Method for comprehensive utilization of potassium-rich acid-insoluble substance

Abstract

The present application relates to a comprehensive utilization method of potassium-rich acid-insoluble substance, and belongs to the technical field of potassium ore processing. The present application solves the technical problem of providing a comprehensive utilization method of potassium-rich acid-insoluble substance. The method comprises the following steps: a, acidolysis: potassium-rich acid-insoluble substance is mixed with nitric acid and fluorosilicic acid, and reacted at 50-110 DEG C for 1-6h, and then solid-liquid separation is performed to obtain a potassium-containing filtrate; b, neutralization: the potassium-containing filtrate is mixed with potassium hydroxide, and then solid-liquid separation is performed to obtain a potassium nitrate solution and an aluminum hydroxide precipitate; c, crystallization: the potassium nitrate solution is crystallized to obtain a potassium nitrate product. The method provides an economic and green utilization route for potassium-rich acid-insoluble substance, has a high potassium leaching rate, and fully utilizes potassium and aluminum elements, so that all elements of the potassium phosphate ore are utilized, and the economic value of the potassium phosphate ore is increased. Meanwhile, the method provides a new utilization idea for potassium feldspar resources with similar components in China, has a mature industrial utilization, and is simple and low in cost.

Description

Technical Field

[0001] This invention relates to a method for the comprehensive utilization of potassium-rich acid-insoluble substances, belonging to the field of potassium ore processing technology. Background Technology

[0002] my country's potash reserves are approximately 1.1 billion tons, mainly distributed in Qinghai, Yunnan, Sichuan, Shandong, and Xinjiang. The reserves of soluble potash are relatively small, while the demand for potash fertilizer in agriculture is substantial. Therefore, the development and utilization of insoluble potash resources are of great significance to my country's agricultural development.

[0003] Potassium feldspar is a naturally occurring mineral resource with a stable structure. It contains potassium, aluminum, silicon, and other components, and the proven reserves in my country are as high as tens of billions of tons. Potassium feldspar has been studied abroad for nearly a hundred years, and domestically it has been studied and developed for nearly sixty years, but no mature process has been formed. Currently, the methods for utilizing potassium feldspar are: (1) High-temperature decomposition, including sintering, melting, and blast furnace smelting. This method involves mixing potassium feldspar with additives or auxiliaries and reacting it at 900-1500℃ to convert insoluble potassium into soluble or citrate-soluble potassium. However, this technology has high energy consumption and poor economic efficiency. (2) Decomposition with fluorine-containing additives, which destroys the stable structure of potassium feldspar by generating hydrogen fluoride, thereby obtaining soluble potassium. This method has a low reaction temperature, but the fluorides generated are easy to corrode equipment, which greatly increases the investment cost and may also pollute the environment. (3) Microbial decomposition, which uses bacteria to react with potassium feldspar to decompose it. It has the advantages of short process flow and low pollution. However, it has disadvantages such as long strain cultivation cycle, slow decomposition rate and low potassium dissolution rate, so it is not suitable for industrial production.

[0004] Patent CN102001691A discloses a process for producing potassium nitrate by low-temperature decomposition of potassium feldspar using fluorinated acid. The process involves decomposing potassium feldspar powder with fluorinated acid at an acid-to-powder ratio of 1–5:1, reacting at 60–100°C for 1–6 hours, and absorbing the generated SiF4 gas with water to obtain H2SiF6 and silica products. The resulting slurry is separated to obtain liquid, paste, and solids. The liquid and solids are returned to the reactor for secondary decomposition and separation. After potassium feldspar decomposition, the final product is an acidic liquid, paste, and solids. The solids are purified and separated using fluorinated acid to obtain potassium fluorosilicate. The resulting acid solution is reused in the potassium feldspar decomposition reaction. After K2SiF6 and KOH undergo a complete alkaline hydrolysis reaction under heating conditions, KF solution and SiO2·nH2O are separated. Part of the KF solution reacts with Ca(OH)2 to separate KOH solution and CaF2 solid. Another part of the KF solution reacts with Ca(NO3)2 to obtain CaF2 and potassium nitrate products. The production process generates no waste, solving the technical problems of high energy consumption, low output, and low recovery rate found in existing technologies. However, this method uses a large amount of fluorinated acid, which easily corrodes equipment, increasing equipment investment. Furthermore, the high temperature easily causes the fluorinated acid to volatilize, polluting the environment. Its process flow is also relatively long, and each step involves fluorinated substances, further increasing equipment investment.

[0005] Patent CN1557781A discloses a low-temperature decomposition method for potassium feldspar. Potassium feldspar is mixed with sulfuric acid and the additive fluorosilicic acid, reacting at 90–150°C to generate silicon tetrafluoride gas and soluble salts. The silicon tetrafluoride gas undergoes four-stage absorption to obtain reusable fluorosilicic acid and silicic acid precipitate. The silicic acid precipitate is processed into silica, which can be used as a rubber reinforcing material. The soluble salts are neutralized with ammonia to generate a potassium ion-containing solution and an aluminum hydroxide precipitate. The potassium ion-containing solution can be concentrated to produce potassium ammonium sulfate compound fertilizer. The aluminum hydroxide precipitate, after acidification and alkalization, can be used to produce polyaluminum sulfate for water treatment flocculation. Therefore, this method features a simple and reasonable process, low energy consumption, low cost, high efficiency, high potassium feldspar decomposition rate (up to 99%), high comprehensive utilization rate, no waste discharge, and high additive recovery rate. However, this patent has a relatively high reaction temperature and high energy consumption.

[0006] It is evident that existing technologies for extracting potassium from potassium feldspar suffer from problems such as high energy consumption, poor economic efficiency, low utilization rate of potassium ore, and heavy pollution. Breakthroughs in this field could not only open up new avenues for potassium salt products but also significantly increase the economic value of potassium feldspar.

[0007] Furthermore, after acid leaching of potassium phosphate ore, the acid-insoluble residue mainly consists of potassium feldspar and a small amount of unreacted metallic minerals. Compared to traditional potassium feldspar, the composition of this acid-insoluble residue is more complex. If it is not utilized, it will not only hinder the economical and efficient use of potassium phosphate ore but also lead to a waste of resources. Existing potassium feldspar decomposition technologies are unable to effectively decompose this acid-insoluble residue. Summary of the Invention

[0008] To address the above deficiencies, the technical problem solved by this invention is to provide a comprehensive utilization method for potassium-rich acid-insoluble substances.

[0009] The method for comprehensive utilization of potassium-rich acid-insoluble substances of the present invention includes the following steps:

[0010] a. Acid hydrolysis: Potassium-rich acid insolubles are mixed with nitric acid and fluorosilicic acid and reacted at 50-110℃ for 1-6 hours. After the reaction is completed, solid and liquid are separated to obtain potassium-containing filtrate and acid residue.

[0011] b. Neutralization: Mix the potassium-containing filtrate with potassium hydroxide, adjust the pH to 5-8, and separate the solid and liquid to obtain potassium nitrate solution and aluminum hydroxide precipitate;

[0012] c. Crystallization: Potassium nitrate solution is crystallized to obtain potassium nitrate product;

[0013] The potassium-rich acid-insoluble matter is the insoluble matter after acid leaching of potassium phosphate ore.

[0014] In one embodiment of the present invention, in step a, the amount of nitric acid added is 110% to 170% of the theoretical amount, and the amount of fluorosilicic acid added is 30% to 100% of the theoretical amount.

[0015] In one embodiment of the present invention, in step a, the gas generated during the reaction is collected, absorbed, and separated into solid and liquid components. The resulting liquid is a fluorosilicic acid solution, and the resulting solid is washed and dried to obtain silica. The absorption temperature is >70°C.

[0016] In one embodiment of the present invention, the absorption is a two-stage absorption, wherein the primary absorption medium is a fluorosilicic acid solution with a concentration of 10-20 wt%, and the secondary absorption medium is a fluorosilicic acid solution with a concentration of <10 wt%.

[0017] In one embodiment of the present invention, in step b, ammonia or liquid ammonia is used to replace potassium hydroxide, and solid-liquid separation is performed to obtain ammonium nitrate solution and aluminum hydroxide precipitate. Then, the ammonium nitrate solution is reacted with potassium chloride to obtain potassium nitrate solution.

[0018] In one embodiment of the present invention, the potassium-rich acid insoluble matter is prepared by the following method: a nitric acid solution with a concentration of 35-65 wt% is mixed with potassium phosphate ore and subjected to an acid hydrolysis reaction. After the reaction is completed, solid and liquid are separated to obtain a phosphorus-containing filtrate and potassium-rich acid insoluble matter; wherein, the potassium leaching rate in the potassium phosphate ore is ≤3% and the phosphorus leaching rate is ≥96%.

[0019] In one embodiment of the present invention, the particle size of the phosphate rock is 50-200 μm.

[0020] In one embodiment of the present invention, when preparing the potassium-rich acid insoluble material, the amount of nitric acid used is more than 90% of the theoretical consumption; preferably, the amount of nitric acid used is 90% to 110% of the theoretical consumption.

[0021] In one embodiment of the present invention, the acidolysis reaction temperature is ≥40°C.

[0022] In a preferred embodiment of the present invention, the acidolysis reaction temperature is 40–70°C.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The method of this invention provides an economical and green utilization route for potassium-rich acid-insoluble substances. This allows for the full utilization of potassium phosphate deposits, increasing their economic value. Simultaneously, it offers a new approach to utilizing potassium feldspar resources with similar compositions in my country.

[0025] 2) The method of the present invention has a high potassium leaching rate in the acid-insoluble matter, and the potassium and aluminum elements in the filtrate are fully utilized. Its industrial application is relatively mature, and the method is simple and low in cost.

[0026] 3) This invention can improve the leaching rate of phosphorus and reduce the leaching rate of potassium by acid hydrolysis with nitric acid. Furthermore, the use of nitric acid to treat phosphate and potassium ore avoids the problem of potassium fluorosilicate precipitating out and clogging the filter cloth during vacuum filtration and cooling. Detailed Implementation

[0027] The method for comprehensive utilization of potassium-rich acid-insoluble substances of the present invention includes the following steps:

[0028] a. Acid hydrolysis: Potassium-rich acid insolubles are mixed with nitric acid and fluorosilicic acid and reacted at 50-110℃ for 1-6 hours. After the reaction is completed, solid and liquid are separated to obtain potassium-containing filtrate and acid residue.

[0029] b. Neutralization: Mix the potassium-containing filtrate with potassium hydroxide, adjust the pH to 5-8, and separate the solid and liquid to obtain potassium nitrate solution and aluminum hydroxide precipitate;

[0030] c. Crystallization: Potassium nitrate solution is crystallized to obtain potassium nitrate product;

[0031] The potassium-rich acid-insoluble matter is the insoluble matter after acid leaching of potassium phosphate ore.

[0032] The potassium-rich acid-insoluble matter mainly consists of potassium feldspar (K₂O·Al₂O₃·6SiO₂) and a small amount of unreacted metallic minerals and fluorapatite. In one embodiment of the present invention, the composition of the potassium-rich acid-insoluble matter is shown in Table 1.

[0033] Table 1. Analysis of Acid-Insoluble Components

[0034] <![CDATA[P2O5(%)]]> <![CDATA[SiO2(%)]]> CaO (%) MgO (%) <![CDATA[Fe2O3(%)]]> <![CDATA[Al2O3(%)]]> 0.70～2.30 58.85～62.80 1.23～3.20 2.27～1.94 1.98～6.04 8.82～14.15 <![CDATA[K2O(%)]]> <![CDATA[Na2O(%)]]> <![CDATA[TiO2(%)]]> MnO (%) <![CDATA[SO3(%)]]> MER 6.02～9.78 0.11～0.13 0.25～0.77 0.01～0.02 0.33～0.98 9.18～28.23

[0035] In this invention, the component measurement method is XRF sampling.

[0036] In one embodiment of the present invention, in step a, the amount of nitric acid added is 110% to 170% of the theoretical amount, and the amount of fluorosilicic acid added is 30% to 100% of the theoretical amount. Since nitric acid decomposes upon heating, the amount of nitric acid added is higher than the theoretical amount to ensure the effectiveness of acid leaching. If the amount of fluorosilicic acid is too low, the generated HF will be reduced, failing to break down structures such as potassium feldspar in potassium-rich acid-insoluble substances, thus leading to a decrease in potassium leaching rate. In a preferred embodiment of the present invention, the amount of fluorosilicic acid is 50% to 100% of the theoretical amount. In a specific embodiment, the amount of fluorosilicic acid is 90% to 100% of the theoretical amount. In a specific embodiment, the amount of fluorosilicic acid is 100% of the theoretical amount.

[0037] The theoretical amount mentioned in this invention refers to the theoretical acid consumption for the complete reaction of potassium-rich acid-insoluble substances, which can be calculated based on the content of each component in the potassium-rich acid-insoluble substance. For example, if the main components reacting with nitric acid in a certain potassium-rich acid-insoluble substance are potassium feldspar, calcium, magnesium, iron, and aluminum, the theoretical acid consumption for the complete reaction of calcium, magnesium, iron, and aluminum in the potassium-rich acid-insoluble substance can be calculated based on the content of each component, i.e., the theoretical amount. If the main components reacting with fluorosilicic acid in a certain potassium-rich acid-insoluble substance are silicon dioxide and potassium feldspar, the amount of fluorosilicic acid used can be calculated based on the component content, i.e., the theoretical amount.

[0038] The following is the reaction equation:

[0039] Ca5F(PO4)3+10HNO3=5Ca(NO3)2+3H 3 PO4+HF

[0040] Fe₂O₃ + 6HNO₃ = 2Fe(NO₃)₃ + 3H₂O

[0041] MgO + 2HNO3 = Mg(NO3)2 + H2O

[0042] Al₂O₃ + 6HNO₃ = 2Al(NO₃)₃ + 3H₂O

[0043] K2O·Al2O3·SiO2+4HNO3+6H2SiF6=KNO3+Al(NO3)3+9SiF4+8H2O

[0044] 4HF + SiO2 = SiF4↑ + 2H2O

[0045] Unless otherwise specified, all percentages in this invention refer to mass fractions.

[0046] The concentrations of nitric acid and fluorosilicic acid commonly used in this field are applicable to this invention. In one specific embodiment, the concentration of nitric acid is 30% to 40%, and the concentration of fluorosilicic acid is 30% to 32%.

[0047] In one embodiment of the present invention, in step a, the gas generated during the reaction is collected, absorbed, and separated into solid and liquid components. The resulting liquid is a fluorosilicic acid solution, and the resulting solid is washed and dried to obtain silica. The absorption temperature is >70°C.

[0048] In one embodiment of the present invention, the absorption is a two-stage absorption, wherein the primary absorption medium is a fluorosilicic acid solution with a concentration of 10-20 wt%, and the secondary absorption medium is a fluorosilicic acid solution with a concentration of <10 wt%.

[0049] In one embodiment of the present invention, in step b, ammonia or liquid ammonia is used to replace potassium hydroxide for solid-liquid separation, yielding ammonium nitrate solution and aluminum hydroxide precipitate. The ammonium nitrate solution is then reacted with potassium chloride to obtain potassium nitrate solution. Replacing potassium hydroxide with ammonia or liquid ammonia eliminates the need for potassium hydroxide, further reducing costs.

[0050] Step c is the crystallization step, and commonly used potassium nitrate crystallization methods in the art are applicable to this invention. In one embodiment of this invention, when ammonia or liquid ammonia is used to replace potassium hydroxide, ammonium nitrate, potassium nitrate solution, and aluminum hydroxide precipitate are obtained (in addition to ammonium nitrate, potassium ammonium nitrate and other substances may also be present in the solution). The solution is then reacted with potassium chloride in a metathesis reaction, and potassium nitrate is precipitated by cooling and crystallization. After filtration, the potassium nitrate product is obtained.

[0051] In one embodiment of the present invention, the potassium-rich acid-insoluble matter is prepared by the following method: a nitric acid solution with a concentration of 35-65 wt% is mixed with potassium phosphate ore, and an acid hydrolysis reaction is carried out. After the reaction is completed, solid-liquid separation is performed to obtain a phosphorus-containing filtrate and potassium-rich acid-insoluble matter; wherein, the potassium leaching rate in the potassium phosphate ore is ≤3%, and the phosphorus leaching rate is ≥96%. Using nitric acid to leach potassium phosphate ore can increase the phosphorus leaching rate and reduce the potassium leaching rate, thus achieving 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. Centrifuge separation and filtration are generally used in the separation process to avoid the problem of potassium fluorosilicate precipitating and clogging the filter cloth during vacuum filtration and cooling. The production equivalent of the nitric acid method is not large; therefore, the nitric acid method for treating potassium phosphate ore perfectly avoids the disadvantages of the traditional wet phosphoric acid method for treating potassium phosphate ore, and the product is abundant.

[0052] In one embodiment of the present invention, the particle size of the phosphate rock is 50-200 μm.

[0053] In one embodiment of the present invention, when preparing the potassium-rich acid insoluble material, the amount of nitric acid used is 70% to 110% of the theoretical consumption; preferably, the amount of nitric acid used is 90% to 110% of the theoretical consumption.

[0054] The theoretical acid consumption mentioned in this invention refers to the theoretical acid consumption for the complete reaction of potassium phosphate ore, which can be calculated based on the content of each component in the potassium phosphate ore. For example, if the main components reacting with acid in a certain potassium phosphate ore are detected to be 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 potassium phosphate ore can be calculated based on the content of each of the above components, that is, the theoretical acid consumption for the complete reaction of potassium phosphate ore.

[0055] In one embodiment of the invention, the acidolysis reaction temperature is ≥40°C. A reaction temperature above 40°C ensures a high phosphorus leaching rate and a low potassium leaching rate. The reaction temperature can be any temperature above 40°C, such as 50°C, 70°C, etc. Pressure can also be applied to further increase the reaction temperature to 100°C, 200°C, etc.

[0056] To simplify operation and save energy, in a preferred embodiment of the present invention, the acidolysis reaction temperature is 40–70°C.

[0057] The acid-insoluble substances after nitric acid decomposition mainly consist of potassium feldspar (K2O·Al2O3·6SiO2) and a small amount of unreacted metallic minerals and fluorapatite. Through the reaction of nitric acid and fluorosilicic acid, the residual fluorapatite and potassium feldspar are decomposed, activating phosphorus and potassium elements into the liquid phase. The volatilized SiF4 is absorbed by water at high temperature (>70℃) and concentrated to obtain fluorosilicic acid for recycling. KOH is added to the liquid phase to precipitate Al elements. After solid-liquid separation, Al(OH)3 is obtained. The liquid is then concentrated and dried to obtain KNO3. Depending on the company's actual situation, liquid ammonia can also be used to neutralize and precipitate Al elements, followed by the addition of KCl to induce a metathesis reaction. By controlling the precipitation conditions, KNO3 can be obtained.

[0058] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the described embodiments. The phosphate and potassium ore used in the examples was provided by Hanyuan, and its composition is shown in Table 2.

[0059] Table 2. Compositional Analysis of Phosphate and Potassium Ore

[0060] <![CDATA[P2O5(%)]]> <![CDATA[SiO2(%)]]> CaO (%) MgO (%) <![CDATA[Fe2O3(%)]]> <![CDATA[Al2O3(%)]]> 20.970～22.950 20.613～21.470 33.791～35.445 2.265～2.936 3.247～3.607 5.216～5.355 <![CDATA[K2O(%)]]> <![CDATA[Na2O(%)]]> <![CDATA[TiO2(%)]]> MnO (%) <![CDATA[SO3(%)]]> MER 3.148～3.538 0.157～0.163 0.253～0.262 0.032～0.050 0.334～0.632 0.476～0.562

[0061] Example 1

[0062] A. Preparation of potassium-rich acid-insoluble substances:

[0063] A1. Based on the composition of the phosphate and potassium ore, see Table 2. The theoretical consumption of pure nitric acid is 899.1 g / kg of phosphate and potassium ore. The amount of nitric acid added is 90% of the theoretical amount. Nitric acid (concentration: 65%) is injected into the acid tank and mixed with water to prepare an acid hydrolysis solution with a concentration of 40%.

[0064] A2. Weigh a certain amount of mineral powder (mesh size: 0.4% mass fraction for 50-100 mesh mineral powder, and 0.6% mass fraction for 100-200 mesh mineral powder).

[0065] A3. Start the agitator in the reaction tank. Once the tank temperature reaches the predetermined 50°C, add the mineral powder, controlling the feeding time to 50 minutes. After adding the powder, react for another 20 minutes, then perform vacuum filtration. Wash, weigh, and dry the filter cake (i.e., potassium-rich acid-insoluble matter), and measure its composition (see Table 3). At this point, calculate the phosphorus and potassium leaching rates. The phosphorus leaching rate is 96.93%, and the potassium leaching rate is 2.77%.

[0066] Table 3. Analysis of insoluble components of potassium-rich acid

[0067] <![CDATA[P2O5(%)]]> <![CDATA[SiO2(%)]]> CaO (%) MgO (%) <![CDATA[Fe2O3(%)]]> <![CDATA[Al2O3(%)]]> 1.856 58.852 2.650 1.980 5.506 13.754 <![CDATA[K2O(%)]]> <![CDATA[Na2O(%)]]> <![CDATA[TiO2(%)]]> MnO (%) <![CDATA[SO3(%)]]> MER 9.427 0.112 0.759 0.015 0.369 11.44

[0068] B. Treatment of potassium-rich acid-insoluble substances:

[0069] B1. Weigh a certain mass of potassium-rich acid insoluble matter (mesh size: 100-200 mesh) and pour it into the reaction tank.

[0070] B2. Based on the composition of acid-insoluble matter, weigh out nitric acid to add at 170% of the theoretical amount, with a concentration of 40%; weigh out fluorosilicic acid to add at 100% of the theoretical amount, with a concentration of 32%, and mix with nitric acid.

[0071] B3. Start the agitator in the reaction tank. After the temperature of the reaction tank reaches the predetermined temperature (100℃), pour in the mixed acid and react for 6 hours. Filter to obtain potassium-containing filtrate and acid residue. Calculate the phosphorus and potassium leaching rates, where the phosphorus leaching rate is 99.86% and the potassium leaching rate is 92.63%.

[0072] B4. Mix the potassium-containing filtrate with potassium hydroxide, adjust the pH to 5-8, and separate the solid and liquid to obtain potassium nitrate solution and aluminum hydroxide precipitate.

[0073] B5. Crystallize the potassium nitrate solution to obtain the potassium nitrate product.

[0074] It is evident that, under certain process conditions, potassium feldspar in acid-insoluble matter is effectively decomposed, and fluorapatite that was not fully reacted in the early stage is also completely decomposed, and all valuable elements are utilized.

[0075] Comparative Example 1

[0076] (1) Weigh a certain mass of the potassium-rich acid insoluble material (mesh size: 100-200 mesh) obtained in Example 1 and pour it into the reaction tank.

[0077] (2) Based on the composition of potassium-rich acid insoluble matter, potassium feldspar was added to the reactor at a ratio of 1000g potassium feldspar: 3000mL fluorosilicic acid: 1000mL concentrated sulfuric acid. The mixture was stirred until homogeneous, and the temperature was raised to 120℃ under continuous stirring. The mixture was kept at this temperature for 3 hours and then filtered to obtain potassium-containing filtrate and acid residue. The phosphorus and potassium leaching rates were calculated, and the results are shown in Table 4.

[0078] Table 4

[0079]

[0080]

[0081] The results show that when using the potassium-rich acid insoluble material of the present invention with the existing technology CN1557781A, the potassium leaching rate is only 53.43%, which is not high. The reason may be that the potassium-rich acid insoluble material of the present invention has a complex composition and cannot be applied to this technology. Therefore, a new utilization method needs to be found.

[0082] Comparative Example 2 (Nitric acid dosage was 60% of the theoretical dosage)

[0083] (1) Weigh a certain mass of the potassium-rich acid insoluble material (mesh size: 100-200 mesh) obtained in Example 1 and pour it into the reaction tank.

[0084] (2) Based on the composition of potassium-rich acid insoluble matter, weigh out 60% of the theoretical amount of nitric acid with a concentration of 40%; weigh out fluorosilicic acid with a concentration of 100% of the theoretical amount and a concentration of 32%, and mix it with nitric acid.

[0085] (3) Start the agitator in the reaction tank. After the temperature of the reaction tank reaches the predetermined temperature (100℃), pour in the mixed acid and react for 6 hours. Filter to obtain potassium-containing filtrate and acid residue. Calculate the phosphorus and potassium leaching rates, and the results are shown in Table 4.

[0086] The results show that when nitric acid is insufficient, the decomposition rate of potassium feldspar in the acid-insoluble matter remains very low. This is because insufficient nitric acid reduces the amount of HF produced from the reaction with fluorosilicic acid, hindering the effective decomposition of potassium feldspar and lowering the potassium leaching rate.

[0087] Comparative Example 3 (Fluorosilicic acid dosage was 40% of the theoretical dosage)

[0088] (1) Weigh a certain mass of the potassium-rich acid insoluble material (mesh size: 100-200 mesh) obtained in Example 1 and pour it into the reaction tank.

[0089] (2) Based on the composition of potassium-rich acid insoluble matter, weigh out 170% of the theoretical amount of nitric acid with a concentration of 40%; weigh out fluorosilicic acid with a concentration of 32% and add it to the theoretical amount, and mix it with nitric acid.

[0090] (3) Start the agitator in the reaction tank. After the temperature of the reaction tank reaches the predetermined temperature (60℃), pour in the mixed acid and react for 6 hours. Filter to obtain potassium-containing filtrate and acid residue. Calculate the phosphorus and potassium leaching rates, and the results are shown in Table 4.

[0091] Example 2

[0092] The method of Example 1 was used, with only the temperature or the amount of nitric acid changed, and all other conditions remaining the same as in Example 1. Specific variables are shown in Table 5. The composition of the filter cake from step A3 was determined, and the leaching rates of phosphorus and potassium in the phosphate rock were calculated. The results are shown in Table 5.

[0093] Table 5. Variables and leaching rate in Example 2

[0094] serial number condition Phosphorus leaching rate (%) Potassium leaching rate (%) 2-1 Temperature 70℃ 99.40 85.18 2-2 The amount of nitric acid used is 110% of the theoretical amount. 99.21 80.21 2-3 At a temperature of 60℃, the amount of nitric acid used is 170% of the theoretical amount. 99.78 83.92

[0095] Example 3

[0096] The method of Example 1 was used, except that the preparation method of the potassium-rich acid insoluble material was changed. All other conditions were the same as in Example 1. The specific variables are shown in Table 6. The composition of the filter cake in step A3 was determined, and the leaching rates of phosphorus and potassium in the potassium phosphate ore were calculated. The results are shown in Table 6.

[0097] Table 6. Variables and leaching rate in Example 3

[0098] serial number Variable conditions Phosphorus leaching rate (%) Potassium leaching rate (%) 3-1 The nitric acid concentration is 65%. 95.98 2.87 3-2 The amount of nitric acid added was 110% of the theoretical amount. 98.59 2.92 3-3 The predetermined temperature of the reaction vessel is 70℃ 96.18 2.86 3-4 The amount of nitric acid added was 62% of the theoretical amount. 62.93 1.41 3-5 The amount of nitric acid added is 70% of the theoretical amount. 75.45 1.53 3-6 The predetermined temperature of the reaction tank is 30℃ 93.21 1.41 3-7 Replace nitric acid with sulfuric acid. 42.97 2.38 3-8 Replace nitric acid with hydrochloric acid. 86.71 6.03

[0099] The specific steps in 3-7 are as follows:

[0100] A1. Based on the composition of potassium phosphate ore, the theoretical consumption of pure sulfuric acid is 663.1 g / kg potassium phosphate ore. The amount of sulfuric acid added is 90% of the theoretical amount. The sulfuric acid (concentration: 98%) is injected into the acid tank and mixed with water to prepare an acid hydrolysis solution with a concentration of 40%.

[0101] A2. Weigh a certain amount of mineral powder (mesh size: 0.4% mass fraction for 50-100 mesh mineral powder, and 0.6% mass fraction for 100-200 mesh mineral powder).

[0102] A3. Start the agitator in the reaction tank. Once the tank temperature reaches the predetermined temperature (50℃), add the mineral powder, controlling the feeding time to 50 minutes. After adding the powder, react for another 20 minutes, then perform pressure filtration. Wash, weigh, and dry the filter cake, measuring its composition as detailed in Table 7. Calculate the phosphorus and potassium leaching rates; the results are shown in Table 6.

[0103] Pressure filtration is used here because using sulfuric acid will produce potassium fluorosilicate that clogs the filter residue. Under experimental conditions, although vacuum filtration can filter, the filtration speed is significantly slower than pressure filtration.

[0104] Table 7. Analysis of acid-insoluble components in items 3-7

[0105] <![CDATA[P2O5(%)]]> <![CDATA[SiO2(%)]]> CaO (%) MgO (%) <![CDATA[Fe2O3(%)]]> <![CDATA[Al2O3(%)]]> 12.075 18.764 33.244 0.604 1.204 4.193 <![CDATA[K2O(%)]]> <![CDATA[Na2O(%)]]> <![CDATA[TiO2(%)]]> MnO (%) <![CDATA[SO3(%)]]> MER 3.103 0.116 0.238 0.004 22.947 5.397

[0106] The specific steps for 3-8 are as follows:

[0107] (1) Based on the composition of phosphate and potassium ore, the theoretical consumption of pure hydrochloric acid is 520.8 g / kg of phosphate and potassium ore. The amount of hydrochloric acid added is 90% of the theoretical amount. The hydrochloric acid (concentration: 35%) is injected into the acid tank and mixed with water to prepare an acid hydrolysis solution with a concentration of 40%.

[0108] (2) Weigh a certain amount of mineral powder (mesh size: 0.4% for 50-100 mesh mineral powder and 0.6% for 100-200 mesh mineral powder).

[0109] (3) Start the agitator in the reaction tank. After the temperature of the reaction tank reaches the predetermined temperature (50℃), add the mineral powder one spoonful at a time, controlling the feeding time to 50 minutes. After the feeding is complete, react for another 20 minutes, and then perform vacuum filtration. Wash, weigh, and dry the filter cake and measure its composition, as detailed in Table 8. Calculate the phosphorus and potassium leaching rates, and the results are shown in Table 6.

[0110] Table 8. Analysis of acid-insoluble components in items 3-8

[0111] <![CDATA[P2O5(%)]]> <![CDATA[SiO2(%)]]> CaO (%) MgO (%) <![CDATA[Fe2O3(%)]]> <![CDATA[Al2O3(%)]]> 7.997 51.346 7.433 1.432 1.653 11.548 <![CDATA[K2O(%)]]> <![CDATA[Na2O(%)]]> <![CDATA[TiO2(%)]]> MnO (%) <![CDATA[SO3(%)]]> MER 8.223 0.090 0.648 0.007 1.282 1.830

[0112] The results showed that the leaching rate of phosphorus and the separation effect of phosphorus and potassium in hydrochloric acid decomposition of potassium phosphate rock were far 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.

Claims

1. A method for the comprehensive utilization of potassium-rich acid-insoluble substances, characterized in that, Includes the following steps: a. Acid hydrolysis: Potassium-rich acid-insoluble matter is mixed with nitric acid and fluorosilicic acid and reacted at 50–110℃ for 1–6 h. After the reaction is complete, solid and liquid are separated to obtain potassium-containing filtrate and acid residue. In step a, the amount of nitric acid added is 110%–170% of the theoretical amount, and the amount of fluorosilicic acid added is 90%–100% of the theoretical amount. b. Neutralization: Mix the potassium-containing filtrate with potassium hydroxide, adjust the pH to 5-8, and separate the solid and liquid to obtain potassium nitrate solution and aluminum hydroxide precipitate; c. Crystallization: Potassium nitrate solution is crystallized to obtain potassium nitrate product; The potassium-rich acid insoluble matter is the insoluble matter after acid leaching of potassium phosphate ore. The potassium-rich acid insoluble matter is prepared by the following method: a nitric acid solution with a concentration of 35-65 wt% is mixed with potassium phosphate ore and subjected to acid hydrolysis. After the reaction is completed, solid and liquid are separated to obtain phosphorus-containing filtrate and potassium-rich acid insoluble matter. The potassium leaching rate in the potassium phosphate ore is ≤3%, and the phosphorus leaching rate is ≥96%.

2. The method for comprehensive utilization of potassium-rich acid-insoluble substances according to claim 1, characterized in that: In step a, the gas generated during the reaction is collected, absorbed, and separated into solid and liquid components. The resulting liquid is a fluorosilicic acid solution, and the resulting solid is washed and dried to obtain silica. The absorption temperature is >70℃.

3. The method for comprehensive utilization of potassium-rich acid-insoluble substances according to claim 2, characterized in that: The absorption is a two-stage absorption, with the primary absorption medium being a fluorosilicic acid solution with a concentration of 10–20 wt% and the secondary absorption medium being a fluorosilicic acid solution with a concentration of <10 wt%.

4. The method for comprehensive utilization of potassium-rich acid-insoluble substances according to claim 1, characterized in that: In step b, ammonia or liquid ammonia is used to replace potassium hydroxide, and solid-liquid separation is performed to obtain ammonium nitrate solution and aluminum hydroxide precipitate. Then, the ammonium nitrate solution is reacted with potassium chloride to obtain potassium nitrate solution.

5. The method for comprehensive utilization of potassium-rich acid-insoluble substances according to claim 1, characterized in that: The particle size of the phosphate rock is 50–200 μm.

6. The method for comprehensive utilization of potassium-rich acid-insoluble substances according to claim 1, characterized in that: When preparing potassium-rich acid insolubles, the amount of nitric acid used is more than 90% of the theoretical consumption.

7. The method for comprehensive utilization of potassium-rich acid-insoluble substances according to claim 6, characterized in that: When preparing potassium-rich acid insolubles, the amount of nitric acid used is 90% to 110% of the theoretical consumption.

8. The method for comprehensive utilization of potassium-rich acid-insoluble substances according to claim 1, characterized in that: The acid hydrolysis reaction temperature is ≥40℃.

9. The method for comprehensive utilization of potassium-rich acid-insoluble substances according to claim 8, characterized in that: The acidolysis reaction takes place at a temperature of 40–70 °C.

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