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

Abstract

The invention provides a separation system and method for flue gas of a thermal power plant for preparing sodium carbonate through an ammonia-alkali method, and the separation system comprises a first adsorption unit, a second adsorption unit, a first three-way valve, a membrane assembly, a condenser and a gas mixing tank, a first outlet of the first three-way valve is connected with the first adsorption unit, and a second outlet of the first three-way valve is connected with the second adsorption unit; wherein the first adsorption unit and the second adsorption unit are both used for adsorbing carbon dioxide; a first outlet of the first adsorption unit is connected with a membrane assembly, a second outlet of the first adsorption unit is connected with a condenser, a first outlet of the second adsorption unit is connected with the membrane assembly, and a second outlet of the second adsorption unit is connected with the condenser; and the outlet of the membrane component and the condenser are respectively connected with the gas mixing tank. The device has the technical effect that the carbon dioxide in the flue gas of the thermal power plant can be economically and efficiently captured and treated.

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 system and method for separating flue gas in thermal power plants for producing soda ash by an ammonia-soda process. Background Art

[0002] In order to promote the construction of ecological civilization, many thermal power plants are currently 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 carbon dioxide 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 in the production of soda ash by the ammonia-soda process include brine, quicklime, coal and ammonia. The carbon dioxide gas required in the process of preparing soda ash is produced by the calcination and decomposition of limestone and coal. This not only requires additional energy consumption to calcine limestone, but also the carbon dioxide produced in the process of soda ash production is not conducive to the implementation of the dual carbon target plan.

[0004] Therefore, there is an urgent need for a separation system and method for the flue gas of thermal power plants used in the production of soda ash by the ammonia-soda process, which can capture and treat the carbon dioxide in the flue gas of thermal power plants and use it in the alkali production process, which can not only further reduce the resource consumption in the production process, but also improve the resource utilization efficiency of carbon dioxide. 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 system and method for separating flue gas from 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 first adsorption unit, a second adsorption unit and a first three-way valve, wherein the inlet of the first three-way valve is connected to the flue gas duct, the first outlet of the first three-way valve is connected to the first adsorption unit, and the second outlet of the first three-way valve is connected to the second adsorption unit; wherein the first adsorption unit and the second adsorption unit are both used for adsorbing carbon dioxide;

[0008] A membrane assembly and a condenser, wherein the first outlet of the first adsorption unit is connected to the membrane assembly, the second outlet of the first adsorption unit is connected to the condenser, and the first outlet of the second adsorption unit is connected to the membrane assembly, and the second outlet of the second adsorption unit is connected to the condenser;

[0009] A gas mixing tank, the outlet of the membrane assembly and the condenser are respectively connected to the gas mixing tank;

[0010] In the first state, when the flue gas passes through the first adsorption unit or the second adsorption unit, a first airflow is formed, and the first airflow is separated by the membrane module to form an oxygen-rich airflow and a nitrogen-rich airflow, and the nitrogen-rich airflow enters the gas mixing tank;

[0011] In the second state, the carbon dioxide adsorbed by the first adsorption unit or the second adsorption unit is desorbed and enters the gas mixing tank through the condenser, and the nitrogen in the nitrogen-rich gas flow is mixed with the carbon dioxide in a preset ratio to form a product gas for producing soda ash by the ammonia-soda process.

[0012] 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 three-way valve and a third three-way valve;

[0013] The first inlet of the second three-way valve is connected to the outlet of the first adsorption unit, the first outlet of the second three-way valve is connected to the membrane module, and the second outlet of the second three-way valve is connected to the condenser;

[0014] The first inlet of the third three-way valve is connected to the outlet of the second adsorption unit, the first outlet of the third three-way valve is connected to the membrane assembly, and the second outlet of the third three-way valve is connected to the condenser.

[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 compressor, wherein the compressor is used to compress the first airflow;

[0016] The first outlet of the second three-way valve and the first outlet of the third three-way valve are respectively connected to the compressor, and the compressor is connected to the membrane assembly;

[0017] The first airflow is compressed in the compressor and then separated by passing through the membrane module.

[0018] 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, a first flow meter, a second gas storage tank and a second 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, and the condenser is connected to the gas mixing tank through the second gas storage tank and the second flow meter in sequence;

[0019] The first gas storage tank is used to store the nitrogen-rich gas flow; the second gas storage tank is used to store the carbon dioxide.

[0020] Optionally, the separation system for flue gas from a thermal power plant for producing soda ash by the ammonia-soda process further comprises a three-way pipe;

[0021] The first inlet of the three-way pipe is connected to the second outlet of the second three-way valve, the second inlet of the three-way pipe is connected to the second outlet of the third three-way valve, and the outlet of the three-way pipe is connected to the condenser.

[0022] Optionally, the first adsorption unit is provided with an inlet at the bottom and an outlet at the top.

[0023] Optionally, the carbon dioxide desorption method of the first adsorption unit or the second adsorption unit is heating.

[0024] Optionally, the condenser has a first outlet and a second outlet, the first outlet of the condenser is connected to the gas mixing tank, and the second outlet of the condenser is used to output condensed water.

[0025] Optionally, the preset ratio is: the volume ratio of the carbon dioxide is 42%, and the volume ratio of the nitrogen is 58%.

[0026] According to a second aspect of the present invention, there is provided a method for separating flue gas from a thermal power plant for producing soda ash by an ammonia-soda process, comprising the following steps:

[0027] Step S1, the flue gas to be treated from the thermal power plant enters the first adsorption unit through the first three-way valve, and the first adsorption unit adsorbs carbon dioxide in the flue gas to form a first airflow; the first airflow is separated by the membrane assembly to form an oxygen-rich airflow and a nitrogen-rich airflow, and the nitrogen-rich airflow enters the gas mixing tank;

[0028] Step S2, when the adsorbent in the first adsorption unit is in a saturated state of carbon dioxide adsorption, the flue gas enters the second adsorption unit through the first three-way valve, and the second adsorption unit adsorbs the carbon dioxide in the flue gas to form a first airflow; the first airflow is separated by the membrane assembly to form an oxygen-rich airflow and a nitrogen-rich airflow, and the nitrogen-rich airflow enters the gas mixing tank;

[0029] At the same time, the carbon dioxide adsorbed by the first adsorption unit is desorbed, and the carbon dioxide enters the gas mixing tank through the condenser, and the nitrogen in the nitrogen-rich gas flow is mixed with the carbon dioxide according to a preset ratio to form a product gas for producing soda ash by the ammonia-soda process;

[0030] Step S3, when the adsorbent in the second adsorption unit is in a saturated state of carbon dioxide adsorption, the flue gas enters the first adsorption unit through the first three-way valve, and the first adsorption unit adsorbs carbon dioxide in the flue gas to form a first airflow; the first airflow is separated by the membrane assembly to form an oxygen-rich airflow and a nitrogen-rich airflow, and the nitrogen-rich airflow enters the gas mixing tank;

[0031] At the same time, the carbon dioxide adsorbed by the second adsorption unit is desorbed, and the carbon dioxide enters the gas mixing tank through the condenser, and the nitrogen in the nitrogen-rich gas flow is mixed with the carbon dioxide according to a preset ratio to form a product gas for producing soda ash by the ammonia-soda process;

[0032] Step S4, when the carbon dioxide adsorbed by the first adsorption unit is desorbed, repeat step S1; when the carbon dioxide adsorbed by the second adsorption unit is desorbed, repeat step S2.

[0033] A technical effect of the present invention is:

[0034] In an embodiment of the present application, the solid adsorption carbon dioxide method and the membrane separation method are coupled to capture and treat carbon dioxide in the flue gas of a thermal power plant in an economical and efficient manner. First, the solid adsorption carbon dioxide method is used to capture and separate carbon dioxide in the flue gas of a thermal power plant, and a 99% concentration of carbon dioxide can be obtained. Then, a membrane assembly is used to separate the purified gas (that is, the first airflow) at the outlet of the first adsorption unit and the second adsorption unit, so that the nitrogen in the purified gas is increased from 93% to more than 98%. Finally, the high-concentration nitrogen and carbon dioxide are mixed to obtain the product gas required for the alkali making equipment. The volume ratio of carbon dioxide in the product gas is 42%, thereby realizing the absorption of carbon dioxide in the coal-fired flue gas, which has good application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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;

[0036] 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.

[0037] In the figure: 1. first adsorption unit; 2. second adsorption unit; 3. first three-way valve; 4. flue gas duct; 5. membrane assembly; 6. condenser; 7. mixing tank; 8. second three-way valve; 9. third three-way valve; 10. compressor; 11. first gas storage tank; 12. first flow meter; 13. second gas storage tank; 14. second flow meter; 15. three-way pipe. DETAILED DESCRIPTION

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] According to a first aspect of the present invention, see Figure 1 and Figure 2 , provides a separation system for flue gas from a thermal power plant for producing soda ash by an ammonia-soda process, comprising:

[0044] A first adsorption unit 1, a second adsorption unit 2 and a first three-way valve 3, wherein the inlet of the first three-way valve 3 is connected to the flue gas duct 4, the first outlet of the first three-way valve 3 is connected to the first adsorption unit 1, and the second outlet of the first three-way valve 3 is connected to the second adsorption unit 2; wherein the first adsorption unit 1 and the second adsorption unit 2 are both used for adsorbing carbon dioxide;

[0045] A membrane assembly 5 and a condenser 6, wherein the first outlet of the first adsorption unit 1 is connected to the membrane assembly 5, the second outlet of the first adsorption unit 1 is connected to the condenser 6, and the first outlet of the second adsorption unit 2 is connected to the membrane assembly 5, and the second outlet of the second adsorption unit 2 is connected to the condenser 6;

[0046] A gas mixing tank 7, an outlet of the membrane assembly 5 and the condenser 6 are respectively connected to the gas mixing tank 7;

[0047] In the first state, when the flue gas passes through the first adsorption unit 1 or the second adsorption unit 2, a first airflow is formed, and the first airflow is separated by the membrane assembly 5 to form an oxygen-rich airflow and a nitrogen-rich airflow, and the nitrogen-rich airflow enters the mixing tank 7; wherein, in the first state, the adsorbent in the first adsorption unit 1 or the second adsorption unit 2 is in an unsaturated state of carbon dioxide adsorption;

[0048] In the second state, the carbon dioxide adsorbed by the first adsorption unit 1 or the second adsorption unit 2 is desorbed and enters the gas mixing tank 7 through the condenser 6, and the nitrogen in the nitrogen-rich gas flow is mixed with the carbon dioxide according to a preset ratio to form a product gas for producing soda ash by the ammonia-soda process. The first state is that the adsorbent in the first adsorption unit 1 or the second adsorption unit 2 is in a saturated state of carbon dioxide adsorption.

[0049] In an embodiment of the present application, the solid adsorption carbon dioxide method and the membrane separation method are coupled to capture and treat carbon dioxide in the flue gas of a thermal power plant economically and efficiently. First, the solid adsorption carbon dioxide method is used to capture and separate carbon dioxide in the flue gas of a thermal power plant, and a 99% concentration of carbon dioxide can be obtained. Then, the membrane assembly 5 is used to separate the purified gas (that is, the first airflow) at the outlet of the first adsorption unit 1 and the second adsorption unit 2, so that the nitrogen in the purified gas is increased from 93% to more than 98%. Finally, the high-concentration nitrogen and carbon dioxide are mixed to obtain the product gas required for the alkali making equipment. The volume ratio of carbon dioxide in the product gas is 42%, thereby realizing the absorption of carbon dioxide in 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] Exemplarily, the outlet of the gas mixing tank 7 is connected to the product gas inlet of the alkali production equipment.

[0052] 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 three-way valve 8 and a third three-way valve 9;

[0053] The first inlet of the second three-way valve 8 is connected to the outlet of the first adsorption unit 1, the first outlet of the second three-way valve 8 (which serves as the first outlet of the first adsorption unit 1) is connected to the membrane assembly 5, and the second outlet of the second three-way valve 8 (which serves as the first outlet of the second adsorption unit 2) is connected to the condenser 6;

[0054] The first inlet of the third three-way valve 9 is connected to the outlet of the second adsorption unit 2, the first outlet of the third three-way valve 9 (which serves as the first outlet of the second adsorption unit 2) is connected to the membrane assembly 5, and the second outlet of the third three-way valve 9 (which serves as the first outlet of the second adsorption unit 2) is connected to the condenser 6.

[0055] In the above embodiment, the first adsorption unit 1 can smoothly output carbon dioxide or the first airflow through the second three-way valve 8, and the second adsorption unit 2 can smoothly output carbon dioxide or the first airflow through the third three-way valve 9, and the operation is simple.

[0056] 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 10, wherein the compressor 10 is used to compress the first airflow;

[0057] The first outlet of the second three-way valve 8 and the first outlet of the third three-way valve 9 are respectively connected to the compressor 10, and the compressor 10 is connected to the membrane assembly 5;

[0058] The first airflow is compressed in the compressor 10 and then passes through the membrane module 5 for separation.

[0059] In the above embodiment, the compressor 10 can effectively compress the first airflow, thereby facilitating the membrane module 5 to separate the compressed first airflow.

[0060] 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 11, a first flow meter 12, a second gas storage tank 13 and a second flow meter 14; the membrane assembly 5 is connected to the gas mixing tank 7 through the first gas storage tank 11 and the first flow meter 12 in sequence, and the condenser 6 is connected to the gas mixing tank 7 through the second gas storage tank 13 and the second flow meter 14 in sequence;

[0061] The first gas storage tank 11 is used to store the nitrogen-rich gas flow; the second gas storage tank 13 is used to store the carbon dioxide.

[0062] In the above embodiment, it is helpful to adjust the flow rate of nitrogen and the flow rate of carbon dioxide in the nitrogen-rich gas flow, thereby helping to accurately mix nitrogen and carbon dioxide according to a preset ratio to form a product gas for producing soda ash by the ammonia-soda process.

[0063] Optionally, the separation system for flue gas from a thermal power plant for producing soda ash by the ammonia-soda process further includes a three-way pipe 15;

[0064] The first inlet of the three-way pipe 15 is connected to the second outlet of the second three-way valve 8 , the second inlet of the three-way pipe 15 is connected to the second outlet of the third three-way valve 9 , and the outlet of the three-way pipe 15 is connected to the condenser 6 .

[0065] In the above embodiment, the design of the three-way pipe 15 is relatively reasonable, which helps to optimize the pipeline connection of the separation system of the flue gas of the thermal power plant used for producing soda ash by the ammonia-soda process.

[0066] Optionally, the first adsorption unit 1 is provided with an inlet at the bottom and an outlet at the top, which helps the first adsorption unit 1 to adsorb carbon dioxide in the flue gas. Exemplarily, the second adsorption unit 2 is provided with an inlet at the bottom and an outlet at the top.

[0067] Optionally, the carbon dioxide desorption method of the first adsorption unit 1 or the second adsorption unit 2 is heating, which makes the carbon dioxide desorption method relatively simple and easy to operate.

[0068] Optionally, the condenser 6 has a first outlet and a second outlet, the first outlet of the condenser 6 is connected to the gas mixing tank 7, and the second outlet of the condenser 6 is used to output condensed water. The condenser 6 is used to condense carbon dioxide and separate condensed water, thereby better ensuring the purity of carbon dioxide.

[0069] Optionally, the preset ratio is: the volume ratio of the carbon dioxide is 42%, and the volume ratio of the nitrogen is 58%. This enables the product gas to meet the requirements of the alkali production process, thereby achieving the absorption of carbon dioxide in coal-fired flue gas and having good application value.

[0070] According to a second aspect of the present invention, there is provided a method for separating flue gas from a thermal power plant for producing soda ash by an ammonia-soda process, comprising the following steps:

[0071] Step S1, the flue gas to be treated from the thermal power plant enters the first adsorption unit 1 through the first three-way valve 3, and the first adsorption unit 1 adsorbs the carbon dioxide in the flue gas to form a first airflow (the volume ratio of O2 is 7%, and the volume ratio of N2 is 93%); the first airflow is separated by the membrane assembly 5 to form an oxygen-rich airflow and a nitrogen-rich airflow, and the nitrogen-rich airflow enters the gas mixing tank 7;

[0072] Step S2, when the adsorbent in the first adsorption unit 1 is in a saturated state of carbon dioxide adsorption, the flue gas enters the second adsorption unit 2 through the first three-way valve 3, and the second adsorption unit 2 adsorbs carbon dioxide in the flue gas to form a first airflow; the first airflow is separated by the membrane assembly 5 to form an oxygen-rich airflow and a nitrogen-rich airflow (the volume ratio of N2 is 98%), the nitrogen-rich airflow enters the mixing tank 7, and the oxygen-rich airflow is directly discharged into the atmosphere; for example, the first airflow is compressed by the compressor 10 and then enters the membrane assembly 5;

[0073] At the same time, the carbon dioxide adsorbed by the first adsorption unit 1 is desorbed, and the carbon dioxide enters the gas mixing tank 7 through the condenser 6, and the nitrogen in the nitrogen-rich gas flow is mixed with the carbon dioxide according to a preset ratio to form a product gas for producing soda ash by the ammonia-soda process;

[0074] Step S3, when the adsorbent in the second adsorption unit 2 is in a saturated state of carbon dioxide adsorption, the flue gas enters the first adsorption unit 1 through the first three-way valve 3, and the first adsorption unit 1 adsorbs carbon dioxide in the flue gas to form a first airflow; the first airflow is separated by the membrane assembly 5 to form an oxygen-rich airflow and a nitrogen-rich airflow, and the nitrogen-rich airflow enters the mixing tank 7;

[0075] At the same time, the carbon dioxide adsorbed by the second adsorption unit 2 is desorbed, and the carbon dioxide enters the gas mixing tank 7 through the condenser 6, and the nitrogen in the nitrogen-rich gas flow is mixed with the carbon dioxide according to a preset ratio to form a product gas for producing soda ash by the ammonia-soda process;

[0076] Step S4, when the carbon dioxide adsorbed by the first adsorption unit 1 is desorbed, step S1 is repeated; when the carbon dioxide adsorbed by the second adsorption unit 2 is desorbed, step S2 is repeated.

[0077] In the above-mentioned embodiment, the separation method of 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 process of producing soda ash by the ammonia-soda process. It is a method that not only reduces the cost of CO2 production by alkali manufacturers, 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 a circular economy.

[0078] Exemplarily, an adsorption bed is provided in the first adsorption unit 1 or the second adsorption unit 2, and an adsorbent is provided on the adsorption bed. After the flue gas of the boiler is treated with pollutant removal and dust removal, it is cooled to 40°C by a water cooler, and then enters the adsorption bed from the entrance of the first adsorption unit 1 or the second adsorption unit 2, and contacts and reacts with the adsorbent in the adsorption bed. The adsorbent adsorbs CO2, while other gases are released and discharged. After the adsorbent adsorbs CO2 to saturation, it releases CO2 under the action of heat, completing the regeneration process of the adsorbent. The regenerated CO2 gas is separated by the condenser 6 to obtain high-purity CO2. The heat source of the regeneration process is usually the heat exchange of low-pressure cylinder steam in the power plant. After the regenerated adsorbent is cooled to 40°C, it re-enters the next CO2 adsorption process.

[0079] Furthermore, the main components of the outlet purified gas (i.e., the first gas stream) of the first adsorption unit 1 or the second adsorption unit 2 are N2 (93%) and O2 (6%), as well as a small amount of CO2 (1%). A portion of the gas is extracted from the outlet purified gas of the first adsorption unit 1 or the second adsorption unit 2, and after dehydration treatment, enters the compressor 10 to be pressurized to 8.5 bar and is sent to the membrane module 5 (i.e., Figure 2 Since the membrane assembly 5 has different selectivities for N2 and O2 gases, the N2 / O2 mixed gas is separated in the membrane assembly 5 to obtain two outlet gas streams, one of which is a N2-enriched gas stream (i.e., a nitrogen-enriched gas stream) and the other is an O2-enriched gas stream (i.e., an oxygen-enriched gas stream).

[0080] In the embodiment of the present application, the nitrogen-rich gas flow of the membrane assembly 5 is mixed with the CO2 gas flow output by the first adsorption unit 1 or the second adsorption unit 2 (i.e., the solid adsorption system) and sent to the alkali production process. In the alkali production process, the production 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 adsorbent to reduce the desulfurization operation cost.

[0081] 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 first adsorption unit, a second adsorption unit and a first three-way valve, wherein the inlet of the first three-way valve is connected to the flue gas duct, the first outlet of the first three-way valve is connected to the first adsorption unit, and the second outlet of the first three-way valve is connected to the second adsorption unit; wherein the first adsorption unit and the second adsorption unit are both used for adsorbing carbon dioxide; A membrane assembly and a condenser, wherein the first outlet of the first adsorption unit is connected to the membrane assembly, the second outlet of the first adsorption unit is connected to the condenser, and the first outlet of the second adsorption unit is connected to the membrane assembly, and the second outlet of the second adsorption unit is connected to the condenser; A gas mixing tank, the outlet of the membrane assembly and the condenser are respectively connected to the gas mixing tank; In the first state, when the flue gas passes through the first adsorption unit or the second adsorption unit, a first airflow is formed, and the first airflow is separated by the membrane module to form an oxygen-rich airflow and a nitrogen-rich airflow, and the nitrogen-rich airflow enters the gas mixing tank; In the second state, the carbon dioxide adsorbed by the first adsorption unit or the second adsorption unit is desorbed and enters the gas mixing tank through the condenser, and the nitrogen in the nitrogen-rich gas flow is mixed with the carbon dioxide in a preset ratio to form a product gas 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: Also included is a second three-way valve and a third three-way valve; The first inlet of the second three-way valve is connected to the outlet of the first adsorption unit, the first outlet of the second three-way valve is connected to the membrane module, and the second outlet of the second three-way valve is connected to the condenser; The first inlet of the third three-way valve is connected to the outlet of the second adsorption unit, the first outlet of the third three-way valve is connected to the membrane assembly, and the second outlet of the third three-way valve is connected to the condenser.

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: Also included is a compressor, the compressor being used to compress the first airflow; The first outlet of the second three-way valve and the first outlet of the third three-way valve are respectively connected to the compressor, and the compressor is connected to the membrane assembly; The first airflow is compressed in the compressor and then separated by passing through the membrane module.

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: It also includes a first gas storage tank, a first flow meter, a second gas storage tank and a second 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, and the condenser is connected to the gas mixing tank through the second gas storage tank and the second flow meter in sequence; The first gas storage tank is used to store the nitrogen-rich gas flow; the second gas storage tank is used to store the carbon dioxide.

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: Also includes a tee pipe; The first inlet of the three-way pipe is connected to the second outlet of the second three-way valve, the second inlet of the three-way pipe is connected to the second outlet of the third three-way valve, and the outlet of the three-way pipe is connected to the condenser.

6. 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: The first adsorption unit is provided with an inlet at the bottom and an outlet at the top.

7. The separation system of flue gas from a thermal power plant for producing soda ash by the ammonia-soda process according to claim 1 is characterized in that: The carbon dioxide desorption method of the first adsorption unit or the second adsorption unit is heating.

8. 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: The condenser has a first outlet and a second outlet. The first outlet of the condenser is connected to the gas mixing tank, and the second outlet of the condenser is used to output condensed water.

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: The preset ratio is: the volume ratio of the carbon dioxide is 42%, and the volume ratio of the nitrogen is 58%.

10. A method for separating flue gas from a thermal power plant for producing soda ash by an ammonia-soda process, characterized in that: The steps include: Step S1, the flue gas to be treated from the thermal power plant enters the first adsorption unit through the first three-way valve, and the first adsorption unit adsorbs carbon dioxide in the flue gas to form a first airflow; the first airflow is separated by the membrane assembly to form an oxygen-rich airflow and a nitrogen-rich airflow, and the nitrogen-rich airflow enters the gas mixing tank; Step S2, when the adsorbent in the first adsorption unit is in a saturated state of carbon dioxide adsorption, the flue gas enters the second adsorption unit through the first three-way valve, and the second adsorption unit adsorbs the carbon dioxide in the flue gas to form a first airflow; the first airflow is separated by the membrane assembly to form an oxygen-rich airflow and a nitrogen-rich airflow, and the nitrogen-rich airflow enters the gas mixing tank; At the same time, the carbon dioxide adsorbed by the first adsorption unit is desorbed, and the carbon dioxide enters the gas mixing tank through the condenser, and the nitrogen in the nitrogen-rich gas flow is mixed with the carbon dioxide according to a preset ratio to form a product gas for producing soda ash by the ammonia-soda process; Step S3, when the adsorbent in the second adsorption unit is in a saturated state of carbon dioxide adsorption, the flue gas enters the first adsorption unit through the first three-way valve, and the first adsorption unit adsorbs carbon dioxide in the flue gas to form a first airflow; the first airflow is separated by the membrane assembly to form an oxygen-rich airflow and a nitrogen-rich airflow, and the nitrogen-rich airflow enters the gas mixing tank; At the same time, the carbon dioxide adsorbed by the second adsorption unit is desorbed, and the carbon dioxide enters the gas mixing tank through the condenser, and the nitrogen in the nitrogen-rich gas flow is mixed with the carbon dioxide according to a preset ratio to form a product gas for producing soda ash by the ammonia-soda process; Step S4, when the carbon dioxide adsorbed by the first adsorption unit is desorbed, repeat step S1; when the carbon dioxide adsorbed by the second adsorption unit is desorbed, repeat step S2.

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