Method for decomposing and utilizing phosphate-potassium ore

Abstract

The present invention relates to a method for decomposing and utilizing phosphate-potassium ore, belonging to the technical field of phosphate-potassium ore treatment. The technical problem solved by the present invention is to provide a method for decomposing and utilizing phosphate-potassium ore. The method comprises the following steps: mixing nitric acid and phosphate-potassium ore, and carrying out an acidolysis reaction; after the reaction is completed, performing solid-liquid separation to obtain a phosphorus-containing filtrate and potassium-containing acid-insoluble substances; wherein, the leaching rate of potassium in the phosphate-potassium ore is ≤3%, and the leaching rate of phosphorus is ≥96%. The present invention for the first time uses nitric acid to treat phosphate-potassium ore, controls the reaction conditions of the acidolysis process to reduce the leaching rate of K element, realizes the separation of phosphorus and potassium elements, avoids the problem that potassium fluorosilicate precipitates and clogs the filter cloth during vacuum filtration and cooling, perfectly avoids the disadvantages of the traditional wet-process phosphoric acid for treating phosphate-potassium ore, and has rich products.

Description

Technical Field

[0001] The invention relates to a method for decomposing and utilizing phosphate-potash ore, and belongs to the technical field of phosphate-potash ore processing. Background Art

[0002] The development and utilization of potassium phosphate ores can not only find new methods for utilizing medium and low-grade potassium phosphate ores, but also have important significance for the development of insoluble potassium in potassium feldspar.

[0003] The main components of potassium phosphate ore are collophanite and microcline potassium feldspar, and the other components are dolomite, quartz and a small amount of chlorite. The phosphorus and potassium content in potassium phosphate ore is low. At present, the main utilization idea is to enrich phosphorus or potassium through traditional mineral processing technology to obtain phosphorus concentrate or potassium concentrate. For example, "Flotation Experimental Study on Low-Grade Potassium Phosphate Ore in Yichang" (Li Xiang, Lv Renliang, Ma Jiayu, Wang Tielin, Luo Huihua, Wang Cunwen. Flotation Experimental Study on Low-Grade Potassium Phosphate Ore in Yichang [J]. Chemical Minerals and Processing, 2015, 44(05):1-4) discloses a small-scale experiment of roughing and scavenging Yichang potassium phosphate ore using TSM-46 and dodecylamine as collectors, sodium carbonate and sulfuric acid as pH adjusters, and water glass as an inhibitor and dispersant. The potassium-rich tailings were floated and suitable roughing process parameters were obtained. This document only uses potassium in potassium phosphate ore, but does not consider the use of phosphorus, resulting in a waste of resources. Moreover, the flotation method has a low recovery rate of phosphorus and potassium elements.

[0004] It can be seen that the use of traditional mineral processing technology and only the single use of a certain element will reduce the overall economic value of phosphate and potassium mines and cause a waste of resources.

[0005] At present, the traditional wet phosphoric acid process uses sulfuric acid to leach phosphate ore, which cannot effectively utilize potassium phosphate ore. The main reasons are: 1. When treating phosphate ore with sulfuric acid, 1 ton of ore will produce 1.4 to 1.5 tons of phosphogypsum, which is not environmentally friendly. 2. In large-scale production, phosphate fertilizer plants use vacuum filtration to separate phosphogypsum and acid. After acidifying potassium phosphate ore with sulfuric acid, not only a large amount of phosphogypsum will be produced, but also potassium fluorosilicate. Vacuum filtration will lower the system temperature, precipitate potassium fluorosilicate, and block the filter cloth, making separation difficult. 3. Even if it is barely filtered, the entrained potassium fluorosilicate will act as a seed, making it easier for calcium sulfate and sodium fluorosilicate to precipitate in the fluid, blocking pipes and equipment. Therefore, the traditional wet phosphoric acid method cannot utilize potassium phosphate ore economically and environmentally friendly. It is necessary to find a new method to treat potassium phosphate ore.

[0006] The Chinese patent with publication number CN112758937A discloses a method for preparing potassium fluorosilicate and NPK compound fertilizer from phosphorus and potassium associated ore, wherein the phosphorus and potassium associated ore after roasting and activation is mixed with hydrochloric acid for leaching to obtain a filtrate enriched with phosphorus and potassium. The Chinese patent with publication number CN106278391A discloses a method for directly using hydrochloric acid to decompose phosphorus and potassium associated ore and phosphate ore mixed ore under low temperature conditions, wherein the phosphorus and potassium associated ore and the phosphate ore are ground and mixed evenly, and then hydrochloric acid solution is added for leaching to obtain a leaching solution containing K and P and an alkaline earth metal compound of fluorine. The Chinese patent with publication number CN105367176A discloses a multi-element comprehensive utilization process of phosphorus and potassium associated ore, wherein a fluorine-containing compound is used as an additive and a low-temperature leaching reaction of phosphorus and potassium associated ore is realized under acidic conditions to obtain a silica filter residue and a leachate. The Chinese patent with publication number CN102864303A discloses a method for leaching potassium from phosphorus and potassium associated ore using microwave / ultrasound-assisted low-temperature leaching. A Chinese patent with publication number CN104744175A discloses a method for producing nitrogen-phosphorus-potassium compound fertilizer using phosphorus-potassium associated minerals. The phosphorus-potassium associated minerals are used as raw materials, mixed with sulfuric acid and fluoride additives for reaction, filtered, and the pH of the obtained filtrate is adjusted to 6.5-8.0 with ammonia water, and then evaporated, crystallized, and granulated to obtain a high-concentration nitrogen-phosphorus-potassium compound fertilizer.

[0007] It can be seen that in the prior art, the comprehensive utilization of phosphate and potassium ores is carried out by using hydrochloric acid or sulfuric acid, using ultrasound or adding various additives to simultaneously leach phosphorus and potassium to obtain a leachate containing phosphorus and potassium, and then comprehensively utilizing the leachate without separating phosphorus and potassium. The subsequent products are single and there are large differences between batches of products.

[0008] In addition, in the traditional wet phosphoric acid process, after using sulfuric acid to treat potassium phosphate ore, a large amount of gypsum will be produced, so vacuum filtration is used in the separation process. During the vacuum filtration process, the air will be taken away when it is extracted, reducing the temperature. Therefore, potassium fluorosilicate (K2SiF6, freezing point: -1°C) will precipitate due to the cooling during the filtration process, blocking the filter cloth. Even if it is barely filtered, the entrained potassium fluorosilicate will serve as a seed crystal, making it easier for calcium sulfate and sodium fluorosilicate to precipitate in the fluid, blocking the pipeline and equipment, and thus making the production process impossible. Therefore, it is difficult to use potassium phosphate ore in the traditional sulfuric acid method. Summary of the invention

[0009] In view of the above defects, the technical problem solved by the present invention is to provide a method for decomposing and utilizing phosphate potassium ore.

[0010] The decomposition and utilization method of potassium phosphate ore of the present invention comprises the following steps: mixing nitric acid and potassium phosphate ore, carrying out acid hydrolysis reaction, and after the reaction is completed, separating solid and liquid to obtain phosphorus-containing filtrate and potassium-containing acid insoluble matter; wherein the leaching rate of potassium in the potassium phosphate ore is ≤3%, and the leaching rate of phosphorus is ≥96%.

[0011] In one embodiment of the present invention, the particle size of the phospho-potassium ore is 50 - 200 μm.

[0012] In one embodiment of the present invention, the concentration of nitric acid is 35 - 65 wt%.

[0013] In one embodiment of the present invention, the amount of nitric acid used is more than 90% of the theoretical consumption. In a preferred embodiment of the present invention, the amount of nitric acid used is 90% - 110% of the theoretical consumption.

[0014] In one embodiment of the present invention, the temperature of the acidolysis reaction is ≥40°C. In a preferred embodiment of the present invention, the temperature of the acidolysis reaction is 40 - 70°C.

[0015] In one embodiment of the present invention, the acidolysis reaction adopts gradient acidolysis, and the gradient acidolysis sequentially includes the following steps:

[0016] A1: Divide the nitric acid solution into n parts, where n is an integer ≥2.

[0017] A2: React the phospho-potassium ore with 1 part of the nitric acid solution, then perform solid-liquid separation to obtain a solid and a liquid.

[0018] A3: React the solid obtained in the previous step with another 1 part of the nitric acid solution, then perform solid-liquid separation to obtain a solid and a liquid.

[0019] Repeat step A3 until the reaction of n parts of the nitric acid solution is completed. The obtained solid is potassium-containing acid-insoluble matter, and the liquids from all steps are combined to be the phosphorus-containing filtrate.

[0020] In one embodiment of the present invention, the treatment method of the phospho-potassium ore further includes the following steps: Mix the phosphorus-containing filtrate with a lime milk solution for a mineralization reaction to make its pH value 2.5 - 4, and then filter to obtain phosphorus concentrate.

[0021] In one embodiment of the present invention, the temperature of the mineralization reaction is 40 - 80°C.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention first treats the phospho-potassium ore with nitric acid, controls the reaction conditions in the acidolysis process, reduces the leaching rate of potassium elements, realizes the separation of phosphorus and potassium elements, and avoids the problem of the filter cloth being blocked by potassium fluorosilicate precipitating during vacuum filtration and cooling. Therefore, the nitric acid method for treating phospho-potassium ore perfectly avoids the disadvantages of the traditional wet-process phosphoric acid for treating phospho-potassium ore, and the products are rich. Specific Embodiments

[0024] The method for decomposing and utilizing phosphate-potassium ore of the present invention comprises the following steps: mixing nitric acid and phosphate-potassium ore, carrying out acidolysis reaction, and after the reaction is completed, separating solid from liquid to obtain a phosphate-containing filtrate and potassium-containing acid-insoluble substances; wherein, the leaching rate of potassium in the phosphate-potassium ore is ≤3%, and the leaching rate of phosphorus is ≥96%.

[0025] The present invention uses nitric acid to treat phosphate-potassium ore, and by controlling the reaction conditions in the acidolysis process, the leaching rate of potassium element is reduced, realizing the separation of phosphorus and potassium elements. The nitric acid method does not produce gypsum, so the production equivalent in the separation process is not large. In the separation process, a centrifuge is generally used for separation and filtration, avoiding the problem of potassium fluorosilicate precipitating and blocking the filter cloth due to vacuum filtration and temperature reduction. Therefore, the nitric acid method for treating phosphate-potassium ore effectively overcomes the shortcomings of the traditional sulfuric acid method for treating phosphate-potassium ore, and the products are rich.

[0026] In one embodiment of the present invention, the particle size of the phosphate-potassium ore is 50-200 μm.

[0027] In one embodiment of the present invention, the concentration of nitric acid is 35-65 wt%.

[0028] It is found by single-factor experiments that the factor having the greatest influence on the leaching rates of phosphorus and potassium is the dosage of nitric acid, and the other factors such as reaction time, reaction temperature, mesh number, etc. have little influence on the leaching rates of phosphorus and potassium, but have a certain influence on impurity elements. In one embodiment of the present invention, the dosage of nitric acid is more than 90% of the theoretical consumption. In a preferred embodiment of the present invention, the dosage of nitric acid is 90%-110% of the theoretical consumption.

[0029] Unless otherwise specified, the percentage signs in the present invention all represent mass fractions.

[0030] The theoretical consumption described in the present invention is the theoretical acid consumption for the complete reaction of phosphate-potassium ore, which can be calculated according to the contents of various components in the phosphate-potassium ore. For example, if the main components reacting with acid in a certain phosphate-potassium ore are calcium oxide, magnesium oxide, iron oxide and aluminum oxide, the theoretical acid consumption for the complete reaction of calcium oxide, magnesium oxide, iron oxide and aluminum oxide in the phosphate-potassium ore can be calculated based on the contents of the above components, that is, the theoretical acid consumption for the complete reaction of phosphate-potassium ore.

[0031] In one embodiment of the present invention, the temperature of the acidolysis reaction is ≥40 °C. When the acidolysis reaction temperature is above 40 °C, a high phosphorus leaching rate and a low potassium leaching rate can be ensured. The reaction temperature can be any temperature above 40 °C, such as 50 °C, 70 °C, etc. It can also be pressurized to further increase the reaction temperature to 100 °C, 200 °C, etc.

[0032] In a preferred embodiment of the present invention, in order to simplify the operation and save energy, the temperature of the acidolysis reaction is 40-70 °C.

[0033] In one embodiment of the present invention, the acidolysis reaction adopts gradient acidolysis, and the gradient acidolysis sequentially includes the following steps:

[0034] A1: Divide the nitric acid solution into n parts, where n is an integer ≥ 2;

[0035] A2: React the potassium phosphate ore with 1 part of the nitric acid solution, then perform solid-liquid separation to obtain a solid and a liquid;

[0036] A3: React the solid obtained in the previous step with another 1 part of the nitric acid solution, then perform solid-liquid separation to obtain a solid and a liquid;

[0037] Repeat step A3 until the reaction of n parts of the nitric acid solution is completed. The obtained solid is potassium-containing acid-insoluble matter, and the liquids from all steps are combined to obtain a phosphorus-containing filtrate.

[0038] During the acidolysis process, the concentration of H + is crucial for the decomposition of each mineral phase. Therefore, by controlling the concentration of acid in the reaction tank through gradient acidolysis, it is possible to preferentially decompose fluorapatite without decomposing potassium feldspar, increasing the separation degree of phosphorus and potassium elements.

[0039] In one embodiment of the present invention, n is 3. Dividing the nitric acid solution into 3 parts by volume for gradient acidolysis can increase the separation ratio of phosphorus and potassium.

[0040] In a specific embodiment, the nitric acid solution is divided into three parts in a volume ratio of 5:3:2. Specifically, the acid solution is divided into three parts in a ratio of 5:3:2 and placed in three acidolysis tanks, numbered 1, 2, and 3 in sequence. Add the potassium phosphate ore to the first acidolysis tank, react after feeding, and then perform solid-liquid separation. Collect the solid and add it to the second acidolysis tank, react, and then perform solid-liquid separation. Collect the solid and add it to the third acidolysis tank, react, and the obtained solid is potassium-containing acid-insoluble matter. The liquids from the three acidolysis solid-liquid separations are combined to obtain a phosphorus-containing filtrate.

[0041] In one embodiment of the present invention, the treatment method of the potassium phosphate ore further includes the following steps: Mix the phosphorus-containing filtrate with a lime milk solution for a mineralization reaction to make its pH value 2.1 - 2.4, and then filter to obtain phosphorus concentrate.

[0042] In the mineralization process, the decomposition of potassium fluorosilicate can be achieved by adjusting the pH, thus avoiding the problem of scaling in equipment and pipelines.

[0043] The main components in the phosphate-potassium ore are Ca5F(PO4)3, K2O·Al2O3·6SiO2, CaCO3, MgCO3, SiO2, etc. The lower the grade of the phosphate ore, the higher the impurity content and the lower the P2O5 content. By decomposing the phosphate-potassium ore with nitric acid, the phosphorus in the ore is activated and exists in the solution, and then it is calcified into calcium phosphate and precipitated as concentrate, while a small amount of potassium is dissolved in the nitric acid decomposition system and does not enter the concentrate. The main reactions occurring during the reaction process are as follows:

[0044]

[0045] The filter residue after mineralization is phosphate concentrate, and the subsequent utilization of the filtrate after mineralization can be divided into two types: If the manufacturer can produce nitric acid by itself, the mineralized filtrate can be prepared into calcium nitrate tetrahydrate; if the manufacturer cannot produce nitric acid, the manufacturer can add sulfuric acid to remove calcium, and then rectify and separate nitric acid for recycling use.

[0046] In one embodiment of the present invention, the concentration of the lime milk solution is 60-70%, and the concentration of the lime milk is calculated based on calcium oxide.

[0047] In one embodiment of the present invention, the temperature of the mineralization reaction is 40-50°C.

[0048] In one embodiment of the present invention, in order to make the mineralization reagent parameters (such as viscosity, density, etc.) close to the actual production system, the lime milk solution can be prepared with calcium nitrate solution as the base liquid, that is, calcium nitrate is also added to the lime milk solution, and preferably the concentration of calcium nitrate is 30-50%.

[0049] Since most of the potassium elements in the phosphate-potassium ore exist in the form of potassium feldspar, the phosphate-potassium ore cannot be efficiently, economically and environmentally friendly utilized by using the flotation method or sulfuric acid acidolysis treatment. The present invention decomposes the phosphate-potassium ore with nitric acid to obtain phosphate concentrate and potassium-rich acid-insoluble substances, and both of them are widely used in the chemical industry, greatly increasing the economic value of the phosphate-potassium ore and finding a new way out for the phosphate-potassium ore that has not been widely utilized at present.

[0050] The following further describes the specific embodiments of the present invention in conjunction with the examples, and the present invention is not limited to the scope of the described examples. The phosphate-potassium ore used in the examples is provided by Hanyuan, and its components are shown in Table 1.

[0051] Table 1 Phosphate-potassium ore component analysis

[0052]

[0053] The component measurement method is XRF sample measurement.

[0054] Example 1

[0055] (1) According to the composition of the phosphate-potassium ore, the theoretical consumption of pure nitric acid is 899.1 g / kg of phosphate-potassium ore. The amount of nitric acid added is 90% of the theoretical amount. Inject nitric acid (concentration: 65%) into the acid tank and mix it with water to prepare an acidolysis solution with a concentration of 40%.

[0056] (2) Weigh a certain mass of ore powder (the mass fraction of ore powder with a mesh size of 50 - 100 is 0.4, and the mass fraction of ore powder with a mesh size of 100 - 200 is 0.6).

[0057] (3) Start the stirring paddle of the reaction tank. After the temperature of the reaction tank reaches the predetermined temperature of 50 °C, add the ore powder, and control the feeding time within 50 min. After the feeding is completed, react for another 20 min, and then carry out vacuum filtration. Wash, weigh, and measure the composition of the filter cake after drying, as shown in Table 2. Calculate the leaching rates of phosphorus and potassium and the separation effect of phosphorus and potassium, and the results are shown in Table 3.

[0058] Table 2 Analysis of the composition of acid-insoluble substances in Example 1

[0059]

[0060] Table 3 Leaching rates of phosphorus and potassium in examples and comparative examples

[0061] Examples 2 - 4 and Comparative Examples 1 - 3

[0062] Using the method of Example 1, only changing some conditions, carry out acidolysis reaction. The specific variable conditions are shown in Table 4. Measure the composition of the filter cake and calculate the leaching rates of phosphorus and potassium and the separation effect of phosphorus and potassium, and the results are shown in Table 3.

[0063] Table 4 Variables in examples and comparative examples

[0064] Comparative Example 4

[0065] In the acidolysis process, use sulfuric acid, keep the other conditions unchanged, and explore whether the traditional wet-process phosphoric acid process can utilize phosphate-potassium ore.

[0066] (1) According to the composition of the phosphate-potassium ore, the theoretical consumption of pure sulfuric acid is 663.1 g / kg of phosphate-potassium ore. The amount of sulfuric acid added is 90% of the theoretical amount. Inject sulfuric acid (concentration: 98%) into the acid tank and mix it with water to prepare an acidolysis solution with a concentration of 40%.

[0067] (2) Weigh a certain mass of ore powder (the mass fraction of ore powder with a mesh size of 50 - 100 is 0.4, and the mass fraction of ore powder with a mesh size of 100 - 200 is 0.6).

[0068] (3) Start the stirring paddle of the reaction tank. After the temperature of the reaction tank reaches the predetermined temperature (50 °C), add the ore powder, and control the feeding time within 50 min. After the feeding is completed, react for another 20 min, and then perform pressure filtration. Wash, weigh, and dry, and then measure the composition of the filter cake. See Table 5 for details. Calculate the leaching rates of phosphorus and potassium and the separation effect of phosphorus and potassium. The results are shown in Table 3.

[0069] Table 5 Analysis of the composition of acid-insoluble substances in Comparative Example 4

[0070] It was found that due to the production of calcium sulfate by sulfuric acid acidolysis, the reaction was passivated, and the phosphorus leaching rate and the separation effect of phosphorus and potassium were much lower than those in the examples. Therefore, the traditional sulfuric acid acidolysis process is inferior to the nitric acid acidolysis process under the same conditions.

[0071] Comparative Example 5

[0072] In the acidolysis process, sulfuric acid was used. Referring to the actual process production conditions, in step (3), vacuum filtration was used, and the other conditions were controlled unchanged to observe whether potassium fluorosilicate would block the filter paper.

[0073] Finally, it was found that under laboratory conditions, vacuum filtration could be used for filtration, but the filtration speed was significantly slower than that of pressure filtration.

[0074] Comparative Example 6

[0075] In the acidolysis process, hydrochloric acid was used, and the other conditions were controlled unchanged to explore whether the hydrochloric acid method could utilize phosphate rock and potassium ore.

[0076] (1) According to the composition of phosphate rock and potassium ore, the theoretical consumption of pure hydrochloric acid is 520.8 g / kg of phosphate rock and potassium ore. Hydrochloric acid (the added amount is 90% of the theoretical amount), and hydrochloric acid (concentration: 35%) was injected into the acid tank and mixed with water to prepare an acidolysis solution with a concentration of 40%.

[0077] Weigh a certain mass of ore powder (the mass fraction of ore powder with a mesh size of 50 - 100 meshes is 0.4, and the mass fraction of ore powder with a mesh size of 100 - 200 meshes is 0.6).

[0078] (3) Start the stirring paddle of the reaction tank. After the temperature of the reaction tank reaches the predetermined temperature (50 °C), add the ore powder, and control the feeding time within 50 min. After the feeding is completed, react for another 20 min, and then perform vacuum filtration. Wash, weigh, and dry, and then measure the composition of the filter cake. See Table 6 for details. Calculate the leaching rates of phosphorus and potassium and the separation effect of phosphorus and potassium. The results are shown in Table 3.

[0079] Table 6 Analysis of the composition of acid-insoluble substances in Comparative Example 6

[0080] It was found that the leaching rate of phosphorus from phosphate-potassium ore decomposed by hydrochloric acid and the separation effect of phosphorus and potassium were much lower than those in Example 1. Therefore, the traditional hydrochloric acid and sulfuric acid acidolysis processes are not as effective as the nitric acid acidolysis process under the same conditions.

[0081] Example 5

[0082] Through gradient acidolysis, control the H + concentration in the reaction tank to improve the separation effect of phosphorus and potassium.

[0083] (1) According to the composition of the phosphate-potassium ore, the theoretical consumption of pure nitric acid is 899.1 g / kg of phosphate-potassium ore. The amount of nitric acid added is 90% of the theoretical amount. Inject nitric acid (concentration: 65%) into the acid tank and mix it with water to prepare an acidolysis solution with a concentration of 40%. Then divide the acid solution into three parts in a ratio of 5:3:2 and place them in three acidolysis tanks, numbered 1, 2, and 3 in sequence.

[0084] (2) Weigh a certain mass of ore powder (the mass fraction of ore powder with a mesh size of 50 - 100 meshes is 0.4, and the mass fraction of ore powder with a mesh size of 100 - 200 meshes is 0.6).

[0085] (3) Start the stirring paddle of the reaction tank. After the temperature of the reaction tank reaches the predetermined temperature (50 °C), add the ore powder to Acidolysis Tank No. 1, and the feeding frequency is based on the standard that no large amount of bubbles are generated. After adding the material, react for another 30 minutes and then perform vacuum filtration. Collect the filter cake and add it to Acidolysis Tank No. 2, react for 18 minutes, and perform vacuum filtration. Collect the filter cake and add it to Acidolysis Tank No. 3, and react for 12 minutes. Wash, weigh, and measure the composition of the filter cake after drying. See Table 7 for details. Calculate the leaching rates of phosphorus and potassium and the separation effect of phosphorus and potassium. The results are shown in Table 3.

[0086] Table 7 Analysis of the composition of acid-insoluble substances in Example 5

[0087] It was found through experiments that gradient acidolysis can indeed increase the leaching rate of phosphorus, but at the same time, it will also increase the leaching rate of potassium, resulting in basically unchanged separation effect of phosphorus and potassium. However, from the perspective of recovering phosphorus elements, this process is superior to the example.

[0088] Example 6

[0089] The filtrate and washing solution in the acidolysis stage of Example 1 were combined into an acidolysis mixed solution for mineralization experiments. The specific steps are as follows:

[0090] (1) Mix lime milk with a certain amount of calcium nitrate solution (calcium nitrate is 40 wt%) to prepare a solution with a lime milk concentration of 60 - 70%.

[0091] (2) Combine the filtrate and washing solution in the acidolysis stage into an acidolysis mixed solution, weigh it, place it in a high-position tank, and prepare a peristaltic pump.

[0092] (3) Add the base material into the reaction tank (~5L). Both the reaction tank and the added base material need to be weighed and recorded. The added base material should preferably submerge the lower stirring paddle, and keep the material at a constant temperature of 45°C. Composition of the base material: The calcium nitrate content is approximately 38.0%.

[0093] (4) Start the stirring paddle of the reaction tank. After the temperature of the reaction tank reaches the predetermined temperature, add the acidolysis mixture and lime milk simultaneously. When the pH reaches 2.5 - 4, take a sample of about 200g of the slurry, filter it, wash the filter cake to obtain phosphoric acid concentrate. Determine the content of each element in the phosphoric acid concentrate, and the results are shown in Table 8.

[0094] Table 8 Composition Table of Phosphoric Acid Concentrate in Example 6

[0095] It can be seen that by using the method of the present invention, it is possible to treat potassium phosphate ore with nitric acid, reduce the leaching rate of potassium element by regulating the reaction conditions of the acidolysis process, realize the separation of phosphorus and potassium elements, perfectly avoid the disadvantages of traditional wet-process phosphoric acid for treating potassium phosphate ore, and have rich products.

Claims

1. A method for decomposing and utilizing phosphate rock and potassium ore, characterized in that, It includes the following steps: Mix a nitric acid solution and potassium phosphate rock, carry out an acidolysis reaction. After the reaction is completed, carry out solid-liquid separation to obtain a phosphorus-containing filtrate and potassium-containing acid-insoluble substances; wherein, the leaching rate of potassium in the potassium phosphate rock is ≤3%, and the leaching rate of phosphorus is ≥96%; the particle size of the potassium phosphate rock is 50-200 μm; in the nitric acid solution, the concentration of nitric acid is 35-65 wt%; the amount of nitric acid used is more than 90% of the theoretical consumption; the temperature of the acidolysis reaction is ≥40 °C.

2. The method for decomposing and utilizing phosphorite-potash ore according to claim 1, characterized in that: The amount of nitric acid used is 90%-110% of the theoretical consumption.

3. The method for decomposing and utilizing phosphorite-potash ore according to claim 1, wherein: The temperature of the acidolysis reaction is 40-70 °C.

4. The method for decomposing and utilizing phosphorite-potash ore according to claim 1, characterized in that: The acidolysis reaction adopts gradient acidolysis, and the gradient acidolysis sequentially includes the following steps: A1: Divide the nitric acid solution into n parts, where n is an integer ≥2; A2: React the potassium phosphate rock with 1 part of the nitric acid solution, and then carry out solid-liquid separation to obtain a solid and a liquid; A3: React the solid obtained in the previous step with another 1 part of the nitric acid solution, and then carry out solid-liquid separation to obtain a solid and a liquid; Repeat step A3 until the reaction of n parts of the nitric acid solution is completed. The obtained solid is potassium-containing acid-insoluble substances, and the liquids of all steps are combined to be the phosphorus-containing filtrate.

5. The method for decomposing and utilizing phosphate-potassium ore according to claim 1, characterized in that: It also includes the following steps: Mix the phosphorus-containing filtrate with a lime milk solution to carry out a mineralization reaction to make its pH value 2.5-4, and filter to obtain phosphorus concentrate.

6. The method for decomposing and utilizing phosphorite-potash ore according to claim 5, characterized in that: The temperature of the mineralization reaction is 40-80 °C.

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