A separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash.

Abstract

This invention provides a separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash. The system includes a flue gas pipeline, an absorption tower, a first branch pipe, a desorption tower, a heat exchanger, a membrane module, a mixing tank, and a condensation unit. The flue gas pipeline is connected to the lower inlet of the absorption tower, the bottom outlet of the absorption tower is connected to the first end of the first branch pipe, and the second end of the first branch pipe is connected to the upper inlet of the desorption tower. The heat exchanger is located on the first branch pipe. The input end of the membrane module is connected to the top outlet of the absorption tower, and the output end of the membrane module is connected to the mixing tank. The top outlet of the desorption tower is connected to the condensation unit, and the first output end of the condensation unit is connected to the mixing tank. One technical advantage of this invention is that it can obtain product gas with a CO2 concentration of 42% required by the soda ash production equipment, thereby achieving the utilization of CO2 from coal-fired flue gas and possessing significant application value.

Description

Technical Field

[0001] This invention belongs to the field of flue gas treatment technology for thermal power plants, and specifically relates to a separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash. Background Technology

[0002] Many thermal power plants are currently preparing to build carbon capture (CC) systems to effectively reduce carbon emissions from coal-fired power units and contribute to the green transformation of the coal-fired power sector. However, how to utilize the captured CO2 has become a bottleneck hindering the large-scale implementation of carbon capture and urgently needs to be addressed.

[0003] Furthermore, the raw materials used in the ammonia-soda process for producing soda ash include brine, quicklime, coal, and ammonia. The CO2 gas required for soda ash production is generated by the calcination and decomposition of limestone and coal, which necessitates additional energy consumption for calcining the limestone.

[0004] Therefore, there is an urgent need for a separation system for flue gas from thermal power plants used in the ammonia-soda process to produce soda ash, which can capture and treat CO2 in the flue gas and then use it in the soda ash production process. This can not only further reduce resource consumption in the production process, but also improve the resource utilization efficiency of CO2. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art, and to provide a new technical solution for the separation system of flue gas from thermal power plants for the production of soda ash by the ammonia-soda process.

[0006] According to a first aspect of the present invention, a separation system for flue gas from a thermal power plant used in the ammonia-soda process for producing soda ash is provided, comprising:

[0007] The system includes a flue gas duct, an absorption tower, a first branch pipe, a desorption tower, and a heat exchanger. The flue gas duct is connected to the lower inlet of the absorption tower, the bottom outlet of the absorption tower is connected to the first end of the first branch pipe, and the second end of the first branch pipe is connected to the upper inlet of the desorption tower. The heat exchanger is located on the first branch pipe.

[0008] A membrane module and a mixing tank, wherein the input end of the membrane module is connected to the top outlet of the absorption tower, and the output end of the membrane module is connected to the mixing tank;

[0009] A condensation unit is provided, with the top outlet of the desorption tower connected to the condensation unit and the first output end of the condensation unit connected to the mixing tank.

[0010] The flue gas input from the lower inlet of the absorption tower comes into countercurrent contact with the absorbent input from the upper inlet of the absorption tower to form a first gas flow and a rich liquid;

[0011] The first gas flow enters the membrane module from the top outlet of the absorption tower, and after separation by the membrane module, nitrogen gas is formed and enters the mixing tank.

[0012] The rich liquid is discharged from the bottom outlet of the absorption tower into the first branch pipe, and after being heated by the heat exchanger, it enters the desorption tower. After being desorbed in the desorption tower, the rich liquid forms a second gas flow and a lean liquid. The lean liquid is discharged from the bottom outlet of the desorption tower. The second gas flow passes through the condensation unit to form carbon dioxide and condensate. The carbon dioxide enters the mixing tank and mixes with nitrogen to form a product gas with a preset ratio for the production of soda ash using the ammonia-soda process.

[0013] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash further includes a second branch pipe and a reboiler. The first end of the second branch pipe is connected to the bottom outlet of the desorption tower, the second end of the second branch pipe is connected to the middle inlet of the desorption tower, and the reboiler is disposed on the second branch pipe.

[0014] The lean liquor discharged from the bottom outlet of the desorption tower is heated by the reboiler and then enters the desorption tower through the middle inlet to desorb the rich liquor.

[0015] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash further includes a third branch pipe; the heat exchanger is connected to the third branch pipe.

[0016] The first end of the third branch pipe is connected to the reboiler, and the other end is connected to the upper inlet of the absorption tower.

[0017] A portion of the lean liquor in the reboiler is extracted and heated at the heat exchanger to heat the rich liquor. The cooled lean liquor then enters the absorption tower through the upper inlet.

[0018] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash also includes a compressor for compressing the first gas stream.

[0019] The top outlet of the absorption tower is connected to the compressor, and the compressor is connected to the membrane module;

[0020] The first gas flow is compressed in the compressor and then separated by the membrane module.

[0021] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash further includes a rich liquid pump, which is installed on the first branch pipe and located between the absorption tower and the heat exchanger.

[0022] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash also includes a lean liquor pump, which is located in the third branch pipe and between the reboiler and the heat exchanger.

[0023] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash also includes a booster pump and a lean liquor cooler.

[0024] Both the booster pump and the lean liquid cooler are located on the third branch pipe, with the booster pump situated between the heat exchanger and the absorption tower, and the lean liquid cooler situated between the booster pump and the absorption tower.

[0025] Optionally, the condensation unit includes a first condenser, a second condenser, a reflux pump, and a fourth branch pipe;

[0026] The first end of the fourth branch pipe is connected to the top outlet of the desorption tower, and the second end is connected to the upper outlet of the desorption tower. The first condenser, the second condenser, and the reflux pump are all installed on the fourth branch pipe.

[0027] The second gas stream passes sequentially through the first condenser and the second condenser to form carbon dioxide and condensate. The condensate is then returned to the desorption tower by the reflux pump.

[0028] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash further includes a first gas storage tank and a first flow meter; the membrane module is connected to the mixing tank in sequence via the first gas storage tank and the first flow meter.

[0029] The first gas storage tank is used to store the nitrogen gas.

[0030] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash further includes a second gas storage tank and a second flow meter; the condensation unit is connected to the mixing tank in sequence via the second gas storage tank and the second flow meter.

[0031] The second gas storage tank is used to store the carbon dioxide.

[0032] One technical advantage of this invention is that:

[0033] In this embodiment, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash economically and efficiently treats and captures CO2 from the flue gas by coupling chemical absorption and membrane separation. On one hand, chemical absorption is used to capture and separate carbon dioxide from the flue gas, obtaining a carbon dioxide concentration of 99%. On the other hand, a membrane module is used to separate the first gas stream (i.e., purified gas) at the top outlet of the absorption tower, increasing the nitrogen concentration in the first gas stream from 93% to over 98%. Then, the high-concentration nitrogen and carbon dioxide are mixed to obtain product gas with a CO2 concentration of 42% required by the soda ash production equipment, thus achieving the utilization of CO2 from coal-fired flue gas and demonstrating good application value. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a separation system for flue gas from a thermal power plant used in the ammonia-soda process for producing soda ash, according to an embodiment of the present invention.

[0035] Figure 2 This is a reference diagram showing the usage status of a separation system for flue gas from a thermal power plant used in the ammonia-soda process for producing soda ash, according to an embodiment of the present invention.

[0036] In the diagram: 1. Flue gas duct; 2. Absorption tower; 3. First branch pipe; 4. Desorption tower; 5. Heat exchanger; 6. Membrane module; 7. Mixing tank; 81. First condenser; 82. Second condenser; 83. Reflux pump; 84. Fourth branch pipe; 9. Second branch pipe; 10. Reboiler; 11. Third branch pipe; 12. Compressor; 13. Rich solution pump; 14. Lean solution pump; 15. First gas storage tank; 16. First flow meter; 17. Second gas storage tank; 18. Second flow meter; 19. Booster pump; 20. Lean solution cooler. Detailed Implementation

[0037] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0038] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0039] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0040] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and 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, and therefore should not be construed as a limitation of this application.

[0041] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" 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 between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0042] According to a first aspect of the invention, see figures and Figure 2 A separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash is provided, comprising:

[0043] The system includes a flue gas duct 1, an absorption tower 2, a first branch pipe 3, a desorption tower 4, and a heat exchanger 5. The flue gas duct 1 is connected to the lower inlet of the absorption tower 2, the bottom outlet of the absorption tower 2 is connected to the first end of the first branch pipe 3, and the second end of the first branch pipe 3 is connected to the upper inlet of the desorption tower 4. The heat exchanger 5 is located on the first branch pipe 3.

[0044] Membrane module 6 and gas mixing tank 7, wherein the input end of membrane module 6 is connected to the top outlet of absorption tower 2, and the output end of membrane module 6 is connected to gas mixing tank 7;

[0045] The top outlet of the desorption tower 4 is connected to the condensation unit, and the first output end of the condensation unit is connected to the mixing tank 7.

[0046] The flue gas input from the lower inlet of the absorption tower 2 comes into countercurrent contact with the absorbent input from the upper inlet of the absorption tower 2 to form a first gas flow and a rich liquid;

[0047] The first gas flow enters the membrane module 6 from the top outlet of the absorption tower 2, and is separated by the membrane module 6 to form nitrogen gas which enters the mixing tank 7.

[0048] The rich liquid is discharged from the bottom outlet of the absorption tower 2 into the first branch pipe 3, and after being heated by the heat exchanger 5, it enters the desorption tower 4. After being desorbed in the desorption tower 4, the rich liquid forms a second gas flow and a lean liquid. The lean liquid is discharged from the bottom outlet of the desorption tower 4. The second gas flow passes through the condensation unit to form carbon dioxide and condensate. The carbon dioxide enters the mixing tank 7 and mixes with nitrogen to form a product gas with a preset ratio for the production of soda ash using the ammonia-soda process.

[0049] In this embodiment, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash economically and efficiently treats and captures CO2 from the flue gas by coupling chemical absorption and membrane separation. On one hand, chemical absorption is used to capture and separate carbon dioxide from the flue gas, obtaining a carbon dioxide concentration of 99%. On the other hand, membrane module 6 is used to separate the first gas stream (i.e., purified gas) at the top outlet of absorption tower 2, increasing the nitrogen concentration in the first gas stream from 93% to over 98%. Then, the high-concentration nitrogen and carbon dioxide are mixed to obtain product gas with a CO2 concentration of 42% required by the soda ash production equipment, thus achieving the utilization of CO2 from coal-fired flue gas and demonstrating good application value.

[0050] It should be noted that matching the CO2 capture process in thermal power plant flue gas with the ammonia-soda process requires understanding the supply and demand relationship between the flue gas from thermal power plants and the feed gas for ammonia-soda alkali production. The volume ratio of flue gas components in thermal power plants is typically 81% N2, 13% CO2, and 6% O2. The ammonia-soda process requires the product gas (i.e., the CO2 feed gas) to have 42% CO2, 57% N2, and less than 1% O2. The product gas prepared in this application for the ammonia-soda process can meet the requirements of the ammonia-soda process, thus achieving the absorption of carbon dioxide from coal-fired flue gas and demonstrating good application value.

[0051] In this embodiment, the working principle of the separation system for the flue gas of a thermal power plant used in the ammonia-soda process for producing soda ash is as follows: The flue gas to be treated (CO2 concentration of 13%, O2 concentration of 6%, N2 concentration of 81%) enters the absorption tower 2 from the lower inlet of the absorption tower 2 through a coupled chemical absorption method. It comes into countercurrent contact with the absorbent pumped in from the upper inlet of the absorption tower 2 by the booster pump 19. The CO2 in the flue gas reacts with the absorbent and is removed. The purified flue gas (i.e., the first gas flow) is discharged from the top outlet of the absorption tower 2 and sent to the membrane module 6 through the compressor 12. After separation by the membrane module 6, nitrogen-rich gas (N2 concentration of 98%) and oxygen-rich gas are generated. The oxygen-rich gas is directly discharged into the atmosphere, while the nitrogen-rich gas (i.e., nitrogen) enters the first gas storage tank 15. After the flow rate is adjusted by the first flow meter 16, it enters the mixing tank 7 to wait for mixing. The rich liquid discharged from the bottom outlet of absorption tower 2 is pumped into heat exchanger 5 by rich liquid pump 13. After heat exchange and temperature increase, it enters desorption tower 4 from the upper inlet to desorb carbon dioxide. The second gas flow (i.e., desorption gas flow) generated in desorption tower 4 is discharged from the top outlet of desorption tower 4 and enters the first condenser 81 and the second condenser 82 (the second condenser 82 can be a reflux condenser), which respectively produce CO2 gas with a concentration of 99% and condensate. The condensate flows back into desorption tower 4 from the condensate inlet of desorption tower 4. The lean liquid discharged from the bottom outlet of desorption tower 4 enters desorption tower 4 through reboiler 10 to provide heat for the desorption process. Part of the lean liquid in reboiler 10 enters heat exchanger 5 through lean liquid pump 14. The lean liquid is further cooled and pressurized to about 40°C and becomes absorbent to enter absorption tower 2 to absorb carbon dioxide.

[0052] Finally, CO2 gas with a concentration of 99% enters the second storage tank 17. After the flow rate is adjusted by the second flow meter 18, it is mixed with nitrogen in the mixing tank 7 to form the product gas required for the alkali production process (CO2 concentration of 42% and N2 concentration of 58%).

[0053] Optionally, the separation system for the flue gas of a thermal power plant used in the ammonia-soda process for producing soda ash further includes a second branch pipe 9 and a reboiler 10. The first end of the second branch pipe 9 is connected to the bottom outlet of the desorption tower 4, and the second end of the second branch pipe 9 is connected to the middle inlet of the desorption tower 4. The reboiler 10 is disposed on the second branch pipe 9.

[0054] The lean liquid discharged from the bottom outlet of the desorption tower 4 is heated by the reboiler 10 and then enters the desorption tower 4 through the middle inlet to desorb the rich liquid.

[0055] In the above embodiment, the water vapor generated in the reboiler 10 is transported to the desorption tower 4 through the third branch pipe 11 to desorb the rich liquid. The desorption process is relatively simple.

[0056] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash also includes a third branch pipe 11; the heat exchanger 5 is connected to the third branch pipe 11.

[0057] The first end of the third branch pipe 11 is connected to the reboiler 10, and the other end is connected to the upper inlet of the absorption tower 2.

[0058] A portion of the lean liquor in the reboiler 10 is extracted and heated in the heat exchanger 5 to heat the rich liquor. The cooled lean liquor then enters the absorption tower 2 through the upper inlet.

[0059] In the above embodiments, the absorbent can be recycled.

[0060] Optionally, the separation system for the flue gas from the thermal power plant used in the ammonia-soda process for producing soda ash also includes a compressor 12, which is used to compress the first gas flow.

[0061] The top outlet of the absorption tower 2 is connected to the compressor 12, and the compressor 12 is connected to the membrane module 6;

[0062] The first airflow is compressed in the compressor 12 and then separated by the membrane module 6.

[0063] In the above embodiment, the compressor 12 can effectively compress the first gas flow, thereby helping the membrane module 6 to separate the compressed first gas flow.

[0064] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash further includes a rich liquid pump 13, which is installed on the first branch pipe 3 and located between the absorption tower 2 and the heat exchanger 5.

[0065] In the above embodiment, the rich liquid pump 13 helps to smoothly pump the rich liquid to the desorption tower 4.

[0066] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash also includes a lean liquor pump 14, which is located in the third branch pipe 11 and between the reboiler 10 and the heat exchanger 5.

[0067] In the above embodiment, the lean liquid pump 14 helps to smoothly pump the lean liquid to the absorption tower 2.

[0068] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash also includes a booster pump 19 and a lean liquor cooler 20.

[0069] Both the booster pump 19 and the lean liquid cooler 20 are located on the third branch pipe 11, with the booster pump 19 located between the heat exchanger 5 and the absorption tower 2, and the lean liquid cooler 20 located between the booster pump 19 and the absorption tower 2.

[0070] In the above embodiments, the booster pump 19 and the lean liquid cooler 20 can effectively ensure that the lean liquid at the preset temperature and preset pressure is delivered to the absorption tower 2, thus effectively realizing the recycling of the absorbent.

[0071] Optionally, the condensation unit includes a first condenser 81, a second condenser 82, a reflux pump 83, and a fourth branch pipe 84; wherein the second condenser 82 can be a reflux condenser.

[0072] The first end of the fourth branch pipe 84 is connected to the top outlet of the desorption tower 4, and the second end is connected to the upper outlet of the desorption tower 4. The first condenser 81, the second condenser 82, and the reflux pump 83 are all installed on the fourth branch pipe 84.

[0073] The second gas flow passes sequentially through the first condenser 81 and the second condenser 82, forming carbon dioxide and condensate. The condensate is then returned to the desorption tower 4 by the reflux pump 83.

[0074] In the above embodiments, the condensation unit has a reasonable structural design, which not only helps to obtain high concentrations of carbon dioxide, but also enables the recycling of condensate, thus saving water resources.

[0075] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash further includes a first gas storage tank 15 and a first flow meter 16; the membrane module 6 is connected to the mixing tank 7 in sequence via the first gas storage tank 15 and the first flow meter 16.

[0076] The first gas storage tank 15 is used to store the nitrogen gas.

[0077] In the above embodiments, it is helpful to accurately adjust the amount of nitrogen entering the mixing tank 7, thereby achieving precise mixing of nitrogen and carbon dioxide, and better ensuring that the product gas can be used in the ammonia-soda process to produce soda ash.

[0078] Optionally, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash further includes a second gas storage tank 17 and a second flow meter 18; the condensation unit is connected to the mixing tank 7 in sequence via the second gas storage tank 17 and the second flow meter 18.

[0079] The second gas storage tank 17 is used to store the carbon dioxide.

[0080] In the above embodiments, it is helpful to accurately adjust the amount of carbon dioxide entering the mixing tank 7, thereby achieving precise mixing of carbon dioxide and nitrogen, and better ensuring that the product gas can be used in the ammonia-soda process to produce soda ash.

[0081] In one specific embodiment, after the boiler flue gas undergoes pollutant removal and dust removal treatment, it is cooled to 40°C by a water cooler and then enters the absorption tower 2 from the lower inlet. Inside the absorption tower 2, it reacts counter-currently with the absorbent. Afterward, it is circulated and washed in the top water scrubbing tower of the absorption tower 2 to remove some of the volatile absorbent before exiting the absorption tower 2 from the top outlet. Simultaneously, the absorbent is sprayed from top to bottom at the top of the absorption tower 2, reacting with CO2 to form a rich liquid, which is discharged from the bottom outlet of the absorption tower 2. The rich liquid is heated in the heat exchanger 5 and then enters the desorption tower 4 (i.e., the regeneration tower), where it releases CO2 under heat, completing the regeneration process of the absorbent. The regenerated CO2 is extracted from the desorption tower 4 by the water vapor generated inside the desorption tower 4 and then condensed to obtain high-purity CO2. The water vapor in the regeneration process comes from the reboiler 10, and its heat source is typically steam from the low-pressure cylinder of the power plant. The regenerated absorbent (i.e., lean solution) is discharged from the bottom outlet of the desorption tower 4, cooled to 40°C by the makeup liquid heat exchanger 5 and the lean solution cooler 20, and then re-enters the absorption tower 2 to circulate and absorb CO2. The lean solution can also be stored in a storage tank located in the third branch pipe 11.

[0082] Furthermore, the main components of the first gas stream (i.e., purified gas) at the top outlet of absorption tower 2 are N2 with a concentration of 93% and O2 with a concentration of 6%, as well as a small amount of CO2. A portion of the gas is extracted from the first gas stream at the top outlet of absorption tower 2, dehydrated, and then pressurized to 8.5 bar by compressor 12 before being sent to membrane module 6 (i.e., membrane separation system). Due to the different selectivity of membrane module 6 for N2 and O2 gases, the N2 / O2 mixture will be separated into two outlet gas streams in the membrane separation system, one of which is an N2-enriched gas stream and the other is an O2-enriched gas stream.

[0083] The N2 enriched gas stream (i.e., nitrogen) from membrane module 6 is mixed with the CO2 gas stream (i.e., carbon dioxide) from the chemical absorption system and then sent to the alkali production process. In the alkali production process, the waste sludge from production can be transported through pipelines to the desulfurization system of a thermal power plant for use. The calcium oxide and a small amount of sodium hydroxide contained in the sludge can be used as a desulfurization absorbent, reducing the operating cost of desulfurization.

[0084] In the embodiments of this application, the separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash can effectively decarbonize the flue gas and use the obtained CO2 in the subsequent ammonia-soda process for producing soda ash. This system reduces the CO2 production cost for soda ash manufacturers, solves the problems of carbon capture and resource utilization in coal-fired power plants, and enables the cascade utilization of waste heat from thermal power plants, improving energy efficiency and reducing the operating cost of the carbon capture system, thus achieving a win-win situation and effectively promoting the development of a circular economy.

[0085] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash, characterized in that, include: The system includes a flue gas duct, an absorption tower, a first branch pipe, a desorption tower, and a heat exchanger. The flue gas duct is connected to the lower inlet of the absorption tower, the bottom outlet of the absorption tower is connected to the first end of the first branch pipe, and the second end of the first branch pipe is connected to the upper inlet of the desorption tower. The heat exchanger is located on the first branch pipe. A membrane module and a mixing tank, wherein the input end of the membrane module is connected to the top outlet of the absorption tower, and the output end of the membrane module is connected to the mixing tank; A condensation unit is provided, with the top outlet of the desorption tower connected to the condensation unit and the first output end of the condensation unit connected to the mixing tank. The flue gas input from the lower inlet of the absorption tower comes into countercurrent contact with the absorbent input from the upper inlet of the absorption tower to form a first gas flow and a rich liquid; The first gas flow enters the membrane module from the top outlet of the absorption tower, and is separated by the membrane module to form nitrogen gas which enters the mixing tank. The rich liquid is discharged from the bottom outlet of the absorption tower into the first branch pipe, and after being heated by the heat exchanger, it enters the desorption tower. After being desorbed in the desorption tower, the rich liquid forms a second gas flow and a lean liquid. The lean liquid is discharged from the bottom outlet of the desorption tower. The second gas flow passes through the condensation unit to form carbon dioxide and condensate. The carbon dioxide enters the mixing tank and mixes with nitrogen to form a product gas with a preset ratio for the production of soda ash using the ammonia-soda process.

2. The separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash according to claim 1, characterized in that, It also includes a second branch pipe and a reboiler. The first end of the second branch pipe is connected to the bottom outlet of the desorption tower, and the second end of the second branch pipe is connected to the middle inlet of the desorption tower. The reboiler is disposed on the second branch pipe. The lean liquor discharged from the bottom outlet of the desorption tower is heated by the reboiler and then enters the desorption tower through the middle inlet to desorb the rich liquor.

3. The separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash according to claim 2, characterized in that, It also includes a third branch pipe; the heat exchanger is connected to the third branch pipe; The first end of the third branch pipe is connected to the reboiler, and the other end is connected to the upper inlet of the absorption tower. A portion of the lean liquor in the reboiler is extracted and heated at the heat exchanger to heat the rich liquor. The cooled lean liquor then enters the absorption tower through the upper inlet.

4. The separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash according to claim 3, characterized in that, It also includes a compressor for compressing the first airflow; The top outlet of the absorption tower is connected to the compressor, and the compressor is connected to the membrane module; The first gas flow is compressed in the compressor and then separated by the membrane module.

5. The separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash according to claim 4, characterized in that, It also includes a rich liquid pump, which is installed on the first branch pipe and is located between the absorption tower and the heat exchanger.

6. The separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash according to claim 5, characterized in that, It also includes a lean liquid pump, which is disposed in the third branch pipe and located between the reboiler and the heat exchanger.

7. The separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash according to claim 6, characterized in that, It also includes booster pumps and lean liquid coolers; Both the booster pump and the lean liquid cooler are located on the third branch pipe, with the booster pump situated between the heat exchanger and the absorption tower, and the lean liquid cooler situated between the booster pump and the absorption tower.

8. The separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash according to claim 7, characterized in that, The condensation unit includes a first condenser, a second condenser, a reflux pump, and a fourth branch pipe; The first end of the fourth branch pipe is connected to the top outlet of the desorption tower, and the second end is connected to the upper outlet of the desorption tower. The first condenser, the second condenser, and the reflux pump are all installed on the fourth branch pipe. The second gas stream passes sequentially through the first condenser and the second condenser to form carbon dioxide and condensate. The condensate is then returned to the desorption tower by the reflux pump.

9. The separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash according to claim 1, characterized in that, It also includes a first gas storage tank and a first flow meter; the membrane module is connected to the mixing tank in sequence via the first gas storage tank and the first flow meter; The first gas storage tank is used to store the nitrogen gas.

10. The separation system for flue gas from thermal power plants used in the ammonia-soda process for producing soda ash according to claim 1, characterized in that, It also includes a second gas storage tank and a second flow meter; the condensation unit is connected to the mixing tank in sequence via the second gas storage tank and the second flow meter. The second gas storage tank is used to store the carbon dioxide.

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