Method for purifying phosphogypsum in wet-process phosphoric acid production process

Abstract

The invention relates to a method for purifying phosphogypsum in a wet-process phosphoric acid production process, which comprises the following steps: mixing phosphate concentrate with a phosphorus-sulfur mixed acid solution, dissolving to obtain reaction slurry, adding a composite purifying agent into the reaction slurry, and carrying out foam separation to obtain a foam product and impurity-removed and purified slurry, sequentially filtering and washing the purified slurry to obtain phosphoric acid and phosphogypsum; and carrying out solid-liquid separation on the foam product to obtain medicament acid liquor and residues. The method for purifying and whitening ardealite in the wet-process phosphoric acid production process is invented by starting from the ardealite production source and summarizing the characteristics of the traditional wet-process phosphoric acid technology for producing ardealite, the quality of ardealite is improved from the source, impurities in phosphoric acid are purified, TOC of phosphoric acid is reduced, meanwhile, the cost is low, the process adaptability is high, and the method is suitable for industrial production. The improvement of the utilization rate of phosphorus resources is promoted.

Description

Technical Field

[0001] The invention belongs to the field of purification and impurity removal of phosphogypsum, and specifically relates to a method for purifying and whitening phosphogypsum in a wet phosphoric acid production process. Background Art

[0002] Phosphogypsum is a byproduct of phosphoric acid produced by the wet phosphoric acid process. Its main chemical components are CaSO4·2H2O and CaSO4·1 / 2H2O. According to statistics, the production of 1 ton of phosphoric acid will produce 5 to 6 tons of phosphogypsum (dry basis), and the actual volume is about 7 tons. As of 2023, the cumulative stockpile of phosphogypsum in my country will exceed 800 million tons, and the comprehensive utilization rate will be 55.6%. Phosphogypsum is highly acidic, with large fluctuations in grade. It also contains various forms of impurities such as phosphorus, fluorine substances, quartz, organic matter, and metal salts. These impurities will not only pollute the environment, but also have a great impact on the comprehensive utilization of phosphogypsum. Therefore, purification and whitening of phosphogypsum can turn waste into treasure and greatly improve its utilization value. At present, the research on the whitening and purification technology of phosphogypsum is mainly based on the treatment of the terminal of wet phosphoric acid - phosphogypsum, which is not only difficult to treat but also has poor effect. Flotation is a common method for pretreatment and impurity removal of phosphogypsum. It is usually to stir the phosphogypsum in a strong acidic environment and then send it to the flotation equipment, and then add the flotation agent for foam separation. This method can remove most of the organic matter and insoluble impurities in the phosphogypsum, but the purity and whiteness of the concentrate gypsum after flotation are low, which affects the downstream products. CN117696265A provides a phosphogypsum decolorization and purification process through grinding, microbubble pretreatment, one rough flotation and two fine flotations. The pH of the pretreated pulp is adjusted to 6.5-7.5, and flotation separation is performed after adding the collector and the frother. The process flow is long and the energy consumption is high. The microbubble pretreatment is difficult to promote, and there are many points for adding the agent, which makes the actual operation difficult. CN117324123A provides a method for washing and desludging phosphogypsum, and then purifying and decolorizing it through reverse-forward flotation. This method has many kinds of reagents, a complicated process flow, and must distinguish and treat the return water of the reverse flotation and forward flotation systems, which is costly and difficult. CN117920466A discloses a reagent method for removing impurities from phosphogypsum through synchronous reverse flotation. The frother provided by the method is mainly used to remove organic impurities, and the collector is mainly used to remove silicate impurities. Starting from phosphogypsum, this method improves the disadvantage of poor quality of phosphogypsum to a certain extent, but there are problems such as high processing cost, great difficulty, and difficulty in ensuring the effect.

[0003] Starting from the wet-process phosphoric acid, the source of phosphogypsum production, there are few methods for improving the quality of phosphogypsum. CN114835094A provides a method for extracting phosphoric acid and phosphogypsum in situ with an extractant during phosphoric acid acid hydrolysis. The method realizes in-situ extraction and separation of phosphoric acid while leaching phosphoric acid, reducing impurities in phosphoric acid and by-product calcium sulfate, but there are problems such as high cost of the extractant, difficulty in recovery, and high pollution. CN117509576A provides a method for preparing phosphoric acid by crushing and calcining phosphate ore or phosphate tailings and then leaching with ammonium nitrate. The dihydrate calcium sulfate produced by this process has a purity of more than 96% and a whiteness of more than 86%, but the calcination energy consumption is high, the cost is high, the process flow is complicated, and it is difficult to promote and apply.

[0004] In summary, in order to improve the problems of poor quality of impurity-removed gypsum, complex process flow and difficult to ensure the effect brought by the traditional flotation method, and solve the problems of high cost, high energy consumption and high pollution in the source of phosphogypsum production, it is necessary to develop a method for purifying and removing soluble and insoluble impurities from the wet phosphoric acid production process, which can not only improve the quality of by-product calcium sulfate, but also reduce the TOC of phosphoric acid and realize phosphoric acid purification, with the advantages of low cost, low energy consumption and environmental protection. Summary of the invention

[0005] The present invention starts from the source of phosphogypsum production, summarizes the characteristics of poor quality of phosphogypsum as a by-product of the wet-process phosphoric acid process obtained in the prior art, and provides a method for purifying and whitening phosphogypsum in the wet-process phosphoric acid production process, which not only improves the quality of phosphogypsum from the source, but also purifies impurities in phosphoric acid and reduces the TOC of phosphoric acid. It has the characteristics of low reagent cost and strong process adaptability, and has a certain promoting effect on achieving an increase in the utilization rate of phosphorus resources.

[0006] To achieve the above object, the technical solution of the present invention is as follows: (1) mixing phosphate concentrate with phosphorus-sulfur mixed acid solution and dissolving them to obtain reaction slurry; (2) After the composite purifier is uniformly mixed with the reaction slurry described in step (1), flotation separation is performed to obtain a foam product and a purified and impurity-free slurry; (3) filtering and washing the purified slurry in step (2) to obtain wet-process phosphoric acid and phosphogypsum; (4) After solid-liquid separation of the foam product in step (2), a liquid phase reagent and a solid phase residue are obtained. The reagent can be recycled as a composite purifier for purifying and removing impurities in the reaction slurry, and the residue can be treated as tailings.

[0007] (5) As a preferred technical solution of the present invention, the P2O5 grade in the phosphate concentrate described in step (1) is 25%~36%.

[0008] (6) Preferably, the mass ratio of the phosphate concentrate to the phosphorus-sulfur mixed acid solution in step (1) is 1:(1.5-2.6).

[0009] (7) Preferably, in the phosphorus-sulfur mixed acid solution of step (1), sulfuric acid, phosphoric acid and water are uniformly mixed in a mass ratio of 1: (0.5-1): 1, wherein the mass concentration of sulfuric acid is greater than 98%, and the mass concentration of phosphoric acid is greater than 85%.

[0010] Preferably, the dissolving temperature in step (1) is 70-90°C.

[0011] Preferably, the dissolution time in step (1) is (30-240 min).

[0012] Preferably, the composite purifier in step (2) is compounded from a foaming agent and an amine agent, has both foaming and collecting properties, and is used in an amount of 0.4-1 kg / t.

[0013] Preferably, the composite purifier in step (2) comprises a foaming agent and an amine agent, wherein the foaming agent comprises one or more of pine oil, eucalyptus oil, methyl isobutyl carbinol, dimethyl benzyl alcohol, polyvinyl alcohol and alkane aromatic hydrocarbons.

[0014] Preferably, the composite purifier in step (2) comprises a foaming agent and an amine agent, wherein the amine agent comprises one or more of laurylamine acetate, laurylamine hydrochloride, triethyltetramine, dihexadecyldimethylammonium acetate, alkylbenzylpyridine, trimethylhexadecylammonium bromide, amylphenyl ether amine, denatured rosin amine, alkanolamide, and dodecyl-N-carboxyethyl imidazoline.

[0015] Preferably, the liquid phase reagent obtained in step (4) is recycled and reused in step (2).

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) In the process of wet phosphoric acid production, a small amount of composite purifier is used to separate organic matter and insoluble impurities in the wet phosphoric acid in time through flotation equipment, which not only reduces impurities in the by-product phosphogypsum and improves its whiteness and purity, but also purifies impurities in phosphoric acid, reduces the TOC of acid solution, and improves the utilization rate of phosphorus resources; (2) The raw materials of the composite purifier used in the present invention are cheap, easy to obtain and easy to recycle and reuse, without introducing new impurities. The impurity removal process is carried out at normal temperature and pressure, with low cost, strong adaptability of the process flow, and good economic benefits and promotion and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart of the method for purifying phosphogypsum in the wet phosphoric acid production process. DETAILED DESCRIPTION

[0018] Example 1 This embodiment provides a method for purifying phosphogypsum in a wet phosphoric acid production process, and the method comprises the following steps.

[0019] (1) Phosphate concentrate and phosphorus-sulfur mixed acid solution were mixed in a mass ratio of 1:1.5, and dissolved at 80°C for 1 hour to obtain a reaction slurry. The P2O5 component in the phosphate concentrate was 31.5%, and sulfuric acid, phosphoric acid and water were prepared in a mass ratio of 1:0.77:1.

[0020] (2) Add 0.4 kg / t of composite purifier to the reaction slurry, stir for 3 minutes to obtain a mixed slurry, and perform flotation separation on the mixed slurry to obtain a foam product and an in-tank product. The composite purifier is a compound obtained by mixing a foaming agent and an amine agent, wherein the foaming agent comprises pine oil and polyvinyl alcohol in a mass ratio of 3:2; the amine agent comprises lauric hydrochloride, dihexadecyl dimethyl ammonium acetate, and amylphenyl ether amine in a mass ratio of 3:2:1.

[0021] (3) The foam product is subjected to solid-liquid separation to obtain solid organic matter and silicate impurities, and the liquid agent acid is recycled into the reaction slurry of step (2). The liquid agent can be recycled into the reaction slurry and used as a low-concentration composite purifier, thereby reducing the amount of composite purifier used and reducing costs.

[0022] (4) The product in the tank is separated into solid and liquid to obtain solid phosphogypsum and liquid phosphoric acid.

[0023] (5) After three countercurrent washings of the solid phosphogypsum, it is transported to the phosphogypsum storage yard by belt conveyor, and the liquid phosphoric acid is pumped into the dilute phosphoric acid aging tank for aging.

[0024] The measured TOC of phosphoric acid in Example 1 was 140 ppm, the whiteness of phosphogypsum was 61.2%, the purity was 93.7%, the total phosphorus was 1.12%, and the total fluorine was 0.5%.

[0025] Comparative Example 1 The method and steps are the same as those in Example 1. The foaming agent pine oil in the composite purifier formula is removed, and the slurry purification flotation is performed. It is detected that the TOC in Comparative Example 1 is 1530 ppm, the whiteness in the phosphogypsum is 38.5%, the purity is 90.4%, the total phosphorus is 1.73%, and the total fluorine is 0.67%.

[0026] Comparative Example 2 The method and steps are the same as those in Example 1. The amine agent lauryl hydrochloride in the composite purifier formula is removed, and the slurry purification flotation is performed. It is detected that the TOC in Comparative Example 1 is 720 ppm, the whiteness in the phosphogypsum is 54.5%, the purity is 90.2%, the total phosphorus is 1.84%, and the total fluorine is 0.68%.

[0027] Example 2 (1) Phosphate concentrate and phosphorus-sulfur mixed acid solution were mixed in a mass ratio of 1:1.7, and dissolved at 85°C for 1.1 h to obtain a reaction slurry. The P2O5 component in the phosphate concentrate was 28.8%, and sulfuric acid, phosphoric acid and water were prepared in a mass ratio of 1:0.8:1.

[0028] (2) Add 0.75 kg / t of composite purifier to the reaction slurry, stir for 3 minutes to obtain a mixed slurry, and perform flotation separation on the mixed slurry to obtain a foam product and an in-tank product. The composite purifier is a compound of a foaming agent and an amine agent, wherein the foaming agent contains methyl isobutyl carbinol and eucalyptus oil in a mass ratio of 2:3; the amine agent contains alkyl benzyl pyridine, denatured rosin amine, and alkanolamide in a mass ratio of 1:4:3.

[0029] (3) The foam product is subjected to solid-liquid separation to obtain solid organic matter and silicate impurities, and the liquid agent acid is recycled into the reaction slurry of step (2), thereby reducing the amount of composite purifier used and reducing costs.

[0030] (4) The product in the tank is separated into solid and liquid to obtain solid phosphogypsum and liquid phosphoric acid.

[0031] (5) After three countercurrent washings of the solid phosphogypsum, it is transported to the phosphogypsum storage yard by belt conveyor, and the liquid phosphoric acid is pumped into the dilute phosphoric acid aging tank for aging.

[0032] The measured TOC of phosphoric acid in Example 2 was 135 ppm, the whiteness of phosphogypsum was 60.2%, the purity was 93.3%, the total phosphorus was 1.15%, and the total fluorine was 0.52%.

[0033] Comparative Example 3 The method and steps are the same as those in Example 2. The foaming agent methyl isobutyl carbinol in the composite purifier formula is removed, and the slurry purification flotation is performed. It is detected that the TOC in Comparative Example 1 is 1540 ppm, the whiteness in the phosphogypsum is 40.7%, the purity is 89.6%, the total phosphorus is 1.7%, and the total fluorine is 0.72%.

[0034] Comparative Example 4 The method and steps are the same as those in Example 2. The amine agent alkanolamide in the composite purifier formula is removed, and the slurry purification flotation is performed. It is detected that the TOC in Comparative Example 1 is 695 ppm, the whiteness in the phosphogypsum is 53.7%, the purity is 90.8%, the total phosphorus is 1.81%, and the total fluorine is 0.77%.

[0035] Example 3 (1) Phosphate concentrate and phosphorus-sulfur mixed acid solution were mixed at a mass ratio of 1:2.0, and dissolved at 83°C for 1.5 hours to obtain a reaction slurry. The P2O5 component in the phosphate concentrate was 32.5%, and sulfuric acid, phosphoric acid and water were prepared at a mass ratio of 1:0.64:1.

[0036] (2) Add 0.62 kg / t of composite purifier to the reaction slurry, stir for 3 minutes to obtain a mixed slurry, and perform flotation separation on the mixed slurry to obtain a foam product and an in-tank product. The composite purifier is a compound of a foaming agent and an amine agent, wherein the foaming agent comprises dimethyl benzyl alcohol and alkyl aromatic hydrocarbons, which are configured in a mass ratio of 4:3; the amine agent comprises dodecyl-N-carboxyethyl imidazoline, triethyltetramine, and laurylamine acetate, which are configured in a mass ratio of 2:5:2.

[0037] (3) The foam product is subjected to solid-liquid separation to obtain solid organic matter and silicate impurities, and the liquid agent acid is recycled into the reaction slurry of step (2), thereby reducing the amount of composite purifier used and reducing costs.

[0038] (4) The product in the tank is separated into solid and liquid to obtain solid phosphogypsum and liquid phosphoric acid.

[0039] (5) After three countercurrent washings of the solid phosphogypsum, it is transported to the phosphogypsum storage yard by belt conveyor, and the liquid phosphoric acid is pumped into the dilute phosphoric acid aging tank for aging.

[0040] The measured TOC of phosphoric acid in Example 3 was 180 ppm, the whiteness of phosphogypsum was 61.2%, the purity was 93.6%, the total phosphorus was 1.21%, and the total fluorine was 0.51%.

[0041] Comparative Example 5 The method and steps are the same as those in Example 3. The foaming agent alkane aromatic hydrocarbons in the composite purifier formula are removed, and the slurry purification flotation is performed. It is detected that the TOC in Comparative Example 1 is 1590 ppm, the whiteness in the phosphogypsum is 41.3%, the purity is 90.45%, the total phosphorus is 1.8%, and the total fluorine is 0.78%.

[0042] Comparative Example 6 The method and steps are the same as those in Example 3. The amine agent dodecyl-N-carboxyethyl imidazoline in the composite purifier formula is removed, and the slurry purification flotation is performed. It is detected that the TOC in Comparative Example 1 is 710 ppm, the whiteness in the phosphogypsum is 54.6%, the purity is 89.76%, the total phosphorus is 1.9%, and the total fluorine is 0.67%.

[0043] Example 4 (1) Phosphate concentrate and phosphorus-sulfur mixed acid solution were mixed in a mass ratio of 1:2.3, and dissolved at 75°C for 2 hours to obtain a reaction slurry. The P2O5 component in the phosphate concentrate was 33.6%, and sulfuric acid, phosphoric acid and water were prepared in a mass ratio of 1:0.56:1.

[0044] (2) Add 0.55 kg / t of composite purifier to the reaction slurry, stir for 3 minutes to obtain a mixed slurry, and perform flotation separation on the mixed slurry to obtain a foam product and an in-tank product. The composite purifier is a compound of a foaming agent and an amine agent, wherein the foaming agent comprises eucalyptus oil and polyvinyl alcohol, which are configured in a mass ratio of 1:1; the amine agent comprises trimethyl hexadecyl ammonium bromide, laurylamine hydrochloride, and amylphenyl ether amine, which are configured in a mass ratio of 3:4:2.

[0045] (3) The foam product is subjected to solid-liquid separation to obtain solid organic matter and silicate impurities, and the liquid agent acid is recycled into the reaction slurry of step (2), thereby reducing the amount of composite purifier used and reducing costs.

[0046] (4) The product in the tank is separated into solid and liquid to obtain solid phosphogypsum and liquid phosphoric acid.

[0047] (5) After three countercurrent washings of the solid phosphogypsum, it is transported to the phosphogypsum storage yard by belt conveyor, and the liquid phosphoric acid is pumped into the dilute phosphoric acid aging tank for aging.

[0048] The measured TOC of phosphoric acid in Example 4 was 178 ppm, the whiteness of phosphogypsum was 61.7%, the purity was 92.8%, the total phosphorus was 1.13%, and the total fluorine was 0.49%.

[0049] Comparative Example 7 The method and steps are the same as those in Example 4. The foaming agent eucalyptus oil in the composite purifier formula is removed, and the slurry purification flotation is performed. It is detected that the TOC in Comparative Example 1 is 1550ppm, the whiteness in the phosphogypsum is 39.2%, the purity is 90.12%, the total phosphorus is 1.66%, and the total fluorine is 0.75%.

[0050] Comparative Example 8 The method and steps are the same as those in Example 4. The amine agent amylphenyl ether amine in the composite purifier formula is removed, and the slurry purification flotation is performed. It is detected that the TOC in Comparative Example 1 is 802 ppm, the whiteness in the phosphogypsum is 53.9%, the purity is 89.97%, the total phosphorus is 1.77%, and the total fluorine is 0.76%.

[0051] Example 5 (1) Phosphate concentrate and phosphorus-sulfur mixed acid solution were mixed in a mass ratio of 1:2.6, and dissolved at 90°C for 1.8 hours to obtain a reaction slurry. The P2O5 component in the phosphate concentrate was 30.8%, and sulfuric acid, phosphoric acid and water were prepared in a mass ratio of 1:0.7:1.

[0052] (2) Add 0.77 kg / t of composite purifier to the reaction slurry, stir for 3 minutes to obtain a mixed slurry, and perform flotation separation on the mixed slurry to obtain a foam product and an in-tank product. The composite purifier is a compound of a foaming agent and an amine agent, wherein the foaming agent comprises pine oil and polyvinyl alcohol in a mass ratio of 1:2; the amine agent comprises alkyl benzyl pyridine, laurylamine hydrochloride, and denatured rosin amine in a mass ratio of 2:2:4.

[0053] (3) The foam product is subjected to solid-liquid separation to obtain solid organic matter and silicate impurities, and the liquid agent acid is recycled into the reaction slurry of step (2), thereby reducing the amount of composite purifier used and reducing costs.

[0054] (4) The product in the tank is separated into solid and liquid to obtain solid phosphogypsum and liquid phosphoric acid.

[0055] (5) After three countercurrent washings of the solid phosphogypsum, it is transported to the phosphogypsum storage yard by belt conveyor, and the liquid phosphoric acid is pumped into the dilute phosphoric acid aging tank for aging.

[0056] The measured TOC of phosphoric acid in Example 5 was 133 ppm, the whiteness of phosphogypsum was 62.6%, the purity was 93.8%, the total phosphorus was 1.14%, and the total fluorine was 0.52%.

[0057] Comparative Example 9 The method and steps are the same as those in Example 5. The foaming agent polyvinyl alcohol in the composite purifier formula is removed, and the slurry purification flotation is performed. It is detected that the TOC in Comparative Example 1 is 1580 ppm, the whiteness in the phosphogypsum is 38.8%, the purity is 88.9%, the total phosphorus is 1.73%, and the total fluorine is 0.7%.

[0058] Comparative Example 10 The method and steps are the same as those in Example 5. The amine agent denatured rosin amine in the composite purifier formula is removed, and the slurry purification flotation is performed. It is detected that the TOC in Comparative Example 1 is 745 ppm, the whiteness in the phosphogypsum is 52.7%, the purity is 90.1%, the total phosphorus is 1.78%, and the total fluorine is 0.72%.

[0059] The above description is only a preferred embodiment of the present invention, and is not intended to limit the implementation scheme. It should be noted that it is possible for a person skilled in the art to make several improvements and changes without departing from the creative concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for purifying phosphogypsum in a wet phosphoric acid production process, characterized in that: The following steps are included (1) mixing phosphate concentrate with phosphorus-sulfur mixed acid solution and dissolving the mixture to obtain a reaction slurry; (2) After the composite purifier is uniformly mixed with the reaction slurry described in step (1), flotation separation is performed to obtain a foam product and a purified and impurity-free slurry; (3) filtering and washing the purified slurry in step (2) to obtain wet-process phosphoric acid and phosphogypsum; (4) After solid-liquid separation of the foam product in step (2), a liquid phase reagent and a solid phase residue are obtained. The reagent can be recycled as a composite purifier for purifying and removing impurities in the reaction slurry, and the residue can be treated as tailings.

2. The method for purifying phosphogypsum in the wet phosphoric acid production process according to claim 1, characterized in that: The composite purifier raw materials include a foaming agent and an amine agent.

3. The method for purifying phosphogypsum in the wet process phosphoric acid production process according to claim 2, characterized in that: The foaming agent comprises one or more of pine oil, eucalyptus oil, methyl isobutyl carbinol, dimethyl benzyl alcohol, polyvinyl alcohol and alkane aromatic hydrocarbons.

4. The method for purifying phosphogypsum in the wet phosphoric acid production process according to claim 2, characterized in that: The amine agents include one or more of laurylamine acetate, laurylamine hydrochloride, triethyltetramine, dihexadecyldimethylammonium acetate, alkylbenzylpyridine, trimethylhexadecylammonium bromide, amylphenyl ether amine, denatured rosin amine, alkanolamide, and dodecyl-N-carboxyethyl imidazoline.

5. The method for purifying phosphogypsum in the wet process phosphoric acid production process according to claim 1, characterized in that: The P2O5 grade in the phosphate concentrate described in step (1) is 25%-36%; the mass ratio of the phosphate concentrate to the phosphorus-sulfur mixed acid solution is 1:(1.5-2.6).

6. The method for purifying phosphogypsum in the wet process phosphoric acid production process according to claim 5, characterized in that: In the phosphorus-sulfur mixed acid solution, sulfuric acid, phosphoric acid and water are uniformly mixed in a mass ratio of 1: (0.5-1): 1, wherein the mass concentration of sulfuric acid is above 98%, and the mass concentration of phosphoric acid is above 85%.

7. The method for purifying phosphogypsum in the wet phosphoric acid production process according to claim 1, characterized in that: The dissolution temperature of step (1) is 70-90°C; the dissolution time is (30-240min).

8. The method for purifying phosphogypsum in the wet process phosphoric acid production process according to claim 1, characterized in that: The dosage of the composite purifier is 0.4-1 kg / t.

9. The method for purifying phosphogypsum in the wet process phosphoric acid production process according to claim 1, characterized in that: The liquid reagent obtained in step (4) is recycled and reused in step (2).

10. A method for purifying phosphogypsum in a wet phosphoric acid production process according to any one of claims 1 to 9, characterized in that: The purification method is to add a composite purifier into the reaction slurry to physically separate the organic matter and insoluble impurities therein, thereby achieving the purpose of purifying phosphoric acid and phosphogypsum.

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