WO2013091367A1

WO2013091367A1 - Hydrochloric acid technology for producing food-grade phosphoric acid

Info

Publication number: WO2013091367A1
Application number: PCT/CN2012/077645
Authority: WO
Inventors: 杨站平
Original assignee: 凯恩德利(北京)科贸有限公司
Priority date: 2011-12-23
Filing date: 2012-06-27
Publication date: 2013-06-27
Also published as: CN102515134A; JO3135B1; CN102515134B

Abstract

Disclosed is a hydrochloric acid technology for producing food-grade phosphoric acid. Based on a hydrochloric acid acidolysis process, heavy metal impurities are removed by means of a preliminary impurity removal process and a subsequent impurity removal process. Meanwhile, tributyl phosphate with simple composition and stable properties is used as an extraction agent to complete an extraction process. The extraction effect is desirable, and in combination with a back extraction process of diluted hydrochloric acid, the utilization rate of the extraction agent is high. The entire extraction and back extraction process can be completed at a room temperature and are especially suitable for preparing food-grade phosphoric acid in industrial production. A liquid-liquid extraction technology is highly controllable and has high extraction and impurity removal rates; the H₃PO₄ content accounts for more than 75wt% of the end phosphoric acid product. The phosphoric acid has good quality and can be used in the food industry without being purified. The present invention is applicable to both lean phosphate ore and rich phosphate ore.

Description

Production process of hydrochloric acid method for food grade phosphoric acid

Technical field

The invention relates to a production process of high-purity phosphoric acid, in particular to a hydrochloric acid production process for food grade phosphoric acid used in the food industry, and belongs to the field of chemical product processing.

Background technique

Phosphoric acid is an important chemical raw material widely used in the fertilizer industry, food industry, water treatment industry, electronics industry, coatings industry and other fields. Food grade phosphoric acid is also an inexpensive sour agent and is widely used as a food additive in the production of dairy products, meat products, aquatic products and various beverages. Food grade phosphoric acid is in great demand both domestically and internationally, but preparation methods have been relatively backward.

The preparation of food grade phosphoric acid is generally based on thermal phosphoric acid or wet process phosphoric acid. The thermal phosphoric acid uses a two-step process in which yellow phosphorus is first produced in an electric furnace, and then the yellow phosphorus is oxidized and hydrated in a phosphoric acid plant to obtain a finished phosphoric acid. The thermal acid phosphoric acid has a large energy consumption and a high comprehensive cost, so this method is less applied. A typical wet-process phosphoric acid is the decomposition of phosphate rock with sulfuric acid, and the resulting phosphoric acid slurry is subjected to solid-liquid separation to obtain phosphoric acid and calcium sulfate. Wet-process phosphoric acid generally requires that the content of P ₂ 0 ₅ in the phosphate rock is higher than 30%, and the fluctuation of the content of P ₂ 0 ₅ cannot exceed 0.3% to 0.5%, and the fluctuation of harmful impurities such as aluminum, iron, magnesium, etc. is also limited, and A large amount of phosphogypsum is produced in the sulfuric acid production process, which is difficult to recycle and occupies a large area after discharge, which is not conducive to environmental protection and recycling.

In recent years, there has been a method of producing phosphoric acid by using hydrochloric acid instead of sulfuric acid to decompose medium and low grade phosphate rock. For example, a method for producing industrial phosphoric acid by decomposing medium and low grade phosphate rock by hydrochloric acid disclosed in Chinese Patent No. 200510019049.2, which decomposes phosphate rock with hydrochloric acid, prepares calcium chlorophosphate, and then dissolves it with hydrochloric acid, extracts and concentrates with tributyl phosphate. Then, it is extracted with tributyl phosphate and isopropyl ether, stripped, concentrated, and decolorized to prepare 85% industrial grade phosphoric acid. The method has the disadvantages of large equipment investment, low impurity removal efficiency, high risk and high energy consumption, which is not conducive to large-scale industrial production. Another method for producing industrial phosphoric acid, industrial ammonium phosphate and food grade phosphoric acid from medium and low grade phosphate rock by a hydrochloric acid method as disclosed in Chinese Patent No. 201110006702, which is to decompose 1^0 ₅ ≥ 6^% phosphate rock by hydrochloric acid. Firstly prepare calcium dihydrogen phosphate CaClH ₂ P0 ₄ · H ₂ 0 (abbreviated as P-01) and then add diluted phosphoric acid, filter and purify P-01, then dissolve with hydrochloric acid, extract and concentrate with tributyl phosphate. , decolorization of industrial phosphoric acid, addition of ammonia to industrial ammonium phosphate, or concentrated industrial phosphoric acid plus P ₂ S ₅ Dephosphorization and de-heavy metals are decolorized and oxidized by activated carbon and hydrogen peroxide, respectively, to obtain food grade phosphoric acid. In practice, the method has disadvantages such as difficulty in filtration and poor washing effect, and no industrialized production has been achieved so far.

How to solve the industrial processing of food grade phosphoric acid, further improve the processing method and improve the processing quality have become the primary problems to be solved by the present invention.

Summary of the invention

The invention aims to provide a hydrochloric acid production process which is simple in process, convenient in operation, high in quality and low in cost, and can efficiently realize industrialized production of food grade phosphoric acid.

The main difference between food grade phosphoric acid and industrial phosphoric acid is that food grade phosphoric acid has high purity and low impurity content, especially the content of heavy metals such as arsenic and lead are strictly controlled. In order to adapt to industrial production, phosphoric acid requires excellent controllability and high stability in the extraction process, and is especially suitable for long-term use. Therefore, the center of the present invention is: pre-pre-decontamination and post-depletion processes are used as means to remove heavy metals in batches and time-sharing, so that the impurity content in the finished phosphoric acid is sufficiently reduced, and at the same time, suitable industrial production and groups are adopted. The extraction is carried out with a relatively simplified extractant to ensure long-term, stable and efficient extraction, until the industrial production of food grade phosphoric acid is completed.

The present invention is further described in detail below:

The hydrochloric acid production process of the food grade phosphoric acid according to the present invention comprises the following steps:

Step 1 Preparation of raw materials: Using P ₂ 0 ₅ >5 wt% of phosphate-poor or phosphate-rich ore as raw material, crushing to 20 mesh or more, forming phosphate rock powder, and sending it to the acid hydrolysis section through the weight belt to ensure the feeding The rate is stable and reliable.

Using phosphate-poor or phosphate-rich ore as raw material, the applicability of the phosphoric acid production process is improved, the raw materials are widely used, the production cost is effectively reduced, and the processing process is simplified.

Step two acid hydrolysis: using hydrochloric acid as a solvent, the prepared phosphate rock powder is acid-dissolved with 15 _W t%~35 _W t% hydrochloric acid under stirring, and the molar ratio of hydrochloric acid is the total conversion of calcium in the phosphate rock powder. The theoretical amount of hydrogen chloride required for calcium chloride is 95% to 110%, and the acid hydrolysis reaction time is controlled to 15 to 45 minutes.

Usually, the mass percentage of hydrochloric acid is 20-25%, the optimum mass percentage of hydrochloric acid is 23%, the acid hydrolysis reaction time is 30 minutes, and the hydrochloric acid dosage is 105% of the theoretical amount.

A slight excess of hydrochloric acid during the acid hydrolysis process not only facilitates the full acid hydrolysis of the phosphate rock, but also facilitates the extraction of phosphoric acid during subsequent extraction. In the acid hydrolysis process, the concentration and amount of hydrochloric acid should be strictly controlled to produce as many composite compounds as Ca ₄ AlSiS0 ₄ F ₁₃ 43H ₂ 0 in the acid hydrolysis process to effectively remove fluorine, aluminum and soluble silicon in the system. Impurities such as sulfur reduce the difficulty of removing impurities in the later stage.

Since the material formed by the decomposition of phosphate rock by hydrochloric acid is substantially free of scale-prone components, the material is easy to transport and handle, It is also not easy to block the pipeline during the production process, which greatly facilitates the production process and is easy to realize industrial production.

Step 3 pre-removal: 6 _W t%~12 _W t% Na ₂ S solution is added to the process liquid after acid hydrolysis for pre-decontamination, and the Na ₂ S solution is added in an amount of 2% to 4% of the volume of the process liquid. .

Pre-decontamination is mainly to remove As and Pb contained in the process liquid. After reacting with arsenic and lead to form a precipitate, sodium sulfide can be removed by filtration. The reaction process is as follows:

As ⁵⁺ +S ² "→As ₂ S ₅ i

As ³⁺ +S ² "→As ₂ S ₃ ^

Pb ²⁺ +S ² "→PbS i

Typically, the Na ₂ S solution has a mass percentage of 6% and is added in an amount of 3% by volume of the process liquid. Before the extraction process, the impurities are first reduced to a relatively low level, which greatly reduces the occurrence of subsequent emulsification, which is beneficial to the smooth and in-depth extraction process.

Step 4: Adding flocculant to the process liquid after decontamination, the flocculant is a polyacrylamide solution with a molecular weight of more than 10 million Daltons, the flocculant concentration is 0.05wt%~0.2wt%, and the flocculant dosage is 1% to 3% of the volume of the process liquid, and the solid impurities are precipitated and filtered to obtain a filtrate after the desired pretreatment.

Step 5: Extracting iron: The filtrate is subjected to countercurrent extraction with an extractant. The extractant is composed of N235 (mixed tri-fatty amine), isooctanol and kerosene. N235: isooctyl alcohol: kerosene is 15% to 18% by volume: 15 ~18 : 64%~70%; The ratio of extractant to filtrate is 1:1, the extraction temperature is 15~45 °C, and the raffinate water phase is iron-deficient phosphoric acid.

N235 is an alkaline extractant, which is a mixed tribasic amine mainly composed of C8~C10. N235 can extract Fe ³⁺ which is combined with C1 to form an anion in chloride solution. The iron extraction ability is extremely strong, and the compounding process is :

R ₃ N+HC1=R ₃ NHC1

Fe+4Cl = (FeCl ₄ )"

R ₃ NHCl+(FeCl ₄ ) = R ₃ NHFeCl ₄ +Cl"

Kerosene is an inert solvent that does not chemically combine with the extract as a diluent. It is used to improve the physical properties of organic matter and control the extraction ability of the extractant during the extraction process. Isooctyl alcohol is used as an additive to increase N235. Solubility in kerosene ensures reliable extraction.

Among them, according to the volume percentage, the optimum ratio of the components of the extractant N235: isooctanol: kerosene = 15%: 15%: 70%, which has a good removal effect on iron, and the loss rate of phosphorus is very low. .

In the above steps, the extraction phase produced by the extraction process can also be back-extracted with pure water. The volume percentage of the pure water and the extracted phase is 1:2, and the organic phase obtained by the stripping is the regenerated extractant, and returns to step 5 again. The extraction and iron removal improve the efficiency of the filtrate and reduce the production loss. Step 6 extraction: using a mixed solvent of tributyl phosphate and kerosene as an extractant, at least ten extractions of iron-diluted phosphoric acid, the volume ratio of kerosene and tributyl phosphate is 1:1~2, and the extraction temperature is 15~ At 45 ° C, the volume ratio of the aqueous phase to the extracted phase is 1:3 to 5, and the phosphoric acid in the process liquid after the extraction enters the organic phase, and the impurities and free hydrochloric acid remain in the aqueous phase.

Compared with the mixed extractant composed of tributyl phosphate + other extractant + kerosene used in the previous process, it is affected by the different water solubility of other extractants and tributyl phosphate. In the long-term production, the prior process will have a proportional imbalance. It is not easy to control the shortcomings of the ratio and cannot be suitable for large-scale industrial production. In this step, kerosene is a diluent, tributyl phosphate is an extractant, and phosphoric acid is extracted by using a mixed solvent of tributyl phosphate + kerosene, the extracting agent itself is hardly soluble in water, the ratio is easy to control, and the extraction effect is good, the process Simple, it can be used for stable extraction for a long time. At the same time, the extraction process is carried out at a normal temperature of 15~45 °C, which can reduce energy consumption and dependence on the environment, reduce the investment of the pre-production cost, and simplify the production process.

Of course, in order to achieve comprehensive utilization, the raffinate phase in the extraction process can also be treated with CaCl ₂ , and the CaC # liquid of the raffinate phase can be used as an industrial raw material to produce desiccant and antifreeze after being neutralized, filtered, spray dried and separated. Products such as preservatives and preservatives also avoid the generation of large amounts of gypsum in the sulfuric acid phosphoric acid, which brings difficulties to the discharge process.

Step 7 Washing: The extracted organic phase is subjected to at least five stages of washing with a 10 wt% to 18 wt% dilute phosphoric acid solution. When washing, the volume ratio of the aqueous phase: organic phase is 1:120 to 30.

Step 8 reverse extraction: The washed organic phase is subjected to at least five-stage stripping with 0.5 wt% to 1.5 wt% of dilute hydrochloric acid. The aqueous phase in the stripping: organic phase = 1:10~15, the aqueous phase after stripping is Dilute phosphoric acid. In order to further improve the efficiency, the organic phase after stripping can also be subjected to at least five-stage stripping with pure water. The volume ratio of pure water to organic phase is 1:2, and the organic phase after stripping with pure water is returned to step 6 and continue to be used. For extraction.

In this step, the stripping section is stripped with phosphoric acid by dilute hydrochloric acid. Because of the high content of chloride ions in the aqueous phase, impurities such as As and F are present in the organic phase, and are back-extracted when stripping with pure water. Effectively removes impurities such as As and F contained therein, and reduces the impurity content. The organic phase after stripping with pure water can be reused for extraction without separate recovery. The loss rate of the extractant is less than 0.1%, which improves the utilization rate of the extractant and reduces the production cost.

Since the acid is added to both the washing section and the stripping section during the extraction process, the extraction rate of the extraction process and the by-products are greatly improved. &. ₁₂ raffinate aqueous phase, a very low content of phosphoric acid, lime milk and then recovered without wherein P ₂ 0 _5.

Step 9 impurity removal: 6 _W t%~12 _W t% Na ₂ S solution is added to dilute phosphoric acid obtained by stripping hydrochloric acid for secondary decontamination, and the Na ₂ S solution is added in an amount of 1% of dilute phosphoric acid volume. ~4%, then adsorbed by activated carbon, and then filtered with a precision filter.

This step can reduce the content of impurities in dilute phosphoric acid, especially the content of heavy metals As and Pb, to meet the requirements of food grade phosphoric acid.

Step ten oxidation: 30% by weight of hydrogen peroxide is added to the dilute phosphoric acid after secondary decontamination, and the amount of hydrogen peroxide added is dilute phosphorus The acid volume is 0.3% to 0.5% to remove the oxides contained in the dilute phosphoric acid.

Step 11 Evaporation and concentration: Preheat the oxidized dilute phosphoric acid, and evaporate and concentrate to obtain phosphoric acid containing H ₃ P0 ₄ 75 wt% or more. After evaporation of the recovered hydrochloric acid, return to step 2 and continue to be used for acid hydrolysis. Dissolving.

The evaporator used can use graphite evaporator, which has high thermal conductivity and good corrosion resistance. The recycling of hydrochloric acid reduces waste of resources and saves production costs.

Step 12 Decolorization and Filtration: After cooling the concentrated phosphoric acid, decolorization and filtration treatment of activated carbon is carried out to obtain a food grade phosphoric acid containing H ₃ P0 ₄ 75 wt% or more.

Throughout the whole process, the removal of heavy metals such as arsenic and lead in the pre-production and subsequent stages with Na ₂ S solution is carried out in a step-by-step manner. The removal process is simple, reliable and effective, and effectively controls the impurity content in the finished phosphoric acid. In the acid hydrolysis and stripping process, a slight excess of hydrochloric acid is added, which not only facilitates the full acid hydrolysis of the phosphate rock, but also facilitates the subsequent extraction of phosphoric acid and improves the extraction rate; the extractant tributyl phosphate is used. It is hardly soluble in water, simple in composition, stable in performance, good in extraction effect and high in utilization rate. The extraction process at normal temperature has low environmental requirements and is especially suitable for long-term industrial extraction. Its liquid-liquid extraction process has strong controllability, high extraction and impurity removal rate, and the content of H ₃ P0 ₄ in the finished phosphoric acid reaches over 75wt%. It has good quality and can be used in the food industry without purification. It is rich in phosphate rock or rich in phosphorus. Mines are available.

DRAWINGS

1 is a structural flow chart of a hydrochloric acid production process of the food grade phosphoric acid according to the present invention.

detailed description

The hydrochloric acid production process of the food grade phosphoric acid according to the present invention is as shown in Fig. 1. First, the phosphate rock is pulverized and then hydrochloric acid is added for acid hydrolysis, and the Na ₂ S solution is added during the acid hydrolysis to pre-deplete the impurities. Containing heavy metal elements such as arsenic and lead to reduce the impurity content; then, adding a flocculant to the process liquid for filtration to remove solid impurities contained in the process liquid; after recovering the filtrate, extracting the filtrate with an extractant to remove iron, and extracting The aqueous phase is dephosphorized iron; the extract phase is stripped with pure water, and the organic phase obtained after stripping is returned to the iron removal process; then, the iron-diluted phosphoric acid is extracted, and the raffinate phase can be removed to CaCl ₂ The treatment device is treated, the organic phase is washed with dilute phosphoric acid and then stripped with dilute hydrochloric acid to prepare a dilute phosphoric acid solution. After the stripped organic phase is stripped again with pure water, the organic phase is returned to the extraction process for reuse; stripping of the resulting solution was diluted phosphoric acid solution of Na ₂ S impurity and activated carbon adsorption and precision filtration, removal of hydrogen peroxide readily oxidizable, and concentrated by evaporation It was obtained after containing H ₃ P0 ₄ 75wt% or more of the phosphoric acid solution, concentrated by evaporation process for recovering hydrochloric acid solution also return; Finally, the resulting phosphoric acid solution decolorized, filtered, to obtain Phosphoric acid. Example 1

Take 200 g of phosphorus-depleted ore containing about 20% of P ₂ 0 ₅ , pulverize to 20 mesh or more and then add to the beaker; add 23 wt% of hydrochloric acid 400 ml and a part of water, react for 20 minutes under stirring, and then add 6 wt% of Na. 14ml of ₂ S solution was pre-depleted, then added with 0.1% of flocculant 10ml flocculation and sedimentation, and then filtered with filter paper; with volume percentage N235: isooctanol: kerosene = 15%: 15%: 70% mixed solvent pair The filtrate is extracted and de-ironed, the extraction temperature is 20~30 °C, the extraction phase: water phase=1: 1, the obtained raffinate water phase is the iron-reduced phosphoric acid; then, the mixed solvent of tributyl phosphate and kerosene is used as the extraction The agent extracts ten times of iron-diluted phosphoric acid, the extraction temperature is 20-30 ° C, according to the volume ratio, tributyl phosphate: kerosene = 1: 1, the aqueous phase during extraction: organic phase = 1:4; then, The extracted organic phase is subjected to five-stage washing with a 15 wt% dilute phosphoric acid solution, and the aqueous phase is washed: organic phase = 1:25; then, the organic phase is subjected to five-stage stripping with 1 wt% of dilute hydrochloric acid, and stripping is obtained. The aqueous phase is a dilute phosphoric acid solution, and the aqueous phase during stripping: organic phase = 1:10, organic phase after stripping For five stripping with water, the organic phase may be returned to the extraction process of recycling, the use of water during stripping water phase: organic phase = 1: 10; Subsequently, addition of 6 _W t in a dilute phosphoric acid solution 4ml of % Na ₂ S solution for impurity removal; adding 5g of activated carbon to dilute phosphoric acid to remove the organic matter; filtering with filter paper; adding 1ml of 30% hydrogen peroxide to remove easy oxides in dilute phosphoric acid; Evaporation and concentration were carried out, and the evaporation temperature was 158 ° C; lg activated carbon was added to dilute phosphoric acid cooled to room temperature, and the mixture was decolorized by stirring, and then filtered through a sand core funnel to obtain 56.4 g of a colorless transparent finished phosphoric acid. This experiment was repeated three times, the second and the first time being identical; in the third and fourth experiments, the Na ₂ S solution was not added to the reaction process for pre-depuration, and the remaining steps were identical.

According to GB 3149-2004 "Food Additives - Phosphoric Acid", phosphoric acid as a food additive should meet the requirements of the following table:

For the tetra-component phosphoric acid prepared in this example, the content of H ₃ P0 ₄ was determined by gravimetric method, the content of F was determined by the standard curve method, the content of As and Pb was determined by ICP-MS, and the easy oxide was determined by titration. (in terms of H ₃ P0 ₃ ). After the determination, the first group and the second group of products reached the food grade, and the third group and the fourth group of products which were not pre-depleted by adding Na ₂ S solution during the reaction did not reach the food grade standard. The specific data are as follows: Finished product quality H3PO4 F— As Pb H3PO3 Group 1 56.5g 83.2% 0.0005% 0.00004% 0.0004% 0.007%

The second group 56.0g 83.6% 0.0007% 0.00003% 0.0003% 0.009%

The third group 56.3g 84.5% 0.0009% 0.00008% 0.0006% 0.010%

The fourth group 56.1g 85.3% 0.0008% 0.00007% 0.0007% 0.009%

It can be seen that the pre-depuration with Na ₂ S solution in the acid hydrolysis process can effectively ensure that the impurity content of the finished phosphoric acid is at a lower level, and the impurity content of the finished phosphoric acid without pre-depletion is obvious. High. This indicates that pre-doping during the reaction can effectively reduce the impurity content in the finished phosphoric acid. Example 2

The pulverized 100 kg of phosphate rock powder, P ₂ 0 ₅ content is about 20%, put into the reaction tank, add 0.2m ³ of hydrochloric acid with a mass fraction of 23% for acid hydrolysis, and react for 20 minutes under stirring to add 7L. Pre-depletion of 6% Na ₂ S solution, then adding 0.1% of flocculant 3.5L flocculation precipitate, and then filtering; using volume percentage, N235: isooctanol: kerosene = 15%: 15%: 70% mixed solvent extracts the filtrate to remove iron, the extraction temperature is 20~30 °C, the extraction phase: water phase = 1: 1, the resulting raffinate water phase is iron-reduced phosphoric acid; then, by volume ratio, phosphoric acid Butyl ester: kerosene = 1:1 mixed solvent for ten-stage extraction of iron-diluted phosphoric acid, extraction temperature is 20~30 °C, aqueous phase during extraction: organic phase = 1: 5; 10 for extracting organic phase _W t% dilute phosphoric acid solution is subjected to five-stage washing, and the aqueous phase is washed: organic phase = 1:20; the organic phase is subjected to five-stage stripping with l _W t% of dilute hydrochloric acid to obtain a dilute phosphoric acid solution, and the aqueous phase is stripped. : Organic phase = 1:10; the organic phase after stripping is subjected to five-stage stripping with water, and the organic phase obtained by stripping is reused for extraction. Process, when stripping with pure water phase: organic phase = 1: 10; 5L added mass fraction in a dilute phosphoric acid solution back-extracted with dilute hydrochloric acid obtained in the impurity removal 6% solution of Na ₂ S, and then fed to impurity The can removes the organic matter in the dilute phosphoric acid; then removes 30% of 30% hydrogen peroxide in the dilute phosphoric acid to remove the easy oxide, and sends it to the evaporator for evaporation and concentration, and the evaporation temperature is 158 ° C to 164 ° C; After cooling, it was decolorized by a decolorizing tower, and then filtered to obtain a colorless and transparent finished phosphoric acid of 28.4 kg. This pilot test was repeated twice, the second and the first time all the steps were exactly the same, the third time in the extraction process using deionized water instead of dilute hydrochloric acid to strip the organic phase, the remaining steps are exactly the same as the first time.

According to GB 3149-2004 "Food Additive - Phosphoric Acid", for the three-component phosphoric acid prepared in this example, the content of H ₃ P0 ₄ was determined by gravimetric method, the content of F was determined by standard curve method, and As was detected by ICP-MS. The content of Pb was determined by titration to determine the content of oxides (as H ₃ P0 ₃ ). It was determined that the first two groups of products reached the food grade, and the F and As contents in the third group exceeded the standard and did not reach the food grade. The specific data is as follows: Finished product quality H3PO4 F— As Pb H3PO3 Group 1 27.4kg 85.7% 0.0008% 0.00004% 0.0004% 0.009%

The second group 27.5kg 0.0007% 0.00004% 0.0003% 0.011%

The third group 27.9kg 86.3% 0.0011% 0.00007% 0.0004% 0.008%

It can be seen that in the extraction process, the organic phase is stripped with dilute hydrochloric acid instead of deionized water, so that the impurities in the finished pity acid can be contained.

0

The amount is at a lower level. This shows that the use of dilute hydrochloric acid to extract the organic phase is better.

Claims

1. A hydrochloric acid production process for food grade phosphoric acid, characterized in that it comprises the following steps:

(1) Preparation of raw materials: using P ₂ 0 ₅ > 5 wt% of phosphate-poor or phosphate-rich ore as raw material, pulverizing to above 20 mesh to form phosphate rock powder;

(2) Acid hydrolysis: The prepared phosphate rock powder is acid-dissolved with 15 _W t%~35 _W t% hydrochloric acid under stirring. The molar ratio of hydrochloric acid is the conversion of calcium in the phosphate rock powder to calcium chloride. 95%~110% of the theoretical amount of hydrogen chloride required, and the acid hydrolysis reaction time is 15~45 minutes;

(3) Pre-decontamination: 6 _W t%~12 _W t% Na ₂ S solution is added to the process liquid after acid hydrolysis for pre-decontamination, and the Na ₂ S solution is added in an amount of 2% to 4 of the volume of the process liquid. %;

(4) Filtration: flocculating the flocculant into the process liquid after the impurity removal, and filtering to obtain the desired filtrate;

(5) Extracting iron: The filtrate is subjected to countercurrent extraction with an extractant consisting of N235, isooctanol and kerosene; the ratio of the extractant to the filtrate is 1:1, and the extraction temperature is 15 to 45 °C. , the raffinate water phase is iron thinning phosphoric acid;

(6) Extraction: using a mixed solvent of tributyl phosphate and kerosene as an extractant, at least ten extractions of iron-diluted phosphoric acid, the volume ratio of kerosene and tributyl phosphate is 1:1~2, and the extraction temperature is 15 〜45 ° C, the phosphoric acid in the process liquid after the extraction into the organic phase, the impurities and free hydrochloric acid remain in the aqueous phase, the volume ratio of the aqueous phase and the extract phase is 1:3~5;

(7) washing: the extracted organic phase is washed with 10 wt% ~ 18 wt% of dilute phosphoric acid solution for at least five stages, washing, the volume ratio of the aqueous phase: organic phase = 1: 20~30;

(8) Stripping: The washed organic phase is subjected to at least five stages of stripping with 0.5% by weight to 1.5% by weight of dilute hydrochloric acid. The aqueous phase during stripping: organic phase = 1:10~15, water after stripping The phase is dilute phosphoric acid;

(9) impurity removal: adding Na ₂ S solution to the dilute phosphoric acid obtained by stripping for secondary decontamination and adsorption by activated carbon, and then filtering with a precision filter;

(10) Oxidation: adding hydrogen peroxide to remove the easy oxides contained in the dilute phosphoric acid;

(11) Evaporation and concentration: Preheating the oxidized dilute phosphoric acid, and evaporating and concentrating to obtain phosphoric acid containing H ₃ P0 ₄ 75 wt% or more, and recovering the evaporated hydrochloric acid and returning to step (2) for acid hydrolysis Dissolving

(12) Decolorization and filtration: The concentrated phosphoric acid is cooled, and activated carbon decolorization and filtration treatment are carried out to obtain a food grade phosphoric acid containing H ₃ P0 ₄ 75 wt or more.

2 . The hydrochloric acid production process of food grade phosphoric acid according to claim 1 , wherein the hydrochloric acid has a mass percentage of 20% to 25%, the acid hydrolysis reaction time is 30 minutes, and the hydrochloric acid dosage is a theoretical amount of 105. %.

3. The hydrochloric acid production process of food grade phosphoric acid according to claim 1, wherein the flocculating agent is The polyacrylamide solution having a molecular weight of more than 10 million Daltons has a flocculant concentration of 0.05% by weight to 0.2% by weight, and the flocculating agent is used in an amount of 1% to 3% by volume of the process liquid.

The process for producing a food-grade phosphoric acid according to claim 1, wherein in the step (5), N235: isooctyl alcohol: the volume percentage of kerosene is 15% to 18%: 15 to 18 : 64%~70%.

The process for producing a food-grade phosphoric acid according to claim 1, wherein the step (5) further comprises: stripping the extracted phase with pure water, and returning the organic phase obtained by stripping ( 5) Re-use for extracting iron, the volume percentage of the pure water and the extract phase is 1:2, and the organic phase obtained by stripping is a regenerated extractant.

The process for producing a food-grade phosphoric acid according to claim 1, wherein in the step (8), the organic phase after stripping is subjected to at least five-stage stripping with pure water, the pure water. The volume fraction of the organic phase and the organic phase is 1:2, and the organic phase after the stripping is returned to the step (6) to continue the extraction, and the organic phase after the stripping is the regenerated extractant.

The process for producing a food-grade phosphoric acid according to claim 1, wherein in the step (9), 6 wt% to 12 _W % of Na ₂ S is added to the diluted phosphoric acid obtained by stripping. The solution was subjected to secondary decontamination, and the Na ₂ S solution was added in an amount of 1% to 4% by volume of the dilute phosphoric acid.

The process for producing a food-grade phosphoric acid according to claim 1, wherein in the step (10), 30 wt% of hydrogen peroxide is added to the dilute phosphoric acid, and the amount of hydrogen peroxide added is 0.3% of the volume of the dilute phosphoric acid. ~0.5%.