A method for producing yellow phosphorus

Abstract

The application discloses a preparation method of yellow phosphorus, which comprises the following steps: fully utilizing phosphate ore and phosphate-containing waste ore powder to produce artificial phosphate ore pellets which can be directly used for yellow phosphorus production, and further utilizing the artificial phosphate ore pellets and a shaft furnace in the steel industry to produce high-quality yellow phosphorus products. On one hand, the utilization efficiency of phosphorus resources is improved, and the production pressure of yellow phosphorus is relieved. On the other hand, a new utilization way is provided for the shaft furnace in the steel industry, waste is turned into treasure, and the waste of resources and equipment is reduced.

Description

Technical Field

[0001] This invention relates to the production process of yellow phosphorus, specifically to a method for preparing yellow phosphorus, and belongs to the field of yellow phosphorus production technology. Background Technology

[0002] my country's phosphate rock resources are mainly low- to medium-grade phosphate rock, with scarce rich ore resources. Phosphate rock is a non-renewable resource; due to its wide range of uses and relatively low output, and the lack of corresponding substitutes, it is a scarce resource. The scarcity and irreplaceability of phosphate rock resources determine that its valuation should be higher than other resources. With the increasing consumption of high-quality phosphate rock, the amount of high-quality phosphate rock available for yellow phosphorus production is also decreasing, leading to a growing shortage of natural phosphate rock resources and a rising market price. Solving the problem of ore supply for yellow phosphorus production is urgent and has become crucial to ensuring the normal production of yellow phosphorus enterprises.

[0003] During the mining and production of natural phosphate rock lumps, a large amount of waste phosphate rock powder is inevitably generated. This high-quality phosphate rock powder cannot be directly used for electric arc furnace phosphorus production, resulting in the idleness of high-quality phosphate rock resources and causing resource waste. On the other hand, this phosphate rock powder, which cannot be directly used for yellow phosphorus production, is stockpiled in large quantities in stockpiles, occupying a lot of space, wasting land resources, and easily causing environmental pollution. In addition, the domestic steel industry has overcapacity, and with increasingly stringent environmental protection requirements, the steel industry will gradually phase out existing vertical shaft furnaces in the sintering and pelletizing field. The direct dismantling of these vertical shaft furnaces will inevitably lead to the waste of resources and equipment. How to further utilize these phased-out vertical shaft furnaces has become a current technical challenge. Summary of the Invention

[0004] To address the problems in existing technologies, such as the inability of waste phosphate rock powder to be directly used in electric arc furnace phosphorus production, leading to the waste of phosphorus resources, and the waste of resources and equipment caused by the abandonment of existing vertical shaft furnaces in the steel industry, this invention provides a method for preparing yellow phosphorus. By fully utilizing raw phosphate ore and phosphorus-containing waste ore powder, artificial phosphate rock pellets that can be directly used for yellow phosphorus production are obtained. This method replaces electric arc furnaces with vertical shaft furnaces in the steel industry for yellow phosphorus production. On the one hand, it improves the efficiency of phosphorus resource utilization and alleviates the pressure on yellow phosphorus production; on the other hand, it provides a new utilization path for steel vertical shaft furnaces, turning waste into treasure and reducing the waste of resources and equipment.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing yellow phosphorus, the method comprising:

[0007] 1) Phosphate powder is obtained by mixing open-pit phosphate ore with deep-buried phosphate ore and pre-treating them.

[0008] 2) The phosphate rock powder, biomass straw pellets and quartz powder are mixed to obtain a mixture.

[0009] 3) According to the set pelleting index requirements, add rice slurry aqueous solution to the mixture for granulation. After granulation, add calcium hydroxide solution for pelletizing to obtain green phosphate rock pellets.

[0010] 4) Sinter the green phosphate rock pellets to obtain mature phosphate rock pellets.

[0011] 5) After mixing the phosphate rock pellets with coke, the mixture is fed into a vertical shaft furnace for reduction treatment. The phosphorus-containing flue gas discharged from the vertical shaft furnace is cooled with water, the precipitate is collected and dried to obtain yellow phosphorus.

[0012] Preferably, step 1) includes:

[0013] 101) After mixing open-pit phosphate ore and deep-buried phosphate ore, the raw ore is successively refined, washed, dried and screened to obtain raw ore blocks, large-particle raw ore and fine-particle raw ore.

[0014] 102) The large-particle raw ore is ground and classified to obtain raw ore coarse powder, raw ore fine powder and raw ore micro powder.

[0015] 103) After the fine ore powder is subjected to flotation, magnetic separation, photoelectric separation and calcination in sequence, it is mixed with fine-particle raw ore, coarse ore powder, micro-ore powder and waste phosphate rock powder to obtain phosphate rock powder.

[0016] In this invention, open-pit phosphate ore generally has low impurity content and hard texture, and is often mined by blasting; deep-buried phosphate ore generally has high impurity content and soft texture, and is often mined by drilling and electric scraper; the mixing ratio of the two can be any ratio, such as 1:1, 2:1, or 3:2, etc.

[0017] Preferably, in step 101), the refining involves crushing the mixed ore composed of open-pit phosphate mine ore and deep-buried phosphate mine ore to a particle size of ≤30mm, preferably ≤25mm.

[0018] Preferably, in step 101), the washing involves repeatedly washing the refined raw ore mixture with water. The liquid-to-solid mass ratio during a single wash is 1~6:1, preferably 2~4:1.

[0019] Preferably, in step 101), the drying is to dry the washed raw ore mixture at a temperature of 110~300℃ (preferably 150-250℃) until the moisture content is <10wt% (preferably <8wt%).

[0020] Preferably, in step 101), the particle size of the raw ore lump is 20-30 mm. The particle size of the large-particle raw ore is between 5 and 20 mm in diameter (generally excluding the endpoint values). The particle size of the fine-particle raw ore is no greater than 5 mm.

[0021] Preferably, in step 102), the grinding process involves grinding large-particle raw ore to a particle size of ≤1mm, with the proportion of such particles not less than 95%.

[0022] Preferably, in step 102), the particle size of the coarse ore powder is >1 mm and ≤5 mm. The particle size of the fine ore powder is ≥0.5 mm and ≤1 mm. The particle size of the micro-ore powder is <0.5 mm.

[0023] Preferably, in step 103), the waste phosphate rock powder includes phosphate rock powder generated during the mining of open-pit phosphate mine ore and deep-buried phosphate mine ore, as well as phosphate rock powder generated during the reprocessing of open-pit phosphate mine ore and deep-buried phosphate mine ore.

[0024] Preferably, the calcination temperature in step 103) is 400~600℃, more preferably 450~550℃.

[0025] Preferably, the P2O5 content in the phosphate rock powder in step 103) is not less than 10%, and more preferably 10-15%.

[0026] Preferably, in step 2), the mixing mass ratio of the phosphate rock powder, biomass straw pellets, and quartz powder is 70~75:5~9:20~25.

[0027] It should be noted that, in this invention, the phosphate rock powder may be washed and dried again before mixing, or not (for example, by using a rapid high-temperature hot airflow or microwave rapid drying, which can greatly shorten the drying time and save time; at the same time, it can also prevent some minerals in the phosphate powder from crystallizing and affecting the subsequent crushing).

[0028] It should be noted that, in this invention, the main chemical components of the phosphate rock powder are generally: SiO2 content 10%~15%, CaO content 45%~55%, Fe2O3 content 0.5%~1%, Al2O3 content 3%~5%, MgO content 1%~2%, F content 0.1%~0.3%, and S content 0.5%~0.8%.

[0029] Preferably, in step 2), the biomass straw pellets have a particle size of 0.1~3 mm. The quartz powder has a particle size of 0.1~0.2 mm. Preferably, the biomass straw pellets are soaked and dried in a calcium hydroxide solution before being mixed.

[0030] Preferably, in step 3), the pelleting index is the ratio of the maximum molecular water mass to the maximum capillary water fill factor in the mixture. The maximum capillary water fill factor refers to the difference between the maximum capillary water mass and the maximum molecular water mass. The set pelleting index is 0.8 to 1, preferably 0.8 to 0.9, and more preferably 0.8 to 0.85.

[0031] It should be noted that in this invention, the sphericity index K is a comprehensive parameter that reflects the particle size, particle size distribution, and specific surface area of ​​the material. Its calculation formula is as follows:

[0032] W 分 The percentage of the maximum molecular weight of water, %; W 毛 This represents the maximum capillary water mass percentage, %.

[0033] Preferably, in step 3), the concentration of the rice slurry aqueous solution is 1~10 g / L (rice and water are mixed, heated, crushed, and stirred to obtain the final rice slurry aqueous solution, which is a type of starch solution, generally using expired waste rice as raw material for resource recycling). The concentration of the calcium hydroxide solution is 0.01~0.1 mol / L. The particle size of the mixture after granulation is 3~10 mm. The particle size of the green phosphate rock pellets is 15~30 mm. The amount of rice slurry aqueous solution and calcium hydroxide solution added results in an overall moisture content of 6~8 wt% for the green phosphate rock pellets and a moisture content of 8.5~10 wt% for the outer layer of the green phosphate rock pellets.

[0034] Preferably, in step 4), the sintering process involves using natural phosphate rock (i.e., raw phosphate rock) as a base material, followed by drying, preheating, roasting, and cooling of the raw phosphate rock pellet layer to obtain sintered phosphate rock pellets.

[0035] The drying process specifically involves: first drying the material to be sintered at 200-300℃ for 30-60 minutes; then drying it at 350-450℃ for 10-40 minutes; and finally drying it at 500-700℃ for 8-25 minutes. The first drying is achieved using intermittent microwave drying, while the second and third drying processes are performed using hot air drying.

[0036] Preheating specifically involves preheating the dried material at a temperature of 750~950℃ for 3~20 minutes.

[0037] The roasting process involves roasting the preheated material at a temperature of 1100~1350℃ for 0.2~5 hours.

[0038] The cooling process involves first cooling the calcined material to 600-800°C using room temperature air, and then further cooling it to 150-300°C using room temperature air.

[0039] Preferably, the hot air generated from the second cooling is circulated as the hot air for the second drying (the hot air after the second drying is discharged after dust removal). The hot air generated from the first cooling is circulated as the hot air for preheating. The hot air generated from calcination is treated with dust and then used as the hot air for the third drying. The hot air generated from the third drying and preheating is treated with dust removal, desulfurization, and denitrification before being discharged.

[0040] Preferably, the P2O5 content in the natural phosphate rock is not less than 18%. The thickness of the base material is 50-80 mm. The thickness of the green phosphate rock pellet layer is 100-200 mm. The particle size of the molten phosphate rock pellets is not less than 5 mm.

[0041] Preferably, in step 5), the mixing mass ratio of phosphate rock pellets to coke is 75~90:10~25, more preferably 80~88:12~20.

[0042] Preferably, the reduction treatment temperature is 1300~1500℃, and the reduction treatment time is 5~9 hours. The drying process uses phosphorus-containing flue gas as a heat source.

[0043] This invention utilizes open-pit phosphate mines, deep-buried phosphate mines, and corresponding low-grade phosphate rock powder to produce yellow phosphorus. This broadens the application range and expands resource utilization, solving the problem of how to prepare high-purity yellow phosphorus from existing low-grade phosphate ore, thus enabling the effective utilization of large quantities of low-grade phosphate ore. Furthermore, this invention utilizes abandoned vertical shaft furnaces in the steel industry for yellow phosphorus production, avoiding the waste of resources and equipment caused by the direct dismantling of these furnaces. By using these abandoned furnaces to produce phosphorus, resource reuse is achieved. Since vertical shaft furnace phosphorus production has low energy consumption, it further reduces phosphorus production costs.

[0044] In this invention, the method for obtaining open-pit phosphate ore is generally as follows: the open-pit phosphate mine is first blasted, and then mined to obtain the open-pit phosphate ore. The method for obtaining deep-buried phosphate ore is generally as follows: the deep-buried phosphate mine is first drilled, and then the ore is extracted using an electric scraper to obtain the deep-buried phosphate ore. In this process, it is necessary to collect and store the phosphate ore powder (one type of waste phosphate ore powder) generated during the blasting and mining of the open-pit phosphate mine, as well as the phosphate ore powder (one type of waste phosphate ore powder) generated during the drilling and electric scraper extraction of the deep-buried phosphate mine.

[0045] In this invention, the mixing of open-pit phosphate ore and deep-buried phosphate ore broadens its applicability and expands the scope of resource utilization. By washing the refined ore mixture, wet mud adhering to the phosphate ore can be removed, along with soluble substances (such as sodium chloride and free lime), thereby improving the grade of the phosphate ore and reducing the difficulty of subsequent processing.

[0046] In this invention, the washed and dried raw ore mixture is graded and screened to separate it into three grades: mixed raw phosphate ore with a particle size of 20mm~30mm (including the endpoint value) is classified as irregular raw ore lump (which can be used as a base material for subsequent sintering); mixed raw phosphate ore with a particle size between 5mm and 20mm (excluding the endpoint value) is classified as large-particle raw ore; and mineral powder with a particle size ≤5mm is classified as fine-particle raw ore (which can be used in subsequent mixing to obtain phosphate ore powder for sintering batching and briquetting). The purpose of grading and screening is to refine and classify the raw ore mixture so that it can be fully utilized in subsequent processes, thereby improving the utilization efficiency of phosphorus resources and avoiding the production of solid waste.

[0047] In this invention, the large-particle raw ore with a particle size between 5 mm and 20 mm is further ground (the proportion of particles with a particle size ≤ 1 mm is not less than 95%), thereby obtaining raw ore coarse powder with a particle size of 1 mm to 5 mm, raw ore fine powder with a particle size of 0.5 mm to 1 mm, and raw ore micro powder with a particle size < 0.5 mm. The fine ore powder with a particle size of 0.5mm~1mm undergoes impurity removal treatment (including flotation, magnetic separation, photoelectric separation, and calcination). Specifically, the process begins with the use of flotation agents (for phosphate rock flotation, the flotation agents include collectors, depressants, and synergists. Collectors can be long-chain fatty acids and their soaps. In flotation, long-chain fatty acids and their soaps are used to float phosphate and carbonate minerals, exhibiting strong collecting ability and sensitivity to pulp and certain ions. Depressants can be carboxymethyl cellulose, citric acid, etc. Phosphate ore often contains carbonate minerals such as dolomite and calcite; depressants can remove these impurities. Synergists can be surfactants). As an alkanolamide, in phosphate rock flotation, the flotation performance can be improved by adding a small amount of activator to a long-chain fatty acid collector, causing the phosphate minerals to float while gangue and other impurities sink, thus obtaining initially enriched phosphate rock. Then, the initially enriched phosphate rock undergoes magnetic separation to remove the magnetic minerals, followed by photoelectric separation. Utilizing the different colors of the phosphate rock and impurity minerals, photoelectric elements are used for identification, and compressed air jets are controlled to separate the phosphate rock from the impurity minerals, resulting in enriched phosphate rock. Finally, the enriched phosphate rock is calcined by burning a mixture of combustible gas and air to obtain the final enriched phosphate rock powder. Generally, the calorific value of the combustible gas is ≥3000 kcal / Nm³. 3 The calcination temperature is 400~600℃. Through calcination, organic matter, carbon dioxide and some fluorine in the enriched phosphate rock are removed. The hot gas after calcination can be returned to the raw ore drying step to dry the mixed raw phosphate rock, thereby improving the grade of this part of the phosphate rock powder. This not only improves the utilization value of this part of the phosphate rock powder, but also helps to improve the grade of the final artificial finished product, phosphate lump ore.

[0048] In this invention, the process involves grinding a mixture of phosphate rock powder, fine bulk materials, and low-temperature calcined pellets. The phosphate rock powder has low hardness and is relatively easy to grind, but its pelletizing ability is weak. The fine bulk materials and low-temperature calcined pellets have high hardness and are more difficult to grind, but after fine grinding, they exhibit good hydrophilicity and better pelletizing ability. The pelletizing index is improved after fine grinding, eliminating the need for binders to meet the green pellet strength requirements. The combination of high and low hardness materials, along with the material-to-material grinding process, reduces grinding energy consumption, increases fine grinding efficiency, and enhances the grinding effect.

[0049] In this invention, the process involves pretreatment of low-grade phosphate rock powder through washing, filtration, rapid drying, and grinding. This not only yields a particle size distribution with good pelletizing properties but also improves the grade of the phosphate rock powder.

[0050] In this invention, the sintering mixture includes phosphate rock powder, quartz powder, biomass straw pellets, etc. Small pellets are obtained by spraying a rice slurry aqueous solution for mixing and granulation, followed by spraying a calcium hydroxide solution to form larger pellets. During the batching process, the addition of quartz powder significantly increases the silicon content of the phosphate rock pellets, adjusts the acidity, and increases the acidity of the pellets (e.g., acidity greater than 0.85), which is beneficial for improving the roasting strength of the pellets. In subsequent phosphorus production, quartz can also act as a flux to promote phosphorus reduction. At high temperatures, quartz can react with calcium oxide in the phosphate rock to form easily fusible slag, while simultaneously lowering the melting temperature of the reactants and reducing energy consumption. It should be noted that the amount of quartz added should not be too high, as excessive amounts will form a large liquid phase, damaging the furnace body. In the process of this invention, by adopting layered pelletizing, the outer layer of the pellets has high moisture content and the inner layer has low moisture content. Therefore, the vapor pressure is reduced in the later stage of pellet drying, which can not only prevent the pellets from bursting in the later stage of drying, but also reduce the overall moisture content of the pellets and save drying energy consumption.

[0051] In this invention, adding a rice slurry aqueous solution during mixing and granulation improves the granulation effect, resulting in better particle size distribution and stronger pellets. This also provides additional heat during subsequent roasting, further enhancing the high-temperature consolidation strength of the green pellets. During pelleting, adding a calcium hydroxide solution not only increases the strength of the green pellets but also adjusts their acidity, enhancing their physicochemical and metallurgical properties. This invention uses an aqueous solution of calcium hydroxide as the pelleting raw material, mixing it with the pelletizing material. During mixing, the calcium hydroxide aqueous solution adsorbs onto the surface of the pelletizing particles, existing as molecular water within the pelletizing material. This results in a uniform distribution of a large number of calcium ions on the surface of the pelletizing particles, avoiding the situation in conventional pelletizing materials where the calcium component is mainly in the calcium hydroxide particles, with virtually no calcium ions in the molecular water on the surface of the pelletizing particles. Molecular water does not flow on the surface of the particles. During the process of adding water in pelletizing, water is adsorbed on the surface of the pelletizing material particles and migrates between the particles. When the calcium ions in the molecular water that are uniformly dispersed on the surface of the pelletizing material particles come into contact with the carbonate ions in the water, the calcium ions and carbonate ions undergo a carbonation reaction to generate calcium carbonate. During the precipitation of the newly formed calcium carbonate, the pelletizing material particles that are in contact with each other will be bonded together, which will increase the carbonation and consolidation rate of the green pellets and the strength of the green pellets.

[0052] In this invention, fine phosphate rock powder and biomass straw are mixed, granulated into small balls, and then made into large balls. The moisture content of the small balls and the large balls (outer layer) are different. By adopting layered pelletizing, the outer layer of the pellets has high moisture content and the inner layer has low moisture content, which reduces the vapor pressure in the later stage of the pellet drying time and avoids the pellets from bursting in the later stage of drying. At the same time, it also reduces the overall moisture content of the pellets and saves drying energy consumption.

[0053] In this invention, the process does not require the addition of a special binder, and P2O5 is not lost during roasting. After removing impurities such as carbonates, the P2O5 content can be increased by approximately 1.5%, thus improving the phosphorus grade of the pellets and lumps. This invention yields a large quantity of phosphate rock pellets with a particle size of 18-30 mm, exhibiting a concentrated and stable particle size distribution and good permeability. Under the high-temperature reducing atmosphere of subsequent yellow phosphorus production, the pulverization rate is low, significantly reducing dust generation during phosphorus production. Furthermore, the phosphate rock pellets have high grade, good chemical composition, and high strength, facilitating subsequent transportation and improving transportability, thereby reducing transportation costs. In addition, their low moisture content and low carbonate content effectively reduce power consumption in subsequent lump ore phosphorus production, improving economic efficiency.

[0054] In this invention, the process of obtaining finished phosphate ore lumps from green phosphate rock pellets through sintering requires transfer and heat treatment, with roasting temperatures exceeding 1100℃. This necessitates that the green phosphate rock pellets possess sufficient strength to prevent excessive breakage during transfer and bursting during heat treatment. Therefore, this invention incorporates biomass straw pellets into the feedstock, distributing them throughout the green phosphate rock pellets. This provides diffusion channels for internal moisture evaporation during drying, significantly increasing the rate of water vapor escape. Furthermore, it effectively prevents the rapid evaporation of water molecules at high temperatures, which could lead to bursting of the green phosphate rock pellets. Simultaneously, the fibers of the biomass straw in the pellets enhance the adhesion between phosphate rock powder particles, improving the pellet strength. Additionally, the biomass straw provides heat during subsequent roasting, aiding in the high-temperature consolidation of the green phosphate rock pellets and further improving their physical strength and chemical properties.

[0055] In this invention, to further improve the strength of green phosphate rock pellets, the biomass straw pellets undergo pretreatment before mixing. Specifically, the biomass straw pellets are soaked in a calcium hydroxide solution of a certain concentration (e.g., 0.01-0.5 mol / L) for 0.1-5 hours. After soaking, the biomass straw pellets are filtered and dried before being added to the batch. Because the biomass straw adsorbs calcium hydroxide, it improves the bonding performance with other materials during the batching process, increasing the strength of the green phosphate rock pellets and significantly reducing the breakage rate during handling. Simultaneously, during subsequent heat treatment, the biomass straw decomposes upon heating, releasing carbon dioxide and water. The released carbon dioxide, under the action of water vapor, reacts with the internal calcium hydroxide to form a compound that acts as a binder (the adsorbed calcium hydroxide solidifies internally as calcium carbonate), further improving the bonding strength between the biomass straw and other raw materials. This helps prevent high-temperature cracking while greatly ensuring and improving the strength of the finished phosphate rock pellets and reducing the ore powder rate. It should be noted that the amount of biomass straw added should not be too much or too little. Too much straw will reduce the proportion of phosphate rock powder and quartz powder, thus reducing the yield. At the same time, too much straw particles will create more large pores inside the finished phosphate rock pellets after heat treatment, which will easily lead to the collapse and pulverization of the finished phosphate rock pellets, which is not conducive to improving the strength of the finished phosphate rock pellets. On the other hand, if the amount added is too little, it will not be conducive to improving the internal bonding strength of the green phosphate rock pellets, which will easily cause the green pellets to break up before heat treatment.

[0056] In this invention, the drying process of the sintered material includes intermittent microwave drying (primary drying) and two-stage hot air drying (secondary and tertiary drying). Microwave heating is used first, allowing simultaneous heating of the green pellets' interior and exterior. This causes both internal and external moisture to vaporize and diffuse outwards simultaneously, preventing cracking due to uneven drying. Furthermore, the three-stage drying process of this invention is a variable-temperature drying method. The drying stages are divided into multiple sections arranged in a sequence from low to high temperature and from long to short time. Compared to conventional drying, this increases the drying speed, shortens the drying time, avoids material cracking during drying, and improves the strength of the material.

[0057] In this invention, during the sintering heat treatment process, the dust after the hot air is purged is collected. This dust is first humidified and then returned to the sintering mixing step to participate in the briquetting process.

[0058] In this invention, the phosphate rock pellets obtained after sintering heat treatment also need to be screened to select finished phosphate rock pellets that meet the requirements for yellow phosphorus production (generally requiring a particle size of not less than 5 mm, preferably not less than 8 mm). The bulk materials generated in the above screening steps are recycled and returned for batching, granulation, and pelletizing, thereby saving resources and minimizing solid waste discharge.

[0059] In this invention, natural phosphate rock lumps (i.e., irregular lumps with a P2O5 content of approximately 18% to 20%) with a grade higher than that of low-grade phosphate rock powder are used as a base material. This mixing method can improve the average grade of the finished product lumps. At the same time, the metallurgical properties of the natural phosphate rock lumps are further improved after heat treatment. Using natural phosphate rock lumps as a base material increases permeability and protects the roasting equipment. By selecting an appropriate base material thickness, the production capacity is also increased.

[0060] In this invention, to reduce heat emissions and save energy, the hot air emitted from each node of the system is selectively recycled based on the characteristics of each operating condition within the system. Specifically, the hot air generated during cooling is recycled to provide heat for processes such as drying and preheating. Furthermore, waste heat is fully recovered through cascaded utilization, significantly reducing additional heating energy consumption. In addition, this invention also recycles and utilizes various bulk materials and dust generated during the process. The cascaded utilization of waste heat further significantly reduces additional heating energy consumption, achieving the recycling of valuable resources and contributing to environmental protection.

[0061] In this invention, phosphorus is produced in a vertical shaft furnace using coke as a reducing agent, resulting in low cost and good reducing properties. Water is used as a cooling medium to cool and precipitate the yellow phosphorus from the flue gas, achieving low cost and good results. Furthermore, a portion of the yellow phosphorus flue gas is used to dry the wet phosphorus, allowing for recycling, reducing energy consumption, and improving the purity of the yellow phosphorus, yielding high-quality yellow phosphorus.

[0062] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0063] 1. This invention reuses phosphate rock powder from phosphate mining and processing, solving the problem of resource waste caused by the inability to reuse phosphate rock powder in existing phosphate mining and processing. It also realizes the full utilization of phosphate rock, greatly alleviating the pressure on the production and use of phosphorus resources, and solving the problem of land resource waste caused by the large-scale stockpiling of phosphate rock powder in existing phosphate mining and processing. At the same time, the use of vertical shaft furnaces for phosphorus production improves the efficiency of equipment resource utilization, avoids the waste of equipment resources, and produces high-quality yellow phosphorus products.

[0064] 2. The finished phosphate rock pellets produced by this invention have a concentrated and stable particle size distribution, good air permeability, and low pulverization rate under the high-temperature reducing atmosphere of subsequent yellow phosphorus production, which can greatly reduce the amount of dust in phosphorus production. Furthermore, these phosphate rock pellets have high grade, good chemical composition, and high strength, facilitating subsequent transportation and exhibiting strong transportability. Their low moisture content and low carbonate content can effectively reduce energy consumption in subsequent phosphorus production and improve the purity of the yellow phosphorus product. Attached Figure Description

[0065] Figure 1 This is a schematic diagram of the overall process for producing phosphorus from phosphate rock powder according to the present invention.

[0066] Figure 2 This is a schematic diagram of the pretreatment process for phosphate ore according to the present invention. Detailed Implementation

[0067] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0068] Example 1

[0069] Open-pit phosphate mines are first blasted and then mined to obtain open-pit phosphate ore. Deep-buried phosphate mines are first drilled and then extracted using electric scrapers to obtain deep-buried phosphate ore. The open-pit and deep-buried phosphate ores are mixed at a mass ratio of 1:1.2 and then finely crushed to a particle size ≤30mm to obtain a raw ore mixture. This mixture is then washed three times with water at a liquid-to-solid mass ratio of 4:1, and dried at 180℃ until the moisture content is below 8wt%. After drying, it is screened to obtain raw ore lumps with a particle size of 20-30mm (collected for later use), large particles with a particle size between 5-20mm, and fine particles with a particle size ≤5mm (collected for later use). Further, the large particles of raw ore with a particle size between 5 and 20 mm are ground until the proportion of particles with a particle size ≤ 1 mm is greater than 97%, and then screened again to obtain raw ore coarse powder with a particle size > 1 mm and ≤ 5 mm (collected for later use), raw ore fine powder with a particle size ≥ 0.5 mm and ≤ 1 mm, and raw ore micro powder with a particle size < 0.5 mm (collected for later use).

[0070] First, the fine ore powder with a particle size ≥0.5mm and ≤1mm is subjected to mineral processing. A flotation agent is used to float the phosphate minerals while gangue and other impurities sink, resulting in pre-enriched phosphate ore powder. Then, the pre-enriched phosphate ore is subjected to magnetic separation to remove the magnetic minerals. Finally, the different colors of the phosphate ore and impurity minerals are used to identify them with photoelectric elements, and compressed air jets are controlled to separate the phosphate ore and impurity minerals, resulting in the final enriched phosphate ore powder.

[0071] The final enriched phosphate rock powder is calcined at 550℃ to remove organic matter, carbon dioxide and some fluorine from the final enriched phosphate rock. Then, the calcined phosphate rock powder is mixed with fine particles of raw ore, coarse powder of raw ore, micro powder of raw ore and waste phosphate rock powder to obtain phosphate rock powder with a P2O5 content of about 14.28%.

[0072] Example 2

[0073] Corn stalks were crushed to a particle size of less than 2 mm to obtain stalk pellets, and quartz was pulverized to obtain quartz powder. Then, the phosphate rock powder, stalk pellets, and quartz powder prepared in Example 1 were mixed evenly at a mass ratio of 71:7:22 to obtain a mixture. Then, according to the requirement of a pelleting index of 0.85, a rice slurry aqueous solution with a concentration of 6 g / L was first added to the mixture for pelleting treatment. After obtaining small pellets with a particle size of about 5 mm, a calcium hydroxide solution with a concentration of 0.03 mol / L was added for pelletizing treatment to obtain green phosphate rock pellets with a particle size of about 28 mm (the overall moisture content is about 7.2 wt%, and the moisture content of the outer layer is about 9.0 wt%).

[0074] The raw ore lump (P2O5 content approximately 19.15%) was laid as the base material for the sintering trolley, with a thickness of 70 mm. Then, a 190 mm thick layer of green phosphate ore pellets was laid on top of the base material. After laying, the sintering layer was first dried using microwave at 250℃ for 40 min, then dried with hot air at 400℃ for 25 min, and finally dried with hot air at 600℃ for 12 min. After drying, the sintering layer was preheated with hot air at 850℃ for 10 min. After preheating, the sintering layer was roasted at 1200℃ for 50 min using a mixture of natural gas and air. After roasting, the roasted clinker was cooled once to approximately 700℃ using room temperature air, and then further cooled a second time to approximately 200℃ using room temperature hot air. After cooling, the clinker was screened, and clinker blocks ≥5 mm in size were collected as the finished phosphate ore pellets (P2O5 content approximately 39.22%).

[0075] Finished phosphate rock pellets and coke are mixed at a mass ratio of 85:15 and added to a vertical shaft furnace. Combustion of a mixture of combustible gas and air provides heat for phosphorus production. At 1400℃, the reducing properties of coke at high temperatures reduce the phosphorus in the phosphate rock pellets, resulting in yellow phosphorus-containing flue gas escaping from the top of the furnace. The remaining solid waste containing calcium silicate is discharged from the bottom. The yellow phosphorus flue gas escaping from the top of the furnace is collected and cooled in a water tank. The yellow phosphorus in the flue gas precipitates as a solid underwater, while soluble impurities dissolve in the water. Solid-liquid separation and filtration yield wet yellow phosphorus. A portion of the collected high-temperature yellow phosphorus flue gas is used to dry the wet yellow phosphorus, obtaining high-quality yellow phosphorus (99.91% purity). The dried yellow phosphorus flue gas is then circulated back into the water tank for further cooling.

[0076] Example 3

[0077] Corn stalks were crushed to a particle size of less than 2 mm and then soaked in a 0.02 mol / L calcium hydroxide solution for 1 hour. After filtration, modified straw granules were obtained. Quartz was crushed to obtain quartz powder. The phosphate rock powder, modified straw granules, and quartz powder prepared in Example 1 were then mixed evenly in a mass ratio of 71:7:22 to obtain a mixture. According to the requirement of a pelleting index of 0.85, a rice slurry aqueous solution with a concentration of 6 g / L was first added to the mixture for pelleting treatment. After obtaining small balls with a particle size of about 5 mm, a calcium hydroxide solution with a concentration of 0.03 mol / L was added for pelletizing treatment to obtain green phosphate rock pellets with a particle size of about 28 mm (the overall moisture content is about 7.5 wt%, and the outer layer moisture content is about 9.4 wt%).

[0078] The raw ore lump (P2O5 content approximately 19.15%) was laid as the base material for the sintering trolley, with a thickness of 70 mm. Then, a 190 mm thick layer of green phosphate ore pellets was laid on top of the base material. After laying, the sintering layer was first dried using microwave at 250℃ for 40 min, then dried with hot air at 400℃ for 25 min, and finally dried with hot air at 600℃ for 12 min. After drying, the sintering layer was preheated with hot air at 850℃ for 10 min. After preheating, the sintering layer was roasted at 1200℃ for 50 min using a mixture of natural gas and air. After roasting, the roasted clinker was cooled once to approximately 700℃ using room temperature air, and then further cooled a second time to approximately 200℃ using room temperature hot air. After cooling, the clinker was screened, and clinker blocks ≥5 mm in size were collected as the finished phosphate ore pellets (P2O5 content approximately 40.06%).

[0079] Finished phosphate rock pellets and coke are mixed at a mass ratio of 85:15 and added to a vertical shaft furnace. Combustion of a mixture of combustible gas and air provides heat for phosphorus production in the furnace. At 1400℃, the reducing properties of coke at high temperatures reduce the phosphorus in the phosphate rock pellets, resulting in yellow phosphorus-containing flue gas escaping from the top of the furnace. The remaining solid waste containing calcium silicate is discharged from the bottom. The yellow phosphorus flue gas escaping from the top of the furnace is collected and cooled in a water tank. The yellow phosphorus in the flue gas precipitates as a solid underwater, while soluble impurities in the flue gas dissolve in the water. Solid-liquid separation and filtration yield wet yellow phosphorus. A portion of the collected high-temperature yellow phosphorus flue gas is used to dry the wet yellow phosphorus, obtaining high-quality yellow phosphorus (99.98% purity). The dried yellow phosphorus flue gas is then circulated back into the water tank for further cooling.

[0080] Example 4

[0081] Corn stalks were crushed to a particle size of less than 2 mm to obtain stalk pellets, and quartz was pulverized to obtain quartz powder. Then, the phosphate rock powder, stalk pellets, and quartz powder prepared in Example 1 were mixed evenly at a mass ratio of 75:2:23 to obtain a mixture. Then, according to the requirement of a pelleting index of 0.85, a rice slurry aqueous solution with a concentration of 6 g / L was first added to the mixture for pelleting treatment. After obtaining small pellets with a particle size of about 5 mm, a calcium hydroxide solution with a concentration of 0.03 mol / L was added for pelletizing treatment to obtain green phosphate rock pellets with a particle size of about 28 mm (the overall moisture content is about 7.0 wt%, and the moisture content of the outer layer is about 9.1 wt%).

[0082] The raw ore lump (P2O5 content approximately 19.15%) was laid as the base material for the sintering trolley, with a thickness of 70 mm. Then, a 190 mm thick layer of green phosphate ore pellets was laid on top of the base material. After laying, the sintering layer was first dried using microwave at 250℃ for 40 min, then dried with hot air at 400℃ for 25 min, and finally dried with hot air at 600℃ for 12 min. After drying, the sintering layer was preheated with hot air at 850℃ for 10 min. After preheating, the sintering layer was roasted at 1200℃ for 50 min using a mixture of natural gas and air. After roasting, the roasted clinker was cooled once to approximately 700℃ using room temperature air, and then further cooled a second time to approximately 200℃ using room temperature hot air. After cooling, the clinker was screened, and clinker blocks ≥5 mm in size were collected as the finished phosphate ore pellets (P2O5 content approximately 31.01%).

[0083] Finished phosphate rock pellets and coke are mixed at a mass ratio of 85:15 and added to a vertical shaft furnace. Combustion of a mixture of combustible gas and air provides heat for phosphorus production. At 1400℃, the phosphorus in the phosphate rock pellets is reduced using the reducing properties of coke at high temperatures, and the phosphorus escapes from the top of the furnace as yellow phosphorus-containing flue gas. The remaining solid waste containing calcium silicate is discharged from the bottom of the furnace. The yellow phosphorus flue gas escaping from the top of the furnace is collected and cooled in a water tank. The yellow phosphorus in the flue gas precipitates as a solid underwater, while soluble impurities in the flue gas dissolve in the water. Solid-liquid separation and filtration yield wet yellow phosphorus. A portion of the collected high-temperature yellow phosphorus flue gas is used to dry the wet yellow phosphorus, obtaining high-quality yellow phosphorus (purity 99.81%). The dried yellow phosphorus flue gas is then circulated back into the water tank for further cooling.

[0084] Example 5

[0085] Corn stalks were crushed to a particle size of less than 2 mm to obtain stalk pellets, and quartz was pulverized to obtain quartz powder. Then, the phosphate rock powder, stalk pellets, and quartz powder prepared in Example 1 were mixed evenly at a mass ratio of 68:12:20 to obtain a mixture. Then, according to the requirement of a pelleting index of 0.85, a rice slurry aqueous solution with a concentration of 6 g / L was first added to the mixture for pelleting treatment. After obtaining small pellets with a particle size of about 5 mm, a calcium hydroxide solution with a concentration of 0.03 mol / L was added for pelletizing treatment to obtain green phosphate rock pellets with a particle size of about 28 mm (the overall moisture content is about 7.6 wt%, and the moisture content of the outer layer is about 9.5 wt%).

[0086] The raw ore lump (P2O5 content approximately 19.15%) was laid as the base material for the sintering trolley, with a thickness of 70 mm. Then, a 190 mm thick layer of green phosphate ore pellets was laid on top of the base material. After laying, the sintering layer was first dried using microwave at 250℃ for 40 min, then dried with hot air at 400℃ for 25 min, and finally dried with hot air at 600℃ for 12 min. After drying, the sintering layer was preheated with hot air at 850℃ for 10 min. After preheating, the sintering layer was roasted at 1200℃ for 50 min using a mixture of natural gas and air. After roasting, the roasted clinker was cooled once to approximately 700℃ using room temperature air, and then further cooled a second time to approximately 200℃ using room temperature hot air. After cooling, the clinker was screened, and clinker blocks ≥5 mm in size were collected as the finished phosphate ore pellets (P2O5 content approximately 25.13%).

[0087] Finished phosphate rock pellets and coke are mixed at a mass ratio of 85:15 and added to a vertical shaft furnace. Combustion of a mixture of combustible gas and air provides heat for phosphorus production in the furnace. At 1400℃, the phosphorus in the phosphate rock pellets is reduced using the reducing properties of coke at high temperatures, and the phosphorus escapes from the top of the furnace as yellow phosphorus-containing flue gas. The remaining solid waste containing calcium silicate is discharged from the bottom of the furnace. The yellow phosphorus flue gas escaping from the top of the furnace is collected and cooled in a water tank. The yellow phosphorus in the flue gas precipitates as a solid underwater when cooled in the water, while soluble impurities in the flue gas dissolve in the water. Solid-liquid separation and filtration yield wet yellow phosphorus. A portion of the collected high-temperature yellow phosphorus flue gas is used to dry the wet yellow phosphorus, obtaining high-quality yellow phosphorus (purity 99.86%). The dried yellow phosphorus flue gas is then circulated back into the water tank for further cooling.

[0088] Example 6

[0089] Corn stalks were crushed to a particle size of less than 2 mm to obtain stalk pellets, and quartz was pulverized to obtain quartz powder. Then, the phosphate rock powder, stalk pellets, and quartz powder prepared in Example 1 were mixed evenly at a mass ratio of 77:8:15 to obtain a mixture. Then, according to the requirement of a pelleting index of 0.85, a rice slurry aqueous solution with a concentration of 6 g / L was first added to the mixture for pelleting treatment. After obtaining small pellets with a particle size of about 5 mm, a calcium hydroxide solution with a concentration of 0.03 mol / L was added for pelletizing treatment to obtain green phosphate rock pellets with a particle size of about 28 mm (the overall moisture content is about 6.8 wt%, and the moisture content of the outer layer is about 8.9 wt%).

[0090] The raw ore lump (P2O5 content approximately 19.15%) was laid as the base material for the sintering trolley, with a thickness of 70 mm. Then, a 190 mm thick layer of green phosphate ore pellets was laid on top of the base material. After laying, the sintering layer was first dried using microwave at 250℃ for 40 min, then dried with hot air at 400℃ for 25 min, and finally dried with hot air at 600℃ for 12 min. After drying, the sintering layer was preheated with hot air at 850℃ for 10 min. After preheating, the sintering layer was roasted at 1200℃ for 50 min using a mixture of natural gas and air. After roasting, the roasted clinker was cooled once to approximately 700℃ using room temperature air, and then further cooled a second time to approximately 200℃ using room temperature hot air. After cooling, the clinker was screened, and clinker blocks ≥5 mm in size were collected as the finished phosphate ore pellets (P2O5 content approximately 35.02%).

[0091] Finished phosphate rock pellets and coke are mixed at a mass ratio of 85:15 and added to a vertical shaft furnace. Combustion of a mixture of combustible gas and air provides heat for phosphorus production in the furnace. At 1400℃, the phosphorus in the phosphate rock pellets is reduced using the reducing properties of coke at high temperatures, and the phosphorus escapes from the top of the furnace as yellow phosphorus-containing flue gas. The remaining solid waste containing calcium silicate is discharged from the bottom of the furnace. The yellow phosphorus flue gas escaping from the top of the furnace is collected and cooled in a water tank. The yellow phosphorus in the flue gas precipitates as a solid underwater when cooled in the water, while soluble impurities in the flue gas dissolve in the water. Solid-liquid separation and filtration yield wet yellow phosphorus. A portion of the collected high-temperature yellow phosphorus flue gas is used to dry the wet yellow phosphorus, obtaining high-quality yellow phosphorus (purity 99.75%). The dried yellow phosphorus flue gas is then circulated back into the water tank for further cooling.

[0092] Example 7

[0093] Corn stalks were crushed to a particle size of less than 2 mm to obtain stalk pellets, and quartz was pulverized to obtain quartz powder. Then, the phosphate rock powder, stalk pellets, and quartz powder prepared in Example 1 were mixed evenly at a mass ratio of 64:6:30 to obtain a mixture. Then, according to the requirement of a pelleting index of 0.85, a rice slurry aqueous solution with a concentration of 6 g / L was first added to the mixture for pelleting treatment. After obtaining small pellets with a particle size of about 5 mm, a calcium hydroxide solution with a concentration of 0.03 mol / L was added for pelletizing treatment to obtain green phosphate rock pellets with a particle size of about 28 mm (the overall moisture content is about 7.2 wt%, and the moisture content of the outer layer is about 9.2 wt%).

[0094] The raw ore lump (P2O5 content approximately 19.15%) was laid as the base material for the sintering trolley, with a thickness of 70 mm. Then, a 190 mm thick layer of green phosphate ore pellets was laid on top of the base material. After laying, the sintering layer was first dried using microwave at 250℃ for 40 min, then dried with hot air at 400℃ for 25 min, and finally dried with hot air at 600℃ for 12 min. After drying, the sintering layer was preheated with hot air at 850℃ for 10 min. After preheating, the sintering layer was roasted at 1200℃ for 50 min using a mixture of natural gas and air. After roasting, the roasted clinker was cooled once to approximately 700℃ using room temperature air, and then further cooled a second time to approximately 200℃ using room temperature hot air. After cooling, the clinker was screened, and clinker blocks ≥5 mm in size were collected as the finished phosphate ore pellets (P2O5 content approximately 31.13%).

[0095] Finished phosphate rock pellets and coke are mixed at a mass ratio of 85:15 and added to a vertical shaft furnace. Combustion of a mixture of combustible gas and air provides heat for phosphorus production in the furnace. At 1400℃, the phosphorus in the phosphate rock pellets is reduced using the reducing properties of coke at high temperatures, and the phosphorus escapes from the top of the furnace as yellow phosphorus-containing flue gas. The remaining solid waste containing calcium silicate is discharged from the bottom of the furnace. The yellow phosphorus flue gas escaping from the top of the furnace is collected and cooled in a water tank. The yellow phosphorus in the flue gas precipitates as a solid underwater when cooled in the water, while soluble impurities in the flue gas dissolve in the water. Solid-liquid separation and filtration yield wet yellow phosphorus. A portion of the collected high-temperature yellow phosphorus flue gas is used to dry the wet yellow phosphorus, obtaining high-quality yellow phosphorus (purity 99.82%). The dried yellow phosphorus flue gas is then circulated back into the water tank for further cooling.

[0096] Comparative Example 1

[0097] Quartzite was crushed to obtain quartzite powder; then, the phosphate rock powder and quartzite powder prepared in Example 1 were mixed evenly at a mass ratio of 77:23 to obtain a mixture; then, according to the requirement of a pelletizing index of 0.85, a rice slurry aqueous solution with a concentration of 6 g / L was first added to the mixture for granulation treatment. After obtaining small balls with a particle size of about 5 mm, a calcium hydroxide solution with a concentration of 0.03 mol / L was added for pelletizing treatment to obtain green phosphate rock pellets with a particle size of about 28 mm (the overall moisture content is about 7.0 wt%, and the moisture content of the outer layer is about 8.8 wt%).

[0098] The raw ore lump (P2O5 content approximately 19.15%) was laid as the base material for the sintering trolley, with a thickness of 70 mm. Then, a 190 mm thick layer of green phosphate ore pellets was laid on top of the base material. After laying, the sintering layer was first dried using microwave at 250℃ for 40 min, then dried with hot air at 400℃ for 25 min, and finally dried with hot air at 600℃ for 12 min. After drying, the sintering layer was preheated with hot air at 850℃ for 10 min. After preheating, the sintering layer was roasted at 1200℃ for 50 min using a mixture of natural gas and air. After roasting, the roasted clinker was cooled once to approximately 700℃ using room temperature air, and then further cooled a second time to approximately 200℃ using room temperature hot air. After cooling, the clinker was screened, and clinker blocks ≥5 mm in size were collected as the finished phosphate ore pellets (P2O5 content approximately 29.20%).

[0099] Finished phosphate rock pellets and coke were mixed at a mass ratio of 85:15 and added to a vertical shaft furnace. Combustion of a mixture of combustible gas and air provided heat for phosphorus production. At 1400°C, the phosphorus in the phosphate rock pellets was reduced using the reducing properties of coke at high temperatures, and the phosphorus escaped from the top of the furnace as yellow phosphorus-containing flue gas. The remaining solid waste containing calcium silicate was discharged from the bottom of the furnace. The yellow phosphorus flue gas escaping from the top of the furnace was collected and cooled in a water tank. The yellow phosphorus in the flue gas precipitated as a solid underwater when cooled, while soluble impurities in the flue gas dissolved in the water. Solid-liquid separation and filtration yielded wet yellow phosphorus. A portion of the collected high-temperature yellow phosphorus flue gas was used to dry the wet yellow phosphorus, obtaining high-quality yellow phosphorus (purity 99.61%, yield reduced by approximately 10% compared to Example 1). The dried yellow phosphorus flue gas was then cooled again in the water tank for recycling.

[0100] Comparative Example 2

[0101] Corn stalks were crushed to a particle size of less than 2 mm to obtain stalk pellets. Then, the phosphate rock powder and stalk pellets prepared in Example 1 were mixed evenly at a mass ratio of 91:9 to obtain a mixture. Then, according to the requirement of a pelleting index of 0.85, a rice slurry aqueous solution with a concentration of 6 g / L was first added to the mixture for pelleting treatment. After obtaining small pellets with a particle size of about 5 mm, a calcium hydroxide solution with a concentration of 0.03 mol / L was added for pelleting treatment to obtain green phosphate rock pellets with a particle size of about 28 mm (the overall moisture content is about 6.9 wt%, and the moisture content of the outer layer is about 9.0 wt%).

[0102] The raw ore lump (P2O5 content approximately 19.15%) was laid as the base material for the sintering trolley, with a thickness of 70 mm. Then, a 190 mm thick layer of green phosphate ore pellets was laid on top of the base material. After laying, the sintering layer was first dried using microwave at 250℃ for 40 min, then dried with hot air at 400℃ for 25 min, and finally dried with hot air at 600℃ for 12 min. After drying, the sintering layer was preheated with hot air at 850℃ for 10 min. After preheating, the sintering layer was roasted at 1200℃ for 50 min using a mixture of natural gas and air. After roasting, the roasted clinker was cooled once to approximately 700℃ using room temperature air, and then further cooled a second time to approximately 200℃ using room temperature hot air. After cooling, the clinker was screened, and clinker blocks ≥5 mm in size were collected as the finished phosphate ore pellets (P2O5 content approximately 33.64%).

[0103] Finished phosphate rock pellets and coke were mixed at a mass ratio of 85:15 and added to a vertical shaft furnace. Combustion of a mixture of combustible gas and air provided heat for phosphorus production. At 1400°C, the phosphorus in the phosphate rock pellets was reduced using the reducing properties of coke at high temperatures, and the phosphorus escaped from the top of the furnace as yellow phosphorus-containing flue gas. The remaining solid waste containing calcium silicate was discharged from the bottom of the furnace. The yellow phosphorus flue gas escaping from the top of the furnace was collected and cooled in a water tank. The yellow phosphorus in the flue gas precipitated as a solid underwater when cooled, while soluble impurities in the flue gas dissolved in the water. Solid-liquid separation and filtration yielded wet yellow phosphorus. A portion of the collected high-temperature yellow phosphorus flue gas was used to dry the wet yellow phosphorus, obtaining high-quality yellow phosphorus (purity 99.59%, yield reduced by approximately 15% compared to Example 1). The dried yellow phosphorus flue gas was then cooled again in the water tank for recycling.

Claims

1. A process for the production of yellow phosphorus, characterized in that: The method includes: 1) Phosphate powder is obtained by mixing open-pit phosphate ore and deep-buried phosphate ore and then pre-treating the mixture; specifically including: 101) After mixing open-pit phosphate ore and deep-buried phosphate ore, the mixture is sequentially refined, washed, dried and screened to obtain raw ore lumps, large-particle raw ore and fine-particle raw ore; the particle size of the raw ore lumps is 20~30mm; the particle size of the large-particle raw ore is between 5~20mm; the particle size of the fine-particle raw ore is no greater than 5mm. 102) The large-particle raw ore is ground and classified to obtain coarse raw ore powder, fine raw ore powder, and micro-raw ore powder; the particle size of the coarse raw ore powder is >1mm and ≤5mm; the particle size of the fine raw ore powder is ≥0.5mm and ≤1mm; the particle size of the micro-raw ore powder is <0.5mm; the grinding process ensures that the proportion of large-particle raw ore powder with a particle size ≤1mm is not less than 95%; 103) The fine ore powder of the raw ore is subjected to flotation, magnetic separation, photoelectric separation and calcination in sequence, and then mixed with fine-particle raw ore, coarse ore powder of raw ore, micro ore powder of raw ore and waste phosphate rock powder to obtain phosphate rock powder. 2) A mixture of phosphate rock powder, biomass straw pellets, and quartz powder is obtained; the mass ratio of the phosphate rock powder, biomass straw pellets, and quartz powder is 70~75:5~9:20~25. 3) According to the set pelleting index requirements, rice slurry aqueous solution is first added to the mixture for granulation. After granulation, calcium hydroxide solution is added for pelletizing to obtain phosphate rock green pellets. 4) Sinter the green phosphate rock pellets to obtain sintered phosphate rock pellets; 5) After mixing the phosphate rock pellets with coke, the mixture is fed into a vertical shaft furnace for reduction treatment. The phosphorus-containing flue gas discharged from the vertical shaft furnace is cooled with water, the precipitate is collected and dried to obtain yellow phosphorus.

2. The method according to claim 1, characterized in that: In step 101), the refining process involves crushing the mixed ore composed of open-pit phosphate mine ore and deep-buried phosphate mine ore to a particle size ≤30mm; and / or In step 101), the washing involves repeatedly washing the refined raw ore mixture with water; the liquid-to-solid mass ratio during a single wash is 1-6:1; and / or In step 101), the drying process involves drying the washed raw ore mixture at a temperature of 110~300℃ until the moisture content is <10wt%.

3. The method according to claim 1, characterized in that: In step 103), the waste phosphate rock powder includes phosphate rock powder generated during the extraction of open-pit and buried phosphate mine ore, as well as phosphate rock powder generated during the reprocessing of open-pit and buried phosphate mine ore; and / or The calcination temperature in step 103) is 400~600℃; and / or In step 103), the P2O5 content in the phosphate rock powder is 10-15%.

4. The method according to claim 1, characterized in that: In step 2), the particle size of the biomass straw pellets is 0.1~3mm; the particle size of the quartz powder is 0.1~0.2mm.

5. The method according to claim 1, characterized in that: The biomass straw pellets were soaked and filtered dry in a calcium hydroxide solution before being mixed with other materials.

6. The method according to claim 1, characterized in that: In step 3), the pelleting index is the ratio of the maximum molecular water mass to the maximum capillary water fill value in the mixture; wherein, the maximum capillary water fill value refers to the difference between the maximum capillary water mass and the maximum molecular water mass; the set pelleting index is 0.8~1.

7. The method according to claim 6, characterized in that: The set ball formation index is 0.8~0.

9.

8. The method according to claim 7, characterized in that: The set ball formation index is 0.8~0.

85.

9. The method according to claim 1, characterized in that: In step 3), the concentration of the rice slurry aqueous solution is 1~10 g / L; the concentration of the calcium hydroxide solution is 0.01~0.1 mol / L; the particle size of the granulated mixture is 3~10 mm; the particle size of the green phosphate rock pellets is 15~30 mm; the amount of rice slurry aqueous solution and calcium hydroxide solution added is such that the overall moisture content of the green phosphate rock pellets is 6~8 wt%, and the moisture content of the outer layer of the green phosphate rock pellets is 8.5~10 wt%.

10. The method according to claim 1, characterized in that: In step 4), the sintering process involves using natural phosphate rock as a base material and then sequentially drying, preheating, roasting, and cooling the raw phosphate rock pellets to obtain cooked phosphate rock pellets. Specifically, the drying process involves drying the material to be sintered at 200-300℃ for 30-60 minutes, then at 350-450℃ for 10-40 minutes, and finally at 500-700℃ for 8-25 minutes. The first drying is done using intermittent microwave drying, while the second and third drying processes are done using hot air drying. Preheating specifically involves preheating the dried material at 750~950℃ for 3~20 minutes; The roasting process specifically involves roasting the preheated material at a temperature of 1100~1350℃ for 0.2~5 hours. The cooling process involves first cooling the roasted material to 600-800°C using room temperature air, and then further cooling it to 150-300°C using room temperature air.

11. The method according to claim 10, characterized in that: The hot air generated from the second cooling is circulated as hot air for the second drying; the hot air generated from the first cooling is circulated as hot air for preheating; the hot air generated from roasting is treated with dust removal and then used as hot air for the third drying; the hot air generated from the third drying and preheating is treated with dust removal, desulfurization and denitrification and then discharged.

12. The method according to claim 10, characterized in that: The P2O5 content in natural phosphate rock is not less than 18%; the thickness of the base material is 50-80mm; the thickness of the raw phosphate rock pellet layer is 100-200mm; and the particle size of the molten phosphate rock pellets is not less than 5mm.

13. The method according to claim 1, characterized in that: In step 5), the mixing mass ratio of phosphate rock pellets to coke is 75~90:10~25.

14. The method according to claim 13, characterized in that: In step 5), the mixing mass ratio of phosphate rock pellets to coke is 80~88:12~20.

15. The method according to claim 1, characterized in that: In step 5), the reduction treatment temperature is 1300~1500℃ and the reduction treatment time is 5~9h; the drying is carried out using phosphorus-containing flue gas as a heat source.

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