A system for preparing ferrous sulfate and ferric ion-containing inorganic polymers from waste sulfuric acid.

Abstract

A system for preparing ferrous sulfate and iron-containing inorganic polymers from waste sulfuric acid includes a storage tank, a first reaction tank connected to the storage tank and receiving ferrous sulfate solution obtained by reacting waste sulfuric acid solution with an iron source, a filtration device connected to the first reaction tank for filtering the ferrous sulfate solution, a second reaction tank connected to the filtration device and connected to an acid supply tank and an oxidant supply device, into which acidic solvent and oxidant are added to the second reaction tank to polymerize with the ferrous sulfate solution to obtain a polyferric sulfate solution, and an evaporator connected to both the filtration device and the second reaction tank to evaporate and concentrate the ferrous sulfate solution or the polyferric sulfate solution, followed by cooling in a first crystallizer to precipitate ferrous sulfate crystals or polyferric sulfate crystals, thus realizing the production of different finished products from waste sulfuric acid to meet market demand.

Description

Technical Field

[0001] This invention relates to a system for preparing ferrous sulfate or ferric ion-containing inorganic polymers, and more particularly to a system for preparing ferrous sulfate and ferric ion-containing inorganic polymers using waste sulfuric acid. Prior Technology

[0002] Sulfuric acid is a commonly used acid in industrial production. In the era of the circular economy, how to handle the waste sulfuric acid solution generated after production is a matter of great concern to industries. Taiwan's semiconductor industry is booming, and high-concentration sulfuric acid is often used for etching during wafer fabrication. The large amount of waste sulfuric acid produced after this process still has a very high concentration and can still be used as raw material for the steel industry. Therefore, it can be recycled and supplied to other industries. However, the current output of waste sulfuric acid from the semiconductor industry far exceeds the domestic market demand, and the waste sulfuric acid produced by other integrated industries has a relatively low concentration and is not suitable for metal processing. How to rationally recycle and utilize the above-mentioned waste sulfuric acid solution has become an urgent problem to be solved. Therefore, it is necessary to develop new and powerful recycling and reuse channels to solve the problem of excessive waste sulfuric acid produced domestically.

[0003] With industrial development and the promotion of green circular economy policies, wastewater treatment has become an urgent issue that needs to be addressed in industrial development. Ferrous sulfate and iron-containing polymers such as polyferric sulfate and polyaluminum ferric sulfate are commonly used in the industry due to their excellent water purification effect, good coagulation performance, and wide adaptability to various pH ranges of water bodies. They are widely used to purify various highly turbid industrial wastewaters and municipal sewage. Utilizing the large quantities of domestically produced waste sulfuric acid to generate ferrous sulfate and iron-containing polymers not only meets market demand but also effectively recycles waste sulfuric acid, reduces waste sulfuric acid emissions, and meets green environmental protection requirements.

[0004] However, the systems used in the industry to prepare ferrous sulfate and ferric ion-containing polymers from waste sulfuric acid solutions have limited functionality and cannot simultaneously meet the needs of preparing ferrous sulfate and ferric ion-containing polymers. This results in a limited range of finished products that cannot meet the diverse needs of the market, which is an urgent problem that needs to be solved at present.

[0005] Therefore, how to solve the above-mentioned problems is the primary issue that this invention aims to address. Summary of the Invention

[0006] The main objective of this invention is to provide a system for preparing ferrous sulfate or iron-containing inorganic polymers from waste sulfuric acid. The system involves reacting a waste sulfuric acid solution with an iron source in a first reaction tank to obtain a ferrous sulfate solution. The ferrous sulfate solution is then concentrated and crystallized to obtain ferrous sulfate crystals, depending on production requirements. Alternatively, it can react with an acidic solvent and an oxidant in a second reaction tank to obtain a polyferric sulfate solution, which is then concentrated and crystallized to obtain polyferric sulfate crystals. This system diversifies the types of finished products obtained from waste sulfuric acid solution treatment, meets market demands, conforms to the requirements of a circular economy and green environmental protection, and enhances the economic value of waste sulfuric acid.

[0007] To achieve the aforementioned objectives, the present invention provides a system for preparing ferrous sulfate and iron-containing inorganic polymers using waste sulfuric acid, comprising:

[0008] A storage tank is used to store and supply a waste sulfuric acid solution;

[0009] A first reaction tank is connected to the storage tank and is used to receive the waste sulfuric acid solution and react it with an iron source to obtain a ferrous sulfate solution;

[0010] A filtration device, connected to the first reaction tank, is used to filter the ferrous sulfate solution;

[0011] A second reaction tank is connected to the filtration device to receive the filtered ferrous sulfate solution. An acid supply tank and an oxidant supply device are respectively connected to the second reaction tank to quantitatively add acidic solvent and oxidant to the second reaction tank. The ferrous sulfate solution reacts with the acidic solvent and oxidant to produce a polymerized ferrous sulfate solution.

[0012] An evaporator, connected to the filtration device and the second reaction tank, is used to evaporate and concentrate the ferrous sulfate solution or the polyferric sulfate solution into a saturated ferrous sulfate solution or a saturated polyferric sulfate solution.

[0013] A first crystallizer, connected to the evaporator, is used to cool the saturated solution of ferrous sulfate or the saturated solution of polyferric sulfate to precipitate ferrous sulfate crystals or polyferric sulfate crystals.

[0014] One of the auxiliary technical means derived from the above-mentioned necessary technical means also includes a third reaction tank and an aluminum compound feeding tank. The third reaction tank is connected to the second reaction tank and is used to receive the polyferric sulfate solution. The aluminum compound feeding tank is connected to the third reaction tank and quantitatively adds an aluminum-containing compound to the third reaction tank to react with the polyferric sulfate solution to obtain a polyaluminum ferric sulfate solution.

[0015] One of the auxiliary technical means derived from the aforementioned necessary technical means also includes a third reaction tank and an aluminum compound supply tank. The third reaction tank is connected to the filter device to receive the ferrous sulfate solution. The third reaction tank is also connected to the acid supply tank and the oxidant supply device. First, the acid supply tank and the oxidant supply device quantitatively add acidic solvent and oxidant to the third reaction tank. The ferrous sulfate solution reacts with the acidic solvent and oxidant to obtain a polyferric sulfate solution. Then, the aluminum compound supply tank quantitatively adds an aluminum-containing compound to the third reaction tank to react with the polyferric sulfate solution to obtain a polyaluminum ferric sulfate solution.

[0016] One of the auxiliary technical means derived from the above-mentioned necessary technical means also includes a second crystallizer and a drying and ripening device. The second crystallizer is connected to the third reaction tank, and the drying and ripening device is connected to the second crystallizer. The second crystallizer cools the polyaluminum ferric sulfate solution to precipitate polyaluminum ferric sulfate crystals, and the drying and ripening device dries and ripens the polyaluminum ferric sulfate crystals at a temperature of 50°C to 75°C.

[0017] In one of the auxiliary technical means derived from the aforementioned necessary technical means, the iron source is one or more of iron powder, iron filings, and iron materials; depending on the chemical dosage of the iron source reacting with the waste sulfuric acid solution, 1% to 6% of the iron source by weight of the chemical dosage is added to the first reaction tank, the reaction temperature of the first reaction tank is controlled at above 55°C, the stirring speed is 30 rpm to 80 rpm, and the stirring is carried out at a constant temperature and speed for at least 30 minutes to decompose the hydrogen peroxide contained in the waste sulfuric acid solution.

[0018] In one of the auxiliary technical means derived from the above-mentioned necessary technical means, the first reaction tank controls the reaction temperature of the iron source and the waste sulfuric acid solution to be 60℃~130℃, the stirring speed to be 30rpm~80rpm, and the constant temperature and speed stirring reaction to be 6 hours~12 hours, so that the iron source and the waste sulfuric acid solution react to obtain ferrous sulfate solution.

[0019] In one of the auxiliary technical means derived from the aforementioned necessary technical means, the acid solvent provided by the acid supply tank is a sulfuric acid solution with a concentration of 25% to 70%; the oxidant provided by the oxidant supply device includes one of sodium nitrite, potassium chlorate, sodium chlorate, hydrogen peroxide, nitric acid, and oxygen.

[0020] In one of the auxiliary technical means derived from the above-mentioned necessary technical means, the second reaction tank controls the polymerization reaction temperature to be 40℃~120℃ and the stirring speed to be 25rpm~75rpm. When the hydroxyl value of the reaction solution reaches 40~50 and the pH value is 1~5, the addition of oxidant and acidic solvent is stopped.

[0021] In one of the auxiliary technical means derived from the aforementioned necessary technical means, the aluminum compound supplied by the aluminum compound feeding tank is an aluminum sulfate solution or an alkaline aluminum solution alkalized by an alkalizing agent. The amount of aluminum compound added is based on the molar ratio of aluminum to iron, with the aluminum-iron molar ratio being 1~4:6~9. The third reaction tank controls the reaction temperature at 40℃~80℃ and the stirring speed at 25rpm~75rpm, maintaining constant temperature and speed stirring until the pH value of the reaction solution is 2~6, at which point the addition of the aluminum compound is stopped.

[0022] One of the auxiliary technical means derived from the aforementioned necessary technical means also includes a dehydration device and a drying device. The dehydration device is connected to the first crystallizer. The dehydration device is also connected to the first reaction tank via a first reflux pipe and to the second reaction tank via a second reflux pipe. The dehydration device separates the crystals from the mother liquor and returns the mother liquor to the first reaction tank or the second reaction tank. The drying device is connected to the dehydration device and is used to dry the crystals.

[0023] The aforementioned objectives and advantages of the present invention can be readily understood from the following detailed description of the selected embodiments and the accompanying drawings. Simple Explanation of the Diagram

[0024] Figure 1 is a schematic diagram of the system provided in the first embodiment of the present invention. Figure 2 is a schematic diagram of the system provided in the second embodiment of the present invention. Figure 3 is a schematic diagram of the system provided in the third embodiment of the present invention. Implementation

[0025] Please refer to Figure 1. Figure 1 shows a system for preparing ferrous sulfate and ferric ion-containing inorganic polymers using waste sulfuric acid according to a preferred embodiment of the present invention. The system includes a storage tank 100, a first reaction tank 110, a filter device 120, a second reaction tank 200, an acid supply tank 210, an oxidant supply device 220, an evaporator 300, and a first crystallizer 310.

[0026] The storage tank 100 is connected to the first reaction tank 110 and is used to store and quantitatively supply a waste sulfuric acid solution to the first reaction tank 110. The waste sulfuric acid solution is a sulfuric acid solution with a sulfuric acid content of less than 70%, which is a mixture of waste sulfuric acid from the semiconductor industry and water.

[0027] An iron source, which can be one or more of iron powder, iron filings, and iron materials, is also metered and added into the first reaction tank 110. The iron source is added according to the chemical dosage required for its reaction with the waste sulfuric acid solution. If the waste sulfuric acid solution contains hydrogen peroxide (H2O2), an iron source of 1% to 6% by weight of the chemical dosage is added first. The reaction temperature in the first reaction tank 110 is controlled at above 55°C, and the stirring speed is 30 rpm to 80 rpm. The stirring is carried out at a constant temperature and speed for at least 30 minutes. The hydrogen peroxide contained in the waste sulfuric acid solution is decomposed by the exothermic reaction and the heating of the system. At this time, the chemical reaction occurring in the first reaction tank 110 is: 2H2O2 → 2H2O + O2↑, avoiding sudden boiling during the reaction process and potential production safety hazards.

[0028] After removing hydrogen peroxide from the waste sulfuric acid solution, the remaining iron source is added. The first reaction tank 110 controls the reaction temperature between the iron source and the waste sulfuric acid solution to be 60℃~130℃, and the stirring speed to be 30rpm~80rpm. The reaction is carried out at a constant temperature and speed for 6~12 hours to ensure complete reaction of the iron source and the waste sulfuric acid solution, yielding a ferrous sulfate solution. This ferrous sulfate solution is then filtered through a filter 120 to remove insoluble impurities, reducing their impact on subsequent chemical reactions and thus lowering the yield.

[0029] In a first embodiment of the present invention, the filtration device 120 is connected to both the second reaction tank 200 and the evaporator 300. A diversion valve (not shown) or other known prior art controls the flow of the filtered ferrous sulfate solution to the second reaction tank 200 or the evaporator 300, allowing production operators to deliver the filtered ferrous sulfate solution to either the second reaction tank 200 or the evaporator 300 according to product requirements. If ferrous sulfate crystals are to be obtained, the ferrous sulfate solution is directly evaporated and concentrated in the evaporator 300 at a temperature of 50°C to 70°C to form a saturated ferrous sulfate solution. This solution is then cooled in the first crystallizer 310 to precipitate ferrous sulfate crystals. The first crystallizer 310 is preferably a continuous crystallizer to improve crystallization efficiency and reduce system energy consumption.

[0030] To obtain polyferric sulfate crystals, a ferrous sulfate solution is fed into the second reaction tank 200. An acidic solvent is added to the second reaction tank 200 by an acidic supply tank 210, and an oxidant is added to the second reaction tank 200 by an oxidant supply device 220. The acidic solvent, containing sulfuric acid with a concentration of 70%–85%, is prepared by mixing concentrated sulfuric acid and water in a specific ratio; alternatively, it can be a waste sulfuric acid solution within this concentration range. The oxidant includes sodium nitrite (NaNO4), sodium chlorate (NaClO3), potassium chlorate (KClO3), hydrogen peroxide (H2O2), nitric acid (HNO3), and oxygen (O2). The second reaction tank 200 controls the polymerization reaction temperature at 40°C–120°C and the stirring speed at 25 rpm–75 rpm. When the hydroxyl value of the reaction solution reaches 40–50 and the pH value is 1–5, the polymerization reaction is complete, and the addition of oxidant and acidic solvent is stopped. The hydroxyl value was calculated by titrating the reaction solution sample with potassium hydroxide (KOH), while the pH value was monitored using a pH meter. After the polymerization reaction was completed, the polyferric sulfate solution was evaporated and concentrated in the evaporator 300 at a temperature of 50℃~70℃ to become a saturated polyferric sulfate solution. Then, it was cooled in the first crystallizer 310 to precipitate polyferric sulfate crystals from the saturated polyferric sulfate solution.

[0031] The first embodiment of the present invention further includes a dehydration device 320 and a drying device 330. The dehydration device 320 is connected to the first crystallizer 310 and is used to dehydrate the ferrous sulfate crystal solution followed by the polyferric sulfate crystal solution. The separated ferrous sulfate mother liquor is returned to the first reaction tank 110, or the separated polyferric sulfate mother liquor is returned to the second reaction tank 200 for the next round of reaction recovery, reducing waste. The separated ferrous sulfate crystals or polyferric sulfate crystals are heated by the drying device 330 to remove excess water. The drying device 330 obtains ferrous sulfate crystals containing different amounts of water of crystallization by controlling the drying temperature. The drying temperature for heptahydrate ferrous sulfate crystals is 40°C to 50°C, the drying temperature for trihydrate ferrous sulfate crystals is 65°C to 75°C, the drying temperature for monohydrate ferrous sulfate crystals is 80°C to 123°C, and the drying temperature for anhydrous ferrous sulfate is 156°C or higher. The drying temperature for polyferric sulfate crystals is 60℃~80℃.

[0032] As shown in Figure *, this is a second embodiment of the present invention, which differs from the first embodiment in that it further includes a third reaction tank 400 and an aluminum compound supply tank 410. The third reaction tank 400 is connected to the second reaction tank 200 and is used to receive the polyferric sulfate solution. The aluminum compound supply tank is connected to the third reaction tank 400, and the aluminum compound is added quantitatively and in batches to the third reaction tank 400 to react with the polyferric sulfate solution. The aluminum compound is an aluminum sulfate solution or a basic aluminum solution alkalized with an alkalizing agent. Specifically, the form of aluminum addition depends on the required basicity; generally, an aluminum sulfate solution is added. If a higher basicity is required in the final product, a basic aluminum solution alkalized with an alkalizing agent is added. The amount of aluminum compound added is based on the molar ratio of aluminum to iron, with the aluminum-iron molar ratio being 1~4:6~9. The third reaction tank 400 controls the reaction temperature at 40℃~80℃ and the stirring speed at 25rpm~75rpm. The stirring is carried out at a constant temperature and speed until the pH value of the reaction solution is 2~6. Then, the addition of aluminum compound is stopped, and polyaluminum ferric sulfate solution is obtained.

[0033] The third reaction tank 400 is also connected to a second crystallizer 420, which in turn is connected to a drying and ripening device 430. The polyaluminum ferric sulfate solution is transported from the third reaction tank 400 to the second crystallizer 420, where it is cooled to precipitate polyaluminum ferric sulfate crystals. These crystals are then dried and ripened in the drying and ripening device 430 at a temperature of 50°C to 75°C. Finally, according to market demand, the polyaluminum ferric sulfate crystals can be pulverized into the required particle size using a pulverizing device and packaged as a finished product for sale.

[0034] The second embodiment of the present invention adds a branch system for preparing polyaluminum ferric sulfate. When polyaluminum ferric sulfate is prepared in the third reaction tank 400, polyferric sulfate can also be prepared simultaneously in the second reaction tank 200, or ferrous sulfate can be prepared simultaneously in the first reaction tank 110, so as to realize the simultaneous production of multiple products, increase the variety of products after waste sulfuric acid is recycled and treated, and meet the diversified market demand.

[0035] As shown in Figure 3, this is a third embodiment of the present invention. The difference between this third embodiment and the second embodiment is that the third reaction tank 400 is connected to the filter device 120 and directly receives the ferrous sulfate solution from the filter device 120. The third reaction tank 400 is also connected to the acid supply tank 210 and the oxidant supply device 220. First, the acid supply tank 210 and the oxidant supply device 220 quantitatively add acidic solvent and oxidant to the third reaction tank 400. The ferrous sulfate solution reacts with the acidic solvent and oxidant to obtain a polyferric sulfate solution. Then, the aluminum compound supply tank quantitatively adds an aluminum compound to the third reaction tank 400, and the polyferric sulfate solution reacts with the aluminum compound to obtain a polyaluminum ferric sulfate solution.

[0036] The third implementation involves receiving ferrous sulfate reaction solution in the third reaction tank 400 to form a system branch. The amount of ferrous sulfate solution required to prepare different finished products can be reasonably allocated according to the production plan, which improves production flexibility, improves waste sulfuric acid treatment efficiency, and generates different finished products simultaneously, thereby improving production efficiency requirements.

[0037] Based on the above three embodiments of the present invention, further details are provided in conjunction with the following examples.

[0038] Example 1

[0039] (I) Preparation system: The first embodiment shown in Figure 1

[0040] (II) Reactants and Reagents

[0041] Waste sulfuric acid solution: Waste sulfuric acid from the semiconductor industry containing approximately 4% hydrogen peroxide (H2O2), with a sulfuric acid content of 80%, is diluted with water to a sulfuric acid content of 70%.

[0042] Iron source: iron filings

[0043] Acidic solvent: 25% sulfuric acid solution

[0044] Oxidizing agent: nitric acid

[0045] (III) Pre-processing steps:

[0046] First, a measured amount of waste sulfuric acid solution is added to the first reaction tank 110. Based on the stoichiometric ratio of the iron source to the waste sulfuric acid solution, 4% by weight of the stoichiometric ratio of the iron source is added. The reaction temperature is controlled at 65°C, and the stirring speed is 40 rpm. After stirring at a constant temperature and speed for 38 minutes, the residual hydrogen peroxide in the reaction solution is tested with hydrogen peroxide test paper. If the hydrogen peroxide test paper cannot detect it, it is determined that the hydrogen peroxide has been completely decomposed.

[0047] Then, the remaining iron source was added sequentially to the first reaction tank 110. The reaction temperature was controlled at 70℃, and the stirring speed at 45 rpm. The reaction was carried out at a constant temperature and speed for 8 hours. The chemical reaction occurring in the first reaction tank 110 was: H2SO4 + Fe → FeSO4 + H2↑. The reaction was considered complete when the pH of the reaction solution was 3, yielding a ferrous sulfate solution. After filtering to remove insoluble impurities, the ferrous sulfate solution was obtained.

[0048] (iv) Preparation of ferrous sulfate:

[0049] First, the ferrous sulfate solution obtained after pretreatment is concentrated into a saturated solution by evaporator 300, and then cooled in the first crystallizer 310 to precipitate ferrous sulfate crystals.

[0050] Then, the dehydration device 320 separates the ferrous sulfate crystals from the mother liquor, and returns the mother liquor to the first reaction tank 110 via the first reflux pipe;

[0051] Finally, the ferrous sulfate crystals were dried in the drying apparatus 330 at a temperature of 40°C to obtain ferrous sulfate heptahydrate.

[0052] (V) Preparation of Polyferric Sulfate:

[0053] The ferrous sulfate solution obtained after pretreatment is transferred to the second reaction tank 200, and acidic solvent and oxidant are added. The reaction temperature is controlled at 80℃ and the stirring speed is 30 rpm. The chemical reaction occurring in the second reaction tank 200 is: FeSO4 + HNO3 → Fe(OH)SO4 + NO2↑. When the hydroxyl value of the reaction solution reaches 45 and the pH value reaches 2, the reaction is considered complete, and the addition of oxidant and acidic solvent is stopped.

[0054] Next, the polyferric sulfate solution is evaporated and concentrated in evaporator 300 at 60°C to become a saturated polyferric sulfate solution, and then cooled in the first crystallizer 310 to precipitate polyferric sulfate crystals;

[0055] Then, the dehydration device 320 separates the polyferric sulfate from the mother liquor and returns the mother liquor to the second reaction tank 200 via the first reflux pipe;

[0056] Finally, the drying device 330 dries the product at a temperature of 80°C to obtain polyferric sulfate crystals.

[0057] Example 2

[0058] (a) Preparation system: The second embodiment shown in Figure 2

[0059] (II) Reactants and Reagents

[0060] Waste sulfuric acid solution: Waste sulfuric acid from the semiconductor industry containing approximately 3.5% hydrogen peroxide (H2O2), with a sulfuric acid content of 70%.

[0061] Iron source: iron filings

[0062] Acidic solvent: 60% sulfuric acid solution

[0063] Oxidizing agent: Potassium chlorate

[0064] Aluminum-containing compounds: 1.5M aluminum sulfate solution

[0065] (III) Pre-processing steps;

[0066] First, a measured amount of waste sulfuric acid solution is added to the first reaction tank 110. Based on the stoichiometric ratio of the iron source to the waste sulfuric acid solution, 2% by weight of the stoichiometric ratio of the iron source is added. The reaction temperature is controlled at 60°C, and the stirring speed is 50 rpm. After stirring at a constant temperature and speed for 45 minutes, the residual hydrogen peroxide in the reaction solution is tested with hydrogen peroxide test paper. If the hydrogen peroxide test paper cannot detect it, it is determined that the hydrogen peroxide has been completely decomposed.

[0067] Then, the remaining iron source in the chemical dose is added to the first reaction tank 110 in sequence. The reaction temperature is controlled at 60℃ and the stirring speed is 65rpm. The reaction is carried out at a constant temperature and speed for 10 hours. The chemical reaction that occurs in the first reaction tank 110 is: H2SO4+Fe→FeSO4+H2↑. The reaction is judged to be complete when the pH value of the reaction solution is 2, and ferrous sulfate solution is obtained. Then, the ferrous sulfate solution is filtered to remove insoluble impurities, and the filtered ferrous sulfate solution is obtained.

[0068] (iv) Preparation of ferrous sulfate:

[0069] Next, the filtered ferrous sulfate solution is evaporated and concentrated at 60°C using the evaporator 300 to obtain a saturated ferrous sulfate solution;

[0070] Then, the saturated ferrous sulfate solution is cooled down in the first crystallizer 310 to precipitate ferrous sulfate crystals; the dehydration device 320 separates the ferrous sulfate crystals from the mother liquor, and the mother liquor is returned to the first reaction tank 110 through the first reflux pipe;

[0071] Finally, the ferrous sulfate crystals were dried in the drying apparatus 330 at a temperature of 70°C to obtain ferrous sulfate trihydrate.

[0072] (V) Preparation of Polyferric Sulfate:

[0073] Alternatively, the ferrous sulfate solution filtered by the filter device 120 is transported to the second reaction tank 200, and acidic solvent and oxidant are added. The reaction temperature is controlled at 70℃ and the stirring speed is 60rpm. The chemical reaction occurring in the second reaction tank 200 is: 6FeSO4+KClO3+3(1-n / 2)H2SO4→3[Fe2(OH)n(SO4)3-n / 2]+3(1-n)H2O+KCl, n=0.5~1. When the hydroxyl value of the reaction solution reaches 50 and the pH value is 3, the reaction is considered complete and the addition of oxidant and acidic solvent is stopped.

[0074] Next, the polyferric sulfate solution is evaporated and concentrated in evaporator 300 at 50°C to become a saturated polyferric sulfate solution, and then cooled in the first crystallizer 310 to precipitate polyferric sulfate crystals.

[0075] Then, the dehydration device 320 separates the polyferric sulfate from the mother liquor and returns the mother liquor to the second reaction tank 200 via the first reflux pipe.

[0076] Finally, the drying device 330 dries the product at a temperature of 70°C to obtain polyferric sulfate crystals.

[0077] (vi) Preparation of polyaluminum ferric sulfate:

[0078] The second reaction tank 200 can also transport the polyferric sulfate solution prepared above to the third reaction tank 400; aluminum compound feeding tank 410 adds aluminum sulfate solution at an aluminum-iron molar ratio of 1:6, controls the reaction temperature at 70℃, and the stirring speed at 55rpm, and stirs at a constant temperature and speed until the pH value of the reaction solution is 3, then stops adding aluminum-containing compounds, and obtains polyaluminum ferric sulfate solution;

[0079] Then, the third reaction tank 400 conveys the polyaluminum ferric sulfate solution to the second crystallizer 420, where the second crystallizer 420 cools the polyaluminum ferric sulfate solution to precipitate polyaluminum ferric sulfate crystals;

[0080] Finally, the drying and aging device 430 dries the polyaluminum ferric sulfate crystals at 60°C for 5 hours to age them. The aged polyaluminum ferric sulfate crystals are then crushed into the required particle size according to market demand.

[0081] Example 3

[0082] (a) Preparation system: The third embodiment shown in Figure 3.

[0083] (II) Reactants and Reagents

[0084] Waste sulfuric acid solution: Waste sulfuric acid from the semiconductor industry containing approximately 6% hydrogen peroxide (H2O2), with a sulfuric acid content of 65%.

[0085] Iron source: iron powder

[0086] Acidic solvent: 30% sulfuric acid solution

[0087] Oxidizing agent: Hydrogen peroxide

[0088] Aluminum-containing compounds: 2M aluminum sulfate solution

[0089] (III) Pre-processing steps:

[0090] First, add a measured amount of waste sulfuric acid solution to the first reaction tank 110. Then, according to the stoichiometric ratio of the iron source to the waste sulfuric acid solution, add 6% iron source by weight, controlling the reaction temperature at 70℃ and the stirring speed at 60 rpm. After stirring at a constant temperature and speed for 50 minutes, test the residual hydrogen peroxide in the reaction solution with hydrogen peroxide test paper. If the hydrogen peroxide test paper cannot detect it, it is determined that the hydrogen peroxide has been completely decomposed.

[0091] Then, the remaining iron source in the chemical dose is added to the first reaction tank 110 in sequence. The reaction temperature is controlled at 100℃ and the stirring speed is 70 rpm. The reaction is carried out at a constant temperature and speed for 12 hours. The chemical reaction that occurs in the first reaction tank 110 is: H2SO4 + Fe → FeSO4 + H2↑. The reaction is considered complete when the pH value of the reaction solution is 3. Ferrous sulfate solution is obtained. The ferrous sulfate solution is filtered to remove insoluble impurities.

[0092] (iv) Preparation of ferrous sulfate:

[0093] Next, the ferrous sulfate solution is evaporated and concentrated in the evaporator 300 at 55°C to obtain a saturated ferrous sulfate solution; the saturated solution is cooled in the first crystallizer 310 to precipitate ferrous sulfate crystals. The dehydration device 320 separates the ferrous sulfate crystals from the mother liquor, and the mother liquor is returned to the first reaction tank 110 through the first reflux pipe; then the drying device 330 dries the ferrous sulfate crystals at a temperature of 85°C to obtain hydrated ferrous sulfate.

[0094] (V) Preparation of Polyferric Sulfate:

[0095] Alternatively, ferrous sulfate solution can be transferred to the second reaction tank 200, and acidic solvent and oxidant can be added. The reaction temperature can be controlled at 85℃ and the stirring speed at 75rpm. The chemical reaction occurring in the second reaction tank 200 is: 2FeSO4 + H2O2 + (1-n / 2)H2SO4 → Fe2(OH)n(SO4)3-n / 2] + (2-n)H2O, n<2. When the hydroxyl value of the reaction solution reaches 40 and the pH value is 4, the reaction is considered complete and the addition of oxidant and acidic solvent is stopped.

[0096] Then, the polyferric sulfate solution is evaporated and concentrated in evaporator 300 at 50°C to become a saturated polyferric sulfate solution. It is then cooled in the first crystallizer 310 to precipitate polyferric sulfate crystals. The dehydration device 320 separates the polyferric sulfate from the mother liquor, and the mother liquor is returned to the second reaction tank 200 via the first reflux pipe. Finally, the drying device 330 dries the solution at a temperature of 65°C to obtain polyferric sulfate crystals.

[0097] (vi) Preparation of polyaluminum ferric sulfate:

[0098] Alternatively, the filtered ferrous sulfate solution can be transported to the third reaction tank 400, and acidic solvent and oxidant can be added. The reaction temperature can be controlled at 85℃ and the stirring speed at 75rpm. The chemical reaction occurring in the third reaction tank 400 is: 2FeSO4 + H2O2 + (1-n / 2)H2SO4 → Fe2(OH)n(SO4)3-n / 2] + (2-n)H2O, n<2. When the hydroxyl value of the reaction solution reaches 40 and the pH value is 4, the reaction is considered complete and the addition of oxidant and acidic solvent is stopped.

[0099] Next, aluminum sulfate solution is added to the third reaction tank 400 at an aluminum-iron molar ratio of 4:9. The reaction temperature is controlled at 80°C and the stirring speed is 70 rpm. The mixture is stirred at a constant temperature and speed until the pH of the reaction solution is 6. Then, the addition of aluminum-containing compounds is stopped, and a polyaluminum ferric sulfate solution is obtained.

[0100] Then, the third reaction tank 400 conveys the polyaluminum ferric sulfate solution to the second crystallizer 420, where the second crystallizer 420 cools the polyaluminum ferric sulfate solution to precipitate polyaluminum ferric sulfate crystals;

[0101] Finally, the drying and aging device 430 dries the polyaluminum ferric sulfate crystals at 75°C for 6 hours to age them. The aged polyaluminum ferric sulfate crystals are then crushed into the required particle size according to market demand.

[0102] As can be seen from the above embodiments, the different embodiments of the system provided by the present invention use waste sulfuric acid solution as raw material to react and obtain different finished products.

[0103] In summary, the system for preparing ferrous sulfate or iron-containing polymers from waste sulfuric acid provided by this invention has the following technical advancements and advantages:

[0104] First, different compounds can be selectively prepared according to production needs, shortening the production process. The system provided by this invention utilizes the ferrous sulfate solution generated in the first reaction tank, which, after filtration, can be concentrated, cooled, and crystallized to obtain ferrous sulfate crystals. Alternatively, the ferrous sulfate solution can be reacted with an acidic solvent and an oxidant to obtain a polyferric sulfate solution, which can then be cooled and crystallized to obtain polyferric sulfate crystals. The polyferric sulfate solution can also be further reacted with an aluminum-containing compound to produce a polyaluminum ferric sulfate solution, which can then be cooled and crystallized to obtain polyaluminum ferric sulfate crystals. This system allows for the selection of different preparation system branches according to production needs, thereby satisfying the simultaneous preparation of different compounds and shortening the production process.

[0105] Secondly, it diversifies the types of finished products from waste sulfuric acid solution treatment to meet diverse market demands. By utilizing the commonalities of reactants and products between various reactions, and using ferrous sulfate solution as the base reaction solution, it achieves the effects of preparing ferrous sulfate crystals, reacting to prepare polyferric sulfate crystals or polyaluminum ferric sulfate crystals, thereby diversifying the types of finished products and meeting market demands.

[0106] Third, remove hydrogen peroxide from the waste sulfuric acid solution to avoid sudden boiling and safety accidents during the reaction.

[0107] Fourth, it meets the requirements of circular economy and energy conservation and carbon reduction; the present invention uses waste sulfuric acid solution produced by the semiconductor industry as a reaction raw material to convert waste sulfuric acid, which has a high pollution effect on the environment, into compounds that can be applied to other industries, thereby reducing the energy consumption of waste sulfuric acid treatment and meeting the requirements of circular economy and energy conservation and carbon reduction.

[0108] However, the above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Therefore, any changes in numerical values ​​or substitutions of equivalent elements should still fall within the scope of the present invention.

[0109] In conclusion, since this invention can clearly demonstrate to those skilled in the art that it can achieve the aforementioned objectives, it complies with the provisions of the Patent Law, and therefore an application is filed in accordance with the law.

[0110] 100: Storage slot 110: First Reaction Tank 120: Filtering device 200: Second Reaction Tank 210: Acid Supply Tank 220: Oxidant supply unit 300: Evaporator 310: First Crystallizer 320: Dehydration device 330: Drying device 400: Third Reaction Tank 410: Aluminum compound feeder 420: Second Crystallizer 430: Drying and maturation apparatus

Claims

1. A system for preparing ferrous sulfate and iron-containing inorganic polymers from waste sulfuric acid, comprising: a storage tank for storing and supplying a waste sulfuric acid solution; a first reaction tank connected to the storage tank for receiving the waste sulfuric acid solution and reacting it with an iron source to obtain a ferrous sulfate solution; a filtration device connected to the first reaction tank for filtering the ferrous sulfate solution; a second reaction tank connected to the filtration device for receiving the filtered ferrous sulfate solution; an acid supply tank and an oxidant supply device respectively connected to the second reaction tank for quantitatively adding an acidic solvent and an oxidant to the second reaction tank, wherein the ferrous sulfate solution reacts with the acidic solvent and the oxidant to polymerize and obtain a polyferric sulfate solution; and an evaporator connected to the filtration device and the second reaction tank for evaporating and concentrating the ferrous sulfate solution or the polyferric sulfate solution into a saturated ferrous sulfate solution or a saturated polyferric sulfate solution. A first crystallizer, connected to the evaporator, is used to cool the saturated ferrous sulfate solution or the saturated polyferric sulfate solution to precipitate ferrous sulfate crystals or polyferric sulfate crystals; It also includes a third reaction tank and an aluminum compound feeding tank, the third reaction tank being connected to the second reaction tank to receive the polyferric sulfate solution; the aluminum compound feeding tank being connected to the third reaction tank, and a quantitative amount of aluminum-containing compound is added to the third reaction tank to react with the polyferric sulfate solution to obtain a polyaluminum ferric sulfate solution.

2. A system for preparing ferrous sulfate and iron-containing inorganic polymers from waste sulfuric acid, comprising: a storage tank for storing and supplying a waste sulfuric acid solution; a first reaction tank connected to the storage tank for receiving the waste sulfuric acid solution and reacting it with an iron source to obtain a ferrous sulfate solution; a filtration device connected to the first reaction tank for filtering the ferrous sulfate solution; a second reaction tank connected to the filtration device for receiving the filtered ferrous sulfate solution; an acid supply tank and an oxidant supply device respectively connected to the second reaction tank for quantitatively adding an acidic solvent and an oxidant to the second reaction tank, wherein the ferrous sulfate solution reacts with the acidic solvent and the oxidant to polymerize and obtain a polyferric sulfate solution; and an evaporator connected to the filtration device and the second reaction tank for evaporating and concentrating the ferrous sulfate solution or the polyferric sulfate solution into a saturated ferrous sulfate solution or a saturated polyferric sulfate solution. A first crystallizer, connected to the evaporator, is used to cool the saturated ferrous sulfate solution or the saturated polyferric sulfate solution to precipitate ferrous sulfate crystals or polyferric sulfate crystals. The system also includes a third reaction tank and an aluminum compound feeding tank. The third reaction tank is connected to the filtration device to receive the ferrous sulfate solution. The third reaction tank is also connected to an acid supply tank and an oxidant supply device, through which acidic solvents and oxidants are quantitatively added to the third reaction tank. The ferrous sulfate solution polymerizes with the acidic solvents and oxidants to obtain a polyferric sulfate solution. The aluminum compound feeding tank is connected to the third reaction tank to quantitatively add an aluminum-containing compound to the third reaction tank to react with the polyferric sulfate solution, obtaining a polyaluminum ferric sulfate solution.

3. The system for preparing ferrous sulfate and iron-containing inorganic polymers from waste sulfuric acid as described in claim 1 or claim 2, wherein, It also includes a second crystallizer and a drying and ripening device. The second crystallizer is connected to the third reaction tank, and the drying and ripening device is connected to the second crystallizer. The second crystallizer cools the polyaluminum ferric sulfate solution to precipitate polyaluminum ferric sulfate crystals, and the drying and ripening device dries and ripens the polyaluminum ferric sulfate crystals at a temperature of 50°C to 75°C.

4. The system for preparing ferrous sulfate and iron-containing inorganic polymers from waste sulfuric acid as described in claim 1 or claim 2, wherein, The iron source is one or more of iron powder, iron filings, and iron materials. Depending on the chemical dosage of the iron source reacting with the waste sulfuric acid solution, 1% to 6% of the iron source by weight of the chemical dosage is added to the first reaction tank. The reaction temperature of the first reaction tank is controlled at above 55°C, and the stirring speed is 30 rpm to 80 rpm. The mixture is stirred at a constant temperature and speed for at least 30 minutes to decompose the hydrogen peroxide contained in the waste sulfuric acid solution.

5. The system for preparing ferrous sulfate and ferric ion-containing inorganic polymers from waste sulfuric acid as described in claim 1 or claim 2, wherein, The first reaction tank controls the reaction temperature of the iron source and the waste sulfuric acid solution to be 60℃~130℃, the stirring speed to be 30rpm~80rpm, and the reaction is carried out at a constant temperature and speed for 6 hours~12 hours, so that the iron source and the waste sulfuric acid solution react to obtain ferrous sulfate solution.

6. The system for preparing ferrous sulfate and iron-containing inorganic polymers from waste sulfuric acid as described in claim 1 or claim 2, wherein, The acid supply tank provides an acidic solvent solution with a concentration of 25% to 70% sulfuric acid; the oxidant supply device provides an oxidant including one of sodium nitrite, potassium chlorate, sodium chlorate, hydrogen peroxide, nitric acid, and oxygen.

7. The system for preparing ferrous sulfate and ferric ion-containing inorganic polymers from waste sulfuric acid as described in claim 1 or claim 2, wherein, The second reaction tank controls the polymerization reaction temperature to be 40℃~120℃ and the stirring speed to be 25rpm~75rpm. When the hydroxyl value of the reaction solution reaches 40~50 and the pH value is 1~5, the addition of oxidant and acidic solvent is stopped.

8. The system for preparing ferrous sulfate and ferric ion-containing inorganic polymers from waste sulfuric acid as described in claim 1 or claim 2, wherein, The aluminum compound supply tank provides aluminum sulfate solution or basic aluminum solution alkalized with an alkalizing agent. The amount of aluminum compound added is based on the molar ratio of aluminum to iron, with the aluminum-iron molar ratio being 1-4:6-9. The third reaction tank controls the reaction temperature at 40℃-80℃ and the stirring speed at 25rpm-75rpm. The stirring is carried out at a constant temperature and speed until the pH value of the reaction solution is 2-6, at which point the addition of aluminum compound is stopped.

9. The system for preparing ferrous sulfate and iron-containing inorganic polymers from waste sulfuric acid as described in claim 1 or claim 2, wherein, It also includes a dehydration device and a drying device. The dehydration device is connected to the first crystallizer. The dehydration device is also connected to the first reaction tank via a first reflux pipe and to the second reaction tank via a second reflux pipe. The dehydration device separates the crystals from the mother liquor and returns the mother liquor to the first reaction tank or the second reaction tank. The drying device is connected to the dehydration device and is used to dry the crystals.

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