CN102616765A - Method of using composite extracting agent for extraction and refining of phosphoric acid prepared through wet process - Google Patents

Abstract

A method for extracting and refining wet-process phosphoric acid with a composite extractant, the method sequentially includes a pretreatment process, an extraction and refining process, and a post-treatment process, wherein the extracted raw material obtained after the pre-treatment process is concentrated, defluorinated, settled, decolorized, and filtered The solid content in the acid is less than 0.05wt%. The extraction and refining process adopts a compound extractant for countercurrent contact extraction. The composition and weight ratio of the compound extractant are: ketone ether: alcohol: ester = 60–80:15–20:5 -15, the composition and weight ratio of the ketone ether are: ketone:ether=95-60:5-40; the post-treatment process is concentrated, decolorized, desulfurized, concentrated, and filtered to obtain the product industrial 85% phosphoric acid. This design not only has lower requirements for extraction of raw acid and lower production cost, but also has better extraction effect and produces more industrial phosphoric acid products.

Description

A method for extracting and refining wet-process phosphoric acid with a composite extractant

technical field

The invention relates to a method for extracting and refining wet-process phosphoric acid with an extractant, in particular to a method for extracting and refining wet-process phosphoric acid with a compound extractant, which is specifically suitable for extracting and refining the acid by using a compound extractant on the basis of reducing the requirements for the extraction of raw acid. rate increased to 85-90%.

Background technique

At present, there are some domestic existing technologies for extracting and refining wet-process phosphoric acid, but these existing technologies have high requirements for the original acid used in extraction. In order to meet their requirements, it is necessary to import high-grade phosphate rock to produce wet-process phosphoric acid French phosphoric acid, such as Moroccan phosphate rock, or complex pretreatment of domestic wet-process phosphoric acid mainly produced by medium and low-grade phosphate rock. Whether it is imported high-grade phosphate rock or complex pretreatment of wet-process phosphoric acid, the production cost will be greatly increased, and the final extraction effect is also poor, with the extraction rate generally only about 70%.

The Chinese patent number is ZL 200510021984.2, and the invention patent date of authorization announcement is April 4, 2007, which discloses an extraction solvent and its extraction method for the production of food-grade phosphoric acid by wet-process phosphoric acid purification. A liquid mixed extraction solvent formed by mixing a single extraction solvent: tributoxyethyl phosphate: isopropyl ether: cyclohexanol = 1–6:2–5:2–4, the method is a liquid mixed extraction solvent and after The pretreated wet-process phosphoric acid is mixed, vibrated and stratified according to a certain volume ratio. After the vibrating and stratified, the lower raffinate is discharged, and the upper extract is washed and stratified with a small amount of food-grade phosphoric acid. The water after stratification is relatively The upper-grade phosphoric acid is subjected to multi-stage extraction, and then deionized water is used for multi-stage back extraction, and the obtained extracted phosphoric acid is concentrated to obtain food-grade phosphoric acid. Although the extraction rate of wet-process phosphoric acid in this invention can reach 80% on average, it has strict restrictions on the original acid used for extraction: after dearsenic, heavy metal, desulfurized, and defluorinated ortho acid, the concentration of phosphoric acid is more than 70%. Arsenic, heavy metals, sulfate radicals, etc. meet the standards of industrial-grade phosphoric acid. This has very high requirements for extracting the original acid, which will inevitably increase the production cost.

Contents of the invention

The purpose of the present invention is to overcome the defects and problems existing in the prior art that have higher requirements for extracting raw acid, poor extraction effect and high production cost, and provide a kind of A method for extracting and refining wet-process phosphoric acid with a compound extractant with good production cost and low production cost.

For realizing above object, technical solution of the present invention is:

A method for extracting and refining wet-process phosphoric acid with a composite extractant, the method sequentially includes a pretreatment process, an extraction and refining process, and a post-treatment process; the method sequentially includes the following processes:

Pretreatment process: first concentrate the crude phosphoric acid obtained by the wet method until the mass percent concentration of P ₂ O ₅ in the crude phosphoric acid is 45%, and then add Na ₂ CO ₃ to the concentrated crude phosphoric acid for defluorination. The amount of Na ₂ CO ₃ added is calculated based on 100%–120% of the stoichiometric ratio of the free fluoride ion in the crude phosphoric acid after concentration, and then a composite sedimentation agent is added to the crude phosphoric acid after defluorination for sedimentation, and then stirred evenly, after 4 hours of sedimentation The sedimentation acid and the bottom flow slag acid can be obtained. The volume of the sedimentation cleaning acid is 85%-90% of the sum of the crude phosphoric acid after defluorination and the volume of the composite sedimentation agent. The bottom flow slag acid is sent to the fertilizer workshop to make fertilizer, and then Add powdered activated carbon to the settled clear acid for decolorization, the mass volume ratio of the active carbon to the settled clear acid mg/ml is 0.5%-1.5%: 1, and then filter to obtain the extracted original acid, the extracted original acid The solid content in the acid is less than 0.05wt%;

Extraction and refining process: First, the composite extractant and the above-mentioned extraction acid are subjected to countercurrent contact extraction at a ratio of 1:2–4 to obtain a loaded organic phase and raffinate, and then the obtained loaded organic phase is compared with washing water at a ratio of 10 -25:1 for counter-current contact washing to obtain the washed organic phase and raffinate water, then the washed organic phase and distilled water are compared to 6-25:1 for counter-current contact stripping to obtain the stripping liquid and the empty organic phase, and then Reclaiming the extractant to the strip liquid obtained to obtain the strip liquid after recovery; the ratio is the volume ratio of the organic phase to the aqueous phase;

The composition of the composite extractant and its weight ratio are: ketone ether: alcohol: ester = 60-80: 15-20: 5-15, the composition of the ketone ether and its weight ratio are: ketone: ether = 95–60:5–40; said ketone means methyl isopropyl ketone, diisopropyl ketone, diisobutyl ketone, methyl isobutyl ketone or cyclohexanone, said ether means diisopropyl ether Or diisobutyl ether, said alcohol refers to n-butanol, isobutanol, n-pentanol, isoamyl alcohol or cyclohexanol, and said ester refers to tributoxyethyl phosphate or tributyl phosphate;

Post-treatment process: Concentrate the recovered back-extraction liquid obtained above until the mass percentage concentration of H ₃ PO ₄ in the recovered back-extraction liquid is 75%. At this time, 75% phosphoric acid is obtained, and then added to the 75% phosphoric acid Powdered activated carbon is used for decolorization, and then filtered to obtain 75% phosphoric acid after decolorization, and then 100% of the sulfuric acid radical stoichiometry in the 75% phosphoric acid after decolorization is put into barium salt for desulfurization, and then filtered after the sulfate radical content meets the requirements of the national standard , and then concentrate the filtrate until the mass percent concentration of H ₃ PO ₄ in the filtrate is 85%, at this time the product industrial 85% phosphoric acid is obtained.

In the pretreatment process: the volume of the composite sedimentation agent is 1‰-10‰ of the volume of crude phosphoric acid after defluorination, and the composite sedimentation agent is an aqueous solution with a mass percentage concentration of 5%-15%, and its solute is 1: 10–50 mass ratio of nonionic surfactant and anionic surfactant prepared;

The nonionic surfactant is: one of maleic acid-acrylic acid copolymer, acrylamide-methyl acrylate-2-acrylamide-2-methylpropanesulfonic acid copolymer, AM-AA-DMA copolymer Or any two prepared according to the mass ratio of 1:1;

The anionic surfactant is oleyl polyoxyethylene (10) ether phosphate, sodium octyl sulfate, sodium α-alkenyl sulfonate, sodium lignin sulfonate, disodium stearyl sulfosuccinamic acid, lauryl One of ammonium sulfate.

In the extraction and refining process: the raffinate is sent to the fertilizer workshop to produce fertilizer; the washing water is a phosphoric acid solution containing sodium, potassium or ammonium salt, and the raffinate is sent to the phosphate workshop for production after recovering the extractant Phosphate sodium salt, potassium salt or ammonium salt; after the empty organic phase is mixed with the recovered extractant, it is used to prepare a composite extractant for recycling.

In the post-treatment process: the industrial 85% phosphoric acid is defluorinated by silicon dioxide, arsenic and heavy metals are removed by sulfide to obtain food-grade phosphoric acid.

Compared with prior art, the beneficial effect of the present invention is:

1. A method for extracting and refining wet-process phosphoric acid with a compound extractant of the present invention includes three processes of pretreatment, extraction and refining and post-treatment successively. The extraction and refining process adopts a compound extractant to extract, and the compound extractant not only has Its high selectivity, high repellency to metal ions and impurity anions, and a wider allowable concentration range for phosphoric acid extraction can further increase the extraction rate to 85–90%. Among them, “high selectivity to phosphoric acid, The characteristics of "high repulsion of metal ions and impurity anions" make it less demanding for the extraction of raw acid, as long as the solid content in the extracted raw acid is less than 0.05wt%, it can meet the requirements, which greatly simplifies the operation of the pretreatment process and saves The production cost is reduced; the characteristics of "the allowable concentration range of phosphoric acid extraction is wider, and the extraction rate can be further improved to 85-90%" can ensure that the present invention has a better extraction effect, and the phosphoric acid taken away from the extracted raw acid is more More, so as to get more industrial phosphoric acid products. Therefore, the present invention not only has lower requirements for extracting raw acid and lower production cost, but also has better extraction effect and produces more industrial phosphoric acid products.

2. The purpose of the pretreatment process in the method for extracting and refining wet-process phosphoric acid with a compound extractant of the present invention is to prevent solid particles and organic matter from entering the extraction tank, so as to ensure that the solid content in the extracted raw acid is less than 0.05wt%. In the pretreatment process, not only desulfurization and heavy metal removal are not required, but also defluorination does not pursue the defluorination rate. It only needs to reduce the free fluorine appropriately to prevent it from affecting the extraction process and equipment. This greatly simplifies the pretreatment steps and makes It is easier to operate and reduces production costs. Therefore, the present invention not only simplifies the operation steps, but also reduces the production cost.

3. A method for extracting and refining wet-process phosphoric acid with a compound extractant of the present invention requires that the loaded organic phase and washing water be compared to 10-25:1 for countercurrent contact washing, and the washing organic phase and distilled water shall be compared by 6 –25:1 for countercurrent contact stripping, in which, the purpose of “countercurrent contact washing of loaded organic phase and washing water at a ratio of 10–25:1” is to improve the washing ratio under the same washing effect. Reduce the washing loss of phosphoric acid and extractant, so that the product can be as much as possible, and the cost of the product is as low as possible; Compared with high back extraction, the concentration of phosphoric acid in the back extraction liquid can be further increased, which reduces the burden for subsequent evaporation and concentration, and reduces production costs; in addition, in the whole process of extraction and refining process, various intermediate products are taken The saving measures realize the purpose of as many products as possible and the cost as low as possible. Therefore, the present invention not only has more products, but also has lower costs.

4. The method for extracting and refining wet-process phosphoric acid with a compound extractant of the present invention has carried out a desulfurization operation in the post-treatment process. This is to cooperate with the use of a compound extractant in the extraction and refining process. Just because the compound extractant is effective on metal ions, Impurity anions have high repellency, so the present invention does not need desulfurization and heavy metal removal in the pretreatment stage, but puts desulfurization and heavy metal removal in the post-treatment stage, so that the overall process of the present invention is completely different from the prior art; and, Since the desulfurization step is carried out before the end of the overall process, not only one desulfurization can meet the requirements of the national standard for sulfate radicals, the desulfurization effect is better, and the sulfate radical content at this time is also far less than that in the pretreatment stage. Reduced the amount of barium salt used for desulfurization and reduced production costs; in addition, since the indicators of refined phosphoric acid after desulfurization have reached the requirements of the national industrial-grade phosphoric acid standard, and are close to the national standard requirements of food-grade phosphoric acid, such as sulfate ≤ 0.002%, fluorine 0.0007%, iron ≤0.002%, arsenic ≤0.0002%, heavy metal 0.0009%, chloride ≤0.0005%, so only need to add silicon dioxide to defluorinate, sulfide to remove arsenic and remove heavy metals to get food grade phosphoric acid , thereby enriching the types of products and increasing the value of products. Therefore, the present invention not only has a stronger desulfurization effect, but also has a better quality of industrial 85% phosphoric acid, and is easy to produce food-grade phosphoric acid, improving the cost performance of production.

Description of drawings

Fig. 1 is a flow chart of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Referring to Fig. 1, a method for extracting and refining wet-process phosphoric acid with a compound extractant, the method comprises the following processes in turn:

Pretreatment process: first concentrate the crude phosphoric acid obtained by the wet method until the mass percent concentration of P ₂ O ₅ in the crude phosphoric acid is 45%, and then add Na ₂ CO ₃ to the concentrated crude phosphoric acid for defluorination. The amount of Na ₂ CO ₃ added is calculated based on 100%–120% of the stoichiometric ratio of the free fluoride ion in the crude phosphoric acid after concentration, and then a composite sedimentation agent is added to the crude phosphoric acid after defluorination for sedimentation, and then stirred evenly, after 4 hours of sedimentation The sedimentation acid and the bottom flow slag acid can be obtained. The volume of the sedimentation cleaning acid is 85%-90% of the sum of the crude phosphoric acid after defluorination and the volume of the composite sedimentation agent. The bottom flow slag acid is sent to the fertilizer workshop to make fertilizer, and then Add powdered activated carbon to the settled clear acid for decolorization, the mass volume ratio of the active carbon to the settled clear acid mg/ml is 0.5%-1.5%: 1, and then filter to obtain the extracted original acid, the extracted original acid The solid content in the acid is less than 0.05wt%;

Extraction and refining process: First, the composite extractant and the above-mentioned extraction acid are subjected to countercurrent contact extraction at a ratio of 1:2–4 to obtain a loaded organic phase and raffinate, and then the obtained loaded organic phase is compared with washing water at a ratio of 10 -25:1 for counter-current contact washing to obtain the washed organic phase and raffinate water, then the washed organic phase and distilled water are compared to 6-25:1 for counter-current contact stripping to obtain the stripping liquid and the empty organic phase, and then Reclaiming the extractant to the strip liquid obtained to obtain the strip liquid after recovery; the ratio is the volume ratio of the organic phase to the aqueous phase;

The composition of the composite extractant and its weight ratio are: ketone ether: alcohol: ester = 60-80: 15-20: 5-15, the composition of the ketone ether and its weight ratio are: ketone: ether = 95–60:5–40; said ketone means methyl isopropyl ketone, diisopropyl ketone, diisobutyl ketone, methyl isobutyl ketone or cyclohexanone, said ether means diisopropyl ether Or diisobutyl ether, said alcohol refers to n-butanol, isobutanol, n-pentanol, isoamyl alcohol or cyclohexanol, and said ester refers to tributoxyethyl phosphate or tributyl phosphate;

Post-treatment process: Concentrate the recovered back-extraction liquid obtained above until the mass percentage concentration of H ₃ PO ₄ in the recovered back-extraction liquid is 75%. At this time, 75% phosphoric acid is obtained, and then added to the 75% phosphoric acid Powdered activated carbon is used for decolorization, and then filtered to obtain 75% phosphoric acid after decolorization, and then 100% of the sulfuric acid radical stoichiometry in the 75% phosphoric acid after decolorization is put into barium salt for desulfurization, and then filtered after the sulfate radical content meets the requirements of the national standard , and then concentrate the filtrate until the mass percent concentration of H ₃ PO ₄ in the filtrate is 85%, at this time the product industrial 85% phosphoric acid is obtained.

In the pretreatment process: the volume of the composite sedimentation agent is 1‰-10‰ of the volume of crude phosphoric acid after defluorination, and the composite sedimentation agent is an aqueous solution with a mass percentage concentration of 5%-15%, and its solute is 1: 10–50 mass ratio of nonionic surfactant and anionic surfactant prepared;

The nonionic surfactant is: one of maleic acid-acrylic acid copolymer, acrylamide-methyl acrylate-2-acrylamide-2-methylpropanesulfonic acid copolymer, AM-AA-DMA copolymer Or any two prepared according to the mass ratio of 1:1;

The anionic surfactant is oleyl polyoxyethylene (10) ether phosphate, sodium octyl sulfate, sodium α-alkenyl sulfonate, sodium lignin sulfonate, disodium stearyl sulfosuccinamic acid, lauryl One of ammonium sulfate.

In the extraction and refining process: the raffinate is sent to the fertilizer workshop to produce fertilizer; the washing water is a phosphoric acid solution containing sodium, potassium or ammonium salt, and the raffinate is sent to the phosphate workshop for production after recovering the extractant Phosphate sodium salt, potassium salt or ammonium salt; after the empty organic phase is mixed with the recovered extractant, it is used to prepare a composite extractant for recycling.

In the post-treatment process: the industrial 85% phosphoric acid is defluorinated by silicon dioxide, arsenic and heavy metals are removed by sulfide to obtain food-grade phosphoric acid.

Principle of the present invention is described as follows:

Due to long-term disorderly mining, my country's phosphate rock resources have begun to deplete. The grade of phosphate rock is very low, basically low-grade phosphate rock. It cannot meet the requirements of the existing extraction and refining technology, and complex pretreatment (increased cost and operational difficulty) must be carried out before it can be applied to the existing extraction and refining technology. Even so, the extraction effect is often poor, and the extraction rate is only about 70%. . For this reason, it is necessary to design an extraction and refining technology with lower requirements for extracting raw acid, better extraction effect, and lower production cost. A method for extracting and refining wet-process phosphoric acid with a composite extractant of the present invention can meet this goal.

1. About the compound extractant:

The composite extractant used in the present invention not only has high selectivity to phosphoric acid (basically only extracts phosphoric acid, but extracts very little other impurities), high repellency to metal ions and impurity anions, and has a wider extraction tolerance of phosphoric acid The concentration range further increases the extraction rate to 85-90%. These features make the present invention have no too many requirements for extracting the original acid, so as long as the pretreatment process does not allow solid particles and organic matter to enter the extraction tank, it can meet the requirements, that is, the solid content in the extraction original acid is less than 0.05wt%. It is necessary to carry out desulfurization and heavy metal removal in the pretreatment, even if defluorination does not pursue the defluorination rate, which greatly simplifies the pretreatment process.

The above characteristics of the compound extractant come from its unique composition. The composition and weight ratio of the composite extractant are: ketone ether: alcohol: ester = 60-80: 15-20: 5-15, the composition and weight ratio of the ketone ether are: ketone: ether = 95- 60:5–40; the ketone refers to methyl isopropyl ketone, diisopropyl ketone, diisobutyl ketone, methyl isobutyl ketone or cyclohexanone, and the ether refers to diisopropyl ether or diisopropyl ether Isobutyl ether, said alcohol refers to n-butanol, isobutanol, n-pentanol, isoamyl alcohol or cyclohexanol, and said ester refers to tributoxy ethyl phosphate or tributyl phosphate. If the types or proportions of the above ingredients are changed, it will lead to a decrease in the extraction rate (the resulting product is less acidic), a decrease in the effect of extraction and separation of impurities (the quality of the product will be unqualified), which will directly affect the production cost and even affect the production efficiency. went well.

2. About the pretreatment process:

Since the present invention does not have high requirements on the pretreatment process, as long as the solid content in the extracted raw acid is <0.05wt%, the pretreatment process not only reduces the operation difficulty, but also saves the production cost. The whole pretreatment process mainly includes three steps of defluorination, sedimentation and decolorization.

1. About defluorination:

The object of defluorination is only free fluoride ions, and the defluorination rate is not pursued. The reason is that many phosphate fertilizer enterprises use aluminum-containing water treatment agents, or use phosphate rock with high aluminum content to produce wet-process phosphoric acid. The defluorination effect is greatly reduced, so the defluorination process in the present invention does not pursue the defluorination rate. If the defluorination rate is too high, the gain will outweigh the gain. Therefore, it is only necessary to appropriately reduce the free fluorine ion to ensure that it does not affect the extraction process and equipment. , thus simplifying the operation process.

2. Regarding settlement:

The purpose of adopting the composite sedimentation agent in the present invention is to remove solid particles and organic matter in the wet-process phosphoric acid faster and more thoroughly, so as to meet the application requirements of the composite extraction agent. Traditional filtration or natural sedimentation method are all difficult to meet this requirement, for this reason, the present invention adopts composite sedimentation agent to carry out sedimentation, but this does not mean that the pretreatment process among the present invention must adopt this kind of composite sedimentation agent to carry out sedimentation, as long as If the effect of pretreatment can be realized (the solid content in the extracted raw acid is less than 0.05wt%), it meets the application requirements of the composite extractant in the present invention and belongs to the protection scope of the present invention.

3. About decolorization:

The purpose of decolorization is to avoid a large amount of interface dirt due to the extraction of organic matter in the original acid during the extraction and refining process of wet-process phosphoric acid (accumulation of interface dirt will increase the thickness of the interface dirt, and eventually the phase separation cannot be completed, resulting in The extraction process cannot be carried out), which directly affects the extraction process.

3. Extraction and refining process:

1. About comparison:

The purpose of countercurrent contact stripping of the washing organic phase and distilled water at a ratio of 6–25:1 is: higher stripping can further increase the concentration of phosphoric acid in the stripping liquid (for the same volume and the same phosphoric acid content of organic Phase, back extraction with less water, can make the phosphoric acid in the water more concentrated), reduce the burden for subsequent evaporation and concentration, and reduce production costs.

2. Regarding various saving measures:

The raffinate is sent to make fertilizer after recovering the extractant, and there will be no waste liquid discharge.

The composition of the washing water is a phosphoric acid solution of sodium salt, potassium salt or ammonium salt, which can effectively remove the impurity ions in the extracted organic phase, and concentrate the stripping solution to 75% H ₃ PO ₄ to contain impurities other than sulfate radicals. It has reached the national standard requirements for industrial phosphoric acid and is close to the national standard requirements for food acids.

After recovering the extractant, the washing water is sent to the phosphate workshop to produce sodium phosphate, potassium salt or ammonium salt. Taking full advantage of the advantages that the impurity content in the washing water is much lower than that of the original acid and the phosphorus loss is low in the production of phosphate, the production of high added value industrial phosphates.

The extractant recovered from the raffinate and washing water can not only greatly reduce the loss of the extractant, thereby greatly reducing the production cost, but also can be mixed with the empty organic phase to prepare a compound extractant for recycling.

4. Post-processing process:

1. About desulfurization:

In the post-treatment process of the present invention, 100% of the sulfate radical stoichiometry in 75% phosphoric acid after decolorization (too much will cause excessive barium in the product, and less will make the sulfate radical removed uncleanly, thereby the quality is unqualified). Salt desulfurization, one desulfurization can meet the requirements of the national standard for sulfate radicals, and the separated barium sulfate can be sold as a product after washing.

The reason why the desulfurization step is arranged in the post-treatment process rather than in the pre-treatment process as in the prior art is that the composite extractant used in the extraction and refining process has a high selectivity to phosphoric acid, while the sulfate radical is selected It has very little resistance, and the removal of sulfate not only does not hinder the extraction, but also has little effect on the content of sulfate in the extracted organic phase, so desulfurization can be carried out after extraction. At that time, one desulfurization can reach the national standard for sulfuric acid. root requirements. If desulfurization is performed in the pretreatment process, since calcium salt or barium salt is generally used for desulfurization in the prior art, if calcium salt is used, the solubility of calcium sulfate generated after desulfurization in phosphoric acid is relatively large, not only cannot completely remove sulfate radicals, but also It will bring in calcium ions, reduce the quality of phosphoric acid, and hinder the extraction of phosphoric acid by the subsequent composite extractant; if barium salt is used, the content of sulfate in phosphoric acid after defluorination is much greater than that in phosphoric acid after extraction, so it is bound to increase. The consumption of barium salt, and the cost of barium salt is too high again, thereby greatly increases production cost. Therefore, the present invention does not carry out desulfurization after defluorination, which not only simplifies the operation process, but also reduces the cost of desulfurization overall.

2. Regarding the preparation of food-grade phosphoric acid:

Since the composite extractant used in the extraction and refining process has high repellency to metal ions and impurity anions, the extraction of metal ions in the original acid will not affect the extraction of phosphoric acid by the composite extractant. Remove metal ions in the medium, so the present invention places this step in the post-treatment process. At the same time, because the composite extractant has a wider allowable concentration range for phosphoric acid extraction, the extraction rate can be increased to 85-90%, so the post-treatment process The various indicators of refined phosphoric acid after desulfurization have not only met the requirements of the national industrial grade phosphoric acid standard, but also approached the national standard requirements of food grade phosphoric acid, such as sulfate ≤ 0.002%, fluorine 0.0007%, iron ≤ 0.002%, arsenic ≤ 0.0002% , heavy metals 0.0009%, and chloride ≤ 0.0005%. At this time, adding sulfide to remove arsenic and heavy metals, not only the dosage is small and the cost is low, but also food-grade phosphoric acid can be obtained after removing arsenic and heavy metals, which enriches the types of products and improves the production efficiency. the value of the product.

Example 1:

A method for extracting and refining wet-process phosphoric acid with a compound extractant, the method comprises the following processes in sequence:

Pretreatment process: first concentrate the crude phosphoric acid obtained by the wet method until the mass percent concentration of P ₂ O ₅ in the crude phosphoric acid is 45%, and then add Na ₂ CO ₃ to the concentrated crude phosphoric acid for defluorination. The amount of Na ₂ CO ₃ added is calculated based on 100%–120% of the stoichiometric ratio of the free fluoride ion in the crude phosphoric acid after concentration, and then a composite sedimentation agent is added to the crude phosphoric acid after defluorination for sedimentation, and then stirred evenly, after 4 hours of sedimentation The sedimentation acid and the bottom flow slag acid can be obtained. The volume of the sedimentation cleaning acid is 85%-90% of the sum of the crude phosphoric acid after defluorination and the volume of the composite sedimentation agent. The bottom flow slag acid is sent to the fertilizer workshop to make fertilizer, and then Add powdered activated carbon to the settled clear acid for decolorization, the mass volume ratio of the active carbon to the settled clear acid mg/ml is 0.5%-1.5%: 1, and then filter to obtain the extracted original acid, the extracted original acid The solid content in the acid is less than 0.05wt%;

The volume of the composite settling agent is 1‰-10‰ of the volume of crude phosphoric acid after defluorination. The composite settling agent is an aqueous solution with a mass percentage concentration of 5%-15%, and its solute is 1:10-50 by mass ratio Prepared nonionic surfactant and anionic surfactant; the nonionic surfactant is: maleic acid-acrylic acid copolymer, acrylamide-methyl acrylate-2-acrylamide-2-methylpropanesulfonic acid One of copolymer, AM-AA-DMA copolymer or any two prepared in a mass ratio of 1:1; the anionic surfactant is oleyl polyoxyethylene (10) ether phosphate, sodium octyl sulfate, One of sodium α-alkenyl sulfonate, sodium lignin sulfonate, disodium stearyl sulfosuccinamic acid, and ammonium lauryl sulfate;

Extraction and refining process: First, the compound extractant and the above-mentioned extraction acid are subjected to countercurrent contact extraction at a ratio of 1:2 to obtain the loaded organic phase and raffinate, and then the obtained loaded organic phase is compared with the washing water at a ratio of 10:1 Perform countercurrent contact washing to obtain the washed organic phase and raffinate water, then perform countercurrent contact stripping on the washed organic phase and distilled water at a ratio of 6:1 to obtain the stripping solution and the empty organic phase, and then extract the obtained stripping solution Recover the extractant to obtain the stripping solution after recovery; the ratio is the volume ratio of the organic phase to the water phase; the raffinate is sent to the fertilizer workshop to produce fertilizer; the washing water is sodium, potassium or ammonium salt-containing Phosphoric acid solution, the washed water is sent to the phosphate workshop to produce sodium phosphate, potassium salt or ammonium salt after recovering the extractant; after the empty organic phase is mixed with the recovered extractant, it is used to prepare a composite extractant for recycling use;

The composition of the composite extractant and its weight ratio are: ketone ether: alcohol: ester = 75: 15: 10, the composition of the ketone ether and its weight ratio are: ketone: ether = 95: 5; Ketone refers to methyl isopropyl ketone, diisopropyl ketone, diisobutyl ketone, methyl isobutyl ketone or cyclohexanone, said ether refers to diisopropyl ether or diisobutyl ether, and said alcohol refers to Butanol, isobutanol, n-pentanol, isoamyl alcohol or cyclohexanol, the ester refers to tributoxyethyl phosphate or tributyl phosphate;

Post-treatment process: Concentrate the recovered back-extraction liquid obtained above until the mass percentage concentration of H ₃ PO ₄ in the recovered back-extraction liquid is 75%. At this time, 75% phosphoric acid is obtained, and then added to the 75% phosphoric acid Powdered activated carbon is used for decolorization, and then filtered to obtain 75% phosphoric acid after decolorization, and then 100% of the sulfuric acid radical stoichiometry in the 75% phosphoric acid after decolorization is put into barium salt for desulfurization, and then filtered after the sulfate radical content meets the requirements of the national standard , and then concentrate the filtrate until the mass percent concentration of H ₃ PO ₄ in the filtrate is 85%, at this time the product industrial 85% phosphoric acid is obtained.

Example 1 extraction result: extraction rate 85%; product quality: H ₃ PO ₄ content 85.7%, sulfate ≤ 0.002%, fluorine 0.0007%, iron ≤ 0.002%, arsenic ≤ 0.0002%, heavy metal 0.0009%, chloride ≤ 0.0005 %.

Food-grade phosphoric acid can be obtained after 85% of the industrial phosphoric acid is defluorinated by silicon dioxide, arsenic and heavy metals are removed by sulfide.

Example 2:

Step is with embodiment 1, and difference is:

Extraction and refining process: Composite extractant and the above-mentioned extraction acid are used for countercurrent contact extraction at a ratio of 1:3, and the ratio of the loaded organic phase to the washing water is 20:1 for countercurrent contact washing, and the ratio of the washed organic phase to the distilled water is 25: 1. Carry out countercurrent contact stripping; the composition of the composite extractant and its weight ratio are: ketone ether: alcohol: ester=65: 20: 15, and the composition of the ketone ether and its weight ratio are: ketone: ether =60:40;

Example 2 extraction result: extraction rate 87%; product quality: H ₃ PO ₄ content 85.5%, sulfate ≤ 0.002%, fluorine 0.0007%, iron ≤ 0.002%, arsenic ≤ 0.0002%, heavy metal 0.0009%, chloride ≤ 0.0005 %.

Example 3:

Step is with embodiment 1, and difference is:

Extraction and refining process: the compound extractant and the above-mentioned extraction acid are used for countercurrent contact extraction at a ratio of 1:4, the loaded organic phase and washing water are compared at a ratio of 16:1 for countercurrent contact washing, and the washing organic phase is compared with distilled water at a ratio of 15: 1. Perform countercurrent contact stripping; the composition and weight ratio of the composite extractant are: ketone ether: alcohol: ester = 80: 15: 5, the composition and weight ratio of the ketone ether are: ketone: ether =75:25;

Example 3 extraction results: extraction rate 90%; product quality: H ₃ PO ₄ content 85.5%, sulfate ≤ 0.002%, fluorine 0.0007%, iron ≤ 0.002%, arsenic ≤ 0.0002%, heavy metal 0.0009%, chloride ≤ 0.0005 %.

The above descriptions are only preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments, but all equivalent modifications or changes made by those of ordinary skill in the art according to the disclosure of the present invention should be included within the scope of protection described in the claims. the

Claims (4)

1. the method for a composite extractant extracting and refining phosphoric acid by wet process, this method comprises pretreatment technology, extracting and refining technology and aftertreatment technology successively, it is characterized in that said method comprises following technology successively:

Pretreatment technology: the raw phosphoric acid that earlier wet method is made concentrates P in raw phosphoric acid ₂O ₅Mass percent concentration be 45%, add Na in the raw phosphoric acid after concentrating again ₂CO ₃Carry out defluorinate, said Na ₂CO ₃Add-on stoichiometric 100% – 120% of free state fluorion calculates in the raw phosphoric acid of back by concentrating; Add compound sinking agent then in the raw phosphoric acid after defluorinate and carry out sedimentation, restir is even, and sedimentation can obtain clear acid of sedimentation and underflow slag acid after 4 hours; The volume of the clear acid of said sedimentation is 85% – 90% of raw phosphoric acid after the defluorinate, compound sinking agent volume sum; Composting between tumbril is sent in said underflow slag acid, in the clear acid of sedimentation, adds the powdered activated carbon then and decolours, and the mass volume ratio mg/ml of the clear acid of this activated carbon and sedimentation is 0.5% – 1.5%:1; Filter again to obtain extracting ortho acid, solid contents ﹤ 0.05wt% in the said extraction ortho acid;

Extracting and refining technology: earlier composite extractant is carried out the counter current contact extraction to obtain load organic phases and raffinate with above-mentioned extraction ortho acid by comparing 1:2 – 4; Again the load organic phases that obtains is carried out the counter current contact washing to obtain washing organic phase and wash water with wash water by comparing 10 – 25:1; To wash organic phase then and carry out the counter current contact reextraction to obtain strip liquor and unloaded organic phase by comparing 6 – 25:1, again the strip liquor that obtains reclaimed extraction agent to obtain reclaiming the back strip liquor with zero(ppm) water; The said volume ratio that is in a ratio of organic phase and water;

The composition of said composite extractant and weight part ratio thereof are: ether ketone: alcohol: ester=60 – 80:15 – 20:5 – 15, and the composition of said ether ketone and weight part ratio thereof are: ketone: ether=95 – 60:5 – 40; Said ketone nail base nezukone, diisopropyl ketone, DIBK, MIBK or pimelinketone; Said ether refers to DIPE or diisobutyl ether; Said alcohol make a comment or criticism butanols, isopropylcarbinol, Pentyl alcohol, primary isoamyl alcohol or hexalin, said ester refers to three butoxyethyl group SULPHOSUCCINIC ACID ESTER or tributyl phosphates;

Aftertreatment technology: earlier strip liquor after the above-mentioned recovery that obtains is concentrated H in reclaiming the back strip liquor ₃PO ₄Mass percent concentration be 75%; Obtain 75% phosphoric acid this moment, in 75% phosphoric acid, add the powdered activated carbon again and decolour, filter then to obtain decolouring back 75% phosphoric acid; Drop into the barium salt desulfurization by sulfate radical stoichiometric 100% in 75% phosphoric acid of decolouring back again; Treat to refilter after the requirement that sulfate radical content is up to state standards, then filtrating is concentrated H in filtrating ₃PO ₄Mass percent concentration be 85%, promptly get industrial 85% phosphoric acid of product this moment.

2. the method for a kind of composite extractant extracting and refining phosphoric acid by wet process according to claim 1; It is characterized in that: in the said pretreatment technology: the volume of compound sinking agent is 1 ‰ – 10 ‰ of raw phosphoric acid volume after the defluorinate; Said compound sinking agent is that mass percent concentration is the aqueous solution of 5% – 15%, and its solute is for pressing the nonionogenic tenside and the AS of the preparation of 1:10 – 50 mass ratioes;

Said nonionogenic tenside is: maleic acid-acrylic acid copolymer, acrylamide-acrylicacid methyl esters-2-acrylamido-2-methyl propane sulfonic acid multipolymer, AM-AA-DMA multipolymer a kind of or press any two kinds of 1:1 mass ratio preparation;

Said AS is a kind of of oil base T 46155 (10) ether phosphate, sodium octyl sulfate, α – sodium olefin sulfonate, sodium lignosulfonate, stearyl sulfosuccinamic acid disodium, Texapon Special.

3. the method for a kind of composite extractant extracting and refining phosphoric acid by wet process according to claim 1 and 2 is characterized in that: in the said extracting and refining technology: said raffinate send composting Workshop Production fertilizer; Said wash water is the phosphoric acid solution that contains sodium, potassium or ammonium salt, and said wash water send phosphoric acid salt Workshop Production sodium phosphate salt, sylvite or ammonium salt after reclaiming extraction agent; Said unloaded organic phase is with after the extraction agent of recovery mixes, in order to the preparation composite extractant to recycle.

4. the method for a kind of composite extractant extracting and refining phosphoric acid by wet process according to claim 1 and 2 is characterized in that: in the said aftertreatment technology: said industrial 85% phosphoric acid can obtain food grade phosphoric acid behind silicon-dioxide defluorinate, sulfide dearsenification removing heavy-metal.

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