阅读说明：本技术 一种利用工业湿法净化磷酸制造食品级磷酸氢二钠的方法 (Method for preparing food-grade disodium hydrogen phosphate by using industrial wet-process purified phosphoric acid ) 是由 吴正奇 李摇摇 姚其凤 徐歆 许琦 吴龙 李倩 陈小强 于 2018-08-09 设计创作，主要内容包括：本发明公开了一种利用工业湿法净化磷酸制造食品级磷酸氢二钠的方法：⑴加水稀释：取工业湿法净化磷酸于耐酸容器中加纯水搅拌稀释；⑵中和反应与脱氟硫：加入脱氟硫剂和氢氧化钠搅拌反应,膜过滤得精密过滤的中和液；⑶氧化脱砷、微碱性脱重金属与膜过滤：调节中和液的pH至微碱性、加入氧化剂、加热、冷却、膜过滤,得精密过滤的微碱性脱重金属和氧化脱砷液；⑷pH调节与浓缩：用氢氧化钠调整pH值并浓缩,得磷酸氢二钠浓缩液；⑸降温结晶：浓缩液转入结晶设备内,搅拌、冷却、结晶、固液分离,得磷酸氢二钠湿结晶；⑹结晶干燥：湿结晶干燥至产品要求水分,得食品级磷酸氢二钠产品。方法易行,成本低,纯度高,砷和重金属离子脱除充分,溶解性能好。(The invention discloses a method for preparing food-grade disodium hydrogen phosphate by using industrial wet-process purified phosphoric acid, which comprises the steps of ⑴ diluting with water, putting the industrial wet-process purified phosphoric acid into an acid-resistant container, adding pure water, stirring and diluting, ⑵ neutralizing reaction and defluorination, adding a defluorination and desulfurization agent and sodium hydroxide, stirring and reacting, performing membrane filtration to obtain a precisely filtered neutralizing solution, ⑶ oxidizing and dearsenifying and slightly alkaline heavy metal removal and membrane filtration, adjusting the pH value of the neutralizing solution to be slightly alkaline, adding an oxidant, heating, cooling and performing membrane filtration to obtain a precisely filtered slightly alkaline heavy metal removal and oxidized dearsenification solution, ⑷ adjusting the pH value, concentrating, adjusting the pH value by using sodium hydroxide, obtaining a disodium hydrogen phosphate concentrated solution, ⑸ cooling and crystallizing, transferring the concentrated solution into a crystallizing device, stirring, cooling, crystallizing, and performing solid-liquid separation to obtain disodium hydrogen phosphate wet crystals, ⑹ crystallizing and drying, drying the wet crystals to obtain the product requiring moisture, thus obtaining the food-grade disodium hydrogen phosphate product.)

1. A method for preparing food-grade disodium hydrogen phosphate by using industrial wet-process purified phosphoric acid is characterized by comprising the following steps:

⑴ adding water to dilute the phosphoric acid, placing the phosphoric acid into an acid-proof container, adding water with the mass multiple of 0.5-3.1 times of the phosphoric acid under the condition of stirring to obtain a dilute phosphoric acid solution with the mass percentage concentration of 20.7-56.7%, and continuously stirring to obtain a dilute phosphoric acid solution for industrial wet purification;

⑵ performing neutralization reaction and defluorination and desulfurization, namely putting a phosphoric acid diluent ⑴ into an acid-resistant container, adding a defluorination and desulfurization agent with the mass fraction of 0.1-1% of the phosphoric acid diluent under the condition of stirring, continuously stirring to ensure that the defluorination and desulfurization agent are fully dissolved and fully reacted with fluoride ions and sulfate radicals in the phosphoric acid diluent to obtain a reaction mixture, neutralizing the reaction mixture by using a sodium hydroxide solution with the mass percentage concentration of 20-50% under the condition of stirring until the pH value is 3.9-4.8, continuously stirring to obtain a neutralization solution, controlling the temperature of the neutralization solution to be 20-60 ℃, and performing precise filtration on the neutralization solution by using membrane filtration equipment to obtain the precisely filtered neutralization solution for later use;

⑶, oxidizing to remove arsenic, slightly alkaline to remove heavy metal and membrane filtering, under the condition of continuous stirring, adjusting the pH of the neutralized liquid obtained by the precise filtration of ⑵ to 7.0-8.0 by using a sodium hydroxide solution with the mass percentage concentration of 20-50%, adding an oxidant with the mass fraction of 0.1-4% of the neutralized liquid, heating the mixture and maintaining the temperature to the temperature required by arsenic oxidation, refluxing, preserving heat and oxidizing for 0.5-8 hours under the condition of stirring, then opening cooling water to reduce the temperature of the mixture to 10-50 ℃, continuing stirring for 0.5-10 hours, and precisely filtering the mixture by using membrane filtering equipment to obtain the slightly alkaline to remove heavy metal and the oxidized arsenic-removing liquid for later use;

⑷, adjusting and concentrating the pH of the solution after ⑶ of slightly alkaline heavy metal removal and arsenic removal by oxidation to 8.7-9.7 by using a sodium hydroxide solution with the mass percentage concentration of 20-50% under the condition of continuously stirring to obtain a disodium hydrogen phosphate solution, and concentrating the disodium hydrogen phosphate solution to the mass percentage concentration of 40-60% by using a forced circulation vacuum concentration method under the conditions of the vacuum degree of 0.8-0.99 MPa and the temperature of 70-110 ℃ to obtain a disodium hydrogen phosphate concentrated solution for later use;

⑸, cooling and crystallizing, namely transferring the ⑷ obtained disodium hydrogen phosphate concentrated solution into a crystallizing device, crystallizing disodium hydrogen phosphate within the temperature range of a metastable zone of disodium hydrogen phosphate crystals for 1-25 hours, then reducing the temperature to 1-30 ℃ at a cooling speed of 1-10 ℃/hour, and continuously crystallizing for 1-50 hours until no crystals are generated;

⑹ drying the crystal, drying the ⑸ wet crystal of disodium hydrogen phosphate by hot air at normal pressure until the water content of the product is required, cooling and packaging to obtain the food grade disodium hydrogen phosphate product, wherein the temperature of the material in the whole process of the step is controlled to be less than or equal to 120 ℃.

2. The method as claimed in claim 1, wherein the step ⑴ comprises defluorinating, desulfurizing, extracting, back-extracting, purifying, and purifying the phosphoric acid with 85% by weight of phosphoric acid, wherein the phosphoric acid with conductivity less than 10 is superior, and qualified products according to HG/T4069-^-3s/m reverse osmosis process pure water, ion exchange process pure water, and distillation condensation process pure water.

3. The method as claimed in claim 1, wherein the defluorinating agent used in step ⑵ is analytically or chemically pure barium carbonate or barium bicarbonate, the sodium hydroxide is analytically or chemically pure solid sodium hydroxide, and the membrane filtration device is silicon carbide, has a membrane module form of honeycomb-coal-type inner tubular membrane with a pore size of 1, 0.5, 0.1 or 0.04 μm.

4. The method for preparing food-grade disodium hydrogen phosphate by using industrial wet-process purified phosphoric acid according to claim 1, wherein the sodium hydroxide in step ⑶ is analytically or chemically pure solid sodium hydroxide, the oxidants are analytically or chemically pure hydrogen peroxide (hydrogen peroxide) and bleaching powder, the temperature required by arsenic oxidation is 40-100 ℃, and the membrane filtration equipment is a silicon carbide membrane, is a honeycomb coal type inner tubular membrane, and has a membrane pore size of 1, 0.5, 0.1 or 0.04 μm.

5. The method for producing food grade disodium hydrogen phosphate by using industrial wet-purification phosphoric acid as claimed in claim 1, wherein the sodium hydroxide in the step ⑷ is analytically pure or chemically pure solid sodium hydroxide.

6. The method for preparing food grade disodium hydrogen phosphate by using industrial wet-purification phosphoric acid as claimed in claim 1, wherein the temperature range of the metastable zone of the disodium hydrogen phosphate crystals in the step ⑸ is 30-45 ℃.

7. The method for preparing food grade disodium hydrogen phosphate by using industrial wet-purification phosphoric acid as claimed in claim 1, wherein the required moisture content in step ⑹ is less than or equal to 2% by mass.

Technical Field

The invention relates to the technical field of food additive processing, in particular to a method for preparing food-grade disodium hydrogen phosphate by industrial wet-process phosphoric acid purification.

Background

Disodium hydrogen phosphate is an important chemical raw material and has wide application in industrial departments of biological fermentation, food, medicine, feed, chemical industry, agriculture and the like. The method for producing disodium hydrogen phosphate mainly includes neutralization, extraction, ion exchange, double decomposition, direct method, crystallization, and electrolysis, and the main production method is neutralization. Phosphoric acid can be classified into wet-process phosphoric acid obtained by acidifying phosphate ore as a raw material and hot-process phosphoric acid obtained by burning pure phosphorus as a raw material according to the source of the phosphoric acid used, and thus, disodium hydrogen phosphate can be classified into hot-process disodium hydrogen phosphate and wet-process disodium hydrogen phosphate, wherein the hot-process disodium hydrogen phosphate has high purity but high cost; according to the purity, the disodium hydrogen phosphate can be divided into industrial grade, agricultural grade and food grade, wherein the food grade disodium hydrogen phosphate has the highest quality standard. Food grade disodium hydrogen phosphate is typically manufactured from hot process phosphoric acid via a neutralization process.

The method has the advantages that the method has abundant phosphate ore resources in China, industrial-grade wet-process phosphoric acid and phosphate represented by disodium hydrogen phosphate are prepared by using the phosphate ore as a raw material, the technology is mature, the cost is low, the product quality is stable, the impurity content is high, the purity is low, and the requirement of food grade cannot be met. In contrast, the production of phosphoric acid by a hot process and phosphate represented by disodium hydrogen phosphate using phosphorus as a raw material has a high cost although the technology is mature, the product quality is stable, the purity is high, the impurity content is low, and the requirement of food grade can be met. Therefore, how to utilize rich phosphate rock resources in China to prepare food-grade phosphoric acid and phosphate represented by disodium hydrogen phosphate through wet-process phosphoric acid is economically important and urgent in demand.

The core problems to be solved for preparing the food-grade disodium hydrogen phosphate by using wet-process phosphoric acid (comprising a diluted phosphoric acid semi-finished product with the mass percentage concentration of 20-50% and industrial wet-process purified phosphoric acid with the mass percentage concentrations of 75% and 85%) as raw materials comprise: a. how to separate a small amount of toxic elements such as lead, cadmium, mercury and arsenic in industrial wet-process phosphoric acid to ensure that the product meets the necessary sanitary and safety requirements of food additives; b. how to separate fluorine, iron, calcium and other conventional elements in the industrial wet-process phosphoric acid to ensure that the product reaches the corresponding quality limit index; c. how to separate solid particles, pigment particles and the like in industrial wet-process phosphoric acid to ensure that each index of a product reaches corresponding quality requirements. A large number of researchers at home and abroad research the process technology for preparing food-grade phosphoric acid by refining and purifying wet-process phosphoric acid and preparing food-grade phosphate represented by disodium hydrogen phosphate by taking the wet-process phosphoric acid as a raw material, and a batch of new processes, new technologies and new achievements are brought forward. For example, Hubei Sanning chemical company develops a new technology which is mainly characterized by extracting wet phosphoric acid from melamine, back-extracting and potassium chloride potassizing to obtain food-grade potassium dihydrogen phosphate, and is industrialized. Chinese patent CN201210473441.4 discloses a preparation method of disodium hydrogen phosphate dodecahydrate; chinese patent CN201510606518.4 discloses a method for preparing disodium hydrogen phosphate by separating impurities through ammoniation by using wet-process phosphoric acid; chinese patent CN200910102800.3 discloses a method for preparing food-grade disodium hydrogen phosphate by directly neutralizing and concentrating dilute phosphoric acid; chinese patent CN86101186.4 discloses a method for preparing potassium dihydrogen phosphate by an "association-displacement" method; US7601319 discloses a process for the production of monopotassium phosphate.

How to remove toxic and harmful components in industrial wet-process purified phosphoric acid with high efficiency and low cost and improve the purity of disodium hydrogen phosphate to meet the sanitary and safety requirements of food additives is a core technical problem of preparing food-grade disodium hydrogen phosphate by industrial wet-process purified phosphoric acid and is a fundamental development direction for improving economic benefits in the wet-process phosphoric acid industry.

Disclosure of Invention

Aiming at the defects that the disodium hydrogen phosphate prepared by industrial wet-process purified phosphoric acid cannot meet the food-grade requirement and the prior art has the defects, the invention aims to provide the method for preparing the food-grade disodium hydrogen phosphate which has the advantages of low cost, high purity, full removal of arsenic and heavy metal ions, high sanitary safety, simple and convenient process, high raw material utilization rate, good dissolving performance and mechanized production.

The technical concept of the invention is as follows: the method comprises the steps of utilizing the salting-out effect that sulfate ions and fluoride ions in industrial wet-process purified phosphoric acid are easier to generate barium fluosilicate and barium sulfate precipitates and sodium dihydrogen phosphate under the weak acid condition and simultaneously carrying out defluorination and desulfurization, arsenite can be oxidized into insoluble arsenate, heavy metal ions generate insoluble precipitates under the neutral alkali condition, phosphoric acid is neutralized into the property that the solubility of disodium hydrogen phosphate and disodium hydrogen phosphate with larger solubility changes obviously along with the temperature, adding water to dilute the industrial wet-process purified phosphoric acid, adding a defluorination and desulfurization agent and filtering the filtrate subjected to membrane neutralization and simultaneous defluorination and desulfurization, oxidizing the defluorination and precipitation of heavy metal ions by using an oxidizing agent under the weak alkaline condition, and obtaining the food-grade disodium hydrogen phosphate through pH regulation, concentration, crystallization and drying.

In order to achieve the purpose, the invention adopts the following technical measures:

a method for preparing food-grade disodium hydrogen phosphate by using industrial wet-process purified phosphoric acid comprises the following steps:

⑴ adding water to dilute the phosphoric acid, placing the phosphoric acid into an acid-proof container, adding water with the mass multiple of 0.5-3.1 times of the phosphoric acid under the condition of stirring to obtain a dilute phosphoric acid solution with the mass percentage concentration of 20.7-56.7%, and continuously stirring to obtain the diluted phosphoric acid solution for industrial wet purification.

The industrial wet-process purified phosphoric acid is subjected to defluorination, desulfurization, extraction-back extraction purification treatment and has a mass percentage concentration of 85 percent, and the mass of the industrial wet-process purified phosphoric acid is superior, first-class and qualified products which meet the requirements of HG/T4069 + 2008 industrial wet-process purified phosphoric acid; the water refers to electricityConductivity less than 10^-3s/m reverse osmosis process pure water, ion exchange process pure water, and distillation condensation process pure water.

Preferably, the industrial wet-process purified phosphoric acid is subjected to defluorination, desulfurization and extraction-back extraction purification treatment, and has a mass percentage concentration of 85%, and the mass of the industrial wet-process purified phosphoric acid is a first-class product and a qualified product which meet the requirements of HG/T4069-2008 industrial wet-process purified phosphoric acid; the water refers to the conductivity of less than 10^-3s/m reverse osmosis pure water.

⑵ neutralization reaction and defluorination and desulfurization, ⑴ of the obtained phosphoric acid diluent is put in an acid-proof container, under the condition of stirring, defluorination and desulfurization agent with the mass fraction of 0.1-1% is added, the stirring is continued, the defluorination and desulfurization agent is fully dissolved and fully reacted with the fluorine ions and the sulfate radicals in the phosphoric acid diluent, a reaction mixture is obtained, under the condition of stirring, 20-50% of sodium hydroxide solution by mass percentage concentration is used for neutralizing the reaction mixture until the pH value is 3.9-4.8, the stirring is continued to obtain a neutralization solution, the temperature of the neutralization solution is controlled to be 20-60 ℃, the neutralization solution is precisely filtered by a membrane filtering device, and the precisely filtered neutralization solution is obtained for standby.

The defluorination and desulfurization agent is analytically pure or chemically pure barium carbonate and barium bicarbonate; the sodium hydroxide is analytically pure or chemically pure solid sodium hydroxide; the membrane filtration equipment has the membrane material of silicon carbide, the membrane component is a honeycomb briquette type inner tubular membrane, and the sizes of membrane pores are 1, 0.5, 0.1 and 0.04 mu m.

Preferably, the defluorination and desulfurization agent is analytically pure barium carbonate and barium bicarbonate; the sodium hydroxide is analytically pure solid sodium hydroxide; the membrane filtering equipment has the membrane material of silicon carbide, the membrane component is a honeycomb briquette type inner tubular membrane, and the sizes of membrane pores are 0.1 and 0.04 mu m.

⑶ oxidizing to remove arsenic, slightly alkaline to remove heavy metal and membrane filtering under the condition of continuous stirring, adjusting the pH of the neutralized liquid obtained by the precise filtration of ⑵ to 7.0-8.0 by using a sodium hydroxide solution with the mass percentage concentration of 20-50%, adding an oxidant with the mass fraction of 0.1-4% of the neutralized liquid, heating the mixture to the temperature required by arsenic oxidation and maintaining the temperature, refluxing, preserving heat and oxidizing for 0.5-8 hours under the condition of stirring, then opening cooling water to reduce the temperature of the mixture to 10-50 ℃, continuously stirring for 0.5-10 hours, and precisely filtering by using membrane filtering equipment to obtain the slightly alkaline to remove heavy metal and the oxidized arsenic-removing liquid for later use.

The sodium hydroxide is analytically pure or chemically pure solid sodium hydroxide; the oxidant is analytically pure or chemically pure hydrogen peroxide (hydrogen peroxide) and bleaching powder; the temperature required by the arsenic oxidation is 50-100 ℃; the membrane filtration equipment has the membrane material of silicon carbide, the membrane component is a honeycomb briquette type inner tubular membrane, and the sizes of membrane pores are 1, 0.5, 0.1 and 0.04 mu m.

Preferably, the sodium hydroxide is analytically pure solid sodium hydroxide; the oxidant is analytically pure or chemically pure hydrogen peroxide (hydrogen peroxide); the temperature required by the arsenic oxidation is 70-95 ℃; the membrane filtering equipment has the membrane material of silicon carbide, the membrane component is a honeycomb briquette type inner tubular membrane, and the sizes of membrane pores are 0.1 and 0.04 mu m.

⑷ adjusting the pH and concentrating, adjusting the pH of ⑶ to 8.7-9.7 with sodium hydroxide solution with the mass percentage concentration of 20-50% under the condition of continuous stirring to obtain disodium hydrogen phosphate solution, and concentrating the disodium hydrogen phosphate solution to 40-60% under the conditions of vacuum degree of 0.8-0.99 MPa and temperature of 70-110 ℃ by a forced circulation vacuum concentration method to obtain the disodium hydrogen phosphate concentrated solution for later use.

The purity of the sodium hydroxide is of analytical and chemical purity industrial grade.

Preferably, the sodium hydroxide is of analytical and chemical purity.

⑸ temperature reduction and crystallization, transferring the ⑷ obtained disodium hydrogen phosphate concentrated solution into a crystallization device, crystallizing disodium hydrogen phosphate within the temperature range of a metastable zone of disodium hydrogen phosphate crystals for 1-25 hours, reducing the temperature to 1-30 ℃ at the temperature reduction speed of 1-10 ℃/hour, continuously crystallizing for 1-50 hours until no crystals are generated, carrying out solid-liquid separation on the crystallized mixture to obtain disodium hydrogen phosphate wet crystals and a crystal mother solution of disodium hydrogen phosphate (the crystal mother solution of disodium hydrogen phosphate can be concentrated-crystallized or concentrated-spray dried to obtain agricultural grade disodium hydrogen phosphate which is used as an agricultural sodium phosphate fertilizer), and taking the disodium hydrogen phosphate wet crystals for standby.

The temperature range of the sodium hydrogen phosphate crystallization metastable zone is 30-45 ℃.

Preferably, the temperature range of the metastable zone of the disodium hydrogen phosphate crystal is 25-35 ℃.

⑹ drying the crystal, drying ⑸ wet crystal of disodium hydrogen phosphate with hot air under normal pressure until the water content of the product is required, cooling and packaging to obtain food grade disodium hydrogen phosphate product, and controlling the temperature of the material in the whole process of the step to be less than or equal to 120 ℃.

The required moisture content is less than or equal to 2 percent by mass.

Preferably, the water requirement is less than 2% in percentage by mass.

Compared with the prior art, the method has the advantages and beneficial effects that:

1. the method mainly solves the separation of tiny solid particles (including pigments) in industrial wet-process purified phosphoric acid by filtering through a strong-acid-resistant silicon carbide film, realizes the precipitation and precipitation of main impurities with large contents of fluorine, sulfur and the like in wet-process diluted phosphoric acid by adding a defluorination and sulfur agent under the slightly acidic condition, solves the technical problems and difficulties of the removal of toxic and harmful heavy metals such as arsenic, lead, cadmium and the like in the wet-process diluted phosphoric acid by oxidation and dearsenification, slightly alkaline heavy metal removal and film filtration, and mainly achieves the technical effects of separating impurities, removing toxic and harmful substances and improving the purity of disodium hydrogen phosphate so that the product reaches the food-grade quality requirement. Compared with the prior art, the invention is characterized in that the prior art can only utilize industrial wet-process purified phosphoric acid to prepare the industrial-grade disodium hydrogen phosphate, and the invention realizes the technical breakthrough of directly preparing the food-grade disodium hydrogen phosphate by utilizing the industrial wet-process purified phosphoric acid.

2. Through the technical treatment of the invention, the removal rate of insoluble impurities in industrial wet-process purified phosphoric acid is 100 percent, the removal rate of pigments is more than 95 percent, and the appearance is clear and transparent; the removal rate of main impurities such as fluorine ions, sulfur ions (sulfate ions) and the like is more than 99 percent; the removal rate of toxic and harmful substances such as arsenic, lead, cadmium and the like is more than 99.99 percent; the phosphoric acid retention rate is more than 99.5 percent. Through determination, the obtained food-grade disodium hydrogen phosphate is white crystalline powder or particles, and all indexes of the food-grade disodium hydrogen phosphate meet or exceed the requirements of national food safety standard GB25568-2010 food additive disodium hydrogen phosphate.

3. Low cost, high purity, sufficient removal of arsenic and heavy metal ions, high sanitary safety, simple and convenient process, high utilization rate of raw materials, good solubility, mechanized production and suitability for large-scale and small-scale production.

Drawings

FIG. 1 is a process flow diagram for manufacturing food grade disodium hydrogen phosphate from industrial wet-cleaned phosphoric acid.

Detailed Description

The applicant shall now describe the process of the present invention in further detail with reference to specific examples.