the energy of the product is recovered and utilized using an energy recovery and utilization unit.

[0039] The raw gas in the buffer tank is divided into two streams and enters the first and second regenerative thermal oxidizers through the first and second inlet pipelines, respectively, to generate high-temperature purified flue gas through high-temperature oxidation combustion. The high-temperature purified flue gas enters the flue gas side of the medium-pressure boiler through the first and second high-temperature flue gas pipes. With the external water source supplying water to the water supply side of the medium-pressure boiler, the high-temperature purified flue gas heats the water on the water supply side in the medium-pressure boiler to generate medium-pressure superheated steam with a pressure of 4.8 MPa and a temperature of 420°C. The medium-pressure superheated steam is sent to the external pipeline network for utilization through the superheated steam pipeline.

[0040] Furthermore, in step S2, the scrubbing gas, oxygen-supplementing air, and circulating air are mixed to form raw material gas. When the content of combustible gas in the raw material gas exceeds 25% of the minimum explosion limit at the location where the raw material gas passes through the LEL detector in the CO2 emission gas pipeline, the raw material gas is directly discharged from the buffer tank into the emission cylinder. When the content of combustible gas in the raw material gas does not exceed 25% of the minimum limit at the location where the raw material gas passes through the LEL detector in the CO2 emission gas pipeline, the raw material gas is fed from the buffer tank into the regenerative thermal oxidative combustion unit for high-temperature oxidation combustion treatment.

[0041] The beneficial effects of this invention are as follows:

[0042] This invention adds a mass transfer separation device between the first and second flash tower sections in the first-stage system. Under the premise that the gas pressure in the first flash tower section, the mass transfer separation device, and the second flash tower section is gradually reduced, the volume fraction of each effective gas generated by the depressurized flash evaporation of the methanol solution, the first flash liquid, and the second flash liquid in the first flash tower section, the mass transfer separation device, and the second flash liquid, respectively, also tends to decrease. This allows the effective gases in the methanol solution to be extracted as much as possible, increasing the methanol concentration in the liquid obtained after three depressurized flash evaporations, which is beneficial for methanol regeneration. Furthermore, this invention uses a CO2 scrubbing tower to scrub the gas generated by the three depressurized flash evaporations in the first-stage system. Based on the raw material gas obtained by mixing oxygen-supplementing air and circulating air, the raw material gas is introduced into a regenerative thermal combustion unit for high-temperature oxidation and combustion of the effective gases, producing high-temperature purified flue gas whose gas composition meets national environmental emission standards. The heat energy accompanying the high-temperature purified flue gas is utilized through heat exchange, completing the recovery and utilization of the effective gases in the low-temperature methanol wash exhaust gas. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart illustrating the overall usage process of a low-temperature methanol washing exhaust gas resource utilization system according to the present invention.

[0045] Figure 2 This is a schematic diagram of the pipeline connections of the methanol solution mass transfer and separation processing unit in this invention;

[0046] Figure 3 This is a schematic diagram of the pipeline connections for the effective gas pressurization and recovery unit in this invention;

[0047] Figure 4 This is a schematic diagram of the pipeline connections of the gas mixing buffer unit in this invention;

[0048] Figure 5 This is a schematic diagram of the pipeline connection of the regenerative combustion unit in this invention;

[0049] Figure 6 This is a schematic diagram of the pipeline connections for the energy recovery and utilization unit in this invention;

[0050] Figure 7 This is a flowchart of the method for resource utilization of low-temperature methanol washing exhaust gas in this invention;

[0051] In the diagram: Flash tower 1, Flash tower section 1 2, Flash tower section 2 3; First methanol solution pipeline 4, Third control valve 401; Second methanol solution pipeline 5, First control valve 501, Second control valve 502; Mass transfer separation equipment 6; Flash vapor vent pipeline 7; First flash vapor pipeline 8; Second flash vapor pipeline 9; Multistage compressor 10; Third flash vapor pipeline 11; Fourth flash vapor pipeline 12; CO2 scrubber 13; CO2 emission pipeline 14; Buffer tank 15; First oxygen supply air pipeline 16, First valve 161; Oxygen supply fan 17; First air inlet pipeline 18, First air inlet valve 181; First regenerative thermal oxidizer 19; First purging air pipeline 20 201; 21; 22; 23; 24; 25; 25; 26; 27; 28; 29; 29; 20; 30; 30; 31; 31; 32; 33; 34; 35; 36; 37; 38; 39; 30; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 30; 40; 31; 32; 33; 34; 35; 36; 37; 38; 39; 30; 40; 31; 32; 33; 34; 35; 36; 37; 38; 39; 30; 41; 32; 33; 34; 35; 36; 37; 38; 39; 30; 41; 32; 33; 34; 35; 36; 37; 38; 39; 30; 41; 32; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39 ...0; 31; 32; 3 Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0054] In existing coal chemical processes, crude coal gas is subjected to low-temperature methanol washing. This process utilizes the solubility of methanol in acidic gases at temperatures ranging from -30°C to -70°C to selectively remove impurities such as H2S, COS, and CO2 from the crude coal gas, thereby improving the purity of coal-to-natural gas.

[0055] However, during the low-temperature methanol washing process, a large amount of methane and non-methane total hydrocarbons inevitably dissolve in the methanol solution. Based on this, the existing low-temperature methanol washing process separates the H2S in the methanol solution in a high-concentration form through an external H2S regeneration device, which is then used for the subsequent production of sulfur and sulfuric acid, thus realizing resource utilization. The remaining impurities such as methane, non-methane total hydrocarbons, and CO2 dissolved in the methanol solution need to be desorbed and collected or discharged through two-stage flash evaporation in a flash tower.

[0056] In fact, since methane, H2, CO, and non-methane hydrocarbons are all combustible and usable gases, and the emission of some of these effective gases into the atmosphere would harm the atmospheric environment, the existing low-temperature methanol washing process uses a flash tower to perform two-stage depressurization flash evaporation of the methanol solution. The gas after the initial flash evaporation is passed into the high-pressure zone system of the low-temperature methanol washing system for utilization, while the gas after the second flash evaporation is directly discharged. It should be noted that the aforementioned effective gases generally include CH4, H2, CO, C2H6, C2H4, C3H8, and C3H6. The gas produced by the two-stage depressurization flash evaporation in the flash tower includes not only the aforementioned effective gases but also CO2 and N2. Specifically, the gas after the initial flash evaporation has larger components such as CH4, H2, and CO, so it is passed entirely into the high-pressure zone system of the low-temperature methanol washing system; the gas after the second flash evaporation has smaller components except for CO2, and is directly discharged.

[0057] Against this backdrop, as modern society increasingly demands higher resource utilization rates and strengthens environmental protection efforts, this application provides a low-temperature methanol washing exhaust gas resource utilization system. Based on the existing flash tower, a mass transfer separation device is added to build a first-stage system. Under the premise of further flash evaporation of the methanol solution using the first-stage system, a second-stage system is used to further treat the flash gas to be emitted and recycle the effective gas inside, so that the content of each component in the final gas meets the national environmental protection emission standards, thus taking into account both environmental protection and energy utilization.

[0058] The technical solution of this application will be described in detail below with reference to the accompanying drawings.

[0059] In this technical solution, a low-temperature methanol wash exhaust gas resource utilization system is provided to recover and utilize the effective gases in the low-temperature methanol wash tail gas. The low-temperature methanol wash tail gas mentioned here is the same as the low-temperature methanol wash exhaust gas, and this concept can be understood in the same sense throughout the text. Furthermore, the components of the effective gases include methane, H2, CO, and non-methane hydrocarbons, including C2H6, C2H4, and C3H8. Figure 1 As shown, the low-temperature methanol washing exhaust gas resource utilization system includes: a first-stage system and a second-stage system, wherein: the first-stage system includes a methanol solution mass transfer separation treatment unit and an effective gas pressurization and recovery unit; the second-stage system includes a gas mixing and buffer unit, a regenerative thermal combustion unit and an energy recovery and utilization unit.

[0060] Specifically, such as Figure 2 As shown, the methanol solution mass transfer separation processing unit includes a flash tower 1 and a mass transfer separation device 6. The flash tower 1 includes a first flash tower section 2 and a second flash tower section 3 located above the first flash tower section 2. The input end of the first flash tower section 2 is connected to a low-temperature methanol washing device via an external pipeline, which is used to introduce the methanol solution after use by the low-temperature methanol washing device into the first flash tower section 2. The first flash tower section 2 performs a first depressurization flash evaporation on the methanol solution, and the pressure of the first depressurization flash evaporation is 1.0-1.1 MPa. This first depressurization flash evaporation produces a first flash liquid and a flash vapor gas. The components of the flash vapor gas, by volume fraction, are CH4: 25.67%, H2: 25.63%, CO2: 28.38%, CO: 16.38%, C2H6: 0.09%, C2H4: 0.13%, C3H8: 0.1%, and N2: 0.74%.

[0061] In addition, the input end of the mass transfer separation device 6 is connected to the liquid phase output end of the first section 2 of the flash tower via the first methanol solution pipeline 4, which is used to introduce the first flash liquid into the mass transfer separation device 6 and perform a second depressurized flash evaporation. The gas pressure of the second depressurized flash evaporation is 0.36-0.44 MPa. The second depressurized flash evaporation yields a second flash liquid and a first original gas. The components of the first original gas, in volume fractions, are CH4: 11.53%, H2: 0.57%, CO2: 80.62%, CO: 2.39%, C2H6: 2.06%, C2H4: 0.03%, C3H8: 0.11%, and N2: 2.01%.

[0062] Based on this, the gas phase output end of the mass transfer separation device 6 is equipped with a first flash vapor pipeline 8, which is used to export the first raw gas from the mass transfer separation device 6. The liquid phase output end of the mass transfer separation device 6 is connected to the second stage 3 of the flash tower through a second methanol solution pipeline 5, so that the second flash liquid is introduced into the second stage 3 of the flash tower and subjected to a third depressurization flash evaporation. The pressure of the third depressurization flash evaporation is 0.08 MPa. The third depressurization flash evaporation produces a third flash liquid and the second raw gas. The composition of the second raw gas, in volume fraction, is CO2: 93.96%, CH4: 2.03%, CO: 0.21%, N2: 1.29%, C2H6: 1.62%, and C3H8: 0.11%. In addition, the liquid phase output end of the second stage 3 of the flash tower is also connected to an external pipeline, and the third flash liquid is output to the subsequent process equipment through the external pipeline. The subsequent process equipment mentioned here refers to the regeneration and recycling part of the methanol solution in the low-temperature methanol washing process, which is also incorporated into this application as prior art.

[0063] like Figure 2-3 As shown, the effective gas pressurization and recovery unit includes a multi-stage compressor 10. The multi-stage compressor 10 includes a low-pressure input terminal and a high-pressure input terminal. The low-pressure input terminal of the multi-stage compressor 10 is connected to the first flash vapor pipeline 8 to receive the first raw gas into the multi-stage compressor 10. The high-pressure input terminal of the multi-stage compressor 10 is connected to the gas phase output terminal of the first stage 2 of the flash tower via a second flash vapor pipeline 9 to receive the flash vapor into the multi-stage compressor 10. The first raw gas and the flash vapor are pressurized to 3.6 MPa within the multi-stage compressor 10. Afterwards, the gas is led out through the third flash vapor pipeline 11 to the low-temperature methanol wash high-pressure zone system. The low-temperature methanol wash high-pressure zone system is a commonly used part of the low-temperature methanol wash process in the prior art. This application only uses the main body of the low-temperature methanol wash high-pressure zone system to indicate that the first original gas and flash vapor obtained from flash evaporation are recycled. Since the pressure of the low-temperature methanol wash high-pressure zone system in the prior art is generally 3.5 MPa, the multi-stage compressor 10 pressurizes its internal pressure to 3.6 MPa before it can be introduced into the low-temperature methanol wash high-pressure zone system.

[0064] It should be noted in this application that the flash tower 1 and the mass transfer separation device 6 mentioned in this application are both prior art.

[0065] As the core of this application, based on the above embodiments, under the premise that the gas pressure in the first stage 2 of the flash tower, the mass transfer separation device 6, and the second stage 3 of the flash tower gradually decreases, the volume fraction of each effective gas generated by the first stage 2 of the flash tower, the mass transfer separation device 6, and the second stage 3 of the flash tower respectively for depressurization flash evaporation of methanol solution, first flash liquid, and second flash liquid also tends to decrease, so that the effective gas in methanol solution is desorbed as much as possible, resulting in an increase in the concentration of methanol in the liquid obtained after three depressurization flash evaporations, which is beneficial to the regeneration and utilization of methanol. Under this premise, the first flash liquid and the second flash liquid obtained in the above embodiments are both methanol solutions with different contents of CO2, N2, and effective gases. Since this application intends to perform three depressurization flash evaporations of methanol solution using a first-step system and to further process the gas obtained from the last depressurization flash evaporation using a second-step system, the content of each component in the liquid obtained from each depressurization flash evaporation is not analyzed in detail here.

[0066] In the first-tier system of this application, such as Figure 2 As shown, the second methanol solution pipeline 5 is a three-way pipeline, and in addition to being connected to the mass transfer separation device 6 and the second stage of the flash tower 3, the second methanol solution pipeline 5 is also connected to the first methanol solution pipeline 4.

[0067] Based on this, the second methanol solution pipeline 5 is also equipped with a first control valve 501 and a second control valve 502. At the same time, the first control valve 501 is located between the three-way contact A of the second methanol solution pipeline 5 and the contact position B between the second methanol solution pipeline 5 and the first methanol solution pipeline 4. The second control valve 502 is located between the three-way contact A of the second methanol solution pipeline 5 and the liquid phase output end of the mass transfer separation device 6. In addition, the first methanol solution pipeline 4 is equipped with a third control valve 401, which is located between the input end of the mass transfer separation device 6 and the contact position B between the first methanol solution pipeline 4 and the second methanol solution pipeline 5.

[0068] Based on the above embodiments, when the mass transfer separation device 6 in the low-temperature methanol wash exhaust gas resource utilization system is operating normally, the first control valve 501 is closed, and the second control valve 502 and the third control valve 401 are open, so that the pipeline flow is: from the first stage 2 of the flash tower into the mass transfer separation device 6, and then from the mass transfer separation device 6 into the second stage 3 of the flash tower; when the mass transfer separation device 6 in the low-temperature methanol wash exhaust gas resource utilization system is under maintenance, the first control valve 501 is opened, and the second control valve 502 and the third control valve 401 are closed, so that the pipeline flow is: from the first stage 2 of the flash tower directly into the second stage 3 of the flash tower; thus, the above-mentioned control valves are set to prevent the operation of the mass transfer separation device 6 from directly affecting the overall operation of the effective gas recovery and utilization system, aiming to improve the adaptability of the first-stage system.

[0069] The mass transfer separation device 6 is also equipped with a flash vapor venting pipeline 7, which is used to depressurize the mass transfer separation device 6 when it experiences an abnormal overpressure operation or when the entire system is shut down.

[0070] Thus far, the foregoing embodiments have described the destinations and uses of the gaseous and liquid products obtained from each depressurization flash evaporation, excluding the second original gas. As another core aspect of this application, this low-temperature methanol wash exhaust gas resource utilization system will utilize a second-step system to recover and utilize the effective gases in the second original gas.

[0071] In the second-tier system of this application, such as Figure 4 As shown, the gas mixing buffer unit includes a CO2 scrubbing tower 13 and a buffer tank 15. The input end of the CO2 scrubbing tower 13 is connected to the gas phase output end of the second stage 3 of the flash tower through the fourth flash vapor pipeline 12, and is used to receive the second raw gas. The output end of the CO2 scrubbing tower 13 and the input end of the buffer tank 15 are connected through a CO2 exhaust gas pipeline 14, so that the scrubbing gas obtained after the second raw gas is scrubbed by the CO2 scrubbing tower 13 is introduced into the buffer tank 15.

[0072] In this embodiment, since the second original gas is dissolved in methanol solution before being flashed and desorbed, and a small amount of gaseous methanol will inevitably be introduced after the second original gas is flashed and desorbed, the working mechanism of CO2 scrubbing tower 13 is to absorb the methanol in the second original gas by spraying brine, and reduce the methanol content to below 50 ppm.

[0073] The gas mixing unit also includes an oxygen replenishment air assembly and a recirculation air assembly, which are respectively connected to the CO2 emission gas pipeline 14 to provide oxygen replenishment air and recirculation air to the CO2 emission gas pipeline 14. Specifically, the oxygen replenishment air assembly includes an oxygen replenishment fan 17 and a first oxygen replenishment air pipeline 16, which connects the oxygen replenishment fan 17 to the CO2 emission gas pipeline 14 and introduces the oxygen replenishment air provided by the oxygen replenishment fan 17 into the CO2 emission gas pipeline 14; the recirculation air assembly includes a recirculation fan 34 and a first recirculation air pipeline 15. Pipeline 26, the first recirculation pipeline 26 is used to connect the recirculation fan 34 and the CO2 exhaust gas pipeline 14, and to introduce the circulating air provided by the recirculation fan 34 into the CO2 exhaust gas pipeline 14; thereby, the scrubbing gas obtained after the second raw gas is scrubbed by the CO2 scrubbing tower 13, mixed with the oxygen supplementing air and the circulating air to form the raw material gas, is introduced into the buffer tank 15 for buffer storage. The specific composition of the oxygen supplementing air and the circulating air will be described in the following embodiments, and the actual pressure of the scrubbing gas in the above process is 5-12 kPa and the actual temperature is 8-10°C.

[0074] In addition, an LEL detector 39 is installed on the CO2 emission gas pipeline 14, and the LEL detector 39 is located downstream of the junction of the CO2 emission gas pipeline 14 with the first oxygen supply air pipeline 16 and the first recirculation pipeline 26. It is used to detect the content of combustible gas in the raw gas, wherein the combustible gas is the sum of the contents of CH4, H2, CO, C2H6, C2H4 and C3H8. In addition, a first valve 161 is installed on the first oxygen supply air pipeline 16 to control the opening and closing state of the first oxygen supply air pipeline 16, thereby controlling the content of oxygen supply air introduced into the CO2 emission gas pipeline 14, wherein the oxygen supply air is ordinary air in the atmosphere.

[0075] like Figure 5 As shown, the regenerative thermal oxidizer unit includes a first regenerative thermal oxidizer 19 and a second regenerative thermal oxidizer 28. The first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28 are connected in parallel. The input ends of the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28 are respectively provided with a first air inlet pipeline 18 and a second air inlet pipeline 30. The first air inlet pipeline 18 and the second air inlet pipeline 30 are connected in parallel to the output end of the buffer tank 15, so that the raw material gas in the buffer tank 15 is divided into two paths and enters the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28 through the first air inlet pipeline 18 and the second air inlet pipeline 30 respectively, where it undergoes high-temperature oxidation combustion at 900-1000℃ to generate high-temperature purified flue gas and release heat energy. Among them, the combustible gas in the raw material gas undergoes high-temperature oxidation combustion to generate CO2 and H2O, while the CO2 and N2 in the raw material gas itself do not undergo high-temperature oxidation combustion due to their stable chemical properties. It should be noted that the above The high-temperature oxidation combustion process described refers to the oxidation reaction that occurs when combustible gas is placed in a high-temperature environment of 900-1000℃ and reacts with oxygen, which is equivalent to combustion. After the reaction, the gas temperature is 800-900℃. Therefore, this application refers to the gas produced by the high-temperature oxidation combustion of the raw material gas in the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28 at 900-1000℃ as high-temperature purified flue gas. The components in the high-temperature purified flue gas, in volume fraction, are CO2: 56.73%, O2: 6.18%, N2: 36.87%, non-methane total hydrocarbons: ≤80mg / m³, and particulate matter: ≤15mg / m³. The content of these components meets the national environmental protection emission standards and can be directly emitted. Therefore, the output end of the first regenerative thermal oxidizer 19 and the output end of the second regenerative thermal oxidizer 28 are respectively provided with a first high-temperature flue gas pipe 21 and a second high-temperature flue gas pipe 31 for discharging the high-temperature purified flue gas.

[0076] In addition, the first air inlet pipeline 18 and the second air inlet pipeline 30 are respectively equipped with a first air inlet valve 181 and a second air inlet valve 301, which are used to control the opening and closing of the first air inlet pipeline 18 and the second air inlet pipeline 30 respectively, thereby specifically controlling one regenerative thermal incinerator or two regenerative thermal incinerators to be connected to the effective gas recovery and utilization system at the same time.

[0077] To prevent the waste of thermal energy from the high-temperature purified flue gas, this application also includes an energy recovery and utilization unit, such as... Figure 5-6 As shown, the energy recovery and utilization unit includes a medium-pressure boiler 22, which includes a flue gas side and a water supply side. The flue gas side of the medium-pressure boiler 22 is connected to the first high-temperature flue gas pipe 21 and the second high-temperature flue gas pipe 31, and is used to receive part of the high-temperature purified flue gas generated by the first regenerative incinerator 19 and the second regenerative incinerator 28. The water supply side of the medium-pressure boiler 22 is connected to an external water source through a water supply pipeline 38, and the external water source supplies water to the water supply side of the medium-pressure boiler 22. The medium-pressure boiler 22 heats the water on the water supply side with the high-temperature purified flue gas on the flue gas side to generate medium-pressure superheated steam, and sends the medium-pressure superheated steam to the external pipe network for recovery and utilization through the superheated steam pipeline 40.

[0078] In addition, the output end of the medium-pressure boiler 22 is also equipped with a purified flue gas pipeline 23. The end of the purified flue gas pipeline 23 is connected to a discharge stack 36. The remaining flue gas after the high-temperature purified flue gas in the medium-pressure boiler 22 heats the water is purified flue gas. The purified flue gas is introduced into the discharge stack 36 through the purified flue gas pipeline 23 for discharge. The discharge stack 36 is also equipped with a CEMS analyzer 37, which is used to analyze the content of each gas in the purified flue gas, that is, the gas component content of the aforementioned high-temperature purified flue gas.

[0079] It should be noted in this embodiment that the first regenerative thermal incinerator 19 and the second regenerative thermal incinerator 28 are multi-bed oxidation incinerators with identical structures. This is an application of existing technology. Those skilled in the art can learn about their specific structure and function through existing technical documents. Here, this application only describes their supporting facilities and pipeline connection methods.

[0080] Specifically, this low-temperature methanol wash exhaust gas resource utilization system also includes auxiliary units, such as... Figure 4-5 As shown, the auxiliary unit includes a purge fan 24. The output end of the purge fan 24 is connected to a first purge air pipeline 20 and a second purge air pipeline 33 via a three-way pipeline. The first purge air pipeline 20 is connected to the first regenerative thermal oxidizer 19, and the second purge air pipeline 33 is connected to the second regenerative thermal oxidizer 28. The purge air pipeline 20 provides purge air to the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28 respectively, preventing the accumulation of combustible gas and the risk of explosion when the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28 are in use. The specific composition of the purge air will be described in the following embodiments. In addition, a first on / off valve 201 and a second on / off valve 331 are respectively provided on the first purge air pipeline 20 and the second purge air pipeline 33, which are used to control the on / off of the first purge air pipeline 20 and the second purge air pipeline 33 respectively.

[0081] In addition, the auxiliary unit also includes a second oxygen supply air duct 25 and a third oxygen supply air duct 29. One end of the second oxygen supply air duct 25 and the third oxygen supply air duct 29 are connected in parallel to the oxygen supply fan 17, and the other end is connected to the first air intake duct 18 and the second air intake duct 30, respectively. They are used to provide oxygen supply air to the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28 and to replace the air in the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28. This is used to promote the complete combustion of combustible gas in the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28 and to maintain combustion stability. In addition, the second oxygen supply air duct 25 is provided with a second valve 251, and the third oxygen supply air duct 29 is provided with a third valve 291. The second valve 251 and the third valve 291 are used to control the opening and closing of the second oxygen supply air duct 25 and the third oxygen supply air duct 29, respectively.

[0082] Based on this, such as Figure 4-5 As shown, the auxiliary unit also includes a direct discharge pipeline 27. The direct discharge pipeline 27 is connected to the first air inlet pipeline 18 and the second air inlet pipeline 30, which are arranged in parallel. One end of the direct discharge pipeline 27 is connected to the output end of the buffer tank 15, and the other end is connected to the discharge cylinder 36. When the LEL detector 39 detects that the content of combustible gas in the raw material gas exceeds 25% of the minimum explosion limit, the raw material gas is directly discharged from the buffer tank 15 into the discharge cylinder 36. The minimum explosion limit is the standard limit for the treatment of combustible gas in the coal chemical industry. This standard limit is selected according to HJ 1093—2020 "Technical Specification for Industrial Waste Gas Treatment Engineering by Regenerative Combustion Method".

[0083] Based on this, the auxiliary unit also includes a first exhaust pipe 35 and a second exhaust pipe 32, which are respectively connected to the output ends of the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28. Both the first exhaust pipe 35 and the second exhaust pipe 32 are connected to the discharge stack 36, and are used to directly discharge a portion of the high-temperature purified flue gas after reaction in the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28. Specifically, the direct discharge of a portion of the high-temperature purified flue gas from the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28 through the discharge stack 36 via the first exhaust pipe 35 and the second exhaust pipe 32 is explained as follows: Because the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28... The structure and heating properties of furnace 28 itself require separate pipelines within the first regenerative incinerator 19 and the second regenerative incinerator 28 to accommodate high-temperature purified flue gas for storing heat in the regenerative ceramics inside the regenerative incinerator. After the regenerative ceramics have stored heat, they transfer heat to the high-temperature purified flue gas in the other pipelines, causing it to oxidize and burn at high temperature. Therefore, the portion of high-temperature purified flue gas that is directly discharged here refers to the portion of high-temperature purified flue gas used to store heat in the regenerative ceramics. Since the pipelines for this portion of high-temperature purified flue gas are different in each regenerative incinerator and the overall temperature decreases after being stored in the regenerative ceramics, it is no longer used to enter the energy recovery and utilization unit for heat exchange and is instead discharged directly.

[0084] Based on this, such as Figure 5 As shown, the input end of the purge fan 24 in the auxiliary unit is also connected to the first outlet pipeline 35 and the second outlet pipeline 32, so that part of the high-temperature purified flue gas is used as purge air and introduced into the first regenerative incinerator 19 and the second regenerative incinerator 28; in addition, the input end of the recirculation fan 34 in the recirculation air assembly is also connected to the first outlet pipeline 35 and the second outlet pipeline 32, so that part of the high-temperature purified flue gas is used as recirculation air and introduced into the CO2 emission pipeline 14.

[0085] Thus, the low-temperature methanol washing exhaust gas resource utilization system can complete the recovery and utilization of effective gases in the second original gas.

[0086] Based on the above embodiments, this application provides a method for the resource utilization of low-temperature methanol wash exhaust gas, based on the aforementioned low-temperature methanol wash exhaust gas resource utilization system. Figure 7 As shown, the specific steps include:

[0087] In step S1: the methanol solution after the low-temperature methanol washing process is subjected to flash evaporation to remove effective gases, and the effective gases obtained from the flash evaporation are recovered and reused.

[0088] Specifically, the methanol solution used in the low-temperature methanol washing process is fed into the first stage 2 of the flash tower through an external pipeline and undergoes depressurized flash evaporation at a pressure of 1.0-1.1 MPa to produce a first flash liquid and a flash gas. The flash gas is discharged from the first stage 2 of the flash tower. The first flash liquid is fed into the mass transfer separation device 6 through the first methanol solution pipeline 4 and undergoes depressurized flash evaporation at a pressure of 0.36-0.44 MPa to obtain a second flash liquid and a first raw gas. At this time, the first raw gas is discharged from the mass transfer separation device 6. The second flash liquid is fed into the second stage 3 of the flash tower through the second methanol solution pipeline 5 and undergoes depressurized flash evaporation at a pressure of 0.08 MPa to obtain a third flash liquid and a second raw gas. The third flash liquid enters the subsequent process equipment through an external pipeline, and the second raw gas is prepared to enter the second-stage system.

[0089] The flash vapor and the first raw gas enter the multi-stage compressor 10 through the second flash vapor line 9 and the first flash vapor line 8, respectively, and are pressurized to 3.6 MPa. Then, they are discharged to the low-temperature methanol wash high-pressure zone system through the third flash vapor line 11.

[0090] In step S2: the second raw gas obtained after depressurizing and flashing the second flash liquid in the second stage 3 of the flash tower is processed to obtain raw material gas.

[0091] Specifically, the second raw gas enters the CO2 scrubbing tower 13 through the fourth flash vapor pipeline 12 to obtain scrubbing gas. The scrubbing gas is mixed with the oxygen supplementing air and circulating air provided by the oxygen supplementing air assembly and the recirculation air assembly at a pressure of 5-12 kPa and a temperature of 8-10°C to form raw material gas. The raw material gas is then passed into the buffer tank 15 for buffer storage through the CO2 exhaust gas pipeline 14.

[0092] It should be noted that the scrubbing gas, oxygen supplementation air, and circulating air are mixed to form raw material gas. When the content of combustible gas in the raw material gas exceeds 25% of the minimum explosion limit at the location where the raw material gas passes through the LEL detector 39 in the CO2 emission gas pipeline 14, the raw material gas is directly discharged from the buffer tank 15 into the emission cylinder 36. When the content of combustible gas in the raw material gas does not exceed 25% of the minimum limit at the location where the raw material gas passes through the LEL detector 39 in the CO2 emission gas pipeline 14, the raw material gas is discharged from the buffer tank 15 into the regenerative combustion unit for high-temperature oxidation combustion treatment.

[0093] In step S3: After the raw gas is subjected to high-temperature oxidation and combustion treatment, the energy of the product is recovered and utilized using an energy recovery and utilization unit.

[0094] Specifically, the raw gas in the buffer tank 15 is divided into two paths and enters the first regenerative thermal oxidizer 19 and the second regenerative thermal oxidizer 28 through the first air inlet pipeline 18 and the second air inlet pipeline 30 respectively for high-temperature oxidation combustion to generate high-temperature purified flue gas. The high-temperature purified flue gas enters the flue gas side of the medium-pressure boiler 22 through the first high-temperature flue gas pipe 21 and the second high-temperature flue gas pipe 31. Based on the use of external water source to supply water to the water supply side of the medium-pressure boiler 22, the high-temperature purified flue gas heats the water on the water supply side in the medium-pressure boiler 22 to generate medium-pressure superheated steam with a pressure of 4.8 MPa and a temperature of 420°C. The medium-pressure superheated steam is sent to the external pipeline network for utilization through the superheated steam pipeline 40.

[0095] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-temperature methanol washing exhaust gas resource utilization system, characterized in that, include: First-tier system and second-tier system, wherein: The first-stage system includes a methanol solution mass transfer and separation processing unit and an effective gas pressurization and recovery unit. A methanol solution mass transfer and separation processing unit includes a flash tower and a mass transfer and separation device. The flash tower includes a first flash tower section and a second flash tower section located above the first flash tower section. The input end of the first flash tower section is connected to a low-temperature methanol washing device via an external pipeline to introduce the methanol solution from the low-temperature methanol washing device into the first flash tower section. The first flash tower section performs depressurization flash evaporation on the methanol solution to generate a first flash liquid and a flash vapor. Furthermore, the input end of the mass transfer separation device is connected to the liquid phase output end of the first stage of the flash tower via a first methanol solution pipeline, which is used to pass the first flash liquid into the mass transfer separation device for depressurized flash evaporation again to obtain the second flash liquid and the first original gas. On this basis, the gas phase output end of the mass transfer separation device is provided with a first flash vapor pipeline, which is used to exit the first original gas from the mass transfer separation device. The liquid phase output end of the mass transfer separation device is connected to the second stage of the flash tower via a second methanol solution pipeline, which is used to pass the second flash liquid into the second stage of the flash tower for depressurized flash evaporation to generate the third flash liquid and the second original gas. An effective gas pressurization and recovery unit includes a multi-stage compressor. The multi-stage compressor includes a low-pressure section input terminal and a high-pressure section input terminal. The low-pressure section input terminal of the multi-stage compressor is connected to the first flash vapor pipeline for receiving the first raw gas into the multi-stage compressor. The high-pressure input terminal of the multi-stage compressor is connected to the gas phase output terminal of a section of the flash tower through a second flash vapor pipeline for receiving flash gas into the multi-stage compressor. After being pressurized in the multi-stage compressor, the first raw gas and flash gas are discharged to the low-temperature methanol wash high-pressure zone system through a third flash vapor pipeline. The second-stage system includes a gas mixing and buffer unit, a regenerative thermal combustion unit, and an energy recovery and utilization unit. A gas mixing and buffer unit includes a CO2 scrubbing tower and a buffer tank. The CO2 scrubbing tower is used to absorb methanol. The input end of the CO2 scrubbing tower is connected to the gas phase output end of the second stage of the flash tower through a fourth flash vapor pipeline to receive the second raw gas. The output end of the CO2 scrubbing tower and the input end of the buffer tank are connected through a CO2 exhaust gas pipeline, so that the scrubbing gas obtained after the second raw gas is scrubbed by the CO2 scrubbing tower is introduced into the buffer tank. In addition, the gas mixing and buffer unit also includes an oxygen replenishment air assembly and a recirculation air assembly, which are respectively connected to the CO2 exhaust gas pipeline to provide oxygen replenishment air and recirculation air to the CO2 exhaust gas pipeline. The oxygen replenishment air, recirculation air and scrubbing gas are mixed to form a raw material gas, which is then buffered and stored in the buffer tank. The regenerative thermal oxidizer unit includes a first regenerative thermal oxidizer and a second regenerative thermal oxidizer. The input end of the first regenerative thermal oxidizer is provided with a first air inlet pipeline, and the input end of the second regenerative thermal oxidizer is provided with a second air inlet pipeline. The first air inlet pipeline and the second air inlet pipeline are connected in parallel and connected to the output end of the buffer tank. The raw material gas in the buffer tank is divided into two paths and enters the first regenerative thermal oxidizer and the second regenerative thermal oxidizer through the first air inlet pipeline and the second air inlet pipeline respectively for high-temperature oxidation and combustion to generate high-temperature purified flue gas. In addition, the output end of the first regenerative thermal oxidizer is provided with a first high-temperature flue gas pipe, and the output end of the second regenerative thermal oxidizer is provided with a second high-temperature flue gas pipe for discharging the high-temperature purified flue gas. An energy recovery and utilization unit includes a medium-pressure boiler, which comprises a flue gas side and a water supply side. The flue gas side of the medium-pressure boiler is connected to a first high-temperature flue gas pipe and a second high-temperature flue gas pipe, and is used to receive part of the high-temperature purified flue gas generated by the first and second regenerative thermal oxidizers. The water supply side of the medium-pressure boiler is connected to an external water source through a water supply pipeline, and the external water source supplies water to the water supply side of the medium-pressure boiler. The medium-pressure boiler heats the water on the water supply side with the high-temperature purified flue gas on the flue gas side to generate medium-pressure superheated steam, and sends the medium-pressure superheated steam to an external pipeline network for recovery and utilization through a superheated steam pipeline. In addition, the output end of the medium-pressure boiler is also equipped with a purified flue gas pipeline, and the end of the purified flue gas pipeline is connected to an exhaust stack. The remaining flue gas after the high-temperature purified flue gas in the medium-pressure boiler heats the water is the purified flue gas. The purified flue gas is introduced into the exhaust stack through the purified flue gas pipeline for discharge. The exhaust stack is also equipped with a CEMS analyzer for analyzing the content of various gases in the purified flue gas.

2. The low-temperature methanol washing exhaust gas resource utilization system according to claim 1, characterized in that: In the methanol solution mass transfer and separation processing unit, the gas pressure in the first stage of the flash tower is 1.0-1.1 MPa, and the composition of the flash gas obtained by depressurizing and flashing the methanol solution in the first stage of the flash tower, in volume fractions, is CH4: 25.67%, H2: 25.63%, CO2: 28.38%, CO: 16.38%, C2H6: 0.09%, C2H4: 0.13%, C3H8: 0.1%, N2: 0.74%. The gas pressure in the mass transfer separation device is 0.36-0.44 MPa, and the composition of the first raw gas produced by depressurization flash evaporation, by volume fraction, is CH4: 11.53%, H2: 0.57%, CO2: 80.62%, CO: 2.39%, C2H6: 2.06%, C2H4: 0.03%, C3H8: 0.11%, N2: 2.01%. The pressure in the second stage of the flash tower is 0.08 MPa, and the composition of the second original gas produced by the depressurization flash evaporation is as follows (by volume fraction): CO2: 93.96%, CH4: 2.03%, CO: 0.21%, N2: 1.29%, C2H6: 1.62%, C3H8: 0.11%.

3. The low-temperature methanol washing exhaust gas resource utilization system according to claim 2, characterized in that: In the methanol solution mass transfer and separation processing unit, the second methanol solution pipeline is a three-way pipeline, and in addition to being connected to the mass transfer and separation equipment and the two sections of the flash tower, the second methanol solution pipeline is also connected to the first methanol solution pipeline. Based on this, the second methanol solution pipeline is also equipped with a first control valve and a second control valve. At the same time, the first control valve is located between the tee joint of the second methanol solution pipeline and the joint between the second methanol solution pipeline and the first methanol solution pipeline. The second control valve is located between the tee joint of the second methanol solution pipeline and the liquid phase output end of the mass transfer separation device. In addition, the first methanol solution pipeline is equipped with a third control valve, which is located between the input end of the mass transfer separation device and the joint between the first methanol solution pipeline and the second methanol solution pipeline. The mass transfer separation equipment is also equipped with a flash vapor venting pipeline, which is used to depressurize the mass transfer separation equipment when it experiences an abnormal overpressure operation or when the entire system shuts down. The liquid output end of the second section of the flash tower is also connected to an external pipeline, through which the third flash liquid is output to the subsequent process equipment.

4. The low-temperature methanol washing exhaust gas resource utilization system according to claim 3, characterized in that: In the effective gas pressurization and recovery unit, the multi-stage compressor pressurizes the first raw gas and flash vapor inside it to 3.6 MPa and then exports them to the low-temperature methanol wash high-pressure zone system through the third flash vapor pipeline.

5. The low-temperature methanol washing exhaust gas resource utilization system according to claim 4, characterized in that: In the gas mixing buffer unit, the oxygen replenishment air assembly includes an oxygen replenishment fan and a first oxygen replenishment air pipeline. The first oxygen replenishment air pipeline is used to connect the oxygen replenishment fan with the CO2 exhaust gas pipeline and to introduce the oxygen replenishment air provided by the oxygen replenishment fan into the CO2 exhaust gas pipeline. In addition, the first oxygen replenishment air pipeline is also provided with a first valve to control the opening and closing state of the first oxygen replenishment air pipeline. The recirculation air assembly includes a recirculation fan and a first recirculation pipeline. The first recirculation pipeline is used to connect the recirculation fan to the CO2 emission pipeline and to introduce the recirculation air provided by the recirculation fan into the CO2 emission pipeline. The second raw gas, after being washed by the CO2 scrubbing tower, is mixed with oxygen-supplementing air and circulating air to form raw material gas, which is then passed into a buffer tank for buffer storage. In addition, an LEL detector is installed on the CO2 emission gas pipeline, and the LEL detector is located downstream of the junction of the CO2 emission gas pipeline and the first oxygen-supplementing air pipeline and the first recirculation pipeline. It is used to detect the content of combustible gas in the raw material gas, which is the sum of CH4, H2, CO, C2H6, C2H4 and C3H8.

6. The low-temperature methanol washing exhaust gas resource utilization system according to claim 5, characterized in that: In the regenerative thermal combustion unit, the first regenerative thermal combustion furnace and the second regenerative thermal combustion furnace are connected in parallel. The temperature for high-temperature oxidation and combustion of the raw gas in the first and second regenerative thermal combustion furnaces is 900-1000℃. The high-temperature oxidation and combustion of the raw gas generates CO2 and H2O to form high-temperature purified flue gas and releases heat energy. In addition, a first air inlet valve is provided on the first air inlet pipeline and a second air inlet valve is provided on the second air inlet pipeline to control the opening and closing of the first air inlet pipeline and the second air inlet pipeline respectively. The first high-temperature flue gas pipe and the second high-temperature flue gas pipe are connected to the flue gas side of the medium-pressure boiler.

7. A low-temperature methanol washing exhaust gas resource utilization system according to claim 6, characterized in that: The aforementioned low-temperature methanol wash exhaust gas resource utilization system further includes an auxiliary unit, which includes a purge fan. The output end of the purge fan is connected to a first purge air pipeline and a second purge air pipeline via a three-way pipeline. The first purge air pipeline is connected to the first regenerative thermal incinerator, and the second purge air pipeline is connected to the second regenerative thermal incinerator, providing purge air to the first and second regenerative thermal incinerators respectively. In addition, a first on / off valve is installed on the first purge air pipeline, and a second on / off valve is installed on the second purge air pipeline, for controlling the on / off of the first and second purge air pipelines respectively.

8. The low-temperature methanol washing exhaust gas resource utilization system according to claim 7, characterized in that: The auxiliary unit also includes a second oxygen supply air duct and a third oxygen supply air duct. One end of the second oxygen supply air duct and the third oxygen supply air duct are connected in parallel and connected to the oxygen supply fan. The other end of the second oxygen supply air duct is connected to the first air inlet duct, and the other end of the third oxygen supply air duct is connected to the second air inlet duct. These are used to provide oxygen supply air to the first regenerative thermal oxidizer and the second regenerative thermal oxidizer and to replace the air in the first regenerative thermal oxidizer and the second regenerative thermal oxidizer. In addition, a second valve is provided on the second oxygen supply air duct, and a third valve is provided on the third oxygen supply air duct. The second valve and the third valve are used to control the opening and closing of the second oxygen supply air duct and the third oxygen supply air duct, respectively. In addition, the auxiliary unit also includes a direct discharge pipeline. The direct discharge pipeline is connected to the first and second air inlet pipelines arranged in parallel. One end of the direct discharge pipeline is connected to the output end of the buffer tank, and the other end is connected to the discharge cylinder. When the LEL detector detects that the content of combustible gas in the raw material gas exceeds 25% of the minimum explosion limit, the raw material gas is directly discharged from the buffer tank into the discharge cylinder. Based on this, the auxiliary unit also includes a first gas outlet pipeline connected to the output end of the first regenerative thermal incinerator and a second gas outlet pipeline connected to the output end of the second regenerative thermal incinerator. Both the first and second gas outlet pipelines are connected to the discharge stack, which are used to discharge part of the high-temperature purified flue gas after reaction in the first and second regenerative thermal incinerators, respectively.

9. A method for resource utilization of low-temperature methanol wash exhaust gas, employing the low-temperature methanol wash exhaust gas resource utilization system according to any one of claims 1-8, characterized in that, Includes the following steps: S1: Flash evaporation of the methanol solution after the low-temperature methanol washing process is performed to remove the effective gas, and the effective gas obtained from the flash evaporation is recovered and reused. In this process, the methanol solution used in the low-temperature methanol washing process is fed into the first stage of a flash tower through an external pipeline and undergoes depressurization flash evaporation at a pressure of 1.0-1.1 MPa to produce a first flash liquid and a flash gas. The flash gas is discharged from the first stage of the flash tower, while the first flash liquid is fed into a mass transfer separation device through a first methanol solution pipeline and undergoes depressurization flash evaporation at a pressure of 0.36-0.44 MPa to obtain a second flash liquid and a first raw gas. At this point, the first raw gas is discharged from the mass transfer separation device, while the second flash liquid is fed into the second stage of the flash tower through a second methanol solution pipeline and undergoes depressurization flash evaporation at a pressure of 0.08 MPa to obtain a third flash liquid and a second raw gas. The third flash liquid is fed into subsequent process equipment through an external pipeline, while the second raw gas is prepared to enter the second-stage system. The flash vapor enters the multi-stage compressor through the second flash vapor pipeline, is pressurized to 3.6 MPa, and then exits to the low-temperature methanol wash high-pressure zone system through the third flash vapor pipeline; The first raw gas enters the multi-stage compressor through the first flash vapor pipeline and is pressurized to 3.6 MPa, and then exits to the low-temperature methanol wash high-pressure zone system through the third flash vapor pipeline; S2: The second raw gas obtained after depressurizing and flashing the second flash liquid in the second stage of the flash tower is processed to obtain the raw material gas; The second raw gas enters the CO2 scrubbing tower through the fourth flash vapor pipeline to obtain scrubbing gas. The scrubbing gas is mixed with the oxygen supplementation air and recirculation air provided by the oxygen supplementation air component and the recirculation air component to form raw material gas. The raw material gas is then passed into the buffer tank for buffer storage through the CO2 exhaust gas pipeline. S3: After the raw gas is subjected to high-temperature oxidation and combustion treatment, the energy of the product is recovered and utilized using an energy recovery and utilization unit. The raw gas in the buffer tank is divided into two streams and enters the first and second regenerative thermal oxidizers through the first and second inlet pipelines, respectively, to generate high-temperature purified flue gas through high-temperature oxidation combustion. The high-temperature purified flue gas enters the flue gas side of the medium-pressure boiler through the first and second high-temperature flue gas pipes. With the external water source supplying water to the water supply side of the medium-pressure boiler, the high-temperature purified flue gas heats the water on the water supply side in the medium-pressure boiler to generate medium-pressure superheated steam with a pressure of 4.8 MPa and a temperature of 420°C. The medium-pressure superheated steam is sent to the external pipeline network for utilization through the superheated steam pipeline.

10. A method for resource utilization of low-temperature methanol washing exhaust gas according to claim 9, characterized in that: In step S2, the scrubbing gas, oxygen-supplementing air, and circulating air are mixed to form raw material gas. When the content of combustible gas in the raw material gas exceeds 25% of the minimum explosion limit at the location where the raw material gas passes through the LEL detector in the CO2 emission gas pipeline, the raw material gas is directly discharged from the buffer tank into the emission cylinder. When the content of combustible gas in the raw material gas does not exceed 25% of the minimum limit at the location where the raw material gas passes through the LEL detector in the CO2 emission gas pipeline, the raw material gas is fed from the buffer tank into the regenerative thermal oxidative combustion unit for high-temperature oxidation combustion treatment.

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