A water-soluble fertilizer produced from low-grade ores and a preparation method thereof

Abstract

The application relates to a water-soluble fertilizer produced by low-grade ore and a preparation method thereof, and belongs to the technical field of low-grade phosphate ore processing. After low-grade phosphate ore is crushed, a process of one-time rough separation, one-time fine separation and one-time scavenging is carried out to obtain phosphate concentrate; the phosphate concentrate is mixed with nitric acid to obtain acidolysis liquid; the acidolysis liquid is neutralized until no precipitation is generated; the precipitation is filtered; sulfuric acid is added to the precipitation to carry out secondary acidolysis, and secondary acidolysis liquid is obtained; liquid ammonia or ammonia water is added to the secondary acidolysis liquid for neutralization; after the reaction is completed, the reaction liquid is filtered, and the obtained filtrate is the water-soluble phosphate fertilizer. The application can produce water-soluble phosphate fertilizer by exploiting low-grade phosphate ore, improve the utilization degree of phosphate resources, and reduce the production cost of enterprises.

Description

Technical Field

[0001] This invention belongs to the technical field of low-grade phosphate rock processing, and relates to a water-soluble fertilizer produced from low-grade phosphate rock and its preparation method. Background Technology

[0002] Water-soluble fertilizer is a new type of fertilizer. Its advantages lie in the fact that its nutrients are dissolved in water, making it suitable for drip irrigation and sprinkler irrigation. Plants can fully absorb the nutrients they need, and it causes less environmental pollution. Currently, wet-process in-situ chelation of phosphate is used to produce in-situ chelated water-soluble fertilizers containing micronutrients. The herbal ingredient is organic water-soluble monoammonium phosphate. This water-soluble fertilizer dissolves quickly, which is beneficial for plant absorption. However, the production process of this product requires high-quality phosphate with low impurity content, meaning that the grade of the phosphate rock must be relatively high.

[0003] Although my country has abundant phosphate rock reserves, most of them are low- to medium-grade phosphate rock, which is difficult to beneficiate and has high production costs for enterprises. With the continuous depletion of phosphate resources, the development and utilization of low- to medium-grade phosphate rock is of great significance for making full use of my country's phosphate resources, reducing the production costs of enterprises, and promoting the sustainable development of the phosphate chemical industry.

[0004] Producing water-soluble fertilizers from low-grade minerals is a challenging and innovative process. At the same time, it is a promising field. Through continuous technological innovation and process optimization, it is possible to achieve efficient resource utilization and sustainable environmental development. This also provides agricultural production with more environmentally friendly and efficient fertilizer options, contributing to the green development of agriculture. Summary of the Invention

[0005] The purpose of this invention is to develop and utilize low-grade phosphate rock to produce water-soluble phosphate fertilizer, thereby improving resource utilization and reducing enterprise production costs.

[0006] This invention utilizes flotation of low-grade phosphate rock to obtain concentrate and tailings, and then uses the concentrate to produce monoammonium phosphate, an organic water-soluble fertilizer. The core technologies are as follows:

[0007] A method for preparing water-soluble fertilizer from low-grade phosphate rock involves crushing the low-grade phosphate rock, followed by flotation, acid hydrolysis, and neutralization with ammonia to obtain water-soluble phosphate fertilizer.

[0008] The flotation process employs a single roughing, a single cleaning, and a single scavenging stage to obtain phosphate concentrate. During the flotation process, the roughing reagents are: sodium carbonate 1.0-1.5 kg / t, water glass 0.2-0.3 kg / t, sodium α-chlorooctanoate 0.2-0.3 kg / t, octyl hydroxamic acid 0.1-0.2 kg / t, and α-sulfo fatty acid methyl ester 0.04-0.05 kg / t. The cleaning reagents... The concentrations of sodium α-chlorooctanoate are 0.025-0.075 kg / t, octyl hydroxamic acid is 0.025-0.05 kg / t, and α-sulfo fatty acid methyl ester is 0.007-0.01 kg / t; the scavenging agents are sodium α-chlorooctanoate 0.07-0.1 kg / t, octyl hydroxamic acid 0.05-0.08 kg / t, and α-sulfo fatty acid methyl ester is 0.01-0.015 kg / t.

[0009] The acid hydrolysis process involves adding phosphate concentrate to nitric acid for a mixed reaction to obtain an acid hydrolysis solution. The solution is then neutralized until no more precipitate forms. The precipitate is filtered, and sulfuric acid is added to the precipitate for a second acid hydrolysis to obtain a second acid hydrolysis solution.

[0010] The ammonia neutralization involves adding liquid ammonia or ammonia water to the secondary acid hydrolysis solution for neutralization. After the reaction is complete, the reaction solution is filtered, and the resulting filtrate is the water-soluble phosphate fertilizer.

[0011] Preferably, the roughing process is as follows: the raw ore is ground to a particle size of -0.074mm, accounting for more than 70%, to prepare a slurry. Sodium carbonate 1.0-1.5 kg / t and water glass 0.2-0.3 kg / t are added and the slurry is adjusted for 5-10 minutes. Sodium α-chlorooctanoate 0.2-0.3 kg / t, octyl hydroxamic acid 0.1-0.2 kg / t and α-sulfo fatty acid methyl ester 0.04-0.05 kg / t are added and the mixture is stirred for 3-5 minutes to carry out roughing, thereby obtaining roughing concentrate and roughing tailings.

[0012] Preferably, the refining process involves adding 0.025-0.075 kg / t of sodium α-chlorooctanoate, 0.025-0.05 kg / t of octyl hydroxamic acid, and 0.007-0.01 kg / t of α-sulfo fatty acid methyl ester to the rough concentrate obtained after roughing, and stirring for 3-5 minutes to obtain concentrate and refined middlings.

[0013] Preferably, the scavenging is performed by adding 0.07-0.1 kg / t of sodium α-chlorooctanoate, 0.05-0.08 kg / t of octyl hydroxamic acid, and 0.01-0.015 kg / t of α-sulfo fatty acid methyl ester to the roughing tailings obtained after roughing, and stirring for 3-5 minutes to perform scavenging to obtain scavenged ore and tailings.

[0014] Preferably, the temperature of the nitric acid mixing reaction is 55-75℃, the reaction time is 1.5-2h, the stirring speed is controlled at 350-400r / min during the reaction, the concentration of nitric acid is 50-60%, and the amount of nitric acid used is 1.0-1.3 times the mass of low-grade phosphate rock.

[0015] Preferably, during the acid hydrolysis process, liquid ammonia or ammonia water is used to neutralize the acid hydrolysate to a pH of 7-7.5.

[0016] Preferably, during the acidolysis process, the concentration of sulfuric acid is 40-60%, the amount of sulfuric acid used is 1.0-1.3 times the mass of low-grade phosphate rock, the reaction temperature is 55-75℃, the reaction time is 1.5-2h, and the stirring speed is controlled at 350-400r / min during the reaction.

[0017] Preferably, the pH value is controlled at 4-5 during the ammonia neutralization process.

[0018] Preferably, the selected middlings obtained from the fine selection and the scavenged middlings obtained from the scavenging are returned to the roughing selection for further selection, and the scavenged tailings obtained from the scavenging are processed into low-nutrient fertilizer.

[0019] Preferably, the filtrate obtained by neutralizing ammonia is evaporated, concentrated, and dried to obtain a solid water-soluble phosphate fertilizer.

[0020] A water-soluble fertilizer prepared by the above-described preparation method has monoammonium phosphate as its main component.

[0021] The beneficial effects of this invention are:

[0022] 1. The concentrate obtained by the flotation process of this invention has P2O5 ≥ 33% ​​and MER ≤ 0.05.

[0023] 2. The solid obtained by evaporating, concentrating and drying the water-soluble fertilizer liquid of the present invention is a white powder with water-insoluble matter ≤0.5%. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the preparation method of the present invention. Detailed Implementation

[0025] Example 1

[0026] A water-soluble fertilizer produced from low-grade ore is prepared by the following method:

[0027] (1) Prepare low-grade phosphate rock and test the elemental composition of the raw ore: P2O5 17.88%, MgO 3.27%, Fe2O3 1.56%, Al2O3 3.96%, SiO2 18.53%. After crushing the low-grade phosphate rock, grind it to a particle size of -0.074mm, with a particle size of 85%, and make a slurry. Add 1.5kg / t of sodium carbonate and 0.2kg / t of water glass and adjust the slurry for 6 minutes. Add 0.3kg / t of sodium α-chlorooctanoate, 0.2kg / t of octyl hydroxamic acid and 0.05kg / t of α-sulfo fatty acid methyl ester, stir for 3 minutes and carry out roughing to obtain roughing concentrate and roughing tailings.

[0028] (2) Add 0.075 kg / t of sodium α-chlorooctanoate, 0.025 kg / t of octyl hydroxamic acid and 0.008 kg / t of α-sulfo fatty acid methyl ester to the rough concentrate obtained after roughing, stir for 3 min for fine cleaning, and obtain concentrate and fine middlings. The fine middlings can be returned to roughing for re-selection. The obtained concentrate contains 34.68% P2O5, 0.82% MgO, 0.61% Fe2O3, 0.64% Al2O3 and 5.85% SiO2.

[0029] (3) Add 0.07 kg / t of sodium α-chlorooctanoate, 0.05 kg / t of octyl hydroxamic acid and 0.01 kg / t of α-sulfo fatty acid methyl ester to the rough tailings obtained after roughing, stir for 3 min and perform scavenging to obtain scavenged ore and tailings. The scavenged ore can be returned to the roughing for re-selection, and the tailings can be prepared into low-component fertilizer.

[0030] (4) The selected phosphate concentrate was mixed with 60% nitric acid and reacted. The amount of nitric acid was 1.0 times the mass of the low-grade phosphate ore. The reaction temperature was 60℃ and the reaction time was 100 min. During the reaction, the stirring speed was controlled at 350 r / min to obtain an acid hydrolysis solution. Then, the acid hydrolysis solution was neutralized with ammonia water to pH 7. The precipitate no longer precipitated. The precipitate was filtered and 60% sulfuric acid was added to the precipitate for secondary acid hydrolysis. The amount of sulfuric acid was 1.1 times the mass of the low-grade phosphate ore. The reaction temperature was 60℃ and the reaction time was 100 min. During the reaction, the stirring speed was controlled at 400 r / min to obtain a secondary acid hydrolysis solution.

[0031] (5) Add ammonia water to the secondary acid hydrolysis solution for neutralization, control the pH to 4, filter the reaction solution after the reaction is completed, and the resulting filtrate is water-soluble phosphate fertilizer, in which the P2O5 content reaches 62.3%.

[0032] If it is to be prepared as a solid, the filtrate obtained in step (5) is evaporated, concentrated and dried to obtain a solid water-soluble phosphate fertilizer, which is a white powder.

[0033] Example 2

[0034] A water-soluble fertilizer produced from low-grade ore is prepared by the following method:

[0035] (1) Prepare low-grade phosphate rock and test the elemental composition of the raw ore: P2O5 17.88%, MgO 3.27%, Fe2O3 1.56%, Al2O3 3.96%, SiO2 18.53%. After crushing the low-grade phosphate rock, grind it to a particle size of -0.074mm with a particle size of 80% to make a slurry. Add 1.0kg / t of sodium carbonate and 0.2kg / t of water glass and adjust the slurry for 7min. Add 0.2kg / t of sodium α-chlorooctanoate, 0.2kg / t of octyl hydroxamic acid and 0.04kg / t of α-sulfo fatty acid methyl ester and stir for 5min for roughing to obtain rough concentrate and rough tailings.

[0036] (2) Add 0.025 kg / t of sodium α-chlorooctanoate, 0.05 kg / t of octyl hydroxamic acid and 0.007 kg / t of α-sulfo fatty acid methyl ester to the rough concentrate obtained after roughing, stir for 5 min for fine cleaning, and obtain concentrate and fine middlings. The fine middlings can be returned to roughing for re-selection. The obtained concentrate contains 33.14% P2O5, 0.78% MgO, 0.62% Fe2O3, 0.69% Al2O3 and 5.23% SiO2.

[0037] (3) Add 0.08 kg / t of sodium α-chlorooctanoate, 0.06 kg / t of octyl hydroxamic acid and 0.014 kg / t of α-sulfo fatty acid methyl ester to the rough tailings obtained after roughing, stir for 5 min and perform scavenging to obtain scavenged ore and tailings. The scavenged ore can be returned to the roughing for re-selection, and the tailings can be prepared into low-component fertilizer.

[0038] (4) The selected phosphate concentrate was mixed with 50% nitric acid and reacted. The amount of nitric acid was 1.3 times the mass of the low-grade phosphate ore. The reaction temperature was 75℃ and the reaction time was 1.5h. During the reaction, the stirring speed was controlled at 400r / min to obtain an acid hydrolysis solution. Then, the acid hydrolysis solution was neutralized with ammonia water to pH 7.5. The precipitate no longer precipitated. The precipitate was filtered and 40% sulfuric acid was added to the precipitate for secondary acid hydrolysis. The amount of sulfuric acid was 1.3 times the mass of the low-grade phosphate ore. The reaction temperature was 75℃ and the reaction time was 1.5h. During the reaction, the stirring speed was controlled at 400r / min to obtain a secondary acid hydrolysis solution.

[0039] (5) Add liquid ammonia or ammonia water to the secondary acid hydrolysis solution for neutralization, neutralize pH 5, filter the reaction solution after the reaction is completed, and the resulting filtrate is water-soluble phosphate fertilizer, in which the P2O5 content reaches 60.1%.

[0040] If it is to be prepared as a solid, the filtrate obtained in step (5) is evaporated, concentrated and dried to obtain a solid water-soluble phosphate fertilizer, which is a white powder.

[0041] Example 3

[0042] A water-soluble fertilizer produced from low-grade ore is prepared by the following method:

[0043] (1) Prepare low-grade phosphate rock and test the elemental composition of the raw ore: P2O5 17.88%, MgO 3.27%, Fe2O3 1.56%, Al2O3 3.96%, SiO2 18.53%. After crushing the low-grade phosphate rock, grind it to a particle size of -0.074mm, with a particle size of 75%, and make a slurry. Add 1.2kg / t of sodium carbonate and 0.25kg / t of water glass and adjust the slurry for 10min. Add 0.3kg / t of sodium α-chlorooctanoate, 0.2kg / t of octyl hydroxamic acid and 0.05kg / t of α-sulfo fatty acid methyl ester, stir for 4min and carry out roughing to obtain roughing concentrate and roughing tailings.

[0044] (2) Add 0.05 kg / t of sodium α-chlorooctanoate, 0.04 kg / t of octyl hydroxamic acid and 0.009 kg / t of α-sulfo fatty acid methyl ester to the rough concentrate obtained after roughing, stir for 4 min for fine cleaning, and obtain concentrate and fine middlings. The fine middlings can be returned to roughing for re-selection. The obtained concentrate contains 34.22% P2O5, 0.84% ​​MgO, 0.63% Fe2O3, 0.72% Al2O3 and 5.78% SiO2.

[0045] (3) Add 0.1 kg / t of sodium α-chlorooctanoate, 0.05 kg / t of octyl hydroxamic acid and 0.015 kg / t of α-sulfo fatty acid methyl ester to the rough tailings obtained after roughing, stir for 4 min for scavenging, and obtain scavenged ore and tailings. The scavenged ore can be returned to the roughing for re-selection, and the tailings can be prepared into low-component fertilizer.

[0046] (4) The selected phosphate concentrate was mixed with 55% nitric acid and reacted. The amount of nitric acid was 1.2 times the mass of the low-grade phosphate ore. The reaction temperature was 55℃ and the reaction time was 2h. During the reaction, the stirring speed was controlled at 400r / min to obtain an acid hydrolysis solution. Then, the acid hydrolysis solution was neutralized with ammonia water to pH 7. The precipitate no longer precipitated. The precipitate was filtered and 50% sulfuric acid was added to the precipitate for secondary acid hydrolysis. The amount of sulfuric acid was 1.2 times the mass of the low-grade phosphate ore. The reaction temperature was 55℃ and the reaction time was 2h. During the reaction, the stirring speed was controlled at 400r / min to obtain a secondary acid hydrolysis solution.

[0047] (5) Add liquid ammonia or ammonia water to the secondary acid hydrolysis solution for neutralization, and neutralize the pH to 4.5. After the reaction is completed, filter the reaction solution and the resulting filtrate is water-soluble phosphate fertilizer, in which the P2O5 content reaches 61.8%.

[0048] If it is to be prepared as a solid, the filtrate obtained in step (5) is evaporated, concentrated and dried to obtain a solid water-soluble phosphate fertilizer, which is a white powder.

[0049] Comparative Example 1

[0050] A water-soluble fertilizer produced from low-grade ore is prepared by the following method:

[0051] (1) Prepare low-grade phosphate ore and test the elemental composition of the raw ore: P2O5 17.88%, MgO 3.27%, Fe2O3 1.56%, Al2O3 3.96%, SiO2 18.53%. After crushing the low-grade phosphate ore, grind it to a particle size of -0.074mm with a particle size of 85% to make a slurry. Add 1.5kg / t of sodium carbonate and 0.2kg / t of water glass and adjust the slurry for 6 minutes. Add 0.3kg / t of sodium α-chlorooctanoate and 0.2kg / t of octyl hydroxamic acid and stir for 3 minutes for roughing to obtain rough concentrate and rough tailings.

[0052] (2) Add 0.075 kg / t of sodium α-chlorooctanoate and 0.025 kg / t of octyl hydroxamic acid to the rough concentrate obtained after roughing, stir for 3 min for fine cleaning, and obtain concentrate and fine middlings. The fine middlings can be returned to roughing for further fine cleaning. The obtained concentrate contains 0.78% P2O5, 0.94% MgO, 0.87% Fe2O3, 0.76% Al2O3, and 6.46% SiO2.

[0053] (3) Add 0.07 kg / t of sodium α-chlorooctanoate and 0.05 kg / t of octyl hydroxamic acid to the rough tailings obtained after roughing, stir for 3 min and perform scavenging to obtain scavenged ore and tailings. The scavenged ore can be returned to the roughing for re-selection, and the tailings can be prepared into low-component fertilizer.

[0054] (4) The selected phosphate concentrate was mixed with 60% nitric acid and reacted. The amount of nitric acid was 1.0 times the mass of the low-grade phosphate ore. The reaction temperature was 60℃ and the reaction time was 100 min. During the reaction, the stirring speed was controlled at 350 r / min to obtain an acid hydrolysis solution. Then, the acid hydrolysis solution was neutralized with ammonia water to pH 7. The precipitate no longer precipitated. The precipitate was filtered and 60% sulfuric acid was added to the precipitate for secondary acid hydrolysis. The amount of sulfuric acid was 1.1 times the mass of the low-grade phosphate ore. The reaction temperature was 60℃ and the reaction time was 100 min. During the reaction, the stirring speed was controlled at 400 r / min to obtain a secondary acid hydrolysis solution.

[0055] (5) Add ammonia water to the secondary acid hydrolysis solution for neutralization, control the pH to 4, and after the reaction is completed, filter the reaction solution. The resulting filtrate is water-soluble phosphate fertilizer.

[0056] If it is to be prepared as a solid, the filtrate obtained in step (5) is evaporated, concentrated and dried to obtain a solid water-soluble phosphate fertilizer, which is a white powder.

[0057] Comparative Example 2

[0058] A water-soluble fertilizer produced from low-grade ore is prepared by the following method:

[0059] (1) Prepare low-grade phosphate rock and test the elemental composition of the raw ore: P2O5 17.88%, MgO 3.27%, Fe2O3 1.56%, Al2O3 3.96%, SiO2 18.53%. After crushing the low-grade phosphate rock, grind it to a particle size of -0.074mm with a particle size of 85% to make a slurry. Add 1.5kg / t of sodium carbonate and 0.2kg / t of water glass and adjust the slurry for 6 minutes. Add 0.5kg / t of sodium α-chlorooctanoate and 0.05kg / t of α-sulfo fatty acid methyl ester and stir for 3 minutes for roughing to obtain rough concentrate and rough tailings.

[0060] (2) Add 0.1 kg / t of sodium α-chlorooctanoate and 0.008 kg / t of α-sulfofatty acid methyl ester to the rough concentrate obtained after roughing, stir for 3 min for fine cleaning, and obtain concentrate and fine middlings. The fine middlings can be returned to roughing for further fine cleaning. The obtained concentrate contains 28.25% P2O5, 1.03% MgO, 0.94% Fe2O3, 0.88% Al2O3, and 7.24% SiO2.

[0061] (3) Add 0.12 kg / t of sodium α-chlorooctanoate and 0.01 kg / t of α-sulfofatty acid methyl ester to the rough tailings obtained after roughing, stir for 3 min and perform scavenging to obtain scavenged ore and tailings. The scavenged ore can be returned to the roughing for re-selection, and the tailings can be prepared into low-component fertilizer.

[0062] (4) The selected phosphate concentrate was mixed with 60% nitric acid and reacted. The amount of nitric acid was 1.0 times the mass of the low-grade phosphate ore. The reaction temperature was 60℃ and the reaction time was 100 min. During the reaction, the stirring speed was controlled at 350 r / min to obtain an acid hydrolysis solution. Then, the acid hydrolysis solution was neutralized with ammonia water to pH 7. The precipitate no longer precipitated. The precipitate was filtered and 60% sulfuric acid was added to the precipitate for secondary acid hydrolysis. The amount of sulfuric acid was 1.1 times the mass of the low-grade phosphate ore. The reaction temperature was 60℃ and the reaction time was 100 min. During the reaction, the stirring speed was controlled at 400 r / min to obtain a secondary acid hydrolysis solution.

[0063] (5) Add ammonia water to the secondary acid hydrolysis solution for neutralization, control the pH to 4, and after the reaction is completed, filter the reaction solution. The resulting filtrate is water-soluble phosphate fertilizer.

[0064] If it is to be prepared as a solid, the filtrate obtained in step (5) is evaporated, concentrated and dried to obtain a solid water-soluble phosphate fertilizer, which is a white powder.

[0065] Comparative Example 3

[0066] A water-soluble fertilizer produced from low-grade ore is prepared by the following method:

[0067] (1) Prepare low-grade phosphate rock and test the elemental composition of the raw ore: P2O5 17.88%, MgO 3.27%, Fe2O3 1.56%, Al2O3 3.96%, SiO2 18.53%. After crushing the low-grade phosphate rock, grind it to a particle size of -0.074mm, with a particle size of 85%, and make a slurry. Add 1.5kg / t of sodium carbonate and 0.2kg / t of water glass and adjust the slurry for 6 minutes. Add 0.5kg / t of octyl hydroxamic acid and 0.05kg / t of α-sulfo fatty acid methyl ester and stir for 3 minutes for roughing to obtain rough concentrate and rough tailings.

[0068] (2) Add 0.1 kg / t of octyl hydroxamic acid and 0.008 kg / t of α-sulfo fatty acid methyl ester to the rough concentrate obtained after roughing, stir for 3 min for fine cleaning, and obtain concentrate and fine middlings. Fine middlings can be returned to roughing for further fine cleaning. The obtained concentrate contains 28.46% P2O5, 1.28% MgO, 1.33% Fe2O3, 0.98% Al2O3, and 8.24% SiO2.

[0069] (3) Add 0.12 kg / t of octyl hydroxamic acid and 0.01 kg / t of α-sulfo fatty acid methyl ester to the rough tailings obtained after roughing, stir for 3 min for scavenging, and obtain scavenged ore and tailings. The scavenged ore can be returned to the roughing for re-selection, and the tailings are prepared into low-component fertilizer.

[0070] (4) The selected phosphate concentrate was mixed with 60% nitric acid and reacted. The amount of nitric acid was 1.0 times the mass of the low-grade phosphate ore. The reaction temperature was 60℃ and the reaction time was 100 min. During the reaction, the stirring speed was controlled at 350 r / min to obtain an acid hydrolysis solution. Then, the acid hydrolysis solution was neutralized with ammonia water to pH 7. The precipitate no longer precipitated. The precipitate was filtered and 60% sulfuric acid was added to the precipitate for secondary acid hydrolysis. The amount of sulfuric acid was 1.1 times the mass of the low-grade phosphate ore. The reaction temperature was 60℃ and the reaction time was 100 min. During the reaction, the stirring speed was controlled at 400 r / min to obtain a secondary acid hydrolysis solution.

[0071] (5) Add ammonia water to the secondary acid hydrolysis solution for neutralization, control the pH to 4, and after the reaction is completed, filter the reaction solution. The resulting filtrate is water-soluble phosphate fertilizer.

[0072] If it is to be prepared as a solid, the filtrate obtained in step (5) is evaporated, concentrated and dried to obtain a solid water-soluble phosphate fertilizer, which is a white powder.

Claims

1. A method for preparing water-soluble fertilizer from low-grade phosphate rock, comprising crushing low-grade phosphate rock, followed by flotation, acid hydrolysis, and neutralization with ammonia to obtain water-soluble phosphate fertilizer, characterized in that... The flotation process employs a single roughing, a single cleaning, and a single scavenging stage to obtain phosphate concentrate. During the flotation process, the roughing reagents are: sodium carbonate 1.0-1.5 kg / t, water glass 0.2-0.3 kg / t, sodium α-chlorooctanoate 0.2-0.3 kg / t, octyl hydroxamic acid 0.1-0.2 kg / t, and α-sulfo fatty acid methyl ester 0.04-0.05 kg / t. The cleaning reagents... The concentrations of sodium α-chlorooctanoate are 0.025-0.075 kg / t, octyl hydroxamic acid is 0.025-0.05 kg / t, and α-sulfo fatty acid methyl ester is 0.007-0.01 kg / t; the scavenging agents are sodium α-chlorooctanoate 0.07-0.1 kg / t, octyl hydroxamic acid 0.05-0.08 kg / t, and α-sulfo fatty acid methyl ester is 0.01-0.015 kg / t. The acid hydrolysis process involves adding phosphate concentrate to nitric acid for a mixed reaction to obtain an acid hydrolysis solution. The solution is then neutralized until no more precipitate forms. The precipitate is filtered, and sulfuric acid is added to the precipitate for a second acid hydrolysis to obtain a second acid hydrolysis solution. The ammonia neutralization involves adding liquid ammonia or ammonia water to the secondary acid hydrolysis solution for neutralization. After the reaction is complete, the reaction solution is filtered, and the resulting filtrate is the water-soluble phosphate fertilizer.

2. The method for preparing water-soluble fertilizer from low-grade ore according to claim 1, characterized in that, The roughing process involves grinding the raw ore to a particle size of -0.074mm, with a particle size percentage of over 70%, to prepare a slurry. Sodium carbonate (1.0-1.5 kg / t) and water glass (0.2-0.3 kg / t) are added and the slurry is adjusted for 5-10 minutes. Then, sodium α-chlorooctanoate (0.2-0.3 kg / t), octyl hydroxamic acid (0.1-0.2 kg / t), and α-sulfo fatty acid methyl ester (0.04-0.05 kg / t) are added and the mixture is stirred for 3-5 minutes to perform roughing, yielding a roughing concentrate and roughing tailings.

3. The method for preparing water-soluble fertilizer from low-grade ore according to claim 1, characterized in that, The fine-refinement process involves adding 0.025-0.075 kg / t of sodium α-chlorooctanoate, 0.025-0.05 kg / t of octyl hydroxamic acid, and 0.007-0.01 kg / t of α-sulfo fatty acid methyl ester to the rough concentrate obtained after roughing, and stirring for 3-5 minutes to obtain concentrate and fine-refinement middlings.

4. The method for preparing water-soluble fertilizer from low-grade ore according to claim 1, characterized in that, The scavenging process involves adding 0.07-0.1 kg / t of sodium α-chlorooctanoate, 0.05-0.08 kg / t of octyl hydroxamic acid, and 0.01-0.015 kg / t of α-sulfo fatty acid methyl ester to the roughing tailings obtained after roughing, stirring for 3-5 minutes to perform scavenging, and obtaining scavenged ore and tailings.

5. The method for preparing water-soluble fertilizer from low-grade ore according to claim 1, characterized in that, The temperature for the nitric acid mixture reaction is 55-75℃, the reaction time is 1.5-2h, the stirring speed is controlled at 350-400r / min during the reaction, the concentration of nitric acid is 50-60%, and the amount of nitric acid used is 1.0-1.3 times the mass of low-grade phosphate rock.

6. The method for preparing water-soluble fertilizer from low-grade ore according to claim 1, characterized in that, During the acidolysis process, liquid ammonia or ammonia water is used to neutralize the acidolysis solution to a pH of 7-7.

5. The concentration of sulfuric acid used in the acidolysis process is controlled at 40-60%, and the amount of sulfuric acid used is 1.0-1.3 times the mass of low-grade phosphate rock. The reaction temperature is 55-75℃, the reaction time is 1.5-2h, and the stirring speed is controlled at 350-400r / min during the reaction.

7. The method for preparing water-soluble fertilizer from low-grade ore according to claim 1, characterized in that, The pH value is controlled at 4-5 during the ammonia neutralization process.

8. The method for preparing water-soluble fertilizer from low-grade ore according to claim 1, characterized in that, The selected middlings and the scavenged middlings are returned to the roughing process for further selection, while the scavenged tailings are processed into low-nutrient fertilizer.

9. The method for preparing water-soluble fertilizer from low-grade ore according to claim 1, characterized in that, The filtrate obtained by neutralizing ammonia is evaporated, concentrated, and dried to obtain solid water-soluble phosphate fertilizer.

10. A water-soluble fertilizer prepared by the preparation method of claim 1.

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