Process and device for preparing calcium sulfate whiskers from semi-dry desulfurization ash

Abstract

The invention discloses a process and a device for preparing calcium sulfate whiskers from semi-dry desulfurization ash. The process comprises the following steps: crushing the semi-dry desulfurization ash, and screening; carrying out iron removal treatment on qualified semi-dry desulfurization ash after screening; adding water into the deironed semi-dry desulfurization ash to prepare slurry, so as to obtain slurry; oxidizing the slurry; adding a hardening and tempering agent into the oxidized slurry, and hardening and tempering; sending the conditioned slurry into an evaporation kettle, and carrying out water bath crystallization; filtering the crystallization liquid to obtain a filter material and filtrate; drying the filter material; one part of the filtrate is used for pulping, potassium salt and sodium salt are extracted from the other part of the filtrate through a salt extraction process, and obtained clear water is used for pulping; and packaging the dried calcium sulfate whiskers. According to the invention, the semi-dry flue gas desulfurization ash is used as the raw material to prepare the calcium sulfate whisker, so that the pollution of the desulfurization ash to the environment can be reduced, the natural gypsum resource can be saved, and a new way is opened up for the high value-added utilization of the semi-dry flue gas desulfurization ash.

Description

Technical Field

[0001] The invention belongs to a solid waste resource treatment process, and in particular relates to a process and a device for preparing calcium sulfate whiskers by utilizing semi-dry desulfurization ash. Background Art

[0002] With increasingly stringent environmental protection requirements, sulfur dioxide control in flue gases from sintering processes, hot blast furnaces, and gas boilers in steel plants is a top priority. The majority of sulfur dioxide in these flue gases is removed using semi-dry desulfurization processes. This results in the generation of large amounts of desulfurization ash, which is currently primarily used in the cement surfacing of highways. A small amount is incorporated into cement, but the majority is used for paving. As road construction scales down in the future, significant amounts of desulfurization ash will need to be landfilled, creating serious environmental problems.

[0003] At present, most of the patents for producing gypsum whiskers use gypsum as raw material to produce whiskers.

[0004] Application number CN202222893764.0, "A device for preparing calcium sulfate whiskers using sintered flue gas desulfurization ash," uses a centrifuge as a filtering device. Due to the limitations of the centrifuge, it can only achieve small-scale production and cannot be used for industrial large-scale production. Gypsum whiskers are short fibers, and using a centrifuge to filter them will cause blockage of pipes and centrifuges, making continuous large-scale production impossible. The method of this patent lacks an immediate drying device, so the whiskers produced will undergo deliquesce and be reduced to gypsum, affecting the quality of the whiskers. Therefore, this patent is only suitable for laboratory use and cannot be used for industrial production. The patent also has serious flaws in the wastewater treatment process generated. The wastewater is treated by ion resin exchange. For example, the sodium chloride brine process is used to remove calcium and magnesium ions from the water. Not only will more wastewater be generated, but the new water obtained will also contain a large amount of sodium ions. If a yin and yang bed is used to treat the ions in the wastewater, a large amount of acid and alkali will be consumed, increasing the discharge of more high-salt wastewater.

[0005] Application number CN202211354173.4, "A method and apparatus for preparing calcium sulfate whiskers using sintered flue gas desulfurization ash," uses a centrifuge for filtration, which suffers from the same drawbacks as above and precludes industrial production. The hydrothermal reactor in this patent operates at a temperature of 60 to 80 degrees Celsius, representing a low-temperature, normal-pressure reaction. Furthermore, the reaction time is only 30 to 90 minutes, making it difficult to obtain qualified gypsum whiskers. The wastewater treatment method used in this patent also suffers from the same drawbacks as the above patent.

[0006] Application number CN201010545829.1, "Method for Preparing Calcium Sulfate Whiskers Using Sintered Ore Flue Gas Desulfurization Byproducts," uses oxygen, sodium hypochlorite, potassium hypochlorite, potassium chlorate, sodium chlorate, ammonium persulfate, calcium hypochlorite, or calcium chlorate as oxidants. These oxidants are costly and increase the difficulty of wastewater treatment, making them suitable only for laboratory production. The inhibitors used are sodium phosphate, nitric acid, magnesium phosphate, magnesium chloride, phosphoric acid, or sulfuric acid, with a mass concentration of 0.05% to 3% for nitric acid and 0.05% to 3% for sulfuric acid. These inhibitors are only suitable for wet desulfurization ash, the main component of which is desulfurization gypsum. They are not suitable for current semi-dry desulfurization ash, as the calcium hydroxide content in semi-dry desulfurization ash is 20% to 50%, requiring a large amount of sulfuric acid as an inhibitor, with a mass concentration of 5% to 30%. In addition, this patent has the defect of being unsuitable for industrial production. Since the sintering desulfurization ash contains a large amount of potassium and sodium salts, the filtrate must be subjected to salt extraction treatment during the production process to prevent the salt concentration in the filtrate from being too high and to extract the potassium and sodium salts in the filtrate.

[0007] Application number CN202410984528.0 "High aspect ratio hemihydrate gypsum whiskers and preparation method thereof" uses dihydrate gypsum as the raw material for gypsum production, and the process used has serious defects (the industrial raw materials contain a large amount of other salts, which need to be processed simultaneously; otherwise, as impurities and other salts accumulate, the method will not be able to proceed). This method can only be carried out in the laboratory and cannot be achieved in large-scale production.

[0008] Application number CN202410603363.8 "A method for preparing dihydrate gypsum whiskers" has the same situation as above. Gypsum is used as raw material to produce whiskers, and it can only be completed in the laboratory and cannot be used for large-scale production.

[0009] Application number CN202410513082.3, "A method for promoting the crystallization of phosphogypsum and the recycling of solutions," is similar to the above patent, using gypsum as the raw material to produce whiskers. Furthermore, using sodium nitrate solution as the medium for semi-dry desulfurization ash significantly increases operating costs (because sodium nitrate is an oxidizing agent, and a large amount of oxidized calcium sulfite in semi-dry desulfurization ash, accounting for about 30-50% of the total, will greatly increase the amount of sodium nitrate required). This method can only be completed in the laboratory and cannot be used for large-scale production.

[0010] Application number CN202410464062.1 "A method for preparing gypsum whiskers using industrial by-product gypsum" is the same as above, using gypsum as raw material to produce whiskers.

[0011] Application number CN202410354898.6, "A method for co-producing gypsum whiskers using calcium-containing solid waste and high-acid wastewater," is intended to treat arsenic-containing wastewater using calcium-containing solid waste. The product is low-grade gypsum, with gypsum whiskers being a byproduct. This process cannot guarantee the quality or quantity of the gypsum whiskers.

[0012] Application number CN202410129836.5, "A Method for Preparing Gypsum Whiskers and Ferric Phosphate," aims to produce battery-grade ferric phosphate, with gypsum whiskers as a byproduct. Due to the limited market capacity for ferric phosphate, the annual production of 100 million tons of semi-dry desulfurization ash cannot be absorbed.

[0013] Application number CN202310879332.0 "A method for directly preparing α-hemihydrate gypsum whiskers from titanium dioxide waste acid" uses calcium carbonate as raw material to process titanium dioxide waste acid to produce gypsum whiskers. Not only is the production cost high, but it is also unable to digest the annual output of 100 million tons of semi-dry desulfurization ash.

[0014] Application number CN202310410992.4 "A system for producing gypsum whiskers using citric acid gypsum" still uses gypsum as the raw material to produce gypsum whiskers.

[0015] Application number CN202311782923.2 "A new method for efficient resource utilization of sintering flue gas desulfurization gypsum in the steel industry" still uses gypsum as the raw material for raw gypsum whiskers.

[0016] In the existing technology center, there are a few patents that disclose the preparation of calcium sulfate whiskers using semi-dry desulfurization ash as raw material, but all of them have problems.

[0017] Application No. 202211354173.4, "A method and apparatus for preparing calcium sulfate whiskers using sintered flue gas desulfurization ash," involves: 1) preparing a slurry using semi-dry desulfurization ash dry powder; 2) converting SO₃⁻⁻ in the slurry to SO₄⁻⁻ using air aeration; 3) maintaining an initial temperature of 45°C and acidic conditions, feeding the slurry into a hydrothermal reactor at a temperature of 60-80°C for 30-90 minutes; 4) discharging the slurry into a centrifuge for solid-liquid separation, resulting in a mixture of 2H₂O calcium sulfate and 1 / 2H₂O calcium sulfate; 5) performing a second solid-liquid separation using centrifugation, resulting in 1 / 2H₂O calcium sulfate whiskers; 6) the solution after centrifugation is fed into a wastewater treatment process. Furthermore, the solution from the preparation process is treated in a dedicated wastewater treatment facility and reused as fresh water. The hydrothermal reactor temperature of this patent is 60 to 80 degrees, which is a low-temperature and normal-pressure reaction, and the reaction time is only 30 to 90 minutes, making it difficult to obtain qualified gypsum whiskers; this patent uses a centrifuge for centrifugal filtration, which has the disadvantage that it cannot be industrialized and is prone to clogging, making it difficult to carry out continuous large-scale production; the wastewater treatment method has defects, and when large-scale production is carried out, ordinary wastewater treatment processes cannot meet the system requirements, and the wastewater needs to be treated for salt extraction to extract potassium and sodium salts from the water and sell them as products.

[0018] Application No. 201710123480.4 "A method for preparing calcium sulfate whiskers from semi-dry desulfurization ash of sintering flue gas based on acid oxidation" is to mix an oxygen-enhancing agent with water to obtain an oxygen-enhancing agent solution, blow oxygen-containing gas into the mixture of desulfurization ash and water, and evenly inject the oxygen-enhancing agent solution into the bottom of the desulfurization ash mixture. The oxygen-enhancing agent includes an acidic auxiliary agent, and the pKa1 acidity coefficient of the acidic auxiliary agent is between the pKa1 acidity coefficients of sulfurous acid and sulfuric acid. The oxidized desulfurization ash is slurried and emulsified to obtain a slurry, and the slurry is subjected to a hydrothermal reaction to prepare calcium sulfate whiskers. This invention is only applicable to the production of calcium sulfate whiskers in the laboratory and cannot be applied to large-scale production. The patent requires: "mixing an oxygen-enhancing agent with water to obtain an oxygen-enhancing agent solution, blowing oxygen-containing gas into the mixture of desulfurization ash and water, and evenly injecting the oxygen-enhancing agent solution into the bottom of the desulfurization ash mixture", which are not suitable for large-scale production. The filtration method of this patent is "S6, water washing and drying: wash the reaction product with water 1-3 times, filter to obtain a filter cake; then place the filter cake in a drying oven to dry, and after drying, obtain CaSO4 whiskers." It can only be implemented in the laboratory.

[0019] Application No. 202110238158.2 "A method for preparing hemihydrate calcium sulfate whiskers using semi-dry desulfurization ash" uses powdered semi-dry desulfurization ash as raw material, fully oxidizes it under acidic conditions using hexavalent chromium wastewater, and then dehydrates and dries it to obtain oxidized desulfurization ash. A CaCl2-HCl mixed solution or a MgCl2-H2SO4 mixed solution is used as the base liquid, and a certain amount of oxidized desulfurization ash is added. After hydrothermal treatment, a hemihydrate calcium sulfate product is obtained, and the base liquid can be reused. This invention is only applicable to the production of calcium sulfate whiskers in the laboratory and cannot be applied to large-scale production. In large-scale production, the base liquid cannot be used for a long time, because when the potassium, sodium and other ions it contains are enriched to a certain extent, it will seriously affect the production of whiskers, so the base liquid must be treated for salt extraction. Summary of the Invention

[0020] The purpose of the present invention is to provide a process and device for preparing calcium sulfate whiskers using semi-dry desulfurization ash, so as to reduce the pollution of flue gas desulfurization by-products to the environment and save natural gypsum resources.

[0021] To achieve the above object, the present invention adopts the following technical solutions:

[0022] A process for preparing calcium sulfate whiskers using semi-dry desulfurization ash comprises the following steps:

[0023] (1) Crushing and screening the semi-dry desulfurization ash;

[0024] (2) performing iron removal treatment on the semi-dry desulfurization ash that has passed the screening in step (1);

[0025] (3) adding water to the semi-dry desulfurization ash after iron removal in step (2) to prepare a slurry;

[0026] (4) oxidizing the slurry obtained in step (3);

[0027] (5) adding a conditioning agent to the slurry oxidized in step (4) to perform conditioning;

[0028] (6) sending the slurry after conditioning in step (5) into an evaporator for water bath crystallization;

[0029] (7) filtering the crystallization liquid after crystallization in step (6) to obtain a filter material and a filtrate;

[0030] (8) drying the filter material obtained in step (7);

[0031] (9) A portion of the filtrate obtained in step (7) is used for pulping in step (3), and the other portion is subjected to a salt extraction process to extract potassium salt and sodium salt, and the resulting clear water is used for pulping in step (3);

[0032] (10) Packing the calcium sulfate whiskers obtained after drying in step (8).

[0033] Furthermore, in step (1), qualified desulfurization ash is screened and sent to step (2) for iron removal, and the coarse particles screened are repeatedly screened and crushed; in step (2), the iron removal process is carried out in a permanent magnetic iron removal device.

[0034] Furthermore, in step (3), the semi-dry desulfurization ash is mixed with water in a mass ratio of 1:4 to 1:15 for slurrying, and the slurry is stirred to make it uniform during the slurrying process; and steam is introduced to heat the slurry to a temperature of 50 to 70°C.

[0035] Furthermore, in the step (4), air or oxygen is introduced to perform aeration oxidation on the slurry, and the pressure of the air or oxygen is 0.2 to 0.8 MPa.

[0036] Furthermore, in step (5), a conditioning agent is first added, and then sulfuric acid is added to adjust the pH value of the slurry to between 1 and 5.5, and the slurry is stirred; the conditioning agent is one or more of an organic acid, an organic acid sodium salt, glycerol, erythritol, xylitol, sorbitol, sodium dodecylbenzenesulfonate, and sodium lauryl sulfate.

[0037] Furthermore, in step (6), the heating temperature of the water bath crystallization is 120-180° C., the heating time is 60-240 minutes, and continuous stirring is performed during the heating process.

[0038] Furthermore, in step (7), a vacuum filter or a plate and frame filter press is used for filtration.

[0039] Furthermore, in step (8), the drying is carried out using a vibrating fluidized bed drying device, a fluidized tower drying device or a tunnel furnace drying device, and the gas temperature used for drying is between 140°C and 600°C.

[0040] Furthermore, in the step (9), in the salt extraction process, the filtrate obtained by filtration is subjected to treatments such as impurity removal, clarification, and hardness removal to obtain a clean brine, and then the clean brine is evaporated, crystallized, and filtered to obtain lithium salt and sodium salt; the agent added in the impurity removal is a flocculant, sodium carbonate, or ammonium carbonate.

[0041] A device for preparing calcium sulfate whiskers using semi-dry desulfurization ash, comprising:

[0042] The raw material silo is used to store semi-dry desulfurization ash. A spiral discharger and an automatic weighing device are installed at the bottom of the raw material silo for quantitative transportation of semi-dry desulfurization ash.

[0043] The screening and crushing device is connected to the spiral discharger at the bottom of the raw material bin and is used to crush and screen the semi-dry desulfurization ash;

[0044] The permanent magnetic iron removal device is connected to the screening and crushing device and is used to remove iron from the semi-dry desulfurization ash;

[0045] The pulping device is connected to the permanent magnetic iron removal device. The pulping device is provided with an agitator and a steam heating device for adding water to the semi-dry desulfurization ash to make pulp;

[0046] A waterfall oxidation device, connected to the pulping device, is used to perform waterfall oxidation treatment on the slurry;

[0047] The dosing and tempering device is connected to the waterfall oxidation device and is used to temper the slurry;

[0048] The heating crystallization device is connected to the dosing and tempering device and is used to perform water bath crystallization treatment on the slurry;

[0049] The filtering device is connected to the heating crystallization device and the pulping device respectively, and is used to filter the crystallization liquid, and a part of the filtrate obtained by filtration is sent to the pulping device;

[0050] A drying device, connected to the filtering device, for drying the filter material obtained by the filtering process;

[0051] The salt extraction device is connected to the drying device and the pulping device respectively, and is used to extract salt from another part of the filtrate obtained by the filtration process, and send the obtained clean water to the pulping device;

[0052] The packaging device is connected to the drying device through a cyclone dust collector. The cyclone dust collector sends the dried calcium sulfate whiskers to the packaging device, and the packaging device packages the calcium sulfate whiskers.

[0053] Beneficial effects: The process and device for preparing calcium sulfate whiskers using semi-dry desulfurization ash of the present invention have the following advantages:

[0054] The preparation of calcium sulfate whiskers using semi-dry flue gas desulfurization ash as raw material can not only reduce the pollution of desulfurization ash to the environment, but also save natural gypsum resources, and open up a new way for the high value-added utilization of semi-dry flue gas desulfurization ash. The calcium sulfate whiskers are prepared through the following steps: slurrying, oxidation, conditioning, water bath crystallization, filtration, filtrate salt extraction, filter material drying, and packaging. The production cost is low and industrial-scale production can be achieved, which will produce significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The present invention discloses a process flow chart for preparing calcium sulfate whiskers by utilizing semi-dry desulfurization ash. DETAILED DESCRIPTION

[0056] The present invention will be further explained below with reference to the accompanying drawings.

[0057] like Figure 1 As shown, a process for preparing calcium sulfate whiskers using semi-dry desulfurization ash comprises the following steps:

[0058] (1) crushing the semi-dry desulfurization ash and screening it; after screening, the qualified desulfurization ash enters step (2) for iron removal, and the coarse particles under screening are repeatedly screened and crushed; the screening particle size can be set according to actual needs;

[0059] (2) removing iron from the semi-dry desulfurization ash that has passed the screening in step (1) in a permanent magnetic iron removal device;

[0060] (3) mixing the semi-dry desulfurization ash after iron removal in step (2) with water in a mass ratio of 1:4 to 1:15 to prepare pulp, stirring the pulp to make the pulp uniform during the pulping process; and heating the pulp with steam to make the pulp temperature reach 50 to 70° C.;

[0061] (4) introducing air or oxygen into the slurry obtained in step (3) to perform aeration oxidation on the slurry, wherein the pressure of the air or oxygen is 0.2 to 0.8 MPa;

[0062] (5) adding a conditioning agent to the slurry oxidized in step (4) for conditioning; then adding sulfuric acid to adjust the pH value of the slurry to between 1 and 5.5, and stirring the slurry; the conditioning agent is one or more of an organic acid, an organic acid sodium salt, glycerol, erythritol, xylitol, sorbitol, sodium dodecylbenzenesulfonate, and sodium lauryl sulfate;

[0063] (6) The slurry after conditioning in step (5) is fed into an evaporator for water bath crystallization. The heating temperature of the water bath crystallization is 120 to 180° C., the heating time is 60 to 240 minutes, and continuous stirring is performed during the heating process;

[0064] (7) filtering the crystallized liquid after the crystallization in step (6) using a vacuum filter or a plate and frame filter press to obtain a filter material and a filtrate;

[0065] (8) drying the filter material obtained in step (7) using a vibrating fluidized bed drying device, a fluidized tower drying device, or a tunnel furnace drying device, with the gas temperature for drying being between 140° C. and 600° C.;

[0066] (9) A portion of the filtrate obtained in step (7) is used for pulping in step (3), and the other portion is subjected to a salt extraction process to extract potassium salt and sodium salt, and the resulting clean water is used for pulping in step (3); in the salt extraction process, the filtrate obtained by filtration is subjected to a treatment to remove impurities, clarify, and remove hardness to obtain a clean brine, and then the clean brine is evaporated, crystallized, and filtered to obtain lithium salt and sodium salt; the agent added in the treatment to remove impurities is a flocculant, sodium carbonate, or ammonium carbonate;

[0067] (10) Packing the calcium sulfate whiskers obtained after drying in step (8).

[0068] A device for preparing calcium sulfate whiskers using semi-dry desulfurization ash, comprising:

[0069] The raw material silo is used to store semi-dry desulfurization ash. A spiral discharger and an automatic weighing device are installed at the bottom of the raw material silo for quantitative transportation of semi-dry desulfurization ash.

[0070] The screening and crushing device is connected to the spiral discharger at the bottom of the raw material bin and is used to crush and screen the semi-dry desulfurization ash;

[0071] The permanent magnetic iron removal device is connected to the screening and crushing device and is used to remove iron from the semi-dry desulfurization ash;

[0072] The pulping device is connected to the permanent magnetic iron removal device. The pulping device is provided with an agitator and a steam heating device for adding water to the semi-dry desulfurization ash to make pulp;

[0073] A waterfall oxidation device, connected to the pulping device, is used to perform waterfall oxidation treatment on the slurry;

[0074] The dosing and tempering device is connected to the waterfall oxidation device and is used to temper the slurry;

[0075] The heating crystallization device is connected to the dosing and tempering device and is used to perform water bath crystallization treatment on the slurry;

[0076] The filtering device is connected to the heating crystallization device and the pulping device respectively, and is used to filter the crystallization liquid, and a portion of the filtrate obtained by filtration is sent to the pulping device; the filtering device is preferably a vacuum filter or a plate and frame filter press;

[0077] A drying device connected to the filtering device is used to dry the filter material obtained by the filtering process; the drying device is preferably a vibrating fluidized bed drying device, a fluidized tower drying device or a tunnel furnace drying device;

[0078] The salt extraction device is connected to the drying device and the pulping device respectively, and is used to extract salt from the other part of the filtrate obtained by the filtration process and send the resulting clear water to the pulping device; the salt extraction device is equipped with a clarifier, an evaporation crystallization tank, and a heat exchanger;

[0079] The packaging device is connected to the drying device through a cyclone dust collector. The cyclone dust collector sends the dried calcium sulfate whiskers to the packaging device, and the packaging device packages the calcium sulfate whiskers.

[0080] The present invention will be further described below with reference to the embodiments.

[0081] Example 1

[0082] The present embodiment provides a process for preparing calcium sulfate whiskers using semi-dry desulfurization ash, which includes screening and crushing, iron removal, pulping, oxidation, conditioning, heating and crystallization, filtration, salt extraction from filtrate, filter material drying, and packaging.

[0083] The semi-dry desulfurization ash from the raw material bin is transported to the screening and crushing device through the spiral discharger and automatic weighing device at the bottom of the raw material bin. After screening, the qualified desulfurization ash is sent to the permanent magnetic iron removal device for iron removal, and the coarse particles that pass the screening are crushed. It is then returned to the screening device for further screening and repeated screening and crushing. The desulfurization ash after iron removal is sent to the pulping device and mixed with water to form a slurry. The desulfurization ash and water are mixed in a mass ratio of 1:10 for pulping. During the pulping process, the slurry is stirred to make it uniform. The slurry is steam heated and stirred. When the slurry is uniform and the temperature reaches 50-55°C, air is introduced for waterfall oxidation. The pressure of the introduced air is 0.2-0.8MPa. The oxidized slurry is then conditioned by adding the crystallization agents sodium lauryl sulfate and citric acid, followed by concentrated sulfuric acid. The pH of the slurry is adjusted to 2.5 and the slurry is stirred. After the slurry is uniform, it is sent to an evaporator for heating and crystallization at a temperature of 120-180°C for 60-240 minutes. During heating, the stirring device of the evaporator continuously stirs. When qualified whiskers are obtained after testing, the crystallized liquid in the evaporator is sent to a vacuum filter for filtration. The resulting filter material (whiskers) is then sent to a fluidized tower drying device via a conveyor for drying. The drying airflow is heated to 200°C using a hot air furnace. In the fluidized tower drying device, the filter material is fully mixed with the high-temperature flue gas and dried. The dried filter material (whiskers) and the hot flue gas are then sent through a pipeline to a cyclone dust collector. After passing through a wind dust collector, the dried filter material (whiskers) is sent to a finished product bin and then to a packaging device for packaging.

[0084] The crystallized liquid from the evaporation tank is sent to a filter press for filtration. A portion of the resulting filtrate is returned to the pulping unit for pulping, while the remaining portion is sent to the salt extraction unit for extraction of potassium and sodium salts. The resulting clear water is then returned to the pulping unit for pulping. During the salt extraction process, the filtrate is treated with impurity removal, clarification, and hardness removal to produce a clean brine. This clean brine is then evaporated, crystallized, and filtered to produce lithium and sodium salts. The agent added for impurity removal is a flocculant.

[0085] Example 2:

[0086] The present embodiment provides a process for preparing calcium sulfate whiskers using semi-dry desulfurization ash, which includes screening and crushing, iron removal, pulping, oxidation, conditioning, heating and crystallization, filtration, salt extraction from filtrate, filter material drying, and packaging.

[0087] The semi-dry desulfurization ash from the raw material bin is transported to the screening and crushing device through the spiral discharger and automatic weighing device at the bottom of the raw material bin. After screening, the qualified desulfurization ash is sent to the permanent magnetic iron removal device for iron removal, and the coarse particles that pass the screening are crushed. It is then returned to the screening device for further screening and repeated screening and crushing. The desulfurization ash after iron removal is sent to the pulping device and mixed with water to form a slurry. The desulfurization ash and water are mixed in a mass ratio of 1:15 for pulping. During the pulping process, the slurry is stirred to make it uniform. The slurry is steam heated and stirred. When the slurry is uniform and the temperature reaches 60-70°C, oxygen is introduced for waterfall oxidation. The pressure of the introduced oxygen is 0.2-0.8MPa. The oxidized slurry is then conditioned by adding a crystallization agent, sodium lauryl sulfate and citric acid, followed by concentrated sulfuric acid. The pH of the slurry is adjusted to 2.5, and the slurry is stirred. After the slurry is uniform, it is sent to an evaporator for heating and crystallization at a temperature of 120-180°C for 60-240 minutes. During heating, the stirring device of the evaporator continuously stirs. When qualified whiskers are obtained after testing, the crystallized liquid in the evaporator is sent to a plate and frame filter press for filtration. The resulting filter material (whiskers) is then sent to a vibrating fluidized bed drying device through a conveyor for drying. The drying airflow is heated to 150°C using a hot air furnace. In the vibrating fluidized bed drying device, the filter material is fully mixed with the high-temperature flue gas and dried. The dried filter material (whiskers) and the hot flue gas are then sent to a cyclone dust collector through a pipeline. After passing through a wind dust collector, the dried filter material (whiskers) is sent to a finished product warehouse and then to a packaging device for packaging.

[0088] The crystallized liquid from the evaporation tank is sent to a filter press for filtration. A portion of the resulting filtrate is returned to the pulping unit for pulping, while the remaining portion is sent to the salt extraction unit for extraction of potassium and sodium salts. The resulting clear water is then returned to the pulping unit for pulping. In the salt extraction process, the filtrate is treated with impurity removal, clarification, and hardness removal to produce a clean brine. This clean brine is then evaporated, crystallized, and filtered to produce lithium and sodium salts. The agent used for impurity removal is sodium carbonate.

[0089] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A process for preparing calcium sulfate whiskers using semi-dry desulfurization ash, characterized in that: The following steps are involved: (1) crushing and screening the semi-dry desulfurization ash; (2) removing iron from the semi-dry desulfurization ash that has passed the screening in step (1); (3) adding water to the semi-dry desulfurization ash after iron removal in step (2) to prepare slurry to obtain slurry; (4) oxidizing the slurry obtained in step (3); (5) adding a conditioning agent to the slurry oxidized in step (4) to perform conditioning; (6) sending the slurry after conditioning in step (5) into an evaporator for water bath crystallization; (7) filtering the crystallization liquid after the crystallization in step (6) to obtain a filter material and a filtrate; (8) drying the filter material obtained in step (7); (9) using a portion of the filtrate obtained in step (7) for pulping in step (3), and using the other portion of the filtrate in a salt extraction process to extract potassium salt and sodium salt, and using the resulting clean water for pulping in step (3); (10) Packaging the calcium sulfate whiskers obtained after drying in step (8).

2. A process for preparing calcium sulfate whiskers using semi-dry desulfurization ash according to claim 1, characterized in that: In the step (1), qualified desulfurization ash is screened and sent to step (2) for iron removal, and the coarse particles screened are repeatedly screened and crushed; in the step (2), the iron removal process is carried out in a permanent magnetic iron removal device.

3. A process for preparing calcium sulfate whiskers using semi-dry desulfurization ash according to claim 1, characterized in that: In the step (3), the semi-dry desulfurization ash is mixed with water in a mass ratio of 1:4 to 1:15 for slurrying, and the slurry is stirred to make it uniform during the slurrying process; and steam is introduced to heat the slurry to a temperature of 50 to 70°C.

4. A process for preparing calcium sulfate whiskers using semi-dry desulfurization ash according to claim 1, characterized in that: In the step (4), air or oxygen is introduced to perform aeration oxidation on the slurry, and the pressure of the air or oxygen is 0.2-0.8 MPa.

5. A process for preparing calcium sulfate whiskers using semi-dry desulfurization ash according to claim 1, characterized in that: In the step (5), a conditioning agent is first added, and then sulfuric acid is added to adjust the pH value of the slurry to between 1 and 5.5, and the slurry is stirred; the conditioning agent is one or more of an organic acid, an organic acid sodium salt, glycerol, erythritol, xylitol, sorbitol, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfate.

6. A process for preparing calcium sulfate whiskers using semi-dry desulfurization ash according to claim 1, characterized in that: In the step (6), the heating temperature of the water bath crystallization is 120 to 180° C., the heating time is 60 to 240 minutes, and continuous stirring is performed during the heating process.

7. A process for preparing calcium sulfate whiskers using semi-dry desulfurization ash according to claim 1, characterized in that: In the step (7), a vacuum filter or a plate and frame filter press is used for filtration.

8. A process for preparing calcium sulfate whiskers using semi-dry desulfurization ash according to claim 1, characterized in that: In the step (8), the drying is carried out by a vibrating fluidized bed drying device, a fluidized tower drying device or a tunnel furnace drying device, and the temperature of the gas used for drying is between 140°C and 600°C.

9. A process for preparing calcium sulfate whiskers using semi-dry desulfurization ash according to claim 1, characterized in that: In the step (9), in the salt extraction process, the filtrate obtained by filtration is subjected to treatments for impurity removal, clarification, and hardness removal to obtain a clean brine, and then the clean brine is evaporated, crystallized, and filtered to obtain lithium salt and sodium salt; the agent added in the impurity removal is a flocculant, sodium carbonate, or ammonium carbonate.

10. A device for preparing calcium sulfate whiskers using semi-dry desulfurization ash, characterized in that: include: The raw material bin is used to store semi-dry desulfurization ash. A spiral discharger and an automatic weighing device are installed at the bottom of the raw material bin to quantitatively transport the semi-dry desulfurization ash. The screening and crushing device is connected to the spiral discharger at the bottom of the raw material bin and is used to crush and screen the semi-dry desulfurization ash; The permanent magnetic iron removal device is connected to the screening and crushing device and is used to remove iron from the semi-dry desulfurization ash; A pulping device is connected to the permanent magnetic iron removal device, and is provided with a stirrer and a steam heating device for pulping the semi-dry desulfurization ash by adding water; A gas oxidation device, connected to the pulping device, is used to perform gas oxidation treatment on the pulp; A dosing conditioning device, connected to the waterfall oxidation device, is used to condition the slurry; A heating crystallization device, connected to the dosing and conditioning device, is used to perform water bath crystallization treatment on the slurry; The filtering device is connected to the heating crystallization device and the pulping device respectively, and is used to filter the crystallization liquid, and a part of the filtrate obtained by filtration is sent to the pulping device; A drying device, connected to the filtering device, for drying the filter material obtained by the filtering process; The salt extraction device is connected to the drying device and the pulping device respectively, and is used to extract salt from another part of the filtrate obtained by the filtration process, and send the obtained clean water to the pulping device; The packaging device is connected to the drying device through a cyclone dust collector. The cyclone dust collector sends the dried calcium sulfate whiskers to the packaging device, and the packaging device packages the calcium sulfate whiskers.

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