Method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer

Abstract

The invention discloses a method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing an ammonium phosphate fertilizer. The method specifically comprises the following steps: (1) drying, grinding and screening the ferrophosphorus slag from which lithium is extracted; (2) mixing with an ammonium sulfide solution, carrying out wet reaction, and separating to respectively obtain an ammonium phosphate solution, a ferrous sulfide solid and an elemental sulfur solid; (3) carrying out vacuum evaporation and concentration on the ammonium phosphate solution, cooling, crystallizing and drying to obtain an ammonium phosphate fertilizer; (4) the ferrous sulfide solid is subjected to drying, high-temperature roasting and purification, and iron powder is obtained; and (5) recycling the elemental sulfur solid. According to the method, efficient separation and gradient recovery of phosphorus, iron and sulfur elements in the ferrophosphorus slag are achieved, the ammonium phosphate fertilizer with the high additional value is co-produced, the technological process is simple, economical and environmentally friendly, and the method is suitable for industrial popularization and has important significance in promoting resource recycling in the lithium iron phosphate battery recovery industry.

Description

Technical Field

[0001] The invention relates to the technical field of waste resource recycling, and more specifically to a method for recycling phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer. Background Art

[0002] In the context of the carbon neutral era, the new energy vehicle industry is developing rapidly. Lithium iron phosphate batteries are widely used in new energy vehicles because of their high thermal stability, long cycle life and low cost. The service life of lithium iron phosphate batteries is generally between 3 and 10 years. With the vigorous development of new energy vehicles, power batteries will inevitably usher in a blowout retirement. According to statistics, the total retired batteries in my country will reach 125GWh in 2025, of which lithium iron phosphate batteries account for more than 50%. Therefore, if the retired lithium iron phosphate batteries are not properly disposed of, they will seriously harm the environment and cause a waste of valuable resources. After selective leaching and recovery of lithium iron phosphate, ferrophosphorus slag containing a large amount of valuable metal phosphorus and iron will be obtained. The ferrophosphorus slag contains iron phosphate, carbon slag and a small amount of impurities. Effective recovery of it can reduce dependence on primary mineral sources.

[0003] The main component of ferrophosphorus slag is iron phosphate (FePO4), and it also contains impurities such as graphite and lithium salts. Its composition is complex and its physical and chemical properties vary greatly, which makes it difficult to recycle ferrophosphorus slag. The iron phosphate in ferrophosphorus slag is closely combined with the mineral form of iron, and most of the ferrophosphate slag contains high moisture and insoluble matter, which makes it difficult to efficiently separate valuable elements such as phosphorus and iron by conventional physical or chemical recovery methods.

[0004] At present, the recovery methods of ferrophosphorus slag mainly include several routes such as hydrometallurgy, pyrometallurgy and integrated recovery, but these methods still have problems to varying degrees. Hydrometallurgy (such as acid leaching, solvent extraction, etc.) is often used to recover elements such as phosphorus and iron from ferrophosphorus slag, but due to the complex reaction process and the need to consume a large amount of acid and solvent, the cost is high, and the wastewater treatment after pickling is difficult. Although pyrometallurgy (such as high-temperature roasting) can effectively decompose iron phosphate, it requires high-temperature operation, which not only consumes a lot of energy, but also may produce a large amount of harmful gases, causing serious pollution. Some companies try to use integrated recovery technology to directly convert ferrophosphorus slag into lithium iron phosphate materials without going through the intermediate products of lithium carbonate and iron phosphate. For example, some companies have successfully developed a linear recovery process from lithium iron phosphate waste to lithium iron phosphate materials. This process can significantly improve resource utilization and avoid the problem of intermediate product treatment. However, this technology is still in the exploratory stage, and there are problems such as unstable process and low product purity.

[0005] Patent CN117154273A proposes a method for recycling waste lithium-ion battery positive electrode materials, especially "high-aluminum and high-iron mixed black powder", which covers multiple steps such as auxiliary agent roasting, two-stage leaching, phosphate precipitation, coprecipitation and phosphoric acid regeneration. By using calcium salt roasting and phosphoric acid to control pH, efficient recovery and recycling of valuable metals such as lithium, iron, aluminum, nickel, cobalt, manganese and phosphorus are achieved, solving the problem of traditional technology for the treatment of mixed positive electrode materials and aluminum residues. However, the process involves by-products generated by multiple chemical reactions (such as CaSO4, aluminate in waste liquid, etc.), and it is not clear whether it is equally efficient for other types of battery positive electrode materials (such as ternary materials or positive electrode materials with different doping systems). The adaptability of this technology may be limited, and additional adjustment of process conditions is required.

[0006] Patent CN202211198739.9 heat-treats ferrophosphorus slag with carbon and potassium-containing inorganic compounds, uses potassium to promote the reduction of iron ions to iron, and generates phosphorus-potassium compounds to recover phosphorus; then separates and extracts iron and phosphorus through solid-liquid separation and concentration. However, the heat treatment of this process needs to be carried out in an inert atmosphere, which places high demands on the sealing and atmosphere control of the equipment, and may increase initial investment and maintenance costs. High-temperature heat treatment and subsequent concentration and evaporation processes may produce gas emissions or concentrated waste liquid, causing unnecessary environmental problems.

[0007] Patent CN118026126A uses acid to leach iron phosphate, adjust the iron-phosphorus ratio, add ammonia water to precipitate, convert to generate an intermediate product containing ammonium iron phosphate and roast it, and finally prepare iron phosphate with controllable specific surface area. The key is to achieve effective control of the specific surface area of ​​iron phosphate by regulating the precipitation stage with ammonium salt, so as to meet the controlled synthesis of different waste lithium iron phosphate batteries. However, this technology has high requirements on the iron-phosphorus ratio and impurity content of waste iron phosphate slag. If the raw material composition fluctuates greatly, it is easy to affect the quality of the final iron phosphate product and the controllability of the specific surface.

[0008] Patent CN202011259874.0 recovers phosphorus, iron and lithium from waste lithium iron phosphate batteries, including removing impurities in the battery by soaking in an organic solvent, removing aluminum with a sodium hydroxide solution, leaching iron and phosphorus with an acidic solution, and reacting with sulfuric acid and hydrogen peroxide to finally obtain high-purity iron phosphate and lithium carbonate products. This process can efficiently recover phosphorus, iron and lithium elements from waste batteries, and ensure the stable quality of the final product, meeting the requirements of battery-grade iron phosphate and lithium carbonate. This method uses high-concentration acid solutions, sodium hydroxide solutions and other chemical reagents many times, and requires high-temperature heating and long-term soaking. Although the patent mentions that the generation of iron-containing waste slag and phosphorus-containing wastewater is avoided, the treatment process of other by-products and wastes is not described in detail.

[0009] Patent CN202380011397.1 proposes to remove carbon impurities from recovered ferrophosphorus slag and prepare high-purity ferric phosphate, by setting a magnetic field in the ferrophosphorus slag dispersion, using the magnetic field to adsorb ferric phosphate, increasing the difference in floatability between ferric phosphate and carbon particles, and promoting preliminary separation. Subsequently, the carbon particles are oxidized and activated by a strong oxidizing agent, and the carbon particles and ferrophosphorus slag are further separated by the synergistic effect of aromatic ethers, inhibitors and collectors. Ultimately, through this series of treatments, the purity of ferric phosphate is significantly improved, and the problem of high impurity content when ferrophosphorus slag is used to prepare ferric phosphate during the recycling of waste batteries is solved. However, the patent involves multi-step processes such as magnetic field separation, oxidation activation by strong oxidizing agents, and the synergistic effect of aromatic ethers and inhibitors. Aromatic ethers, collectors, etc. may remain in the separated product. In practical applications, the process may need to be further optimized to solve problems such as cost, environmental impact and universality.

[0010] In summary, the current recycling process of ferrophosphorus slag is still immature, the overall level of resource utilization is low, and its economic efficiency and large-scale application still face many challenges.

[0011] Therefore, how to find a new method for recycling ferrophosphorus slag so that phosphorus, iron and sulfur elements can be recycled efficiently and achieve high value-added resources is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0012] In view of this, the object of the present invention is to provide a method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer, so as to solve the problems of low recovery efficiency of phosphorus, iron and sulfur elements and poor resource utilization in the ferrophosphorus slag which is difficult to handle in the recycling process of lithium iron phosphate batteries in the prior art.

[0013] In order to achieve the above object, the present invention adopts the following technical solution:

[0014] A method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer specifically comprises the following steps:

[0015] (1) drying, grinding, and screening the ferrophosphorus slag after lithium extraction to obtain ferrophosphorus slag particles;

[0016] (2) mixing the ferrophosphorus slag particles with the ammonium sulfide solution, reacting them by a wet process, and separating them to obtain an ammonium phosphate solution, a ferrous sulfide solid, and an elemental sulfur solid, respectively;

[0017] (3) vacuum evaporation and concentration of the ammonium phosphate solution, cooling and crystallization, and drying to obtain ammonium phosphate fertilizer;

[0018] (4) drying, calcining and purifying the ferrous sulfide solid to obtain iron powder;

[0019] (5) Recycling elemental sulfur solids.

[0020] Furthermore, in the above step (1), the drying equipment is a drying oven, the temperature is 100-150° C., the time is 4-6 hours, and the drying is performed until the moisture content of the material is below 3%.

[0021] A further beneficial effect of the above method is that free water and bound water in the ferrophosphorus slag are removed by drying, which is beneficial to subsequent grinding and wet reaction.

[0022] Furthermore, in the above step (1), the grinding method is ball mill grinding; the screening method is vibration screening, and the material is screened to a particle size of ≤8 mm.

[0023] A further beneficial effect of the above method is that, through grinding and screening, the specific surface area of ​​the material can be increased, thereby ensuring uniform contact and reaction efficiency of the subsequent wet reaction.

[0024] Furthermore, in the above step (2), the mass concentration of the ammonium sulfide solution is 10% to 15%; the mass ratio of the ferrophosphorus slag particles to the ammonium sulfide solution is 1:(3 to 8);

[0025] Furthermore, in the above step (2), the wet reaction equipment is a closed reactor, the reaction temperature is 60 to 80° C., and the stirring reaction time is 1 to 3 hours.

[0026] A further beneficial effect of the above method is that the wet reaction generates ammonium phosphate solution and ferrous sulfide solid by reacting the ferric phosphate in the ferrophosphorus slag with ammonium sulfide. The reaction equation is as follows:

[0027] 6(NH4)2S+4FePO4=4FeS↓+4(NH4)3PO4+2S↓

[0028] Among them, ferrous sulfide (FeS) generated by the reaction settles to the bottom as an iron element recovery product, and ammonium phosphate ((NH4)3PO4) dissolves in the upper reaction liquid to form a phosphate fertilizer raw material solution, realizing efficient separation and resource recovery of iron, phosphorus and sulfur.

[0029] Furthermore, in the above step (2), the separation method is sedimentation or filtration.

[0030] A further beneficial effect of adopting the above method is that the ammonium phosphate solution is separated from the ferrous sulfide solid by sedimentation or filtration, and the ammonium phosphate solution is further concentrated and crystallized to form ammonium phosphate fertilizer.

[0031] Furthermore, in the above step (3), the equipment for vacuum evaporation and concentration is a vacuum evaporation device, the vacuum degree is 0.05-0.1 MPa, the evaporation temperature is 50-70° C., the concentration multiple is 3-3.5 times, and the ammonium phosphate solution is concentrated to saturation.

[0032] A further beneficial effect of the above method is that, after the ammonium phosphate solution is concentrated and crystallized, the purity of the ammonium phosphate fertilizer reaches more than 98%, the phosphorus recovery rate is more than 97%, and the obtained ammonium phosphate fertilizer is suitable for agricultural crops.

[0033] Furthermore, in the above step (4), the high temperature calcination equipment is a high temperature reduction calcination furnace, the reducing atmosphere is a CO / N2 mixed gas, the heating rate is 10-15°C / min, the insulation temperature is 800-1000°C, and the insulation time is 30-90min.

[0034] A further beneficial effect of the above method is that, under a reducing atmosphere, ferrous sulfide is converted into metallic iron powder, thereby realizing the recovery and reuse of iron resources. The reaction equation is as follows:

[0035] CO+FeS→Fe+COS

[0036] Furthermore, in the above step (4), the high temperature calcination equipment is a fluidized bed calcination device, the reducing atmosphere is a H2 / N2 mixed gas, the insulation temperature is 800-1000°C, and the insulation time is 30-90 minutes.

[0037] Furthermore, in the above step (4), the purification method is magnetic separation.

[0038] A further beneficial effect of the above method is that the iron powder is further purified by magnetic separation or other physical methods to remove impurities and obtain high-purity iron powder. The purity of the iron powder reaches more than 98%, and the recovery rate of iron element is more than 94%.

[0039] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] 1. The present invention uses the ferrophosphorus slag generated in the process of lithium iron phosphate battery recycling as raw material, and separates and recovers the phosphorus, iron and sulfur elements therein through processes such as drying, grinding, screening and wet reaction, so as to realize resource utilization. First, the ferrophosphorus slag is dried, ground and screened, and then reacted with ammonium sulfide solution to separate ammonium phosphate solution, ferrous sulfide solid and elemental sulfur solid; the ammonium phosphate solution is concentrated and crystallized to prepare high-purity ammonium phosphate fertilizer, and the phosphorus recovery rate is as high as 97% or more. Secondly, the ferrous sulfide solid is reduced and roasted at high temperature to prepare high-purity iron powder, and the iron recovery rate can reach more than 94%. Finally, the elemental sulfur is recycled as a by-product, and further refined as a raw material for industrial sulfide or agricultural sulfur fertilizer, reducing solid waste emissions. The present invention realizes the efficient separation and cascade recovery of phosphorus, iron and sulfur elements in ferrophosphorus slag, and co-produces high-value-added ammonium phosphate fertilizer. The process flow is simple, economical and environmentally friendly, suitable for industrial promotion, and is of great significance to promoting the recycling of resources in the lithium iron phosphate battery recycling industry.

[0041] 2. The present invention realizes the effective recovery of phosphorus, iron and sulfur elements in ferrophosphorus slag through a method combining wet reaction separation with resource utilization, and co-produces ammonium phosphate fertilizer for resource utilization. The process is short, the resource utilization rate is high, and it has both economic benefits and environmental friendliness.

[0042] 3. Through the present invention, phosphorus and iron elements in ferrophosphorus slag are efficiently recovered, the produced ammonium phosphate fertilizer can be used in the agricultural field, and iron resources are recycled in the form of iron powder, thereby achieving maximum utilization of resources and effective control of environmental pollution. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example 1

[0045] The method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer specifically comprises the following steps:

[0046] (1) placing the ferrophosphorus slag after lithium extraction in a drying oven, drying at 120° C. for 6 h until the moisture content of the material is less than 3%, then grinding it with a ball mill, and finally sieving it with a vibration screening device until the material particle size is 8 mm, thereby obtaining ferrophosphorus slag particles;

[0047] (2) firstly mixing the ferrophosphorus slag particles with a 10% ammonium sulfide solution at a mass ratio of 1:3, then placing the mixture in a closed reactor, stirring and reacting at 60° C. for 2 h, and finally settling and separating to obtain an ammonium phosphate solution, ferrous sulfide solid, and elemental sulfur solid, respectively;

[0048] (3) placing the ammonium phosphate solution in a vacuum evaporation device, concentrating the solution to saturation by vacuum evaporation at 0.05 MPa and 50° C., controlling the concentration multiple to 3 times, then cooling the solution to room temperature for crystallization, and drying the solution to obtain an ammonium phosphate fertilizer;

[0049] (4) first drying the ferrous sulfide solid, then placing it in a high-temperature reduction roasting furnace, introducing a CO / N2 mixed gas, heating the temperature from room temperature to 900°C at a heating rate of 15°C / min and keeping the temperature for 60 minutes for high-temperature roasting, and then purifying it by magnetic separation to obtain iron powder;

[0050] (5) Recycling elemental sulfur solids.

[0051] Example 2

[0052] The method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer specifically comprises the following steps:

[0053] (1) placing the ferrophosphorus slag after lithium extraction in a drying oven, drying at 150° C. for 5 h until the moisture content of the material is less than 2%, then grinding it with a ball mill, and finally sieving it with a vibration screening device until the material particle size is 5 mm, thereby obtaining ferrophosphorus slag particles;

[0054] (2) firstly mixing the ferrophosphorus slag particles with a 10% ammonium sulfide solution at a mass ratio of 1:4, then placing the mixture in a closed reactor, stirring and reacting at 70° C. for 3 h, and finally settling and separating to obtain an ammonium phosphate solution, ferrous sulfide solid, and elemental sulfur solid, respectively;

[0055] (3) placing the ammonium phosphate solution in a vacuum evaporation device, concentrating the solution to saturation by vacuum evaporation at 0.08 MPa and 60° C., controlling the concentration multiple to be 3.5 times, then cooling the solution to room temperature for crystallization, and drying the solution to obtain an ammonium phosphate fertilizer;

[0056] (4) first drying the ferrous sulfide solid, then placing it in a high-temperature reduction roasting furnace, introducing a CO / N2 mixed gas, heating the temperature from room temperature to 950°C at a heating rate of 10°C / min and keeping the temperature for 90 minutes for high-temperature roasting, and then purifying it by magnetic separation to obtain iron powder;

[0057] (5) Recycling elemental sulfur solids.

[0058] Example 3

[0059] The method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer specifically comprises the following steps:

[0060] (1) placing the ferrophosphorus slag after lithium extraction in a drying oven, drying at 130° C. for 4 hours until the moisture content of the material is less than 3%, then grinding it with a ball mill, and finally sieving it with a vibration screening device until the material particle size is 3 to 5 mm, thereby obtaining ferrophosphorus slag particles;

[0061] (2) firstly mixing the ferrophosphorus slag particles with an ammonium sulfide solution having a mass concentration of 15% at a mass ratio of 1:3.5, then placing the mixture in a closed reactor, stirring the mixture for reaction at 60 to 80° C. for 1 to 3 hours, and finally settling or filtering the mixture to obtain an ammonium phosphate solution, a ferrous sulfide solid, and an elemental sulfur solid, respectively;

[0062] (3) placing the ammonium phosphate solution in a vacuum evaporation device, concentrating the solution to saturation by vacuum evaporation at 0.08 MPa and 55° C., controlling the concentration multiple to 3 times, then cooling the solution to room temperature for crystallization, and drying the solution to obtain an ammonium phosphate fertilizer;

[0063] (4) first drying the ferrous sulfide solid, then placing it in a fluidized bed roasting device, introducing a H2 / N2 mixed gas, heating it from room temperature to 1000°C at a heating rate of 15°C / min and keeping it at that temperature for 80 minutes for high temperature roasting, and then purifying it by magnetic separation to obtain iron powder;

[0064] (5) Recycling elemental sulfur solids.

[0065] Performance Testing

[0066] Using ferrophosphorus slag produced during the treatment process of a domestic lithium iron phosphate battery recycling plant as raw material, phosphorus, iron and sulfur elements were recovered and ammonium phosphate fertilizer was co-produced according to the methods of Examples 1-3.

[0067] The main components and contents (mass fractions) of the ferrophosphorus slags in Examples 1-3 were determined respectively, and the purity of ammonium phosphate fertilizer, phosphorus recovery rate, iron powder purity and iron recovery rate were calculated. The results are shown in Table 1.

[0068] Table 1 Performance test results of recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer in Example 1-3

[0069]

[0070] As can be seen from Table 1, in Examples 1-3, the purity of ammonium phosphate fertilizer, phosphorus recovery rate, iron powder purity and iron recovery rate are all at a relatively high level.

[0071] The above experiments show that the present invention realizes the efficient separation and cascade recovery of phosphorus, iron and sulfur elements in ferrophosphorus slag, and co-produces high value-added ammonium phosphate fertilizer. The process flow is simple, economical and environmentally friendly, suitable for industrial promotion, and is of great significance to promoting the recycling of resources in the lithium iron phosphate battery recycling industry.

[0072] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for recovering phosphorus, iron and sulfur from ferrophosphorus slag and co-producing ammonium phosphate fertilizer, characterized in that: The specific steps include: (1) drying, grinding, and screening the ferrophosphorus slag after lithium extraction to obtain ferrophosphorus slag particles; (2) mixing the ferrophosphorus slag particles with the ammonium sulfide solution, reacting them by a wet process, and separating them to obtain an ammonium phosphate solution, a ferrous sulfide solid, and an elemental sulfur solid, respectively; (3) vacuum evaporation and concentration of the ammonium phosphate solution, cooling and crystallization, and drying to obtain ammonium phosphate fertilizer; (4) drying, calcining and purifying the ferrous sulfide solid to obtain iron powder; (5) Recycling the elemental sulfur solid.

2. The method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer according to claim 1, characterized in that: In step (1), the drying equipment is a drying oven, the temperature is 100-150° C., the time is 4-6 hours, and the drying is performed until the moisture content of the material is below 3%.

3. The method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer according to claim 1, characterized in that: In step (1), the grinding method is ball mill grinding; the screening method is vibration screening, and the material is screened to a particle size of ≤8 mm.

4. The method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer according to claim 1, characterized in that: In step (2), the mass concentration of the ammonium sulfide solution is 10% to 15%; the mass ratio of the ferrophosphorus slag particles to the ammonium sulfide solution is 1:(3 to 8).

5. The method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer according to claim 1, characterized in that: In step (2), the wet reaction equipment is a closed reactor, the reaction temperature is 60-80° C., and the stirring reaction time is 1-3 h.

6. The method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer according to claim 1, characterized in that: In step (2), the separation method is sedimentation or filtration.

7. The method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer according to claim 1, characterized in that: In step (3), the vacuum evaporation and concentration equipment is a vacuum evaporation device with a vacuum degree of 0.05-0.1 MPa, an evaporation temperature of 50-70° C., a concentration multiple of 3-3.5 times, and the ammonium phosphate solution is concentrated to saturation.

8. The method for recovering phosphorus, iron and sulfur from ferrophosphorus slag and co-producing ammonium phosphate fertilizer according to claim 1, characterized in that: In step (4), the high-temperature calcination equipment is a high-temperature reduction calcination furnace, the reducing atmosphere is a CO / N2 mixed gas, the heating rate is 10-15°C / min, the insulation temperature is 800-1000°C, and the insulation time is 30-90min.

9. The method for recovering phosphorus, iron and sulfur elements from ferrophosphorus slag and co-producing ammonium phosphate fertilizer according to claim 1, characterized in that: In step (4), the high-temperature calcination equipment is a fluidized bed calcination device, the reducing atmosphere is a H2 / N2 mixed gas, the insulation temperature is 800-1000°C, and the insulation time is 30-90 minutes.

10. The method for recovering phosphorus, iron and sulfur from ferrophosphorus slag and co-producing ammonium phosphate fertilizer according to claim 1, characterized in that: In step (4), the purification method is magnetic separation.

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