Phosphogypsum and method for extracting phosphoric acid from thermalized phosphate concentrate and capable of improving quality of phosphogypsum

Abstract

The invention relates to the technical field of ardealite quality improvement, in particular to a method for extracting phosphoric acid from thermalized phosphate concentrate and ardealite, and the method can improve the quality of the ardealite. Phosphorus concentrate beneficiation process parameters and key process parameters in the sulfuric acid extraction process of the phosphorus concentrate are strictly controlled, so that in the process of producing phosphoric acid through sulfuric acid extraction of the phosphorus concentrate, the ardealite crystal form control difficulty is reduced, the condition deterioration influence of impurities on the ardealite generation process is weakened, the effect of the ardealite filtering and washing process is guaranteed, and the ardealite quality is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of improving the quality of phosphogypsum, and in particular to a method for extracting phosphoric acid from thermally selected phosphate concentrate and phosphogypsum capable of improving the quality of phosphogypsum. Background Art

[0002] Phosphogypsum is a solid waste residue produced by the wet phosphoric acid process. About 4-6 tons of phosphogypsum are discharged for every ton of phosphoric acid produced. The main component of phosphogypsum is calcium sulfate dihydrate, which contains various impurities such as phosphorus, fluorine, and iron. The presence of these impurities greatly restricts the resource utilization of phosphogypsum. Therefore, when phosphogypsum is utilized as a resource, it is necessary to pre-treat the phosphogypsum to eliminate or reduce the impact of impurities on the resource utilization of phosphogypsum.

[0003] For example: Patent application No. 201510846035.1 discloses that in order to realize the recycling of phosphogypsum resources and meet the requirements of PVC material production and application as filler, phosphogypsum is modified to reduce the impact of impurities and improve whiteness. Another example: Patent application No. 202210625383.6 discloses that in order to realize the recycling of phosphogypsum resources and improve the performance of road asphalt, phosphogypsum is efficiently purified to improve the purity of phosphogypsum.

[0004] It can be seen that the prior art requires pretreatment or modification of the phosphogypsum produced by the wet phosphoric acid process in order to make the phosphogypsum discharged by the wet phosphoric acid process of better quality and to be utilized as a resource. However, there is no relevant report on whether the mineral processing technology before the wet phosphoric acid process and the wet phosphoric acid extraction and washing process leaching can be directly improved to make the phosphogypsum produced by the wet phosphoric acid process of better quality and directly utilized as a resource within a certain range.

[0005] In view of this, this research team combined the improvement of thermal phosphate concentrate technology and properly controlled the key process parameters of the sulfuric acid extraction of phosphate concentrate, which reduced the difficulty of controlling the gypsum crystal form generated during the sulfuric acid extraction reaction, weakened the deterioration of conditions affecting the formation of phosphogypsum by impurities, and ensured better filtering and washing effects of phosphogypsum, thereby providing new ideas for the production of high-quality phosphogypsum from sulfuric acid extraction of phosphate concentrate with phosphoric acid. Summary of the invention

[0006] The invention provides a method for extracting phosphoric acid from thermally concentrated phosphate ore and phosphogypsum, which can improve the quality of phosphogypsum. The technical solution is:

[0007] A method for extracting phosphoric acid from thermally concentrated phosphate ore capable of improving the quality of phosphogypsum comprises the following steps:

[0008] (1) calcining the phosphate ore, adding water for digestion treatment, then adding ammonium nitrate solution for leaching, filtering, and obtaining phosphate concentrate and nitrate solution; removing magnesium and calcium from the nitrate solution in sequence to prepare a regenerated ammonium nitrate solution; the leaching temperature of the ammonium nitrate solution is consistent with the digestion treatment temperature, and the digestion treatment is carried out by constant temperature treatment with hot water at 60-80°C;

[0009] (2) Sulfuric acid is used to extract the phosphate concentrate, and phosphoric acid and filter residue are obtained by filtration. The filter residue is washed three times to obtain phosphogypsum; and the amount of sulfuric acid added is controlled so that 0.5-1% by weight of sulfate ions are in a free state during the extraction process. At the same time, seed crystals accounting for 5% by weight of the phosphate concentrate are added during the extraction; the seed crystals are calcium sulfate slurry obtained by grinding with water in a ball mill and passing through an 800-1000 mesh sieve.

[0010] The thermal phosphate concentrate selection process is used to control the digestion treatment temperature and the ammonium nitrate solution leaching temperature to ensure the quality of the phosphate concentrate. Combined with the control of the amount of sulfuric acid added and the crystal seed addition in the phosphoric acid extraction process of the phosphate concentrate, the difficulty of controlling the crystal form of phosphogypsum in the sulfuric acid extraction process of the phosphate concentrate is reduced, the impact of impurities on the deterioration of conditions in the phosphogypsum formation process is weakened, the effect of the phosphogypsum filtering and washing process is ensured, and the quality of the phosphogypsum is improved.

[0011] The invention uses calcium sulfate to grind with water to prepare calcium sulfate slurry as a crystal seed, and grinds with water at a mass ratio of calcium sulfate to water of 1:10-20, thereby fully ensuring the hydration of the calcium sulfate component and avoiding the influence of insufficient hydration on the crystal form of phosphogypsum by adding crystal seeds.

[0012] In order to ensure the extraction efficiency and extraction effect and meet the crystallization of phosphogypsum, preferably, the extraction temperature is 69-72°C and the extraction time is 3-3.5h.

[0013] In order to fully decompose dolomite and calcite, preferably, the calcination is carried out at a temperature of 900-1100° C. for 1-2 hours. More preferably, the digestion treatment is carried out for 30-90 minutes.

[0014] In order to enable calcium, magnesium and other components to be fully leached out, reduce the content of calcium, magnesium and other components in phosphate concentrate, and then ensure the concentrated defluorination performance of phosphoric acid prepared by wet phosphoric acid process, preferably, the concentration of the ammonium nitrate solution is 15-30%. More preferably, the leaching is to add the ammonium nitrate solution and the digested phosphate ore into the leaching tank, and stir at a stirring speed of 400-600r / min for 1-2h.

[0015] In order to realize the recycling of ammonium nitrate solution and ensure that the process produces by-products and improve the added value of the entire process, preferably, the preparation of the regenerated ammonium nitrate solution is to pass the ammonia generated by leaching the ammonium nitrate solution into a nitrate solution, filter to obtain a magnesium-removing liquid and a magnesium-containing slag, and dry the magnesium-containing slag to obtain magnesium hydroxide; pass the carbon dioxide generated by calcination and the ammonia generated by leaching the ammonium nitrate solution into the magnesium-removing liquid, filter to obtain a regenerated ammonium nitrate solution and a calcium-containing slag; return the regenerated ammonium nitrate solution for circulating leaching treatment, and dry the calcium-containing slag to obtain calcium carbonate.

[0016] The technical effects of the present invention are as follows:

[0017] By combining the thermal phosphate concentrate beneficiation technology with the sulfuric acid extraction technology, strictly controlling the phosphate concentrate beneficiation process parameters and the key process parameters of the sulfuric acid extraction process, the difficulty of controlling the crystal form of phosphogypsum in the production of phosphoric acid from phosphate concentrate is reduced, the impact of impurities on the deterioration of conditions in the phosphogypsum formation process is weakened, the effect of the phosphogypsum filtering and washing process is guaranteed, and the quality of phosphogypsum is improved.

[0018] The content of calcium sulfate dihydrate in the output phosphogypsum created by the present invention reaches more than 96%, and the water-soluble phosphorus content is reduced to less than 0.2%, and the whiteness reaches more than 85, so it can be directly used, which greatly improves the quality of the output phosphogypsum by the wet phosphoric acid process, helps to accelerate the resource utilization of phosphogypsum, and reduce the cost of resource utilization of phosphogypsum. DETAILED DESCRIPTION

[0019] In order to facilitate those skilled in the art to correctly understand the present invention and enable those skilled in the art to fully understand the technical content of the present invention, the technical solution of the present invention is further explained below in conjunction with specific implementation methods. However, this explanation does not limit the scope of protection required for the present invention. The scope of protection of the present invention by those skilled in the art cannot be limited to the following explanations. Any equivalent substitutions or changes made by any those skilled in the art or persons familiar with the technology in the art based on the present invention and the technical solution and inventive concept thereof should be covered within the scope of protection of the present invention.

[0020] In certain embodiments, a method for extracting phosphoric acid from thermally concentrated phosphate ore capable of improving the quality of phosphogypsum comprises the following steps:

[0021] (1) Calcine the phosphate rock at 900-1100° C., for example, 900° C., 980° C., 1000° C., 1100° C., etc. for 1-2 h, for example, 1 h, 1.5 h, 2 h, etc., and add hot water at 60-80° C., for example, 60° C., 63.5° C., 65.5° C., 67° C., 68.5° C., 72° C., 74.5° C., 78° C., 80° C., 83° C., etc. for digestion for 30-90 min, for example, 30 min, 40 min, 45 min, 60 min in, 70min, 80min, 90min, etc., then adding ammonium nitrate solution with a mass percentage concentration of 15-30%, for example: 15%, 17%, 20%, 25%, 30%, etc., and leaching for 1-2h, for example 1h, 1.5h, 2h, etc., filtering to obtain phosphate concentrate and nitrate solution; the nitrate solution is sequentially demagnesized and decalcified to prepare a regenerated ammonium nitrate solution; the temperature of the ammonium nitrate solution leaching is consistent with the temperature of the digestion treatment, and the digestion treatment is a constant temperature treatment;

[0022] (2) extracting the phosphate concentrate with sulfuric acid at 69-72° C., for example, 69° C., 70° C., 71° C., 72° C., etc. for 3-3.5 h, for example, 3 h, 3.1 h, 3.2 h, 3.3 h, 3.4 h, 3.5 h, etc., filtering to obtain phosphoric acid and filter residue, and washing the filter residue three times to obtain phosphogypsum; and controlling the amount of sulfuric acid added during the extraction process to have a mass percentage of 0.5-1%, for example, 0.5%, 0.6%, 0.7%, 0. 9%, 1%, etc. of sulfate radicals are in a free state. Meanwhile, crystal seeds accounting for 5% of the mass of the phosphate concentrate are added during extraction; the crystal seeds are calcium sulfate slurry obtained by mixing calcium sulfate and water in a mass ratio of 1:10-20, for example, 1:10, 1:15, 1:20, etc., grinding with water in a ball mill, and sieving through 800-1000 mesh, for example, 800 mesh, 880 mesh, 900 mesh, 920 mesh, 950 mesh, 990 mesh, 1000 mesh, etc.

[0023] In some embodiments, the leaching is performed by adding the ammonium nitrate solution and the digested phosphate rock into the leaching tank, and then stirring and leaching at a stirring speed of 400-600 r / min. This helps to accelerate the conversion of calcium and magnesium components into calcium nitrate, magnesium nitrate and other components and enter the solution, thereby improving the processing efficiency.

[0024] In some embodiments, the preparation of the regenerated ammonium nitrate solution is to pass the ammonia generated by the leaching of the ammonium nitrate solution into the nitrate solution, filter, obtain the magnesium-removing solution and the magnesium-containing slag, and dry the magnesium-containing slag to obtain magnesium hydroxide; pass the carbon dioxide generated by calcination and the ammonia generated by the leaching of the ammonium nitrate solution into the magnesium-removing solution, filter, obtain the regenerated ammonium nitrate solution and the calcium-containing slag; return the regenerated ammonium nitrate solution to the cyclic leaching treatment, and dry the calcium-containing slag to obtain calcium carbonate. The regeneration and recycling of the ammonium nitrate solution is realized, and the processing cost is reduced.

[0025] In order to better verify the technical effect of the present invention, the researchers of the present invention carried out the following experimental research (each set of experimental data was measured three times and the average value was taken):

[0026] The low- and medium-grade phosphate rock used in the present invention comes from a phosphorus chemical enterprise in Guizhou, and the composition of the phosphate rock is shown in Table 1 below:

[0027] Table 1 wt%

[0028]

[0029] In the laboratory, the medium and low-grade phosphate ore in Table 1 was subjected to thermal phosphate concentrate treatment: the phosphate ore was calcined, digested with water, leached with ammonium nitrate solution and filtered to obtain phosphate concentrate and nitrate solution. The nitrate solution was used for demagnesization and decalcification and then regenerated into ammonium nitrate solution. In order to improve the leaching efficiency and shorten the laboratory treatment time, the stirring speed was 500r / min during the leaching process. The specific process parameters of the phosphate concentrate preparation process are shown in Table 2 below:

[0030] Table 2

[0031]

[0032] The phosphorus and magnesium contents of the phosphate concentrates obtained in Table 2 (samples 1 to 9) were tested, and the results are shown in Table 3 below:

[0033] Table 3 wt%

[0034]

[0035] Samples 1 to 9 obtained in Table 3 were respectively extracted with sulfuric acid to prepare phosphoric acid, and during the extraction preparation process, the extraction temperature was controlled to be 70°C, the extraction time was 3h, and the amount of sulfuric acid added was controlled to have 0.5% by mass of sulfate in a free state during the extraction process. At the same time, crystal seeds accounting for 5% of the mass of the phosphate concentrate were added during the extraction; the crystal seeds were calcium sulfate slurry obtained by mixing calcium sulfate and water in a mass ratio of 1:10, grinding with water in a ball mill and passing through an 800-mesh sieve; after the extraction was completed, phosphoric acid and filter residue were obtained by filtration, and the filter residue was washed three times to obtain phosphogypsum. Calcium sulfate dihydrate, insoluble phosphorus, water-soluble phosphorus and whiteness in phosphogypsum were tested, and the results are shown in Table 4 below:

[0036] Table 4

[0037]

[0038] As can be seen from Table 4, after the phosphate concentrate obtained by the invention is extracted using the sulfuric acid method to prepare phosphoric acid, the obtained phosphogypsum has better quality and can be directly utilized, which helps to reduce the storage of phosphogypsum generated by the wet phosphoric acid process to produce phosphoric acid and reduce the cost of resource utilization of phosphogypsum.

[0039] The invention improves the beneficiation process of phosphate concentrate for wet phosphoric acid, and combines the improvement and research on the process parameters of phosphoric acid extraction by wet phosphoric acid using sulfuric acid method, so that the content of calcium sulfate dihydrate in phosphogypsum produced by extracting phosphoric acid by wet phosphoric acid using sulfuric acid method reaches more than 96%, and the water-soluble phosphorus is reduced to less than 2%, and the whiteness reaches more than 85, thereby greatly improving the quality of phosphogypsum, achieving the direct production of phosphogypsum from the wet phosphoric acid process and being directly utilized as a resource, which helps to reduce the stockpile of phosphogypsum, and reduces the cost caused by the stockpile of phosphogypsum or the modification treatment before the resource utilization of phosphogypsum in the phosphorus chemical industry.

[0040] Other matters not covered by the present invention may be achieved by conventional technical means with reference to the prior art or common knowledge known to those skilled in the art. For example, the control of process parameters when demagnesizing and decalcifying nitrate solution to regenerate ammonium nitrate solution may be performed with reference to the process parameters and process steps disclosed in the prior art (for example, patent application number 201811203660.4).

Claims

1. A method for extracting phosphoric acid from thermally concentrated phosphate ore capable of improving the quality of phosphogypsum, characterized in that: The following steps are involved: (1) calcining the phosphate ore, adding water for digestion treatment, then adding ammonium nitrate solution for leaching, filtering, and obtaining phosphate concentrate and nitrate solution; The nitrate solution is sequentially demagnesized and decalcified to prepare a regenerated ammonium nitrate solution; The leaching temperature of the ammonium nitrate solution is consistent with the temperature of the digestion treatment, and the digestion treatment is carried out by using hot water at a constant temperature of 60-80°C; (2) Sulfuric acid is used to extract the phosphate concentrate, and phosphoric acid and filter residue are obtained by filtration. The filter residue is washed three times to obtain phosphogypsum; and the amount of sulfuric acid added is controlled so that 0.5-1% by weight of sulfate ions are in a free state during the extraction process. At the same time, seed crystals accounting for 5% by weight of the phosphate concentrate are added during the extraction; the seed crystals are calcium sulfate slurry obtained by grinding with water in a ball mill and passing through an 800-1000 mesh sieve.

2. The method for extracting phosphoric acid from thermal phosphate concentrate capable of improving the quality of phosphogypsum according to claim 1, characterized in that: The extraction temperature is 69-72° C., and the extraction time is 3-3.5 h.

3. The method for extracting phosphoric acid from thermal phosphate concentrate capable of improving the quality of phosphogypsum as claimed in claim 1, characterized in that: The calcination is carried out at a temperature of 900-1100° C. for 1-2 hours.

4. The method for extracting phosphoric acid from thermal phosphate concentrate capable of improving the quality of phosphogypsum according to claim 1, characterized in that: The digestion process lasts for 30-90 minutes.

5. The method for extracting phosphoric acid from thermal phosphate concentrate capable of improving the quality of phosphogypsum as claimed in claim 1, characterized in that: The concentration of the ammonium nitrate solution is 15-30%.

6. The method for extracting phosphoric acid from thermal phosphate concentrate capable of improving the quality of phosphogypsum according to claim 1, characterized in that: The leaching is performed by adding the ammonium nitrate solution and the digested phosphate rock into a leaching tank, and stirring them at a stirring speed of 400-600 r / min for 1-2 hours.

7. The method for extracting phosphoric acid from thermal phosphate concentrate capable of improving the quality of phosphogypsum as claimed in claim 1, characterized in that: The preparation of the regenerated ammonium nitrate solution comprises the following steps: introducing ammonia generated by leaching the ammonium nitrate solution into a nitrate solution, filtering to obtain a de-magnesiumizing solution and a magnesium-containing slag, and drying the magnesium-containing slag to obtain magnesium hydroxide; introducing carbon dioxide generated by calcination and ammonia generated by leaching the ammonium nitrate solution into the de-magnesiumizing solution, filtering to obtain a regenerated ammonium nitrate solution and a calcium-containing slag; returning the regenerated ammonium nitrate solution for a cyclic leaching treatment, and drying the calcium-containing slag to obtain calcium carbonate.

8. Phosphogypsum obtained by the method according to any one of claims 1 to 7.

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