A method for directly circulating and fixing carbon dioxide in flue gas using alkaline solid waste semi-dry method

Abstract

A method for directly recycling and fixing carbon dioxide in flue gas by a semi-dry method using alkaline solid waste, which relates to a method for fixing carbon dioxide in flue gas. In the present invention, alkaline solid waste is fed into a reaction tank, and then ammonium chloride solution is used as the circulating liquid. The circulating liquid is mixed with the alkaline solid waste. After heating, ammonium chloride and water decompose and gasify to produce hydrogen chloride, ammonia, and water vapor. The water vapor wets the surface of the upper-layer alkaline solid waste, enabling the extraction of calcium ions from the alkaline solid waste to activate it. Subsequently, CO2 is introduced into the reaction tank, and the activated calcium ions will react with CO2 to form calcium carbonate. Ammonia and chloride ions and ammonium in a humid environment will regenerate ammonium chloride. The present invention relies on the phase change of ammonium chloride to cause its migration and decomposition, and on this basis, activates alkaline solid waste and captures CO2 in flue gas, which can solve the problems of mass transfer limitation and high energy consumption in the conventional direct dry method, as well as the problems of acid extraction agent, water consumption, and the inability to recycle the alkalizing agent in the indirect method, resulting in a large amount of waste liquid.

Description

Technical Field

[0001] The invention relates to a method for fixing carbon dioxide in flue gas. Background Art

[0002] In the context of global response to climate change, reducing greenhouse gas emissions has become a common goal and mission of the international community. 2 ) is one of the main greenhouse gases, and its emission control is particularly critical. Among the sources of carbon dioxide emissions, flue gas CO generated in industrial production processes 2 The proportion of CO2 emissions in the world's total emissions is relatively high, and the current mainstream processes of CO2 gas separation, compression, liquefaction, storage, and valence state reduction all consume a lot of energy and materials. Therefore, it is necessary to develop efficient and environmentally friendly flue gas CO 2 Capture technology is particularly urgent.

[0003] An innovative solution is to utilize mineral components such as metal oxides and silicates to transform them into more stable carbonates. The mineral sequestration of carbon dioxide can effectively reduce costs and energy consumption, and is a green carbon capture technology.

[0004] In the current industrial production process, especially in the steel, electricity, chemical, waste incineration and other industries, a large amount of inorganic mineral solid waste is generated, such as steel slag, waste incineration fly ash, fly ash and other bulk solid wastes. These solid wastes contain a high proportion of calcium components, and are often dominated by metal oxides and silicate compounds, making this type of solid waste usually alkaline or weakly alkaline. How to effectively treat and utilize these alkaline solid wastes and achieve CO 2 The reduction of emissions has become an urgent problem to be solved. In this context, the use of alkaline solid waste to treat flue gas CO 2 It has become a strategy for mismatched resource reuse and the optimal technical path for waste treatment. Alkaline solid waste contains abundant metal elements such as calcium, and mostly exists in the form of oxides and silicates. Under relevant auxiliary conditions, it can react with CO in flue gas. 2 Chemical reactions occur to generate solid wastes such as calcium carbonate, thereby capturing carbon dioxide. Therefore, the development of alkaline solid waste to fix flue gas CO 2 This method can not only effectively utilize alkali slag resources, but also reduce processing costs and environmental pollution, which has far-reaching significance for promoting the development of a low-carbon economy.

[0005] At present, alkaline solid waste captures flue gas CO 2 Common methods of fixation include direct fixation and indirect fixation. Direct fixation is the direct contact of alkaline solid waste with CO 2Carbonation reaction occurs, which is usually used in the production of building materials such as concrete. Currently, there is a method reported to capture carbon dioxide using carbide slag, which is to keep the carbide slag at a temperature of 100-120°C for 2-3 hours, then grind and sieve it, and pass CO 2 Gas, at a temperature of 580~750℃, CO 2 Calcination was carried out under gas atmosphere for 1.5-3h to obtain CaCO 3 Solid. This method of direct fixation requires sufficient time and high reaction temperature to effectively fix CO 2 At the same time, the contact mode between solid and gas in completely dry treatment is limited, the mass transfer and reaction process are slow, and there are problems of high energy consumption and limited reaction rate.

[0006] The indirect fixation method is to first use an acid solution to leach the calcium ions in the solid slag, and then adjust the pH to alkaline and introduce CO 2 The reaction generates calcium carbonate. In previous reports on solid waste carbon fixation, acid extractants such as sulfuric acid, hydrochloric acid, acetic acid and other soluble acids with stronger acidity than silicate are required to accelerate the extraction of calcium, magnesium and other components in solid waste that can precipitate with carbonate. At the same time, water consumption and alkalizing agents such as sodium hydroxide, ammonia and other soluble alkalis are also required to increase the alkalinity of the solution to increase the rate of carbon dioxide absorption. Acid extractants and alkalizing agents cannot be recycled, resulting in a large amount of waste liquid, which increases the cost of subsequent treatment. There are also reports on the use of calcium silicate-containing substances to fix CO 2 The invention discloses a system and method for preparing calcium carbonate, which specifically uses ammonium chloride solution as a circulating extractant, uses ammonium chloride solution to leach calcium ions in a calcium silicate raw material in a leaching device and generates ammonia gas, separates the ammonia gas generated by the reaction from the solution by gas stripping (desorption), thereby promoting the reaction, mixes the generated ammonia gas with the above-mentioned calcium ion-containing leaching solution to obtain a mineralized solution, and separates the ammonia gas generated by the reaction from the solution by gas stripping (desorption), thereby promoting the reaction, and ... mixing the generated ammonia gas with the above-mentioned calcium ion-containing leaching solution to obtain a mineralized solution, and 2 The gas is introduced into the mineralization solution, and under certain conditions, calcium carbonate precipitation is generated and ammonium chloride solution is recovered. After solid-liquid separation, the ammonium chloride solution is recycled as an extractant. This indirect fixation of CO 2 In the method, since the solid waste raw materials often have complex components, ammonium chloride will quickly turn into waste liquid with complex components, thereby generating a large amount of waste liquid.

[0007] In general, indirect fixation or wet fixation will lead to cost consumption in process stages such as acid resources, water resources, solid-liquid mixing and solid-liquid separation, and requires a large amount of water while producing a large amount of solid waste leaching waste liquid, which is difficult to handle and has high environmental risks, increasing the subsequent treatment costs. Summary of the invention

[0008] The present invention proposes a method for directly fixing carbon dioxide in flue gas by semi-dry method using alkaline solid waste, relying on the phase change of ammonium chloride to make it migrate and decompose, and on this basis, activating alkaline solid waste and capturing CO in flue gas. 2 The present invention can solve the problems of limited mass transfer and high energy consumption in the conventional direct dry method, and the problem of large amounts of waste liquid generated due to the consumption of acid extracting agent, water and alkalizing agent that cannot be recycled in the indirect method.

[0009] The present invention firstly introduces alkaline solid waste into a reaction tank, and then uses ammonium chloride solution as a circulating liquid. The circulating liquid is mixed with the alkaline solid waste. The ammonium chloride and water are decomposed and gasified after being heated to produce hydrogen chloride, ammonia and water vapor. The water vapor wets the surface of the alkaline solid waste on the upper layer. The wetted alkaline solid waste adheres to hydrogen chloride and can extract calcium ions in the alkaline solid waste to activate it. Then, CO is introduced into the reaction tank. 2 , intensified CO in an ammonia environment 2 The activated calcium ions will react with CO 2 Calcium carbonate is generated, while ammonia gas and chloride ions and ammonium in a humid environment regenerate ammonium chloride;

[0010] The method of the present invention using alkaline solid waste semi-dry method to directly circulate and fix carbon dioxide in flue gas is to achieve continuous circulation operation, including an ammonium chloride separation stage, a metal ion extraction stage, and a carbon dioxide absorption and fixation stage:

[0011] 1. In the ammonium chloride separation stage, the thermal decomposition products of ammonium chloride are hydrogen chloride and ammonia, and water vapor is generated when heated.

[0012] 2. In the metal ion extraction stage, hydrogen chloride and water vapor can effectively dissolve metal ions such as calcium in alkaline solid waste after contacting alkaline solid waste; ammonia and water vapor synergistically present alkalinity, which can accelerate the fixation of carbon dioxide and promote the conversion of carbon dioxide from the gas phase to the gas-liquid interface ((2NH 3 ·H 2 O+CO 2 ⇌(NH 4 ) 2 CO 3 +H 2 O, NH 3 ·H 2 O+CO 2 ⇌NH 4 HCO 3 ).

[0013] 3. In the stage of carbon dioxide absorption and fixation, ammonia on the alkaline solid waste dissolves in water to form an alkaline solution, which reacts with the carbon dioxide in the introduced gas to form ammonium carbonate and ammonium bicarbonate, and the carbon dioxide is fixed in the water in the form of salt, thereby promoting the conversion of carbon dioxide from the gas phase to the liquid phase; the process of ammonia dissolving in water to form an alkaline solution can catalyze the rapid formation of metal ions and carbonate precipitation components in the alkaline solid waste; water can play a role in wetting the surface of the solid waste and providing a reaction environment.

[0014] The method of directly circulating and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method is carried out according to the following steps:

[0015] Step 1:

[0016] ①, opening the second feed port (2), feeding the crushed alkaline solid waste into the second reaction tank (23), and then closing the second feed port (2); after the alkaline solid waste is crushed, the contact area becomes larger and the activity is improved;

[0017] ②, the first reaction tank (22) contains alkaline solid waste that has been fixed by carbon dioxide absorption. The temperature of the first reaction tank (22) is heated to 105-450°C. The circulating fluid in the first reaction tank (22) is decomposed to produce hydrogen chloride, ammonia and water vapor, and ammonium chloride is separated in the first reaction tank (22). Then, the 1# gas valve (4) is opened to transport the produced gas to the second reaction tank (23);

[0018] ③. The second reaction tank (23) contains the crushed alkaline solid waste and the circulating liquid. The gas delivered from the first reaction tank (22) causes the temperature and pressure in the second reaction tank (23) to rise continuously. When the temperature in the second reaction tank (23) reaches 105-450° C., metal ion extraction is achieved in the second reaction tank (23). Then, the 2# gas valve (5) is opened to pass the gas generated in the second reaction tank (23) into the third reaction tank (24). If the temperature in the second reaction tank (23) rises slowly or the temperature is insufficient to reach 105-450° C., the second reaction tank (23) is heated.

[0019] ④. The third reaction tank (24) contains alkaline solid waste from which metal ions have been extracted. The 6# gas valve (9) is opened to introduce pre-captured carbon dioxide, and the 3# gas valve (6) and the 9# gas valve (12) are closed. The temperature of the third reaction tank (24) is controlled to be below 100° C. When the temperature is above 100° C., the third reaction tank (24) is cooled to achieve carbon dioxide absorption and fixation in the third reaction tank (24).

[0020] ⑤. When the first reaction tank (22) no longer produces gas, open the 1# discharge valve (13) to discharge the alkaline solid waste in the first reaction tank (22);

[0021] Step 2:

[0022] ①, opening the first feed port (1), feeding the crushed alkaline solid waste into the first reaction tank (22), and then closing the first feed port (1);

[0023] ②, the third reaction tank (24) contains alkaline solid waste that has been fixed by carbon dioxide absorption. The temperature of the third reaction tank (24) is controlled to be 105-400° C. The hydrogen chloride, ammonia and water vapor generated by the decomposition of the circulating fluid in the third reaction tank (24) are separated into ammonium chloride in the third reaction tank (24), and the 3# gas valve (6) is opened to transport the gas generated in the third reaction tank (24) to the first reaction tank (22);

[0024] ③. The first reaction tank (22) contains the crushed alkaline solid waste and the circulating liquid. When the temperature of the first reaction tank (22) reaches 105-450° C., metal ion extraction is achieved in the first reaction tank (22). The outlet 1# gas valve (4) is opened to pass the gas generated in the first reaction tank (22) into the second reaction tank (23).

[0025] ④. The second reaction tank (23) contains alkaline solid waste from which metal ions have been extracted. After the gas generated in the first reaction tank (22) begins to flow into the second reaction tank (23), the 5# gas valve (8) is opened to allow the pre-captured carbon dioxide to flow in. The 2# gas valve (5) and the 8# gas valve (11) are closed to achieve carbon dioxide absorption and fixation in the second reaction tank (23). During the process, the temperature of the second reaction tank (23) is controlled to be below 100° C., and the second reaction tank (23) is cooled when it is above 100° C.;

[0026] ⑤. After the third reaction tank (24) stops producing gas, open the 3# discharge valve (15) to discharge the alkaline solid waste from the third reaction tank (24);

[0027] Step 3:

[0028] ①, opening the third feed port (3), feeding the crushed alkaline solid waste into the third reaction tank (24), and then closing the third feed port (3);

[0029] ②, the alkaline solid waste that has been fixed by carbon dioxide absorption is contained in the second reaction tank (23), the temperature of the second reaction tank (23) is controlled to be 105-400°C, the hydrogen chloride, ammonia and water vapor generated by the decomposition of the circulating fluid in the second reaction tank (23) are separated into ammonium chloride in the second reaction tank (23), the 2# gas valve (5) is opened, and the gas generated in the second reaction tank (23) is passed into the third reaction tank (24);

[0030] ③. The third reaction tank (24) contains the crushed alkaline solid waste and the circulating liquid. When the temperature of the third reaction tank (24) reaches 105-450° C., metal ion extraction is achieved in the third reaction tank (24). The 3# gas valve (6) is opened to pass the gas generated in the third reaction tank (24) into the first reaction tank (22).

[0031] ④. The first reaction tank (22) contains alkaline solid waste for metal ion extraction. After the gas generated by the third reaction tank (24) begins to flow into the first reaction tank (22), the 4# gas valve (7) is opened to introduce the pre-captured carbon dioxide gas, and the 1# gas valve (4) and the 7# gas valve (10) are closed to achieve carbon dioxide absorption and fixation in the first reaction tank (22). During the process, the temperature of the first reaction tank (22) is controlled to be below 100° C., and the first reaction tank (22) is cooled when it is above 100° C.;

[0032] ⑤. After the second reaction tank (23) no longer produces gas, open the 2# discharge valve (14) to discharge the material in the second reaction tank (23);

[0033] Step 4: Repeat steps 1 to 3 to realize direct circulation and fixation of carbon dioxide in flue gas by using alkaline solid waste semi-dry method;

[0034] The method of directly cyclically fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method is carried out in an alkaline solid waste cyclic carbon dioxide fixing device.

[0035] Principle and beneficial effects of the invention:

[0036] (1) Compared with the dry direct fixation technology under high temperature and high pressure, the present invention can decompose ammonium chloride to extract calcium through water vapor wetting and lower temperature, thereby achieving mass transfer enhancement and efficiency improvement at lower energy consumption.

[0037] (2) Compared with the indirect wet fixation technology using ammonium chloride solution as the extracting liquid, the present invention can efficiently capture and recycle carbon dioxide. It uses the principle that ammonium chloride can undergo phase change, volatilization and decomposition at a relatively low temperature to effectively activate alkaline solid waste in a dry or semi-dry state, thereby improving carbon capture efficiency. Even if a small amount of water needs to be added to the circulating liquid during the process, the added water will migrate in the form of water vapor along with ammonium chloride and its decomposition products in the tank in a gaseous state, thereby wetting the alkaline solid waste and providing a reaction environment; while ammonium chloride completes the activation of the alkaline solid waste and its own circulation in its phase change, decomposition and subsequent reactions of the decomposition gas. Conventional wet treatment is to directly immerse the solid residue in a large amount of ammonium chloride solution to extract the metal ions therein. In the process, not only the metal ions will be leached out, but also a large amount of organic matter and other anions will be leached into the ammonium chloride solution, causing the ammonium chloride solution to be contaminated and lose its effectiveness and become a waste liquid. In the process of the present invention, only a small amount of ammonium chloride solution is used. The ammonium chloride solution is gasified and decomposed into hydrogen chloride, ammonia and water vapor, which are infiltrated into the surface of the solid slag for dry or semi-dry reaction. After the reaction, the gaseous hydrogen chloride, ammonia and water vapor will turn back into ammonium chloride, thereby avoiding the leaching of impurities to cause ammonium chloride pollution, and no waste liquid that needs to be treated later is generated, thereby achieving recycling in a true sense.

[0038] (3) The present invention saves separation processes such as precipitation and filtration, and the product does not need to be dried and can be directly used as a concrete auxiliary material, which is easy to realize industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the structure of the alkaline solid waste recycling and carbon dioxide fixation device in Example 1. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any reasonable combination of the specific implementation modes.

[0041] Specific implementation method 1: In this implementation method, the method of directly circulating and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method is carried out according to the following steps:

[0042] Step 1:

[0043] ①, opening the second feed port (2), feeding the crushed alkaline solid waste into the second reaction tank (23), and then closing the second feed port (2); after the alkaline solid waste is crushed, the contact area becomes larger and the activity is improved;

[0044] ②, the first reaction tank (22) contains alkaline solid waste that has been fixed by carbon dioxide absorption. The temperature of the first reaction tank (22) is heated to 105-450°C. The circulating fluid in the first reaction tank (22) is decomposed to produce hydrogen chloride, ammonia and water vapor, and ammonium chloride is separated in the first reaction tank (22). Then, the 1# gas valve (4) is opened to transport the produced gas to the second reaction tank (23);

[0045] ③. The second reaction tank (23) contains the crushed alkaline solid waste and the circulating liquid. The gas delivered from the first reaction tank (22) causes the temperature and pressure in the second reaction tank (23) to rise continuously. When the temperature in the second reaction tank (23) reaches 105-450° C., metal ion extraction is achieved in the second reaction tank (23). Then, the 2# gas valve (5) is opened to pass the gas generated in the second reaction tank (23) into the third reaction tank (24). If the temperature in the second reaction tank (23) rises slowly or the temperature is insufficient to reach 105-450° C., the second reaction tank (23) is heated.

[0046] ④. The third reaction tank (24) contains alkaline solid waste from which metal ions have been extracted. The 6# gas valve (9) is opened to introduce pre-captured carbon dioxide, and the 3# gas valve (6) and the 9# gas valve (12) are closed. The temperature of the third reaction tank (24) is controlled to be below 100° C. When the temperature is above 100° C., the third reaction tank (24) is cooled to achieve carbon dioxide absorption and fixation in the third reaction tank (24).

[0047] ⑤. When the first reaction tank (22) no longer produces gas, open the 1# discharge valve (13) to discharge the alkaline solid waste in the first reaction tank (22);

[0048] Step 2:

[0049] ①, opening the first feed port (1), feeding the crushed alkaline solid waste into the first reaction tank (22), and then closing the first feed port (1);

[0050] ②, the third reaction tank (24) contains alkaline solid waste that has been fixed by carbon dioxide absorption. The temperature of the third reaction tank (24) is controlled to be 105-400° C. The hydrogen chloride, ammonia and water vapor generated by the decomposition of the circulating fluid in the third reaction tank (24) are separated into ammonium chloride in the third reaction tank (24), and the 3# gas valve (6) is opened to transport the gas generated in the third reaction tank (24) to the first reaction tank (22);

[0051] ③. The first reaction tank (22) contains the crushed alkaline solid waste and the circulating liquid. When the temperature of the first reaction tank (22) reaches 105-450° C., metal ion extraction is achieved in the first reaction tank (22). The outlet 1# gas valve (4) is opened to pass the gas generated in the first reaction tank (22) into the second reaction tank (23).

[0052] ④. The second reaction tank (23) contains alkaline solid waste from which metal ions have been extracted. After the gas generated in the first reaction tank (22) begins to flow into the second reaction tank (23), the 5# gas valve (8) is opened to allow the pre-captured carbon dioxide to flow in. The 2# gas valve (5) and the 8# gas valve (11) are closed to achieve carbon dioxide absorption and fixation in the second reaction tank (23). During the process, the temperature of the second reaction tank (23) is controlled to be below 100° C., and the second reaction tank (23) is cooled when it is above 100° C.;

[0053] ⑤. After the third reaction tank (24) stops producing gas, open the 3# discharge valve (15) to discharge the alkaline solid waste from the third reaction tank (24);

[0054] Step 3:

[0055] ①, opening the third feed port (3), feeding the crushed alkaline solid waste into the third reaction tank (24), and then closing the third feed port (3);

[0056] ②, the alkaline solid waste that has been fixed by carbon dioxide absorption is contained in the second reaction tank (23), the temperature of the second reaction tank (23) is controlled to be 105-400°C, the hydrogen chloride, ammonia and water vapor generated by the decomposition of the circulating fluid in the second reaction tank (23) are separated into ammonium chloride in the second reaction tank (23), the 2# gas valve (5) is opened, and the gas generated in the second reaction tank (23) is passed into the third reaction tank (24);

[0057] ③. The third reaction tank (24) contains the crushed alkaline solid waste and the circulating liquid. When the temperature of the third reaction tank (24) reaches 105-450° C., metal ion extraction is achieved in the third reaction tank (24). The 3# gas valve (6) is opened to pass the gas generated in the third reaction tank (24) into the first reaction tank (22).

[0058] ④. The first reaction tank (22) contains alkaline solid waste for metal ion extraction. After the gas generated by the third reaction tank (24) begins to flow into the first reaction tank (22), the 4# gas valve (7) is opened to introduce the pre-captured carbon dioxide gas, and the 1# gas valve (4) and the 7# gas valve (10) are closed to achieve carbon dioxide absorption and fixation in the first reaction tank (22). During the process, the temperature of the first reaction tank (22) is controlled to be below 100° C., and the first reaction tank (22) is cooled when it is above 100° C.;

[0059] ⑤. After the second reaction tank (23) no longer produces gas, open the 2# discharge valve (14) to discharge the material in the second reaction tank (23);

[0060] Step 4: Repeat steps 1 to 3 to realize direct circulation and fixation of carbon dioxide in flue gas by using alkaline solid waste semi-dry method;

[0061] The method of directly cyclically fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method is carried out in an alkaline solid waste cyclic carbon dioxide fixing device.

[0062] This embodiment has the following beneficial effects:

[0063] (1) Compared with the dry direct fixation technology under high temperature and high pressure, this embodiment can decompose ammonium chloride to extract calcium through water vapor wetting and lower temperature, thereby achieving mass transfer enhancement and efficiency improvement at lower energy consumption.

[0064] (2) Compared with the indirect wet fixation technology using ammonium chloride solution as the extracting liquid, this embodiment can efficiently capture and recycle carbon dioxide. It uses the principle that ammonium chloride can undergo phase change, volatilization and decomposition at a relatively low temperature to effectively activate alkaline solid waste in a dry or semi-dry state, thereby improving carbon capture efficiency. Even if a small amount of water needs to be added to the circulating liquid during the process, the added water will migrate in the form of water vapor along with ammonium chloride and its decomposition products in the tank in a gaseous state, playing the role of wetting the alkaline solid waste and providing a reaction environment; while ammonium chloride completes the activation of alkaline solid waste and its own circulation in its phase change, decomposition and subsequent reactions of decomposition gas. Conventional wet treatment is to directly immerse the solid residue in a large amount of ammonium chloride solution to extract the metal ions therein. In the process, not only the metal ions will be leached out, but also a large amount of organic matter and other anions will be leached into the ammonium chloride solution, causing the ammonium chloride solution to be contaminated and lose its effectiveness and become waste liquid. In the process of this embodiment, only a small amount of ammonium chloride solution is used. The ammonium chloride solution is gasified and decomposed into hydrogen chloride, ammonia and water vapor, which are infiltrated into the surface of the solid slag for dry or semi-dry reaction. After the reaction, the gaseous hydrogen chloride, ammonia and water vapor will turn back into ammonium chloride, thereby avoiding the leaching of impurities to cause ammonium chloride pollution, and no waste liquid that needs to be treated later is generated, thus achieving recycling in a true sense.

[0065] (3) This embodiment saves separation processes such as sedimentation and filtration, and the product does not need to be dried and can be directly used as a concrete auxiliary material, which is easy to achieve industrial application.

[0066] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that the circulating liquid in steps 1 to 3 is an ammonium chloride solution, and the molar ratio of ammonium chloride in the ammonium chloride solution to the carbon-fixable metal ions in the alkaline solid waste is 0.5~3:1.

[0067] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that: the water content in the ammonium chloride solution in step four is 5-15% of the mass of the alkaline solid waste.

[0068] Specific implementation method 4: This implementation method is different from any one of specific implementation methods 1 to 3 in that the alkaline solid waste described in steps 1 to 4 is a bulk solid waste rich in metal oxides and silicates.

[0069] Specific implementation mode 5: This implementation mode is different from specific implementation mode 4 in that the bulk solid waste rich in metal oxides and silicates is steel slag, fly ash or waste incineration fly ash.

[0070] Specific implementation method six: This implementation method is different from any one of specific implementation methods one to five in that the carbon dioxide gas pre-captured in steps one to three is carbon dioxide captured from flue gas generated in production processes such as cement plants, power plants, and metallurgical plants.

[0071] Specific embodiment 7: This embodiment differs from any one of specific embodiments 1 to 6 in that the cooling medium used in cooling the first reaction tank (22), the second reaction tank (23) and the third reaction tank (24) in steps 1 to 3 is water or air.

[0072] Specific embodiment eight: This embodiment differs from any one of specific embodiments one to seven in that: the alkaline solid waste recycling carbon dioxide fixation device is composed of a first reaction tank (22), a second reaction tank (23), a third reaction tank (24) and a storage tank (21);

[0073] The first reaction tank (22) is provided with a first feed port (1) and an exhaust port at the top, and a reaction gas inlet and a carbon dioxide inlet are provided at the bottom of the first reaction tank (22); the second reaction tank (23) is provided with a second feed port (2) and an exhaust port at the top, and a reaction gas inlet and a carbon dioxide inlet are provided at the bottom of the second reaction tank (23); the third reaction tank (24) is provided with a third feed port (3) at the top, and a reaction gas inlet and a carbon dioxide inlet are provided at the bottom of the third feed port (3);

[0074] The material outlet of the material storage tank (21) is connected to a material conveying pipe (16), and the material conveying pipe (16) is respectively connected to the first feed port (1), the second feed port (2) and the third feed port (3);

[0075] The exhaust port arranged at the top of the first reaction tank (22) is connected to the reaction gas inlet arranged at the bottom of the second reaction tank (23) via a first reaction tank exhaust pipe (20); a 1# gas valve (4) is arranged on the first reaction tank exhaust pipe (20); a first reaction tank exhaust branch pipe is arranged between the 1# gas valve (4) on the first reaction tank exhaust pipe (20) and the exhaust port arranged at the top of the first reaction tank (22); a 7# gas valve (10) is arranged on the first reaction tank exhaust branch pipe; the exhaust port arranged at the top of the second reaction tank (23) is connected to the reaction gas inlet arranged at the bottom of the third reaction tank (24) via a second reaction tank exhaust pipe (19); a 2# gas valve (5 ), a second reaction tank exhaust branch pipe is arranged between the 2# gas valve (5) on the second reaction tank exhaust pipe (19) and the exhaust port arranged at the top of the second reaction tank (23), and an 8# gas valve (11) is arranged on the second reaction tank exhaust branch pipe; the exhaust port arranged at the top of the third reaction tank (24) is connected to the reaction gas inlet arranged at the bottom of the first reaction tank (22) through the third reaction tank exhaust pipe (17), and a 3# gas valve (6) is arranged on the third reaction tank exhaust pipe (17); a third reaction tank exhaust branch pipe is arranged between the 3# gas valve (6) on the third reaction tank exhaust pipe (17) and the exhaust port arranged at the top of the third reaction tank (24), and a 9# gas valve (12) is arranged on the third reaction tank exhaust branch pipe;

[0076] The carbon dioxide inlet port provided at the bottom of the first reaction tank (22) is connected to a carbon dioxide inlet pipe, and a 4# gas valve (7) is provided on the carbon dioxide inlet pipe at the bottom of the first reaction tank (22); the carbon dioxide inlet port provided at the bottom of the second reaction tank (23) is connected to a carbon dioxide inlet pipe, and a 5# gas valve (8) is provided on the carbon dioxide inlet pipe at the bottom of the second reaction tank (23); the carbon dioxide inlet port provided at the bottom of the third reaction tank (24) is connected to a carbon dioxide inlet pipe, and a 6# gas valve (9) is provided on the carbon dioxide inlet pipe at the bottom of the third reaction tank (24); the carbon dioxide inlet pipe at the bottom of the first reaction tank (22), the carbon dioxide inlet pipe at the bottom of the second reaction tank (23), and the carbon dioxide inlet pipe at the bottom of the third reaction tank (24) are respectively connected to a carbon dioxide inlet main pipe (18).

[0077] Specific embodiment 9: This embodiment differs from specific embodiment 8 in that: a discharge pipe is provided at the bottom of the first reaction tank (22), a discharge pipe is provided at the bottom of the second reaction tank (23), and a discharge pipe is provided at the bottom of the second reaction tank (23).

[0078] Specific embodiment ten: This embodiment differs from specific embodiment nine in that: a 1# discharge valve (13) is provided on the discharge pipe arranged at the bottom of the first reaction tank (22), a 2# discharge valve (14) is provided on the discharge pipe arranged at the bottom of the second reaction tank (23), and a 3# discharge valve (15) is provided on the discharge pipe arranged at the bottom of the third reaction tank (24).

[0079] Example 1

[0080] The method of directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method in this embodiment is carried out according to the following steps:

[0081] Step 1:

[0082] ①, opening the second feed port (2), feeding the crushed 100-mesh alkaline solid waste and the circulating liquid into the second reaction tank (23), and then closing the second feed port (2); after the alkaline solid waste is crushed, the contact area becomes larger and the activity is improved;

[0083] ②, the first reaction tank (22) contains alkaline solid waste that has been fixed by carbon dioxide absorption. The temperature of the first reaction tank (22) is heated to 400° C. The circulating fluid in the first reaction tank (22) is decomposed to produce hydrogen chloride, ammonia and water vapor, and ammonium chloride is separated in the first reaction tank (22). Then, the No. 1 gas valve (4) is opened to transport the produced gas to the second reaction tank (23);

[0084] ③. The second reaction tank (23) contains 100-mesh alkaline solid waste and circulating liquid after crushing. The gas delivered from the first reaction tank (22) causes the temperature and pressure in the second reaction tank (23) to rise continuously. When the temperature in the second reaction tank (23) reaches 250-300° C., metal ion extraction is achieved in the second reaction tank (23); then, the 2# gas valve (5) is opened to pass the gas generated in the second reaction tank (23) into the third reaction tank (24); if the temperature in the second reaction tank (23) rises slowly or the temperature is insufficient to reach 250-300° C., the second reaction tank (23) is heated;

[0085] ④. The third reaction tank (24) contains alkaline solid waste from which metal ions have been extracted. The 6# gas valve (9) is opened to introduce pre-captured carbon dioxide, and the 3# gas valve (6) and the 9# gas valve (12) are closed. The temperature of the third reaction tank (24) is controlled to be below 100° C. When the temperature is above 100° C., the third reaction tank (24) is cooled to achieve carbon dioxide absorption and fixation in the third reaction tank (24).

[0086] ⑤. When the first reaction tank (22) no longer produces gas, open the 1# discharge valve (13) to discharge the alkaline solid waste in the first reaction tank (22);

[0087] Step 2:

[0088] ①, opening the first feed port (1), feeding the crushed alkaline solid waste into the first reaction tank (22), and then closing the first feed port (1);

[0089] ②, the third reaction tank (24) contains alkaline solid waste that has been fixed by carbon dioxide absorption. The temperature of the third reaction tank (24) is controlled to 400° C. The hydrogen chloride, ammonia and water vapor generated by the decomposition of the circulating fluid in the third reaction tank (24) are separated into ammonium chloride in the third reaction tank (24), and the 3# gas valve (6) is opened to transport the gas generated in the third reaction tank (24) to the first reaction tank (22);

[0090] ③. The first reaction tank (22) contains 100-mesh alkaline solid waste and circulating liquid after crushing. When the temperature of the first reaction tank (22) reaches 250-300° C., metal ion extraction is achieved in the first reaction tank (22); the outlet 1# gas valve (4) is opened to pass the gas generated in the first reaction tank (22) into the second reaction tank (23);

[0091] ④. The second reaction tank (23) contains alkaline solid waste from which metal ions have been extracted. After the gas generated in the first reaction tank (22) begins to flow into the second reaction tank (23), the 5# gas valve (8) is opened to allow the pre-captured carbon dioxide to flow in. The 2# gas valve (5) and the 8# gas valve (11) are closed to achieve carbon dioxide absorption and fixation in the second reaction tank (23). During the process, the temperature of the second reaction tank (23) is controlled to be below 100° C., and the second reaction tank (23) is cooled when it is above 100° C.;

[0092] ⑤. After the third reaction tank (24) stops producing gas, open the 3# discharge valve (15) to discharge the alkaline solid waste from the third reaction tank (24);

[0093] Step 3:

[0094] ①, opening the third feed port (3), feeding the crushed alkaline solid waste into the third reaction tank (24), and then closing the third feed port (3);

[0095] ②, the alkaline solid waste that has been fixed by carbon dioxide absorption is contained in the second reaction tank (23), the temperature of the second reaction tank (23) is controlled to 400° C., the hydrogen chloride, ammonia and water vapor generated by the decomposition of the circulating fluid in the second reaction tank (23) are separated into ammonium chloride in the second reaction tank (23), the 2# gas valve (5) is opened, and the gas generated in the second reaction tank (23) is passed into the third reaction tank (24);

[0096] ③. The third reaction tank (24) contains 100-mesh alkaline solid waste and circulating liquid after crushing. When the temperature of the third reaction tank (24) reaches 250-300° C., metal ion extraction is achieved in the third reaction tank (24). The 3# gas valve (6) is opened to pass the gas generated in the third reaction tank (24) into the first reaction tank (22).

[0097] ④. The first reaction tank (22) contains alkaline solid waste for metal ion extraction. After the gas generated by the third reaction tank (24) begins to flow into the first reaction tank (22), the 4# gas valve (7) is opened to introduce the pre-captured carbon dioxide gas, and the 1# gas valve (4) and the 7# gas valve (10) are closed to achieve carbon dioxide absorption and fixation in the first reaction tank (22). During the process, the temperature of the first reaction tank (22) is controlled to be below 100° C., and the first reaction tank (22) is cooled when it is above 100° C.;

[0098] ⑤. After the second reaction tank (23) no longer produces gas, open the 2# discharge valve (14) to discharge the material in the second reaction tank (23);

[0099] Step 4: Repeat steps 1 to 3 to realize direct circulation and fixation of carbon dioxide in flue gas by using alkaline solid waste semi-dry method;

[0100] The circulating fluid in steps 1 to 3 is an ammonium chloride solution, and the molar ratio of ammonium chloride in the ammonium chloride solution to the carbon-fixable metal ions in the alkaline solid waste is 0.5 to 3: 1. The water content in the ammonium chloride solution is 5 to 15% of the mass of the alkaline solid waste.

[0101] The alkaline solid waste described in steps 1 to 3 is steel slag, and its carbon-fixing components are mainly calcium-based oxides and their silicates.

[0102] The carbon dioxide gas pre-captured in steps 1 to 3 is carbon dioxide captured from flue gas generated in production processes such as cement plants, power plants, and metallurgical plants.

[0103] When cooling the first reaction tank (22), the second reaction tank (23) and the third reaction tank (24) in steps 1 to 3, the cooling medium is water.

[0104] The above-mentioned method of directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method is carried out in an alkaline solid waste recycling carbon dioxide fixation device.

[0105] The alkaline solid waste circulating carbon dioxide fixation device is composed of a first reaction tank (22), a second reaction tank (23), a third reaction tank (24) and a storage tank (21);

[0106] The first reaction tank (22) is provided with a first feed port (1) and an exhaust port at the top, and a reaction gas inlet and a carbon dioxide inlet are provided at the bottom of the first reaction tank (22); the second reaction tank (23) is provided with a second feed port (2) and an exhaust port at the top, and a reaction gas inlet and a carbon dioxide inlet are provided at the bottom of the second reaction tank (23); the third reaction tank (24) is provided with a third feed port (3) at the top, and a reaction gas inlet and a carbon dioxide inlet are provided at the bottom of the third feed port (3);

[0107] The material outlet of the material storage tank (21) is connected to a material conveying pipe (16), and the material conveying pipe (16) is respectively connected to the first feed port (1), the second feed port (2) and the third feed port (3);

[0108] The exhaust port arranged at the top of the first reaction tank (22) is connected to the reaction gas inlet arranged at the bottom of the second reaction tank (23) via a first reaction tank exhaust pipe (20); a 1# gas valve (4) is arranged on the first reaction tank exhaust pipe (20); a first reaction tank exhaust branch pipe is arranged between the 1# gas valve (4) on the first reaction tank exhaust pipe (20) and the exhaust port arranged at the top of the first reaction tank (22); a 7# gas valve (10) is arranged on the first reaction tank exhaust branch pipe; the exhaust port arranged at the top of the second reaction tank (23) is connected to the reaction gas inlet arranged at the bottom of the third reaction tank (24) via a second reaction tank exhaust pipe (19); a 2# gas valve (5 ), a second reaction tank exhaust branch pipe is arranged between the 2# gas valve (5) on the second reaction tank exhaust pipe (19) and the exhaust port arranged at the top of the second reaction tank (23), and an 8# gas valve (11) is arranged on the second reaction tank exhaust branch pipe; the exhaust port arranged at the top of the third reaction tank (24) is connected to the reaction gas inlet arranged at the bottom of the first reaction tank (22) through the third reaction tank exhaust pipe (17), and a 3# gas valve (6) is arranged on the third reaction tank exhaust pipe (17); a third reaction tank exhaust branch pipe is arranged between the 3# gas valve (6) on the third reaction tank exhaust pipe (17) and the exhaust port arranged at the top of the third reaction tank (24), and a 9# gas valve (12) is arranged on the third reaction tank exhaust branch pipe;

[0109] The carbon dioxide inlet port provided at the bottom of the first reaction tank (22) is connected to a carbon dioxide inlet pipe, and a 4# gas valve (7) is provided on the carbon dioxide inlet pipe at the bottom of the first reaction tank (22); the carbon dioxide inlet port provided at the bottom of the second reaction tank (23) is connected to a carbon dioxide inlet pipe, and a 5# gas valve (8) is provided on the carbon dioxide inlet pipe at the bottom of the second reaction tank (23); the carbon dioxide inlet port provided at the bottom of the third reaction tank (24) is connected to a carbon dioxide inlet pipe, and a 6# gas valve (9) is provided on the carbon dioxide inlet pipe at the bottom of the third reaction tank (24); the carbon dioxide inlet pipe at the bottom of the first reaction tank (22), the carbon dioxide inlet pipe at the bottom of the second reaction tank (23), and the carbon dioxide inlet pipe at the bottom of the third reaction tank (24) are respectively connected to a carbon dioxide inlet main pipe (18).

[0110] The first reaction tank (22) is provided with a discharge pipe at the bottom, the second reaction tank (23) is provided with a discharge pipe at the bottom, and the second reaction tank (23) is provided with a discharge pipe at the bottom. The discharge pipe provided at the bottom of the first reaction tank (22) is provided with a 1# discharge valve (13), the discharge pipe provided at the bottom of the second reaction tank (23) is provided with a 2# discharge valve (14), and the discharge pipe provided at the bottom of the third reaction tank (24) is provided with a 3# discharge valve (15).

[0111] This embodiment completes one cycle through steps one to three. During the cycle, the first reaction tank (22), the second reaction tank (23), and the third reaction tank (24) alternately complete different functions to achieve carbon fixation of alkaline solid waste. In the three steps, the calcium conversion rate in the steel slag is greater than 60%, and it is converted from calcium oxide or calcium silicate to aragonite calcium carbonate. In the three steps, the first reaction tank (22), the second reaction tank (23), and the third reaction tank (24) are used as carbon dioxide tanks in turn during the recycling, and the absorption rate is more than 90%. The calcium oxide component produced by carbon fixation of steel slag can release the captured carbon dioxide gas after high-temperature heating, making it a potential source of high-purity carbon dioxide gas. At this time, the alkaline solid waste steel slag used can be used for cyclic carbon fixation.

Claims

1. A method for directly circulating and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method, characterized in that: The method of directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method is carried out according to the following steps: Step 1: ①, opening the second feed port (2), feeding the crushed alkaline solid waste into the second reaction tank (23), and then closing the second feed port (2); after the alkaline solid waste is crushed, the contact area becomes larger and the activity is improved; ②, the first reaction tank (22) contains alkaline solid waste that has been fixed by carbon dioxide absorption. The temperature of the first reaction tank (22) is heated to 105-450°C. The circulating fluid in the first reaction tank (22) is decomposed to produce hydrogen chloride, ammonia and water vapor, and ammonium chloride is separated in the first reaction tank (22). Then, the 1# gas valve (4) is opened to transport the produced gas to the second reaction tank (23); ③. The second reaction tank (23) contains the crushed alkaline solid waste and the circulating liquid. The gas delivered from the first reaction tank (22) causes the temperature and pressure in the second reaction tank (23) to rise continuously. When the temperature in the second reaction tank (23) reaches 105-450° C., metal ion extraction is achieved in the second reaction tank (23). Then, the 2# gas valve (5) is opened to pass the gas generated in the second reaction tank (23) into the third reaction tank (24). If the temperature in the second reaction tank (23) rises slowly or the temperature is insufficient to reach 105-450° C., the second reaction tank (23) is heated. ④. The third reaction tank (24) contains alkaline solid waste from which metal ions have been extracted. The 6# gas valve (9) is opened to introduce pre-captured carbon dioxide, and the 3# gas valve (6) and the 9# gas valve (12) are closed. The temperature of the third reaction tank (24) is controlled to be below 100° C. When the temperature is above 100° C., the third reaction tank (24) is cooled to achieve carbon dioxide absorption and fixation in the third reaction tank (24). ⑤. When the first reaction tank (22) no longer produces gas, open the 1# discharge valve (13) to discharge the alkaline solid waste in the first reaction tank (22); Step 2: ①, opening the first feed port (1), feeding the crushed alkaline solid waste into the first reaction tank (22), and then closing the first feed port (1); ②, the third reaction tank (24) contains alkaline solid waste that has been fixed by carbon dioxide absorption. The temperature of the third reaction tank (24) is controlled to be 105-400° C. The hydrogen chloride, ammonia and water vapor generated by the decomposition of the circulating fluid in the third reaction tank (24) are separated into ammonium chloride in the third reaction tank (24), and the 3# gas valve (6) is opened to transport the gas generated in the third reaction tank (24) to the first reaction tank (22); ③. The first reaction tank (22) contains the crushed alkaline solid waste and the circulating liquid. When the temperature of the first reaction tank (22) reaches 105-450° C., metal ion extraction is achieved in the first reaction tank (22). The outlet 1# gas valve (4) is opened to pass the gas generated in the first reaction tank (22) into the second reaction tank (23). ④. The second reaction tank (23) contains alkaline solid waste from which metal ions have been extracted. After the gas generated in the first reaction tank (22) begins to flow into the second reaction tank (23), the 5# gas valve (8) is opened to allow the pre-captured carbon dioxide to flow in. The 2# gas valve (5) and the 8# gas valve (11) are closed to achieve carbon dioxide absorption and fixation in the second reaction tank (23). During the process, the temperature of the second reaction tank (23) is controlled to be below 100° C., and the second reaction tank (23) is cooled when it is above 100° C.; ⑤. After the third reaction tank (24) stops producing gas, open the 3# discharge valve (15) to discharge the alkaline solid waste from the third reaction tank (24); Step 3: ①, opening the third feed port (3), feeding the crushed alkaline solid waste into the third reaction tank (24), and then closing the third feed port (3); ②, the alkaline solid waste that has been fixed by carbon dioxide absorption is contained in the second reaction tank (23), the temperature of the second reaction tank (23) is controlled to be 105-400°C, the hydrogen chloride, ammonia and water vapor generated by the decomposition of the circulating fluid in the second reaction tank (23) are separated into ammonium chloride in the second reaction tank (23), the 2# gas valve (5) is opened, and the gas generated in the second reaction tank (23) is passed into the third reaction tank (24); ③. The third reaction tank (24) contains the crushed alkaline solid waste and the circulating liquid. When the temperature of the third reaction tank (24) reaches 105-450° C., metal ion extraction is achieved in the third reaction tank (24); Open the 3# gas valve (6) to allow the gas produced by the third reaction tank (24) to flow into the first reaction tank (22); ④. The first reaction tank (22) contains alkaline solid waste for metal ion extraction. After the gas generated by the third reaction tank (24) begins to flow into the first reaction tank (22), the 4# gas valve (7) is opened to introduce the pre-captured carbon dioxide gas, and the 1# gas valve (4) and the 7# gas valve (10) are closed to achieve carbon dioxide absorption and fixation in the first reaction tank (22). During the process, the temperature of the first reaction tank (22) is controlled to be below 100° C., and the first reaction tank (22) is cooled when it is above 100° C.; ⑤. After the second reaction tank (23) no longer produces gas, open the 2# discharge valve (14) to discharge the material in the second reaction tank (23); Step 4: Repeat steps 1 to 3 to realize direct circulation and fixation of carbon dioxide in flue gas by using alkaline solid waste semi-dry method; The method of directly cyclically fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method is carried out in an alkaline solid waste cyclic carbon dioxide fixing device.

2. The method for directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method according to claim 1 is characterized in that: The circulating liquid in steps one to three is an ammonium chloride solution, and the molar ratio of ammonium chloride in the ammonium chloride solution to the carbon-fixable metal ions in the alkaline solid waste is 0.5-3:

1.

3. The method for directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method according to claim 2, characterized in that: The water content in the ammonium chloride solution in steps 1 to 3 is 5-15% of the mass of the alkaline solid waste.

4. The method for directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method according to claim 1, characterized in that: The alkaline solid waste described in steps 1 to 4 is a bulk solid waste rich in metal oxides and silicates.

5. The method for directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method according to claim 4, characterized in that: The bulk solid waste rich in metal oxides and silicates is steel slag, fly ash or waste incineration fly ash.

6. The method for directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method according to claim 1, characterized in that: The carbon dioxide gas captured in advance in steps 1 to 3 is carbon dioxide captured from flue gas generated in the production process of a cement plant, a power plant or a metallurgical plant.

7. The method for directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method according to claim 1, characterized in that: When cooling the first reaction tank (22), the second reaction tank (23) and the third reaction tank (24) in steps 1 to 3, the cooling medium is water or air.

8. The method for directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method according to claim 1, characterized in that: The alkaline solid waste circulating carbon dioxide fixation device is composed of a first reaction tank (22), a second reaction tank (23), a third reaction tank (24) and a storage tank (21); The first reaction tank (22) is provided with a first feed port (1) and an exhaust port at the top, and a reaction gas inlet and a carbon dioxide inlet are provided at the bottom of the first reaction tank (22); the second reaction tank (23) is provided with a second feed port (2) and an exhaust port at the top, and a reaction gas inlet and a carbon dioxide inlet are provided at the bottom of the second reaction tank (23); the third reaction tank (24) is provided with a third feed port (3) at the top, and a reaction gas inlet and a carbon dioxide inlet are provided at the bottom of the third feed port (3); The material outlet of the material storage tank (21) is connected to a material conveying pipe (16), and the material conveying pipe (16) is respectively connected to the first feed port (1), the second feed port (2) and the third feed port (3); The exhaust port arranged at the top of the first reaction tank (22) is connected to the reaction gas inlet arranged at the bottom of the second reaction tank (23) via a first reaction tank exhaust pipe (20); a 1# gas valve (4) is arranged on the first reaction tank exhaust pipe (20); a first reaction tank exhaust branch pipe is arranged between the 1# gas valve (4) on the first reaction tank exhaust pipe (20) and the exhaust port arranged at the top of the first reaction tank (22); a 7# gas valve (10) is arranged on the first reaction tank exhaust branch pipe; the exhaust port arranged at the top of the second reaction tank (23) is connected to the reaction gas inlet arranged at the bottom of the third reaction tank (24) via a second reaction tank exhaust pipe (19); a 2# gas valve (5 ), a second reaction tank exhaust branch pipe is arranged between the 2# gas valve (5) on the second reaction tank exhaust pipe (19) and the exhaust port arranged at the top of the second reaction tank (23), and an 8# gas valve (11) is arranged on the second reaction tank exhaust branch pipe; the exhaust port arranged at the top of the third reaction tank (24) is connected to the reaction gas inlet arranged at the bottom of the first reaction tank (22) through the third reaction tank exhaust pipe (17), and a 3# gas valve (6) is arranged on the third reaction tank exhaust pipe (17); a third reaction tank exhaust branch pipe is arranged between the 3# gas valve (6) on the third reaction tank exhaust pipe (17) and the exhaust port arranged at the top of the third reaction tank (24), and a 9# gas valve (12) is arranged on the third reaction tank exhaust branch pipe; The carbon dioxide inlet port provided at the bottom of the first reaction tank (22) is connected to a carbon dioxide inlet pipe, and a 4# gas valve (7) is provided on the carbon dioxide inlet pipe at the bottom of the first reaction tank (22); the carbon dioxide inlet port provided at the bottom of the second reaction tank (23) is connected to a carbon dioxide inlet pipe, and a 5# gas valve (8) is provided on the carbon dioxide inlet pipe at the bottom of the second reaction tank (23); the carbon dioxide inlet port provided at the bottom of the third reaction tank (24) is connected to a carbon dioxide inlet pipe, and a 6# gas valve (9) is provided on the carbon dioxide inlet pipe at the bottom of the third reaction tank (24); the carbon dioxide inlet pipe at the bottom of the first reaction tank (22), the carbon dioxide inlet pipe at the bottom of the second reaction tank (23), and the carbon dioxide inlet pipe at the bottom of the third reaction tank (24) are respectively connected to a carbon dioxide inlet main pipe (18).

9. The method for directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method according to claim 8, characterized in that: A discharge pipe is provided at the bottom of the first reaction tank (22), a discharge pipe is provided at the bottom of the second reaction tank (23), and a discharge pipe is provided at the bottom of the second reaction tank (23).

10. The method for directly recycling and fixing carbon dioxide in flue gas by using alkaline solid waste semi-dry method according to claim 9, characterized in that: A 1# discharge valve (13) is provided on the discharge pipe arranged at the bottom of the first reaction tank (22), a 2# discharge valve (14) is provided on the discharge pipe arranged at the bottom of the second reaction tank (23), and a 3# discharge valve (15) is provided on the discharge pipe arranged at the bottom of the third reaction tank (24).

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