A method for preparing phosphate rock by briquetting and roasting phosphate rock powder

Abstract

This invention discloses a method for preparing phosphate lumps by briquetting and roasting phosphate rock powder. The method involves pre-treating phosphate rock powder and dust collector ash as briquetting raw materials, and then heat-treating the resulting raw material lumps to obtain phosphate lumps suitable for yellow phosphorus production. The resulting phosphate lumps are of high grade, have good chemical composition, and high strength, facilitating subsequent transportation and exhibiting strong transportability. They also have low moisture content and low carbonate content, effectively reducing power consumption in subsequent lump ore phosphorus production and improving phosphorus purity. This method effectively utilizes phosphate rock powder resources and phosphorus-containing dust collector ash, alleviating the raw material shortage problem for yellow phosphorus enterprises. Furthermore, it effectively reduces raw material costs and saves land resources, aligning with national industrial policies and resource development strategies, and holding significant importance for yellow phosphorus production in my country.

Description

Technical Field

[0001] This invention relates to methods for producing and processing phosphate rock, specifically to a method for preparing phosphate lumps by briquetting and roasting phosphate rock powder, belonging to the field of phosphate rock production and processing technology. Background Technology

[0002] Currently, the main process for producing yellow phosphorus from phosphate rock is the electric furnace method: natural phosphate rock lumps are heated together with a reducing agent in an electric furnace. The reducing agent's reducing properties at high temperatures cause elemental phosphorus to escape as yellow phosphorus vapor. The yellow phosphorus vapor is then cooled and collected to obtain yellow phosphorus. However, this process has high requirements for the phosphate rock raw materials. Generally, the phosphate rock entering the furnace must have uniform particle size, low moisture and carbonate content, a P2O5 content higher than 20%, and a certain thermal strength. To meet production needs, Chinese yellow phosphorus producers mainly use lumpy phosphate rock as raw material.

[0003] With the increasing depletion 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.

[0004] At the same time, during the production process of obtaining natural phosphate rock lumps, enterprises will inevitably generate a large amount of phosphate rock powder. This part of high-quality phosphate rock powder cannot be directly used for electric furnace phosphorus production, resulting in the idleness of high-quality phosphate rock resources and waste of resources. On the other hand, a large amount of phosphate rock powder that cannot be directly used for yellow phosphorus production is stockpiled in the yard, occupying a lot of space and also causing waste of land resources. Summary of the Invention

[0005] To address the problems in existing technologies, such as the shortage of phosphate rock ore for yellow phosphorus production, the underutilization of high-quality phosphate rock powder during the production of natural phosphate rock ore, and the direct waste of dust from yellow phosphorus production processes leading to resource waste, this invention provides a method for preparing phosphate rock ore by briquetting and roasting phosphate rock powder. This method involves pre-treating phosphate rock powder and dust as briquetting raw materials, and then heat-treating the resulting raw material briquettes to obtain phosphate rock ore that meets the requirements for yellow phosphorus production. This method effectively utilizes phosphate rock powder resources and phosphorus-containing dust, alleviating the raw material shortage problem for yellow phosphorus enterprises. Furthermore, it effectively reduces raw material costs and saves land resources, aligning with national industrial policies and resource development strategies, and holding significant importance for yellow phosphorus production in my country.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is specifically as follows:

[0007] A method for preparing phosphate rock briquettes by briquetting and roasting phosphate rock powder, the method comprising the following steps:

[0008] 1) The phosphate rock is crushed and washed with water, and then rapidly dried to obtain phosphate rock powder.

[0009] 2) Modified dust is obtained by modifying phosphorus-containing dust using aluminosilicate.

[0010] 3) Mix the phosphate rock powder, modified dust removal ash and biomass straw evenly to obtain a mixture.

[0011] 4) Add calcium hydroxide solution to the mixture, and then press it into blocks to obtain raw material blocks.

[0012] 5) The raw material blocks are heat-treated to obtain finished phosphate ore.

[0013] Preferably, in step 1), the phosphate rock is a low-grade phosphate rock with the following chemical composition: P2O5 content 10-15%, SiO2 content 10-20%, CaO content 40-50%, 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%.

[0014] Preferably, in step 1), the phosphate rock is washed with water 1-8 times, preferably 3-5 times. The liquid-to-solid mass ratio in a single wash is 1-5:1, preferably 2-4:1.

[0015] Preferably, in step 1), the rapid drying specifically employs a rapid high-temperature hot airflow or microwave rapid drying. Rapid drying can significantly shorten the drying time, saving time; it can also prevent partial mineral crystallization within the mineral powder, which would affect subsequent crushing.

[0016] Preferably, in step 1), the moisture content of the phosphate rock powder is 6-10%, more preferably 8-9%.

[0017] Preferably, in step 1), the particle size of the phosphate rock powder is no greater than 8 mm, and more preferably no greater than 5 mm.

[0018] Preferably, in step 2), the dust collected is generated during the production of yellow phosphorus. The modified dust has the following chemical composition: P2O5 content 20-30%, SiO2 content 30-35%, CaO content 20-25%, Fe2O3 content 1-3%, Al2O3 content 7-9%, MgO content 2-4%, F content 0.5-1%, S content 0.1-0.3%, and moisture content 0.1-1%.

[0019] Preferably, in step 2), the modification treatment specifically involves adding aluminosilicate to the dust and performing a mixed grinding treatment.

[0020] Preferably, in step 2), the aluminosilicate is selected from one or more of potassium feldspar, sodium feldspar, calcium feldspar, montmorillonite, zeolite, etc. The amount of aluminosilicate used is 1-5% of the mass of the dust, for example, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.3%, 4.5%, 4.8%, 5%.

[0021] Preferably, in step 3), the mixing mass ratio of the phosphate rock powder, modified dust removal ash, and biomass straw is 70-90:5-10:10-20, and more preferably 75-85:6-8:12-18.

[0022] Preferably, in step 3), the biomass straw is straw pellets with a particle size of no more than 5 mm, and more preferably straw pellets with a particle size of no more than 3 mm. More preferably, the straw pellets are soaked and drained in a calcium hydroxide solution before mixing. The calcium hydroxide solution can be a calcium hydroxide solution added to the mixture later, or it can be prepared separately and adjusted appropriately according to actual working conditions.

[0023] Preferably, in step 4), the concentration of the calcium hydroxide solution is 0.01-0.2 mol / L, more preferably 0.02-0.1 mol / L. The amount of calcium hydroxide solution added is 1-5% of the total mass of the mixture, more preferably 1.5-4%.

[0024] Preferably, in step 4), the raw material block is an elliptical, pillow-shaped, or flat block structure with an average particle size of not less than 15 mm, preferably 15-35 mm.

[0025] Preferably, in step 5), the heat treatment includes drying, preheating, calcination, and cooling.

[0026] Preferably, in step 5), the drying process is a three-step drying process, wherein: the temperature of the first step is 150-300℃, preferably 200-260℃, and the drying time is 5-60 min, preferably 15-45 min. The temperature of the second step is 320-400℃, preferably 350-380℃, and the drying time is 5-40 min, preferably 10-30 min. The temperature of the third step is 400-480℃, preferably 420-450℃, and the drying time is 5-30 min, preferably 8-25 min. More preferably, the first step of drying is intermittent microwave drying, and the second and third steps of drying are hot air drying.

[0027] Preferably, in step 5), the preheating is a two-step preheating process. The first preheating step is performed at a temperature of 500-650℃, preferably 550-600℃, for a duration of 1-20 minutes, preferably 3-15 minutes. The second preheating step is performed at a temperature of 700-900℃, preferably 750-850℃, for a duration of 15-60 minutes, preferably 20-40 minutes.

[0028] Preferably, in step 5), the calcination temperature is 1000-1350℃, more preferably 1050-1300℃. The calcination time is 0.1-5h, more preferably 0.3-4h.

[0029] Preferably, in step 5), the cooling is a two-step cooling process. The first step involves cooling the calcined material to 600-800°C, preferably 650-750°C, using room temperature air. The second step involves cooling the material cooled in the first step to 120-300°C, preferably 150-250°C, using room temperature air.

[0030] Preferably, natural phosphate rock lumps are used as the base material during the heat treatment of the raw meal blocks. The particle size of the natural phosphate rock lumps is 15-30 mm, preferably 20-25 mm. Its P2O5 content is 15-25%, preferably 18-20%. The thickness of the base material is 60-95 mm, preferably 70-90 mm. The thickness of the raw meal block layer is 100-240 mm, preferably 150-200 mm.

[0031] Preferably, the hot air generated from the first cooling step is circulated as the air for the first and / or second preheating steps. The hot air generated from the second cooling step is circulated as the air for the second drying step. The hot air generated from calcination and the second preheating step, after dust removal treatment, is used as the air for the third drying step. The hot air generated from the second drying step, the third drying step, and the first preheating step is discharged after dust removal, desulfurization, and denitrification treatment.

[0032] In this invention, after crushing, the phosphate rock needs to be screened to obtain phosphate rock powder of the target particle size. During the briquetting process, the briquetting pressure is 1-10 t / cm. 2 (preferably 3-8t / cm) 2 The raw material lumps obtained after heat treatment also need to be screened to select those that meet the particle size requirements for heat treatment. Furthermore, the finished phosphate ore obtained after heat treatment also needs to be screened to select those that meet the requirements for yellow phosphorus production (generally requiring a particle size of not less than 5mm, preferably not less than 8mm). The bulk materials generated from the above screening steps are recycled and returned for batching and briquetting, thereby saving resources and minimizing solid waste discharge.

[0033] In this invention, during the heat treatment process, the dust after the hot air is purged is collected. This dust is first humidified and then returned to the batching step to participate in the briquetting process.

[0034] In this invention, the original stockpiled phosphate rock powder has an uneven particle size, so it needs to be re-crushed to obtain uniform mineral powder with a particle size range of 0-8 mm (preferably 0-5 mm).

[0035] In this invention, multiple water washings of the phosphate rock not only remove sludge and impurities, improving its grade, but also disperse and soften the ore powder, which is beneficial for subsequent uniform crushing. Since the phosphate rock powder also contains sludge and soluble impurities, multiple water washings are necessary to reduce the impurity content and improve the phosphate rock grade.

[0036] In this invention, the dust collected during the electric furnace phosphorus production process has a fine particle size and weak adhesion, which is not conducive to subsequent briquetting and is difficult to recycle. Therefore, this invention modifies the dust using aluminosilicates. On the one hand, this increases the adhesion of the dust and improves the strength of the briquetting material without the need for additional binders or other auxiliary materials. On the other hand, the improved adhesion of the dust allows it to be used in large quantities as a briquetting raw material. Moreover, the dust contains a high content of P2O5, and adding a large amount of the modified dust to the phosphate rock powder can further improve the grade of the briquetting material without loss during roasting. Experiments have shown that the use of dust can increase the P2O5 content of the cost phosphate ore by at least 1%.

[0037] In this invention, the raw material blocks need to undergo transportation and heat treatment to become finished phosphate ore blocks, with roasting temperatures exceeding 1000℃. This requires the raw material blocks to possess sufficient strength to prevent excessive breakage during transportation and significant bursting during heat treatment. Therefore, this invention incorporates biomass straw into the raw material blocks. The biomass straw is distributed throughout the raw material blocks, providing diffusion channels for internal moisture during drying, significantly increasing the rate of water vapor escape and effectively preventing bursting caused by rapid evaporation of water molecules at high temperatures. Simultaneously, the fibers of the biomass straw in the raw material blocks enhance the adhesion between phosphate ore particles, improving the strength of the biomass blocks. Furthermore, the biomass straw in the biomass blocks provides some heat during subsequent roasting, facilitating high-temperature consolidation of the raw material blocks and further improving their physical strength and chemical properties.

[0038] In this invention, the addition of calcium hydroxide solution during the mixing and briquetting process not only improves the strength of the material briquettes but also adjusts their acidity, enhancing their physicochemical and metallurgical properties. This invention uses an aqueous solution of calcium hydroxide as the briquetting raw material, mixing it with the raw materials. During mixing, the calcium hydroxide solution adsorbs onto the surface of the raw material particles, existing as molecular water. This results in a uniform distribution of calcium ions on the surface of the particles, avoiding the situation in conventional raw materials where the calcium component is primarily contained within the calcium hydroxide particles, with virtually no calcium ions in the molecular water on the particle surface. The molecular water does not flow on the particle surface. During briquetting, the water adsorbs onto the surface of the raw material particles and migrates between them. When the calcium ions in the molecular water uniformly dispersed on the surface of the raw material particles come into contact with carbonate ions in the water, a carbonation reaction occurs, generating calcium carbonate. The precipitation of the newly formed calcium carbonate binds the contacting raw material particles together, increasing the carbonation and consolidation rate of the raw material briquettes and improving their strength.

[0039] In this invention, to further improve the strength of the raw material blocks, the biomass straw undergoes pretreatment before mixing. Specifically, the biomass straw particles are soaked in a calcium hydroxide solution (e.g., 0.01-1 mol / L) for 0.1-5 hours. After soaking, the biomass straw particles are filtered dry 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 raw material blocks 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 enhancing the strength of the finished phosphate ore and reducing the 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 dust, thus reducing the yield. At the same time, too much straw particles will create more large pores inside the finished phosphate ore after heat treatment, which will easily lead to the collapse and pulverization of the finished phosphate ore, which is not conducive to improving the strength of the finished phosphate ore. On the other hand, if the amount added is too little, it will not be conducive to improving the internal bonding strength of the raw material blocks, and the raw material blocks will easily break into pieces before heat treatment.

[0040] In this invention, the drying process of the raw material blocks involves intermittent microwave drying and two-stage hot air drying. Microwave heating is used first, allowing for simultaneous heating of the raw material blocks both inside and out. This causes the 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 cracking of the material blocks during drying, and improves the strength of the material blocks.

[0041] In this invention, natural phosphate rock lumps 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 the permeability and protects the roasting device. By selecting an appropriate base material thickness, the production capacity is also increased.

[0042] 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 cascade utilization, significantly reducing additional heating energy consumption. In addition, this invention also recycles and reuses various bulk materials and dust generated during the process, realizing the recycling of valuable resources and contributing to environmental protection.

[0043] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0044] 1. This invention couples the use of low-grade stockpiled phosphate rock powder and yellow phosphorus production dust, solving the problem of resource waste caused by the inability to reuse phosphate rock powder in existing phosphate rock processing, and solving the problem of land resource waste caused by the large-scale stockpiling of phosphate rock powder in existing phosphate rock processing. It realizes the resource reuse of phosphate rock powder and also greatly saves land resources.

[0045] 2: This invention significantly improves the clotting performance of dust collector ash by modifying it, and further enhances the strength of the raw material blocks through the bridging of biomass straw. This also effectively ensures the quality of the finished block mineral products and allows for the containment of more dust collector ash, thereby improving the utilization efficiency of the dust collector ash.

[0046] 3. The finished phosphate ore produced by this invention has a particle size mainly concentrated between 16-35mm, with 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, which can greatly reduce the amount of dust generated during phosphorus production. Furthermore, the ore has high grade, good chemical composition, and high strength, facilitating subsequent transportation and exhibiting strong transportability. Its low moisture content and low carbonate content can effectively reduce the power consumption in subsequent ore phosphorus production and improve the purity of phosphorus. Attached Figure Description

[0047] Figure 1 This is a process flow diagram of the method described in this invention. Detailed Implementation

[0048] 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.

[0049] Example 1

[0050] The phosphate rock powder (P2O5 content of 14.39%) was crushed and then washed three times (the liquid-to-solid mass ratio of each wash was 3:1). After washing, the powder was screened using a 5mm screen, and the undersize material was collected and microwave-dried to obtain phosphate rock powder with a moisture content of about 8.2% for later use.

[0051] The dust collected during the production of yellow phosphorus (with a P2O5 content of 26.51%) was mixed and ground with potassium feldspar (added at 2% of the mass of the dust) to obtain modified dust for later use.

[0052] Corn stalks are crushed to a particle size of less than 2 mm to obtain stalk pellets. Then, phosphate rock powder, dust collector ash, and stalk pellets are mixed in a mass ratio of 80:7.5:12.5 to obtain a mixture. Next, 2.5% (based on the total mass of the mixture), 0.015 mol / L calcium hydroxide solution is added to the mixture and stirred until homogeneous. Finally, a 5 t / cm³ flow rate is applied. 2 The raw material is pressed into blocks under pressure, and after pressing, it is sieved through a 15mm sieve to obtain flat raw material blocks with dimensions of 35×25×15mm.

[0053] Natural lump ore with an average particle size of 22 mm (P2O5 content of 22.20%) was laid as the bottom material of the trolley, with a thickness of 80 mm. Then, a layer of raw meal blocks was laid on top of the bottom material, with a thickness of 180 mm. After laying, the mixture layer was dried using microwave at 240℃ for 30 min, followed by drying with hot air at 360℃ for 20 min, and finally drying with hot air at 430℃ for 12 min. After drying, the mixture layer was preheated with hot air at 580℃ for 8 min, and then preheated again with hot air at 850℃ for 25 min. After preheating, natural gas (9000 kcal / Nm³) was used... 3 The mixture of fuel and air is then roasted at 1200℃ for 30 minutes. After roasting, the clinker is cooled to approximately 700℃ using room temperature air, and then further cooled to approximately 200℃ using room temperature hot air. After cooling, the clinker is screened, and clinker blocks ≥5mm are collected as the finished phosphate ore.

[0054] Example 2

[0055] The phosphate rock powder (P2O5 content of 14.39%) was crushed and then washed three times (the liquid-to-solid mass ratio of each wash was 3:1). After washing, the powder was screened using a 6mm screen, and the undersize material was collected and microwave-dried to obtain phosphate rock powder with a moisture content of about 8.2% for later use.

[0056] The dust collected during the production of yellow phosphorus (with a P2O5 content of 26.51%) was mixed and ground with albite (2% of the mass of the dust) to obtain modified dust for later use.

[0057] Corn stalks are crushed to a particle size of less than 2 mm to obtain stalk pellets. Then, phosphate rock powder, dust collector ash, and stalk pellets are mixed in a mass ratio of 78:6:16 to obtain a mixture. Next, 2.5% (based on the total mass of the mixture), 0.015 mol / L calcium hydroxide solution is added to the mixture and stirred until homogeneous. Finally, a 5 t / cm³ flow rate is applied. 2 The raw material is pressed into blocks under pressure, and after pressing, it is sieved through a 15mm sieve to obtain flat raw material blocks with dimensions of 35×25×15mm.

[0058] Natural lump ore with an average particle size of 22 mm (P2O5 content of 22.20%) was laid as the bottom material of the trolley, with a thickness of 80 mm. Then, a layer of raw meal blocks was laid on top of the bottom material, with a thickness of 200 mm. After laying, the mixture layer was dried using microwave at 230℃ for 30 min, followed by drying with hot air at 350℃ for 20 min, and finally drying with hot air at 450℃ for 12 min. After drying, the mixture layer was preheated with hot air at 600℃ for 8 min, and then preheated again with hot air at 850℃ for 25 min. After preheating, natural gas (9000 kcal / Nm³) was used... 3 The mixture of fuel and air is then burned to form a calcined layer at 1250℃ for 30 minutes. After calcination, the calcined clinker is cooled to approximately 700℃ using room temperature air, and then further cooled to approximately 200℃ using room temperature hot air. After cooling, the clinker is screened, and clinker blocks ≥5mm are collected as the finished phosphate ore.

[0059] Example 3

[0060] The phosphate rock powder (P2O5 content of 14.39%) was crushed and then washed three times (the liquid-to-solid mass ratio of each wash was 3:1). After washing, the powder was screened using a 6mm screen, and the undersize material was collected and subjected to a rapid hot air flow to obtain phosphate rock powder with a moisture content of about 8.2% for later use.

[0061] The dust collected during the yellow phosphorus production process (with a P2O5 content of 26.51%) was mixed and ground with montmorillonite (added at 2.5% of the dust granulation amount) to obtain modified dust for later use.

[0062] Corn stalks were crushed to a particle size of less than 2 mm to obtain stalk pellets. These pellets were then soaked in a 0.02 mol / L calcium hydroxide solution for 1 hour and filtered dry to obtain modified stalk pellets. Phosphate rock powder, dust collector ash, and modified stalk pellets were then mixed in a mass ratio of 78:6:16 to obtain a mixture. 2.5% (based on the total mass of the mixture), 0.015 mol / L calcium hydroxide solution was added to the mixture and stirred until homogeneous. The mixture was then subjected to a 5 t / cm³ flow rate. 2 The raw material is pressed into blocks under pressure, and after pressing, it is sieved through a 15mm sieve to obtain flat raw material blocks with dimensions of 35×25×15mm.

[0063] Natural lump ore with an average particle size of 22 mm (P2O5 content of 22.20%) was laid as the bottom material of the trolley, with a thickness of 80 mm. Then, a layer of raw meal blocks was laid on top of the bottom material, with a thickness of 200 mm. After laying, the mixture layer was dried using microwave at 230℃ for 30 min, followed by drying with hot air at 350℃ for 20 min, and finally drying with hot air at 450℃ for 12 min. After drying, the mixture layer was preheated with hot air at 600℃ for 8 min, and then preheated again with hot air at 850℃ for 25 min. After preheating, coke oven gas (4000 kcal / Nm³) was used. 3 The mixture of fuel and air is then burned to form a calcined layer at 1250℃ for 30 minutes. After calcination, the calcined clinker is cooled to approximately 700℃ using room temperature air, and then further cooled to approximately 200℃ using room temperature hot air. After cooling, the clinker is screened, and clinker blocks ≥5mm are collected as the finished phosphate ore.

[0064] Comparative Example 1

[0065] The phosphate rock powder (P2O5 content of 14.39%) was crushed and then washed three times (the liquid-to-solid mass ratio of each wash was 3:1). After washing, the powder was screened using a 6mm screen, and the undersize material was collected and microwave-dried to obtain phosphate rock powder with a moisture content of about 8.2% for later use.

[0066] Dust collected during the yellow phosphorus production process (P2O5 content 26.51%) was mixed and ground with potassium feldspar (added at 2% of the dust mass) to obtain modified dust for later use. Then, phosphate rock powder and dust were mixed at a mass ratio of 92.9:7.1 to obtain a mixture. Next, 2.5% (based on the total mass of the mixture), 0.015 mol / L calcium hydroxide solution was added to the mixture and stirred until homogeneous. Finally, the mixture was subjected to a 5 t / cm... 2 The raw material is pressed into blocks under pressure, and after pressing, it is sieved through a 15mm sieve to obtain flat raw material blocks with dimensions of 35×25×15mm.

[0067] Natural lump ore with an average particle size of 22 mm (P2O5 content of 22.20%) was laid as the bottom material of the trolley, with a thickness of 80 mm. Then, a layer of raw meal blocks was laid on top of the bottom material, with a thickness of 200 mm. After laying, the mixture layer was dried using microwave at 230℃ for 30 min, followed by drying with hot air at 350℃ for 20 min, and finally drying with hot air at 450℃ for 12 min. After drying, the mixture layer was preheated with hot air at 600℃ for 8 min, and then preheated again with hot air at 850℃ for 25 min. After preheating, natural gas (9000 kcal / Nm³) was used... 3 After being mixed with air and burned, the mixture layer is roasted at 1250℃ for 30 minutes. After roasting, the roasted clinker is cooled to about 700℃ with room temperature air, and then further cooled to about 200℃ with room temperature hot air. After cooling, the clinker is screened, and clinker blocks ≥5mm are collected as finished phosphate ore.

[0068] Comparative Example 2

[0069] The phosphate rock powder (P2O5 content of 14.39%) was crushed and then washed three times (the liquid-to-solid mass ratio of each wash was 3:1). After washing, the powder was screened using a 6mm screen, and the undersize material was collected and microwave-dried to obtain phosphate rock powder with a moisture content of about 8.2% for later use.

[0070] Dust collected during the production of yellow phosphorus (P2O5 content of 26.51%) was mixed and ground with potassium feldspar (added at 2% of the mass of dust) to obtain modified dust collector for later use.

[0071] Corn stalks are crushed to a particle size of less than 2 mm to obtain stalk pellets; then, phosphate rock powder, dust collector ash, and stalk pellets are mixed in a mass ratio of 88.2:6.8:5 to obtain a mixture; then, 2.5% (based on the total mass of the mixture), 0.015 mol / L calcium hydroxide solution is added to the mixture and stirred until homogeneous. Finally, the mixture is subjected to a 5 t / cm³ flow rate... 2 The raw material is pressed into blocks under pressure, and after pressing, it is sieved through a 15mm sieve to obtain flat raw material blocks with dimensions of 35×25×15mm.

[0072] Natural lump ore with an average particle size of 22 mm (P2O5 content of 22.20%) was laid as the bottom material of the trolley, with a thickness of 80 mm. Then, a layer of raw meal blocks was laid on top of the bottom material, with a thickness of 200 mm. After laying, the mixture layer was dried using microwave at 230℃ for 30 min, followed by drying with hot air at 350℃ for 20 min, and finally drying with hot air at 450℃ for 12 min. After drying, the mixture layer was preheated with hot air at 600℃ for 8 min, and then preheated again with hot air at 850℃ for 25 min. After preheating, natural gas (9000 kcal / Nm³) was used... 3 The mixture of fuel and air is then burned to form a calcined layer at 1250℃ for 30 minutes. After calcination, the calcined clinker is cooled to approximately 700℃ using room temperature air, and then further cooled to approximately 200℃ using room temperature hot air. After cooling, the clinker is screened, and clinker blocks ≥5mm are collected as the finished phosphate ore.

[0073] Comparative Example 3

[0074] The phosphate rock powder (P2O5 content of 14.39%) was crushed and then washed three times (the liquid-to-solid mass ratio of each wash was 3:1). After washing, the powder was screened using a 6mm screen, and the undersize material was collected and microwave-dried to obtain phosphate rock powder with a moisture content of about 8.2% for later use.

[0075] Dust collected during the production of yellow phosphorus (P2O5 content of 26.51%) was mixed and ground with potassium feldspar (added at 2% of the mass of dust) to obtain modified dust collector for later use.

[0076] Corn stalks are crushed to a particle size of less than 2 mm to obtain stalk pellets; then, phosphate rock powder, dust collector ash, and stalk pellets are mixed in a mass ratio of 69.7:5.3:25 to obtain a mixture; then, 2.5% (based on the total mass of the mixture), 0.015 mol / L calcium hydroxide solution is added to the mixture and stirred until homogeneous. Finally, the mixture is subjected to a 5 t / cm³ flow rate... 2 The raw material is pressed into blocks under pressure, and after pressing, it is sieved through a 15mm sieve to obtain flat raw material blocks with dimensions of 35×25×15mm.

[0077] Natural lump ore with an average particle size of 22 mm (P2O5 content of 22.20%) was laid as the bottom material of the trolley, with a thickness of 80 mm. Then, a layer of raw meal blocks was laid on top of the bottom material, with a thickness of 200 mm. After laying, the mixture layer was dried using microwave at 230℃ for 30 min, followed by drying with hot air at 350℃ for 20 min, and finally drying with hot air at 450℃ for 12 min. After drying, the mixture layer was preheated with hot air at 600℃ for 8 min, and then preheated again with hot air at 850℃ for 25 min. After preheating, natural gas (9000 kcal / Nm³) was used... 3 The mixture of fuel and air is then burned to form a calcined layer at 1250℃ for 30 minutes. After calcination, the calcined clinker is cooled to approximately 700℃ using room temperature air, and then further cooled to approximately 200℃ using room temperature hot air. After cooling, the clinker is screened, and clinker blocks ≥5mm are collected as the finished phosphate ore.

[0078] Comparative Example 4

[0079] The phosphate rock powder (P2O5 content of 14.39%) was crushed and then screened using a screening machine with a 6mm screen to obtain phosphate rock powder with a moisture content of about 7.7% for later use.

[0080] The dust collected during the production of yellow phosphorus (with a P2O5 content of 26.51%) was mixed and ground with potassium feldspar (added at 2% of the mass of the dust) to obtain modified dust for later use.

[0081] Corn stalks are crushed to a particle size of less than 2 mm to obtain stalk pellets. Then, phosphate rock powder, dust collector ash, and stalk pellets are mixed in a mass ratio of 78:6:16 to obtain a mixture. Next, 2.5% (based on the total mass of the mixture), 0.015 mol / L calcium hydroxide solution is added to the mixture and stirred until homogeneous. Finally, a 5 t / cm³ flow rate is applied. 2 The raw material is pressed into blocks under pressure, and after pressing, it is sieved through a 15mm sieve to obtain flat raw material blocks with dimensions of 35×25×15mm.

[0082] Natural lump ore with an average particle size of 22 mm (P2O5 content of 22.20%) was laid as the bottom material of the trolley, with a thickness of 80 mm. Then, a layer of raw meal blocks was laid on top of the bottom material, with a thickness of 200 mm. After laying, the mixture layer was dried using microwave at 230℃ for 30 min, followed by drying with hot air at 350℃ for 20 min, and finally drying with hot air at 450℃ for 12 min. After drying, the mixture layer was preheated with hot air at 600℃ for 8 min, and then preheated again with hot air at 850℃ for 25 min. After preheating, natural gas (9000 kcal / Nm³) was used... 3 The mixture of fuel and air is then burned to form a calcined layer at 1250℃ for 30 minutes. After calcination, the calcined clinker is cooled to approximately 700℃ using room temperature air, and then further cooled to approximately 200℃ using room temperature hot air. After cooling, the clinker is screened, and clinker blocks ≥5mm are collected as the finished phosphate ore.

[0083] Result detection

[0084] The finished phosphate ore obtained from each of the above embodiments and comparative examples was subjected to various quality tests, and the test results are shown in the table below:

[0085]

[0086]

Claims

1. A method for the production of phosphorite by agglomeration and roasting of rock phosphate, characterized in that: The method includes the following steps: 1) The phosphate rock is crushed and washed with water, and then rapidly dried to obtain phosphate rock powder; 2) Modified dust collector ash is obtained by modifying phosphorus-containing dust collector ash with aluminosilicate; the dust collector ash is generated in the production of yellow phosphorus; the chemical composition of the modified dust collector ash is as follows: P2O5 content 20-30%, SiO2 content 30-35%, CaO content 20-25%, Fe2O3 content 1-3%, Al2O3 content 7-9%, MgO content 2-4%, F content 0.5-1%, S content 0.1-0.3%, and moisture content 0.1-1%; 3) Mix the phosphate rock powder, modified dust collector ash, and biomass straw evenly to obtain a mixture; the mixing mass ratio of the phosphate rock powder, modified dust collector ash, and biomass straw is 70-90:5-10:10-20; the straw particles are soaked and filtered dry in calcium hydroxide solution before mixing. 4) Add calcium hydroxide solution to the mixture, and then press it into briquettes to obtain raw material briquettes; the concentration of the calcium hydroxide solution is 0.01-0.2 mol / L; the amount of calcium hydroxide solution added is 1-5% of the total mass of the mixture; 5) The raw material blocks are heat-treated to obtain finished phosphate ore.

2. The method of claim 1, wherein: In step 1), the phosphate rock is a low-grade phosphate rock with the following chemical composition: P2O5 content 10-15%, SiO2 content 10-20%, CaO content 40-50%, 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%.

3. The method according to claim 1, characterized in that: In step 1), the phosphate rock is washed with water 1-8 times; the liquid-solid mass ratio during a single wash is 1-5:

1.

4. The method according to claim 3, characterized in that: In step 1), the phosphate rock is washed with water 3-5 times; the liquid-solid mass ratio during a single wash is 2-4:

1.

5. The method according to claim 1, characterized in that: In step 1), the rapid drying specifically refers to drying using a rapid hot airflow or microwaves.

6. The method according to claim 1, characterized in that: The phosphate rock powder has a moisture content of 6-10%; and / or The particle size of the phosphate rock powder is no greater than 8 mm.

7. The method according to claim 6, characterized in that: The phosphate rock powder has a moisture content of 8-9%; and / or The particle size of the phosphate rock powder is no greater than 5 mm.

8. The method according to claim 1, characterized in that: In step 2), the modification treatment specifically involves adding aluminosilicate to the dust and performing a mixing and grinding process.

9. The method according to claim 8, characterized in that: The aluminosilicate is selected from one or more of potassium feldspar, sodium feldspar, calcium feldspar, montmorillonite, and zeolite; the amount of the aluminosilicate used is 1-5% of the mass of the dust.

10. The method according to claim 1, characterized in that: In step 3), the mixing mass ratio of the phosphate rock powder, modified dust removal ash, and biomass straw is 75-85:6-8:12-18.

11. The method according to claim 1, characterized in that: The biomass straw is straw particles with a particle size of no more than 5 mm.

12. The method according to claim 11, characterized in that: The biomass straw is straw particles with a particle size of no more than 3 mm.

13. The method according to claim 1, characterized in that: In step 4), the concentration of the calcium hydroxide solution is 0.02-0.1 mol / L; the amount of calcium hydroxide solution added is 1.5-4% of the total mass of the mixture.

14. The method according to claim 1, characterized in that: The raw material blocks are oval, pillow-shaped, or flat block structures with an average particle size of not less than 15 mm.

15. The method according to claim 14, characterized in that: The average particle size of the raw material blocks is 15-35 mm.

16. The method according to claim 1, characterized in that: In step 5), the heat treatment includes drying, preheating, calcination, and cooling.

17. The method according to claim 16, characterized in that: The drying process consists of three steps: the first step is dried at a temperature of 150-300℃ for 5-60 minutes; the second step is dried at a temperature of 320-400℃ for 5-40 minutes; and the third step is dried at a temperature of 400-480℃ for 5-30 minutes.

18. The method according to claim 17, characterized in that: The first drying step is performed at a temperature of 200-260℃ for 15-45 minutes; the second drying step is performed at a temperature of 350-380℃ for 10-30 minutes; and the third drying step is performed at a temperature of 420-450℃ for 8-25 minutes.

19. The method according to claim 17, characterized in that: The first drying step is intermittent microwave drying, while the second and third drying steps are hot air drying.

20. The method according to claim 17, characterized in that: The preheating is a two-step preheating process. The first step preheating temperature is 500-650℃ and the first step preheating time is 1-20 minutes. The second step preheating temperature is 700-900℃ and the second step preheating time is 15-60 minutes.

21. The method according to claim 20, characterized in that: The first preheating temperature is 550-600℃, and the first preheating time is 3-15 minutes; the second preheating temperature is 750-850℃, and the second preheating time is 20-40 minutes.

22. The method according to claim 20, characterized in that: The roasting temperature is 1000-1350℃; the roasting time is 0.1-5h.

23. The method according to claim 22, characterized in that: The roasting temperature is 1050-1300℃; the roasting time is 0.3-4h.

24. The method according to claim 22, characterized in that: The cooling process is a two-step cooling process. The first step involves cooling the roasted material to 600-800°C using room temperature air. The second step involves cooling the material cooled in the first step to 120-300°C using room temperature air.

25. The method according to claim 24, characterized in that: The first cooling step involves cooling the roasted material to 650-750℃ using room temperature air; the second cooling step involves cooling the material cooled in the first step to 150-250℃ using room temperature air.

26. The method according to claim 24, characterized in that: During the heat treatment of raw meal blocks, natural phosphate rock lumps are used as the base material; the particle size of the natural phosphate rock lumps is 15-30 mm; its P2O5 content is 15-25%; the thickness of the base material is 60-95 mm; the thickness of the raw meal block layer is 100-240 mm; and / or The hot air generated from the first cooling step is circulated as the air for the first preheating step and / or the second preheating step; the hot air generated from the second cooling step is circulated as the air for the second drying step; the hot air generated from calcination and the second preheating step is treated with dust removal and then used as the air for the third drying step; the hot air generated from the second drying step, the third drying step, and the first preheating step is treated with dust removal, desulfurization, and denitrification before being discharged.

27. The method according to claim 26, characterized in that: The natural phosphate rock ore has a particle size of 20-25mm; its P2O5 content is 18-20%; the thickness of the base material is 70-90mm; and the thickness of the raw material block layer is 150-200mm.

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