Method for preparing iron phosphate from phosphorus and potassium ores and comprehensively utilizing resources

Abstract

The invention provides a method for preparing iron phosphate from phosphorus and potassium ores and comprehensively utilizing resources, and belongs to the crossing field of hydrometallurgy and chemical engineering, the method comprises the following steps: S1, slowly adding a hydrochloric acid solution into the phosphorus and potassium ores and iron powder, carrying out solid-liquid separation after the reaction is ended to obtain a leaching solution and acid leaching tailings, and using the acid leaching tailings for preparing a potassium fertilizer; s2, hydrogen peroxide is added into the leachate in the step S1 to oxidize Fe < 2 + >, then ammonium carbonate is added, the pH of the solution is adjusted to 1.5-2.0, crude iron phosphate dihydrate and primary precipitation mother liquor are obtained, the crude iron phosphate dihydrate is washed, dried and calcined, and battery-grade iron phosphate is obtained; s3, ammonium carbonate continues to be added into the primary precipitation mother liquor in the S2, the pH is adjusted to 7.0-7.5, crude CaCO3 and secondary precipitation mother liquor are obtained, and the crude CaCO3 is washed and dried to obtain a calcium carbonate product; and S4, sequentially carrying out evaporation concentration and cooling crystallization on the secondary precipitation mother liquor in S3 to obtain an ammonium chloride product. According to the method, all elements in the phosphorus-potassium ore are comprehensively utilized, and the method has important practical significance for developing and using phosphorus-potassium ore resources.

Description

Technical Field

[0001] The present invention belongs to the intersection field of hydrometallurgy and chemical industry, and specifically relates to a method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources. Background Art

[0002] my country has abundant reserves of phosphate resources, but the reserves of high-grade phosphate are low, and medium- and low-grade phosphate ore occupies the majority. The reserves of rich phosphate ore with a P2O5 content of 30% or more are only 1.66 billion tons. If the current mining mode of "mining the rich and abandoning the poor" is still followed, my country's phosphate ore will be mined out in 20 years, so the development and utilization of low-grade phosphate ore is imminent. There are more than 2 billion tons of phosphate-potassium composite ore in Hanyuan, Sichuan, which generally contains 10%~20% P2O5 and 29.1%~31.2% CaO. Because of its low grade and high impurity content in the ore, there is currently no mature Hanyuan phosphate-potassium ore utilization process. For this reason, the phosphate-potassium ore has been regarded as a "dead ore" for many years and has not been mined and utilized.

[0003] Iron phosphate is an important precursor for preparing lithium iron phosphate positive electrode materials. Its structure, purity and activity have a great influence on the electrical properties of lithium iron phosphate. At present, iron phosphate accounts for nearly 40% of the raw material cost of lithium iron phosphate. For lithium iron phosphate, which has a shrinking profit margin, it is necessary to improve the iron phosphate precursor process, which accounts for a large proportion of the preparation cost, so as to obtain a cheaper iron phosphate precursor. From the perspective of production cost, phosphorus source is the main cost source for the preparation of iron phosphate. Therefore, using a cheaper phosphorus source to reduce production costs has become a current research hotspot.

[0004] CN116374978A discloses a method for preparing iron phosphate, which includes the following steps: 1. Mixing ferrous nitrate solution with dilute nitric acid, reacting at a temperature of 50-80°C for 0.5-1.5h to obtain iron nitrate solution, then concentrating and crystallizing to obtain iron nitrate crystals; 2. Mixing iron nitrate crystals with concentrated phosphoric acid (concentration ≥ 85wt%), reacting at a temperature of 120-200°C for more than 30min to obtain iron phosphate. First, the method uses nitric acid for oxidation in the ferrous iron oxidation process, and a large amount of nitrogen oxides will be released during the production process; secondly, the process flow is complicated, which reduces the controllability during the preparation process and the product quality is unstable; finally, the method uses concentrated phosphoric acid with a relatively high cost as a phosphorus source, resulting in a high production cost and loss of industry competitiveness; finally, the by-product of the method is phosphogypsum with low practical value and difficult to handle, which increases the cost and difficulty of subsequent treatment and is not in line with the national green development. In summary, the method is difficult to industrialize.

[0005] CN115092901B discloses a method for producing battery-grade iron phosphate, which comprises: decomposing phosphate ore with hydrochloric acid; neutralizing and precipitating with ammonia; crystallizing ammonium phosphate; heating and decomposing iron salt to produce iron oxide; and melting and calcining iron oxide and ammonium phosphate to produce iron phosphate. First, the process is relatively complicated, resulting in a high P loss rate, which makes the yield of iron phosphate low; second, the process conditions of the method are relatively harsh, and most reactions are carried out under high temperature and high pressure, which increases the requirements for equipment and cannot be industrialized; finally, the by-products ammonium nitrate (used to produce explosives) and sodium fluorosilicate generated by the method are both hazardous chemicals, resulting in reduced safety and low product added value. Summary of the invention

[0006] The technical problem to be solved by the present invention is: in view of the shortcomings of the existing process for preparing battery-grade iron phosphate, such as high cost, poor safety and unstable product quality, the present invention adopts Hanyuan potassium phosphate ore with a lower price as a phosphorus source, innovatively introduces ammonium carbonate, obtains battery-grade iron phosphate by reaction precipitation, and obtains calcium carbonate and ammonium chloride products at the same time, which significantly reduces the production cost, and all elements are effectively utilized, and the products produced have high added value and wide application; therefore, the method has the advantages of high product purity, easy availability of raw materials, low energy consumption, small equipment corrosiveness and circulation load, green and environmentally friendly production process, high product added value, and suitability for large-scale production.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources, comprising the following steps:

[0009] S1. Slowly add hydrochloric acid solution to the potassium phosphate ore and iron powder, and after the reaction, separate the solid and liquid to obtain the leachate and acid leaching tailings, which are used to make potash fertilizer;

[0010] S2, add hydrogen peroxide to the S1 leaching solution to Fe 2+ The crude ferric phosphate dihydrate is oxidized, and then ammonium carbonate is added to adjust the pH value of the solution to 1.5-2.0 to obtain crude ferric phosphate dihydrate and a primary precipitation mother liquor. The crude ferric phosphate dihydrate is washed, dried and calcined to obtain battery-grade ferric phosphate;

[0011] S3, continue to add ammonium carbonate to the primary precipitation mother liquor in S2, adjust the pH to 7.0-7.5, obtain crude CaCO3 and secondary precipitation mother liquor, and obtain the calcium carbonate product after washing and drying the crude calcium carbonate;

[0012] S4, the secondary precipitation mother liquor in S3 is concentrated by evaporation and crystallized by cooling to obtain the ammonium chloride product.

[0013] Preferably, in step S1, the liquid-solid mass ratio is 1.5-3:1, wherein the liquid is hydrochloric acid, and the solid is potassium phosphate and iron powder. The mass concentration of the hydrochloric acid solution is 15-30%, the reaction temperature is 25-40°C, and the reaction time is 30-60 min.

[0014] Preferably, in step S1, "slow addition" means dropwise addition. Slow addition of hydrochloric acid solution can make the acid leaching reaction more gentle and sufficient; if it is added quickly, it will cause a violent reaction and severe foaming, which will cause boiling during production. It is not recommended to use other acids for acid leaching. For example, phosphoric acid is a medium-strong acid, and the acid leaching effect is poor; the byproduct of nitric acid is ammonium nitrate, which is easy to explode and has poor safety performance.

[0015] Preferably, in step S1, the main elements and their mass contents in the phosphate-potash ore are: P2O5: 20-22%, CaO: 30-32%, Fe2O3: 2.5-4%, wherein Ca mainly exists in the form of calcium oxide.

[0016] Preferably, in step S1, the amount of iron powder added is 1.0 to 1.05 times the theoretical molar amount of P in the leachate for complete precipitation. Since the iron content in the potassium phosphate ore is not high, iron powder needs to be added to completely react the phosphorus in the potassium phosphate ore to form iron phosphate. Whether the amount of iron powder added is appropriate can be determined by calculating the precipitation rate of P in the primary precipitation mother liquor.

[0017] Preferably, in step S2, the amount of hydrogen peroxide added is such that Fe 2+ 1.00~1.05 times of the theoretical molar amount of complete oxidation. The main components of the mother liquor of the first precipitation are: P: 0.11~0.15g / L, Ca: 65~70g / L, Fe: 0.5~1.0g / L, NH4 + :5~12g / L, Cl - :50~65g / L.

[0018] Preferably, in step S2, the optimal pH for complete precipitation of iron phosphate is 1.5-2. If the pH is low, the precipitation of iron phosphate is incomplete; if the pH is high, the impurity content in the iron phosphate is high. The main reaction equation is: 2Fe 2+ +H2O2+2H + →2Fe 3+ +2H2O、Fe 3+ +PO4 3- →FePO4↓.

[0019] Preferably, in step S2, the reaction temperature is 80-95° C., the reaction time is 0.5-2 h, the stirring rate is 200-500 r / min, and the aging time is 0.5-2.0 h.

[0020] Preferably, in step S3, the reaction temperature is 25-40°C, the reaction time is 1.5-2.0h, and the stirring rate is 100-300r / min. The main components of the secondary precipitation mother liquor are: P: 0.08-0.10g / L, Ca: 0.14-0.22g / L, Fe: 0.5-1.0g / L, NH4 + :45~55g / L, Cl - :50~60g / L.

[0021] Preferably, in step S3, the optimal pH for complete precipitation of calcium carbonate is 7.0-7.5. If the pH is low, the precipitation of calcium carbonate is incomplete; if the pH is high, there is an excess of ammonium ions in the solution, which increases the difficulty of later processing. The main reaction equation is: (NH4)2CO3+CaCl2→CaCO3↓+2NH4Cl.

[0022] If other monovalent carbonates (such as sodium carbonate and potassium carbonate) are used in this step, the product added value of NaCl, a byproduct of sodium carbonate, is too low and the economic benefit is not high, while the cost of potassium carbonate is too high. Therefore, the present invention uses ammonium carbonate as a precipitant, firstly, it will not introduce other impurity metal elements, and secondly, the produced ammonium chloride can be used as a compound fertilizer, and the product added value is high.

[0023] Preferably, in step S4, the secondary precipitation mother liquor is evaporated and concentrated to NH4 + The concentration is 65~80g / L, and the product is obtained by natural cooling and crystallization for 1.5~2h.

[0024] The beneficial effects of the present invention are as follows:

[0025] 1) In order to reduce production costs, the present invention abandons the use of relatively expensive phosphoric acid and phosphoric acid derivatives in the traditional preparation of battery-grade iron phosphate, and selects the cheaper Hanyuan potassium phosphate ore as the phosphorus source, which greatly reduces the cost of preparing iron phosphate and increases the industry competitiveness of the process.

[0026] 2) The technology provided by the present invention only requires "leaching" and "precipitation" steps from raw ore to product, shortening the preparation process and significantly increasing the yield of iron phosphate, thereby improving production efficiency and process efficiency.

[0027] 3) This process reduces the generation of waste and by-products, improves the utilization efficiency of raw materials, reduces resource waste, reduces energy consumption, and especially reduces the reaction steps under high temperature or high pressure conditions. The production process is green and environmentally friendly, reduces the impact on the environment, and the obtained product has a higher purity.

[0028] 4) This process realizes the effective utilization of elements such as phosphorus, calcium, potassium and iron in phosphate-potassium ore, and the products produced have high added value and good economic benefits.

[0029] 5) The decomposition of phosphate rock with hydrochloric acid greatly reduces the generation of gypsum solid waste, reduces environmental pollution and potential safety risks. This project makes full use of by-products, and a variety of materials in the process can be recycled, which is in line with the concept of green industry and green technology actively supported by the country.

[0030] 6) This process has a wide range of applications and can be applied to most medium and low-grade phosphate ores, solving the problem of low utilization rate of medium and low-grade phosphate ores. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 The present invention is a process flow chart of a method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0034] The analysis results of the components of the Hanyuan potassium phosphate ore raw material used in the following examples are shown in Table 1.

[0035] Table 1 Analysis results of components of Hanyuan phosphate and potash ore

[0036]

[0037] Example 1

[0038] S1. Slowly add hydrochloric acid solution to phosphate potassium ore and iron powder (the amount of iron powder added is 1.0 times the theoretical molar amount of complete precipitation of P in the leaching solution), the liquid-to-solid mass ratio is 2.5:1, the mass fraction of hydrochloric acid is 30%, the reaction temperature is 25°C, the reaction time is 30 minutes, and the reaction is completed. The solid-liquid separation obtains the leaching solution and the acid leaching tailings. At this time, the leaching rate of P is 99.21%, and the acid leaching tailings are used to make potash fertilizer;

[0039] S2, add hydrogen peroxide to the S1 leaching solution (the amount of hydrogen peroxide added is to make the Fe 2+ 1.05 times the theoretical molar amount of complete oxidation) 2+Oxidation is performed, and then ammonium carbonate is added to adjust the pH of the solution to 1.5 to obtain crude ferric phosphate dihydrate and a primary precipitation mother liquor. The reaction conditions are: reaction temperature is 85° C., reaction time is 1.0 h, stirring rate is 200 r / min, aging time is 1.0 h, and crude ferric phosphate dihydrate is washed, dried and calcined to obtain battery-grade ferric phosphate;

[0040] S3. Continue to add ammonium carbonate to the primary precipitation mother liquor in S2, adjust the pH to 7.0, and obtain crude CaCO3 and secondary precipitation mother liquor. The reaction conditions are: reaction temperature is 25°C, reaction time is 1.5h, stirring rate is 100r / min, and the crude calcium carbonate is washed and dried to obtain the calcium carbonate product.

[0041] S4, evaporate and concentrate the secondary precipitation mother liquor in S3 to NH4 + The concentration is 70g / L, and the ammonium chloride product can be obtained by natural cooling and crystallization for 1.5h.

[0042] Example 2

[0043] A method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources is implemented according to the method described in Example 1, except that:

[0044] S2, add hydrogen peroxide to the S1 leaching solution (the amount of hydrogen peroxide added is to make the Fe 2+ 1.0 times the theoretical molar amount of complete oxidation) 2+ Oxidation is performed, and then ammonium carbonate is added to adjust the pH of the solution to 2.0 to obtain crude ferric phosphate dihydrate and a primary precipitation mother liquor. The reaction conditions are: reaction temperature is 90° C., reaction time is 1.5 h, stirring rate is 300 r / min, aging time is 1.0 h, and the crude ferric phosphate dihydrate is washed, dried and calcined to obtain battery-grade ferric phosphate;

[0045] S3. Continue to add ammonium carbonate to the primary precipitation mother liquor in S2, adjust the pH to 7.5, and obtain crude CaCO3 and secondary precipitation mother liquor. The reaction conditions are: reaction temperature is 25°C, reaction time is 2.0h, stirring rate is 200r / min, and the crude calcium carbonate is washed and dried to obtain the calcium carbonate product.

[0046] S4, evaporate and concentrate the secondary precipitation mother liquor in S3 to NH4 + The concentration is 75g / L, and the ammonium chloride product can be obtained by natural cooling and crystallization for 1.5h.

[0047] Example 3

[0048] A method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources is implemented according to the method described in Example 1, except that:

[0049] S2, add hydrogen peroxide to the S1 leaching solution (the amount of hydrogen peroxide added is to make the Fe 2+ 1.05 times the theoretical molar amount of complete oxidation) 2+ Oxidation is performed, and then ammonium carbonate is added to adjust the solution pH to 1.5 to obtain crude ferric phosphate dihydrate and a primary precipitation mother liquor. The reaction conditions are: reaction temperature is 95° C., reaction time is 2.0 h, stirring rate is 400 r / min, aging time is 1.0 h, and crude ferric phosphate dihydrate is washed, dried and calcined to obtain battery-grade ferric phosphate;

[0050] S3. Continue to add ammonium carbonate to the primary precipitation mother liquor in S2, adjust the pH to 7.0, and obtain crude CaCO3 and secondary precipitation mother liquor. The reaction conditions are: reaction temperature is 25°C, reaction time is 2.0h, stirring rate is 300r / min, and the crude calcium carbonate is washed and dried to obtain the calcium carbonate product.

[0051] S4, evaporate and concentrate the secondary precipitation mother liquor in S3 to NH4 + The concentration is 80g / L, and the ammonium chloride product can be obtained by natural cooling and crystallization for 1.5h.

[0052] Comparative Example 1

[0053] A method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources is implemented according to the method described in Example 1, except that:

[0054] S2, add hydrogen peroxide to the S1 leaching solution (the amount of hydrogen peroxide added is to make the Fe 2+ 1.05 times the theoretical molar amount of complete oxidation) 2+ Oxidation is carried out, and then ammonium carbonate is added to adjust the pH of the solution to 3.0 to obtain crude ferric phosphate dihydrate and a primary precipitation mother liquor. The reaction conditions are: reaction temperature is 85°C, reaction time is 1.0h, stirring rate is 200r / min, aging time is 1.0h, and the crude ferric phosphate dihydrate is washed, dried and calcined to obtain ferric phosphate.

[0055] Comparative Example 2

[0056] A method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources is implemented according to the method described in Example 1, except that:

[0057] S2, add hydrogen peroxide to the S1 leaching solution (the amount of hydrogen peroxide added is to make the Fe 2+ 1.05 times the theoretical molar amount of complete oxidation) 2+Oxidation is carried out, and then ammonium carbonate is added to adjust the pH of the solution to 1.5 to obtain crude ferric phosphate dihydrate and a primary precipitation mother liquor. The reaction conditions are: reaction temperature is 75°C, reaction time is 0.5h, stirring rate is 100r / min, aging time is 1.0h, and the crude ferric phosphate dihydrate is washed, dried and calcined to obtain ferric phosphate.

[0058] Comparative Example 3

[0059] A method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources is implemented according to the method described in Example 1, except that:

[0060] S3. Continue to add ammonium carbonate to the primary precipitation mother liquor in S2, adjust the pH to 6.5, and obtain crude CaCO3 and secondary precipitation mother liquor. The reaction conditions are: reaction temperature is 25°C, reaction time is 1.5h, stirring rate is 100r / min, and the crude calcium carbonate is washed and dried to obtain the calcium carbonate product.

[0061] Product parameter testing

[0062] The examples 1-3 of the present invention and the comparative examples 1-3 were tested, and the indicators of the products obtained by the present invention were compared with the industry standards. The results are shown in Table 2, Table 3 and Table 4.

[0063] Table 2 Composition of ferric phosphate products

[0064]

[0065] Table 3 Calcium carbonate product composition

[0066]

[0067] Table 4 Ammonium chloride product composition

[0068]

[0069] It can be seen from the data in Tables 2, 3 and 4 that the contents of each component in the products prepared in Examples 1-3 of the present invention are all within the range required by industry standards and are all qualified products.

[0070] In Comparative Example 1, the pH of the solution for precipitating ferric phosphate was too high, and the Ca content in the chemical index of the prepared ferric phosphate exceeded the standard. In Comparative Example 2, the reaction temperature for precipitating ferric phosphate was too low, the reaction time was too short, and the stirring rate was too low, resulting in the content of P and Fe in the ferric phosphate not meeting the standard, indicating that the precipitation of P and Fe in the reactants was incomplete. In Comparative Example 3, the pH of the solution for precipitating calcium carbonate was too low, and the main content of the prepared CaCO3 was not up to standard, indicating that the precipitation of calcium ions in the reactants was incomplete.

[0071] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources, characterized in that: The following steps are involved: S1. Slowly add hydrochloric acid solution to the potassium phosphate ore and iron powder, and after the reaction, separate the solid and liquid to obtain the leachate and acid leaching tailings, which are used to make potash fertilizer; S2, add hydrogen peroxide to the S1 leaching solution to Fe 2+ The crude ferric phosphate dihydrate is oxidized, and then ammonium carbonate is added to adjust the pH value of the solution to 1.5-2.0 to obtain crude ferric phosphate dihydrate and a primary precipitation mother liquor. The crude ferric phosphate dihydrate is washed, dried and calcined to obtain battery-grade ferric phosphate; S3, continue to add ammonium carbonate to the primary precipitation mother liquor in S2, adjust the pH to 7.0-7.5, obtain crude CaCO3 and secondary precipitation mother liquor, and obtain the calcium carbonate product after washing and drying the crude calcium carbonate; S4, the secondary precipitation mother liquor in S3 is concentrated by evaporation and crystallized by cooling to obtain the ammonium chloride product.

2. The method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources according to claim 1, characterized in that: In step S1, the liquid-solid mass ratio is 1.5-3:1, the mass concentration of the hydrochloric acid solution is 15-30%, the reaction temperature is 25-40°C, and the reaction time is 30-60min.

3. The method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources according to claim 1, characterized in that: In step S1, the main elements and their mass contents in the phosphate-potash ore are: P2O5: 20-22%, CaO: 30-32%, Fe2O3: 2.5-4%.

4. The method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources according to claim 1, characterized in that: In step S1, the amount of iron powder added is 1.0 to 1.05 times the theoretical molar amount for complete precipitation of P in the leaching solution.

5. The method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources according to claim 1, characterized in that: In step S2, the amount of hydrogen peroxide added is such that Fe 2+ 1.00~1.05 times the theoretical molar amount for complete oxidation.

6. The method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources according to claim 1, characterized in that: In step S2, the reaction temperature is 80-95° C., the reaction time is 0.5-2 h, the stirring rate is 200-500 r / min, and the aging time is 0.5-2.0 h.

7. The method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources according to claim 1, characterized in that: In step S3, the reaction temperature is 25-40° C., the reaction time is 1.5-2.0 h, and the stirring rate is 100-300 r / min.

8. The method for preparing iron phosphate from potassium phosphate ore and comprehensive utilization of resources according to claim 1, characterized in that: In step S4, the secondary precipitation mother liquor is evaporated and concentrated to NH4 + The concentration is 65~80g / L, and the product is obtained by natural cooling and crystallization for 1.5~2h.

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