Separation system for flue gas of thermal power plant for preparing sodium carbonate by ammonia-alkali method

Abstract

The invention provides a thermal power plant flue gas separation system used for preparing sodium carbonate through an ammonia-alkali method, the thermal power plant flue gas separation system comprises a flue gas pipeline, an absorption tower, a first branch pipe, a desorption tower, a heat exchanger, a membrane assembly, a gas mixing tank and a condensation unit, the flue gas pipeline is connected with a lower inlet of the absorption tower, a bottom outlet of the absorption tower is connected with a first end of the first branch pipe, and a second end of the first branch pipe is connected with a second end of the desorption tower; the second end of the first branch pipe is connected with an upper inlet of the desorption tower; the heat exchanger is arranged on the first branch pipe; the input end of the membrane assembly is connected with a top outlet of the absorption tower, and the output end of the membrane assembly is connected with the gas mixing tank; a top outlet of the desorption tower is connected with the condensation unit, and a first output end of the condensation unit is connected with the gas mixing tank. The method has the technical effects that the product gas with the CO2 concentration of 42% required by the alkali production equipment can be obtained, so that the CO2 in the coal-fired flue gas can be consumed, and the method has good application value.

Description

Technical Field

[0001] The invention belongs to the technical field of flue gas treatment in thermal power plants, and in particular relates to a flue gas separation system for thermal power plants producing soda ash by an ammonia-soda process. Background Art

[0002] Currently, many thermal power plants are preparing to build carbon capture devices, aiming to effectively reduce carbon emissions from coal-fired power units and help achieve green transformation in the coal-fired power sector. However, how to dispose of CO2 after it is captured has become a bottleneck problem that hinders the large-scale development of carbon capture and needs to be solved urgently.

[0003] In addition, the raw materials used for soda ash produced by the ammonia-soda process include brine, quicklime, coal and ammonia. The CO2 gas required in the process of preparing soda ash is produced by calcining and decomposing limestone and coal, which requires additional energy consumption to calcine limestone.

[0004] Therefore, there is an urgent need for a separation system for the flue gas of thermal power plants used to produce soda ash using the ammonia-soda process, which can capture and treat the CO2 in the flue gas of thermal power plants and use it in the alkali 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 solve at least one of the technical problems existing in the prior art and provide a new technical solution for a flue gas separation system of a thermal power plant for producing soda ash by an ammonia-soda process.

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

[0007] A flue gas pipeline, an absorption tower, a first branch pipe, a desorption tower and a heat exchanger, wherein 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 arranged on the first branch pipe;

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

[0009] A condensing unit, the top outlet of the desorption tower is connected to the condensing unit, and the first output end of the condensing unit is connected to the gas mixing tank;

[0010] The flue gas inputted from the lower inlet of the absorption tower contacts the absorbent inputted from the upper inlet of the absorption tower in countercurrent to form a first gas flow and a rich liquid;

[0011] The first gas stream enters the membrane assembly from the top outlet of the absorption tower, and is separated by the membrane assembly to form nitrogen gas which enters the gas mixing tank;

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

[0013] Optionally, the separation system for flue gas from a thermal power plant for producing soda ash by the ammonia-soda process further includes a second branch pipe and a reboiler, wherein 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 arranged on the second branch pipe;

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

[0015] Optionally, the separation system for flue gas from a thermal power plant for producing soda ash by the ammonia-soda process further comprises 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 liquid in the reboiler is extracted to heat the rich liquid at the heat exchanger, and the cooled lean liquid enters the absorption tower through the upper inlet of the absorption tower.

[0018] Optionally, the separation system for flue gas from a thermal power plant for producing soda ash by the ammonia-soda process further comprises a compressor, wherein the compressor is used to compress the first airflow;

[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 airflow is compressed in the compressor and then separated by passing through the membrane module.

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

[0022] Optionally, the separation system for flue gas from a thermal power plant for producing soda ash using the ammonia-soda process further includes a lean liquid pump, which is arranged on the third branch pipe and located between the reboiler and the heat exchanger.

[0023] Optionally, the separation system for flue gas from a thermal power plant for producing soda ash by the ammonia-soda process further includes a booster pump and a lean liquid cooler;

[0024] The boost pump and the lean liquid cooler are both arranged on the third branch pipe, and the boost pump is located between the heat exchanger and the absorption tower, and the lean liquid cooler is located between the boost pump and the absorption tower.

[0025] Optionally, the condensing 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 arranged on the fourth branch pipe;

[0027] The second air flow passes through the first condenser and the second condenser in sequence to form carbon dioxide and condensed water, and the condensed water refluxes into the desorption tower under the action of the reflux pump.

[0028] Optionally, the separation system for flue gas from a thermal power plant for producing soda ash by the ammonia-soda process further comprises a first gas storage tank and a first flow meter; the membrane assembly is connected to the gas mixing tank in sequence through the first gas storage tank and the first flow meter;

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

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

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

[0032] A technical effect of the present invention is:

[0033] In an embodiment of the present application, the separation system of the flue gas of a thermal power plant used for the production of soda ash by the ammonia-soda process economically and efficiently processes and captures CO2 in the flue gas of the thermal power plant by coupling the chemical absorption method and the membrane separation method. On the one hand, the chemical absorption method is used to capture and separate carbon dioxide in the flue gas of the thermal power plant to obtain carbon dioxide with a concentration of 99%. On the other hand, a membrane component is used to separate the first airflow (i.e., purified gas) at the top outlet of the absorption tower, so that the concentration of nitrogen in the first airflow is increased from 93% to more than 98%. Then, the high-concentration nitrogen and carbon dioxide are mixed to obtain a product gas with a CO2 concentration of 42% required by the alkali-making equipment, thereby realizing the consumption of CO2 in coal-fired flue gas, which has good application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic structural diagram of a system for separating flue gas from a thermal power plant for producing soda ash using the ammonia-soda process according to an embodiment of the present invention;

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

[0036] In the figure: 1. flue gas duct; 2. absorption tower; 3. first branch pipe; 4. desorption tower; 5. heat exchanger; 6. membrane assembly; 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 liquid pump; 14. lean liquid pump; 15. first gas storage tank; 16. first flow meter; 17. second gas storage tank; 18. second flow meter; 19. booster pump; 20. lean liquid cooler. DETAILED DESCRIPTION

[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 of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application.

[0038] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0039] The term "first" or "second" in the specification and claims of this application may include one or more of the features explicitly or implicitly. In the description of this application, unless otherwise specified, "plurality" means two or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally means that the objects connected before and after are in an "or" relationship.

[0040] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0041] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0042] According to the first aspect of the present invention, referring to FIG. Figure 2 , provides a separation system for flue gas from a thermal power plant for producing soda ash by an ammonia-soda process, comprising:

[0043] A flue gas pipeline 1, an absorption tower 2, a first branch pipe 3, a desorption tower 4 and a heat exchanger 5, wherein the flue gas pipeline 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 arranged on the first branch pipe 3;

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

[0045] A condensation unit, 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 gas mixing tank 7;

[0046] The flue gas inputted from the lower inlet of the absorption tower 2 is countercurrently contacted with the absorbent inputted 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 assembly 6 from the top outlet of the absorption tower 2, and is separated by the membrane assembly 6 to form nitrogen gas which enters the gas 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 enters the desorption tower 4 after being heated by the heat exchanger 5. The rich liquid forms a second gas flow and a lean liquid after being desorbed in the desorption tower 4. 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 condensed water. The carbon dioxide enters the mixing tank 7 and mixes with nitrogen to form a product gas with a preset ratio for producing soda ash by the ammonia-soda process.

[0049] In the embodiment of the present application, the separation system of the flue gas of the thermal power plant used for the production of soda ash by the ammonia-soda process economically and efficiently processes and captures CO2 in the flue gas of the thermal power plant by coupling the chemical absorption method and the membrane separation method. On the one hand, the chemical absorption method is used to capture and separate the carbon dioxide in the flue gas of the thermal power plant to obtain a carbon dioxide with a concentration of 99%. On the other hand, the membrane component 6 is used to separate the first airflow (i.e., the purified gas) at the top outlet of the absorption tower 2, so that the concentration of nitrogen in the first airflow is increased from 93% to more than 98%. Then, the high-concentration nitrogen and carbon dioxide are mixed to obtain a product gas with a CO2 concentration of 42% required by the alkali-making equipment, thereby realizing the consumption of CO2 in the coal-fired flue gas, which has good application value.

[0050] It should be noted that in order to match the CO2 capture process in the flue gas of a thermal power plant with the ammonia-soda process, it is necessary to master the supply and demand relationship between the flue gas of the thermal power plant and the raw gas for making alkali by the ammonia-soda process. Among them, the volume ratio of the flue gas components of a thermal power plant is usually 81% N2, 13% CO2 and 6% O2. The requirements of the ammonia-soda process for the product gas (that is, CO2 raw gas) are: 42% CO2, 57% N2 and less than 1% O2. The product gas prepared in this application for making soda ash by the ammonia-soda process can meet the process requirements of the ammonia-soda process, thereby realizing the absorption of carbon dioxide in coal-fired flue gas and having good application value.

[0051] In the embodiment of the present application, the working principle of the separation system of the flue gas of the thermal power plant used for producing soda ash by the ammonia-soda process is as follows: the flue gas of the thermal power plant to be treated by the coupled chemical absorption method (the concentration of CO2 is 13%, the concentration of O2 is 6%, and the concentration of N2 is 81%) enters the absorption tower 2 from the lower inlet of the absorption tower 2, and is countercurrently contacted with the absorbent pumped into 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 (that is, the first airflow) is discharged from the top outlet of the absorption tower 2 and sent to the membrane component 6 through the compressor 12. After separation by the membrane component 6, nitrogen-rich gas (N2 with a concentration of 98%) and oxygen-rich gas are generated, wherein the oxygen-rich gas is directly discharged into the atmosphere, and the nitrogen-rich gas (that is, nitrogen) enters the first gas storage tank 15, and after the flow rate is adjusted by the first flowmeter 16, it enters the mixing tank 7 to wait for mixing. The rich liquid discharged from the bottom outlet of the absorption tower 2 is pumped into the heat exchanger 5 through the rich liquid pump 13, and after heat exchange and temperature rise, it enters the desorption tower 4 from the upper inlet of the desorption tower 4 to desorb carbon dioxide. The second airflow (i.e., the desorption airflow) generated in the desorption tower 4 is discharged from the top outlet of the desorption tower 4 and enters the first condenser 81 and the second condenser 82 (the second condenser 82 can be a reflux condenser), respectively generating CO2 gas and condensed water with a concentration of 99%, and the condensed water flows back to the desorption tower 4 from the condensed water inlet of the desorption tower 4. The lean liquid discharged from the bottom outlet of the desorption tower 4 enters the desorption tower 4 through the reboiler 10 to provide heat for the desorption process; part of the lean liquid in the reboiler 10 enters the heat exchanger 5 through the lean liquid pump 14, and the lean liquid is further cooled and pressurized to about 40°C to become an absorbent and enter the absorption tower 2 to absorb carbon dioxide.

[0052] Finally, the CO2 gas with a concentration of 99% enters the second gas storage tank 17, and 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 (the concentration of CO2 is 42% and the concentration of N2 is 58%).

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

[0056] Optionally, the separation system for flue gas from a thermal power plant for producing soda ash by the ammonia-soda process further 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 liquid in the reboiler 10 is extracted to heat the rich liquid at the heat exchanger 5 , and the cooled lean liquid enters the absorption tower 2 through the upper inlet of the absorption tower 2 .

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

[0060] Optionally, the separation system for flue gas from a thermal power plant for producing soda ash by the ammonia-soda process further comprises a compressor 12, wherein the compressor 12 is used to compress the first airflow;

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

[0062] The first airflow is compressed in the compressor 12 and then passes through the membrane module 6 for separation.

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

[0064] Optionally, the separation system for flue gas from a thermal power plant for producing soda ash using the ammonia-soda process further includes a rich liquid pump 13 , which is disposed on the first branch pipe 3 and is 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 a thermal power plant for producing soda ash using the ammonia-soda process further includes a lean liquid pump 14 , which is disposed in the third branch pipe 11 and is located 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 a thermal power plant for producing soda ash by the ammonia-soda process further includes a booster pump 19 and a lean liquid cooler 20;

[0069] The boost pump 19 and the lean liquid cooler 20 are both arranged in the third branch pipe 11 , and the boost pump 19 is located between the heat exchanger 5 and the absorption tower 2 , and the lean liquid cooler 20 is located between the boost pump 19 and the absorption tower 2 .

[0070] In the above embodiment, the booster pump 19 and the lean liquid cooler 20 can better ensure that the lean liquid at a preset temperature and a preset pressure is transported to the absorption tower 2, thereby better realizing the recycling of the absorbent.

[0071] Optionally, the condensing 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 may 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 arranged on the fourth branch pipe 84;

[0073] The second airflow passes through the first condenser 81 and the second condenser 82 in sequence to form carbon dioxide and condensed water. The condensed water refluxes into the desorption tower 4 under the action of the reflux pump 83 .

[0074] In the above-mentioned embodiment, the condensation unit structure is reasonably designed, which not only helps to obtain high-concentration carbon dioxide, but also can realize the recycling of condensed water, thus saving water resources to a good extent.

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

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

[0077] In the above embodiment, it is helpful to accurately adjust the amount of nitrogen entering the gas mixing tank 7, so as to achieve accurate mixing of nitrogen and carbon dioxide, and better ensure that the product gas can be used for the production of soda ash by the ammonia-soda process.

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

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

[0080] In the above embodiment, it is helpful to accurately adjust the amount of carbon dioxide entering the gas mixing tank 7, so as to achieve accurate mixing of carbon dioxide and nitrogen, and better ensure that the product gas can be used for the production of soda ash by the ammonia-soda process.

[0081] In a specific embodiment, after the pollutant removal and dust removal treatment, the boiler flue gas is cooled to 40°C by a water cooler, and then enters the absorption tower 2 from the lower entrance of the absorption tower 2, and reacts with the absorbent in the absorption tower 2 in a reverse contact manner, and then passes through the top water washing tower of the absorption tower 2 for cyclic washing, and after removing part of the volatilized absorbent, leaves the absorption tower 2 from the top outlet of the absorption tower 2. At the same time, the absorbent is sprayed from top to bottom at the top of the absorption tower 2, reacts with CO2 to form a rich liquid, and is discharged from the bottom outlet of the absorption tower 2. After the rich liquid is heated in the heat exchanger 5, it enters the desorption tower 4 (also known as the regeneration tower), releases CO2 under the action of heat, and completes the regeneration process of the absorbent. The regenerated CO2 is extracted by the water vapor generated in the desorption tower 4 and leaves the desorption tower 4, and high-purity CO2 is obtained by condensation separation. The water vapor in the regeneration process comes from the reboiler 10, and its heat source is usually the low-pressure cylinder steam of the power plant. The regenerated absorbent (i.e., lean liquid) is discharged from the bottom outlet of the desorption tower 4, cooled to 40°C by the liquid replenishment, liquid heat exchanger 5 and lean liquid cooler 20, and re-enters the absorption tower 2 to circulate and absorb CO2. The lean liquid can also be stored in a storage tank arranged in the third branch pipe 11.

[0082] Furthermore, the main components of the first gas flow (i.e., purified gas) at the top outlet of the absorption tower 2 are N2 with a concentration of 93%, O2 with a concentration of 6%, and a small amount of CO2. A portion of the gas is extracted from the first gas flow at the top outlet of the absorption tower 2, and after dehydration, it enters the compressor 12 to be pressurized to 8.5 bar and is sent to the membrane assembly 6 (i.e., the membrane separation system). Due to the different selectivity of the membrane assembly 6 for N2 and O2 gases, the N2 / O2 mixed gas will be separated in the membrane separation system to obtain two outlet gas flows, one of which is a N2-enriched gas flow and the other is an O2-enriched gas flow.

[0083] The N2-enriched gas flow (i.e., nitrogen) of the membrane module 6 is mixed with the CO2 gas flow (i.e., carbon dioxide) of the chemical absorption system and sent to the alkali production process. In the alkali production process, the waste residue white mud can be transported to the desulfurization system of the thermal power plant through a pipeline for use. The calcium oxide and a small amount of sodium hydroxide contained in the white mud can be used as a desulfurization absorbent to reduce the desulfurization operation cost.

[0084] In the embodiment of the present application, the separation system for the flue gas of a thermal power plant used for producing soda ash by the ammonia-soda process can effectively decarbonize the flue gas of the thermal power plant, and use the treated CO2 in the subsequent ammonia-soda process for producing soda ash. It is a method that not only reduces the CO2 production cost of the alkali manufacturer, but also solves the problem of carbon capture and resource utilization of coal-fired power generation, and can realize the cascade utilization of waste heat from thermal power plants, improve energy utilization efficiency, reduce the operating cost of the carbon capture system, achieve a win-win situation, and effectively promote the development of the circular economy.

[0085] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill 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 a thermal power plant for producing soda ash by an ammonia-soda process, characterized in that: include: A flue gas pipeline, an absorption tower, a first branch pipe, a desorption tower and a heat exchanger, wherein 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 arranged on the first branch pipe; A membrane assembly and a gas mixing tank, wherein the input end of the membrane assembly is connected to the top outlet of the absorption tower, and the output end of the membrane assembly is connected to the gas mixing tank; A condensing unit, the top outlet of the desorption tower is connected to the condensing unit, and the first output end of the condensing unit is connected to the gas mixing tank; The flue gas inputted from the lower inlet of the absorption tower contacts the absorbent inputted from the upper inlet of the absorption tower in countercurrent to form a first gas flow and a rich liquid; The first gas stream enters the membrane assembly from the top outlet of the absorption tower, and is separated by the membrane assembly to form nitrogen gas which enters the gas mixing tank; The rich liquid is discharged from the bottom outlet of the absorption tower into the first branch pipe, and enters the desorption tower after being heated by the heat exchanger. The rich liquid forms a second gas flow and a lean liquid after being desorbed in the desorption tower. 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 condensed water. The carbon dioxide enters the mixing tank and mixes with nitrogen to form a product gas with a preset ratio for producing soda ash by the ammonia-soda process.

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

3. The separation system of flue gas from a thermal power plant for producing soda ash by the ammonia-soda process 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 liquid in the reboiler is extracted to heat the rich liquid at the heat exchanger, and the cooled lean liquid enters the absorption tower through the upper inlet of the absorption tower.

4. The separation system of flue gas from a thermal power plant for producing soda ash by the ammonia-soda process according to claim 3 is characterized in that: Also included is a compressor, the compressor being used to compress 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 airflow is compressed in the compressor and then separated by passing through the membrane module.

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

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

7. The separation system of flue gas from a thermal power plant for producing soda ash by the ammonia-soda process according to claim 6, characterized in that: Also includes a boost pump and lean liquid cooler; The boost pump and the lean liquid cooler are both arranged on the third branch pipe, and the boost pump is located between the heat exchanger and the absorption tower, and the lean liquid cooler is located between the boost pump and the absorption tower.

8. The separation system of flue gas from a thermal power plant for producing soda ash by the ammonia-soda process according to claim 7, characterized in that: The condensing unit comprises 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 arranged on the fourth branch pipe; The second air flow passes through the first condenser and the second condenser in sequence to form carbon dioxide and condensed water, and the condensed water refluxes into the desorption tower under the action of the reflux pump.

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

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

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