Flue gas desulfurization process

Abstract

Water is added into manganese dioxide powder to prepare manganese slurry, ammonia water or ammonium bicarbonate is used for adjusting the pH value, sulfur-containing flue gas enters a desulfurizing tower to react with the manganese dioxide mineral powder and the manganese slurry to remove sulfur dioxide, manganese sulfate slurry is generated and can be used for obtaining high-purity manganese sulfate, and ammonium sulfate generated through the reaction can be recycled. The process is mild in production condition, SO2 in the flue gas is converted into available manganese sulfate, resource recycling of sulfur dioxide in the flue gas can be achieved, economic benefits are generated, meanwhile, environmental pollution is reduced, and a technical route is provided for sulfur-containing flue gas treatment and resource utilization. The produced manganese sulfate can be used for preparing high-quality battery-grade manganese sulfate, a raw material is provided for the new energy battery industry, and the market competitiveness of enterprises is improved. The process method provided by the invention accords with the concept of combining ecological environment protection and economic development, and has a relatively high application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wet flue gas desulfurization, in particular to a flue gas desulfurization process, a pH value adjusting method and related matching processes. BACKGROUND

[0002] Sulfur dioxide (SO2) gas is one of the world's recognized major atmospheric pollutants, which can cause diseases of human respiratory system and cardiovascular and cerebrovascular system, and cause major environmental problems such as water and soil acidification, haze, and seriously threaten human health and ecological environment safety. The main sources of SO2 emission are the use of fossil fuels, such as coal-fired power plants, metal smelting plants, etc. With the continuous development of economy and society, fossil fuels will still be used in large quantities as the main source of world energy. The energy structure of fossil fuels in China has the characteristics of lack of oil, less gas, and rich coal, and this situation will not change in the foreseeable future. Coal will be a long-term pillar of energy supply in China. The average sulfur content of the proven coal resources in China is 1.13%, which is at a high level. Therefore, in order to maintain the stable economic growth of China and at the same time protect the ecological environment benefits, the problem of SO2 emission must be handled well.

[0003] At present, among various desulfurization technologies for sulfur-containing flue gas, wet desulfurization technology has strong adaptability and is a research hotspot for new desulfurization processes. Relevant documents include “Wu Guanglong. Experimental study on calcium sulfite oxidation in wet desulfurization of calcium carbide slag-gypsum [J / OL]. Chemical Industry and Environmental Protection, 1-7 [2025-06-18]”, “Wang Cun, Xia Shuntang. Application research on slurry pH and density control technology in calcium desulfurization [J]. East China Paper, 2024, 54(08): 60-62.”, etc. Among them, the limestone-gypsum desulfurization method is the most commonly used method in wet desulfurization technology (such as the patent “A new limestone-gypsum wet flue gas desulfurization additive and its preparation method”, CN202311727766.5) (such as the patent “Limestone-gypsum flue gas desulfurization system and limestone-gypsum flue gas desulfurization method”, CN202111289726.8) (such as the patent “High-molecular adhesion calcium-based flue gas desulfurizer and preparation method thereof”, CN202510213134.X). This method has high desulfurization efficiency and wide application range, but it produces gypsum by-product, has low economic value, is difficult to handle, and can easily cause equipment or pipeline blockage; the double-alkali method improves the blockage problem by using sodium alkali solution, but still generates calcium sulfate (CaSO4) solid waste in the regeneration process of the absorption slurry. This route has low cost but produces a large amount of waste residue, uses sodium hydroxide for treatment of sulfur-containing flue gas at high cost, and produces sodium sulfate with low value and difficulty in handling, which is difficult to operate and has high maintenance cost; the ammonia desulfurization method removes SO2 through the reaction of ammonia (NH3) and SO2 and produces nitrogen fertilizer as a by-product, but due to the high volatility of ammonia water, ammonia escape easily occurs during the desulfurization process, causing air pollution; the technology of converting SO2 into elemental sulfur using a reducing agent has the problem of difficulty in selecting a suitable reducing agent, such as using hydrogen sulfide, which is cheap but toxic, malodorous, and inconvenient to source, and using carbon or carbon monoxide as a reducing agent has the problems of high desulfurization temperature (500-850℃) and high operating cost; the sulfide alkali method uses industrial-grade sodium sulfide as raw material to generate sodium thiosulfate, but has the problem of complex reaction.

[0004] At the same time, with the increasing emphasis on environmental problems, the emission limit of SO2 is becoming increasingly stringent; strict emission limits pose a severe challenge to existing SO2 removal technologies. Under the premise of not increasing the size of existing desulfurization equipment, the removal efficiency can only be improved by increasing the circulation amount of desulfurizing agent, which increases the operating cost.

[0005] In summary, the current commonly used desulfurization technologies generally have the problems of waste of sulfur resources and secondary environmental pollution. Therefore, developing green and efficient desulfurization technologies to reduce SO2 emissions and realize the utilization of sulfur resources is the future development direction of SO2 removal technology. SUMMARY

[0006] The application provides a desulfurization process for sulfur-containing flue gas, which has relatively mild production conditions, converts SO2 in the flue gas into available manganese sulfate, can realize resource recycling of sulfur dioxide in the flue gas, reduces environmental pollution while generating economic benefits, and provides a technical route for sulfur-containing flue gas treatment and resource utilization. The generated manganese sulfate can be used for preparing high-quality battery-grade manganese sulfate, providing raw material support for the development of new energy battery industry, promoting technological progress and development, and improving the market competitiveness of enterprises. The process method disclosed by the application conforms to the concept of combining ecological environment protection and economic development, and has strong application value.

[0007] A flue gas desulfurization process, comprising the following steps:

[0008] (1) manganese dioxide powder is prepared into manganese slurry by adding water according to a solid-liquid ratio of 1:(2-4);

[0009] (2) the manganese slurry is passed through 10-25% ammonia water or ammonium bicarbonate to adjust the pH, so that the pH of the manganese slurry is ensured to be between 3.0 and 5.5 during the absorption of the sulfur-containing flue gas;

[0010] (3) the sulfur-containing flue gas enters a desulfurization tower to react with the manganese dioxide mineral powder manganese slurry to remove sulfur dioxide, the system temperature is 50-90 DEG C, manganese sulfate slurry is generated, the sulfur dioxide absorption rate is detected, the tail gas after absorption is exhausted, and the desulfurization manganese slurry is recycled for 2-5 times;

[0011] (4) the generated manganese sulfate slurry is filtered and then enters a manganese sulfate sulfidation acidification impurity removal system to remove impurities, so as to obtain refined manganese sulfate;

[0012] (5) the manganese sulfate slurry containing ammonium sulfate is passed through a manganese sulfate purification impurity removal system, separated by pressure filtration, and the liquid is recycled by a deamination system.

[0013] The desulfurization principle of the process is as follows: the pH of the desulfurization manganese slurry is adjusted by ammonia water or ammonium bicarbonate, the manganese slurry is contacted with the flue gas when the pH is between 3.0 and 5.5, manganese dioxide reacts with sulfur dioxide in the flue gas to generate manganese sulfate.

[0014] Reaction of ammonia water and carbon dioxide: 2NH3·H2O+CO2=(NH4)2CO3

[0015] NH3·H2O+CO2=NH4HCO3

[0016] Neutralization of H + , adjust the pH: (NH4)2CO3+2H + =H2O+2NH4 + +CO2↑

[0017] NH4HCO3+H + =H2O+NH4+ + CO2↑

[0018] The pH value of the desulfurization manganese slurry is mainly adjusted by ammonia water or ammonium bicarbonate, so that the pH value of the manganese slurry in contact with the flue gas in the desulfurization tower is between 3.0 and 5.5 (under this pH condition, the desulfurization efficiency is the highest), and the desulfurization manganese slurry that has passed through the desulfurization tower is recycled to the desulfurization manganese slurry storage tank after adjusting the pH value on the basis of ensuring the desulfurization rate and is used for 2-5 times, so that resource utilization is maximized, the effect of reducing cost and increasing efficiency is achieved, and then it is discharged to a manganese sulfate purification and impurity removal system to prepare high-purity manganese sulfate.

[0019] The CO2 generated in the desulfurization manganese slurry storage tank due to pH adjustment reacts with newly added ammonia water or ammonium carbonate, realizing the recycling of CO2 in the desulfurization manganese slurry storage tank, which not only can play a role in adjusting the pH value, but also can reduce the emission of CO2.

[0020] Absorbing sulfur dioxide: MnO2+ SO2 = MnSO4

[0021] The temperature of the reaction system is 50-90°C, wherein the flue gas has a certain amount of heat, which can promote the temperature rise of the desulfurization manganese slurry. The whole reaction has low requirements for temperature control equipment, the desulfurization raw materials are easy to obtain, and the process temperature is suitable compared with the process using carbon or carbon monoxide as a reducing agent. The pH adjustment process and the desulfurization process in the process are easy to operate.

[0022] The ammonium sulfate generated in the reaction is recycled through the deamination system, so that the recycling of ammonia resources can be realized.

[0023] Preferably, in step (1), the solid-liquid ratio of manganese dioxide powder to water is 1:3.

[0024] Preferably, in step (2), the concentration of ammonia water for adjusting the pH value is 20%.

[0025] Preferably, in step (2), the manganese slurry is adjusted to a pH value by passing ammonia water or ammonium bicarbonate, so that the pH value of the manganese slurry in the process of absorbing sulfur-containing flue gas is between 3.5 and 5.0.

[0026] The concentration of ammonia water used in the process of the present application is 10-25%, and the SO2 removal rate is more than 95.0%; preferably, when the concentration of ammonia water is 20%, the SO2 removal rate can reach 99.6%.

[0027] The subsequent purification and impurity removal process of the crude manganese sulfate of the present application can be seen in the patent applications “A manganese sulfate ammonia sulfidation acidification impurity removal method” CN202411175193.4 and “A manganese sulfate sodium sulfidation impurity removal method” CN202411313702.5 of the present applicant. The sodium content of the manganese sulfate product obtained by the process is less than 40 ug / g, and there is almost no problem of sodium sulfate treatment. The residual manganese (3-4)% of the desulfurization manganese residue of the process of the present application can be used for preparing high-quality battery-grade manganese sulfate.

[0028] Compared with the two mineral acid leaching process for obtaining high-purity manganese sulfate, the washing process for obtaining high-purity manganese sulfate in the application can reduce the washing water consumption per ton of product, and 2 tons of washing water per ton of product can be saved, and at least 2000 tons of washing water can be saved per month under the condition of 1000 tons of output per month.

[0029] The process method using manganese dioxide slurry as a desulfurizer for sulfur-containing flue gas and using ammonia water or ammonium bicarbonate as a manganese slurry pH regulator is currently only used by the company; the process method for preparing high-purity manganese sulfate by treating sulfur-containing flue gas to generate manganese sulfate slurry, and then performing pressure filtration, sulfidation and acidification purification and impurity removal is also currently only used by the company (downstream technology such as patent application "Method for preparing high-end lithium manganate special high-purity trimanganese tetroxide from manganese sulfate", CN202411433603.0); the entire process described in the application can not only realize the recycling of sulfur dioxide resources and the cyclic use of ammonia resources, but also reduce the emission of sulfur-containing flue gas into the environment to cause harm to the environment.

[0030] In addition, in combination with regional resource advantages, the process method described in the application has greater application value and reference value in regions rich in manganese ore reserves (such as Tongren, Guizhou, Hunan, Guangxi, etc.), and can convert manganese ore powder and sulfur dioxide in sulfur-containing flue gas into high-purity manganese functional materials with great economic value through the process method, thereby achieving ecological environment protection and ensuring economic high-quality development.

[0031] Compared with the prior art, the application has the following beneficial effects:

[0032] 1. Easy to operate and low cost: the process is simple, the equipment updating requirement is low, it is easy to operate in actual production, and the production cost is low.

[0033] 2. Resource recycling: ammonia resources can be recycled after desulfurization of ammonium bicarbonate and ammonia water, avoiding resource waste and meeting national resource environmental protection requirements.

[0034] 3. Easy treatment of desulfurization by-products: manganese dioxide slurry is used as a desulfurizer, and ammonia water or ammonium bicarbonate is used to adjust the pH of the desulfurized manganese slurry, avoiding problems that occur when other desulfurization methods are used, such as using lime slurry to absorb sulfur dioxide to generate calcium sulfate, resulting in a large amount of waste residue and easy plugging of the desulfurization tower system; the sodium content of the manganese sulfate product obtained by the process described in the application is less than 40ug / g, avoiding the problems of high cost of using sodium hydroxide to treat sulfur-containing flue gas, low value of generated sodium sulfate and difficulty in treatment, and avoiding the problem of high sodium content caused by the use of sodium hydroxide.

[0035] 4. Win-win of ecological benefit and economic benefit: the sulfur dioxide in the sulfur-containing flue gas is converted into the high-value manganese sulfate product, which realizes the ecological environment protection and the sulfur dioxide resource recycling, and achieves the win-win of ecological benefit and economic benefit.

[0036] 5. Energy saving and emission reduction: the process can reduce the washing water consumption per ton of product, and at least 2 tons of washing water per ton of product is saved.

[0037] 6. Wide application range: the pH value adjusting method and the related matching process in the flue gas desulfurization process are applicable to the treatment of the sulfur-containing flue gas, and can be widely used in the desulfurization of large flue gas emission enterprises such as steel enterprises, bituminous coal power plants, bituminous coal kilns and metallurgical industries. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The flow chart of the flue gas desulfurization process. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0040] Embodiment 1

[0041] A flue gas desulfurization process, comprising the following steps:

[0042] (1) manganese dioxide ore powder is added into a desulfurization manganese slurry storage tank, and water is added according to a solid-liquid ratio of 1:3 to prepare manganese slurry;

[0043] (2) ammonia water or ammonium bicarbonate with a concentration of 20% is added into the desulfurization manganese slurry storage tank to adjust the pH of the manganese slurry; the ammonia water in the ammonia water storage tank is self-flowed into the desulfurization manganese slurry through a pipeline, and the self-flowing amount of the ammonia water is controlled through a valve and a flow meter to ensure that the pH of the manganese slurry is between 3.5 and 5.0 during the absorption of the sulfur-containing flue gas; when the ammonia water in the storage tank is less or the tail gas fluctuates greatly, the ammonium bicarbonate and the ammonia water are added into the desulfurization manganese slurry to adjust the pH of the manganese slurry;

[0044] (3) the manganese dioxide ore slurry liquid after the pH adjustment is pumped into a desulfurization tower, the sulfur-containing flue gas is introduced into the desulfurization tower to react with the manganese dioxide ore slurry liquid to remove sulfur dioxide and generate manganese sulfate, the sulfur dioxide absorption rate is detected, the qualified tail gas after the absorption is discharged through a chimney, and the desulfurization manganese slurry is recycled for 3 times, and the reaction temperature is 80±2℃.

[0045] (4) The generated manganese sulfate slurry is filtered by pressure and then enters the manganese sulfate sulfidation acidification and impurity removal system for impurity removal to obtain refined manganese sulfate. A sample of manganese sulfate is taken for Ca analysis. 2+ Mg 2+ Na + Properties;

[0046] (5) The ammonium sulfate produced in the reaction is recovered through a deammoniation system to realize the recycling of ammonia resources.

[0047] Example 2

[0048] A flue gas desulfurization process includes the following steps:

[0049] (1) Add manganese dioxide ore powder to the desulfurized manganese slurry storage tank and add water at a solid-liquid ratio of 1:3 to prepare manganese slurry;

[0050] (2) Add 25% ammonia or ammonium bicarbonate to the desulfurization manganese slurry storage tank to adjust the pH of the manganese slurry. The ammonia in the desulfurization ammonia storage tank flows into the desulfurization manganese slurry by gravity through the pipeline. The gravity flow of the ammonia is controlled by valves and flow meters to ensure that the pH of the manganese slurry is between 3.5 and 5.0 during the absorption of sulfur-containing flue gas. When there is less ammonia in the storage tank or the tail gas fluctuates greatly, add ammonium bicarbonate and ammonia to the desulfurization manganese slurry to adjust the pH value of the manganese slurry.

[0051] (3) The pH-adjusted manganese dioxide slurry is pumped into the desulfurization tower. The sulfur-containing flue gas enters the desulfurization tower and reacts with the manganese dioxide slurry to remove sulfur dioxide and generate manganese sulfate. The sulfur dioxide absorption rate is tested. The qualified tail gas after absorption is discharged through the chimney. Continuous production is carried out. The desulfurized manganese slurry is recycled 5 times. The reaction temperature is 50-60℃.

[0052] (4) The generated manganese sulfate slurry is filtered by pressure and then enters the manganese sulfate sulfidation acidification and impurity removal system for impurity removal to obtain refined manganese sulfate. A sample of manganese sulfate is taken for Ca analysis. 2+ Mg 2+ Na + Properties;

[0053] (5) The ammonium sulfate produced in the reaction is recovered through a deammoniation system to realize the recycling of ammonia resources.

[0054] Example 3

[0055] A flue gas desulfurization process includes the following steps:

[0056] (1) Add manganese dioxide ore powder to the desulfurized manganese slurry storage tank and add water at a solid-liquid ratio of 1:3 to prepare manganese slurry;

[0057] (2) Add 10% ammonia or ammonium bicarbonate to the desulfurization manganese slurry storage tank to adjust the pH of the manganese slurry. The ammonia in the desulfurization ammonia storage tank flows into the desulfurization manganese slurry by gravity through the pipeline. The gravity flow of the ammonia is controlled by valves and flow meters to ensure that the pH of the manganese slurry is between 3.5 and 5.0 during the absorption of sulfur-containing flue gas. When there is less ammonia in the storage tank or the tail gas fluctuates greatly, add ammonium bicarbonate and ammonia to the desulfurization manganese slurry to adjust the pH value of the manganese slurry.

[0058] (3) The pH-adjusted manganese dioxide slurry is pumped into the desulfurization tower. The sulfur-containing flue gas enters the desulfurization tower and reacts with the manganese dioxide slurry to remove sulfur dioxide and generate manganese sulfate. The sulfur dioxide absorption rate is tested. The qualified tail gas after absorption is discharged through the chimney. The production is continuous. The desulfurized manganese slurry is recycled twice. The reaction temperature is 85-90℃.

[0059] (4) The generated manganese sulfate slurry is filtered by pressure and then enters the manganese sulfate sulfidation acidification and impurity removal system for impurity removal to obtain refined manganese sulfate. A sample of manganese sulfate is taken for Ca analysis. 2+ Mg 2+ Na + Properties;

[0060] (5) The ammonium sulfate produced in the reaction is recovered through a deammoniation system to realize the recycling of ammonia resources.

[0061] Example 4

[0062] A flue gas desulfurization process includes the following steps:

[0063] (1) Add manganese dioxide ore powder to the desulfurized manganese slurry storage tank and add water at a solid-liquid ratio of 1:3 to prepare manganese slurry;

[0064] (2) Add 15% ammonia or ammonium bicarbonate to the desulfurization manganese slurry storage tank to adjust the pH of the manganese slurry. The ammonia in the desulfurization ammonia storage tank flows into the desulfurization manganese slurry by gravity through the pipeline. The gravity flow of the ammonia is controlled by valves and flow meters to ensure that the pH of the manganese slurry is between 3.5 and 5.0 during the absorption of sulfur-containing flue gas. When there is less ammonia in the storage tank or the tail gas fluctuates greatly, add ammonium bicarbonate and ammonia to the desulfurization manganese slurry to adjust the pH value of the manganese slurry.

[0065] (3) The pH-adjusted manganese dioxide slurry is pumped into the desulfurization tower. The sulfur-containing flue gas enters the desulfurization tower and reacts with the manganese dioxide slurry to remove sulfur dioxide and generate manganese sulfate. The sulfur dioxide absorption rate is tested. The qualified tail gas after absorption is discharged through the chimney. The production is continuous. The desulfurized manganese slurry is recycled 4 times. The reaction temperature is 70±2℃.

[0066] (4) The generated manganese sulfate slurry is filtered by pressure and then enters the manganese sulfate sulfidation acidification and impurity removal system for impurity removal to obtain refined manganese sulfate. A sample of manganese sulfate is taken for Ca analysis. 2+ Mg2+ Na + Properties;

[0067] (5) The ammonium sulfate produced in the reaction is recovered through a deammoniation system to realize the recycling of ammonia resources.

[0068] Example 5

[0069] A flue gas desulfurization process includes the following steps:

[0070] (1) Add manganese dioxide ore powder to the desulfurized manganese slurry storage tank and add water at a solid-liquid ratio of 1:4 to prepare manganese slurry;

[0071] (2) Add 20% ammonia water or ammonium bicarbonate to the desulfurization manganese slurry storage tank to adjust the pH of the manganese slurry. The ammonia water in the desulfurization ammonia water storage tank flows into the desulfurization manganese slurry by gravity through the pipeline. The gravity flow of the ammonia water is controlled by valves and flow meters to ensure that the pH of the manganese slurry is between 3.0 and 5.5 during the absorption of sulfur-containing flue gas. When there is less ammonia water in the storage tank or the tail gas fluctuates greatly, add ammonium bicarbonate and ammonia water to the desulfurization manganese slurry to adjust the pH value of the manganese slurry.

[0072] (3) The pH-adjusted manganese dioxide slurry is pumped into the desulfurization tower. The sulfur-containing flue gas enters the desulfurization tower and reacts with the manganese dioxide slurry to remove sulfur dioxide and generate manganese sulfate. The sulfur dioxide absorption rate is tested. The qualified tail gas after absorption is discharged through the chimney. The production is continuous. The desulfurized manganese slurry is recycled 4 times. The reaction temperature is 75-85℃.

[0073] (4) The generated manganese sulfate slurry is filtered by pressure and then enters the manganese sulfate sulfidation acidification and impurity removal system for impurity removal to obtain refined manganese sulfate. A sample of manganese sulfate is taken for Ca analysis. 2+ Mg 2+ Na + Properties;

[0074] (5) The ammonium sulfate produced in the reaction is recovered through a deammoniation system to realize the recycling of ammonia resources.

[0075] Example 6

[0076] A flue gas desulfurization process includes the following steps:

[0077] (1) Add manganese dioxide ore powder to the desulfurized manganese slurry storage tank and add water at a solid-liquid ratio of 1:4 to prepare manganese slurry;

[0078] (2) Add 15% ammonia or ammonium bicarbonate to the desulfurization manganese slurry storage tank to adjust the pH of the manganese slurry. The ammonia in the desulfurization ammonia storage tank flows into the desulfurization manganese slurry by gravity through the pipeline. The gravity flow of the ammonia is controlled by valves and flow meters to ensure that the pH of the manganese slurry is between 3.0 and 5.5 during the absorption of sulfur-containing flue gas. When there is less ammonia in the storage tank or the tail gas fluctuates greatly, add ammonium bicarbonate and ammonia to the desulfurization manganese slurry to adjust the pH value of the manganese slurry.

[0079] (3) The pH-adjusted manganese dioxide slurry is pumped into the desulfurization tower. The sulfur-containing flue gas enters the desulfurization tower and reacts with the manganese dioxide slurry to remove sulfur dioxide and generate manganese sulfate. The sulfur dioxide absorption rate is tested. The qualified tail gas after absorption is discharged through the chimney. The production is continuous. The desulfurized manganese slurry is recycled 4 times. The reaction temperature is 65±2℃.

[0080] (4) The generated manganese sulfate slurry is filtered by pressure and then enters the manganese sulfate sulfidation acidification and impurity removal system for impurity removal to obtain refined manganese sulfate. A sample of manganese sulfate is taken for Ca analysis. 2+ Mg 2+ Na + Properties;

[0081] (5) The ammonium sulfate produced in the reaction is recovered through a deammoniation system to realize the recycling of ammonia resources.

[0082] Example 7

[0083] A flue gas desulfurization process includes the following steps:

[0084] (1) Add manganese dioxide ore powder to the desulfurized manganese slurry storage tank and add water at a solid-liquid ratio of 1:2 to prepare manganese slurry;

[0085] (2) Add 20% ammonia water or ammonium bicarbonate to the desulfurization manganese slurry storage tank to adjust the pH of the manganese slurry. The ammonia water in the desulfurization ammonia water storage tank flows into the desulfurization manganese slurry by gravity through the pipeline. The gravity flow of the ammonia water is controlled by valves and flow meters to ensure that the pH of the manganese slurry is between 3.0 and 5.5 during the absorption of sulfur-containing flue gas. When there is less ammonia water in the storage tank or the tail gas fluctuates greatly, add ammonium bicarbonate and ammonia water to the desulfurization manganese slurry to adjust the pH value of the manganese slurry.

[0086] (3) The pH-adjusted manganese dioxide slurry is pumped into the desulfurization tower. The sulfur-containing flue gas enters the desulfurization tower and reacts with the manganese dioxide slurry to remove sulfur dioxide and generate manganese sulfate. The sulfur dioxide absorption rate is tested. The qualified tail gas after absorption is discharged through the chimney. The production is continuous. The desulfurized manganese slurry is recycled 5 times. The reaction temperature is 55±2℃.

[0087] (4) The generated manganese sulfate slurry is filtered by pressure and then enters the manganese sulfate sulfidation acidification and impurity removal system for impurity removal to obtain refined manganese sulfate. A sample of manganese sulfate is taken for Ca analysis. 2+ Mg2+ Na + Properties;

[0088] (5) The ammonium sulfate produced in the reaction is recovered through a deammoniation system to realize the recycling of ammonia resources.

[0089] Example 8

[0090] A flue gas desulfurization process includes the following steps:

[0091] (1) Add manganese dioxide ore powder to the desulfurized manganese slurry storage tank and add water at a solid-liquid ratio of 1:2 to prepare manganese slurry;

[0092] (2) Add 25% ammonia or ammonium bicarbonate to the desulfurization manganese slurry storage tank to adjust the pH of the manganese slurry. The ammonia in the desulfurization ammonia storage tank flows into the desulfurization manganese slurry by gravity through the pipeline. The gravity flow of the ammonia is controlled by valves and flow meters to ensure that the pH of the manganese slurry is between 3.0 and 5.5 during the absorption of sulfur-containing flue gas. When there is less ammonia in the storage tank or the tail gas fluctuates greatly, add ammonium bicarbonate and ammonia to the desulfurization manganese slurry to adjust the pH value of the manganese slurry.

[0093] (3) The pH-adjusted manganese dioxide slurry is pumped into the desulfurization tower. The sulfur-containing flue gas enters the desulfurization tower and reacts with the manganese dioxide slurry to remove sulfur dioxide and generate manganese sulfate. The sulfur dioxide absorption rate is tested. The qualified tail gas after absorption is discharged through the chimney. Continuous production is carried out. The desulfurized manganese slurry is recycled 5 times. The reaction temperature is 50-60℃.

[0094] (4) The generated manganese sulfate slurry is filtered by pressure and then enters the manganese sulfate sulfidation acidification and impurity removal system for impurity removal to obtain refined manganese sulfate. A sample of manganese sulfate is taken for Ca analysis. 2+ Mg 2+ Na + Properties;

[0095] (5) The ammonium sulfate produced in the reaction is recovered through a deammoniation system to realize the recycling of ammonia resources.

[0096] Detection example

[0097] The results obtained from the processes in Examples 1-6 were summarized, and the effect of ammonia concentration on the SO2 desulfurization rate of flue gas is shown in Table 1 below:

[0098] Table 1. Effect of ammonia concentration on SO2 desulfurization rate of flue gas.

[0099] Serial number Concentration of ammonia water / % SO2 removal rate / % <!-- 6 --> 1 20 99.6 2 25 96.9 3 10 95.0 4 15 95.1 5 20 97.1 6 15 95.2 7 20 97.0 8 25 95.6

[0100] Multiple production practices, including the above examples, have demonstrated that using 20% ​​ammonia water can achieve a relatively stable reaction system and a good desulfurization effect.

[0101] The process described in this invention is used to desulfurize flue gas to produce crude manganese sulfate. After further purification by sulfidation and acidification, high-purity manganese sulfate is obtained, with calcium, magnesium, and sodium content all below 40 ppm. The high-purity manganese sulfate product obtained from the process in Example 1 was tested, and the results are shown in Table 2 below.

[0102] Table 2. Detection data of high-purity manganese sulfate product obtained by the process described in Example 1 of this invention.

[0103] Element K Na Ca Mg Cu Co Ni Pb Ti Al Zn Cd Fe Cr Magnetic substance Impurity content / ppm 1 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0 0 33 32 11 0.1 0.1 0.5 0.5 0.5 0.5 0.3 0.9 1.4 0.5 0.0495

[0104] The desulfurized manganese slag from the process described in this invention has a residual manganese content of (3-4)%, which can be used to prepare high-quality battery-grade manganese sulfate. Compared with the process of producing high-purity manganese sulfate by acid leaching of two ores, the washing process for obtaining high-purity manganese sulfate products in this invention can reduce the amount of washing water per ton of product, reduce the amount of washing water discharged by 2 tons per ton of product, and reduce the amount of washing water discharged by at least 2,000 tons per month with a production output of 1,000 tons.

[0105] In summary, the process described in this invention operates under mild conditions and is simple to use. It converts SO2 in flue gas into usable manganese sulfate, achieving the resource recovery and utilization of sulfur dioxide in flue gas. This generates economic benefits while reducing environmental pollution, providing a technical route for the treatment and resource utilization of sulfur-containing flue gas. The generated manganese sulfate can be used to prepare high-quality battery-grade manganese sulfate, providing raw materials for the new energy battery industry. The process method described in this invention aligns with the concept of combining ecological environmental protection and economic development, and has strong application value.

Claims

1. A flue gas desulfurization process, characterized in that, Includes the following steps: (1) Manganese dioxide powder was mixed with water to prepare manganese slurry according to a solid-liquid ratio of 1:(2-4); (2) The pH of the manganese slurry is adjusted by introducing 10-25% ammonia or ammonium bicarbonate to ensure that the pH of the manganese slurry is between 3.0 and 5.5 during the absorption of sulfur-containing flue gas; (3) Sulfur-containing flue gas enters the desulfurization tower and reacts with manganese slurry containing manganese dioxide ore powder to remove sulfur dioxide. The system temperature is 50-90℃, and manganese sulfate slurry is generated. The sulfur dioxide absorption rate is tested, and the qualified tail gas after absorption is discharged into the air. The desulfurized manganese slurry is recycled 2-5 times. (4) The generated manganese sulfate slurry is filtered by pressure and then enters the manganese sulfate sulfidation acidification and impurity removal system for impurity removal to obtain refined manganese sulfate. (5) After the manganese sulfate slurry containing ammonium sulfate is introduced into the manganese sulfate purification and impurity removal system, it is separated by pressure filtration, and the liquid is recycled through the deammoniation system.

2. The flue gas desulfurization process according to claim 1, characterized in that: In step (1), the solid-liquid ratio of manganese dioxide powder to water is 1:

3.

3. The flue gas desulfurization process according to claim 1, characterized in that: In step (2), the ammonia concentration used to adjust the pH is 20%.

4. The flue gas desulfurization process according to claim 1, characterized in that: Step (2) Ammonia or ammonium bicarbonate is introduced into the manganese slurry to adjust the pH, ensuring that the pH of the manganese slurry is between 3.5 and 5.0 during the absorption of sulfur-containing flue gas.

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