Method for separating phosphorus and sulfur in high-sulfur phosphoric acid

Abstract

The invention relates to a method for separating phosphorus and sulfur in high-sulfur phosphoric acid, which comprises the following steps: mixing high-sulfur phosphoric acid with the content of SO4 < 2-> being 40-70wt% and the content of P2O5 being 10-30wt% with an extraction agent for phase separation to obtain an extraction phase 1 and a raffinate phase 1, mixing the extraction phase 1 with washing acid for phase separation to obtain an extraction phase 2 and a raffinate phase 2, and separating the extraction phase 2 from the raffinate phase 2, mixing the extraction phase 2 and the washing acid for phase splitting to obtain an extraction phase 3 and a raffinate phase 3, and finally mixing the extraction phase 3 and desalted water for phase splitting to obtain reverse extraction acid, namely the low-sulfur phosphoric acid. According to the method, a chemical precipitator is not used, the extraction agent is directly used, most of phosphoric acid enters the extraction agent to be separated by optimizing a phase ratio, and meanwhile, the property that dilute phosphoric acid can destroy phase equilibrium is utilized, so that the content of sulfate radicals in the finally obtained reverse extraction acid is within 4wt%.

Description

Technical Field

[0001] The invention relates to the technical field of phosphorus chemical industry, and in particular to a method for separating phosphorus and sulfur in high-sulfur phosphoric acid. Background Art

[0002] Phosphoric acid is an inorganic acid with three ionizable hydrogen ions. It is a medium-strong acid and is widely used in agriculture, industry, food, medicine, building materials and other fields. The preparation methods of phosphoric acid mainly include thermal phosphoric acid and wet phosphoric acid. Thermal phosphoric acid usually uses high-grade phosphate rock as raw material. It uses an electric furnace method to reduce phosphate rock powder with carbon at high temperature to produce yellow phosphorus, and then oxidizes and hydrates it to make phosphoric acid. Wet phosphoric acid uses medium- and low-grade phosphate rock as raw material and decomposes phosphate rock with strong acid to prepare phosphoric acid. Compared with thermal phosphoric acid, wet phosphoric acid has the advantages of a wide range of raw material sources, low energy consumption and low pollution, so it is favored by the market. Wet phosphoric acid mainly includes sulfuric acid method, nitric acid method and hydrochloric acid method. Due to the wide source of sulfuric acid and low cost, more than 80% of domestic wet phosphoric acid is produced by sulfuric acid decomposing phosphate rock as a by-product of calcium sulfate dihydrate. In this process, in order to ensure the formation of neat and coarse calcium sulfate crystals, excess sulfuric acid needs to be added when decomposing the phosphate ore. As the domestic raw phosphate ore is continuously mined, the grade continues to decrease and the concentration of sulfuric acid required for the reaction increases accordingly. Therefore, these sulfuric acids will become impurities remaining in the phosphoric acid and are difficult to remove.

[0003] In the production process of wet phosphoric acid, high concentration of sulfuric acid will not only release more dilution heat, causing the local temperature of the reaction tank to be too high, aggravating equipment corrosion, affecting the crystallization of phosphogypsum and its filtration and washing performance, leading to increased raw material consumption and production costs, but also affecting the quality of downstream terminal products of phosphorus chemical industry. Therefore, removing sulfuric acid from wet phosphoric acid is a necessary process step before producing phosphoric acid purification products and industrial-grade phosphates.

[0004] Phosphorus and sulfur are elements of the same family. To remove sulfuric acid from phosphoric acid, domestic companies mainly use chemical precipitation methods. Phosphorus rock powder, calcium salts, barium salts, etc. form insoluble precipitation with sulfuric acid in phosphoric acid, and then separate sulfuric acid from phosphoric acid through filtration or precipitation. For example, the patent with application number CN201410818845.1 discloses a method for desulfurization of dilute phosphoric acid, in which calcium-containing defluorination slag is added to the dilute phosphoric acid for desulfurization; the patent with application number CN201110185944.7 discloses a precipitant for refining and desulfurization of wet-process phosphoric acid and its use method, in which barium salt is added to the wet-process phosphoric acid, and then a precipitant made of a non-ionic flocculant and an anionic surfactant is added for desulfurization; the patent with application number CN202011198890.3 discloses a method for removing sulfate from wet-process dilute phosphoric acid by using phosphate slurry, in which phosphate slurry with a water content of 33% to 35% is added to the dilute phosphoric acid to reduce the sulfate content in the dilute phosphoric acid; the patent with application number CN201310551807.X discloses a method for producing industrial phosphates by using wet-process phosphoric acid, in which sulfuric acid is removed from the wet-process phosphoric acid by a three-step neutralization reaction of a quantitative amount of phosphate rock powder, calcium hydroxide, sodium carbonate or potassium hydroxide. However, these patents have the following defects: in order to achieve a better desulfurization effect, an excessive amount of precipitant is usually added during the production process, which not only prolongs the desulfurization time, but also causes the precipitant and soluble impurities in the precipitant to enter the liquid phase of wet-process phosphoric acid, thereby increasing the impurity content in the wet-process phosphoric acid; at the same time, the methods in the above patents are not very effective for SO4 2- Phosphoric acid with a mass percentage of less than 40% is feasible, but when the phosphoric acid solution contains SO4 2- When the mass percentage is greater than 40%, the use of a precipitant will cause a large amount of impurities to enter the wet-process phosphoric acid liquid phase, so that the prepared phosphoric acid is difficult to be industrially applied. Summary of the invention

[0005] The present invention aims to solve the problems of the current separation of phosphorus and sulfur from high-sulfur phosphoric acid, such as the introduction of impurities, difficulty in solid-liquid separation, and poor quality, and provides a method for separating phosphorus and sulfur from high-sulfur phosphoric acid.

[0006] In order to solve the above technical problems, the technical solution of the present invention is:

[0007] S1: After mass transfer, high sulfur phosphoric acid and an extractant are mixed and separated into phases to obtain an extract phase 1 and a raffinate phase 1;

[0008] S2: After mixing the extract phase 1 obtained in step S1 and the dilute phosphoric acid, the mixture is separated into phases to obtain an extract phase 2 and a raffinate phase 2;

[0009] S3: After mixing the extract phase 2 obtained in step S2 and the dilute phosphoric acid, the mixture is separated into phases to obtain an extract phase 3 and a raffinate phase 3;

[0010] S4: The extract phase 3 obtained in step S3 is stripped with desalted water to obtain stripping acid, which is low-sulfur phosphoric acid.

[0011] Preferably, in step S1, SO4 2- The mass percentage is 40% to 70%, and the mass percentage of P2O5 is 10% to 30%.

[0012] Preferably, in step S1, the extractant is methyl isobutyl ketone or tributyl phosphate.

[0013] Preferably, in step S1, the volume ratio of the persulfate phosphoric acid to the extractant is 1:1-10, and the extraction temperature is 40-50°C.

[0014] More preferably, in the step S1, the volume ratio of the persulfate phosphoric acid to the extractant is 1:5-6.

[0015] Preferably, the SO4 in the dilute phosphoric acid 2- The mass percentage is ≤0.5%, and the mass percentage of P2O5 is 27% to 65%.

[0016] Preferably, in step S2, the volume ratio of the extraction phase 1 to the dilute phosphoric acid is 20-50:1.

[0017] Preferably, in step S3, the volume ratio of the extraction phase 2 to the dilute phosphoric acid is 20-50:1.

[0018] Preferably, in step S4, the volume ratio of the extraction phase 3 to the desalted water is 8-15:1.

[0019] Compared with the prior art, the present invention has the following advantages: 2- In the high sulfur phosphoric acid with a mass percentage of 40% to 70% and a P2O5 mass percentage of 10% to 30%, no chemical precipitant is used, and an extractant is used directly. The performance of the extractant to preferentially extract phosphoric acid and exclude cations is utilized, and most of the phosphoric acid enters the extractant for separation by optimizing the phase ratio. At the same time, the property of dilute phosphoric acid that can destroy phase equilibrium is utilized to avoid phosphorus loss, and the sulfur content of the finally obtained stripping acid is within 4wt%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a flow chart of a method for separating phosphorus and sulfur in high-sulfur phosphoric acid. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] This embodiment provides a method for separating phosphorus and sulfur in high-sulfur phosphoric acid, wherein the impurity elements and main elements are tested: impurity element SO4 2- The test was carried out using inductively coupled plasma optical emission spectrometry; the main element P2O5 was tested using the national standard method gravimetric method.

[0023] The present invention provides a method for separating phosphorus and sulfur from high-sulfur phosphoric acid. Figure 1 , including the following steps:

[0024] S1: Extractant and SO4 2- High sulfur phosphoric acid with a mass percentage of 40-70% and a mass percentage of P2O5 of 10-30% is used at a volume ratio of 1-10:1 and an extraction temperature of 45±5°C to enhance the intermolecular force between phosphoric acid and the extractant in the mixed system and the solubility of the extractant. After extraction, most of the phosphoric acid remains in the extraction phase 1 and most of the sulfuric acid remains in the residual phase 1 through phase separation, thereby achieving the separation of phosphorus and sulfur in the mixed system.

[0025] S2: The extract phase 1 obtained in step S1 and SO4 2- After the dilute phosphoric acid with a mass percentage of ≤0.5% and a P2O5 mass percentage of 27% to 65% is mixed at a volume ratio of 20 to 50:1, the addition of the dilute phosphoric acid causes the sulfuric acid and phosphoric acid in the extraction phase 1 to form a concentration difference. After phase separation, most of the phosphoric acid is enriched in the extraction phase 2, while more sulfuric acid in the extraction phase 1 enters the raffinate phase 2 to further remove the sulfuric acid.

[0026] S3: extract phase 2 obtained in step S2 and SO4 2- After the dilute phosphoric acid with a mass percentage of ≤0.5% and a P2O5 mass percentage of 27% to 65% is mixed at a volume ratio of 20 to 50:1, the dilute phosphoric acid is used to supplement the phosphoric acid lost in the above steps into the extraction phase 2, so that the concentration difference of the extraction phase is formed again, so that the sulfuric acid in the extraction phase 2 enters the raffinate phase 3, and most of the phosphoric acid remains in the extraction phase 3, thereby further reducing the sulfuric acid in the extraction phase.

[0027] S4: After stripping the extract phase 3 obtained in the above step S3 and desalted water at a volume ratio of 8 to 15:1, the phosphoric acid in the extract phase 3 is washed into the water phase, and the phases are separated to obtain stripping acid. SO4 in the stripping acid 2-The mass percentage is ≤4%, the mass percentage of P2O5 is ≥50%, and no new impurities are introduced.

[0028] Example 1

[0029] S1: SO4 2- Persulfuric acid with a mass percentage of 60% and a P2O5 mass percentage of 30% and methyl isobutyl ketone were mixed and mass transferred at a volume ratio of 1:4 and an extraction temperature of 40°C, and then phase separation was performed to obtain an extract phase 1 and a raffinate phase 1. Among them, the P2O5 mass percentage in the raffinate phase 1 was 5%, SO4 2- The mass percentage is 13%; the mass percentage of extraction phase 1 is P2O5, which is 15%, SO4 2- The mass percentage is 4%.

[0030] S2: The extract phase 1 obtained in step S1 above is mixed with P2O5 (mass percentage is 27%), SO4 2- After mixed mass transfer with 0.5% diluted phosphoric acid at a volume ratio of 50:1, phase separation was performed to obtain extract phase 2 and raffinate phase 2. Among them, the mass percentage of P2O5 in raffinate phase 2 is 3.3%, SO4 2- The mass percentage is 7.2%; the mass percentage of extraction phase 2 is P2O5, which is 15%, SO4 2- The mass percentage is 2%.

[0031] S3: The extract phase 2 obtained in step S2 above is mixed with P2O5 (mass percentage: 27%), SO4 2- After mixed mass transfer with 0.5% diluted phosphoric acid at a volume ratio of 50:1, phase separation was performed to obtain extract phase 3 and raffinate phase 3. Among them, the mass percentage of P2O5 in raffinate phase 3 is 3%, and SO4 2- The mass percentage is 4%; the mass percentage of extraction phase 3 is P2O5, which is 15%, SO4 2- The mass percentage is 1%; the raffinate phase 1, the raffinate phase 2 and the raffinate phase 3 are used as raw materials for low-nutrient phosphate fertilizer after analysis.

[0032] S4: Mix the extract phase 3 obtained in step S3 with the desalted water in a volume ratio of 10:1 for mass transfer, and then separate the phases to obtain stripping acid. The main components of stripping acid are as follows: P2O5 is 55%, SO4 2- is 3%.

[0033] Example 2

[0034] S1: SO4 2-Persulfuric acid with a mass percentage of 70% and a P2O5 mass percentage of 10% and methyl isobutyl ketone were mixed and mass transferred at a volume ratio of 1:5 and an extraction temperature of 45°C, and then phase separation was performed to obtain an extract phase 1 and a raffinate phase 1. Among them, the P2O5 mass percentage in the raffinate phase 1 was 7%, SO4 2- Mass percentage 15%; extraction phase 1 is P2O5 mass percentage 12%, SO4 2- The mass percentage is 6%.

[0035] S2: The extract phase 1 obtained in step S1 above is mixed with P2O5 (mass percentage is 65%), SO4 2- After mixed mass transfer with 0.3% diluted phosphoric acid at a volume ratio of 20:1, phase separation was performed to obtain extract phase 2 and raffinate phase 2. Among them, the mass percentage of P2O5 in raffinate phase 2 is 2%, and SO4 2- The mass percentage is 8%; the mass percentage of extraction phase 2 is P2O5, which is 15%, SO4 2- The mass percentage is 3%.

[0036] S3: The extract phase 2 obtained in step S2 above is mixed with P2O5 (mass percentage is 65%), SO4 2- After mixed mass transfer with 0.3% diluted phosphoric acid at a volume ratio of 20:1, phase separation was performed to obtain extract phase 3 and raffinate phase 3. Among them, the mass percentage of P2O5 in raffinate phase 3 was 1%, and SO4 2- The mass percentage is 3.5%; the mass percentage of extraction phase 3 is 12% for P2O5, SO4 2- The mass percentage is 1.5%; the raffinate phase 1, the raffinate phase 2 and the raffinate phase 3 are used as raw materials for low-nutrient phosphate fertilizer after analysis.

[0037] S4: The extract phase 3 obtained in the above step S3 is fully mixed with the desalted water at a volume ratio of 8:1 for mass transfer, and then phase separated to obtain stripping acid. The mass percentage of the main components of the stripping acid is: P2O5 is 52%, SO4 2- is 3%.

[0038] Example 3

[0039] S1: SO4 2- High sulfur phosphoric acid with a mass percentage of 68% and a P2O5 mass percentage of 25% and tributyl phosphate were mixed and mass transferred at a volume ratio of 1:6 and an extraction temperature of 48°C, and then phase separation was performed to obtain an extract phase 1 and a raffinate phase 1. Among them, the P2O5 mass percentage in the raffinate phase 1 was 5.4%, SO4 2- Mass percentage 12%; extraction phase 1 is P2O5 mass percentage 14%, SO4 2- The mass percentage is 4.2%.

[0040] S2: The extract phase 1 obtained in step S1 above is mixed with 32% P2O5 and 32% SO4 2- After mixed mass transfer of 0.3% dilute phosphoric acid at a volume ratio of 40:1, phase separation was performed to obtain extract phase 2 and raffinate phase 2. Among them, the mass percentage of P2O5 in raffinate phase 2 is 3%, and SO4 2- The mass percentage is 6.1%; the mass percentage of extraction phase 2 is P2O5, which is 14%, SO4 2- The mass percentage is 2.2%.

[0041] S3: The extract phase 2 obtained in step S2 above is mixed with P2O5 (mass percentage is 32%), SO4 2- After mixed mass transfer with 0.3% diluted phosphoric acid at a volume ratio of 40:1, phase separation was performed to obtain extract phase 3 and raffinate phase 3. Among them, the mass percentage of P2O5 in raffinate phase 3 is 2.3%, SO4 2- The mass percentage is 4%; the mass percentage of extraction phase 3 is P2O5, which is 14%, SO4 2- The mass percentage is 2.2%; the raffinate phase 1, the raffinate phase 2 and the raffinate phase 3 are used as raw materials for low-nutrient phosphate fertilizer after analysis.

[0042] S4: The extract phase 3 obtained in the above step S3 is fully mixed with desalted water at a volume ratio of 15:1 for mass transfer, and then separated into phases to obtain stripping acid. The mass percentage of the main components of the stripping acid is: P2O5 is 53%, SO4 2- is 3%.

[0043] Example 4

[0044] S1: SO4 2- Persulfuric acid with a mass percentage of 40% and a P2O5 mass percentage of 28% and methyl isobutyl ketone were mixed and mass transferred at a volume ratio of 1:1 and an extraction temperature of 50°C, and then phase separation was performed to obtain an extract phase 1 and a raffinate phase 1. Among them, the P2O5 mass percentage in the raffinate phase 1 was 6.1%, SO4 2- The mass percentage is 14.1%; the mass percentage of extraction phase 1 is P2O5, which is 14.3%, SO4 2- The mass percentage is 3%.

[0045] S2: The extract phase 1 obtained in step S1 above is mixed with P2O5 (mass percentage is 60%), SO4 2- After mixed mass transfer with 0.2% diluted phosphoric acid at a volume ratio of 45:1, phase separation was performed to obtain extract phase 2 and raffinate phase 2. Among them, P2O5 in raffinate phase 2 contains 4%, SO4 2- The mass percentage is 7%; the mass percentage of extraction phase 2 is P2O5, which is 14.3%, SO42- The mass percentage is 1.5%.

[0046] S3: The extract phase B obtained in step S2 above is mixed with P2O5 (mass percentage is 60%), SO4 2- After mixed mass transfer of 0.2% diluted phosphoric acid at a volume ratio of 45:1, phase separation was performed to obtain extract phase 3 and raffinate phase 3. Among them, the mass percentage of P2O5 in raffinate phase 3 is 1.5%, SO4 2- The mass percentage is 3%; the mass percentage of extraction phase 3 is P2O5, which is 14.3%, SO4 2- The mass percentage is 0.8%; the raffinate phase 1, the raffinate phase 2 and the raffinate phase 3 are used as raw materials for low-nutrient phosphate fertilizer after analysis.

[0047] S4: The extract phase 3 obtained in the above step S3 is fully mixed with desalted water at a volume ratio of 11:1 for mass transfer, and then phase-separated to obtain stripping acid. The mass percentage of the main components of the stripping acid is: P2O5 is 52.4%, SO4 2- is 2%.

[0048] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for separating phosphorus and sulfur from high-sulfur phosphoric acid, characterized in that: include: S1: After mass transfer, high sulfur phosphoric acid and an extractant are mixed and separated into phases to obtain an extract phase 1 and a raffinate phase 1; S2: After mixing the extract phase 1 obtained in step S1 and the dilute phosphoric acid, the mixture is separated into phases to obtain an extract phase 2 and a raffinate phase 2; S3: After mixing the extract phase 2 obtained in step S2 and the dilute phosphoric acid, the mixture is separated into phases to obtain an extract phase 3 and a raffinate phase 3; S4: The extract phase 3 obtained in step S3 is stripped with desalted water to obtain low-sulfur phosphoric acid.

2. The method for separating phosphorus and sulfur in high-sulfur phosphoric acid according to claim 1, characterized in that: In step S1, the high sulfur phosphoric acid includes SO4 2- The mass percentage is 40% to 70%, and the mass percentage of P2O5 is 10% to 30%.

3. The method for separating phosphorus and sulfur in high-sulfur phosphoric acid according to claim 1, characterized in that: In the step S1, the extractant is methyl isobutyl ketone or tributyl phosphate.

4. The method for separating phosphorus and sulfur in high-sulfur phosphoric acid according to claim 1, characterized in that: In the step S1, the volume ratio of the high sulfur phosphoric acid to the extractant is 1:1-10, and the extraction temperature is 40-50°C.

5. The method for separating phosphorus and sulfur in high-sulfur phosphoric acid according to claim 1, characterized in that: In the steps S2 and S3, the SO4 in the dilute phosphoric acid 2- The mass percentage is ≤0.5%, and the mass percentage of P2O5 is 27% to 65%.

6. The method for separating phosphorus and sulfur in high-sulfur phosphoric acid according to claim 1, characterized in that: In the step S2, the volume ratio of the extraction phase 1 to the dilute phosphoric acid is 20-50:

1.

7. The method for separating phosphorus and sulfur in high-sulfur phosphoric acid according to claim 1, characterized in that: In the step S3, the volume ratio of the extraction phase 2 to the dilute phosphoric acid is 20-50:

1.

8. The method for separating phosphorus and sulfur in high-sulfur phosphoric acid according to claim 1, characterized in that: In the step S4, the volume ratio of the extraction phase 3 to the desalted water is 8-15:1.

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