A method for refining food-grade phosphoric acid by sulfuric acid

Abstract

The present invention relates to a method for producing phosphoric acid, in particular a method for producing food-grade phosphoric acid by sulfuric acid process. The method for extracting phosphoric acid is carried out by the following process steps according to the amount of sulfuric acid treatment, and the preferred process conditions are as follows: extraction: 2, crude desulfurization: 3, fine desulfurization: 4, washing: 5, back extraction: 6, pre-concentration: 7, final concentration: 8, arsenic and heavy metal removal: 9, stripping defluorination: 10, dechlorination and decolorization: 11, sensory analysis: sensory analysis according to the indicators in Table 1; 12, physical and chemical analysis: physical and chemical analysis according to the indicators in Table 2; 13, output food-grade phosphoric acid. In the present invention, the back-extracted acid is concentrated by vacuum concentration to a phosphoric acid concentration of about 85%. Arsenic and heavy metal removal: 85 acid reacts with phosphorus pentasulfide to generate hydrogen sulfide gas, and 85 acid is fully mixed with the gas in a closed arsenic and heavy metal removal device to obtain arsenic sulfide precipitate. Stripping defluorination: steam stripping defluorination is used. Dechlorination and decolorization: the 85 acid after arsenic and heavy metal removal is subjected to ozone aeration to remove chlorine and color, and the final product 85 acid is obtained.

Description

Technical Field

[0001] This invention relates to a method for manufacturing phosphoric acid, and more particularly to a method for refining food-grade phosphoric acid using the sulfuric acid process. Background Technology

[0002] Existing food-grade phosphoric acid production process: 1. Raw material selection: First, high-quality phosphate rock is selected as the main raw material for the production of food-grade phosphoric acid; the quality of phosphate rock directly affects the quality of the final product. 2. Crushing and grinding: The phosphate rock is crushed and ground to achieve a certain particle size in preparation for the subsequent acid leaching reaction; 3. Acidolysis reaction: In a reaction vessel, the ground phosphate rock is reacted with sulfuric acid to produce phosphoric acid and calcium sulfate. This step requires strict control of reaction conditions, such as temperature and pressure, to ensure the smooth progress of the reaction. 4. Filtration and separation: The phosphoric acid and calcium sulfate produced in the reaction are separated by filtration equipment; the resulting phosphoric acid solution needs further purification. 5. Purification treatment: Metal impurities in the phosphoric acid solution are removed and its purity is improved through precipitation, extraction, three-stage desulfurization, washing, back-extraction and other methods. 6. Concentration and De-arsenic and De-fluorination: The purified phosphoric acid solution is concentrated to a certain concentration. Subsequently, it undergoes de-arsenic and heavy metal removal via phosphorus pentasulfide, deep de-fluorination, and ozone decolorization and dechlorination to obtain suitable food-grade phosphoric acid.

[0003] Problems with existing technology:

[0004] The extraction rate is low, the extractant needs to be further concentrated, and the extractant loss is large.

[0005] Sulfate ions and metal ions have low purification efficiency, requiring the addition of chemical reagents, which introduces other impurities into subsequent processes.

[0006] The purpose of this invention is to provide a safe and processable method for refining food-grade phosphoric acid using the sulfuric acid process.

[0007] The objective of this invention is achieved by providing a method for refining food-grade phosphoric acid using a sulfuric acid process, characterized by extracting phosphoric acid through the following process steps, based on the amount of sulfuric acid processed. The preferred process conditions are: 1. Extraction: Add extractant into the extraction tower for extraction at 50℃, ratio 5:1, and vibration frequency 160-185. 2. Crude desulfurization: The amount of calcium carbonate added is 1.3 times the theoretical amount, the reaction temperature is 50℃, the ratio is 3-3.5:1, the reaction time is 60 minutes, the phosphoric acid extraction rate is 83%, and the purified phosphoric acid produced for one ton of phosphorus pentoxide consumes about 0.0161 tons of calcium carbonate.

[0008] 3. Fine desulfurization: The amount of barium carbonate added is 2-2.2 times the theoretical amount, the reaction temperature is 50℃, the ratio is 4:1, the reaction time is 60 minutes, and approximately 0.0056 tons of barium carbonate are consumed for every ton of purified phosphoric acid produced based on phosphorus pentoxide.

[0009] 4. Washing: Single-tower washing, temperature 50℃, ratio 18-20:1, vibration frequency 132Hz.

[0010] 5. Back-extraction: Temperature 60℃, double towers in series for back-extraction, ratio 5:1, vibration frequency 190Hz.

[0011] 6. Pre-concentration: Vacuum degree 0.085-0.09 MPa, temperature 80-90℃ 7. Final concentration: vacuum degree is 0.09 MPa, temperature is 90℃.

[0012] 8. Arsenic and heavy metal removal: The reaction temperature is 70℃, the amount of phosphorus pentasulfide added is 10-15 times the theoretical amount, and the reaction time is 0.5-1 hour.

[0013] 9. Stripping defluorination: The reaction temperature is 90-100℃. Each time, 13% water is added to bring the phosphoric acid content to 75%, and the mixture is repeatedly concentrated and stripped 6 times.

[0014] 10. Dechlorination and decolorization: Temperature 70℃, ozone concentration 110mg / L, flow rate 18L / min, dechlorination and decolorization time 60min; 11. Sensory analysis: Sensory analysis shall be conducted in accordance with the requirements of Table 1; 12. Physicochemical analysis: Physicochemical analysis shall be conducted in accordance with the requirements of Table 2; 13. Output food-grade phosphoric acid.

[0015] The extraction step in step 1 uses an extractant composed of TBP, a certain alcohol, and sulfonated kerosene.

[0016] The extractant components are in the following proportions or are in one of the following proportions: TBP: Isooctyl alcohol / n-octanol: sulfonated kerosene, volume ratio 5-8:1-3:1-2; TBP: Cyclohexanol: Sulfonated kerosene, in a volume ratio of 5-8:1-3:1-2; TBP: Isopropanol / Diisopropyl ether: Sulfonated kerosene, volume ratio 5-8:1-3:1-2.

[0017] The amount of phosphoric acid processed is either: a. Based on 10,000 tons of raw acid, the process time is 300 days, compared to a 5:1 ratio; the aqueous phase feed rate is 18.5 L / min, the organic phase feed rate is 92.6 L / min, and the total feed rate is 111.1 L / min.

[0018] b. Based on 12,000 tons of raw acid, the process time is 300 days, compared to a 5:1 ratio; the aqueous phase feed rate is 22.2 L / min, the organic phase feed rate is 111.1 L / min, and the total feed rate is 133.3 L / min.

[0019] The extraction tower adopts a dual-tower structure. The equipment parameters of the extraction tower are as follows: the height of the aqueous phase clarification section is 170 mm and the volume is 100 mL; the height of the mixing section is 1580 mm and the volume is 658 mL; the height of the oil phase clarification section is 165 mm and the volume is 275 mL. The extraction operation conditions are: temperature 50 ℃, phase ratio 4 - 5:1 (phase ratio refers to the volume ratio of oil phase to aqueous phase, the same below), vibration frequency 150 - 160 Hz (such a high frequency cannot be achieved in industry, it is basically 50 Hz), fixed oil phase feed rate of 30 mL / min, and aqueous phase feed rate of 5 - 6 mL / min.

[0020] The washing operation conditions are: temperature 50 ℃, ratio 18 - 20:1, vibration frequency 110 - 130 Hz (such a high frequency cannot be achieved industrially, so it is basically 50 Hz), fixed oil phase feed rate 30 mL / min, and aqueous phase feed rate 1.5 - 1.67 mL / min. The washing tower is the same as the extraction tower equipment.

[0021] The back-extraction equipment is a vibrating sieve plate tower, which can be divided into three sections: the bottom section is the aqueous phase clarification section, the middle section is the oil-water mixing section, and the top section is the oil phase clarification section. The parameters of the back-extraction tower are as follows: aqueous phase clarification section height 155 mm, capacity 66 mL; mixing section height 1370 mm, capacity 505 mL; oil phase clarification section height 150 mm, capacity 170 mL.

[0022] The operating conditions for the dual-tower tandem back-extraction were: temperature 60 ℃, phase ratio 5:1, vibration frequency 190 Hz, fixed oil phase feed rate 30 mL / min, and aqueous phase feed rate 6 mL / min.

[0023] Advantages of this invention: This process reduces operational steps and is highly automated, thereby reducing labor costs and production risks.

[0024] Through three desulfurization processes—extractant desulfurization, calcium carbonate crude desulfurization, and barium carbonate refined desulfurization—the sulfate ion content in the raw material can be reduced from 1% to 3% to below 0.01%, purifying the sulfate ions in the raw phosphoric acid to food-grade standards.

[0025] It can produce general-purpose industrial-grade phosphoric acid, which can be further processed into food-grade products with a total yield of over 60%, greatly improving the utilization efficiency of phosphate rock resources.

[0026] The present invention will be further described below with reference to the accompanying drawings of the embodiments: Attached Figure Description

[0027] Figure 1 This is a process flow diagram of an embodiment of the present invention. Detailed Implementation

[0028] like Figure 1 As shown, a method for refining food-grade phosphoric acid using the sulfuric acid process is characterized by extracting phosphoric acid through the following process steps, based on the amount of sulfuric acid processed. The preferred process conditions are: 1. Extraction: Add extractant into the extraction tower for extraction at 50℃, ratio 5:1, and vibration frequency 160-185. 2. Crude desulfurization: The amount of calcium carbonate added is 1.3 times the theoretical amount, the reaction temperature is 50℃, the ratio is 3-3.5:1, the reaction time is 60 minutes, the phosphoric acid extraction rate is 83%, and the purified phosphoric acid produced for one ton of phosphorus pentoxide consumes about 0.0161 tons of calcium carbonate.

[0029] 3. Fine desulfurization: The amount of barium carbonate added is 2-2.2 times the theoretical amount, the reaction temperature is 50℃, the ratio is 4:1, the reaction time is 60 minutes, and approximately 0.0056 tons of barium carbonate are consumed for every ton of purified phosphoric acid produced based on phosphorus pentoxide.

[0030] 4. Washing: Single-tower washing, temperature 50℃, ratio 18-20:1, vibration frequency 132Hz.

[0031] 5. Back-extraction: Temperature 60℃, double towers in series for back-extraction, ratio 5:1, vibration frequency 190Hz.

[0032] 6. Pre-concentration: Vacuum degree 0.085-0.09 MPa, temperature 80-90℃ 7. Final concentration: vacuum degree is 0.09 MPa, temperature is 90℃.

[0033] 8. Arsenic and heavy metal removal: The reaction temperature is 70℃, the amount of phosphorus pentasulfide added is 10-15 times the theoretical amount, and the reaction time is 0.5-1 hour.

[0034] 9. Stripping defluorination: The reaction temperature is 90-100℃. Each time, 13% water is added to bring the phosphoric acid content to 75%, and the mixture is repeatedly concentrated and stripped 6 times.

[0035] 10. Dechlorination and decolorization: Temperature 70℃, ozone concentration 110mg / L, flow rate 18L / min, dechlorination and decolorization time 60min; 11. Sensory analysis: Sensory analysis shall be conducted in accordance with the requirements of Table 1;

[0036] 12. Physicochemical analysis: Physicochemical analysis shall be conducted in accordance with the requirements of Table 2;

[0037] 13. Output food-grade phosphoric acid.

[0038] The extraction step in step 1 uses an extractant composed of TBP, a certain alcohol, and sulfonated kerosene.

[0039] The extractant components are in the following proportions or are in one of the following proportions: TBP + isooctyl alcohol / n-octanol + sulfonated kerosene, in a volume ratio of 5-8:1-3:1-2; TBP + cyclohexanol + sulfonated kerosene, in a volume ratio of 5-8:1-3:1-2; TBP + isopropanol / diisopropyl ether + sulfonated kerosene, in a volume ratio of 5-8:1-3:1-2.

[0040] The amount of sulfuric acid treated is as follows: a. Based on 10,000 tons of raw acid, the process time is 300 days, compared to a 5:1 ratio; the aqueous phase feed rate is 18.5 L / min, the organic phase feed rate is 92.6 L / min, and the total feed rate is 111.1 L / min.

[0041] b. Based on 12,000 tons of raw acid, the process time is 300 days, compared to a 5:1 ratio; the aqueous phase feed rate is 22.2 L / min, the organic phase feed rate is 111.1 L / min, and the total feed rate is 133.3 L / min.

[0042] The extraction tower adopts a dual-tower structure. The equipment parameters of the extraction tower are as follows: the height of the aqueous phase clarification section is 170 mm and the volume is 100 mL; the height of the mixing section is 1580 mm and the volume is 658 mL; the height of the oil phase clarification section is 165 mm and the volume is 275 mL. The extraction operation conditions are: temperature 50 ℃, phase ratio 4 - 5:1 (phase ratio refers to the volume ratio of oil phase to aqueous phase, the same below), vibration frequency 150 - 160 Hz (such a high frequency cannot be achieved in industry, it is basically 50 Hz), fixed oil phase feed rate of 30 mL / min, and aqueous phase feed rate of 5 - 6 mL / min.

[0043] The washing operation conditions are: temperature 50 ℃, ratio 18 - 20:1, vibration frequency 110 - 130 Hz (such a high frequency cannot be achieved industrially, so it is basically 50 Hz), fixed oil phase feed rate 30 mL / min, and aqueous phase feed rate 1.5 - 1.67 mL / min. The washing tower is the same as the extraction tower equipment.

[0044] The back-extraction equipment is a vibrating sieve plate tower, which can be divided into three sections: the bottom section is the aqueous phase clarification section, the middle section is the oil-water mixing section, and the top section is the oil phase clarification section. The parameters of the back-extraction tower are as follows: aqueous phase clarification section height 155 mm, capacity 66 mL; mixing section height 1370 mm, capacity 505 mL; oil phase clarification section height 150 mm, capacity 170 mL.

[0045] The operating conditions for the dual-tower tandem back-extraction were: temperature 60 ℃, phase ratio 5:1, vibration frequency 190 Hz, fixed oil phase feed rate 30 mL / min, and aqueous phase feed rate 6 mL / min.

[0046] In this invention, extraction involves mixing and contacting the raw acid and the extractant in an extraction device. Phosphoric acid (accompanied by a small amount of anionic impurities and a very small amount of cationic impurities) in the raw acid is extracted into the extractant. After mixing and contact, the raw acid and extractant undergo phase separation to obtain an extracted organic phase and raffinate. The raffinate is discharged from the process system as a raw material for other processes, while the extracted organic phase enters the coarse desulfurization section.

[0047] In this invention, the crude desulfurization process involves preparing a calcium-ion-containing crude desulfurization solution using calcium carbonate, refined desulfurization solution, and recycled crude desulfurization filtrate. This solution is then mixed and contacted with the extraction organic phase. Sulfate ions from the extraction organic phase enter the crude desulfurization solution and react with calcium ions to form calcium sulfate precipitate (typically dihydrate). After the reaction, the oil and water phases are separated. The organic phase from the crude desulfurization process enters the refined desulfurization section. The crude desulfurization solution containing the calcium sulfate precipitate is filtered to obtain calcium sulfate precipitate and the crude desulfurization filtrate. The calcium sulfate precipitate is discharged from the system, and the crude desulfurization filtrate is used to prepare the next batch of crude desulfurization solution.

[0048] In this invention, fine desulfurization involves dissolving barium carbonate in circulating fine desulfurization filtrate and washing acid to prepare barium-ion-containing fine desulfurization sulfuric acid. This fine desulfurization sulfuric acid is then mixed and contacted with the crude desulfurization organic phase. Sulfate ions from the crude desulfurization organic phase enter the fine desulfurization sulfuric acid and react with barium ions to form barium sulfate precipitate. After the reaction, the oil and water phases are separated. The organic phase after fine desulfurization enters the washing section, and the fine desulfurization sulfuric acid containing barium sulfate precipitate is filtered to obtain barium sulfate precipitate and fine desulfurization filtrate. The barium sulfate precipitate is discharged from the system, and a small portion of the fine desulfurization filtrate is used for crude desulfurization, while the remainder is mixed with washing acid for the next fine desulfurization step.

[0049] In this invention, the washing process involves contacting and mixing the organic phase from the desulfurization process with a small amount of back-extraction acid in a washing device. Impurities in the organic phase (accompanied by a small amount of phosphoric acid) are washed into the back-extraction acid. After mixing and contact, the back-extraction acid and organic phase undergo phase separation to obtain a washed organic phase and washing acid. The washing acid is mixed with the desulfurization filtrate for further desulfurization, while the washed organic phase enters the back-extraction section.

[0050] In this invention, back-extraction involves contacting and mixing the washing organic phase with deionized water (industrially, demineralized water) in a back-extraction device. Essentially all the phosphoric acid and impurities in the organic phase are back-extracted into the deionized water. The mixed deionized water and organic phase are then separated to obtain the back-extracted organic phase and back-extracted acid. A portion of the back-extracted acid is returned to the washing section of the previous step, while the remainder is used as the finished product, dilute phosphoric acid, and enters the pre-concentration section. The back-extracted organic phase is then returned to the extraction section for recycling.

[0051] In this invention, the concentration process involves using a vacuum concentration method to concentrate the back-extracted acid to a phosphoric acid concentration of approximately 85%.

[0052] In this invention, arsenic and heavy metal removal is performed by reacting 85% acid with phosphorus pentasulfide to generate hydrogen sulfide gas. This hydrogen sulfide gas is then fully mixed with the 85% acid in a closed arsenic removal device to obtain arsenic sulfide precipitate.

[0053] In this invention, steam stripping is used for defluorination. Dechlorination and decolorization are performed: the 85% acid after arsenic and weight removal is dechlorinated and decolorized using ozone aeration to obtain the final product, 85% acid.

Claims

1. A method for refining food-grade phosphoric acid using the sulfuric acid process, characterized in that, Phosphoric acid extraction is performed according to the sulfuric acid treatment volume using the following process steps. The preferred process conditions are:

1. Extraction: Add extractant into the extraction tower for extraction at 50℃, ratio 5:1, and vibration frequency 160-185.

2. Crude desulfurization: The amount of calcium carbonate added is 1.3 times the theoretical amount, the reaction temperature is 50℃, the ratio is 3-3.5:1, the reaction time is 60 minutes, the phosphoric acid extraction rate is 83%, and the purified phosphoric acid produced for one ton of phosphorus pentoxide consumes about 0.0161 tons of calcium carbonate.

3. Fine desulfurization: The amount of barium carbonate added is 2-2.2 times the theoretical amount, the reaction temperature is 50℃, the ratio is 4:1, the reaction time is 60 minutes, and approximately 0.0056 tons of barium carbonate are consumed for every ton of purified phosphoric acid produced based on phosphorus pentoxide.

4. Washing: Single-tower washing, temperature 50℃, ratio 18-20:1, vibration frequency 132Hz; 5. Back-extraction: Temperature 60℃, dual towers in series for back-extraction, ratio 5:1, vibration frequency 190Hz; 6. Pre-concentration: Vacuum degree is 0.085-0.09 MPa, temperature is 80-90℃; 7. Final concentration: vacuum degree is 0.09 MPa, temperature is 90℃; 8. Arsenic and heavy metal removal: reaction temperature 70℃, phosphorus pentasulfide added amount is 10-15 times the theoretical amount, reaction time 0.5-1 hour; 9. Stripping defluorination: The reaction temperature is 90-100℃. Each time, 13% water is added to bring the phosphoric acid to 75%, and the mixture is repeatedly concentrated and stripped 6 times.

10. Dechlorination and decolorization: Temperature 70℃, ozone concentration 110mg / L, flow rate 18L / min, dechlorination and decolorization time 60min; 11. Sensory analysis: Sensory analysis shall be conducted in accordance with the requirements of Table 1; 12. Physicochemical analysis: Physicochemical analysis shall be conducted in accordance with the requirements of Table 2; 13. Output food-grade phosphoric acid.

2. The method for refining food-grade phosphoric acid using the sulfuric acid process according to claim 1, characterized in that: The extraction step in step 1, wherein the extractant components are TBP + a certain alcohol + sulfonated kerosene.

3. The method for refining food-grade phosphoric acid using the sulfuric acid process according to claim 1, characterized in that: The extractant components are in the following proportions or according to one of the following proportions: TBP + isooctyl alcohol / n-octanol + sulfonated kerosene, in a volume ratio of 7:1:2; TBP + cyclohexanol + sulfonated kerosene, in a volume ratio of 7:1:2; TBP + isopropanol / diisopropyl ether + sulfonated kerosene, in a volume ratio of 7:1:

2.

4. The method for refining food-grade phosphoric acid using the sulfuric acid process according to claim 1, characterized in that: The amount of sulfuric acid treated is as follows: a. Based on 10,000 tons of raw acid, the process time is 300 days, compared to a 5:1 ratio; the aqueous phase feed rate is 18.5 L / min, the organic phase feed rate is 92.6 L / min, and the total feed rate is 111.1 L / min. b. Based on 12,000 tons of raw acid, the process time is 300 days, compared to a 5:1 ratio; the aqueous phase feed rate is 22.2 L / min, the organic phase feed rate is 111.1 L / min, and the total feed rate is 133.3 L / min.

5. The method for refining food-grade phosphoric acid using the sulfuric acid process according to claim 1, characterized in that: The extraction tower adopts a dual-tower structure. The equipment parameters of the extraction tower are as follows: the height of the aqueous phase clarification section is 170 mm and the volume is 100 mL; the height of the mixing section is 1580 mm and the volume is 658 mL; the oil phase clarification section is 165 mm and the volume is 275 mL. The extraction operation conditions are: temperature 50 ℃, phase ratio 4 - 5:1, vibration frequency 150 - 160 Hz, fixed oil phase feed rate of 30 mL / min, and aqueous phase feed rate of 5 - 6 mL / min.

6. The method for refining food-grade phosphoric acid using the sulfuric acid process according to claim 5, characterized in that: The back-extraction equipment is a vibrating sieve plate tower, which can be divided into three sections: the bottom section is the aqueous phase clarification section, the middle section is the oil-water mixing section, and the top section is the oil phase clarification section. The parameters of the back-extraction tower are as follows: aqueous phase clarification section height 155 mm, capacity 66 mL; mixing section height 1370 mm, capacity 505 mL; oil phase clarification section height 150 mm, capacity 170 mL.

7. The method for refining food-grade phosphoric acid using the sulfuric acid process according to claim 1, characterized in that: The washing operation conditions in step 4 are as follows: temperature 50 ℃, phase ratio 18 - 20:1, vibration frequency 110 - 130 Hz, fixed oil phase feed rate 30 mL / min, and aqueous phase feed rate 1.5 - 1.67 mL / min; the washing tower is the same as the extraction tower.

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