Method for preparing flue gas desulfurization gypsum through catalytic oxidation

Abstract

The invention discloses a method for preparing flue gas desulfurization gypsum through catalytic oxidation, which is characterized in that limestone slurry with corresponding density is prepared from a limestone raw material as a raw material, is subjected to strong acid oxidation treatment and then is subjected to catalytic oxidation treatment by manganese salt to prepare the flue gas desulfurization gypsum, so that the prepared desulfurization gypsum product has low calcium sulfite content and high desulfurization efficiency. The conversion rate of the calcium sulfate gypsum product is high, the equipment investment is low, the manufacturing cost is lower, and the economic and environmental benefits are higher.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas desulfurization solid waste treatment, and specifically to a method for preparing flue gas desulfurization gypsum, and in particular to a method for preparing flue gas desulfurization gypsum by catalytic oxidation. Background Art

[0002] In the process of pyrometallurgical smelting of nonferrous metals, a large amount of sulfur-containing flue gas is generally produced, which needs to be absorbed and treated, and the tail gas can only be discharged after meeting the qualified standards. The desulfurizers used in the industry are mainly limestone, quicklime and slaked lime. The preparation method of limestone-based desulfurization gypsum in the industry usually pre-washes the system flue gas, then passes through the primary and secondary desulfurization systems, and then enters the chimney after absorption by alkaline solution spraying. This method can achieve standard flue gas emissions through multi-stage absorption, and at the same time prepare flue gas desulfurization gypsum as a by-product for sale. However, this method has the disadvantages of large equipment investment, too long gypsum oxidation time, and too high calcium sulfite content in the prepared desulfurization gypsum.

[0003] Chinese Patent Publication No. CN 110304647 A, Invention Name "A Method and System for Preparing Desulfurized Gypsum from Dry Desulfurized Ash Using Waste Acid from Society" The present invention provides a method and system for preparing desulfurized gypsum from dry desulfurized ash using waste acid from society, comprising the following steps: mixing water and dry desulfurized ash, stirring to prepare dry desulfurized ash solution; adding waste acid from society to the dry desulfurized ash solution, introducing oxygen and stirring to carry out oxidation reaction; adding the mixed solution to a solid-liquid separation device for solid-liquid separation; the solid separated from the solid-liquid separation enters a distillation device; the solid is separated from the solid-liquid separation in the distillation device, and the distilled solid is used as desulfurized gypsum. The conversion rate of CaSO3 in the dry desulfurized ash of the present invention to desulfurized gypsum CaSO4 is more than 99%, and the conversion time is ≤1.5 hours, which meets the requirements of JC / T2074-2011 "Flue Gas Desulfurized Gypsum". The present invention makes full use of waste acid from society, achieving the purpose of treating waste with waste; solves the problem of calcium sulfite conversion and simultaneously solves the problem of calcium chloride and calcium nitrite in desulfurized ash; and solves the problem of secondary pollution caused by sulfur dioxide emission generated during the reaction process.

[0004] There is also an application publication number CN 117164260 A, the invention name is "A method for preparing semi-hydrated gypsum from flue gas desulfurization gypsum and its application", the present invention discloses a method for preparing semi-hydrated gypsum from flue gas desulfurization gypsum and its application, the preparation steps of which include: S1: mechanical treatment; taking gypsum, a byproduct of flue gas industry of power plant, grinding it, sieving it, and obtaining a particle size of 90-100 μ m gypsum powder; S2: crystallization treatment; take 5-8 parts of gypsum powder, 1-2 parts of carbon powder and 1-3 parts of modified crystal-transforming agent, put them into 10-15 parts of water, heat them to 40-70°C, stir them for 2-5 minutes to evenly disperse them, and obtain a crystallization solution with a free fiber assembly; S3: solid-phase fiber assembly treatment; take 3-4 parts of NdMnO3 as a negative thermal expansion material and add them to the crystallization solution, and through a high-temperature solid-phase method, NdMnO3 is coated on the surface of the fiber assembly, and after heating and stirring, a gypsum solution with a solid-phase fiber assembly is obtained; S4: high-strength fiber mixing treatment; the present invention has the effects of high strength and strong bonding force.

[0005] The invention discloses a method for preparing desulfurized gypsum by simulating flue gas desulfurization process in a laboratory, wherein a desulfurizer and impurity ions are introduced into raw materials and placed together in a reactor filled with deionized water to form a slurry, sulfur dioxide gas and oxygen are introduced into the slurry by bubbling, and flue gas desulfurization gypsum doped with impurity ions is prepared by chemical reaction of ions in the slurry. The invention can reproduce the synthesis process of flue gas desulfurization gypsum more realistically, and can provide theoretical and technical support for in-depth research and solution of various properties of flue gas desulfurization gypsum under laboratory conditions, and promote the resource utilization of flue gas desulfurization gypsum.

[0006] It can be seen from the technical solutions disclosed in the above patent applications that the calcium sulfite generated after limestone desulfurization in the comparative documents and the prior art solutions oxidizes slowly or is not easily oxidized, and the prepared desulfurized gypsum has a relatively high calcium sulfite content. In addition, the equipment investment is relatively large, the gypsum aeration oxidation time is relatively long, and the oxidation efficiency of calcium sulfite is low, so its production cost is correspondingly high.

[0007] Therefore, a method for preparing flue gas desulfurization gypsum by catalytic oxidation is provided; limestone raw material is prepared into limestone slurry of corresponding density after emulsification as raw material, after strong acid oxidation treatment, and then catalytic oxidation treatment by manganese salt, the prepared flue gas desulfurization gypsum product has low calcium sulfite content, high conversion rate, less equipment investment, low manufacturing cost, high economic and environmental benefits, and saves production costs to meet the requirements of environmental protection circular economy. Summary of the invention

[0008] The present invention provides a method for preparing flue gas desulfurization gypsum by catalytic oxidation. The method uses limestone raw material, limestone slurry with corresponding density as raw material, and is subjected to strong acid oxidation treatment and then catalytic oxidation treatment by manganese salt to prepare the flue gas desulfurization gypsum. The prepared desulfurization gypsum product has low calcium sulfite content and high conversion rate into calcium sulfate gypsum product, and has low equipment investment, low manufacturing cost and high economic and environmental benefits.

[0009] The present invention provides a method for preparing flue gas desulfurization gypsum by catalytic oxidation, which uses limestone raw material and limestone slurry of corresponding density as raw material, and comprises the following method steps: 1) Acidification and oxidation treatment: place the limestone slurry in an aeration oxidation tank, gradually add sulfuric acid solution to the limestone slurry under aeration oxidation stirring conditions, perform aeration oxidation stirring reaction, and stop adding acid when the pH of the reaction solution is controlled to be 3.2-3.7 to obtain calcium sulfate slurry. 2) Manganese salt catalytic oxidation, Add manganese salt to the calcium sulfate slurry in step 1) for catalytic oxidation reaction for 2.5-4.2 hours to obtain manganese salt oxidized gypsum slurry. Filter the manganese salt oxidized gypsum slurry to obtain manganese salt oxidized gypsum slurry slag. After the calcium sulfite and water in the manganese salt oxidized gypsum slurry slag are tested to be qualified, the manganese salt oxidized gypsum slurry slag is made into a mixed liquid and then continued to oxidize for 5-7 hours to obtain desulfurized gypsum slurry. Filter to obtain desulfurized gypsum slurry slag. After the test is qualified, the sulfur gypsum slurry slag is filtered and dried to obtain a flue gas desulfurization gypsum product.

[0010] The method for preparing flue gas desulfurization gypsum by catalytic oxidation, wherein: step 1) limestone slurry with an effective calcium carbonate content of ≥95% and a limestone raw material with a mesh size of ≥325 is prepared into a slurry of corresponding density, which enters the desulfurization system and is pneumatically emulsified into a gypsum slurry liquid.

[0011] Preferably, in step 1), the limestone slurry is desulfurized to form a gypsum slurry liquid, and the gypsum slurry liquid is then placed in an aeration oxidation tank for acidification and oxidation treatment, and the acidification and oxidation treatment time is controlled to be 15-35 minutes.

[0012] The method for preparing flue gas desulfurization gypsum by catalytic oxidation, wherein the manganese salt in step 2) is potassium permanganate or sodium permanganate.

[0013] The method for preparing flue gas desulfurization gypsum by catalytic oxidation, wherein the amount of manganese salt added is controlled so that the manganese content in the desulfurization gypsum slurry reaches 0.01-0.02 mol / L, the addition is stopped, and then the aeration and stirring reaction is continued for 3-4 hours.

[0014] Preferably, in step 2), the manganese salt oxidized gypsum slurry is filtered to obtain manganese salt oxidized gypsum slurry residue, and the moisture content of the manganese salt oxidized gypsum slurry residue is controlled to be 28-35wt%, and the calcium sulfite content is controlled to be 1.6-4.1wt%.

[0015] Furthermore, in step 2), the moisture content in the desulfurized gypsum slurry residue is controlled to be 18-20wt%, and the calcium sulfite content is controlled to be 0.5-1.5wt%.

[0016] The invention discloses a method for preparing flue gas desulfurization gypsum by catalytic oxidation, which is mainly aimed at the situation that the calcium sulfite content of the desulfurization gypsum prepared in the industry is too high, which is mainly reflected in the problem that the calcium sulfite generated after limestone desulfurization is slowly oxidized or not easily oxidized, that is, how to achieve the problem that the calcium sulfite content of the desulfurization gypsum prepared in the industry is too high and to be quickly oxidized into calcium sulfate, etc.; the invention adopts a strong acid such as sulfuric acid to first perform acid oxidation treatment, and then uses a small amount of permanganate to further perform oxidation treatment, and then performs aeration oxidation stirring treatment, so that the calcium sulfite content in the prepared desulfurization gypsum product is low.

[0017] The present method also has the following remarkable effects and characteristics: First, the equipment investment is small, the manufacturing cost is low, and there is no need to install a flue gas pre-washing system during the production desulfurization and oxidation processes, which reduces equipment investment and production energy consumption; Second, the raw materials used in the production of the present invention are cheap and easily available. Sulfuric acid and manganese salt are both industrial products commonly used in the metallurgical and chemical industries and can be purchased on the market. Third, the production process of the present invention is simple to operate, has a fast oxidation rate and a high conversion rate. The calcium sulfite content in the desulfurized gypsum is significantly reduced after testing. The lowest content is 0.26%, while the existing technology process is more than 70%. The calcium sulfate content in the desulfurized gypsum is greatly increased to about 90%, while the gypsum produced by the existing similar process is only about 10%. Specific test data are shown in the test data table of the embodiment below. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. The present invention is not limited to the embodiments, and each component of the present invention can be obtained commercially.

[0019] The present invention discloses a method for preparing flue gas desulfurization gypsum by catalytic oxidation, which uses limestone raw material and limestone slurry with corresponding density as raw material. The so-called limestone slurry with corresponding density generally refers to the limestone slurry used as a desulfurizer to absorb and treat sulfur-containing flue gas generated in the pyrometallurgical process, so that the tail gas can reach the qualified standard for discharge; It includes the following method steps: 1) Acidification oxidation treatment, placing the limestone slurry in an aeration oxidation tank, gradually adding sulfuric acid solution to the limestone slurry under aeration oxidation stirring conditions, performing aeration oxidation stirring reaction, and stopping the addition of acid when the pH of the reaction solution is controlled to be 3.2-3.7, wherein the limestone slurry has an effective calcium carbonate content of ≥95% and a mesh number of ≥325, and is prepared into a slurry of corresponding density, preferably, entering the desulfurization system for pneumatic emulsification into gypsum slurry liquid; obtaining calcium sulfate slurry liquid; 2) Manganese salt catalytic oxidation, A manganese salt is added to the calcium sulfate slurry in step 1) for catalytic oxidation reaction, wherein the manganese salt is potassium permanganate or sodium permanganate; the time is 2.5-4.2 hours to obtain manganese salt oxidized gypsum slurry, the manganese salt oxidized gypsum slurry is filtered to obtain manganese salt oxidized gypsum slurry slag, and after the calcium sulfite and water in the manganese salt oxidized gypsum slurry slag are tested to be qualified, the manganese salt oxidized gypsum slurry slag is made into a mixed liquid and then the oxidation reaction is continued for 5-7 hours to obtain desulfurized gypsum slurry, which is filtered to obtain desulfurized gypsum slurry slag, the desulfurized gypsum slurry slag is tested, and if qualified, the sulfur gypsum slurry slag is filtered and dried to obtain a flue gas desulfurization gypsum product.

[0020] Preferably, in step 1), the limestone slurry is desulfurized to form a gypsum slurry liquid, and the gypsum slurry liquid is then placed in an aeration oxidation tank for acidification and oxidation treatment, and the acidification and oxidation treatment time is controlled to be 15-35 minutes.

[0021] Preferably, the amount of manganese salt added is controlled so that when the manganese content in the desulfurized gypsum slurry reaches 0.01-0.02 mol / L, the addition is stopped, and then the aeration and stirring reaction is continued for 3-4 hours.

[0022] Preferably, in step 2), the manganese salt oxidized gypsum slurry is filtered to obtain manganese salt oxidized gypsum slurry residue, and the moisture content of the manganese salt oxidized gypsum slurry residue is controlled to be 28-35wt%, and the calcium sulfite content is controlled to be 1.6-4.1wt%.

[0023] Furthermore, in step 2), the moisture content in the desulfurized gypsum slurry residue is controlled to be 18-20wt%, and the calcium sulfite content is controlled to be 0.5-1.5wt%.

[0024] All matters not described in the following embodiments are implemented according to the above specific implementation methods. Example

[0025] The raw materials of each component in this embodiment are all commercially available, in terms of quality or mass ratio.

[0026] The present invention discloses a method for preparing flue gas desulfurization gypsum by catalytic oxidation, which uses limestone raw material and limestone slurry with corresponding density as raw material. The so-called limestone slurry with corresponding density generally refers to the limestone slurry used as a desulfurizer to absorb and treat sulfur-containing flue gas generated in the pyrometallurgical process, so that the tail gas can reach the qualified standard for discharge; It includes the following method steps: 1) Acidification and oxidation treatment, placing the limestone slurry in an aeration and oxidation tank, gradually adding sulfuric acid solution to the limestone slurry under aeration and oxidation stirring conditions, the concentration of the sulfuric acid solution is based on commercially available, generally controlled at 40-60% by mass, and the amount of sulfuric acid solution added is based on the pH reaching the set value range, such as 3.5 in this example; it is carried out under aeration and oxidation stirring reaction conditions, and the acid addition is stopped when the pH of the reaction solution is controlled to be 3.5, the limestone slurry has an effective calcium carbonate content of ≥95% and a mesh number of ≥325, is prepared into a slurry of corresponding density, and then enters the desulfurization system for pneumatic emulsification into gypsum slurry liquid; the limestone slurry is a gypsum slurry liquid after desulfurization treatment, such as controlling the calcium carbonate content in the gypsum slurry liquid to be 45-80Wt%; and then the gypsum slurry liquid is placed in an aeration and oxidation tank for acidification and oxidation treatment, and the acidification and oxidation treatment time is controlled to be 30min to obtain a calcium sulfate slurry liquid; 2) Manganese salt catalytic oxidation, When the pH of the calcium sulfate slurry in step 1) rises to 3.9, a manganese salt is added to the calcium sulfate slurry to carry out a manganese salt catalytic oxidation reaction, wherein the manganese salt is potassium permanganate or sodium permanganate; the amount of manganese salt added is controlled so that the manganese content in the desulfurized gypsum slurry reaches 0.012 mol / L, and then the addition is stopped, and then the aeration and stirring reaction is continued for 3 hours to obtain a manganese salt oxidized gypsum slurry, and the manganese salt oxidized gypsum slurry is filtered to obtain a manganese salt oxidized gypsum slurry residue, and the water content in the manganese salt oxidized gypsum slurry residue is controlled to be 28-35Wt %, and the calcium sulfite content is 1.6-4.1Wt ; After the calcium sulfite and water content in the manganese salt oxidized gypsum slurry residue are tested and found to be qualified, water is added to the manganese salt oxidized gypsum slurry residue to form a mixed solution and then the oxidation reaction is continued for 6 hours to obtain desulfurized gypsum slurry. The desulfurized gypsum slurry is filtered to obtain desulfurized gypsum slurry residue, and the water content in the desulfurized gypsum slurry residue is controlled to be 18-20Wt% and the calcium sulfite content is 1.1Wt%; after the test is qualified, the sulfur gypsum slurry residue is filtered and dried to obtain the flue gas desulfurization gypsum product.

[0027] Embodiment 2, The raw materials of each component in this embodiment are all commercially available. The raw materials of each component in this embodiment are all commercially available.

[0028] The present invention discloses a method for preparing flue gas desulfurization gypsum by catalytic oxidation, which uses limestone raw material and limestone slurry with corresponding density as raw material. The so-called limestone slurry with corresponding density generally refers to the limestone slurry used as a desulfurizer to absorb and treat sulfur-containing flue gas generated in the pyrometallurgical process, so that the tail gas can reach the qualified standard for discharge; It includes the following method steps: 1) Acidification and oxidation treatment, placing the limestone slurry in an aeration oxidation tank, gradually adding sulfuric acid solution to the limestone slurry under aeration oxidation stirring conditions, performing aeration oxidation stirring reaction, and stopping the addition of acid when the pH of the reaction solution is controlled to be 3.7, wherein the limestone slurry has an effective calcium carbonate content of 98% and a limestone raw material with a mesh number of 350, and is prepared into a slurry of corresponding density; the limestone slurry is a gypsum slurry liquid after desulfurization treatment, such as controlling the calcium carbonate content in the gypsum slurry liquid to be 45-80wt%; and then placing the gypsum slurry liquid in an aeration oxidation tank for acidification and oxidation treatment, controlling the acidification and oxidation treatment time to be 30min, to obtain a calcium sulfate slurry liquid; 2) Manganese salt catalytic oxidation, When the pH of the calcium sulfate slurry in step 1) rises to 4.2, a manganese salt is added to the calcium sulfate slurry to carry out a manganese salt catalytic oxidation reaction, wherein the manganese salt is potassium permanganate or sodium permanganate; the amount of manganese salt added is controlled so that the manganese content in the desulfurized gypsum slurry reaches 0.015 mol / L, and then the addition is stopped, and then the aeration and stirring reaction is continued for 3 hours to obtain a manganese salt oxidized gypsum slurry, and the manganese salt oxidized gypsum slurry is filtered to obtain a manganese salt oxidized gypsum slurry residue, and the manganese salt oxidized gypsum slurry is filtered to obtain a manganese salt oxidized gypsum slurry residue, and the water content in the manganese salt oxidized gypsum slurry residue is controlled to be 28-35Wt%, and the calcium sulfite content is controlled to be 1.6-4.1Wt; After the calcium sulfite and water content in the manganese salt oxidized gypsum slurry residue are tested and found to be qualified, the manganese salt oxidized gypsum slurry residue is made into a mixed liquid and then the oxidation reaction is continued for 6 hours to obtain a desulfurized gypsum slurry, which is filtered to obtain a desulfurized gypsum slurry residue. The water content in the desulfurized gypsum slurry residue is controlled to be 18-20wt%, and the calcium sulfite content is 0.78wt%. After the test is qualified, the sulfur gypsum slurry residue is filtered and dried to obtain a flue gas desulfurization gypsum product.

[0029] Embodiment 3, The raw materials of each component in this embodiment are all commercially available. The raw materials of each component in this embodiment are all commercially available.

[0030] The present invention discloses a method for preparing flue gas desulfurization gypsum by catalytic oxidation, which uses limestone raw material and limestone slurry with corresponding density as raw material. The so-called limestone slurry with corresponding density generally refers to the limestone slurry used as a desulfurizer to absorb and treat sulfur-containing flue gas generated in the pyrometallurgical process, so that the tail gas can reach the qualified standard for discharge; It includes the following method steps: 1) Acidification and oxidation treatment, placing the limestone slurry in an aeration oxidation tank, gradually adding sulfuric acid solution to the limestone slurry under aeration oxidation stirring conditions, performing aeration oxidation stirring reaction, and stopping the acid addition when the pH of the reaction solution is controlled to be 3.3, the limestone slurry having an effective calcium carbonate content of ≥95% and a mesh number of ≥325 meshes, is prepared into a slurry of corresponding density, and enters the desulfurization system for pneumatic emulsification to become a gypsum slurry liquid; the limestone slurry is a gypsum slurry liquid after desulfurization treatment, such as controlling the calcium carbonate content in the gypsum slurry liquid to be 45-80wt%; and then placing the gypsum slurry liquid in an aeration oxidation tank for acidification and oxidation treatment, controlling the acidification and oxidation treatment time to be 30min, to obtain a calcium sulfate slurry liquid; 2) Manganese salt catalytic oxidation, When the pH of the calcium sulfate slurry in step 1) rises to 3.8, a manganese salt is added to the calcium sulfate slurry to carry out a manganese salt catalytic oxidation reaction, wherein the manganese salt is potassium permanganate or sodium permanganate; the amount of manganese salt added is controlled so that the manganese content in the desulfurized gypsum slurry reaches 0.021 mol / L, and then the addition is stopped, and then the aeration and stirring reaction is continued for 3 hours to obtain a manganese salt oxidized gypsum slurry, and the manganese salt oxidized gypsum slurry is filtered to obtain a manganese salt oxidized gypsum slurry residue, and the manganese salt oxidized gypsum slurry is filtered to obtain a manganese salt oxidized gypsum slurry residue, and the water content in the manganese salt oxidized gypsum slurry residue is controlled to be 28-35Wt%, and the calcium sulfite content is controlled to be 1.6-4.1Wt; After the calcium sulfite and water content in the manganese salt oxidized gypsum slurry residue are tested and found to be qualified, the manganese salt oxidized gypsum slurry residue is made into a mixed liquid and then the oxidation reaction is continued for 6 hours to obtain a desulfurized gypsum slurry, which is filtered to obtain a desulfurized gypsum slurry residue. The water content in the desulfurized gypsum slurry residue is controlled to be 18-20wt%, and the calcium sulfite content is 0.65wt%. After the test is qualified, the sulfur gypsum slurry residue is filtered and dried to obtain a flue gas desulfurization gypsum product.

[0031] Embodiment 4, The raw materials of each component in this embodiment are all commercially available. The raw materials of each component in this embodiment are all commercially available.

[0032] The present invention discloses a method for preparing flue gas desulfurization gypsum by catalytic oxidation, which uses limestone raw material and limestone slurry with corresponding density as raw material. The so-called limestone slurry with corresponding density generally refers to the limestone slurry used as a desulfurizer to absorb and treat sulfur-containing flue gas generated in the pyrometallurgical process, so that the tail gas can reach the qualified standard for discharge; It includes the following method steps: 1) Acidification and oxidation treatment, placing the limestone slurry in an aeration and oxidation tank, gradually adding sulfuric acid solution to the limestone slurry under aeration and oxidation stirring conditions, performing aeration and oxidation stirring reaction, and stopping the addition of acid when the pH of the reaction solution is controlled to be 3.6, the limestone slurry having an effective calcium carbonate content of ≥95% and a mesh number of ≥325 is prepared into a slurry of corresponding density, and enters the desulfurization system for pneumatic emulsification to become a gypsum slurry liquid; the limestone slurry is a gypsum slurry liquid after desulfurization treatment, such as controlling the calcium carbonate content in the gypsum slurry liquid to be 45-80wt%; and then placing the gypsum slurry liquid in an aeration and oxidation tank for acidification and oxidation treatment, controlling the acidification and oxidation treatment time to be 20min, to obtain a calcium sulfate slurry liquid; 2) Manganese salt catalytic oxidation, When the pH of the calcium sulfate slurry in step 1) rises to 4.0, a manganese salt is added to the calcium sulfate slurry to carry out a manganese salt catalytic oxidation reaction, wherein the manganese salt is potassium permanganate or sodium permanganate; the amount of manganese salt added is controlled so that the manganese content in the desulfurized gypsum slurry reaches 0.018 mol / L, and then the addition is stopped, and then the aeration and stirring reaction is continued for 3 hours to obtain a manganese salt oxidized gypsum slurry, and the manganese salt oxidized gypsum slurry is filtered to obtain a manganese salt oxidized gypsum slurry residue, and the manganese salt oxidized gypsum slurry is filtered to obtain a manganese salt oxidized gypsum slurry residue, and the water content in the manganese salt oxidized gypsum slurry residue is controlled to be 28-35Wt %, and the calcium sulfite content is controlled to be 1.6-4.1Wt ; After the calcium sulfite and water content in the manganese salt oxidized gypsum slurry residue are tested and found to be qualified, the manganese salt oxidized gypsum slurry residue is made into a mixed liquid and then the oxidation reaction is continued for 6 hours to obtain a desulfurized gypsum slurry, which is filtered to obtain a desulfurized gypsum slurry residue. The water content in the desulfurized gypsum slurry residue is controlled to be 18-20wt%, and the calcium sulfite content is 0.62wt%. After the test is qualified, the sulfur gypsum slurry residue is filtered and dried to obtain a flue gas desulfurization gypsum product.

[0033] Comparative Example Due to the differences of each desulfurization system, the comparative example is a scheme of the process of the present invention, in which the desulfurization system adopts the process of the present invention and the original process that does not adopt acid oxidation followed by manganese salt oxidation. The process parameters are the same as those of the embodiment of the present invention. That is, the raw materials are basically the same. The prepared desulfurized gypsum board or desulfurized gypsum product has its test data shown in the following table.

[0034] The desulfurized gypsum prepared by the above method of the present invention has been tested by relevant departments, and the main technical parameters are as follows: Testing basis, according to GB∕T 37785-2019 Flue gas desulfurization gypsum testing method analysis, Table 1, test data:

[0035] Note: The test data in Table 1 above are obtained by randomly sampling the prepared flue gas desulfurization gypsum products as samples, wherein the sulfur content is 22.3% for the comparative example, and 18.3, 17.4, 17.6, and 16.9 for the present examples 1-4, respectively. From the data in Table 1 above, it can be seen that the content of calcium sulfite in the desulfurized gypsum prepared by the method of the present invention is greatly reduced from 76.3% to between 0.26 and 1.1. The content of calcium sulfate is greatly increased from 10.9% to 87.6-90.3%. This shows that the method of the present invention is aimed at the problem of high calcium sulfite content in gypsum. In the process of limestone desulfurization, substances that inhibit and hinder oxidation are easily mixed in the slurry, such as thiosulfate inhibiting oxidation, smoke dust encapsulating and isolating oxidation, etc. The method of the present invention can effectively eliminate the encapsulation phenomenon, accelerate the efficiency of calcium sulfite oxidation to generate calcium sulfate, and the prepared desulfurized gypsum product meets the quality standard requirements. The sulphur gypsum slurry residue is filtered and dried, and part of the calcium sulfite is lost in the process. The content of calcium sulfite in the flue gas desulfurization gypsum product obtained by filtering, drying and drying the sulphur gypsum slurry residue is also greatly reduced.

Claims

1. A method for preparing flue gas desulfurization gypsum by catalytic oxidation, which uses limestone raw material and limestone slurry of corresponding density as raw material, characterized in that: The method comprises the following steps: 1) Acidification and oxidation treatment: place the limestone slurry in an aeration oxidation tank, gradually add sulfuric acid solution to the limestone slurry under aeration oxidation stirring conditions, perform aeration oxidation stirring reaction, and stop adding acid when the pH of the reaction solution is controlled to be 3.2-3.7 to obtain calcium sulfate slurry. 2) Manganese salt catalytic oxidation, Add manganese salt to the calcium sulfate slurry liquid in step 1) for catalytic oxidation reaction for 2.5-4.2 hours to obtain manganese salt oxidized gypsum slurry. The manganese salt oxidized gypsum slurry is filtered to obtain manganese salt oxidized gypsum slurry slag. After the calcium sulfite and water in the manganese salt oxidized gypsum slurry slag are tested to be qualified, the manganese salt oxidized gypsum slurry slag is made into a mixed liquid and then continued to oxidize for 5-7 hours to obtain desulfurized gypsum slurry. The desulfurized gypsum slurry slag is filtered to obtain the desulfurized gypsum slurry slag. After the test is qualified, the sulfur gypsum slurry slag is filtered and dried to obtain the flue gas desulfurization gypsum product.

2. The method for preparing flue gas desulfurization gypsum by catalytic oxidation according to claim 1, characterized in that: Step 1) Limestone slurry: Limestone raw materials with effective calcium carbonate content ≥ 95% and mesh size ≥ 325 are prepared into slurry of corresponding density and enter the desulfurization system for pneumatic emulsification into gypsum slurry liquid.

3. A method for preparing flue gas desulfurization gypsum by catalytic oxidation according to claim 1 or 2, characterized in that: Step 1) The limestone slurry is desulfurized to form a gypsum slurry liquid, which is then placed in an aeration oxidation tank for acidification and oxidation treatment, with the acidification and oxidation treatment time being controlled to be 15-35 minutes.

4. The method for preparing flue gas desulfurization gypsum by catalytic oxidation according to claim 1, characterized in that: Step 2) The manganese salt is potassium permanganate or sodium permanganate.

5. A method for preparing flue gas desulfurization gypsum by catalytic oxidation according to claim 1 or 4, characterized in that: The amount of manganese salt added is controlled so that when the manganese content in the desulfurized gypsum slurry reaches 0.01-0.02 mol / L, the addition is stopped, and then the aeration and stirring reaction is continued for 3 hours.

6. The method for preparing flue gas desulfurization gypsum by catalytic oxidation according to claim 1, characterized in that: Step 2) filtering the manganese salt oxidized gypsum slurry to obtain manganese salt oxidized gypsum slurry residue, and controlling the water content of the manganese salt oxidized gypsum slurry residue to be 28-35 wt %, and the calcium sulfite content to be 1.6-4.1 wt %.

7. The method for preparing flue gas desulfurization gypsum by catalytic oxidation according to claim 1, characterized in that: Step 2) Control the moisture content in the desulfurized gypsum slurry residue to 18-20wt%, and the calcium sulfite content to 0.5-1.5wt%.

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