Phosphorus concentrate thermalization method capable of improving wet-process phosphoric acid concentration defluorination performance and phosphorus concentrate

Abstract

The invention relates to the technical field of wet-process phosphoric acid, in particular to a thermalization phosphate concentrate separation method capable of improving wet-process phosphoric acid concentration defluorination performance and phosphate concentrate.The method comprises the steps that phosphorite is calcined so that dolomite and calcite embedded in the phosphorite can be decomposed, hot water digestion is utilized for constant-temperature digestion treatment, then an ammonium nitrate solution is adopted for constant-temperature leaching, and the phosphorus concentrate is obtained; according to the method, calcium and magnesium components form calcium nitrate and magnesium nitrate to enter the solution, then the solution is filtered to obtain phosphate concentrate, the leaching temperature is controlled to be consistent with the digestion temperature, a large amount of calcium, magnesium and other components are promoted to enter the solution, the concentration and defluorination performance of phosphoric acid prepared from the phosphate concentrate through a wet-process phosphoric acid process is facilitated, and the phosphoric acid concentration and quality improvement difficulty is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of wet-process phosphoric acid, and in particular to a thermal phosphate concentrate separation method and a phosphate concentrate capable of improving the concentration and defluorination performance of wet-process phosphoric acid. Background Art

[0002] With the development and utilization of phosphate resources, the utilization of medium and low-grade phosphate ores has been rapidly developed and studied, and a large number of technologies for the chemical treatment of medium and low-grade phosphate ores to prepare high-quality low-magnesium phosphate concentrates have been formed. For example: Patent application No. 201510226362.7 discloses a process for producing calcium carbonate and magnesium oxide as by-products of phosphate concentrate from medium and low-grade phosphate ores, and calcining, digesting, leaching and precipitating medium and low-grade phosphate ores at 900-1100°C to obtain phosphate concentrate. Another example: Patent application No. 201410744065.7 discloses a method for using phosphate tailings as raw materials to produce magnesium hydroxide, calcium carbonate and separate phosphate ore using an ammonia circulation method. Another example: Patent application No. 201811203660.4 discloses a process for enriching phosphate concentrate from medium- and low-grade phosphate ore or phosphate tailings and recovering calcium carbonate and magnesium hydroxide at the same time, so as to solve the environmental risks brought about by the existing phosphate ore using two flotation to enrich phosphate concentrate. The phosphate ore or tailings are calcined and decomposed at 700-1200°C, and ammonium nitrate solution is used to leach the leaching solution A and the leaching residue a. Ammonia and carbon dioxide are introduced into the leaching solution A to first separate the calcium carbonate; the leaching residue a reacts with the ammonium nitrate solution to obtain the leaching solution C and the leaching residue c. The leaching residue c is the phosphate concentrate, and ammonia or ammonia water is added to the leaching solution C to separate the magnesium hydroxide.

[0003] It can be seen that the thermal beneficiation of low- and medium-grade phosphate ore and phosphate tailings in the prior art to improve the quality of phosphate concentrate has attracted the attention of those skilled in the art. However, phosphate ore generally contains impurities such as calcium, magnesium, and fluorine, which cannot be completely removed during the beneficiation process to improve the quality of phosphate concentrate, making it difficult to prepare phosphoric acid and concentrate and recover fluorine in the wet phosphoric acid process, resulting in poor performance of phosphoric acid prepared by the wet phosphoric acid process after concentration and defluorination. Summary of the invention

[0004] Based on the above technical problems, the present invention provides a method for thermally selecting phosphate concentrate and a phosphate concentrate capable of improving the concentration and defluorination performance of wet-process phosphoric acid.

[0005] The specific technical solution is:

[0006] One of the purposes of the present invention is to provide a method for thermally selecting phosphate concentrate capable of improving the concentrated defluorination performance of wet-process phosphoric acid, comprising the following steps:

[0007] (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;

[0008] (2) The nitrate solution is subjected to sequential demagnesization and decalcification 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 a constant temperature treatment of 60-80°C hot water.

[0009] The phosphate ore is calcined to decompose the dolomite and calcite embedded in the phosphate ore, and is digested at a constant temperature using hot water. The ammonium nitrate solution is then used for constant temperature leaching to make the calcium and magnesium components form calcium nitrate and magnesium nitrate and enter the solution. The phosphate concentrate is then filtered to obtain the phosphate concentrate. The leaching temperature is controlled to be consistent with the digestion temperature, so that calcium, magnesium and other components enter the solution in large quantities, which helps to improve the concentrated defluorination performance of phosphoric acid prepared from the phosphate concentrate by a wet phosphoric acid process and reduce the difficulty of concentrating and improving the quality of phosphoric acid.

[0010] 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.

[0011] 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.

[0012] In order to realize the recycling of ammonium nitrate solution and ensure that the process produces by-products, thereby increasing the added value of the entire process, preferably, the step (2) is to pass the ammonia generated by leaching the ammonium nitrate solution into a nitrate solution, filter it, and obtain a magnesium-removing solution and a magnesium-containing slag, and the magnesium-containing slag is dried to obtain magnesium hydroxide; the carbon dioxide generated by calcination and the ammonia generated by leaching the ammonium nitrate solution are passed into the magnesium-removing solution, filter it, and obtain a regenerated ammonium nitrate solution and a calcium-containing slag; the regenerated ammonium nitrate solution is returned to the circulating leaching treatment, and the calcium-containing slag is dried to obtain calcium carbonate.

[0013] In order to improve the concentration and defluorination performance of preparing phosphoric acid from wet-process phosphoric acid with phosphate concentrate and reduce the difficulty of concentration, it is more preferred that the leaching temperature of the ammonium nitrate solution is 68.5°C.

[0014] The second purpose of the present invention is to provide the phosphate concentrate obtained by the above method.

[0015] Compared with the prior art, the technical effects created by the present invention are embodied in:

[0016] The invention adopts a thermal phosphate concentrate beneficiation process to beneficiate medium- and low-grade phosphate ore, phosphate tailings, etc., and properly controls the process digestion and leaching process parameters of the thermal phosphate concentrate beneficiation process, and uses a wet phosphoric acid process to prepare phosphoric acid from the obtained phosphate concentrate, so that the defluorination rate of the phosphoric acid after concentration and defluorination reaches more than 70%, thereby improving the concentration and defluorination performance of the phosphoric acid obtained by the wet phosphoric acid process. DETAILED DESCRIPTION

[0017] 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.

[0018] In certain embodiments, a method for thermally separating phosphate concentrate capable of improving the concentrated defluorination performance of wet-process phosphoric acid comprises the following steps:

[0019] (1) calcining 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., adding 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, 70 min, 80 min, 90 min, etc., then adding ammonium nitrate solution with a mass percentage concentration of 15-30%, for example, 15%, 17%, 20%, 25%, 30%, etc., leaching for 1-2 h, for example, 1 h, 1.5 h, 2 h, etc., filtering to obtain a phosphate concentrate and a nitrate solution;

[0020] (2) The nitrate solution is subjected to sequential demagnesization and decalcification 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 a constant temperature treatment.

[0021] Phosphate ore (medium- and low-grade phosphate ore or phosphate tailings) is calcined to fully decompose calcium and magnesium components in the phosphate ore into calcium oxide and magnesium oxide components, and then treated with hot water to form calcium hydroxide and magnesium hydroxide, and then leached with ammonium nitrate solution to dissolve the calcium and magnesium components in the ammonium nitrate solution to form calcium nitrate, magnesium nitrate and other components, and then filtered to obtain phosphate concentrate, and combined with the proper control of the digestion treatment temperature and the leaching treatment temperature, the quality of the obtained phosphate concentrate is guaranteed, so that after it is used in the wet phosphoric acid preparation process to prepare phosphoric acid, the phosphoric acid concentration and defluorination performance is improved, and the difficulty of phosphoric acid concentration is reduced.

[0022] 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.

[0023] In certain embodiments, the step (2) is to pass the ammonia generated by leaching 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 leaching 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 ammonium nitrate solution is regenerated and recycled, the processing cost is reduced, and calcium carbonate and magnesium hydroxide by-products can be produced at the same time, the product added value of the process flow is increased, and the process cost is reduced.

[0024] In order to better verify the technical effect that the invention can bring, the researchers of the invention carried out the following experimental research in the laboratory (each set of experimental data was measured three times and the average value was taken):

[0025] 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:

[0026] Table 1 wt%

[0027]

[0028] 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:

[0029] Table 2

[0030]

[0031] 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:

[0032] Table 3 wt%

[0033]

[0034] Samples 1 to 9 were respectively extracted with sulfuric acid to prepare phosphoric acid, the extraction time was controlled at 3-3.5h, the extraction temperature was controlled at 69-72°C, the mass percentage concentration of sulfuric acid was 70%, and phosphoric acid was prepared and filtered according to the sulfuric acid wet phosphoric acid process to obtain filtered acid, and the contents of P2O5 and F in the filtered acid were detected, and the results are shown in Table 4 below:

[0035] Table 4 wt%

[0036]

[0037] The filtered acid obtained in Table 4 was concentrated by heat exchange, and the sludge deposition was observed during the concentration process. When sludge deposition appeared, the concentration was stopped, and the contents of P2O5 and F in the filtered acid after concentration (wt%) were detected. The F escape rate (%) was calculated in combination with Table 4. The results are shown in Table 5 below:

[0038] Table 5

[0039]

[0040] Note: F escape rate = [(F content before concentration - F content after concentration) ÷ F content before concentration] × 100%

[0041] It can be seen from Tables 4 and 5 that the process created by the present invention after appropriate calcination, digestion, and leaching treatment can help improve the concentration efficiency of phosphoric acid obtained by the sulfuric acid wet phosphoric acid process, reduce the concentration difficulty, and help improve the fluorine escape rate in the concentration process and increase the fluorine recovery rate. At the same time, it can be seen from Tables 4 and 5 that when the digestion treatment temperature is inconsistent with the leaching treatment temperature, the fluorine escape rate is affected. In view of this phenomenon, the research created by the present invention, based on sample 5, carried out experimental research after the temperature change of the digestion and leaching process, and detected the F content and calculated the F escape rate after the concentration of the filtered acid prepared by the sulfuric acid wet phosphoric acid, and the experimental research results were recorded as shown in Table 6:

[0042] Table 6

[0043]

[0044] Note: F escape rate = [(F content before concentration - F content after concentration) ÷ F content before concentration] × 100%

[0045] It can be seen from Tables 5 and 6 that when the temperature of the digestion treatment process is inconsistent with the temperature of the leaching treatment process, it will affect the F escape rate after the filtered acid is concentrated in the preparation of wet phosphoric acid using sulfuric acid, and further affect the efficiency of phosphoric acid concentration and F recovery in the wet phosphoric acid process.

[0046] Other matters not covered by the present invention can 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 removing magnesium from nitrate solution and decalcifying to regenerate ammonium nitrate solution can be operated with reference to the process parameters and process steps disclosed in the prior art.

Claims

1. A method for thermal separation of phosphate concentrate capable of improving the concentration and defluorination performance of wet-process phosphoric acid, 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; (2) preparing a regenerated ammonium nitrate solution by sequentially removing magnesium and calcium from the 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. The method for thermal separation of phosphate concentrate capable of improving the concentration and defluorination performance of wet-process phosphoric acid according to claim 1, characterized in that: The calcination is carried out at a temperature of 900-1100° C. for 1-2 hours.

3. The method for thermal separation of phosphate concentrate capable of improving the concentration and defluorination performance of wet-process phosphoric acid according to claim 1, characterized in that: The digestion process lasts for 30-90 minutes.

4. The method for thermal separation of phosphate concentrate capable of improving the concentration and defluorination performance of wet-process phosphoric acid according to claim 1, characterized in that: The concentration of the ammonium nitrate solution is 15-30%.

5. The method for thermal separation of phosphate concentrate capable of improving the concentration and defluorination performance of wet-process phosphoric acid 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.

6. The method for thermal separation of phosphate concentrate capable of improving the concentration and defluorination performance of wet-process phosphoric acid according to claim 1, characterized in that: The step (2) comprises: introducing ammonia generated by leaching ammonium nitrate solution into nitrate solution, filtering to obtain magnesium-removing solution and magnesium-containing slag, and drying the magnesium-containing slag to obtain magnesium hydroxide; introducing carbon dioxide generated by calcination and ammonia generated by leaching ammonium nitrate solution into magnesium-removing solution, filtering to obtain regenerated ammonium nitrate solution and calcium-containing slag; returning the regenerated ammonium nitrate solution for cyclic leaching treatment, and drying the calcium-containing slag to obtain calcium carbonate.

7. The method for thermal separation of phosphate concentrate capable of improving the concentration and defluorination performance of wet-process phosphoric acid according to claim 1, characterized in that: The leaching temperature of the ammonium nitrate solution is 68.5°C.

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

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