Preparation method of normal low temperature flue gas desulfurizer

Abstract

The present invention relates to a method for preparing a normal-low-temperature flue gas desulfurizer, comprising the following steps: (a) mixing a soluble carbonate and a soluble manganese salt in a molar ratio of carbonate to manganese ion of 1:0.7 to 1:0.9; (b) subjecting the mixture obtained in step (a) to a coprecipitation method at room temperature with a pH adjusted to 7 to 8 using aqueous ammonia, followed by stirring and reacting; (c) heating the slurry obtained in step (b) to 80°C in a hydrothermal kettle, stirring for 12 hours, and then filtering; (d) curing the solid obtained in step (c) in the vapor of an ethanol aqueous solution for 3 to 48 hours, drying, and then calcining to obtain activated manganese oxide; (e) respectively adding lime, red mud, gypsum, and sodium thiosulfate to the activated manganese oxide obtained in step (d), kneading the mixture uniformly, and then extruding the mixture into strips; and (f) irradiating the product obtained in (e) under ultraviolet light for 3 to 48 hours, followed by drying. The desulfurizer prepared by the present invention has high sulfur capacity and strength.

Description

Technical Field

[0001] The invention relates to a method for preparing a normal-low-temperature flue gas desulfurizer with high sulfur capacity and high strength, and belongs to the field of desulfurized gas purification. Background Art

[0002] Sulfur dioxide is a colorless gas with a strong, pungent odor. It persists in the air for about a week before gradually oxidizing to sulfur trioxide. In the presence of water vapor, sulfuric acid mist forms, with sunlight, dust, and metal oxides acting as catalysts. Sulfuric acid mist is more harmful than sulfur dioxide. Sulfur dioxide pollution also manifests itself in acid rain, causing tens of billions of yuan in economic losses to my country annually. Flue gas desulfurization (FGD) is currently the most widely used, most researched, and most rapidly developing method for removing sulfur dioxide. Most sulfur in flue gas exists in the form of SO2. FGD methods can be broadly divided into two categories: wet, which uses liquid absorbents such as water or alkaline solutions to scrub the flue gas to remove SO2; and dry, which uses powdered or granular absorbents or catalysts to remove SO2. Wet FGD involves adding an alkaline substance to the flue in the presence of moisture, causing it to neutralize the SO2 and remove it. Wet FGD offers high efficiency and relatively low cost. However, when the flue gas comes into contact with equipment and components, it will cause serious corrosion of the equipment and components, and a matching sewage treatment system is required. Dry flue gas desulfurization uses solid powdered or granular absorbents, adsorbents or catalysts to remove sulfur dioxide. The characteristics of dry desulfurization are: it is carried out in a completely dry state without the intervention of a liquid phase, and the desulfurization product is dry. Dry flue gas desulfurization requires less investment than wet desulfurization processes and occupies less space, making it more suitable for renovation projects of old power plants; the waste agent after desulfurization of dry flue gas desulfurization is dry and can be used as raw material in gypsum to continue to make new flue gas desulfurizers, or it can be stacked and reused in road construction, building materials, etc.; there is no wastewater discharge, which reduces equipment corrosion and the trouble of wastewater treatment.

[0003] Currently, the dry flue gas desulfurizers on the market are divided into medium-high temperature and medium-low temperature. The medium-high temperature is usually 200~400℃, and the medium-low temperature is 40~200℃. There are few reports on room temperature flue gas desulfurizers of 0~40℃. Therefore, the present invention has developed a flue gas desulfurizer covering room temperature and low temperature, with an operating temperature range of 0~200℃, filling a blank area in the market. Summary of the Invention

[0004] The present invention mainly solves the problem of serious corrosion of equipment and components caused by current wet flue gas desulfurization, as well as the trouble of handling large amounts of wastewater. The present invention provides a method for preparing a normal low temperature flue gas desulfurizer for dry flue gas desulfurization with a simple manufacturing process.

[0005] In order to solve the above technical problems, the present invention relates to a method for preparing a normal low temperature flue gas desulfurizer, the preparation method comprising the following steps:

[0006] (a) mixing a soluble carbonate and a soluble manganese salt in a molar ratio of carbonate to manganese ion of 1:0.7 to 1:0.9;

[0007] (b) adding water to the mixture obtained in step (a) and reacting the mixture by co-precipitation at room temperature with ammonia water at a pH of 7 to 8, where the metal oxide crystals such as aluminum oxide and iron oxide in the red mud have better desulfurization activity;

[0008] (c) the slurry obtained in step (b) was heated to 80°C in a hydrothermal kettle, stirred for 12 hours, and then filtered;

[0009] (d) curing the solid obtained in step (c) in the vapor of an ethanol aqueous solution at a certain temperature for 3 to 24 hours, drying it, and then calcining it to obtain activated manganese oxide;

[0010] (e) adding lime, red mud, gypsum and sodium thiosulfate in certain proportions to the activated manganese oxide obtained in step (d), kneading the mixture uniformly, and then extruding the mixture into strips;

[0011] (f) Irradiate the product obtained in (e) under ultraviolet light at 40-70°C for 3-24 hours, and then dry it at 120°C.

[0012] The present invention has the following advantages:

[0013] 1. The activated manganese oxide in the raw material of the flue gas desulfurizer prepared by the present invention is subjected to steam curing treatment with an ethanol aqueous solution. The oxygen-manganese ratio of the activated manganese oxide is increased from 1.80 before curing to 1.89, the specific surface area (BET) is increased from 60.24 to 133.25, and the oxygen depletion temperature is significantly reduced, which greatly improves the oxidation activity of the activated manganese oxide. It can efficiently oxidize sulfur dioxide into sulfur trioxide, and finally react with calcium hydroxide to produce calcium sulfate.

[0014] 2. The waste agent of the flue gas desulfurizer prepared by the present invention is mainly composed of calcium sulfate, i.e. gypsum, which can be used as a raw material for the preparation and production of new flue gas desulfurizers, and can also be used as raw materials for road construction, building materials, bricks, etc., which can fully recycle resources.

[0015] 3. The flue gas desulfurizer prepared by the present invention is mixed and extruded and then cured under ultraviolet light at a certain temperature, which can significantly increase the strength of the flue gas desulfurizer, with an average strength exceeding 180N / cm, greatly reducing the catalyst pulverization phenomenon during use and reducing bed resistance. The strength of the product not cured by ultraviolet light is less than 120N / cm.

[0016] 4. The sodium thiosulfate added to the flue gas desulfurizer prepared by the present invention can act as a chemical stimulant to stimulate the activity of red mud, promote the hydration reaction, and greatly increase the specific surface area of ​​the catalyst from 57.23m2 before adding the stimulant. 2 / g increased to 102.42m / g after adding activator 2 / g, which greatly improves the sulfur capacity of the flue gas desulfurizer from 21.7% to 28.5%.

[0017] 5. By adding water to the mixture and then adjusting the pH with ammonia, the solution's original weak acidity becomes weakly alkaline. This allows red mud, primarily composed of aluminum oxide and iron oxide, to exhibit high catalytic desulfurization activity, making it a key active component in the preparation of ambient-temperature flue gas desulfurizers, thus enabling the recycling of red mud, an industrial solid waste. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to specific embodiments.

[0019] Example 1

[0020] 50g of sodium carbonate and 55.8g of manganese sulfate monohydrate were uniformly mixed in a carbonate to manganese ion molar ratio of 1:0.7. 1L of water was added and the pH of the solution was adjusted to 8.0 with aqueous ammonia. The mixture was stirred for 50 minutes to produce a slurry containing an activated manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. After filtering the precipitate, the precipitate was steam-cured at 40°C with an ethanol-water solution (volume ratio: 1:0.5) for 6 hours, then dried and calcined at 400°C for later use. 30g of lime, 5g of red mud, 50g of gypsum, 10g of activated manganese oxide, and 5g of sodium thiosulfate were mixed and kneaded to produce a precipitate. After filtering the precipitate, the precipitate was cured under ultraviolet light at 40°C for 6 hours, and then dried at 120°C for 2 hours. This method for preparing the ambient-low-temperature flue gas desulfurizer of the present invention was completed.

[0021] In this desulfurizer, the strength is 181.2N / cm, the specific surface area is 101.36m 2 / g, sulfur content 28.5%. Example 2

[0022] 50g of sodium carbonate and 55.8g of manganese sulfate monohydrate were uniformly mixed in a carbonate to manganese ion molar ratio of 1:0.7. 1L of water was added and the pH of the solution was adjusted to 7.0 with aqueous ammonia. The mixture was stirred for 50 minutes to produce a slurry containing an activated manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. After filtering the precipitate, the precipitate was steam-cured at 40°C with an ethanol-water solution (volume ratio: 1:0.5) for 6 hours, then dried and calcined at 400°C for later use. 30g of lime, 5g of red mud, 50g of gypsum, 10g of activated manganese oxide, and 5g of sodium thiosulfate were mixed and kneaded to produce a precipitate. After filtering the precipitate, the precipitate was cured under ultraviolet light at 40°C for 6 hours, and then dried at 120°C for 2 hours. This method for preparing the ambient-low-temperature flue gas desulfurizer of the present invention was completed.

[0023] In this desulfurizer, the strength is 182.1N / cm, the specific surface area is 101.46m 2 / g, sulfur content 28.7%.

[0024] Example 3

[0025] 50g of sodium carbonate and 55.8g of manganese sulfate monohydrate were uniformly mixed at a carbonate to manganese ion molar ratio of 1:0.7. The pH value was not adjusted, and the pH was 6.0 at this time. The mixture was stirred for 50 minutes to prepare a slurry containing an activated manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. After filtering the precipitate, the precipitate was steam-cured at 40°C with an ethanol-water solution at a volume ratio of 1:0.5 for 6 hours, then dried and calcined at 400°C for later use. 30g of lime, 5g of red mud, 50g of gypsum, 10g of activated manganese oxide, and 5g of sodium thiosulfate were mixed and kneaded to form a precipitate. After filtering the precipitate, the precipitate was cured under ultraviolet light at 40°C for 6 hours, and then dried at 120°C for 2 hours. This method for preparing the ambient low-temperature flue gas desulfurizer of the present invention was completed.

[0026] In this desulfurizer, the strength is 181.8N / cm, the specific surface area is 100.76m 2 / g, sulfur content 20.4%. Example 4

[0027] 50g of sodium carbonate and 71.7g of manganese sulfate monohydrate were uniformly mixed in a carbonate to manganese ion molar ratio of 1:0.9. 1L of water was added and the pH of the solution was adjusted to 7.8 with aqueous ammonia. The mixture was stirred for 50 minutes to produce a slurry containing an active manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. The slurry was then steam-cured at 50°C with a 1:1 ethanol-water solution by volume ratio for 6 hours, then dried and calcined at 500°C for later use. 35g of lime, 5g of red mud, 50g of gypsum, 5g of active manganese oxide, and 5g of sodium thiosulfate were mixed and extruded, cured under ultraviolet light at 50°C for 6 hours, and then dried at 120°C for 2 hours to produce the normal low-temperature flue gas desulfurizer of the present invention.

[0028] In this desulfurizer, the strength is 188.2N / cm, the specific surface area is 102.16m 2 / g, sulfur content 28.3%.

[0029] Example 5

[0030] 50g of sodium carbonate and 71.7g of manganese sulfate monohydrate were uniformly mixed in a carbonate to manganese ion molar ratio of 1:0.9. 1L of water was added and the pH of the solution was adjusted to 7.8 with aqueous ammonia. The mixture was stirred for 50 minutes to produce a slurry containing an activated manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours, then dried and calcined at 500°C for later use. 35g of lime, 5g of red mud, 50g of gypsum, 5g of activated manganese oxide, and 5g of sodium thiosulfate were mixed and extruded, cured under ultraviolet light at 50°C for 6 hours, and then dried at 120°C for 2 hours to produce the normal low-temperature flue gas desulfurizer of the present invention.

[0031] In this desulfurizer, the strength is 183.4N / cm, the specific surface area is 42.56m 2 / g, sulfur content 21.3%. Example 6

[0032] 55.2g of ammonium carbonate and 41.6g of manganese chloride were uniformly mixed in a carbonate to manganese ion molar ratio of 1:0.7. 1L of water was added and the pH of the solution was adjusted to 7.7 with aqueous ammonia. The mixture was stirred for 80 minutes to prepare a slurry containing an active manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. The mixture was then steam-cured at 60°C with a 1:1 ethanol-water solution by volume ratio for 12 hours, then dried and calcined at 500°C for further use. 35g of lime, 19g of red mud, 40g of gypsum, 1g of active manganese oxide, and 5g of sodium thiosulfate were mixed and extruded. The mixture was cured under ultraviolet light at 60°C for 12 hours and then dried at 120°C for 2 hours to prepare the normal low-temperature flue gas desulfurizer of the present invention.

[0033] In this desulfurizer, the strength is 193.5N / cm, the specific surface area is 102.85m2 / g, sulfur content 28.7%.

[0034] Example 7

[0035] 55.2g of ammonium carbonate and 41.6g of manganese chloride were uniformly mixed in a carbonate to manganese ion molar ratio of 1:0.7. 1L of water was added and the pH of the solution was adjusted to 7.7 with aqueous ammonia. The mixture was stirred for 80 minutes to produce a slurry containing an activated manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. The slurry was then steam-cured at 60°C with a 1:1 ethanol-water ratio by volume for 12 hours, then dried and calcined at 500°C for later use. The method for preparing the ambient-low-temperature flue gas desulfurizer of the present invention was also described. 35g of lime, 19g of red mud, 40g of gypsum, and 1g of activated manganese oxide were cured at 60°C under ultraviolet light for 12 hours, and then dried at 120°C for 2 hours.

[0036] In this desulfurizer, the strength is 192.4N / cm, the specific surface area is 45.40m 2 / g, sulfur content 20.6%. Example 8

[0037] 55.2g of ammonium carbonate and 53.5g of manganese chloride were uniformly mixed, with a carbonate to manganese ion molar ratio of 1:0.9. 1L of water was added and the pH of the solution was adjusted to 7.5 with aqueous ammonia. The mixture was stirred for 80 minutes to prepare a slurry containing an active manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. After filtering the precipitate, the precipitate was steam-cured at 70°C with a 1:3 volume ratio of ethanol and water for 24 hours, then dried and calcined at 450°C for later use. 20g of lime, 20g of red mud, 50g of gypsum, 1g of active manganese oxide, and 9g of sodium thiosulfate were mixed and kneaded to form a precipitate. After filtering the precipitate, the precipitate was cured under ultraviolet light at 70°C for 24 hours, and then dried at 120°C for 2 hours. This method for preparing the ambient low-temperature flue gas desulfurizer of the present invention was completed.

[0038] In this desulfurizer, the strength is 182.2N / cm, the specific surface area is 101.45m 2 / g, sulfur content 28.1%.

[0039] Example 9

[0040] 55.2g of ammonium carbonate and 53.5g of manganese chloride were uniformly mixed, with a carbonate to manganese ion molar ratio of 1:0.9. 1L of water was added and the pH of the solution was adjusted to 7.5 with aqueous ammonia. The mixture was stirred for 80 minutes to prepare a slurry containing an active manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. After filtering the precipitate, the precipitate was steam-cured at 70°C with a 1:3 volume ratio of ethanol and water for 24 hours, then dried and calcined at 450°C for later use. 20g of lime, 20g of red mud, 50g of gypsum, 1g of active manganese oxide, and 9g of sodium thiosulfate were mixed and kneaded to form a precipitate. After filtering the precipitate, the precipitate was dried at 120°C for 2 hours to prepare the normal low temperature flue gas desulfurizer of the present invention.

[0041] In this desulfurizer, the strength is 122.6N / cm, the specific surface area is 101.25m 2 / g, sulfur content 28.2%.

[0042] Table 1 Physical indicators and sulfur capacity of the preparation method of low-temperature flue gas desulfurizers with comparison of control variables

[0043]

[0044] Table 1 summarizes the physical indicators and sulfur capacity data of the preparation methods of the ambient low temperature flue gas desulfurizers compared by controlling variables in Examples 1 to 9. The following conclusions can be drawn from the comparative analysis:

[0045] ① It can be seen from Example 1, Example 2 and Example 3 in Table 1 that when the pH value of the solution is adjusted to between 7 and 8, the sulfur capacity is significantly improved from 20% to more than 28% due to the improvement of the crystal form in the red mud.

[0046] ② From Example 4 and Example 5 in Table 1, it can be seen that under the steam curing with ethanol aqueous solution, the specific surface area of ​​the product is significantly improved from 42.56m 2 / g increased to 102.16m 2 / g, which resulted in the sulfur capacity increasing from 21.3% to 28.3%.

[0047] ③ It can be seen from Examples 6 and 7 in Table 1 that when sodium thiosulfate is used as an activator, the specific surface area of ​​the product is also significantly improved, from 45.40 m 2 / g increased to 102.85m 2 / g, which resulted in the sulfur capacity increasing from 20.6% to 28.7%.

[0048] ④ It can be seen from Example 8 and Example 9 in Table 1 that under the condition of ultraviolet light curing, the product strength is significantly improved from 122.6 N / cm to 182.2 N / cm.

[0049] Example 10

[0050] 37.3g of ammonium bicarbonate and 52.2g of potassium permanganate were uniformly mixed in a carbonate to manganese ion molar ratio of 1:0.7. 1L of water was added and the pH of the solution was adjusted to 7.0 with aqueous ammonia. The mixture was stirred for 50 minutes to produce a slurry containing an activated manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. After filtering the precipitate, the precipitate was steam-cured at 70°C with a 1:5 volume ratio of ethanol and water for 24 hours, then dried and calcined at 550°C for later use. 30g of lime, 5g of red mud, 50g of gypsum, 5g of activated manganese oxide, and 10g of sodium thiosulfate were mixed and kneaded to produce a precipitate. After filtering the precipitate, the precipitate was cured under ultraviolet light at 70°C for 3 hours and then dried at 120°C for 2 hours to produce the normal low-temperature flue gas desulfurizer of the present invention.

[0051] In this desulfurizer, the strength is 189.2N / cm, the specific surface area is 101.63m 2 / g, sulfur content 29.9%. Example 11

[0052] 37.3g of ammonium bicarbonate and 67.1g of potassium permanganate were uniformly mixed in a carbonate to manganese ion molar ratio of 1:0.9. 1L of water was added and the pH of the solution was adjusted to 7.5 with aqueous ammonia. The mixture was stirred for 100 minutes to produce a slurry containing an activated manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. After filtering the precipitate, the precipitate was steam-cured at 70°C with a 1:2 volume ratio of ethanol and water for 3 hours, then dried and calcined at 550°C for later use. 80g of lime, 9g of red mud, 5g of gypsum, 5g of activated manganese oxide, and 1g of sodium thiosulfate were mixed and kneaded to produce a precipitate. After filtering the precipitate, the precipitate was cured under ultraviolet light at 70°C for 24 hours and then dried at 120°C for 2 hours to produce the normal low-temperature flue gas desulfurizer of the present invention.

[0053] In this desulfurizer, the strength is 186.2N / cm, the specific surface area is 100.21m 2 / g, sulfur content 30.2%.

[0054] Example 12

[0055] 65.1g of potassium carbonate and 55.8g of manganese sulfate monohydrate were uniformly mixed in a carbonate to manganese ion molar ratio of 1:0.7. 1L of water was added and the pH of the solution was adjusted to 7.2 with aqueous ammonia. The mixture was stirred for 100 minutes to produce a slurry containing an activated manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. After filtering the precipitate, the precipitate was steam-cured at 70°C with a 1:5 volume ratio of ethanol and water for 24 hours, then dried and calcined at 550°C for later use. 60g of lime, 20g of red mud, 9g of gypsum, 10g of activated manganese oxide, and 1g of sodium thiosulfate were mixed and kneaded to produce a precipitate. After filtering the precipitate, the precipitate was cured under ultraviolet light at 70°C for 3 hours and then dried at 120°C for 2 hours to produce the normal low-temperature flue gas desulfurizer of the present invention.

[0056] In this desulfurizer, the strength is 198.5N / cm, the specific surface area is 103.36m 2 / g, sulfur content 29.8%. Example 13

[0057] 65.1g of potassium carbonate and 71.7g of manganese sulfate monohydrate were uniformly mixed in a carbonate to manganese ion molar ratio of 1:0.9. 1L of water was added and the pH of the solution was adjusted to 8.0 with aqueous ammonia. The mixture was stirred for 120 minutes to produce a slurry containing an activated manganese oxide precipitate. The resulting slurry was heated to 80°C in a hydrothermal kettle and stirred for 12 hours. The precipitate was filtered and then steam-cured at 80°C with a 1:5 volume ratio of ethanol and water for 12 hours. The precipitate was then dried and calcined at 550°C for later use. 20g of lime, 10g of red mud, 50g of gypsum, 10g of activated manganese oxide, and 10g of sodium thiosulfate were mixed and kneaded to produce a precipitate. The precipitate was filtered and cured under ultraviolet light at 70°C for 24 hours. The precipitate was then dried at 120°C for 2 hours to produce the normal low-temperature flue gas desulfurizer of the present invention.

[0058] In this desulfurizer, the strength is 200.5N / cm, the specific surface area is 102.39m 2 / g, sulfur content 31.2%.

[0059] In Examples 1 to 13 above, the sodium carbonate used was an analytically pure reagent with a purity of 99.8%, the ammonium carbonate was an analytically pure reagent with a purity of 99%, the ammonium bicarbonate was an analytically pure reagent with a purity of 99%, the potassium carbonate was an analytically pure reagent with a purity of 99%, the manganese sulfate monohydrate was an analytically pure reagent with a MnSO4·H2O content of 99%, the manganese chloride was an analytically pure reagent with a purity of 99%, the potassium permanganate was an analytically pure reagent with a purity of 99%, the ammonia solution was a 28% ammonia solution reagent, the lime was industrial lime with a calcium hydroxide purity of greater than or equal to 92%, the red mud was a by-product red mud produced by the Bayer process for producing alumina, the gypsum was a calcium sulfate reagent or waste reagent with a purity of 90%, and the sodium thiosulfate was an industrial raw material with a purity of 99%. Extrusion was carried out on a twin-screw extruder, ethanol vapor curing was carried out in a temperature-controlled water bath, drying was carried out in an electric blast drying oven, roasting was carried out in an electric roasting furnace, and UV irradiation curing was carried out in a yellowing resistance test chamber.

[0060] Although the present invention has described the above multiple implementation cases in detail, those skilled in the art should understand that any changes in form and details made thereon fall within the scope of protection of the present invention.

Claims

1. A method for preparing a normal low temperature flue gas desulfurizer, characterized in that The steps include: (a) mixing a soluble carbonate and a soluble manganese salt in a molar ratio of carbonate to manganese ion of 1:0.7 to 1:0.9; (b) adding water to the mixture obtained in step (a) and reacting the mixture by coprecipitation at room temperature with ammonia water adjusting the pH to 7-8; (c) the slurry obtained in step (b) was heated to 80°C in a hydrothermal kettle, stirred for 12 hours, and then filtered; (d) curing the solid obtained in step (c) in the steam of an ethanol aqueous solution at a certain temperature and volume ratio for 3 to 48 hours, drying the solid, and then calcining the solid to obtain activated manganese oxide; (e) adding lime, red mud, gypsum and sodium thiosulfate in certain proportions to the activated manganese oxide obtained in step (d), kneading the mixture uniformly, and then extruding the mixture into strips; The lime is industrial lime with a calcium hydroxide purity greater than or equal to 92%; (f) Irradiating the product obtained in (e) under ultraviolet light at a certain temperature for 3 to 48 hours, and then drying.

2. The method for preparing a normal low temperature flue gas desulfurizer according to claim 1, characterized in that: The soluble carbonate described in step (a) is one of sodium carbonate, ammonium carbonate, ammonium bicarbonate, and potassium carbonate, and the soluble manganese salt is one of manganese sulfate, manganese chloride, and potassium permanganate.

3. The method for preparing a normal-low-temperature flue gas desulfurizer according to claim 1, characterized in that: The coprecipitation method in step (b) is completed by mechanical stirring, and the stirring time is 50 to 120 minutes.

4. The method for preparing a normal-low-temperature flue gas desulfurizer according to claim 1, characterized in that: The volume ratio of ethanol to water in the ethanol aqueous solution in step (d) is 1:0.5 to 1:

5.

5. The method for preparing a normal-low-temperature flue gas desulfurizer according to claim 1, characterized in that: The ethanol aqueous solution vapor temperature in step (d) is 50-80°C.

6. The method for preparing a normal-low-temperature flue gas desulfurizer according to claim 1, characterized in that: The calcination temperature in step (d) is 400° C. to 550° C., and the calcination time is 3 hours.

7. The method for preparing a normal-low-temperature flue gas desulfurizer according to claim 1, characterized in that: In step (e), the mass percentages of lime, red mud, activated manganese oxide, gypsum and sodium thiosulfate are respectively 30-80% of lime, 5%-20% of red mud, 5%-50% of gypsum, 1%-10% of manganese oxide and 1%-10% of sodium thiosulfate.

8. The method for preparing a normal-low-temperature flue gas desulfurizer according to claim 1, characterized in that: The ultraviolet light temperature in step (f) is 40-70°C.

9. The method for preparing a normal-low-temperature flue gas desulfurizer according to claim 1, characterized in that: The ultraviolet light irradiation time in step (f) is 3 to 24 hours.

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