A dechlorination composition, a high-temperature flue gas dechlorination agent containing the dechlorination composition, and a preparation method thereof

Abstract

The present invention discloses a dechlorination composition, a high-temperature flue gas dechlorination agent containing the dechlorination composition, and a preparation method thereof. The dechlorination composition is composed of the following raw materials in percentage by weight: 5-45% red mud, 10-60% white mud, and 15-70% carbide slag. The high-temperature flue gas dechlorination agent comprises a binder, a pore-enlarging agent, and the dechlorination composition. The present invention utilizes solid wastes (red mud, white mud, and carbide slag) as primary materials to prepare the dechlorination agent, achieving comprehensive utilization of solid waste while reducing the cost of the dechlorination agent. The dechlorination agent also has advantages such as high chlorine capacity and strong adsorption capacity, making it suitable for dechlorination of high-temperature flue gas.

Description

Technical Field

[0001] The present invention relates to the technical field of gas phase dechlorination, and in particular to a dechlorination composition, a high-temperature flue gas dechlorination agent containing the dechlorination composition, and a preparation method thereof. Background Art

[0002] Methods for treating chlorine-containing waste primarily include landfill and incineration. Incineration, with its advantages of volume reduction, harmlessness, and resource recovery, has been widely used in recent years. However, from an environmental perspective, the chlorine-containing flue gas produced by incineration can corrode equipment. Furthermore, after undergoing multi-stage heat exchange and cooling (below 300-400°C), the flue gas carries the risk of generating toxic substances such as dioxins, further harming the ecological environment. Therefore, dechlorination of high-temperature incineration flue gas is of great significance.

[0003] White mud is an alkaline waste residue discharged during industrial alkali production and alkali treatment, with its main components being CaCO3 and CaCl2. Red mud is an alkaline waste residue produced by the aluminum smelting industry, containing a variety of metal oxides such as Fe2O3, CaO, NaO, and MgO, as well as large amounts of SiO2, Al2O3, and other substances that provide skeletal support. Carbide slag is the residue produced during the hydrolysis of calcium carbide to obtain acetylene gas, with its main components being Ca(OH)2, along with small amounts of CaCO3, CaSO4, and Mg(OH)2. These three industrial solid wastes, white mud, red mud, and carbide slag, contain large amounts of calcium-based substances and are excellent dechlorination materials. Their use in the preparation of dechlorination agents can achieve waste-to-waste treatment, which is of great significance.

[0004] Reference 1: "Preparation of blast furnace top gas dechlorination agent using red mud and slaked lime as active components", author: Hu Xuewu.

[0005] Reference 1 discloses a dechlorinator containing slaked lime as the primary active ingredient, rubidium oxide as an auxiliary active agent, and a small amount of red mud. The red mud content is relatively low, approximately 15%. This dechlorinator has an active temperature of approximately 150°C and is unsuitable for high-temperature flue gas dechlorination.

[0006] Reference 2: "Effect of calcium-based waste on dechlorination of biomass combustion", author: Li Shijie.

[0007] Reference 2 describes the use of three calcium-based wastes, red mud, white mud, and carbide slag, as dechlorinating agents to remove hydrogen chloride from biomass combustion flue gas. The results indicate that all three materials are excellent high-temperature dechlorination materials. However, the paper does not examine the treatment of the three calcium-based wastes and does not investigate their combined use, resulting in a relatively low chlorine capacity.

[0008] Reference 3: Chinese patent document with patent publication number CN202110718423.7.

[0009] Reference 3 discloses a dechlorinating agent for blast furnace gas. The dechlorinating agent is primarily composed of calcium hydroxide, calcium carbonate, and a carrier material, with small amounts of zinc oxide, red mud, and carbide slag added. The red mud and carbide slag content is less than 10%, resulting in a high cost. Furthermore, the dechlorinating agent is primarily suitable for dechlorinating low-temperature flue gas (20-150°C) and is not suitable for dechlorinating high-temperature flue gas. Summary of the Invention

[0010] The purpose of the present invention is to solve the problems existing in the prior art and provide a dechlorination composition, a high-temperature flue gas dechlorination agent containing the dechlorination composition and a preparation method thereof.

[0011] In order to solve the above technical problems, the present invention adopts the following technical solution: a dechlorination composition, which is composed of the following raw materials in weight percentage: 5-45% red mud, 10-60% white mud and 15-70% carbide slag.

[0012] As a further optimization of the dechlorination composition of the present invention: the red mud is Bayer process red mud or combined process red mud.

[0013] A high-temperature flue gas dechlorination agent consists of a binder, a pore-enlarging agent and the above-mentioned dechlorination composition.

[0014] As a further optimization of the high-temperature flue gas dechlorination agent of the present invention: the dechlorination agent is a spherical dechlorination agent with a particle size of 0.5 to 2.5 mm.

[0015] As a further optimization of the high-temperature flue gas dechlorination agent of the present invention: the binder is at least one of aluminum sol, silica sol, methyl cellulose, kaolin and attapulgite.

[0016] As a further optimization of the high-temperature flue gas dechlorination agent of the present invention: the pore-enlarging agent is at least one of polyethylene glycol, urea, coconut shell and sawdust.

[0017] As a further optimization of the high-temperature flue gas dechlorination agent of the present invention, it is composed of the following raw materials in weight percentage: 5-45% red mud, 10-60% white mud, 15-70% carbide slag, 3-20% binder and 2-15% pore expander.

[0018] As a further optimization of the high-temperature flue gas dechlorination agent of the present invention, it is composed of the following raw materials in weight percentage: 15-30% red mud, 20-45% white mud, 25-55% carbide slag, 5-15% binder and 4-10% pore expander.

[0019] A method for preparing a high-temperature flue gas dechlorination agent comprises the following steps:

[0020] 1) Take red mud, white mud, carbide slag, binder and pore-enlarging agent in proportion, crush the red mud, white mud and carbide slag, sieve them and dry them to constant weight for later use;

[0021] 2) adding red mud and carbide slag into distilled water and mechanically mixing them to obtain a first mixture;

[0022] 3) Add white mud to distilled water and stir evenly, then add dilute acid dropwise until no bubbles are generated, and then add alkali solution to adjust the pH to 8-11 to obtain white mud slurry;

[0023] 4) adding the white mud slurry to the first mixture and stirring evenly to obtain a second mixture;

[0024] 5) adding a binder and a pore-enlarging agent to the second mixture, and adding distilled water to a total solid-liquid ratio of 1:8, and stirring to obtain a third mixture;

[0025] 6) adding the third mixed material into a reactor and heating the mixture to obtain a dechlorinating agent gel;

[0026] 7) Drying and calcining the dechlorination agent gel to obtain the dechlorination agent.

[0027] As a further optimization of the preparation method of the high-temperature flue gas dechlorination agent of the present invention: the red mud, white mud and carbide slag are crushed and sieved to below 100 μm.

[0028] As a further optimization of the preparation method of a high-temperature flue gas dechlorination agent of the present invention: the dilute acid is at least one of nitric acid, hydrochloric acid, phosphoric acid and acetic acid, and the dilute acid concentration is 10 mol / L.

[0029] As a further optimization of the preparation method of a high-temperature flue gas dechlorination agent of the present invention: the alkali solution is at least one of a NaOH solution and a KOH solution, and the concentration of the alkali solution is 2 mol / L.

[0030] As a further optimization of the preparation method of a high-temperature flue gas dechlorination agent of the present invention: the third mixed material is added to a stainless steel high-pressure reactor with a tetrafluoroethylene material as an inner liner, and reacted at 0.1-2.1 MPa and 60-120° C. for 2-8 hours to obtain a dechlorination agent gel.

[0031] As a further optimization of the preparation method of a high-temperature flue gas dechlorination agent of the present invention, the dechlorination agent gel is dried at 90-130° C. for 2-5 hours, and then calcined at 350-650° C. for 2-6 hours to obtain the dechlorination agent.

[0032] The present invention has the following beneficial effects: It utilizes solid wastes, including red mud, white mud, and carbide slag, as primary materials to prepare a dechlorination agent, achieving comprehensive utilization of solid waste while reducing the cost of the dechlorination agent. Furthermore, the dechlorination agent has advantages such as high chlorine capacity and strong adsorption capacity, making it suitable for dechlorination of high-temperature flue gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The chlorine penetration capacity diagram of the dechlorinating agent prepared in Examples 1-6;

[0034] Figure 2 The chlorine penetration capacity diagram of the dechlorinating agent prepared in Example 1 and Comparative Example 1;

[0035] Figure 3 The chlorine penetration capacity diagram of the dechlorinating agent prepared in Example 2 and Comparative Example 2;

[0036] Figure 4 The chlorine penetration capacity diagram of the dechlorinating agent prepared in Example 3 and Comparative Example 3;

[0037] Figure 5 The chlorine penetration capacity diagram of the dechlorinating agent prepared in Example 4 and Comparative Example 4;

[0038] Figure 6 The chlorine penetration capacity diagram of the dechlorinating agent prepared in Example 5 and Comparative Example 5;

[0039] Figure 7 This is a photo of the dechlorinating agent prepared in Example 1. DETAILED DESCRIPTION

[0040] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with examples, but the content of the present invention is not limited to the following examples.

[0041] <Example 1>

[0042] Red mud, white mud, and carbide slag were crushed and sieved to less than 100 μm, then dried to constant weight. 14 g of red mud and 47 g of carbide slag were weighed into beaker 1, and an appropriate amount of distilled water was added before mechanical mixing. 26 g of white mud was weighed into beaker 2, and an equal amount of distilled water was added to prepare a white mud slurry. Subsequently, an appropriate amount of 10 mol / L hydrochloric acid solution was added dropwise until no bubbles formed, and an appropriate amount of 2 mol / L NaOH solution was added to a pH of 8. The white mud slurry in beaker 2 was added to beaker 1, along with 13 g of kaolin and 7 g of polyethylene glycol. Distilled water was added to a total solid-to-liquid ratio of 1:8, and the mixture was stirred for 6 hours. The mixture in beaker 1 was added to a stainless steel autoclave lined with a tetrafluoroethylene liner and reacted at 1.3 MPa and 80°C for 2.5 hours to produce a dechlorination gel. The dechlorination agent gel was dried at 110℃ for 3h and then calcined at 500℃ for 3.5h to obtain a spherical dechlorination agent with a particle size of 0.5-2.5mm. The actual photo is shown in the figure. Figure 7 shown.

[0043] <Example 2>

[0044] Red mud, white mud, and carbide slag were crushed and sieved to less than 100 μm, then dried to constant weight. 27 g of red mud and 30 g of carbide slag were weighed into beaker 1, and an appropriate amount of distilled water was added before mechanical mixing. 31 g of white mud was weighed into beaker 2, and an equal amount of distilled water was added to prepare a white mud slurry. Subsequently, an appropriate amount of 10 mol / L nitric acid solution was added dropwise until no bubbles formed, and an appropriate amount of 2 mol / L KOH solution was added to a pH of 11. The white mud slurry in beaker 2 was added to beaker 1, along with 12 g of silica sol and 10 g of urea. Distilled water was added to a total solid-to-liquid ratio of 1:8, and the mixture was stirred for 6 hours. The mixture in beaker 1 was added to a stainless steel autoclave lined with a tetrafluoroethylene liner and reacted at 0.5 MPa and 110°C for 6 hours to produce a dechlorination gel. The dechlorination agent gel was dried at 100℃ for 4h and then calcined at 450℃ for 5h to obtain a spherical dechlorination agent with a particle size of 0.5-2.5mm.

[0045] <Example 3>

[0046] Red mud, white mud, and carbide slag were crushed, sieved to less than 100 μm, and dried to constant weight. 23 g of red mud and 52 g of carbide slag were weighed into beaker 1, and an appropriate amount of distilled water was added, followed by mechanical mixing. 17 g of white mud was weighed into beaker 2, and an equal amount of distilled water was added to prepare a white mud slurry. Subsequently, an appropriate amount of 10 mol / L acetic acid solution was added dropwise until no bubbles formed, and an appropriate amount of 2 mol / L KOH solution was added to a pH of 10. The white mud slurry from beaker 2 was added to beaker 1, along with 8 g of attapulgite and 5 g of coconut shell. Distilled water was added to a total solid-to-liquid ratio of 1:8, and the mixture was stirred for 6 hours. The mixture from beaker 1 was placed in a stainless steel autoclave with a Teflon liner and reacted at 2.0 MPa and 60°C for 4.5 hours to produce a dechlorination gel. The dechlorination agent gel was dried at 125° C. for 2.5 h and then calcined at 650° C. for 2 h to obtain a spherical dechlorination agent with a particle size of 0.5 to 2.5 mm.

[0047] <Example 4>

[0048] Red mud, white mud, and carbide slag were crushed and sieved to less than 100 μm, then dried to constant weight. 10 g of red mud and 36 g of carbide slag were weighed into beaker 1, and an appropriate amount of distilled water was added before mechanical mixing. 39 g of white mud was weighed into beaker 2, and an equal amount of distilled water was added to prepare a white mud slurry. Subsequently, an appropriate amount of 10 mol / L nitric acid solution was added dropwise until no bubbles formed, and an appropriate amount of 2 mol / L NaOH solution was added to a pH of 9. The white mud slurry in beaker 2 was added to beaker 1, along with 15 g of attapulgite and 4 g of coconut shell. Distilled water was added to a total solid-to-liquid ratio of 1:8, and the mixture was stirred for 6 hours. The mixture in beaker 1 was added to a stainless steel autoclave lined with a tetrafluoroethylene liner and reacted at 0.2 MPa and 120°C for 8 hours to produce a dechlorination gel. The dechlorination agent gel was dried at 90°C for 5 hours and then calcined at 550°C for 4 hours to obtain a spherical dechlorination agent with a particle size of 0.5 to 2.5 mm.

[0049] <Example 5>

[0050] Red mud, white mud, and carbide slag were crushed and sieved to less than 100 μm, then dried to constant weight. 26 g of red mud and 25 g of carbide slag were weighed into beaker 1, and an appropriate amount of distilled water was added before mechanical mixing. 44 g of white mud was weighed into beaker 2, and an equal amount of distilled water was added to prepare a white mud slurry. Subsequently, an appropriate amount of 10 mol / L hydrochloric acid solution was added dropwise until no bubbles formed, and an appropriate amount of 2 mol / L KOH solution was added to a pH of 10. The white mud slurry in beaker 2 was added to beaker 1, along with 5 g of methyl cellulose and 8 g of urea. Distilled water was added to a total solid-to-liquid ratio of 1:8, and the mixture was stirred for 6 hours. The mixture in beaker 1 was placed in a stainless steel autoclave lined with a tetrafluoroethylene liner and reacted at 1.7 MPa and 75°C for 5 hours to produce a dechlorination gel. The dechlorination agent gel was dried at 105°C for 3.5 hours and then calcined at 400°C for 3 hours to obtain a spherical dechlorination agent with a particle size of 0.5 to 2.5 mm.

[0051] <Example 6>

[0052] Red mud, white mud, and carbide slag were crushed and sieved to less than 100 μm, then dried to constant weight. 19 g of red mud and 49 g of carbide slag were weighed into beaker 1, and an appropriate amount of distilled water was added before mechanical mixing. 22 g of white mud was weighed into beaker 2, and an equal amount of distilled water was added to prepare a white mud slurry. Subsequently, an appropriate amount of 10 mol / L acetic acid solution was added dropwise until no bubbles formed, and an appropriate amount of 2 mol / L NaOH solution was added to a pH of 8-11. The white mud slurry in beaker 2 was added to beaker 1, along with 10 g of aluminum sol and 7 g of sawdust. Distilled water was added to a total solid-to-liquid ratio of 1:8, and the mixture was stirred for 6 hours. The mixture in beaker 1 was placed in a stainless steel autoclave lined with a tetrafluoroethylene liner and reacted at 0.9 MPa and 105°C for 7 hours to produce a dechlorination gel. The dechlorination agent gel was dried at 130° C. for 2 h and then calcined at 600° C. for 2.5 h to obtain a spherical dechlorination agent with a particle size of 0.5 to 2.5 mm.

[0053] Comparative Example 1

[0054] Crush and sieve the white mud and carbide slag to less than 100 μm, then dry to constant weight. Weigh 54 g of carbide slag into beaker 1, add an appropriate amount of distilled water, and mechanically mix thoroughly. Weigh 33 g of white mud into beaker 2, add an equal amount of distilled water to prepare a white mud slurry, then add an appropriate amount of 10 mol / L hydrochloric acid solution dropwise until no bubbles form, and add an appropriate amount of 2 mol / L NaOH solution to a pH of 8. The white mud slurry in beaker 2 is added to beaker 1, along with 13 g of kaolin and 7 g of polyethylene glycol. Distilled water is added to a total solid-to-liquid ratio of 1:8, and stirred for 6 hours. The mixture in beaker 1 is placed in a stainless steel autoclave with a Teflon liner and reacted at 1.3 MPa and 80°C for 2.5 hours to produce a dechlorination gel. The dechlorination agent gel was dried at 110° C. for 3 h and then calcined at 500° C. for 3.5 h to obtain a spherical dechlorination agent with a particle size of 0.5 to 2.5 mm.

[0055] Comparative Example 2

[0056] The red mud and white mud raw materials were crushed and sieved to less than 100 μm, and dried to constant weight. 42 g of red mud was weighed into beaker 1, and an appropriate amount of distilled water was added, followed by mechanical mixing. 46 g of white mud was weighed into beaker 2, and an equal amount of distilled water was added to prepare a white mud slurry. Subsequently, an appropriate amount of 10 mol / L nitric acid solution was added dropwise until no bubbles were generated, and an appropriate amount of 2 mol / L KOH solution was added to a pH of 11. The white mud slurry in beaker 2 was added to beaker 1, along with 12 g of silica sol and 10 g of urea, and distilled water was added to a total solid-liquid ratio of 1:8. The mixture was stirred for 6 hours. The mixture in beaker 1 was added to a stainless steel autoclave with a tetrafluoroethylene liner and reacted at 0.5 MPa and 110°C for 6 hours to obtain a dechlorination agent gel. The dechlorination agent gel was dried at 100°C for 4 hours and then calcined at 450°C for 5 hours to obtain a spherical dechlorination agent with a particle size of 0.5 to 2.5 mm.

[0057] Comparative Example 3

[0058] Crush and sieve red mud and carbide slag to less than 100 μm, then dry to constant weight. Weigh 32 g of red mud and 60 g of carbide slag into beaker 1, add an appropriate amount of distilled water, and mechanically mix thoroughly. Add 8 g of attapulgite and 5 g of coconut shell to beaker 1, and add distilled water to a total solid-to-liquid ratio of 1:8. Stir for 6 hours. The mixture in beaker 1 is added to a stainless steel autoclave lined with tetrafluoroethylene. React at 2.0 MPa and 60°C for 4.5 hours to produce a dechlorination agent gel. Dry the dechlorination agent gel at 125°C for 2.5 hours and then calcine at 650°C for 2 hours to produce spherical dechlorination agent with a particle size of 0.5 to 2.5 mm.

[0059] Comparative Example 4

[0060] Red mud, white mud, and carbide slag were crushed and sieved to less than 100 μm, then dried to constant weight. 10 g of red mud and 36 g of carbide slag were weighed into beaker 1, and an appropriate amount of distilled water was added before mechanical mixing. 39 g of white mud was weighed into beaker 2, and an equal amount of distilled water was added to prepare a white mud slurry. Subsequently, an appropriate amount of 10 mol / L nitric acid solution was added dropwise until no bubbles formed, and an appropriate amount of 2 mol / L NaOH solution was added to a pH of 9. The white mud slurry in beaker 2 was added to beaker 1, along with 15 g of attapulgite and 4 g of coconut shell. Distilled water was added to a total solid-to-liquid ratio of 1:8, and stirred for 6 hours. The mixture in beaker 1 was dried at 90°C for 5 hours and then calcined at 550°C for 4 hours to produce a spherical dechlorination agent with a particle size of 0.5 to 2.5 mm.

[0061] Comparative Example 5

[0062] Red mud, white mud, and carbide slag were crushed and sieved to less than 100 μm, then dried to constant weight. 26 g of red mud and 25 g of carbide slag were weighed into beaker 1, and an appropriate amount of distilled water was added before mechanical mixing. 44 g of white mud was weighed into beaker 2, and an equal amount of distilled water was added to prepare a white mud slurry. Subsequently, an appropriate amount of 10 mol / L hydrochloric acid solution was added dropwise until no bubbles formed, and an appropriate amount of 2 mol / L KOH solution was added to a pH of 10. The white mud slurry in beaker 2 was added to beaker 1, along with 5 g of methyl cellulose and 8 g of urea. Distilled water was added to a total solid-to-liquid ratio of 1:8, and the mixture was stirred for 6 hours. The mixture in beaker 1 was placed in a stainless steel autoclave lined with a tetrafluoroethylene liner and reacted at 2.5 MPa and 150°C for 10 hours to produce a dechlorination gel. The dechlorination agent gel was dried at 105°C for 3.5 hours and then calcined at 400°C for 3 hours to obtain a spherical dechlorination agent with a particle size of 0.5 to 2.5 mm.

[0063] <Dechlorination Performance Comparison>

[0064] The performance of the dechlorination agent was tested by the following method: the dechlorination agents prepared in Examples 1-6 and Comparative Examples 1-5 were placed in a fixed bed evaluation device, the HCl concentration in the inlet flue gas was 2000 ppm, the air space was 6000 h -1 , the reaction temperature is 300~800℃, and the results are as follows Figure 1-6 shown.

[0065] Depend on Figure 1 It can be seen that the dechlorinating agent prepared by the present invention has a chlorine penetration capacity higher than 32% at a reaction temperature of 400-800°C, and higher than 40% at a reaction temperature of 550-600°C. The dechlorinating agent prepared in Example 5 has a chlorine penetration capacity higher than 40% at a reaction temperature of 500-700°C, and the highest chlorine penetration capacity is 43.8% at 550°C.

[0066] Depend on Figure 2-6 It can be seen that:

[0067] Comparing the dechlorination effects of Example 1 and Comparative Example 1, no red mud was added during the preparation of the dechlorination agent in Comparative Example 1, and the maximum breakthrough chlorine capacity was reduced from 41.2% to 26.0%.

[0068] Comparing the dechlorination effects of Example 2 and Comparative Example 2, no carbide slag was added during the preparation of the dechlorination agent in Comparative Example 2, and the maximum penetration chlorine capacity was reduced from 42.0% to 24.0%.

[0069] Comparing the dechlorination effects of Example 3 and Comparative Example 3, no white mud was added during the preparation of the dechlorination agent in Comparative Example 3, and the maximum penetration chlorine capacity was reduced from 42.2% to 23.5%.

[0070] Comparing the dechlorination effects of Example 4 and Comparative Example 4, the dechlorination agent in Comparative Example 4 was not processed in a high-pressure reactor during its preparation process, and the maximum breakthrough chlorine capacity was reduced from 40.9% to 20.4%.

[0071] Comparing the dechlorination effects of Example 5 and Comparative Example 5, the high-pressure reactor treatment conditions were adjusted during the preparation of the dechlorination agent in Comparative Example 5, and high-pressure and high-temperature treatment was adopted, and the maximum breakthrough chlorine capacity was reduced from 42.0% to 33.5%.

[0072] This is because during the hydrothermal synthesis process of the dechlorinating agent of the present invention, the Ca in the red mud, white mud and carbide slag forms gel-like hydrated silicate and hydrated aluminate on the SiO2 and Al2O3 in the red mud, which have a large specific surface area. In addition, substances such as Fe, Mg, and Cu in the red mud will form composite nanomaterials with Ca, which stimulate the activity of the dechlorinating agent, thereby improving the adsorption reaction activity of the dechlorinating agent.

[0073] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a high-temperature flue gas dechlorination agent, characterized in that: The following steps are involved: 1) Take red mud, white mud, carbide slag, binder and pore-enlarging agent in proportion, crush the red mud, white mud and carbide slag, sieve them and dry them to constant weight for later use; The weight percentages of the raw materials are: 5-45% red mud, 10-60% white mud, 15-70% carbide slag, 3-20% binder and 2-15% pore expanding agent; 2) adding red mud and carbide slag into distilled water and mechanically mixing them to obtain a first mixture; 3) Add white mud to distilled water and stir evenly, then add dilute acid dropwise until no bubbles are generated, and then add alkali solution to adjust the pH to 8-11 to obtain white mud slurry; 4) adding the white mud slurry to the first mixture and stirring evenly to obtain a second mixture; 5) adding a binder and a pore-enlarging agent to the second mixture, and adding distilled water to a total solid-liquid ratio of 1:8, and stirring to obtain a third mixture; 6) adding the third mixed material into a reactor and heating the mixture to obtain a dechlorinating agent gel; 7) Drying and calcining the dechlorination agent gel to obtain the dechlorination agent.

2. The method for preparing a high-temperature flue gas dechlorination agent according to claim 1, wherein: The red mud is Bayer process red mud or combined process red mud.

3. The method for preparing a high-temperature flue gas dechlorination agent according to claim 1, wherein: The prepared dechlorinating agent is a spherical dechlorinating agent with a particle size of 0.5 to 2.5 mm.

4. The method for preparing a high-temperature flue gas dechlorination agent according to claim 1, wherein: The binder is at least one of aluminum sol, silica sol, methyl cellulose, kaolin and attapulgite.

5. The method for preparing a high-temperature flue gas dechlorination agent according to claim 1, wherein: The pore-enlarging agent is at least one of polyethylene glycol, urea, coconut shell and sawdust.

6. The method for preparing a high-temperature flue gas dechlorination agent according to claim 1, wherein: The weight percentages of the raw materials are: 15-30% red mud, 20-45% white mud, 25-55% carbide slag, 5-15% binder and 4-10% pore-enlarging agent.

7. The method for preparing a high-temperature flue gas dechlorination agent according to claim 1, wherein: The red mud, white mud and carbide slag are crushed and sieved to below 100μm.

8. The method for preparing a high-temperature flue gas dechlorination agent according to claim 1, wherein: The dilute acid is at least one of nitric acid, hydrochloric acid, phosphoric acid and acetic acid, and the concentration of the dilute acid is 10 mol / L.

9. The method for preparing a high-temperature flue gas dechlorination agent according to claim 1, wherein: The alkali solution is at least one of a NaOH solution and a KOH solution, and the concentration of the alkali solution is 2 mol / L.

10. The method for preparing a high-temperature flue gas dechlorination agent according to claim 1, wherein: The third mixed material is added into a stainless steel high-pressure reactor with a tetrafluoroethylene inner liner, and reacted at 0.1-2.1 MPa and 60-120° C. for 2-8 hours to obtain a dechlorination agent gel.

11. The method for preparing a high-temperature flue gas dechlorination agent according to claim 1, wherein: The dechlorination agent gel is dried at 90-130° C. for 2-5 hours, and then calcined at 350-650° C. for 2-6 hours to obtain the dechlorination agent.

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