A phosphate rock powder briquetting roasting system and method

Abstract

This invention discloses a phosphate rock powder briquetting and roasting system and method. The system includes a batching subsystem, a roller pressing subsystem, a sieve distribution subsystem, a roasting and cooling subsystem, a finished product sieve molecular system, and a hot air circulation subsystem. This invention solves the problem of resource waste caused by the inability to reuse phosphate rock powder in existing phosphate rock processing, and the problem of land resource waste caused by the large-scale stockpiling of phosphate rock powder. It realizes the resource reuse of phosphate rock powder and greatly saves land resources. Simultaneously, the prepared lump ore product has high quality and strength, is convenient for subsequent transportation, and has strong transportability; the lump ore product has low moisture content and low carbonate content, effectively reducing the power consumption of subsequent lump ore phosphorus production and improving phosphorus purity.

Description

Technical Field

[0001] This invention relates to the technology of resource utilization of phosphate rock powder and yellow phosphorus electric furnace dust, specifically to a phosphate rock powder briquetting and roasting system and method, belonging to the field of phosphate rock powder and dust recycling technology. Background Technology

[0002] my country has large phosphate rock reserves, but the average grade of phosphate rock is low. According to relevant statistics, the average grade of my country's currently recoverable phosphate rock reserves is 23%, lower than the global average of 30%. Among them, low-grade phosphate rock reserves with a P2O5 content of less than 20% account for more than 60%, while high-grade phosphate rock reserves with a P2O5 content of more than 30% account for less than 10%.

[0003] 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.

[0004] my country's phosphate rock resources are mainly low- to medium-grade phosphate rock, with scarce rich ore resources. With the increasing depletion of high-quality phosphate rock, the amount of high-quality phosphate rock suitable for yellow phosphorus production is also decreasing, leading to a growing shortage of natural phosphate rock resources and rising market prices. 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.

[0005] 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 lacks complete recycling equipment and 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, this phosphate rock powder that cannot be directly used for yellow phosphorus production is piled up in large quantities in the stockpile, occupying a lot of space and causing waste of land resources. Summary of the Invention

[0006] In response to the problems of low utilization rate of dust removal equipment in the production of low-grade phosphate rock powder and yellow phosphorus, lack of complete recycling equipment leading to waste of phosphorus resources, and large-scale stockpiling leading to waste of land resources in the existing technology, this invention provides a phosphate rock powder briquetting and roasting system and method. This system can pre-treat the phosphate rock powder and yellow phosphorus production dust generated by enterprises in the production process of obtaining natural phosphate rock lumps for use in yellow phosphorus production. This not only effectively utilizes powdered mineral resources, effectively alleviates the problem of raw material shortage for yellow phosphorus enterprises, but also effectively reduces raw material costs and greatly saves land resources. It is in line with national industrial policies and resource development strategies and is of great significance to yellow phosphorus production enterprises in my country.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0008] According to a first embodiment of the present invention, a phosphate rock powder briquetting and roasting system is provided:

[0009] A phosphate rock powder briquetting and roasting system includes a batching subsystem, a roller pressing subsystem, a sieving and distributing subsystem, a roasting and cooling subsystem, a finished product sieving system, and a hot air circulation subsystem. According to the material flow direction, the batching subsystem, roller pressing subsystem, sieving and distributing subsystem, roasting and cooling subsystem, and finished product sieving system are arranged in series. The hot air circulation subsystem is located within the roasting and cooling subsystem.

[0010] Preferably, the batching subsystem includes a phosphate rock powder silo, a biomass straw silo, and a dust collection ash silo arranged in parallel. Vibration anti-clogging devices and gate valves are installed at the bottom discharge ports of the phosphate rock powder silo, biomass straw silo, and dust collection ash silo. Each gate valve is also equipped with a metering feeder. The discharge end of all metering feeders is connected to the feed end of the roller pressing subsystem via a high-angle belt conveyor.

[0011] Preferably, the batching subsystem includes multiple phosphate rock powder bins, multiple biomass straw bins, and multiple dust collection bins. The number of phosphate rock powder bins is greater than the number of biomass straw bins and dust collection bins.

[0012] Preferably, the roller pressing subsystem includes a high-intensity mixer, a mixture metering feeder, a double-roller briquetting machine, and a briquetting discharge belt conveyor, arranged in series. The feed end of the high-intensity mixer is connected to the discharge end of the raw material steep-angle belt conveyor, and the discharge end of the briquetting discharge belt conveyor is connected to the feed end of the screening and distribution subsystem. Preferably, a magnetic separator is also provided on the mixture metering feeder.

[0013] Preferably, the screening and distribution subsystem includes a fixed bar screen and a bottom material hopper arranged in parallel. The discharge chute of the fixed bar screen is connected to the feed end of the calcination and cooling subsystem via a raw material distributor. The discharge port of the bottom material hopper is connected to the feed end of the calcination and cooling subsystem via a bottom material distributor, and the connection position between the bottom material distributor and the feed end of the calcination and cooling subsystem is upstream of the connection position between the raw material distributor and the feed end of the calcination and cooling subsystem.

[0014] Preferably, the calcination cooling subsystem is an integrated calcination cooling machine, comprising, according to the material flow direction, a first drying section, a second drying section, a preheating section, a calcination homogenization section, a first cooling section, a second cooling section, an upper air hood covering them, and lower air boxes located at their respective bottoms and not connected to each other. Preferably, a material hopper is also provided below each lower air box. A double-layer ash discharge valve is also provided inside each lower air box.

[0015] Preferably, the finished product screening system includes a fixed screen and a three-way feeder. The feed end of the fixed screen is connected to the discharge end of the cooling section. The feed end of the three-way feeder is connected to the discharge chute of the fixed screen. The first discharge port of the three-way feeder is connected to the finished product belt conveyor. The second discharge port of the three-way feeder is connected to the feed end of the base material conveying mechanism. The discharge end of the base material conveying mechanism is connected to the feed end of the base material hopper. The base material conveying mechanism includes one or more belt conveyors.

[0016] As a preferred option, a natural phosphate rock bin is also provided on the base material conveying mechanism.

[0017] Preferably, the hot air circulation subsystem includes a cooling fan, a regenerating fan, a multi-tube dust collector, a main dust collector, and several air ducts. The cooling fan is connected to the bottom air inlet of the second cooling section via a first air duct and to the bottom air inlet of the first cooling section via a second air duct. The top air outlet of the second cooling section is connected to the top air inlet of the first drying section via a third air duct, and the bottom air outlet of the first drying section is connected to the air inlet of the cooling fan via a fourth air duct.

[0018] The top air outlet of the cooling section is connected to the top air inlet of the calcination homogenization section via the fifth air duct and to the top air inlet of the preheating section via the sixth air duct. The bottom air outlet of the calcination homogenization section is connected to the air inlet of the multi-tube dust collector via the seventh air duct. The air outlet of the multi-tube dust collector is connected to the top air inlet of the drying section via a regenerating fan and the eighth air duct. The bottom air outlet of the drying section is connected to the air inlet of the main dust collector via the ninth air duct. The bottom air outlet of the preheating section is connected to the air inlet of the main dust collector via the tenth air duct.

[0019] Preferably, the outlet of the main dust collector is also connected to the inlet of the desulfurization and denitrification device through the main exhaust fan and the eleventh duct, and the outlet of the desulfurization and denitrification device is directly discharged or connected to the chimney.

[0020] As a preferred option, a heating furnace is also installed on the fifth air duct.

[0021] Preferably, the system also includes a bulk material collection subsystem. The bulk material collection subsystem includes a bulk material belt conveyor, a bulk material bucket elevator, and a bulk material discharge chute, arranged in series. The feed end of the bulk material belt conveyor is connected to the under-screen discharge chute of the fixed screen, the discharge ports of all bulk material hoppers, and the under-screen discharge chute of the fixed bar screen. The discharge end of the bulk material discharge chute is connected to the feed end of the high-intensity mixer.

[0022] Preferably, the system also includes a dust collection subsystem. The dust collection subsystem includes a scraper conveyor, a dust bucket elevator, a dust silo, a combined crusher, and a humidifier.

[0023] Preferably, the bottom dust collection port of the main dust collector is connected to the feed end of the dust silo via a scraper conveyor and a dust bucket elevator. The dust silo and the dust outlet of the multi-tube dust collector are both connected to the feed end of the combined crusher. The discharge end of the combined crusher is connected to the feed end of the humidifier, and the discharge end of the humidifier is connected to the feed end of the dust collection ash silo via an ash conveying mechanism. Preferably, the ash conveying mechanism is a belt conveyor and / or a transport vehicle.

[0024] According to a second embodiment of the present invention, a method for calcining phosphate rock powder into briquettes is provided:

[0025] A method for calcining phosphate rock powder into briquettes, or a method for calcining phosphate rock powder into briquettes using the system described in the first embodiment, the method comprising:

[0026] 1) Phosphate ore is washed with water and rapidly dried to obtain phosphate ore powder, which is then stored in a phosphate ore powder silo. Modified dust is obtained by modifying phosphorus-containing dust using aluminosilicates and stored in a dust ash silo.

[0027] 2) Mix the phosphate rock powder, modified dust removal ash and biomass straw evenly to obtain a mixture.

[0028] 3) Add calcium hydroxide solution to the mixture, then press it into briquettes to obtain raw material briquettes. Sieve the raw material briquettes to obtain large and small raw material briquettes. The small raw material briquettes are returned to step 2) for further mixing. The large raw material briquettes proceed to the next process.

[0029] 4) The large raw material blocks obtained in step 3) are roasted. The roasted finished phosphate ore is then cooled and screened before being transported to the finished product warehouse for storage.

[0030] 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%. 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%. Preferably, the particle size of the phosphate rock powder is not greater than 8 mm, and more preferably not greater than 5 mm.

[0031] Preferably, in step 1), the modification treatment specifically involves adding aluminosilicate to the dust and performing a mixing and grinding process. Preferably, 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.

[0032] Preferably, in step 2), the mixing mass ratio of the phosphate rock powder, modified dust, and biomass straw is 70-90:5-10:10-20, more preferably 75-85:6-8:12-18. Preferably, the biomass straw pellets are modified biomass straw pellets treated with calcium hydroxide solution (the modification process specifically involves soaking and filtering with a 0.01-0.2 mol / L calcium hydroxide solution). The biomass straw is straw pellets with a particle size of no more than 5 mm, preferably straw pellets with a particle size of no more than 3 mm.

[0033] Preferably, in step 3), the large 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.

[0034] Preferably, in step 4), the calcination temperature is 1100-1300℃, more preferably 1150-1250℃, and the calcination time is 1-10h, more preferably 2-8h. The pellets conveyed to the finished product silo after sieving have a particle size of not less than 5mm, preferably not less than 7mm.

[0035] In this invention, several raw material silos (phosphate rock powder silos, biomass straw silos, and dust removal ash silos, etc.) are set up. The raw material silos are located above ground, while the batching equipment, including a quantitative feeder and a high-angle belt conveyor, is located below ground. A front-loading machine feeds the raw material silos, and a direct-drive quantitative feeder (frequency conversion speed regulation) is used for batching below the silos. All materials are automatically metered and batched, and the entire batching process is automatically controlled by a computer according to manually set proportions. To ensure thorough mixing and stable product quality, a horizontal high-power mixer is used for mixing. The mixed material is then fed into a roller briquetting machine via the direct-drive quantitative feeder. The mixed material from the mixer is then fed into the roller briquetting machine via a direct-drive quantitative feeder (frequency conversion speed regulation). The roller briquetting machine has adjustable speed and pressure, which can be adjusted as needed. The mixed material is pressed into flat blocks, which are then transported to a screening and distribution system via a briquetting discharge belt conveyor. The compressed briquettes are screened using a fixed-bar screening machine to remove lumps smaller than 15mm, which are then collected, transferred, and returned to the mixer. Qualified lumps larger than 15mm are evenly distributed onto the roasting device using a raw material distributor for drying and thermal consolidation. To protect the roasting device, a bottom layer is provided, primarily sourced from a natural phosphate rock lump silo. When natural phosphate rock lumps are insufficient, some finished product can be used as the bottom layer. A material layer thickness detection and leveling device is installed above the receiving end of the roasting device to ensure uniform material layer thickness. The raw briquettes undergo drying, thermal solidification, and cooling processes sequentially on the roasting device. A fixed screen is installed at the discharge end to screen the product, removing materials <5mm. After collection and transfer, these materials are returned to the mixing and pressing system for re-pressing. Materials ≥5mm are treated as finished products and transported to the electric furnace system via a finished product belt conveyor (for example, the roasting device uses a grate-type thermal solidification machine with specifications of 2.8×20m, a material layer thickness of 240mm on the grate (including an 80mm bottom layer), a total residence time of approximately 45–50 minutes, and a thermal solidification temperature of 1200℃).

[0036] In this invention, a hot air circulation subsystem employing cascaded heat utilization is incorporated into the calcination cooling subsystem. Cold air carries heat from the cooling section, generating high-temperature flue gas at varying temperatures. Waste heat from the system is recovered and used as heat for the initial drying and heat consolidation processes, thereby reducing fuel consumption. Raw material leakage at the calcination unit's feeding end, entrained loose material, and dust collected in the wind box are collectively referred to as loose material. This loose material will be collected, transported, and returned to the mixing system. During the cascaded utilization of the high-temperature flue gas, a high-temperature multi-tube dust collector is installed to remove dust from the flue gas to protect the circulating fan. After cascaded utilization, a portion of the flue gas will eventually form low-temperature flue gas. This portion, after dust removal by an electrostatic precipitator, is then sent to the desulfurization system by the main exhaust fan for further purification before being discharged. The dust collected by each dust collector will be concentrated in an ash silo and periodically transported by truck to the raw material storage yard for recycling. Crushing and humidification equipment is installed below the ash silo to ensure smooth discharge and prevent dust pollution during transportation. At the same time, a hot air duct heating furnace was added, using electric furnace gas as fuel to provide a stable heat source for the system.

[0037] In this invention, a biomass straw bin is added to the feed preparation subsystem. By distributing the biomass straw in the biomass blocks, a diffusion channel for internal moisture can be provided during drying, greatly increasing the rate of water vapor escape. At the same time, the biomass straw fibers in the biomass blocks can improve the adhesion between phosphate rock powder particles, thereby increasing the strength of the biomass blocks. In addition, the biomass straw in the biomass blocks provides some heat during subsequent roasting, which helps the material blocks to solidify at high temperatures, further improving their physical strength and chemical properties.

[0038] In this invention, a dust collection silo is added to the batching subsystem. The dust collection ash is collected from the yellow phosphorus production process and the hot air circulation subsystem of this system. Because the dust collection ash contains P2O5, direct discharge would lead to a waste of phosphorus resources. At the same time, it can further improve the grade of the briquetted material and will not cause losses during the roasting process. The P2O5 content can be increased by more than 1%. In addition, the modified dust collection ash, which is modified by using phosphate, is transported to the dust collection silo to participate in the mixing, which increases the binding property of the dust collection ash and improves the strength of the briquetted material. This eliminates the need to add binders and other auxiliary materials, realizes the recycling of valuable resources, and is also beneficial to environmental protection.

[0039] In this invention, the base material bin is connected to the natural phosphate rock bin, that is, natural phosphate rock lumps with a grade higher than that of low-grade phosphate rock powder are used as the base material. This mixing can improve the average grade of the finished product material blocks. 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 the base material increases the permeability and protects the roasting device. Selecting an appropriate base material thickness also improves the production capacity.

[0040] In this invention, the lump ore product prepared by the system of this invention has a concentrated and stable particle size distribution, good air permeability, and a low pulverization rate under the high-temperature reducing atmosphere of subsequent yellow phosphorus preparation, which can greatly reduce the amount of dust in phosphorus production. The finished lump ore product has low moisture content and low carbonate content, which can effectively reduce the power consumption of subsequent lump ore phosphorus production and improve the purity of phosphorus.

[0041] 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%.

[0042] 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 a certain strength to prevent excessive breakage during transportation and significant bursting during heat treatment. Therefore, this invention adds biomass straw during the batching process. The biomass straw is distributed throughout the raw material blocks, providing diffusion channels for internal moisture during drying, greatly increasing the rate of water vapor escape and effectively preventing the bursting of the raw material blocks caused by rapid evaporation of water molecules at high temperatures. Simultaneously, the fibers of the biomass straw in the raw material blocks can improve the adhesion between phosphate ore powder particles, thereby increasing the strength of the biomass blocks. Furthermore, the biomass straw in the biomass blocks provides some heat during subsequent roasting, contributing to the high-temperature solidification of the raw material blocks and further improving their physical strength and chemical properties.

[0043] 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.

[0044] 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.

[0045] In this invention, the height of the phosphate rock powder bin, the biomass straw bin, and the dust removal ash bin are each independently 1-300m, preferably 2-200m, more preferably 3-100m, and even more preferably 4-50m, for example, one of 1m, 2m, 3m, 4m, 5m, 6m, 7m, 8m, 9m, 10m, 12m, 15m, 18m, 20m, 25m, 30m, 35m, 40m, 50m, 80m, 100m, 120m, and 150m. Their inner diameters are each independently 1-200m, preferably 2-150m, more preferably 3-100m, and even more preferably 4-80m, for example, one of 1m, 2m, 3m, 4m, 5m, 6m, 7m, 8m, 9m, 10m, 12m, 15m, 18m, 20m, 25m, 30m, 35m, 40m, 50m, 80m, 100m, 120m, and 150m.

[0046] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0047] 1. This invention effectively solves the problem of resource waste caused by the inability to reuse phosphate rock powder in existing phosphate rock processing, and solves 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.

[0048] 2. The lump ore product prepared by this invention has good quality and high strength, is convenient for subsequent transportation, and has strong transportability. The lump ore product has low moisture content and low carbonate content, which effectively reduces the power consumption of subsequent lump ore phosphorus production and improves the purity of phosphorus.

[0049] 3. The present invention has a simple structural layout, orderly and reasonable system components, small site requirements, greatly saves land resources, can meet various terrain requirements, and has a wide range of applications. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the overall structure of the phosphate rock powder briquetting and roasting system described in this invention.

[0051] Figure reference numerals: 1: Batching subsystem; 101: Phosphate rock powder silo; 102: Biomass straw silo; 103: Dust removal ash silo; 104: Vibration anti-blocking device; 105: Slide valve; 106: Quantitative feeder; 107: Raw material steep-angle belt conveyor; 2: Roller pressing subsystem; 201: High-intensity mixer; 202: Mixed material quantitative feeder; 203: Double roller briquetting machine; 204: Briquetting discharge belt conveyor; 205: Magnetic separator; 3: Screening and distributing feeder System; 301: Fixed bar screener; 302: Bottom material silo; 303: Raw material distributor; 304: Bottom material distributor; 4: Calcination and cooling subsystem; 401: Drying stage 1; 402: Drying stage 2; 403: Preheating stage; 404: Calcination homogenization stage; 405: Cooling stage 1; 406: Cooling stage 2; 407: Upper air hood; 408: Lower air box; 409: Bulk hopper; 410: Double-layer ash discharge valve; 5: Finished product screening system; 501: Fixed bar screener 502: Screen; 503: Three-way feeder; 504: Finished product belt conveyor; 505: Bottom material conveying mechanism; 506: Natural phosphate ore bin; 6: Hot air circulation subsystem; 601: Cooling fan; 602: Regenerating fan; 603: Multi-tube dust collector; 604: Main dust collector; 605: Main exhaust fan; 606: Desulfurization and denitrification device; 607: Heating furnace; 7: Bulk material collection subsystem; 701: Bulk material belt conveyor; 702: Bulk material bucket elevator; 70 3: Bulk material discharge chute; 8: Dust collection subsystem; 801: Scraper conveyor; 802: Dust bucket elevator; 803: Dust silo; 804: Combined crusher; 805: Humidifier; L1: First air duct; L2: Second air duct; L3: Third air duct; L4: Fourth air duct; L5: Fifth air duct; L6: Sixth air duct; L7: Seventh air duct; L8: Eighth air duct; L9: Ninth air duct; L10: Tenth air duct; L11: Eleventh air duct. Detailed Implementation

[0052] 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.

[0053] A phosphate rock powder briquetting and roasting system includes a batching subsystem 1, a roller pressing subsystem 2, a sieving and distributing subsystem 3, a roasting and cooling subsystem 4, a finished product sieving subsystem 5, and a hot air circulation subsystem 6. The batching subsystem 1, roller pressing subsystem 2, sieving and distributing subsystem 3, roasting and cooling subsystem 4, and finished product sieving subsystem 5 are arranged in series according to the material flow direction. The hot air circulation subsystem 6 is located on the roasting and cooling subsystem 4.

[0054] Preferably, the batching subsystem 1 includes a phosphate rock powder silo 101, a biomass straw silo 102, and a dust removal ash silo 103 arranged in parallel. Each of the phosphate rock powder silo 101, biomass straw silo 102, and dust removal ash silo 103 is equipped with a vibration anti-blocking device 104 and a gate valve 105 at its bottom discharge port. Each gate valve 105 is also equipped with a quantitative feeder 106. The discharge end of all quantitative feeders 106 is connected to the feed end of the roller pressing subsystem 2 via a high-angle raw material belt conveyor 107.

[0055] Preferably, the batching subsystem 1 includes multiple phosphate rock powder bins 101, multiple biomass straw bins 102, and multiple dust collection bins 103. The number of phosphate rock powder bins 101 is greater than the number of biomass straw bins 102 and dust collection bins 103.

[0056] Preferably, the roller pressing subsystem 2 includes a high-intensity mixer 201, a mixture metering feeder 202, a double-roll briquetting machine 203, and a briquetting discharge belt conveyor 204, arranged in series. The feed end of the high-intensity mixer 201 is connected to the discharge end of the raw material steep-angle belt conveyor 107, and the discharge end of the briquetting discharge belt conveyor 204 is connected to the feed end of the screening and distribution subsystem 3. Preferably, a magnetic separator 205 is also provided on the mixture metering feeder 202.

[0057] Preferably, the screening and distribution subsystem 3 includes a fixed bar screen 301 and a bottom material hopper 302 arranged in parallel. The discharge chute of the fixed bar screen 301 is connected to the feed end of the calcination and cooling subsystem 4 via a raw material distributor 303. The discharge port of the bottom material hopper 302 is connected to the feed end of the calcination and cooling subsystem 4 via a bottom material distributor 304, and the connection position of the bottom material distributor 304 to the feed end of the calcination and cooling subsystem 4 is upstream of the connection position of the raw material distributor 303 to the feed end of the calcination and cooling subsystem 4.

[0058] Preferably, the calcination cooling subsystem 4 is an integrated calcination cooling machine, which, according to the material flow direction, includes a drying section 401, a drying section 402, a preheating section 403, a calcination homogenization section 404, a cooling section 405, a cooling section 406, an upper air hood 407 covering them, and lower air boxes 408 located at their respective bottoms and not connected to each other. Preferably, a material hopper 409 is also provided below each lower air box 408. A double-layer ash discharge valve 410 is also provided inside each lower air box 408.

[0059] Preferably, the finished product screening system 5 includes a fixed screen 501 and a three-way feeder 502. The feed end of the fixed screen 501 is connected to the discharge end of the cooling section 406. The feed end of the three-way feeder 502 is connected to the discharge chute of the fixed screen 501. The first discharge port of the three-way feeder 502 is connected to the finished product belt conveyor 503. The second discharge port of the three-way feeder 502 is connected to the feed end of the base material conveying mechanism 504. The discharge end of the base material conveying mechanism 504 is connected to the feed end of the base material hopper 302. The base material conveying mechanism 504 includes one or more belt conveyors.

[0060] As a preferred option, a natural phosphate rock bin 505 is also provided on the base material conveying mechanism 504.

[0061] Preferably, the hot air circulation subsystem 6 includes a cooling fan 601, a regenerating fan 602, a multi-tube dust collector 603, a main dust collector 604, and several air ducts. The cooling fan 601 is connected to the bottom air inlet of the second cooling section 406 via a first air duct L1 and to the bottom air inlet of the first cooling section 405 via a second air duct L2. The top air outlet of the second cooling section 406 is connected to the top air inlet of the first drying section 401 via a third air duct L3, and the bottom air outlet of the first drying section 401 is connected to the air inlet of the cooling fan 601 via a fourth air duct L4.

[0062] The top air outlet of the cooling section 405 is connected to the top air inlet of the calcination homogenization section 404 via the fifth air duct L5 and to the top air inlet of the preheating section 403 via the sixth air duct L6. The bottom air outlet of the calcination homogenization section 404 is connected to the air inlet of the multi-tube dust collector 603 via the seventh air duct L7. The air outlet of the multi-tube dust collector 603 is connected to the top air inlet of the drying section 402 via the regenerating fan 602 and the eighth air duct L8. The bottom air outlet of the drying section 402 is connected to the air inlet of the main dust collector 604 via the ninth air duct L9. The bottom air outlet of the preheating section 403 is connected to the air inlet of the main dust collector 604 via the tenth air duct L10.

[0063] Preferably, the outlet of the main dust collector 604 is also connected to the inlet of the desulfurization and denitrification device 606 through the main exhaust fan 605 and the eleventh duct L11, and the outlet of the desulfurization and denitrification device 606 is directly discharged or connected to the chimney.

[0064] As a preferred option, a heating furnace 607 is also installed on the fifth air duct L5.

[0065] Preferably, the system also includes a bulk material collection subsystem 7. The bulk material collection subsystem 7 includes a bulk material belt conveyor 701, a bulk material bucket elevator 702, and a bulk material discharge chute 703, arranged in series. The feed end of the bulk material belt conveyor 701 is connected to the under-screen discharge chute of the fixed screen 501, the discharge ports of all bulk material hoppers 409, and the under-screen discharge chute of the fixed bar screen 301. The discharge end of the bulk material discharge chute 703 is connected to the feed end of the high-intensity mixer 201.

[0066] Preferably, the system also includes a dust collection subsystem 8. The dust collection subsystem 8 includes a scraper conveyor 801, a dust bucket elevator 802, a dust silo 803, a combined crusher 804, and a humidifier 805.

[0067] Preferably, the bottom dust collection port of the main dust collector 604 is connected to the feed end of the dust silo 803 via a scraper conveyor 801 and a dust bucket elevator 802. The dust outlets of both the dust silo 803 and the multi-tube dust collector 603 are connected to the feed end of the combined crusher 804. The discharge end of the combined crusher 804 is connected to the feed end of the humidifier 805, and the discharge end of the humidifier 805 is connected to the feed end of the dust collection ash silo 103 via an ash conveying mechanism. Preferably, the ash conveying mechanism is a belt conveyor and / or a transport vehicle.

[0068] Example 1

[0069] like Figure 1 As shown, a phosphate rock powder briquetting and roasting system includes a batching subsystem 1, a roller pressing subsystem 2, a sieving and distributing subsystem 3, a roasting and cooling subsystem 4, a finished product sieving subsystem 5, and a hot air circulation subsystem 6. According to the material flow direction, the batching subsystem 1, roller pressing subsystem 2, sieving and distributing subsystem 3, roasting and cooling subsystem 4, and finished product sieving subsystem 5 are connected in series. The hot air circulation subsystem 6 is installed on the roasting and cooling subsystem 4.

[0070] Example 2

[0071] The embodiment 1 is repeated, except that the batching subsystem 1 includes a phosphate rock powder silo 101, a biomass straw silo 102, and a dust removal ash silo 103 arranged in parallel. Vibration anti-blocking devices 104 and gate valves 105 are installed at the bottom discharge ports of the phosphate rock powder silo 101, biomass straw silo 102, and dust removal ash silo 103. A quantitative feeder 106 is also installed at each gate valve 105. The discharge end of all quantitative feeders 106 is connected to the feed end of the roller pressing subsystem 2 via a high-angle raw material belt conveyor 107.

[0072] Example 3

[0073] Example 2 is repeated, except that the batching subsystem 1 includes multiple phosphate rock powder bins 101, multiple biomass straw bins 102, and multiple dust collection bins 103. The number of phosphate rock powder bins 101 is greater than the number of biomass straw bins 102 and dust collection bins 103.

[0074] Example 4

[0075] The embodiment 3 is repeated, except that the roller pressing subsystem 2 includes a high-intensity mixer 201, a mixture metering feeder 202, a double-roller briquetting machine 203, and a briquetting discharge belt conveyor 204 arranged in series. The feed end of the high-intensity mixer 201 is connected to the discharge end of the raw material steep-angle belt conveyor 107, and the discharge end of the briquetting discharge belt conveyor 204 is connected to the feed end of the screening and distribution subsystem 3.

[0076] Example 5

[0077] Example 4 is repeated, except that an iron remover 205 is also provided on the mixed material quantitative feeder 202.

[0078] Example 6

[0079] The embodiment 5 is repeated, except that the screening and distribution subsystem 3 includes a fixed bar screen 301 and a bottom material hopper 302 arranged in parallel. The discharge chute of the fixed bar screen 301 is connected to the feed end of the calcination and cooling subsystem 4 through a raw material distributor 303. The discharge port of the bottom material hopper 302 is connected to the feed end of the calcination and cooling subsystem 4 through a bottom material distributor 304, and the connection position of the bottom material distributor 304 to the feed end of the calcination and cooling subsystem 4 is upstream of the connection position of the raw material distributor 303 to the feed end of the calcination and cooling subsystem 4.

[0080] Example 7

[0081] Example 6 is repeated, except that the roasting and cooling subsystem 4 is an integrated roasting and cooling machine, which includes a drying section 401, a drying section 402, a preheating section 403, a roasting and homogenizing section 404, a cooling section 405, a cooling section 406, an upper air cover 407 covering them, and a lower air box 408 located at their respective bottoms and not connected to each other.

[0082] Example 8

[0083] The embodiment 7 is repeated, except that a bulk material hopper 409 is also provided below each of the lower air boxes 408. A double-layer ash discharge valve 410 is also provided inside each of the lower air boxes 408.

[0084] Example 9

[0085] The embodiment 8 is repeated, except that the finished product screening system 5 includes a fixed screen 501 and a three-way feeder 502. The feed end of the fixed screen 501 is connected to the discharge end of the cooling section 406. The feed end of the three-way feeder 502 is connected to the discharge chute of the fixed screen 501. The first discharge port of the three-way feeder 502 is connected to the finished product belt conveyor 503. The second discharge port of the three-way feeder 502 is connected to the feed end of the base material conveying mechanism 504. The discharge end of the base material conveying mechanism 504 is connected to the feed end of the base material silo 302. The base material conveying mechanism 504 includes multiple belt conveyors.

[0086] Example 10

[0087] Example 9 is repeated, except that a natural phosphate rock bin 505 is also provided on the base material conveying mechanism 504.

[0088] Example 11

[0089] The embodiment 10 is repeated, except that the hot air circulation subsystem 6 includes a cooling fan 601, a regenerating fan 602, a multi-tube dust collector 603, a main dust collector 604, and several air ducts. The cooling fan 601 is connected to the bottom air inlet of the second cooling section 406 via a first air duct L1 and to the bottom air inlet of the first cooling section 405 via a second air duct L2. The top air outlet of the second cooling section 406 is connected to the top air inlet of the first drying section 401 via a third air duct L3, and the bottom air outlet of the first drying section 401 is connected to the air inlet of the cooling fan 601 via a fourth air duct L4.

[0090] The top air outlet of the cooling section 405 is connected to the top air inlet of the calcination homogenization section 404 via the fifth air duct L5 and to the top air inlet of the preheating section 403 via the sixth air duct L6. The bottom air outlet of the calcination homogenization section 404 is connected to the air inlet of the multi-tube dust collector 603 via the seventh air duct L7. The air outlet of the multi-tube dust collector 603 is connected to the top air inlet of the drying section 402 via the regenerating fan 602 and the eighth air duct L8. The bottom air outlet of the drying section 402 is connected to the air inlet of the main dust collector 604 via the ninth air duct L9. The bottom air outlet of the preheating section 403 is connected to the air inlet of the main dust collector 604 via the tenth air duct L10.

[0091] Example 12

[0092] Example 11 is repeated, except that the air outlet of the main dust collector 604 is also connected to the air inlet of the desulfurization and denitrification device 606 through the main exhaust fan 605 and the eleventh air duct L11, and the air outlet of the desulfurization and denitrification device 606 is connected to the chimney.

[0093] Example 13

[0094] The embodiment 12 is repeated, except that a heating furnace 607 is also installed on the fifth air duct L5.

[0095] Example 14

[0096] The system repeats Embodiment 13, except that it also includes a bulk material collection subsystem 7. The bulk material collection subsystem 7 includes a bulk material belt conveyor 701, a bulk material bucket elevator 702, and a bulk material discharge chute 703, arranged in series. The feed end of the bulk material belt conveyor 701 is connected to the under-screen discharge chute of the fixed screen 501, the discharge ports of all bulk material hoppers 409, and the under-screen discharge chute of the fixed bar screen 301. The discharge end of the bulk material discharge chute 703 is connected to the feed end of the high-intensity mixer 201.

[0097] Example 15

[0098] The system is a repeat of embodiment 14, except that it also includes a dust collection subsystem 8. The dust collection subsystem 8 includes a scraper conveyor 801, a dust bucket elevator 802, a dust silo 803, a combined crusher 804, and a humidifier 805.

[0099] Example 16

[0100] Example 15 is repeated, except that the bottom dust collection port of the main dust collector 604 is connected to the feed end of the dust silo 803 via a scraper conveyor 801 and a dust bucket elevator 802. The dust outlets of the dust silo 803 and the multi-tube dust collector 603 are both connected to the feed end of the combined crusher 804. The discharge end of the combined crusher 804 is connected to the feed end of the humidifier 805. The discharge end of the humidifier 805 is connected to the feed end of the dust collection ash silo 103 via an ash conveying mechanism.

[0101] Example 17

[0102] Repeat Example 16, except that the ash transport mechanism is a transport vehicle.

[0103] Example 18

[0104] A method for calcining phosphate rock powder using the system described in Example 17, the method comprising:

[0105] 1) Phosphate ore is washed with water and rapidly dried to obtain phosphate ore powder, which is then stored in a phosphate ore powder silo. Modified dust is obtained by modifying phosphorus-containing dust using aluminosilicates and stored in a dust ash silo.

[0106] 2) Mix the phosphate rock powder, modified dust removal ash and biomass straw evenly to obtain a mixture.

[0107] 3) Add calcium hydroxide solution to the mixture, then press it into briquettes to obtain raw material briquettes. Sieve the raw material briquettes to obtain large and small raw material briquettes. The small raw material briquettes are returned to step 2) for further mixing. The large raw material briquettes proceed to the next process.

[0108] 4) The large raw material blocks obtained in step 3) are roasted. The roasted finished phosphate ore is then cooled and screened before being transported to the finished product warehouse for storage.

[0109] 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%. 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%. The particle size of the phosphate rock powder is no greater than 8 mm.

[0110] In step 2), the mixing mass ratio of the phosphate rock powder, modified dust removal ash, and biomass straw is 70-90:5-10:10-20.

[0111] In step 3), the large raw material block has a flat block structure with an average particle size of not less than 15 mm.

[0112] In step 4), the roasting temperature is 1100-1300℃, and the roasting time is 1-10 hours. The pellets conveyed to the finished product silo after sieving have a particle size of not less than 5mm.

[0113] Application Example 1

[0114] Phosphate rock powder (P2O5 content 14.39%) was crushed and then washed three times (liquid-solid mass ratio of 3:1 in each wash). After washing, the powder was sieved using a 5mm screen, and the undersize material was collected and microwave-dried to obtain phosphate rock powder with a moisture content of approximately 8.1%. Dust collected during yellow phosphorus production (P2O5 content 26.51%) was mixed and ground with potassium feldspar (added at 2.2% of the dust mass) to obtain modified dust. Corn stalks were crushed to a particle size of less than 2mm to obtain stalk pellets.

[0115] Phosphate rock powder, modified dust collector ash, and corn stalk pellets were mixed in a mass ratio of 80:7.5:12.5 to obtain a mixture. During the mixing process, 2.5% (based on the total mass of solids), 0.015 mol / L calcium hydroxide solution was added and stirred until homogeneous to obtain a uniform mixture. Then, a 5t / cm³ flow rate was used. 2 The mixture is compressed under pressure and then sieved through a 15mm sieve to obtain large, flat raw material blocks measuring 35×25×15mm. These large raw material blocks (using natural phosphate ore as a base material) are then fed into a belt roaster and sequentially pass through a drying section, a drying section, a preheating section, a roasting homogenization section, a cooling section, a cooling section, and a fixed sieve to obtain finished phosphate ore with a particle size greater than 5mm.

[0116] Application Example 2,

[0117] Example 1 was repeated, except that the mass ratio of phosphate rock powder, modified dust removal ash, and corn stalk pellets was 79:6:15.

[0118] Application Example 3

[0119] The application of Example 1 was repeated, except that the corn stalk particles were first soaked in a 0.02 mol / L calcium hydroxide solution for 1 hour and then filtered to obtain modified stalk particles, which were then used in the mixing process.

[0120] Application Example 4

[0121] Repeat Example 1, except that corn stalk pellets are replaced with sorghum stalk pellets.

[0122] Application Example 5

[0123] Repeat Example 1, except that the aluminosilicate is montmorillonite.

[0124] Comparative Example 1

[0125] The application of Example 1 was repeated, except that the dust was not modified.

[0126] Comparative Example 2

[0127] Repeat Example 1, except that the mixture does not contain biomass straw.

[0128] Comparative Example 3

[0129] The same method as Example 1 was used, except that the mass ratio of phosphate rock powder, modified dust removal ash, and corn stalk pellets was 90:6:4.

[0130] Comparative Example 4

[0131] Example 1 was repeated, except that the mass ratio of phosphate rock powder, modified dust removal ash, and corn stalk pellets was 71:6:23.

[0132] 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:

[0133]

Claims

1. A method for calcining phosphate rock powder into briquettes, characterized in that: The method includes: 1) Phosphate ore is washed with water and rapidly dried to obtain phosphate ore powder, which is then stored in a phosphate ore powder silo. Modified dust is obtained by modifying phosphorus-containing dust using aluminosilicates and stored in a dust ash silo. The phosphate ore is low-grade phosphate ore, 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%, and MgO content... The modified dust contains 1-2% P2O5, 0.1-0.3% F, and 0.5-0.8% S; the chemical composition of the modified dust 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%. 2) Mix phosphate rock powder, modified dust removal ash and biomass straw evenly to obtain a mixture; the mixing mass ratio of phosphate rock powder, modified dust removal ash and biomass straw is 70-90:5-10:10-20. 3) Add calcium hydroxide solution to the mixture, then press it into briquettes to obtain raw material briquettes. The raw material briquettes are then sieved to obtain large raw material briquettes and small raw material briquettes. The small raw material briquettes are returned to step 2) to participate in the mixing. The large raw material briquettes are then sent to the next process. 4) The large raw material blocks obtained in step 3) are roasted. The roasted finished phosphate ore is then cooled and screened before being transported to the finished product warehouse for storage.

2. The method according to claim 1, characterized in that: In step 1), the particle size of the phosphate rock powder is no greater than 8 mm.

3. The method according to claim 2, characterized in that: In step 1), the particle size of the phosphate rock powder is no greater than 5 mm.

4. The method according to claim 1, characterized in that: In step 2), the mixing mass ratio of the phosphate rock powder, modified dust removal ash, and biomass straw is 75-85:6-8:12-18.

5. The method according to any one of claims 1-4, characterized in that: The biomass straw is modified biomass straw pellets that have been treated with calcium hydroxide solution.

6. The method according to claim 1, characterized in that: In step 3), the large raw material block has a flat block structure with an average particle size of not less than 15 mm.

7. The method according to claim 6, characterized in that: In step 3), the average particle size of the large raw material block is 15-35 mm.

8. The method according to claim 1, characterized in that: In step 4), the roasting temperature is 1100-1300℃, the roasting time is 1-10h, and the pellet size of the pellets transported to the finished product silo after sieving is not less than 5mm.

9. The method according to claim 8, characterized in that: In step 4), the roasting temperature is 1150-1250℃, the roasting time is 2-8h, and the pellet size of the pellets transported to the finished product silo after screening is not less than 7mm.

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