Method for smelting yellow phosphorus and alloy by using high-magnesium low-grade phosphorite

Abstract

The invention discloses a method for smelting yellow phosphorus and alloy by using high-magnesium low-grade phosphorite, which comprises the following steps of: proportioning the high-magnesium low-grade phosphorite, a calcium flux, a siliceous flux, iron ore and a carbonaceous reducing agent, and carrying out reduction smelting treatment, so that part of apatite is reduced to generate yellow phosphorus steam, and part of phosphorus steam and reduced iron are chemically combined to form the alloy; calcium oxide, magnesium oxide, silicon oxide and aluminum oxide form low-melting-point smelting slag, and activated slag is obtained through water quenching. The method can provide technical reference for efficient resource utilization of low-grade phosphorite, especially high-magnesium and high-iron type low-grade phosphorite, three products of high-quality yellow phosphorus, high-added-value ferrophosphorus and activated smelting slag are obtained at the same time, and no new solid waste is generated in the process.

Description

Technical Field

[0001] The invention belongs to the field of phosphorus chemical industry, and particularly relates to a method for smelting yellow phosphorus and alloys by utilizing high-magnesium low-grade phosphate ore. Background Art

[0002] Thermal H3PO4 production technology mainly involves blast furnace and electric furnace smelting, and electric furnace smelting is the current mainstream. In the reduction smelting process, phosphate rock, silica and coke are furnace charges, and three products are produced: yellow phosphorus, Fe-P alloy and slag. Yellow phosphorus produces high-concentration H3PO4 through oxidation and hydrolysis. At the same time, for every ton of yellow phosphorus produced, about 100-200kg of Fe-P alloy can be produced, and its output varies with the change of hematite concentration in phosphate rock. Fe-P alloy is mainly used as a key alloying agent and deoxidizer for special steel, and is also widely used as an alloy additive in cast iron production, aluminum alloys and copper-based alloys. In recent years, Fe-P alloys have also appeared in the field of new materials. Studies have shown that Fe-P alloy aggregates have a beneficial effect on the physical and mechanical properties of heavy concrete. Some people have tried to use Fe-P alloys to prepare advanced energy materials, such as Fe x P, FePO₄, and LiFePO₄. Transition metal phosphides can also be used as viable alternatives to precious metal co-catalysts in the hydrogen evolution reaction. Therefore, Fe-P alloys have broad application prospects, and optimizing the reduction smelting of phosphate rock to produce Fe-P alloys is of great significance to the sustainable development of the phosphorus industry.

[0003] Phosphate rock and hematite are the primary phases in the charge for yellow phosphorus and Fe-P alloy production, typically containing 20-30% P₂O₅ and 1-3% Fe₂O₃. During the reduction process, the reduction temperature and atmosphere vary, necessitating consideration of the interactions between intermediate products. Numerous attempts have been made to investigate the reduction smelting of phosphate rock, but few studies have focused on the effects of hematite on the reduction of high-phosphorus, low-iron phosphate rock. Furthermore, as a typical high-iron, low-phosphorus ore with an iron content of 35-50% and a P₂O₅ content of 0.23-3.43%, the reduction behavior of high-phosphorus hematite for phosphorus and iron separation in steelmaking has been extensively studied using methods such as magnetic reduction roasting, direct reduction roasting, and reduction smelting. Several dephosphorization agents have also been used to enhance iron and phosphorus separation, with most studies conducted at temperatures below 1300°C. As phosphate rock and hematite are reduced at high temperatures, extensive reduction, volatilization, and alloying reactions occur among the oxides, solid and molten metals, and phosphorus vapor in the multiphase system. Therefore, revealing the interfacial reduction behavior of phosphate rock and hematite at high temperature has important scientific value for elucidating the high-phosphorus, low-iron oxide system.

[0004] On the other hand, in industrial practice, the production of Fe-P alloys is intermittently adjusted based on market demand. Due to the high demand for yellow phosphorus, reducing the iron content of the furnace charge can increase yellow phosphorus production. Once the price of Fe-P alloys increases, scrap steel or hematite is added to the furnace to increase Fe-P alloy production. However, there is no way to predict the product ratio between yellow phosphorus and Fe-P alloys, nor the alloy composition during the smelting process. Therefore, greater attention should be paid to the regulatory mechanisms of volatilization and alloying to promote the efficient production of Fe-P alloys from phosphate rock and hematite. Summary of the Invention

[0005] In view of the above problems, the present invention aims to provide a method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A method for smelting yellow phosphorus and alloys using high-magnesium, low-grade phosphate rock comprises mixing high-magnesium, low-grade phosphate rock powder, a calcareous flux, a siliceous flux, iron ore, and a carbonaceous reducing agent, followed by reduction smelting to produce yellow phosphorus vapor, an alloy, and slag. The mixture, based on the total weight of the mixture, comprises: a SiO2 / (CaO+MgO) mass ratio of 0.65-0.95, a MgO mass percentage of 1-10%, a SiO2 mass percentage of 20-32%, and a Fe2O3 mass percentage of 5-20%. The reduction smelting process comprises heating from room temperature at 5-15°C / min to 950-1250°C, holding for 20-60 minutes, then heating at 10-50°C / min to 1350-1480°C, and holding for 60-120 minutes.

[0007] The method of smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate rock of the present invention comprises the following steps: the mass percentage of phosphorus pentoxide in the high-magnesium low-grade phosphate rock is 5% to 23%, and the mass percentage of magnesium oxide is 1% to 25%; and the particle size of the high-magnesium low-grade phosphate rock powder is not greater than 5 mm.

[0008] In the method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore described in the present invention, the calcareous flux is limestone, wherein the CaO content is not less than 50%; and the siliceous flux is silica, wherein the SiO2 content is not less than 98%.

[0009] In the method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore of the present invention, the iron ore is one or more of hematite, magnetite, and high-phosphorus hematite.

[0010] In the method of smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore described in the present invention, the carbonaceous reducing agent is coke, and its fixed carbon content is not less than 82wt%; the mass of the reducing agent accounts for 8-15% of the total mass of the ingredients; and the particle size of the reducing agent is not greater than 8mm.

[0011] In the method of smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore of the present invention, the particle size of the limestone and silica satisfies that the mass percentage of the particle size less than 100 mesh is not less than 99%.

[0012] The method of smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore of the present invention comprises the following steps: absorbing yellow phosphorus vapor with water to obtain high-quality phosphoric acid; and quenching the smelting slag and alloy mixture with water and physically separating the mixture to obtain an active slag product and a ferrophosphorus alloy product.

[0013] In the method of smelting yellow phosphorus and alloy using high-magnesium low-grade phosphate ore of the present invention, the particle size of the alloy product is not less than 10 mm.

[0014] The technical solution of the present invention is aimed at the characteristics of high-magnesium low-grade phosphate ore with high magnesium oxide, silicon oxide and iron oxide content. Conventional high-grade phosphate ore pyrometallurgical smelting process system has difficulty in slag formation when processing high-magnesium low-grade phosphate ore, low phosphorus reduction and escape efficiency, and poor alloy separation effect. The technical solution of the present invention is to add appropriate amounts of calcium flux and silicon flux to achieve the chemical composition of the ore blending raw materials meeting the following conditions: SiO2 / (CaO+MgO) mass ratio is 0.65~0.95, the mass percentage of MgO is 1~10%, the mass percentage of SiO2 is 15~32%, and the mass percentage of Fe2O3 is 5~20%. As a result, the smelting process of high-magnesium low-grade phosphate ore mainly uses enstatite as the main phase, and the melting range is higher than 1450℃; through ore blending, the enstatite phase is transformed into diopside, the melting temperature is reduced by more than 50℃, and the viscosity of the slag is reduced. The technical solution of the present invention enables slag formation at relatively low temperatures, promoting metal aggregation and growth to form large particles or even massive alloys, thereby improving the separation efficiency of the alloy and slag phase. Furthermore, the technical solution of the present invention can also activate smelting slag to meet the requirements of using the smelting slag as a trace element soil conditioner in the next step. Through the batching, smelting, and water quenching technical solutions, the present invention can produce three high-value-added products without generating new solid waste, achieving full quantification and resource utilization of high-magnesium low-grade phosphate rock. DETAILED DESCRIPTION

[0015] The following examples are intended to further illustrate the present invention, but are not intended to limit the scope of protection of the present invention.

[0016] A method for smelting yellow phosphorus and alloys using high-magnesium, low-grade phosphate rock comprises mixing high-magnesium, low-grade phosphate rock powder, calcareous flux, siliceous flux, iron ore, and a carbonaceous reducing agent, followed by reduction smelting to produce yellow phosphorus vapor, alloy, and slag. The high-magnesium, low-grade phosphate rock, calcareous flux, siliceous flux, and reducing agent are prepared such that the SiO2 / (CaO+MgO) mass ratio is 0.65-0.95, the mass percentage of MgO is 1-10%, the mass percentage of SiO2 is 20-32%, and the mass percentage of Fe2O3 is 5-20%. The reduction smelting process comprises heating from room temperature at 5-15°C / min to 950-1250°C, holding for 20-60 minutes, then heating at 10-50°C / min to 1350-1480°C, and holding for 60-120 minutes.

[0017] The method of smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate rock of the present invention comprises the following steps: the mass percentage of phosphorus pentoxide in the high-magnesium low-grade phosphate rock is 5% to 23%, and the mass percentage of magnesium oxide is 1% to 25%; and the particle size of the high-magnesium low-grade phosphate rock powder is not greater than 5 mm.

[0018] In the method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore of the present invention, the iron ore is one or more of hematite, magnetite, and high-phosphorus hematite.

[0019] In the method of smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore described in the present invention, the carbonaceous reducing agent is coke, and its fixed carbon content is not less than 82%; the mass of the reducing agent accounts for 8-15% of the total mass of the ingredients; and the particle size of the reducing agent is not greater than 8 mm.

[0020] In the method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore, the calcareous flux is limestone, wherein the CaO content is not less than 50%, and the siliceous flux is silica, wherein the SiO2 content is not less than 98%. The limestone and silica have a particle size of less than 100 mesh, and the mass percentage of the particle size is not less than 99%.

[0021] The method of smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore of the present invention comprises the following steps: absorbing yellow phosphorus vapor with water to obtain high-quality phosphoric acid; and quenching the smelting slag and alloy mixture with water and physically separating the mixture to obtain an active slag product and a ferrophosphorus alloy product.

[0022] In the method of smelting yellow phosphorus and alloy using high-magnesium low-grade phosphate ore of the present invention, the particle size of the alloy product is not less than 10 mm.

[0023] Example 1 A method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore, the process is as follows: The invention uses high-magnesium, low-grade phosphate rock with a P2O5 content of 18.7%, a MgO content of 19%, and a SiO2 content of 8% as raw materials, finely ground limestone and silica as fluxes, coke as a reducing agent, and hematite as the iron raw material for batching. The high-magnesium, low-grade phosphate rock powder has a particle size of less than 5 mm, the calcium oxide content of the limestone is 55%, the silicon dioxide content of the silica is 99%, and the particle size of the limestone and silica satisfies the requirement that the mass percentage of the particle size less than 100 mesh is 100%. The mass ratio of the coke is 12%, the fixed carbon content of the coke is 85 wt%, and the particle size of the coke is less than 6 mm. After the ingredients are mixed, the chemical composition of the resulting mixture satisfies the following requirements: a SiO2 / (CaO+MgO) mass ratio of 0.95, a MgO mass percentage of 6%, a SiO2 mass percentage of 20%, and a Fe2O3 mass percentage of 10%. The mixture was reduced in a roasting furnace. The reduction procedure was to increase the temperature to 1250°C at a rate of 15°C / min, hold for 60 minutes, then increase the temperature to 1350°C at a rate of 40°C / min and hold for 120 minutes. Water was used to absorb the yellow phosphorus in the furnace gas during the reduction process. After the reduction, the smelting slag was quenched, ground, and screened. The oversize fraction was the alloy product, and the undersize fraction was the activated slag product. Laboratory analysis revealed a phosphorus release rate of 72%, a phosphorus alloying rate of 26%, an alloy particle size greater than 12 mm, an iron alloying rate of 99%, and a phosphorus recovery rate of 98%.

[0024] Example 2 A method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore, the process is as follows: The invention uses high-magnesium, low-grade phosphate rock with a P2O5 content of 15.3%, a MgO content of 23%, and a SiO2 content of 12% as raw materials, finely ground limestone and silica as fluxes, coke as a reducing agent, and high-phosphorus iron ore as the iron raw material for batching. The high-magnesium, low-grade phosphate rock powder has a particle size of less than 4 mm, the calcium oxide content of the limestone is 58%, the silicon dioxide content of the silica is 98.5%, and the particle size of the limestone and silica satisfies the requirement that the mass percentage of the particle size less than 100 mesh is 100%. The mass ratio of the coke is 13%, the fixed carbon content of the coke is 82 wt%, and the particle size of the coke is less than 8 mm. After mixing the ingredients, the chemical composition of the resulting mixture satisfies the following requirements: a SiO2 / (CaO+MgO) mass ratio of 0.65, an MgO mass percentage of 8%, an SiO2 mass percentage of 22%, and an Fe2O3 mass percentage of 12%. The mixture was reduced in a roasting furnace. The reduction procedure was to increase the temperature to 1200°C at a rate of 10°C / min, hold for 60 minutes, then increase the temperature to 1480°C at a rate of 50°C / min and hold for 120 minutes. Water was used to absorb the yellow phosphorus in the furnace gas during the reduction process. After the reduction, the smelting slag was quenched, ground, and screened. The oversize fraction was the alloy product, and the undersize fraction was the activated slag product. Laboratory analysis revealed a phosphorus release rate of 68%, a phosphorus alloying rate of 25%, an alloy particle size greater than 15 mm, an iron alloying rate of 98%, and a phosphorus recovery rate of 93%.

[0025] Comparative Example 1 The SiO2 / (CaO+MgO) mass ratio is not within the scope of the present invention. The invention uses high-magnesium low-grade phosphate rock with a P2O5 content of 20.9%, a MgO content of 21%, and a SiO2 content of 19% as raw materials, finely ground limestone and silica as fluxes, coke as a reducing agent, and high-phosphorus iron ore as the iron raw material for batching. The high-magnesium low-grade phosphate rock powder has a particle size of less than 5 mm, the calcium oxide content in the limestone is 54%, the silicon dioxide content in the silica is 99%, and the particle size of the limestone and silica satisfies the mass percentage of the particle size less than 100 mesh, the mass ratio of the coke is 15%, the fixed carbon content of the coke is 83wt%, and the particle size of the coke is less than 8 mm. After the ingredients are mixed, the chemical composition of the resulting mixture satisfies the following requirements: SiO2 / (CaO+MgO) mass ratio of 0.4, the mass percentage of MgO of 7%, the mass percentage of SiO2 of 15%, and the mass percentage of Fe2O3 of 10%. The mixture was reduced in a roasting furnace. The reduction procedure was to increase the temperature to 1180°C at a rate of 20°C / min, hold for 60 minutes, then increase the temperature to 1400°C at a rate of 35°C / min and hold for 120 minutes. Water was used to absorb the yellow phosphorus in the furnace gas during the reduction process. After the reduction, the smelting slag was quenched, ground, and screened. The oversize fraction was the alloy product, and the undersize fraction was the activated slag product. Laboratory analysis revealed a phosphorus release rate of 60%, a phosphorus alloying rate of 16%, an alloy particle size of less than 5 mm, an iron alloying rate of 95%, and a phosphorus recovery rate of only 76%.

[0026] Comparative Example 2 The reduction temperature is not within the scope of the present invention. The invention uses high-magnesium low-grade phosphate rock with a P2O5 content of 22.5%, a MgO content of 18%, and a SiO2 content of 20% as raw materials, finely ground limestone and silica as fluxes, coke as a reducing agent, and high-phosphorus iron ore as the iron raw material for batching. The high-magnesium low-grade phosphate rock powder has a particle size of less than 4.5 mm, the calcium oxide content in the limestone is 57%, the silicon dioxide content in the silica is 99.5%, and the particle size of the limestone and silica satisfies the mass percentage of the particle size less than 100 mesh. The mass ratio of the coke is 14%, the fixed carbon content of the coke is 85wt%, and the particle size of the coke is less than 8 mm. After the ingredients are mixed, the chemical composition of the resulting mixture satisfies the following requirements: SiO2 / (CaO+MgO) mass ratio of 0.85, the mass percentage of MgO of 8%, the mass percentage of SiO2 of 25%, and the mass percentage of Fe2O3 of 15%. The mixture was reduced in a roasting furnace. The reduction procedure was to heat the material to 1225°C at a rate of 20°C / min, hold the temperature for 60 minutes, then heat the material to 1650°C at a rate of 35°C / min and hold the temperature for 120 minutes. Water was used to absorb the yellow phosphorus in the furnace gas during the reduction process. After the reduction, the smelting slag was quenched, ground, and screened. The oversize fraction was the alloy product, and the undersize fraction was the activated slag product. Laboratory analysis revealed a phosphorus release rate of 78%, a phosphorus alloying rate of only 15% (due to high-temperature decomposition of the alloy), an alloy particle size greater than 16 mm, an iron alloying rate of 97%, and a phosphorus recovery rate of 93%.

[0027] Although preferred embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work shall fall within the scope of protection of the present invention.

Claims

1. A method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore, characterized in that: High-magnesium low-grade phosphate rock powder, calcium flux, silicon flux, iron ore, and carbonaceous reducing agent are mixed and subjected to reduction smelting to obtain yellow phosphorus vapor, alloy, and slag; The ingredients of high-magnesium low-grade phosphate rock, calcareous flux, siliceous flux, reducing agent, and iron ore shall meet the following requirements: SiO2 / (CaO+MgO) mass ratio is 0.65-0.95, the mass percentage of MgO is 1-10%, the mass percentage of SiO2 is 15-32%, and the mass percentage of Fe2O3 is 5-20%. The reduction smelting process is as follows: heating from room temperature to 950-1250° C. at a rate of 5-15° C. / min, keeping the temperature for 20-60 minutes, then heating to 1350-1480° C. at a rate of 10-50° C. / min, and keeping the temperature for 60-120 minutes.

2. The method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore according to claim 1, characterized in that: The mass percentage of phosphorus pentoxide in the high-magnesium low-grade phosphate rock is 5% to 23%, and the mass percentage of magnesium oxide is 1% to 25%; the particle size of the high-magnesium low-grade phosphate rock powder is not greater than 5mm.

3. The method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore according to claim 1, characterized in that: The calcareous flux is limestone, wherein the CaO content is not less than 50%; the siliceous flux is silica, wherein the SiO2 content is not less than 98%.

4. The method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore according to claim 1, characterized in that: The iron ore is one or more of hematite, magnetite and high-phosphorus hematite.

5. The method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore according to claim 1, characterized in that: The carbonaceous reducing agent is coke, and its fixed carbon content is not less than 82wt%; the mass of the reducing agent accounts for 8-15% of the total mass of the ingredients; and the particle size of the reducing agent is not greater than 8mm.

6. The method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore according to claim 3, characterized in that: The particle size of the limestone and silica is such that the mass percentage of the particle size less than 100 mesh is not less than 99%.

7. The method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore according to claim 1, characterized in that: The yellow phosphorus vapor is absorbed by water to obtain high-quality phosphoric acid, and the smelting slag and alloy mixture are quenched with water and physically separated to obtain an active slag product and a phosphorus-iron alloy product.

8. The method for smelting yellow phosphorus and alloys using high-magnesium low-grade phosphate ore according to claim 1, characterized in that: The particle size of the alloy product is not less than 10 mm.