Method for preparing aluminum sulfate for alkali-free accelerator from chlorine-containing waste sulfuric acid

Abstract

The invention discloses a method for preparing aluminum sulfate for an alkali-free accelerator from chlorine-containing waste sulfuric acid, and belongs to the technical field of chlor-alkali wastewater treatment. The method comprises the following steps: S1, introducing compressed air into the chlorine-containing waste sulfuric acid for chlorine blowing treatment; s2, mixing and stirring the waste sulfuric acid subjected to chlorine blowing treatment in S1 with water to obtain diluted waste sulfuric acid; and S3, adding aluminum hydroxide powder into the diluted waste sulfuric acid obtained in the S2, heating and curing, and adding water for diluting to obtain the aluminum sulfate for the alkali-free accelerator. The chlorine-containing waste sulfuric acid is used as the raw material to prepare the alkali-free accelerator aluminum sulfate, the preparation process is simple, the energy consumption is low, the production cost is low, and the obtained liquid aluminum sulfate meets the general requirements of the alkali-free accelerator and titanium dioxide coating; the problems that a large amount of acid-containing tail gas is discharged, environmental pollution is serious, material consumption and energy consumption are high, reaction is incomplete, the raw material conversion rate is low, and the settling volume in the production process is large in the chlor-alkali waste sulfuric acid treatment and aluminum sulfate preparation process are solved, and the method has wide application prospects.

Description

Technical Field

[0001] This invention relates to the field of chlor-alkali wastewater treatment technology, specifically to a method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid. Background Technology

[0002] In the chlor-alkali production process, the chlorine gas exiting the electrolytic cell is at a high temperature and has a high water content, requiring cooling and drying before being sent to subsequent stages by compressors. Currently, the domestic chlor-alkali industry uses concentrated sulfuric acid drying. After absorbing the moisture from the chlorine gas, the concentration of concentrated sulfuric acid gradually decreases. When the concentration is diluted to around 78%, it no longer meets the drying requirements, and the sulfuric acid at this point becomes waste sulfuric acid, unusable for further drying. Statistics show that chlor-alkali enterprises generate 13-21 kg of chlorine-containing waste sulfuric acid for every ton of caustic soda produced. This waste sulfuric acid is a toxic, highly corrosive, and difficult-to-treat industrial waste. With the increasing severity of environmental problems, the resource utilization of waste sulfuric acid has become an inevitable choice.

[0003] The main methods for treating waste sulfuric acid include: concentration, high-temperature pyrolysis, and the production of fertilizers and various sulfates. Among these, concentration requires high-quality equipment, involves significant investment, is complex to operate, and has a low throughput. High-temperature reduction pyrolysis requires large investments and consumes a lot of energy; handling waste sulfuric acid with high fluorine, chlorine, and metal salt content can easily cause corrosion and blockage of equipment and pipelines. Fertilizer production requires prior purification to remove harmful impurities; incomplete purification can lead to soil pollution. Therefore, currently, most chlor-alkali enterprises transfer waste sulfuric acid to qualified units for disposal at a cost of additional transportation and disposal fees. However, because this waste sulfuric acid contains a large amount of free chlorine, its corrosiveness is increased, making many enterprises unwilling to accept it, often resulting in overflowing storage facilities. Furthermore, trace amounts of chlorine gas are released during transportation and use, polluting the environment. The collection, storage, transportation, and disposal of waste sulfuric acid have become bottlenecks restricting chlor-alkali production.

[0004] Traditional aluminum sulfate preparation involves directly heating with steam and reacting aluminum hydroxide powder and concentrated sulfuric acid at atmospheric pressure and boiling for approximately 4 hours. During the reaction, a large amount of acidic exhaust gas is emitted until the reaction is complete, causing environmental pollution. The escape of acid and steam also leads to high material and energy consumption. Furthermore, incomplete reaction, low raw material conversion rate, and significant sedimentation during production also contribute to the problem. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, the purpose of this invention is to provide a method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid, so as to solve the problems of existing aluminum sulfate preparation processes, such as large-scale emission of acidic tail gas, serious environmental pollution, high material and energy consumption, incomplete reaction, low raw material conversion rate, and large amount of sedimentation during production.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid includes the following steps: S1. Pass compressed air into the chlorine-containing waste sulfuric acid for chlorine blowing treatment; S2. Mix the waste sulfuric acid after chlorination treatment in S1 with water and stir to obtain diluted waste sulfuric acid; S3. Add aluminum hydroxide powder to the diluted waste sulfuric acid obtained in S2, heat to mature, dilute with water, and obtain aluminum sulfate for alkali-free quick-setting agent.

[0007] The beneficial effects of this invention are as follows: This invention uses chlorine-containing waste sulfuric acid as raw material to prepare alkali-free quick-setting agent aluminum sulfate. The preparation process is simple, energy consumption is low, and production cost is low. The obtained liquid aluminum sulfate meets the general requirements of alkali-free quick-setting agents and titanium dioxide coating, solves the disposal problem of chlor-alkali waste sulfuric acid, and has broad application prospects.

[0008] Furthermore, the dechlorination treatment time in S1 is 1-2 hours.

[0009] Furthermore, the free chlorine content in the waste hydrochloric acid after chlorine blowing treatment in S1 is ≤100 ppm.

[0010] The beneficial effects of adopting the above-mentioned further technical solution are as follows: the present invention continuously bubbles in waste sulfuric acid by introducing compressed air, and carries out the free chlorine in the waste sulfuric acid, thereby achieving the preliminary dechlorination of chlorine-containing waste sulfuric acid.

[0011] Furthermore, the mixing time in S2 is 20-40 min.

[0012] Furthermore, the mass concentration of sulfuric acid in the diluted waste sulfuric acid in S2 is 55%-60%.

[0013] Furthermore, the free chlorine content in the diluted waste sulfuric acid in S2 is ≤50 ppm.

[0014] The beneficial effects of adopting the above-mentioned further technical solution are as follows: By utilizing the dilution heat generated during the dilution process of chlorine-containing waste sulfuric acid and the stirring process, the present invention further releases the free chlorine remaining in the chlorine-containing waste hydrochloric acid, thereby achieving further dechlorination of the chlorine-containing waste sulfuric acid.

[0015] Furthermore, the mass ratio of 100% sulfuric acid to 100% aluminum hydroxide in S3 is 1.8-2.3.

[0016] Furthermore, the heating and ripening temperature in S3 is 100-120℃, and the time is 30-45 min.

[0017] The beneficial effects of adopting the above-mentioned further technical solution are as follows: the present invention reacts by slowly adding aluminum hydroxide powder after dechlorination, and the temperature of the reaction liquid gradually increases during the feeding process, which reduces the heat required for subsequent steam heating and reduces the production cost. After heat preservation and curing, aluminum sulfate for alkali-free quick-setting agent is successfully prepared.

[0018] The present invention has the following beneficial effects: 1. This invention uses chlorine-containing waste sulfuric acid as raw material to prepare aluminum sulfate for alkali-free rapid coagulation. It combines compressed air stripping for dechlorination with a dilution reaction for further dechlorination, achieving rapid dechlorination of chlorine-containing waste sulfuric acid to meet the needs of subsequent preparation of alkali-free rapid coagulation agent aluminum sulfate. Compared with traditional vacuum evaporation dechlorination processes, this invention eliminates the need for a dedicated dechlorination device; only simple equipment modifications such as adding a gas distribution pipe to the bottom of the existing dilute acid storage tank are required, significantly reducing the dechlorination cost of chlorine-containing waste sulfuric acid.

[0019] 2. Compared with existing waste sulfuric acid recovery processes such as waste sulfuric acid concentration and high-temperature pyrolysis, this invention requires less new process equipment, lower investment, and lower operating energy consumption, achieving effective utilization of chlorine-containing waste sulfuric acid and solving the disposal problem of chlor-alkali waste sulfuric acid.

[0020] 3. The liquid aluminum sulfate prepared by this invention has an aluminum oxide mass fraction of about 7% and a chloride ion mass fraction of about 0.05%, which is far lower than the general requirements for alkali-free quick-setting agents (GB / T35159-2017) where the chloride ion content is ≤0.1%; the iron content is about 15ppm, which is also lower than the requirements for aluminum sulfate used for titanium dioxide coating. Detailed Implementation

[0021] The principles and features of the present invention are described below with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, specific conditions or manufacturer-recommended conditions should be followed in the embodiments. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0022] Example 1: A method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid includes the following steps: S1, Chlorine blowing treatment The chlorine-containing waste sulfuric acid (78% sulfuric acid mass concentration, 5.6 g / L chloride ion concentration) in the waste sulfuric acid storage tank is poured into the waste acid pretreatment tank through the waste acid pump. The exhaust gas pipeline valve and compressed air purging pipe valve of the exhaust gas treatment system at the top of the waste acid pipe are opened, and compressed air is used to blow away the chlorine for 1.5 h. The sample is taken for analysis, and the free chlorine content is ≤100 ppm. Then it is transferred to the high-level metering tank for later use.

[0023] S2, Dilution and chlorine removal After starting the alkaline washing and absorption system for the waste gas from the reactor, the valves from the high-level metering tanks for pure water and waste sulfuric acid to the enamel-lined reactor were opened one after another. 0.6 tons of pure water and 1.6 tons of waste sulfuric acid were added for dilution. When the liquid level in the enamel-lined reactor was above the bottom of the stirring device, the stirring device was started. After the water and acid were added, stirring was continued for 30 minutes. The sample analysis showed that the free chlorine in the waste acid was 48 ppm and the sulfuric acid mass concentration was 57%.

[0024] S3, aluminum acid reaction Start the aluminum hydroxide feeding device and slowly add 0.7 tons of aluminum hydroxide powder to the enamel-lined reactor. The acid-aluminum ratio (mass ratio of 100% sulfuric acid to 100% aluminum hydroxide) is 1.86. After the feeding is completed, the temperature of the reaction solution reaches 108℃. Slowly open the steam heating valve of the reactor and raise the temperature to 110℃. Maintain the temperature for 40 minutes to ripen the reaction. When no solid particles are found in the reaction solution and the solution is transparent and gel-like, stop the steam supply.

[0025] S4. Dilute with water to prepare the final product. Add 3.6 tons of pure water to the enamel-lined reactor to dilute the aluminum sulfate product. At the same time, use circulating water to lower the temperature of the reaction solution to 60°C. Then, open the discharge valve at the bottom of the reactor to allow the liquid aluminum sulfate to pass through a membrane filter. After filtration, take a sample for analysis and send the product to the liquid aluminum sulfate storage tank.

[0026] Analysis revealed that the liquid aluminum sulfate prepared in this embodiment contained 7.2% aluminum oxide (ANO) by mass, 0.05% chloride ions by mass, and 14 mg / L iron. The results show that the chloride ion content of the liquid aluminum sulfate prepared using this process is approximately 0.05%, far below the general requirements for alkali-free quick-setting agents (GB / T35159-2017), and the iron content is below 15 mg / L, also far below the requirements for aluminum sulfate used in titanium dioxide coating. This indicates that this embodiment achieves rapid and low-cost preparation of alkali-free quick-setting agent aluminum sulfate from chlorinated waste sulfuric acid, without requiring additional industrial equipment, thus significantly reducing production costs.

[0027] Example 2: A method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid includes the following steps: S1, Chlorine blowing treatment The chlorine-containing waste sulfuric acid in the waste sulfuric acid storage tank is poured into the waste acid pretreatment tank through the waste acid pump. The exhaust gas pipeline valve and compressed air purging pipe valve of the exhaust gas treatment system at the top of the waste acid pipe are opened, and compressed air is used to blow away the chlorine for 1 hour. The sample is taken for analysis. The free chlorine content is ≤100 ppm. Then it is transferred to the high-level metering tank for later use.

[0028] S2, Dilution and chlorine removal After starting the alkaline washing and absorption system for the waste gas from the reactor, the valves from the high-level metering tanks for pure water and waste sulfuric acid to the enamel-lined reactor were opened one after another. 0.7 tons of pure water and 1.9 tons of waste sulfuric acid were added for dilution. When the liquid level in the enamel-lined reactor was above the bottom of the stirring device, the stirring device was started. After the water and acid were added, stirring was continued for 30 minutes. The free chlorine in the waste acid was 50 ppm when sampled and analyzed.

[0029] S3, aluminum acid reaction Start the aluminum hydroxide feeding device and slowly add 0.8 tons of aluminum hydroxide powder into the enamel-lined reactor. The acid-aluminum ratio (mass ratio of 100% sulfuric acid to 100% aluminum hydroxide) is 1.9. After the feeding is completed, the temperature of the reaction solution reaches 108℃. Slowly open the steam heating valve of the reactor and raise the temperature to 110℃. Maintain the temperature for 35 minutes to ripen the reaction. When no solid particles are found in the reaction solution and the solution is transparent and gel-like, stop the steam supply.

[0030] S4. Dilute with water to prepare the final product. Add 4.3 tons of pure water to the enamel-lined reactor to dilute the aluminum sulfate product. At the same time, use circulating water to lower the temperature of the reaction solution to 60°C. Then, open the discharge valve at the bottom of the reactor to allow the liquid aluminum sulfate to pass through a membrane filter. After filtration, take a sample for analysis and send the product to the liquid aluminum sulfate storage tank.

[0031] Analysis revealed that the liquid aluminum sulfate prepared in this embodiment contained 6.8% aluminum oxide (ANO) by mass, 0.04% chloride ions by mass, and 15 mg / L iron. The results show that the chloride ion content of the liquid aluminum sulfate prepared using this process is approximately 0.04%, far below the general requirements for alkali-free quick-setting agents (GB / T35159-2017), and the iron content is approximately 15 mg / L, also far below the requirements for aluminum sulfate used in titanium dioxide coating. This indicates that this embodiment achieves rapid and low-cost preparation of alkali-free quick-setting agent aluminum sulfate from chlorinated waste sulfuric acid, without requiring additional industrial equipment, thus significantly reducing production costs.

[0032] Example 3: A method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid includes the following steps: S1, Chlorine blowing treatment The chlorine-containing waste sulfuric acid in the waste sulfuric acid storage tank is poured into the waste acid pretreatment tank through the waste acid pump. The exhaust gas pipeline valve and compressed air purging pipe valve of the exhaust gas treatment system at the top of the waste acid pipe are opened, and compressed air is used to blow away the chlorine for 2 hours. Samples are taken for analysis. The free chlorine content is ≤100 ppm. Then it is transferred to the high-level metering tank for later use.

[0033] S2, Dilution and chlorine removal After starting the alkaline washing and absorption system for the waste gas from the reactor, the valves from the high-level metering tanks for pure water and waste sulfuric acid to the enamel-lined reactor were opened one after another. 0.66 tons of pure water and 1.84 tons of waste sulfuric acid were added for dilution. When the liquid level in the enamel-lined reactor was above the bottom of the stirring device, the stirring device was started. After the water and acid were added, stirring was continued for 30 minutes until no chlorine odor was emitted from the reactor.

[0034] S3, aluminum acid reaction Start the aluminum hydroxide feeding device and slowly add 0.675 tons of aluminum hydroxide powder into the enamel-lined reactor. The acid-aluminum ratio (mass ratio of 100% sulfuric acid to 100% aluminum hydroxide) is 2.2. After the feeding is completed, the temperature of the reaction solution reaches 108℃. Slowly open the steam heating valve of the reactor and raise the temperature to 110℃. Maintain the temperature for 40 minutes to ripen the reaction. When no solid particles are found in the reaction solution and the solution is transparent and gel-like, stop the steam supply.

[0035] S4. Dilute with water to prepare the final product. Add 2.5 tons of pure water to the enamel-lined reactor to dilute the aluminum sulfate product. At the same time, use circulating water to lower the temperature of the reaction solution to 60°C. Then, open the discharge valve at the bottom of the reactor to allow the liquid aluminum sulfate to pass through a membrane filter. After filtration, take a sample for analysis and send the product to the liquid aluminum sulfate storage tank.

[0036] Analysis revealed that the liquid aluminum sulfate prepared in this embodiment had an aluminum oxide content of 7.8% (103.6 mg / L), a chloride ion concentration of 4.34 mg / L, and an iron concentration of 15.12 mg / L. The results show that the chloride ion content of the liquid aluminum sulfate prepared using this process is approximately 0.04%, far below the general requirements for alkali-free quick-setting agents (GB / T35159-2017), and the iron content is approximately 15 mg / L, also far below the requirements for aluminum sulfate used in titanium dioxide coating. This indicates that this embodiment achieves rapid and low-cost preparation of alkali-free quick-setting agent aluminum sulfate from chlorinated waste sulfuric acid, without requiring additional industrial equipment, thus significantly reducing production costs.

[0037] Comparative Example 1: A method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid includes the following steps: S1, Chlorine blowing treatment The chlorine-containing waste sulfuric acid in the waste sulfuric acid storage tank is poured into the waste acid pretreatment tank through the waste acid pump. The exhaust gas pipeline valve and compressed air purging pipe valve of the exhaust gas treatment system at the top of the waste acid pipe are opened, and compressed air is used to blow away chlorine for 1.5 hours. Samples are taken for analysis. The free chlorine content is ≤100 ppm. Then it is transferred to the high-level metering tank for later use.

[0038] S2, Dilution and chlorine removal After starting the alkaline washing and absorption system for the waste gas from the reactor, open the valves from the high-level metering tanks for pure water and waste sulfuric acid to the enamel-lined reactor, and add 0.6 tons of pure water and 1.6 tons of waste sulfuric acid for dilution. When the liquid level in the enamel-lined reactor exceeds the bottom of the stirring device, start the stirring device. After the water and acid are added, immediately start the aluminum hydroxide feeding device for S3.

[0039] S3, aluminum acid reaction Start the aluminum hydroxide feeding device and slowly add 0.65 tons of aluminum hydroxide powder into the enamel-lined reactor. The acid-aluminum ratio (mass ratio of 100% sulfuric acid to 100% aluminum hydroxide) is 2. After the feeding is completed, slowly open the steam heating valve of the reactor and raise the temperature to 110°C. Keep the temperature and mature the reaction for 35 minutes. When no solid particles are found in the reaction liquid and the solution is transparent and gel-like, stop the steam supply.

[0040] S4. Dilute with water to prepare the final product. Add 3.6 tons of pure water to the enamel-lined reactor to dilute the aluminum sulfate product. At the same time, use circulating water to lower the temperature of the reaction solution to 60°C. Then, open the discharge valve at the bottom of the reactor to allow the liquid aluminum sulfate to pass through a membrane filter. After filtration, take a sample for analysis and send the product to the liquid aluminum sulfate storage tank.

[0041] Analysis revealed that the liquid aluminum sulfate prepared in this example contained 6.8% aluminum oxide by mass, 1.1% chloride ions by mass, and 15 mg / L iron. The results showed that in this comparative example, the lack of continued stirring after the addition of water and acid in step S2 resulted in an excessively high chloride ion content of 1.1% in the final liquid aluminum sulfate, far exceeding the general requirements for alkali-free quick-setting agents (GB / T35159-2017), thus failing to meet production needs.

[0042] Comparative Example 2: A method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid includes the following steps: S1, Chlorine blowing treatment The chlorine-containing waste sulfuric acid in the waste sulfuric acid storage tank is poured into the waste acid pretreatment tank through the waste acid pump. The exhaust gas pipeline valve and compressed air purging pipe valve of the exhaust gas treatment system at the top of the waste acid pipe are opened, and compressed air is used to blow away the chlorine for 1 hour. The sample is taken for analysis. The free chlorine content is ≤100 ppm. Then it is transferred to the high-level metering tank for later use.

[0043] S2, Dilution and chlorine removal After starting the alkaline washing and absorption system for the waste gas from the reactor, open the valves from the high-level metering tanks for pure water and waste sulfuric acid to the enamel reactor, and add 0.7 tons of pure water and 1.9 tons of waste sulfuric acid for dilution. When the liquid level in the enamel reactor exceeds the bottom of the stirring device, start the stirring device. After the water and acid are added, immediately start the aluminum hydroxide feeding device for S3.

[0044] S3, aluminum acid reaction Start the aluminum hydroxide feeding device and slowly add 0.8 tons of aluminum hydroxide powder into the enamel-lined reactor. The acid-aluminum ratio (mass ratio of 100% sulfuric acid to 100% aluminum hydroxide) is 1.9. After the feeding is completed, slowly open the steam heating valve of the reactor and raise the temperature to 110°C. Keep the temperature and mature the reaction for 35 minutes. When no solid particles are found in the reaction liquid and the solution is transparent and gel-like, stop the steam supply.

[0045] S4. Dilute with water to prepare the final product. Add 4.3 tons of pure water to the enamel-lined reactor to dilute the aluminum sulfate product. At the same time, use circulating water to lower the temperature of the reaction solution to 60°C. Then, open the discharge valve at the bottom of the reactor to allow the liquid aluminum sulfate to pass through a membrane filter. After filtration, take a sample for analysis and send the product to the liquid aluminum sulfate storage tank.

[0046] Analysis revealed that the liquid aluminum sulfate prepared in this example contained 6.8% aluminum oxide by mass, 1.1% chloride ions by mass, and 14 mg / L iron. The results showed that, similarly in this comparative example, the lack of continued stirring after the addition of water and acid in step S2 resulted in an excessively high chloride ion content of 1.1% in the final liquid aluminum sulfate, far exceeding the general requirements for alkali-free quick-setting agents (GB / T35159-2017), thus failing to meet production needs.

[0047] Comparative Example 3: A method for preparing alkali-free quick-setting agent using sulfuric acid in the laboratory includes the following steps: 84.6 g of 75.16% sulfuric acid was added to a three-necked flask, the stirrer was started, and 32.57 g of aluminum hydroxide powder was added. The heating device was then activated, and the reaction was stirred. When the temperature reached 92°C, the reactants agglomerated, and the reaction could not continue. Analysis revealed that the generated aluminum sulfate was too concentrated, causing crystals to precipitate and encapsulate the unreacted aluminum hydroxide, leading to the interruption of the reaction and incomplete reaction. Therefore, the industrial-scale preparation of liquid aluminum sulfate could not be achieved.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid, characterized in that, Includes the following steps: S1. Pass compressed air into the chlorine-containing waste sulfuric acid for chlorine blowing treatment; S2. Mix the waste sulfuric acid after chlorination treatment in S1 with water and stir to obtain diluted waste sulfuric acid; S3. Add aluminum hydroxide powder to the diluted waste sulfuric acid obtained in S2, heat to mature, dilute with water, and obtain aluminum sulfate for alkali-free quick-setting agent.

2. The method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid according to claim 1, characterized in that, The dechlorination process in S1 takes 1-2 hours.

3. The method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid according to claim 1, characterized in that, The free chlorine content in the waste hydrochloric acid after chlorine blowing treatment in S1 is ≤100 ppm.

4. The method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid according to claim 1, characterized in that, The mixing time in S2 is 20-40 min.

5. The method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid according to claim 1, characterized in that, The mass concentration of sulfuric acid in the diluted waste sulfuric acid in S2 is 55%-60%.

6. The method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid according to claim 1, characterized in that, The free chlorine content in the diluted waste sulfuric acid in S2 is ≤50 ppm.

7. The method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid according to claim 1, characterized in that, The mass ratio of 100% sulfuric acid to 100% aluminum hydroxide in S3 is 1.8-2.

3.

8. The method for preparing alkali-free quick-setting agent aluminum sulfate from chlorine-containing waste sulfuric acid according to claim 1, characterized in that, The heating and ripening temperature in S3 is 100-120℃, and the time is 30-45 min.