A method for producing phosphoric acid using corn steep liquor

Abstract

The present application belongs to the technical field of phosphoric acid production, and discloses a method for producing phosphoric acid by using corn soaking water. After the corn soaking water is doped with lime water, calcium phytate is obtained. Then, the calcium phytate is hydrolyzed at 160-180°C and 0.6-0.7 MPa. The hydrolysis liquid is acidified by adding concentrated sulfuric acid, and calcium sulfate is removed to obtain a filtrate. The filtrate is extracted by an extraction agent to obtain an extraction phase and a raffinate phase. The raffinate phase is filtered and then precipitated and centrifuged by using methanol or ethanol to obtain inositol. The centrifugal mother liquor is recovered and continuously extracted. The extraction phase is reversely extracted by using pure water to obtain a dilute phosphoric acid solution. The dilute phosphoric acid solution is decolorized by activated carbon and then vacuum concentrated to obtain a finished product of phosphoric acid. The present application has the effects of simple production process, low operation cost, full recovery of phosphorus resources, small wastewater discharge, high product purity, and wide application range.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of phosphoric acid production, and particularly relates to a method for producing phosphoric acid by using corn soaking water. BACKGROUND

[0002] Phosphoric acid is a chemical substance with a wide range of uses: in the food and beverage industry, phosphoric acid is used as a pH regulator, preservative and nutritional supplement; in the chemical industry, phosphoric acid is an important catalyst and intermediate for many chemical reactions, and is widely used in the synthesis of organic compounds, drugs, dyes and plastics; in agriculture, phosphoric acid is an important fertilizer ingredient that can provide plants with the phosphorus element they need. It is used for soil improvement and plant growth promotion in the agricultural field; in the electronics industry, phosphoric acid can be used as an electrolyte and electrolyte for batteries, for the charging and discharging process of the battery.

[0003] At present, the common phosphoric acid on the market is divided into hot process phosphoric acid and wet process phosphoric acid according to the production method: hot process phosphoric acid uses phosphorite, limestone and other raw materials, and goes through a series of grinding, roasting, oxidation and absorption processes to finally obtain phosphoric acid. The product has high purity and is often used in the chemical fertilizer, food, pharmaceutical and other industries, but the preparation process is complicated, the energy consumption is high, and a lot of pollutants such as sulfur dioxide are generated, which has a certain impact on the environment. The wet process phosphoric acid preparation process is relatively simple, which uses phosphorite and sulfuric acid as raw materials, and goes through acidification, filtration, concentration and other processes to obtain phosphoric acid product, and the production cost is relatively low, but the purity is relatively low and contains a certain degree of impurities; therefore, the wet process phosphoric acid is mainly used in the papermaking, metal surface treatment and other industrial fields.

[0004] Corn soaking water is a by-product produced in the process of wet production of corn starch, and the content of phytic acid (inositol hexakisphosphate) is about 1.5%. China is the largest corn starch producing country in the world, and produces about 35 million tons of corn soaking water every year, which contains rich plant phosphorus resources and has great development potential. At present, there are many reports on the process of recovering phytate from corn soaking water, and then hydrolyzing, separating and crystallizing to produce inositol and phosphate, but there are few reports on the process of producing phosphoric acid. CN115160108A reports a process for preparing inositol and phosphoric acid, which has the defects of long process flow, incomplete hydrolysis, large wastewater discharge and low phosphoric acid quality. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a method for producing phosphoric acid by using corn soaking water, which uses corn soaking water to prepare phosphoric acid, has a simple production process and low operating cost; fully recovers phosphorus resources, has less wastewater discharge, high product purity and wide application area; and has high economic and ecological benefits.

[0006] To solve the above technical problems, the technical scheme of the present application is:

[0007] A method for producing phosphoric acid by using corn steep liquor, comprising the following steps:

[0008] a. Neutralization: the corn steep liquor is removed suspended impurities by sedimentation, then lime water is added to neutralize the pH value of the solution to 6-8, and then filtered to obtain calcium phytate precipitate;

[0009] b. Hydrolysis: the calcium phytate obtained in step a is put into a feeding tank, water is added to pulp to a solid content of 20-30%wt, then transferred into a hydrolysis kettle, steam is introduced to heat to a temperature of 160-180°C and a pressure of 0.6-0.7 MPa, and hydrolysis is carried out under insulation and pressure, the hydrolysis time is 10-12 h, and the hydrolysis is completed when the pH value is 2-3 to obtain a hydrolysis solution;

[0010] c. Acidification: sulfuric acid with a concentration of 98.3% is added to the hydrolysis solution obtained in step b to perform acidification, the sulfuric acid reacts with calcium phosphate to generate insoluble calcium sulfate precipitate, the molar ratio of sulfuric acid to calcium phytate is 5-6:1, the reaction temperature is 60-80°C, and the reaction time is 2-4 h to obtain an acidification solution;

[0011] d. Filtration: the acidification solution obtained in step c is filtered by a plate and frame filter to remove the calcium sulfate precipitate, and the obtained filtrate is used as needed;

[0012] e. Extraction: an extractant is added to the filtrate obtained in step d to perform an extraction reaction, the extractant is n-butanol or tributyl phosphate, the phase ratio O / A is 4-6:1, the extraction temperature is 50-70°C, and the extraction time is 1-2 h; the extraction phase (upper layer) is an organic solution phase containing phosphoric acid, and the raffinate phase is an aqueous phase containing inositol, so that inositol and phosphoric acid are separated;

[0013] f. Inositol treatment: the raffinate phase (aqueous phase containing inositol) in step e is concentrated to a solid content of 10-15%wt by nanofiltration, then mixed with a solvent methanol or ethanol in an amount of 2-3 times the volume of the concentrated solution, and then precipitated for 3-5 h, and then inositol is obtained by centrifugation at 1500-3000 rpm, and the residual liquid produced after the solvent is recovered from the centrifugal mother liquor is combined with the plate and frame filter filtrate obtained in step d to perform extraction;

[0014] g. Reverse extraction: pure water is added to the extraction phase (organic phase containing phosphoric acid) in step e to perform reverse extraction, the phase ratio O / A is 0.5-1:1, the extraction times is 3-5 times, the extraction temperature is 50-70°C, and the extraction time is 0.2-0.5 h; a dilute phosphoric acid solution is obtained, and the raffinate phase produced by reverse extraction is returned to step e for repeated use as an extractant;

[0015] h. Decolorization: the dilute phosphoric acid solution obtained in step g is added to activated carbon for decolorization, the amount of activated carbon is 10-20 kg / m 3, the decoloring temperature is 30-40 DEG C, and the decoloring time is 0.5-1 h; after the decoloring is completed, the dilute phosphoric acid decoloring solution is filtered to obtain a dilute phosphoric acid decoloring solution;

[0016] i. concentration: the dilute phosphoric acid decoloring solution obtained in step h is concentrated under vacuum to obtain a phosphoric acid product; the temperature of the vacuum concentration is 80-90 DEG C, and the vacuum degree is -0.07 to -0.09 MPa.

[0017] Preferably, the material liquid in step a is neutralized to a pH value of 7.

[0018] Preferably, in step b, the water is beaten to a solid content of 25% wt, and then transferred into a hydrolysis kettle, steam is introduced to heat to a temperature of 170 DEG C and a pressure of 0.65 MPa, and hydrolysis is carried out under insulation and pressure, the hydrolysis time is 11 h, and the hydrolysis is completed when the pH value is 2.5.

[0019] Preferably, in step c, the molar ratio of sulfuric acid to calcium phytate is 5.5:1, the reaction temperature is 70 DEG C, and the reaction time is 3 h.

[0020] Preferably, in step d, the model of the plate and frame filter is XMZGF200 / 1250-U, and the manufacturer is Jingjin Equipment Co., Ltd.

[0021] Preferably, in step e, the extractant is n-butanol, the extraction phase ratio O / A is 5:1, the extraction temperature is 60 DEG C, and the extraction time is 1.5 h.

[0022] Preferably, in step f, the solid content after nanofiltration concentration is 12.5% wt, the nanofiltration membrane pore size is 100 Da; 2.5 times the volume of the concentrated solution of solvent methanol is added and mixed, and then precipitated for 4 h; centrifuged at 2500 rpm.

[0023] Preferably, in step g, the reverse extraction phase ratio O / A is 0.75:1, the extraction times is 4 times, the extraction temperature is 60 DEG C, and the extraction time is 0.35 h.

[0024] Preferably, in step h, the amount of activated carbon is 15 kg / m 3 , the decoloring temperature is 35 DEG C, and the decoloring time is 0.75 h.

[0025] Preferably, in step i, the temperature of the vacuum concentration is 85 DEG C, and the vacuum degree is -0.08 MPa.

[0026] The phosphoric acid produced by soaking corn water has the characteristics of high purity (75-85% wt), and therefore can be widely used in food, medicine, electronics and other fields.

[0027] Due to the adoption of the above technical scheme, the present application has the following beneficial effects:

[0028] The present application further expands the source of high-quality phosphoric acid by using the phosphoric acid produced from corn soaking water generated in the corn deep processing process, slows down the ecological destruction and environmental pollution caused by the mining of phosphate rock and the hot process of phosphoric acid, and the production process is simple, the operation cost is low, the phosphorus resources are fully recovered, the wastewater discharge is small, the product purity is high, and the application area is wide, so the present application has significant economic and ecological benefits. DETAILED DESCRIPTION

[0029] The technical solutions of the present application are further described below in combination with examples:

[0030] Example 1:

[0031] a. Neutralization: 10 m 3 The corn soaking water is removed from suspended impurities by sedimentation, then lime water is added to neutralize the pH value of the slurry to 6, and then filtered to obtain 285 kg of calcium phytate precipitate;

[0032] b. Hydrolysis: The calcium phytate obtained in step a is put into a feeding tank, 400 liters of water are added to pulp to a solid content of 20% wt, then transferred into a hydrolysis kettle, steam is introduced to heat to a temperature of 160℃ and a pressure of 0.6 MPa, and hydrolysis is carried out under insulation and pressure, the hydrolysis time is 12 h, and the hydrolysis is completed when the pH value is 2;

[0033] c. Acidification: 45 liters of 98.3% concentrated sulfuric acid is added to the hydrolysis liquid obtained in step b for acidification, the sulfuric acid reacts with calcium phosphate to generate insoluble calcium sulfate precipitate, the molar ratio of sulfuric acid to calcium phosphate is 5:1, the reaction temperature is 60℃, and the reaction time is 4 h;

[0034] d. Filtration: The acidified liquid obtained in step c is filtered by plate and frame filtration (filter cloth aperture 300 meshes, filtration pressure 0.3 MPa) to remove the calcium sulfate precipitate, and 500 liters of the obtained filtrate is reserved for use;

[0035] e. Extraction: Tributyl phosphate is added to the plate and frame filtrate obtained in step d for extraction reaction, the extraction phase ratio O / A is 4:1, the extraction temperature is 50℃, and the extraction time is 2 h; the extraction phase (upper layer) is an organic solution phase containing phosphoric acid, 2100 liters are obtained, and the raffinate phase is an aqueous phase containing inositol, 400 liters are obtained, and the separation of inositol and phosphoric acid is realized;

[0036] f. Inositol treatment: The raffinate phase (aqueous phase containing inositol) in step e is concentrated to a solid content of 10% wt by nanofiltration (nanofiltration membrane molecular weight cut-off 100 Da), 250 liters, then mixed with 2 times the volume of solvent ethanol, precipitated for 3 h, and then inositol 30 kg is obtained by centrifugation at 1500 rpm, the residual liquid produced after recovering the solvent from the centrifugal mother liquor is combined with the plate and frame filtrate obtained in step d, and then extraction is carried out;

[0037] g. Back-extraction: Add 4200 L of purified water to the extract phase (organic phase containing phosphoric acid) from step e for back-extraction. The O / A ratio of the back-extraction phase is 0.5:1, the number of extractions is 5, the extraction temperature is 50℃, and the extraction time is 0.5 h. 21000 L of dilute phosphoric acid solution is obtained. The raffinate generated by back-extraction is returned to step e and reused as an extractant.

[0038] h. Decolorization: The dilute phosphoric acid solution obtained in step g is added to 210 kg of activated carbon for decolorization. The amount of activated carbon used is 10 kg / m³. 3 The decolorization temperature was 30℃, and the decolorization time was 1 hour. After the decolorization was completed, the solution was filtered to obtain 21,000 liters of dilute phosphoric acid decolorized solution.

[0039] i. Concentration: The dilute phosphoric acid decolorizing solution obtained in step h is concentrated under vacuum at a temperature of 80°C and a vacuum degree of -0.07 MPa; 70 liters of phosphoric acid product with a concentration of 75% wt are obtained, with a yield of 92%.

[0040] Example 2:

[0041] a. Neutralization: 10m 3 The corn soaking water was used to remove suspended impurities by sedimentation, and then lime water was added to neutralize the solution to pH 8. After filtration, 310 kg of calcium phytate precipitate was obtained.

[0042] b. Hydrolysis: The calcium phytate obtained in step a is put into a feeding tank, 200 liters of water is added and the mixture is slurried until the solid content is 30% wt. Then it is transferred to a hydrolysis kettle, steam is introduced and heated to a temperature of 180℃ and a pressure of 0.7 MPa. The temperature and pressure are maintained for hydrolysis for 10 hours and the hydrolysis ends when the pH value is 3.

[0043] c. Acidification: Add 55 liters of 98.3% sulfuric acid to the hydrolysate obtained in step b for acidification. The sulfuric acid reacts with calcium dihydrogen phosphate to form an insoluble calcium sulfate precipitate. The molar ratio of sulfuric acid to calcium phytate is 6:1. The reaction temperature is 80℃ and the reaction time is 2h.

[0044] d. Filtration: The acidified solution obtained in step c is filtered through a plate and frame filter (300 mesh filter cloth, 0.3 MPa filtration pressure) to remove calcium sulfate precipitate, and 400 liters of filtrate are prepared for use.

[0045] e. Extraction: Tributyl phosphate was added to the plate and frame filtrate obtained in step d for extraction reaction. The extraction ratio of O / A was 6:1, the extraction temperature was 70℃, and the extraction time was 1h. The extraction phase (upper layer) was an organic solvent phase containing phosphoric acid, yielding 2500 liters. The raffinate phase was an aqueous phase containing inositol, yielding 300 liters, thus achieving the separation of inositol and phosphoric acid.

[0046] f. Inositol treatment: the raffinate phase (containing inositol aqueous phase) in step e was concentrated to solid content 15%wt, 185 liters by nanofiltration (nanofiltration membrane molecular weight cut-off 100 Da), then 3 times the volume of solvent ethanol was added and mixed, precipitated for 5 h, and then inositol 29.5 kg was obtained by centrifugation at 3000 rpm. The residual liquid produced after recovery of the solvent from the centrifugal mother liquor was combined with the plate and frame filtrate obtained in step d and subjected to extraction;

[0047] g. Reverse extraction: 2500 liters of pure water was added to the extraction phase (containing phosphoric acid organic phase) in step e to perform reverse extraction, the reverse extraction phase ratio O / A was 1:1, the extraction times was 3 times, the extraction temperature was 70°C, and the extraction time was 0.2 h; 7500 liters of dilute phosphoric acid solution was obtained, and the raffinate phase produced by reverse extraction was returned to step e for repeated use as an extractant;

[0048] h. Decolorization: 150 kg of activated carbon was added to the dilute phosphoric acid solution obtained in step g to perform decolorization, the activated carbon dosage was 20 kg / m 3 , the decolorization temperature was 40°C, and the decolorization time was 0.5 h; after decolorization, filtration was performed to obtain 7500 liters of dilute phosphoric acid decolorization liquid;

[0049] i. Concentration: the dilute phosphoric acid decolorization liquid obtained in step h was concentrated under vacuum, the vacuum concentration temperature was 90°C, and the vacuum degree was -0.09 MPa; 65 liters of 80%wt phosphoric acid product was obtained, and the yield was 93%.

[0050] Example 3:

[0051] a. Neutralization: 10 m 3 Corn soaking water was treated by sedimentation to remove suspended impurities, then lime water was added to neutralize the liquid to a pH value of 7, and then filtration was performed to obtain 300 kg of calcium phytate precipitate;

[0052] b. Hydrolysis: the calcium phytate obtained in step a was put into a feeding tank, 300 kg of water was added to pulp to a solid content of 25%wt, then it was transferred into a hydrolysis kettle, steam was introduced to heat to a temperature of 170°C and a pressure of 0.65 MPa, and hydrolysis was performed under isothermal and isobaric conditions, the hydrolysis time was 11 h, and the hydrolysis was stopped when the pH value reached 2.5;

[0053] c. Acidification: 50 liters of 98.3% sulfuric acid was added to the hydrolysis liquid obtained in step b to perform acidification, the molar ratio of sulfuric acid to calcium phytate was 5.5:1, the reaction temperature was 70°C, and the reaction time was 3 h;

[0054] d. Filtration: the acidified liquid obtained in step c was subjected to plate and frame filtration (filter cloth aperture 300 meshes, filtration pressure 0.3 MPa) to remove calcium sulfate precipitate, and 450 liters of filtrate was obtained for standby use;

[0055] e. Extraction: the plate and frame filtrate obtained in step d is added with n-butanol for extraction reaction, the extraction phase ratio O / A is 5:1, the extraction temperature is 60°C, the extraction time is 1.5h; the extraction phase (upper layer) is the organic phase containing phosphoric acid, 2300 liters are obtained, the raffinate phase is the water phase containing inositol, 400 liters are obtained, realizing the separation of inositol and phosphoric acid;

[0056] f. Inositol treatment: the raffinate phase (water phase containing inositol) in step e is concentrated to a solid content of 12.5%wt by nanofiltration (nanofiltration membrane molecular weight cut-off 100Da), then 2.5 times the volume of solvent methanol is added to mix and precipitate for 4h, and then inositol 31 kg is obtained by centrifugation at 2500 rpm, and the residual liquid produced after recovery of the solvent from the centrifugal mother liquor is combined with the plate and frame filtrate obtained in step d for extraction;

[0057] g. Reverse extraction: 3060 liters of pure water is added to the extraction phase (organic phase containing phosphoric acid) in step e for reverse extraction, the reverse extraction phase ratio O / A is 0.75:1, the extraction times is 4, the extraction temperature is 60°C, the extraction time is 0.35h; 12240 liters of dilute phosphoric acid solution is obtained, and the raffinate phase produced by reverse extraction is returned to step e for repeated use as an extractant;

[0058] h. Decolorization: 103.5 kg of activated carbon is added to the dilute phosphoric acid solution obtained in step g for decolorization, the activated carbon dosage is 15 kg / m 3 , the decolorization temperature is 35°C, the decolorization time is 0.75h; after decolorization, filtration is performed to obtain 12240 liters of dilute phosphoric acid decolorization liquid;

[0059] i. Concentration: the dilute phosphoric acid decolorization liquid obtained in step h is concentrated under vacuum, the vacuum concentration temperature is 85°C, the vacuum degree is -0.08 MPa; 60 liters of 85%wt phosphoric acid product is obtained, the yield is 93.5%.

[0060] Example 4:

[0061] a. Neutralization: 10 m 3 Corn soaking water is treated by sedimentation to remove suspended impurities, then lime water is added to neutralize the pH value of the feed liquid to 7, then filtration is performed to obtain 305 kg of calcium phytate precipitate;

[0062] b. Hydrolysis: the calcium phytate obtained in step a is put into a feeding tank, 305 kg of water is added to pulp to a solid content of 25%wt, then it is transferred into a hydrolysis kettle, steam is introduced to heat to a temperature of 180°C and a pressure of 0.7 MPa, and hydrolysis is carried out under the conditions of temperature and pressure, the hydrolysis time is 10h, and the hydrolysis is stopped when the pH value reaches 2.5;

[0063] c. Acidification: The hydrolysis solution obtained in step b was acidified by adding 50 liters of sulfuric acid with a concentration of 98.3%, and the molar ratio of sulfuric acid to calcium phytate was 5.5:1. The reaction temperature was 70°C, and the reaction time was 3 hours;

[0064] d. Filtration: The acidified solution obtained in step c was filtered by plate and frame filtration (filter cloth aperture 400 mesh, filtration pressure 0.4 MPa) to remove calcium sulfate precipitate, and 460 liters of filtrate was obtained for standby use;

[0065] e. Extraction: n-Butanol was added to the plate and frame filtrate obtained in step d to perform extraction reaction, the extraction phase ratio O / A was 5:1, the extraction temperature was 60°C, and the extraction time was 1.5 hours. The extraction phase (upper layer) was an organic solution phase containing phosphoric acid, and 2360 liters was obtained. The raffinate phase was an aqueous phase containing inositol, and 400 liters was obtained, realizing the separation of inositol and phosphoric acid;

[0066] f. Inositol treatment: The raffinate phase (aqueous phase containing inositol) in step e was concentrated to a solid content of 12.5% wt by nanofiltration (nanofiltration membrane molecular weight cut-off 100 Da), then 2.5 times the volume of solvent methanol was added, mixed uniformly, and precipitated for 4 hours. Inositol 30.5 kilograms was obtained by centrifugation at 2500 rpm. The residual liquid produced after recovering the solvent from the centrifugal mother liquor was combined with the plate and frame filtrate obtained in step d and subjected to extraction;

[0067] g. Reverse extraction: 3150 liters of pure water was added to the extraction phase (organic phase containing phosphoric acid) in step e to perform reverse extraction, the reverse extraction phase ratio O / A was 0.75:1, the extraction times was 4, the extraction temperature was 60°C, and the extraction time was 0.35 hours. Dilute phosphoric acid solution 12600 liters was obtained, and the raffinate phase produced by reverse extraction was returned to step e for repeated use as an extractant;

[0068] h. Decolorization: 189 kg of activated carbon was added to the dilute phosphoric acid solution obtained in step g to perform decolorization, the activated carbon dosage was 15 kg / m 3 , the decolorization temperature was 35°C, and the decolorization time was 0.75 hours. After decolorization, filtration was performed to obtain 12600 liters of dilute phosphoric acid decolorization liquid;

[0069] i. Concentration: The dilute phosphoric acid decolorization liquid obtained in step h was concentrated under vacuum, the vacuum concentration temperature was 85°C, and the vacuum degree was -0.08 MPa. Concentrated phosphoric acid product 58 liters with a concentration of 85% wt was obtained, and the yield was 90.4%.

[0070] Example 5:

[0071] a. Neutralization: 10 m 3 Corn soaking water was treated by sedimentation to remove suspended impurities, then lime water was added to neutralize the pH value of the liquid to 7, and then filtration was performed to obtain 300 kilograms of calcium phytate precipitate;

[0072] b. Hydrolysis: The calcium phytate obtained from step a was put into a feeding tank, 300 kg of water was added to pulp to solid content of 25%wt, then transferred into a hydrolysis kettle, steam was introduced to heat to temperature of 170°C and pressure of 0.65 MPa, hydrolysis was carried out under the condition of temperature and pressure, hydrolysis time was 11 h, hydrolysis was ended when pH value was 2.5;

[0073] c. Acidification: 45 liters of sulfuric acid with concentration of 98.3% was added to the hydrolysis solution obtained from step b to carry out acidification, the molar ratio of sulfuric acid to calcium phytate was 5:1, reaction temperature was 70°C, reaction time was 3 h;

[0074] d. Filtration: The acidification solution obtained from step c was filtered by plate and frame filter (filter cloth aperture was 400 mesh, filtration pressure was 0.4 MPa) to remove calcium sulfate precipitate, 450 liters of filtrate was obtained for standby use;

[0075] e. Extraction: Tributyl phosphate was added to the plate and frame filtrate obtained from step d to carry out extraction reaction, the phase ratio of O / A was 5:1, extraction temperature was 60°C, extraction time was 1.5 h; the extraction phase (upper layer) was organic solution phase containing phosphoric acid, 2300 liters was obtained, the raffinate phase was water phase containing inositol, 400 liters was obtained, realizing separation of inositol and phosphoric acid;

[0076] f. Inositol treatment: The raffinate phase (water phase containing inositol) in step e was concentrated to solid content of 12.5%wt by nanofiltration (nanofiltration membrane molecular weight cut-off was 100 Da), then 2.5 times volume of solvent methanol was added to mix evenly, then precipitated for 4 h, inositol 30.6 kg was obtained by centrifugation at 1500 rpm, the residual liquid produced by recovery of solvent from the centrifugal mother liquor was combined with the plate and frame filtrate obtained from step d to carry out extraction;

[0077] g. Reverse extraction: 3060 liters of pure water was added to the extraction phase (organic phase containing phosphoric acid) in step e to carry out reverse extraction, the phase ratio of O / A was 0.75:1, extraction times was 4, extraction temperature was 60°C, extraction time was 0.35 h; dilute phosphoric acid solution 12240 liters was obtained, the raffinate phase produced by reverse extraction was returned to step e for repeated use as extraction agent;

[0078] h. Decolorization: 103.5 kg of activated carbon was added to the dilute phosphoric acid solution obtained from step g to carry out decolorization, the dosage of activated carbon was 15 kg / m 3 , decolorization temperature was 35°C, decolorization time was 0.75 h; after decolorization, filtration was carried out to obtain dilute phosphoric acid decolorization liquid 12240 liters;

[0079] i. Concentration: The dilute phosphoric acid decolorization liquid obtained from step h was concentrated by vacuum concentration, the temperature of vacuum concentration was 85°C, the vacuum degree was -0.08 MPa; 59 liters of phosphoric acid product with concentration of 85%wt was obtained, the yield was 91.9%.

[0080] Example 6:

[0081] a. Neutralization: 10 m 3 The corn soaking water was removed suspended impurities by sedimentation, then added lime water to neutralize the pH value of the feed liquid to 7.5, then filtered to obtain 310 kg of calcium phytate precipitate;

[0082] b. Hydrolysis: The calcium phytate obtained in step a was put into a feeding tank, and 310 kg of water was added to pulp to a solid content of 25% wt, then transferred into a hydrolysis kettle, and steam was introduced to heat to a temperature of 170℃ and a pressure of 0.65 MPa, and hydrolysis was carried out under the conditions of temperature and pressure, the hydrolysis time was 11 h, and the hydrolysis was completed when the pH value was 2.8;

[0083] c. Acidification: 50 liters of sulfuric acid with a concentration of 98.3% was added to the hydrolysis liquid obtained in step b to acidify, the molar ratio of sulfuric acid to calcium phytate was 5.5:1, the reaction temperature was 60℃, and the reaction time was 4 h;

[0084] d. Filtration: The acidified liquid obtained in step c was filtered by plate and frame filtration (filter cloth aperture 300 meshes, filtration pressure 0.3 MPa) to remove calcium sulfate precipitate, and 450 liters of filtrate was obtained for standby use;

[0085] e. Extraction: n-butanol was added to the plate and frame filtrate obtained in step d to carry out extraction reaction, the phase ratio O / A was 5:1, the extraction temperature was 60℃, and the extraction time was 1.5 h; the extraction phase (upper layer) was an organic solution phase containing phosphoric acid, 2300 liters were obtained, and the raffinate phase was an aqueous phase containing inositol, 400 liters were obtained, achieving separation of inositol and phosphoric acid;

[0086] f. Inositol treatment: The raffinate phase (aqueous phase containing inositol) in step e was concentrated to a solid content of 12.5% wt by nanofiltration (nanofiltration membrane molecular weight cut-off 100 Da), then 2.5 times the volume of solvent ethanol was added to mix and precipitate for 4 h, and inositol 30.3 kg was obtained by centrifugation at 2500 rpm, the residual liquid produced by recovering the solvent from the centrifugal mother liquor was combined with the plate and frame filtrate obtained in step d, and extraction was carried out;

[0087] g. Reverse extraction: 3060 liters of pure water was added to the extraction phase (organic phase containing phosphoric acid) in step e to carry out reverse extraction, the phase ratio O / A was 0.75:1, the extraction times was 4, the extraction temperature was 60℃, and the extraction time was 0.35 h; a dilute phosphoric acid solution 12240 liters was obtained, and the raffinate phase produced by reverse extraction was returned to step e for repeated use as an extractant;

[0088] h. Decolorization: The dilute phosphoric acid solution obtained in step g was added to 103.5 kg of activated carbon for decolorization, the activated carbon dosage was 15 kg / m 3 , the decolorization temperature was 35℃, and the decolorization time was 0.75 h; after decolorization, filtration was carried out to obtain a dilute phosphoric acid decolorization liquid 12240 liters;

[0089] i. Concentration: the decolorized dilute phosphoric acid solution obtained in step h is concentrated under vacuum, the temperature of vacuum concentration is 85°C, and the vacuum degree is -0.08 MPa; 62 liters of 80%wt phosphoric acid product is obtained, with a yield of 89.2%.

[0090] Result analysis: the product of examples 1-6 is detected (the detection method is according to the method described in GB 3149-2004 "food additive phosphoric acid"), and the results are shown in table 1.

[0091] Table 1: content yield and heavy metal detection results of products of examples 1-6

[0092]

[0093] From the detection data of examples 1-6, it can be seen that the content and impurity content of the phosphoric acid produced by the process of the present application meet the requirements of food-grade phosphoric acid in the national food safety standard; the process conditions of example 3 are the best, the product yield is the highest, and the impurity content is the lowest.

[0094] It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. Furthermore, it should be understood that after reading the content taught by the present application, those skilled in the art can make various modifications or changes to the present application, and these equivalent forms also fall within the scope defined by the claims attached to the present application.

Claims

1. A method for producing phosphoric acid using corn steep liquor, characterized by: The method comprises the following steps: a. Neutralization: corn soaking water is settled to remove suspended impurities, then lime water is added to neutralize the feed liquid to a pH value of 6-8, and then filtered to obtain calcium phytate precipitate; b. Hydrolysis: the calcium phytate obtained in step a is put into a feeding tank, water is added to pulp to a solid content of 20-30%wt, then transferred into a hydrolysis kettle, steam is introduced to heat to a temperature of 160-180°C and a pressure of 0.6-0.7 MPa, and hydrolysis is carried out under the conditions of temperature and pressure, the hydrolysis time is 10-12 h, and the hydrolysis is ended when the pH value is 2-3 to obtain a hydrolysis liquid; c. Acidification: sulfuric acid with a concentration of 98.3% is added to the hydrolysis liquid obtained in step b to carry out acidification, the molar ratio of sulfuric acid to calcium phytate is 5-6:1, the reaction temperature is 60-80°C, and the reaction time is 2-4 h to obtain an acidification liquid; d. Filtration: the acidification liquid obtained in step c is filtered through a plate and frame filter to remove calcium sulfate precipitate, and the obtained filtrate is used for standby; e. Extraction: an extractant is added to the filtrate obtained in step d to carry out extraction reaction, the extractant is n-butanol or tributyl phosphate, the phase ratio O / A is 4-6:1, the extraction temperature is 50-70°C, and the extraction time is 1-2 h; the extraction phase is an organic solution phase containing phosphoric acid, and the raffinate phase is an aqueous phase containing inositol; f. Inositol treatment: the raffinate phase in step e is concentrated by nanofiltration to a solid content of 10-15%wt, then 2-3 times the volume of solvent methanol or ethanol is added to mix uniformly, and then precipitated for 3-5 h, and inositol is obtained by centrifugation at 1500-3000 rpm, and the residual liquid produced by recovering the solvent from the centrifugal mother liquor is combined with the plate and frame filtrate obtained in step d to carry out extraction; g. Reverse extraction: pure water is added to the extraction phase in step e to carry out reverse extraction, the phase ratio O / A is 0.5-1:1, the extraction times is 3-5 times, the extraction temperature is 50-70°C, and the extraction time is 0.2-0.5 h; a dilute phosphoric acid solution is obtained, the raffinate phase produced by reverse extraction is returned to step e to be reused as an extractant; h. decolorization: the dilute phosphoric acid solution obtained in step g is added to activated carbon for decolorization, the amount of activated carbon is 10-20 kg / m 3 , the decolorization temperature is 30-40 °C, the decolorization time is 0.5-1 h; after the decolorization is completed, the dilute phosphoric acid decolorization solution is obtained by filtration; i. Concentration: the dilute phosphoric acid decolorization liquid obtained in step h is concentrated under vacuum to obtain a phosphoric acid product; the concentration temperature is 80-90°C, and the vacuum degree is -0.07 to -0.09 MPa.

2. The method for producing phosphoric acid using corn steep liquor according to claim 1, characterized by: In step a, the feed liquid is neutralized to a pH value of 7.

3. The method for producing phosphoric acid using corn steep liquor according to claim 1, wherein: In step b, water is added to pulp to a solid content of 25%wt, then transferred into a hydrolysis kettle, steam is introduced to heat to a temperature of 170°C and a pressure of 0.65 MPa, and hydrolysis is carried out under the conditions of temperature and pressure, the hydrolysis time is 11 h, and the hydrolysis is ended when the pH value is 2.

5.

4. The method for producing phosphoric acid using corn steep liquor according to claim 1, wherein: In step c, the molar ratio of sulfuric acid to calcium phytate is 5.5:1, the reaction temperature is 70°C, and the reaction time is 3 h.

5. The method for producing phosphoric acid using corn steep liquor according to claim 1, wherein: In step e, the extractant is n-butanol, the phase ratio O / A is 5:1, the extraction temperature is 60°C, and the extraction time is 1.5 h.

6. The method for producing phosphoric acid using corn steep liquor according to claim 1, wherein: In step f, the solid content after nanofiltration concentration is 12.5%wt, the nanofiltration membrane pore size is 100 Da; 2.5 times the volume of solvent methanol is added to mix uniformly, and then precipitated for 4 h; centrifugation is carried out at 2500 rpm.

7. The method for producing phosphoric acid using corn soaking water as described in claim 1, characterized in that: In step g, the phase ratio O / A is 0.75:1, the extraction times is 4 times, the extraction temperature is 60°C, and the extraction time is 0.35 h.

8. The method for producing phosphoric acid using corn soaking water as described in claim 1, characterized in that: The activated carbon dosage in step h is 15 kg / m 3 , the bleaching temperature is 35℃, and the bleaching time is 0.75 h.

9. The method for producing phosphoric acid using corn steep liquor according to claim 1, wherein: The temperature of the vacuum concentration in step i is 85°C, and the vacuum degree is -0.08 MPa. The temperature of the vacuum concentration in step i is 85°C, and the vacuum degree is -0.08 MPa.

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