Method and system for purifying ammonium sulfate

Abstract

The invention discloses a method and a system for purifying ammonium sulfate. The method comprises the steps of raw material pretreatment, oxidation impurity removal, precipitation impurity removal, carbon material adsorption, crystallization drying and the like for synergic impurity removal. In the raw material pretreatment, insoluble impurities are removed by using a gradient dissolution method and organic filter membrane filtration; the oxidation impurity removal adopts hydrogen peroxide to oxidize low-valence metal ions under the conditions of specific temperature and pH; a composite precipitator composed of organic phosphonate and magnesium salt is used for precipitation and impurity removal; carbon material adsorption adopts activated carbon with a specific specific surface area to adsorb organic matters; and the crystallization and drying are performed by controlling the temperature to perform evaporation concentration, gradient cooling crystallization and drying. The system and the method can effectively solve the problems of incomplete impurity removal, high cost, complex process and environmental pollution in the existing ammonium sulfate purification technology, have the advantages of efficient impurity removal, economical efficiency optimization of the whole process and environmental friendliness, and realize synergistic removal of heavy metal ions, organic matters and colloidal particles.

Description

Technical Field

[0001] This invention relates to the field of chemical product purification technology, specifically to an integrated system and process for deep purification and high-purity crystallization of ammonium sulfate solution based on multi-parameter synergistic control. Background Technology

[0002] Ammonium sulfate, as an important chemical product, has wide applications in agriculture and industry. In agriculture, it is a commonly used nitrogen fertilizer; in industry, it is used in pharmaceuticals, textiles, and other sectors. However, industrially produced ammonium sulfate often contains various impurities, such as heavy metal ions (iron ions, copper ions, etc.), sulfate ion impurities (such as sodium sulfate), and organic impurities. These impurities not only affect the quality of ammonium sulfate and limit its application in high-end fields, but may also pose potential hazards to the environment and users.

[0003] Current methods for purifying ammonium sulfate have several shortcomings. While recrystallization is relatively simple, it is energy-intensive, time-consuming, and ineffective at removing some impurities. Ion exchange has high impurity removal efficiency, but ion exchange resins are expensive, the regeneration process is complex, and it can easily cause secondary pollution. Precipitation can remove some impurities, but the selection and dosage of the precipitant are difficult to control precisely, and it can easily introduce new impurities. Therefore, developing an efficient, environmentally friendly, and low-cost method for purifying ammonium sulfate is of significant practical importance. Summary of the Invention

[0004] The purpose of this invention is to provide an efficient method and system for ammonium sulfate purification, so as to solve the problems of incomplete impurity removal, high cost, complex process and environmental pollution in existing ammonium sulfate purification technologies.

[0005] To solve the above technical problems, the present invention provides a method for purifying ammonium sulfate, comprising the following steps: (1) Raw material pretreatment: Crude ammonium sulfate and ultrapure water are mixed at a mass-volume ratio of 1:2.5-3.5, stirred at 40-60℃ for a period of time, and then filtered through an organic filter membrane to remove insoluble impurities; (2) Oxidation and impurity removal: Hydrogen peroxide is added to the pretreated solution to adjust the pH of the solution to 5-7, and the reaction is carried out at 40-60℃ for 0.5-1.5h to oxidize low-valence metal ions; (3) Precipitation and purification: Add a composite precipitant to the solution after oxidation and purification. The composite precipitant includes an organic phase and an inorganic phase. The organic phase is a mixture of PBTC and ATMP in a molar ratio of 1:0.6-0.8, and the inorganic phase is a magnesium salt. The magnesium ion concentration reaches 0.15-0.25 mol / L. React at 30-40℃ for 1-2 hours, and then filter to remove the precipitate. (4) Carbon material adsorption: Add activated carbon to the solution after precipitation and purification. The activated carbon has a BET specific surface area ≥1200 m². 2 / g, adsorb organic matter until the solution TOC≤50ppm, and control the solution pH to 6.5-7.5; (5) Crystallization and drying: evaporate and concentrate the adsorbed solution at 70-80℃, then carry out gradient cooling crystallization, control the crystallization temperature at 10-20℃, centrifuge and separate, and dry at 50-60℃ to obtain high-purity ammonium sulfate product.

[0006] Preferably, the stirring rate in step (1) is 800 r / min, and the pore size of the organic filter membrane is in the range of 0.1-0.5 μm.

[0007] Preferably, the magnesium salt in step (3) is a mixture of basic magnesium carbonate and magnesium sulfate.

[0008] Preferably, the gradient cooling crystallization in step (5) specifically involves starting at an initial temperature of 30-40℃ and cooling down to 10-20℃ at a cooling rate of 1-2℃ / min.

[0009] Preferably, the drying in step (5) is performed in a vacuum drying oven for 2-3 hours.

[0010] Preferably, the composite precipitant is regenerated after use, including: recovering magnesium salts from the mother liquor after precipitation and separation by electrodialysis, and regenerating the organophosphonate by resin adsorption.

[0011] The present invention also provides an ammonium sulfate purification system for implementing the above method, comprising: (1) a raw material pretreatment module configured to remove insoluble impurities by gradient dissolution and organic filter membrane filtration; (2) an oxidation and impurity removal module configured to oxidize low-valence metal ions by using hydrogen peroxide at 40-60℃ and pH 5-7; (3) a precipitation and impurity removal module configured to add a composite precipitant, wherein the composite precipitant comprises an organic phase PBTC and ATMP compounded at a molar ratio of 1:0.6-0.8 and an inorganic phase magnesium salt, and reacts at 30-40℃ for 1-2 hours; (4) a carbon material adsorption module configured to adsorb organic matter using activated carbon with a BET specific surface area ≥1200 m² / g, so that the TOC of the solution is ≤50ppm; (5) a crystallization and drying module configured to concentrate by evaporation at 70-80℃, crystallize by gradient cooling at 10-20℃, and dry at 50-60℃.

[0012] Preferably, the amount of hydrogen peroxide added in the oxidation and impurity removal module is 0.5-1.5% of the solution volume.

[0013] Preferably, the pH of the solution after treatment by the carbon material adsorption module is 6.5-7.5.

[0014] Furthermore, the system has a water resource recycling rate of ≥95% and reduces solid waste generation by 80%.

[0015] The technical solution of the present invention has the following beneficial effects: 1. High-efficiency impurity removal technology: A three-stage impurity interception system was constructed using an oxidation-precipitation-adsorption coupled process. By precisely controlling the reaction conditions, the synergistic removal of heavy metal ions, organic matter, and colloidal particles was achieved.

[0016] 2. Optimize the economic efficiency of the entire process: We developed our own composite precipitants and low-cost carbon-based adsorbents, which reduced reagent costs. By optimizing evaporation and concentration parameters using response surface methodology and combining them with an intelligent control system, we achieved a 25% reduction in energy consumption and a 30% decrease in overall equipment operating costs.

[0017] 3. Environmentally friendly process system: Using hydrogen peroxide as a green oxidant, the reaction process produces zero harmful byproducts. A system for the regeneration and recycling of precipitants and the resource utilization of adsorbent materials is established, reducing solid waste generation by 80% and achieving a water resource recycling rate of 95%, meeting the requirements of the ISO14001 environmental management system. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to specific examples.

[0019] The present invention provides a highly efficient method and system for purifying ammonium sulfate, the main technical solutions of which include: 1. Multi-step synergistic impurity removal technology Innovative design: Deep impurity removal is achieved through a three-step synergistic process of "oxidation-precipitation-adsorption", breaking through the limitations of traditional single methods.

[0020] Technical advantages: ① In the oxidation stage, a green oxidant (hydrogen peroxide) is used to convert low-valence metal ions (such as ferrous ions) into high-valence states, thereby enhancing the subsequent precipitation efficiency; ② During the precipitation stage, a self-made composite precipitant is used to simultaneously remove heavy metal ions (copper, lead) and sulfate impurities (sodium sulfate). ③ The adsorption stage utilizes activated carbon to adsorb organic matter, addressing the shortcomings of traditional methods in removing organic impurities.

[0021] 2. Development of self-made composite precipitant ① Organophosphonates chelate heavy metal ions, while magnesium salts remove sulfate impurities through co-precipitation reactions; ②Precisely control reaction conditions (30-40℃, 1-2 hours) to avoid introducing new impurities.

[0022] 3. Green and environmentally friendly process design ① Use hydrogen peroxide to replace highly polluting oxidants (such as chlorate) to reduce toxic byproducts; ②The precipitant and activated carbon can be recycled and regenerated, achieving resource recycling; ③ Optimize energy consumption through low-temperature evaporation and concentration (70-80℃) and cooling crystallization (10-20℃).

[0023] 4. Optimization of industrial production adaptability ① The pretreatment stage uses an organic filter membrane to quickly remove particulate matter, thereby improving the efficiency of subsequent reactions; ② Control the supersaturation and cooling rate during the crystallization stage to shorten the crystallization time; ③ The drying temperature (50-60℃) balances energy consumption and crystal quality.

[0024] Specifically: Purification methods: 1. Raw material pretreatment: A gradient dissolution method was used, in which crude ammonium sulfate (industrial grade, purity ≥92%) and ultrapure water (resistivity ≥18.2 MΩ·cm) were added at a solid-liquid ratio of 1:2.5-3.5 (w / v) to form a solution of a certain concentration. The solution was heated in a water bath at 40-60℃ using a magnetic stirrer and stirred at 800 r / min for 1 hour. Then, it was filtered while hot, and insoluble impurities such as silt and particulate matter were removed by filtration through an organic filter membrane.

[0025] 2. Oxidation for impurity removal: Add an appropriate amount of green oxidant (hydrogen peroxide as an example) to the pretreated solution. Control the solution temperature between 40 and 60°C, and adjust the pH value to 5 to 7. Under these conditions, low-valence metal impurity ions (such as ferrous ions) in the solution will be oxidized to high-valence states, thereby significantly improving their separation efficiency in subsequent steps.

[0026] 3. Precipitation and impurity removal: Construction of composite precipitation system Develop organic-inorganic hybrid precipitation systems, including: Organic phase: 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC, C7H) 11 O7P) and aminotrimethylenephosphonic acid (ATMP, C3H) 12 NO9P3) is compounded in a molar ratio of 1:0.6-0.8. Inorganic phase: Basic magnesium carbonate (4MgCO3·Mg(OH)2·5H2O) and magnesium sulfate (MgSO4·7H2O) form a buffer system (Mg²+ concentration 0.15-0.25mol / L).

[0027] Self-made composite precipitation preparation method 1. Organic phase compounding: PBTC (50% aqueous solution) and ATMP (50% aqueous solution) were mixed at a molar ratio of 1:0.7. A transparent chelate system is formed by aging at 60℃ for 30 minutes. 2. Inorganic phase preparation Basic magnesium carbonate and magnesium sulfate heptahydrate are mixed at a mass ratio of 1:1.2. Grind to D 90 ≤20μm 3. Composite process Organic and inorganic phases are mixed at a dry weight ratio of 1:2. Fluidized bed granulation (inlet air temperature 80℃) yields particles with a diameter of 0.5-1mm. A self-made composite precipitant is added, which reacts with heavy metal ions (such as copper ions and lead ions) and sulfate ion impurities (such as sodium sulfate) in the solution to form a sparingly soluble precipitate. The reaction temperature is controlled at 30-40℃, and the reaction time is 1-2 hours. The precipitate is then separated by filtration.

[0028] 4. Carbon material adsorption for impurity removal: Based on the physical adsorption and chemical complexation of surface functional groups (carboxyl groups, phenolic hydroxyl groups, etc.) of porous carbon-based adsorbent materials (such as activated carbon, BET specific surface area ≥1200 m² / g, micropore size distribution 0.5-2 nm), this invention preferably uses coconut shell activated carbon (specification: particle size 1-3 mm, methylene blue value ≥150 mg / g) to deeply purify ammonium sulfate solution (pH 6.5-7.5, residual TOC ≤50 ppm). 5. Crystallization and drying: For the ammonium sulfate solution after deep impurity removal, an evaporation and concentration operation is performed. A precise temperature control system maintains the concentration temperature range at 70–80°C. Once the solution reaches supersaturation, a gradient cooling program induces further supersaturation and initiates a cooling crystallization process, with the crystallization temperature range set at 10–20°C. A centrifugal separator is used to achieve solid-liquid separation, obtaining ammonium sulfate crystals. Finally, a constant-temperature drying oven is used for drying, with the drying temperature range set at 50–60°C, thus producing a high-purity ammonium sulfate product that meets industrial-grade standards.

[0029] Example 1: Experimental conditions: 1. Raw material pretreatment: 1000g of crude ammonium sulfate (92% purity), 3000mL of ultrapure water (solid-liquid ratio 1:3), stirred at 50℃ for 1h (800r / min), and filtered through a 0.2μm organic filter membrane.

[0030] 2. Oxidation for impurity removal: 30% hydrogen peroxide dosage: 1% (30 mL) of solution volume, temperature 50℃, pH=6, reaction time 1 h.

[0031] 3. Precipitation and impurity removal: Composite precipitant: PBTC and ATMP are mixed in a molar ratio of 1:0.7 (10g organic phase), and magnesium salts (basic magnesium carbonate + magnesium sulfate) are used to precipitate Mg²⁺. + Concentration 0.2 mol / L (25 g inorganic phase), react at 35℃ for 1.5 h, then filter.

[0032] 4. Adsorption by carbon materials: Activated carbon (BET specific surface area 1300m² / g) dosage 5g / L, adsorbed to TOC ≤30ppm.

[0033] 5. Crystallization and drying: Evaporation and concentration at 78℃, followed by gradient cooling (35℃→12℃, 1.5℃ / min) for crystallization, and vacuum drying at 58℃ for 2.5h.

[0034] Test data

[0035] Example 2: Experimental conditions: (Only the cooling rate was adjusted) Other parameters are the same as in Example 1, with temperature cooling rates of 1℃ / min, 1.5℃ / min, and 2℃ / min, respectively, and crystal particle size and purity are detected.

[0036] Test data

[0037] Example 3: pH Optimization Experiment for Oxidation and Impurity Removal Experimental conditions: (pH adjusted only during the oxidation phase) Other parameters are the same as in Example 1. During the oxidation stage, pH is controlled at 5, 6, and 7 respectively, and the Fe²⁺ oxidation efficiency is detected.

[0038] Test data:

[0039] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for purifying ammonium sulfate, characterized in that, The process includes the following steps: (1) Raw material pretreatment: Crude ammonium sulfate and ultrapure water are mixed at a mass-volume ratio of 1:2.5-3.5 and stirred at 40-60℃ for a period of time. Then, the mixture is filtered through an organic filter membrane to remove insoluble impurities; (2) Oxidation and impurity removal: Hydrogen peroxide is added to the pretreated solution to adjust the pH of the solution to 5-7. The solution is reacted at 40-60℃ for 0.5-1.5h to oxidize low-valence metal ions; (3) Precipitation and impurity removal: A composite precipitant is added to the oxidized and impurity-removed solution. The composite precipitant includes an organic phase and an inorganic phase. The organic phase is a mixture of PBTC and ATMP at a molar ratio of 1:0.6-0.8, and the inorganic phase is a magnesium salt. The magnesium ion concentration reaches 0.15-0.25mol / L. The mixture is reacted at 30-40℃ for 1-2h, and then the precipitate is removed by filtration; (4) Carbon material adsorption: Activated carbon is added to the precipitated and impurity-removed solution. The activated carbon has a BET specific surface area ≥1200 m². 2 / g, adsorb organic matter until the solution TOC≤50ppm, and control the solution pH to 6.5-7.5; (5) Crystallization and drying: evaporate and concentrate the adsorbed solution at 70-80℃, then carry out gradient cooling crystallization, control the crystallization temperature at 10-20℃, centrifuge and separate, and dry at 50-60℃ to obtain high-purity ammonium sulfate product.

2. The method according to claim 1, characterized in that, The stirring rate in step (1) is 800 r / min, and the pore size of the organic filter membrane is in the range of 0.1-0.5 μm.

3. The method according to claim 1, characterized in that, The magnesium salt in step (3) is a mixture of basic magnesium carbonate and magnesium sulfate.

4. The method according to claim 1, characterized in that, The gradient cooling crystallization in step (5) specifically involves starting at an initial temperature of 30-40℃ and cooling down to 10-20℃ at a rate of 1-2℃ / min.

5. The method according to claim 1, characterized in that, The drying in step (5) is performed in a vacuum drying oven for 2-3 hours.

6. The method according to claim 1, characterized in that, The composite precipitant is regenerated after use, including: recovering magnesium salts from the mother liquor after precipitation and separation through electrodialysis, and regenerating organophosphonates through resin adsorption.

7. An ammonium sulfate purification system for implementing the method according to any one of claims 1-6, characterized in that, include: (1) The raw material pretreatment module is configured to remove insoluble impurities by gradient dissolution and organic membrane filtration; (2) Oxidation and impurity removal module, configured to use hydrogen peroxide to oxidize low-valence metal ions at 40-60℃ and pH 5-7; (3) Precipitation and impurity removal module, configured to add a composite precipitant, the composite precipitant including organic phase PBTC and ATMP in a molar ratio of 1:0.6-0.8 and inorganic phase magnesium salt, reacting at 30-40℃ for 1-2 hours; (4) Carbon material adsorption module, configured to use activated carbon with BET specific surface area ≥1200 m² / g for organic matter adsorption, so that the solution TOC≤50ppm; (5) Crystallization and drying module, configured to concentrate by evaporation at 70-80℃, crystallize by gradient cooling at 10-20℃ and dry at 50-60℃.

8. The system according to claim 7, characterized in that, The amount of hydrogen peroxide added in the oxidation and impurity removal module is 0.5-1.5% of the solution volume.

9. The system according to claim 7, characterized in that, The pH of the solution after treatment by the carbon material adsorption module is 6.5-7.

5.

10. The system according to claim 7, characterized in that, The system achieves a water resource recycling rate of ≥95% and reduces solid waste generation by 80%.

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