A system and method for producing phosphorus ore by vertical furnace roasting

Abstract

The application discloses a kind of phosphate rock shaft furnace roasting production system and method, the system includes phosphate rock pretreatment unit, auxiliary material distribution unit, pelletizing unit, screening distribution material unit, shaft furnace roasting unit, cooling unit and finished product processing unit.The application can be obtained in the production process of natural phosphate rock block ore by enterprise and the low-grade powder ore produced is pretreated as pelletizing raw material, and the prepared pellet can be directly used for yellow phosphorus production after shaft furnace roasting treatment.The application can effectively utilize phosphate rock powder ore resources on the one hand, alleviate the problem of lack of raw materials for yellow phosphorus enterprises, on the other hand, can also effectively reduce raw material cost and save land resources, both in line with national industrial policy and resource development strategy, and also has important significance for yellow phosphorus production in China.

Description

Technical Field

[0001] This invention relates to phosphate rock production and processing equipment, specifically to a phosphate rock vertical furnace roasting production system and method, 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] Although my country has large phosphate rock reserves, its resources are mainly low- to medium-grade phosphate rock, with limited rich ore resources. According to statistics, the average grade of my country's currently recoverable phosphate rock reserves is 23%, lower than the global average of 30%. Among these, low-grade phosphate rock reserves with a P2O5 content below 20% account for over 60%, while high-grade phosphate rock reserves with a content above 30% account for less than 10%. 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.

[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 the production of yellow phosphorus 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 problem of resource waste caused by the shortage of phosphate rock ore for yellow phosphorus production and the underutilization of high-quality phosphate rock powder during the production of natural phosphate rock ore, this invention provides a phosphate rock vertical shaft furnace roasting production system and method. This system pre-treats low-grade phosphate rock powder generated during the production of natural phosphate rock ore and uses it as pelletizing raw material. The resulting pellets, after vertical shaft furnace roasting, can be directly used in yellow phosphorus production. This system effectively utilizes phosphate rock powder resources, 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] According to a first embodiment of the present invention, a phosphate rock roasting production system is provided:

[0008] A phosphate rock roasting production system includes a phosphate rock pretreatment unit, an auxiliary material distribution unit, a pelletizing unit, a screening and distribution unit, a roasting unit, a cooling unit, and a finished product processing unit. The phosphate rock pretreatment unit and the auxiliary material distribution unit are arranged in parallel, and according to the material flow, both the phosphate rock pretreatment unit and the auxiliary material distribution unit are connected in series with the pelletizing unit, the screening and distribution unit, the roasting unit, the cooling unit, and the finished product processing unit.

[0009] Preferably, the phosphate rock pretreatment unit includes a high-calcium phosphate rock powder silo, a high-silica phosphate rock powder silo, a drying device, and a grinding device. A phosphate rock powder feeding and conveying mechanism is connected to the feed ends of the high-calcium phosphate rock powder silo and the high-silica phosphate rock powder silo, respectively, to transport phosphate rock powder from the outside to the high-calcium phosphate rock powder silo or the high-silica phosphate rock powder silo for pre-storage. The discharge ends of the high-calcium phosphate rock powder silo and the high-silica phosphate rock powder silo are connected to the feed ends of the drying device, the grinding device, and the pelletizing unit, respectively, via a phosphate rock powder discharge conveying mechanism. The discharge end of the drying device is connected to the feed end of the grinding device via a drying discharge conveying mechanism. The discharge end of the grinding device is connected to the feed end of the pelletizing unit via a grinding discharge conveying mechanism. Preferably, a discharge vibrating hopper, a disc feeder, and a quantitative feeder are also independently and sequentially arranged between the discharge ends of the high-calcium phosphate rock powder silo and the high-silica phosphate rock powder silo and the feed ends of the phosphate rock powder discharge conveying mechanism.

[0010] Preferably, the ore powder feeding conveying mechanism, ore powder discharging conveying mechanism, drying discharging conveying mechanism and grinding discharging conveying mechanism each independently include one or more belt conveyors, and each belt conveyor may or may not be equipped with a pear-shaped unloader.

[0011] Preferably, the phosphate rock pretreatment unit further includes a temporary phosphate rock storage yard, which is connected to the discharge end of the phosphate rock feeding and conveying mechanism. A grab crane is also installed on the temporary phosphate rock storage yard. The grab crane transports the stored phosphate rock to high-calcium phosphate rock silos and / or high-silica phosphate rock silos.

[0012] Preferably, the drying apparatus includes a cylindrical dryer, a wet scrubber, a drying fan, and a drying exhaust stack. The cylindrical dryer, wet scrubber, drying fan, and drying exhaust stack are connected in series according to the airflow direction. The discharge end of the cylindrical dryer is connected to the feed end of the drying discharge conveying mechanism. Preferably, the drying apparatus also includes a hot air furnace, a sedimentation tank, and a sludge drying device. The hot air outlet of the hot air furnace is connected to an air inlet located on the side of the cylindrical dryer's material discharge end via a hot air pipe. The dust outlet of the wet scrubber is connected to the feed inlet of the sedimentation tank, the sludge discharge outlet of the sedimentation tank is connected to the feed inlet of the sludge drying device, and the discharge outlet of the sludge drying device is connected to a temporary mineral powder stockpile via a dry sludge conveying mechanism.

[0013] Preferably, the grinding device includes a roller screen, a grinding buffer chamber, and a high-pressure roller mill arranged in series. The feed end of the roller screen is connected to the discharge ends of the ore powder discharge conveying mechanism and the drying discharge conveying mechanism. The discharge end of the high-pressure roller mill is connected to the feed end of the grinding discharge conveying mechanism. Preferably, the discharge end of the grinding buffer chamber is connected to the feed end of the high-pressure roller mill and the feed end of the grinding discharge conveying mechanism respectively through a reversible quantitative feeder. More preferably, a vibration anti-clogging device is also provided on the side wall of the discharge end of the grinding buffer chamber. An iron remover is also provided on the roller screen.

[0014] Preferably, the auxiliary material delivery unit includes a dust bin, a bentonite bin, and a biomass straw bin arranged in parallel. The discharge ends of the dust bin and the bentonite bin are independently and sequentially connected in series with a vibration anti-blocking device, a rotary valve, a screw feeder, and a sealed belt scale. The discharge ends of all sealed belt scales are connected to the mineral powder discharge conveying mechanism. The discharge end of the biomass straw bin is sequentially connected in series with a discharge vibrating hopper, a disc feeder, and a quantitative feeder. The discharge end of the quantitative feeder is connected to the mineral powder discharge conveying mechanism.

[0015] Preferably, the pelletizing unit includes a high-intensity mixer, a mixing silo, and a disc pelletizer arranged in series. The feed end of the high-intensity mixer is connected to the discharge end of the mineral powder discharge conveying mechanism. The discharge end of the disc pelletizer is connected to the screening and distribution unit via a green pellet conveying mechanism. A discharge vibrating hopper, a disc feeder, and a quantitative feeder are also arranged in series between the mixing silo and the disc pelletizer. Preferably, the green pellet conveying mechanism includes one or more belt conveyors.

[0016] Preferably, the pelletizing unit includes multiple sets of mixing bins arranged in parallel and a disc pelletizer.

[0017] Preferably, the screening and distribution unit includes a roller screen and a natural phosphate ore bin. The feed end of the roller screen is connected to the discharge end of the green ball conveying mechanism. Both the large ball discharge end and the small ball discharge end of the roller screen are connected to the feed end of the mixing bin via a return ball belt conveyor (the discharge end of the roller screen is generally equipped with crushing rollers to crush the large and small balls, allowing them to directly enter the mixing bin). The medium ball discharge end of the roller screen is connected to the feed end of the vertical shaft furnace roasting unit via a green ball feeding conveyor. The natural phosphate ore bin is arranged parallel to the roller screen, and its discharge end is connected to the green ball feeding conveyor via a large-angle lump ore belt conveyor. Preferably, the green ball feeding conveyor includes one or more belt conveyors.

[0018] Preferably, the vertical shaft furnace roasting unit includes a shuttle feeder, a vertical shaft furnace, an electric vibrating feeder, and a hot chain conveyor, arranged in series. The feed end of the shuttle feeder is connected to the discharge end of the green ball feeding and conveying mechanism. The discharge end of the hot chain conveyor is connected to the feed end of the cooling unit. Preferably, a toothed roller crusher is also provided between the discharge end of the vertical shaft furnace and the electric vibrating feeder. Preferably, a combustion fan and a cooling fan are also provided on one side of the vertical shaft furnace. The combustion fan is connected to the combustion chamber at the top of the vertical shaft furnace through a combustion fan duct, and the cooling fan is connected to the cooling chamber at the bottom of the vertical shaft furnace through a cooling fan duct.

[0019] Preferably, the cooling unit is a multi-stage belt cooler, which includes, in sequence according to the material flow, a first-stage belt cooler, a second-stage belt cooler, a third-stage belt cooler, a fourth-stage belt cooler, and a fan hood covering them. The feed end of the first-stage belt cooler is connected to the discharge end of the hot chain conveyor, and the discharge end of the fourth-stage belt cooler is connected to the feed end of the finished product processing unit.

[0020] Preferably, the lower air inlets of the cooling sections three and four are each connected to a blower via independent ducts. The upper air outlet of the cooling section four is connected to the upper air inlet of the cooling section two via a first circulating duct, and the lower air outlet of the cooling section two is connected to the combustion air blower of the vertical furnace via a second circulating duct. The upper air outlet of the cooling section three is connected to the upper air inlet of the cooling section one via a third circulating duct, and the lower air outlet of the cooling section one is connected to the air inlet of the cylindrical dryer via a fourth circulating duct. Preferably, an exhaust fan is also installed on the fourth circulating duct.

[0021] Preferably, the finished product processing unit includes a finished product screen, a finished product bin, and a powder bin. The feed end of the finished product screen is connected to the discharge end of the cooling four-section unit. The discharge end of the finished product screen above the screen is connected to the feed end of the finished product bin, and the discharge end of the finished product screen below the screen is connected to the feed end of the powder bin. Both the discharge ends of the finished product bin and the powder bin are equipped with electro-hydraulic sector valves.

[0022] Preferably, the finished product processing unit includes multiple finished product bins, and the discharge end of the finished product screen is connected to the feed ends of the multiple finished product bins through a screen material conveying mechanism. The screen material conveying mechanism includes one or more belt conveyors and / or heavy-duty unloading vehicles.

[0023] Preferably, the vertical shaft furnace roasting unit further includes a main flue gas dust collector, the inlet of which is connected to the top flue gas outlet of the vertical shaft furnace via a flue gas conveying pipe. The exhaust outlet of the main flue gas dust collector is connected to the chimney via an exhaust pipe, on which a main exhaust fan and a desulfurization and denitrification device are sequentially installed. The bottom dust outlet of the main flue gas dust collector is connected to the feed end of the dust silo via a pneumatic conveying pump and a pneumatic dust conveying pipe.

[0024] According to a second embodiment of the present invention, a method for producing phosphate rock by vertical shaft roasting is provided:

[0025] A method for producing phosphate rock by vertical shaft roasting, or a method for producing phosphate rock by vertical shaft roasting using the system described in the first embodiment, the method comprising:

[0026] 1) After pre-treating the phosphate rock powder through the phosphate rock pre-treatment unit, high-calcium phosphate rock powder and high-silicon phosphate rock powder are obtained; then the high-calcium phosphate rock powder and high-silicon phosphate rock powder are mixed to obtain mixed mineral powder.

[0027] 2) Mix the mixed mineral powder, dust (dust collected by the system), bentonite, and biomass straw pellets in proportion to obtain a pelletizing mixture (average particle size not greater than 5mm, preferably not greater than 4mm).

[0028] 3) Add the pelletizing mixture to the pelletizer to form pellets, and screen the obtained green pellets to obtain large pellets, seed pellets and small pellets; the large and small pellets are crushed and returned to step 2) to participate in the mixing; the medium pellets enter the next process.

[0029] 4) The pellets obtained in step 3) are fed into a vertical furnace for roasting. The roasted pellets are then cooled by a belt cooler and screened by a screening machine before being transported to the finished product warehouse for storage.

[0030] Preferably, in step 1), the high-calcium phosphate rock powder is a phosphate rock powder with a P2O5 content of no more than 15 wt%, a CaO content of no less than 40 wt%, and a moisture content of 6-10%. More preferably, it is a phosphate rock powder with a P2O5 content of 10-15 wt%, a CaO content of 45-55 wt%, and a moisture content of 8-9%.

[0031] Preferably, in step 1), the high-silica phosphate rock powder is a phosphate rock powder with a P2O5 content of no more than 15 wt%, a SiO2 content of no less than 40 wt%, and a water content of 6-10%; more preferably, it is a phosphate rock powder with a P2O5 content of 10-15 wt%, a SiO2 content of 45-55 wt%, and a water content of 8-9%.

[0032] Preferably, in step 1), the mixing mass ratio of high-calcium phosphate rock powder to high-silica phosphate rock powder is 1.2-1.6:1, more preferably 1.3-1.45:1. The average particle size of the mixed mineral powder is not greater than 0.15 mm, more preferably not greater than 0.125 mm.

[0033] Preferably, in step 2), the mixing mass ratio of the mixed mineral powder, dust, bentonite, and biomass straw pellets is 92-98:3-8:1-5:0.5-2 (preferably 94-97:4-7:2-4:1-1.5). Preferably, the biomass straw pellets are modified biomass straw pellets treated with calcium hydroxide solution.

[0034] Preferably, in step 3), the particle size of the medium sphere is 5-20 mm, preferably 8-16 mm; spheres with a particle size larger than the medium sphere are called large spheres, and spheres with a particle size smaller than the medium sphere are called small spheres.

[0035] 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 pellet size of the pellets transported to the finished product silo after sieving is not less than 5mm, more preferably not less than 7mm.

[0036] In this invention, phosphate rock powder is sorted into high-calcium phosphate rock powder and high-silica phosphate rock powder by a phosphate rock pretreatment unit, and then stored and distributed separately. During the pretreatment process, the high-calcium phosphate rock powder and the high-silica phosphate rock powder are selectively dried or not, depending on their respective moisture content. The drying process is generally carried out in a cylindrical dryer, where hot air from a hot air furnace and / or a subsequent cooling section comes into counter-current contact with the material for heat exchange. Generally, the moisture content of the dried high-calcium phosphate rock powder and the high-silica phosphate rock powder is controlled to be 6-10% (preferably 8-9%). Furthermore, the high-calcium phosphate rock powder and the high-silica phosphate rock powder can be selectively subjected to high-pressure roller milling based on the original particle size of the phosphate rock powder to obtain fine phosphate rock powder with an average particle size of no more than 0.15 mm (preferably no more than 0.125 mm) as pelletizing raw material. After drying, the hot air is cleaned by a dust collector, and the clean flue gas is discharged through an induced draft fan and exhaust stack. The collected dust is transported by truck to a temporary phosphate rock powder stockpile. The drying hot air mainly comes from the cooling section. When the temperature is insufficient, heat is supplemented by a hot blast stove. The hot blast stove uses blast furnace gas as fuel and generates hot flue gas at 750-900℃ for the cylindrical dryer.

[0037] In this invention, the chemical composition of the high-calcium phosphate rock powder is generally as follows: P2O5 content 10-15%, SiO2 content 10%-15%, CaO content 40%-55%, Fe2O3 content 0.5%-1%, Al2O3 content 3%-5%, MgO content 1%-2%, F content 0.1%-0.3%, and S content 0.5%-0.8%. The chemical composition of the high-silica phosphate rock powder is generally as follows: P2O5 content 10-15%, SiO2 content 40%-55%, CaO content 20%-25%, 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%.

[0038] In this invention, to ensure the safe operation of the high-pressure roller mill, an iron removal device and a debris screen are installed before the phosphate rock powder enters the roller mill. After removing iron blocks and large-sized debris, the powder falls into a buffer silo and is fed into the high-pressure roller mill by a reversible quantitative feeder below the silo. After high-pressure roller milling, the powder enters the ore powder discharge and conveying mechanism. A bypass is provided in the high-pressure roller milling process. When the raw material particle size is very fine and high-pressure roller milling is not required, the powder can be directly fed into the ore powder discharge and conveying mechanism by the reversible quantitative feeder through the bypass.

[0039] In this invention, a temporary stockpile of mineral powder is also provided. Phosphate rock powder with high calcium content and high silicon content can also be transported by truck from outside to the temporary stockpile of high-calcium and high-silicon phosphate rock powder. A grab crane is used to stack the phosphate rock powder in the temporary stockpile of high-calcium and high-silicon phosphate rock powder, and the grab crane can also be used to grab the phosphate rock powder and move it to the phosphate rock powder silo. Different types of phosphate rock powder are stored in the phosphate rock powder silo. The vibrating bucket under the silo feeds the phosphate rock powder to the powder disc feeder, and then to the powder quantitative feeder. The material is automatically batched. Each phosphate rock powder silo is equipped with a level gauge to stabilize the discharge rate and achieve precise batching. The entire batching process is automatically controlled by a computer according to the manually set ratio. If the material in the current batch has a very fine particle size and a very low moisture content, then no drying process is required; if the material in the current batch has a very coarse particle size and a very low moisture content, then skip the drying process and proceed directly to roller milling; if the material in the current batch has a high particle size and moisture content, then it needs to be dried in a cylindrical dryer, and the dried material is then judged whether to undergo roller milling based on its particle size.

[0040] In this invention, high-calcium and high-silicon phosphate rock are mixed and subjected to high-pressure roller milling. After being pressed by the high-pressure roller mill, the specific surface area of ​​the mineral powder is larger, which is beneficial for pelletizing and also improves the pelletizing strength. High-silicon phosphate rock has low hardness and is easier to roller mill, but after fine grinding, it has poor hydrophilicity, a low static pelletizing index, and weak pelletizing ability. High-calcium phosphate rock has high hardness and is more difficult to grind, but after fine grinding, it has good hydrophilicity, a high static pelletizing index, and good pelletizing ability. The specific surface area of ​​the mineral powder after mixed roller milling generally exceeds 2200 cm². 2 / g, significantly improving the pelletizing index. By combining high-calcium phosphate rock powder with low-silica phosphate rock powder, the roller mill process uses material to grind material, reducing roller mill energy consumption; at the same time, it can effectively adjust the acidity, so that the acidity of the pellets obtained after pelleting is greater than 0.95, which can further reduce the amount of flux added in subsequent electric furnace phosphorus production.

[0041] In this invention, the dust collected during the general electric furnace phosphorus production process has a fine particle size and weak agglomeration, making it unsuitable for direct granulation and pelletizing, and difficult to recycle. Therefore, this invention uses a pneumatic dust collection mechanism to collect the dust and transport it to a dust silo to participate in the pelletizing raw material batching as a pelletizing auxiliary material. Since the dust has a certain degree of agglomeration properties, it can improve the agglomeration performance of phosphate rock powder to a certain extent. Moreover, the dust contains a high content of P2O5, and adding dust to phosphate rock powder can further improve the grade of green pellets without loss during roasting. Experiments have shown that the use of dust can increase the P2O5 content of cost phosphate rock pellets by at least 1%. Furthermore, this invention can also use aluminosilicates (such as potassium feldspar, sodium feldspar, calcium feldspar, montmorillonite, and zeolite) to modify the dust, increasing its agglomeration properties and improving the strength of the pellets after pelletizing, which can greatly reduce the amount of additional binder required.

[0042] In this invention, a bentonite bin is also provided, and bentonite is used as one of the pelletizing auxiliary materials. This can greatly make up for the poor adhesion of dust collector ash, thereby increasing the amount of dust collector ash added and improving the quality of the pellets. At the same time, it will not reduce the bonding strength of the pellets during pelletizing.

[0043] In this invention, a biomass straw bin (biomass straw includes, but is not limited to, rice straw, sorghum straw, corn straw, reed straw, wheat straw, etc.) is also provided. The biomass straw is used as one of the auxiliary materials for pelleting. The biomass straw is distributed in the green pellets, which can provide diffusion channels for the internal moisture of the green pellets, greatly increasing the rate of internal water vapor escape and avoiding the phenomenon of a large number of pellets bursting during high-temperature roasting. At the same time, the fibers of the biomass straw can improve the adhesion between phosphate rock powder particles and improve the strength of the biomass blocks. In addition, the biomass straw in the biomass blocks can provide some heat during subsequent roasting, which helps the high-temperature consolidation of the raw material blocks and further improves the physical strength and chemical properties.

[0044] Furthermore, to further improve the strength of the green pellets, the biomass straw underwent pretreatment before mixing. Specifically, the biomass straw particles were soaked in a calcium hydroxide solution (e.g., 0.01-1 mol / L) for 0.1-5 hours. After soaking, the biomass straw particles were filtered and dried before being added to the batch. Because the biomass straw adsorbs calcium hydroxide, it improves the bonding performance with other materials during the batching process, increasing the strength of the green pellets and significantly reducing the breakage rate during handling. Simultaneously, during subsequent heat treatment, the biomass straw decomposes upon heating, releasing carbon dioxide and water. The released carbon dioxide, under the action of water vapor, reacts with the internal calcium hydroxide to form a solidifying compound (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 rock pellets and reducing the ore fines rate. It should be noted that the amount of biomass straw added should not be too much or too little. Too much addition will reduce the proportion of phosphate rock powder and dust removal ash, thus reducing the yield. At the same time, too much straw particles will cause more large pores inside the finished phosphate rock pellets after heat treatment, which will easily lead to the collapse and pulverization of the finished phosphate rock pellets, which is not conducive to improving the strength of the finished phosphate rock pellets. On the other hand, if the amount added is too little, it will not be conducive to improving the internal bonding strength of the green pellets, and the green pellets will easily break up before heat treatment.

[0045] In this invention, all materials are automatically batched, and each batching tank is equipped with a level gauge to ensure stable discharge and precise batching. The entire batching process is automatically controlled by a computer according to manually set proportions. After batching, a high-powered mixer is used to mix and granulate the pelletizing mixture, which improves the granulation effect, resulting in better particle size distribution and stronger pellets. The high-powered mixer ensures that trace amounts of binder are fully mixed with the phosphate rock powder, improving the uniformity of the mixture, reducing binder usage, enhancing green pellet strength, reducing re-pellet production, and stabilizing green pellet quality. The purpose of pelletizing is to produce green pellets that meet the particle size requirements of the final pellet product and to ensure that the green pellets have sufficient mechanical strength to meet the requirements of the next process. Pelleting is a crucial step in the pelletizing process; the quality of the green pellets directly affects the normal operation of the pellet roasting process and the quality of the finished pellets.

[0046] In this invention, the process of turning green pellets into finished phosphate rock pellets requires transportation and high-temperature heat treatment. During the transportation and distribution process, collisions and compression between pellets are inevitable, and the roasting temperature reaches over 1100℃. This necessitates that the green pellets possess sufficient strength to prevent excessive breakage during transportation and bursting during heat treatment. Therefore, this invention incorporates biomass straw into the pellet mix, ensuring its even distribution throughout the green pellets. This provides 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 enhance the adhesion between phosphate rock powder particles, improving the pellet strength. Furthermore, the biomass straw provides additional heat during subsequent roasting, aiding in high-temperature consolidation and further enhancing the physical strength and chemical properties of the finished pellets.

[0047] In this invention, the strongly mixed material and the unqualified green pellets are discharged together by conveyors to various mixing bins, each lined with a 20mm thick wear-resistant ceramic liner. The pelletizing equipment uses a disc pelletizer with variable frequency speed control; the residence time of the material in the disc can be adjusted by changing the disc's inclination angle and rotation speed. The disc pelletizer uses a fixed scraper, allowing the mixed material to roll and grow into pellets under suitable moisture conditions. Due to centrifugal force, green pellets reaching a certain size automatically overflow the disc and fall onto the green pellet conveyor, then to the screening and distribution unit. Green pellet screening uses a roller screen with grading points of 8mm and 16mm. Particles <8mm and >16mm are returned to the pelletizing mixing bin via a return belt conveyor. Qualified green pellets of 8-16mm are conveyed to a shuttle distributor via a green pellet distribution mechanism and evenly distributed onto the drying bed at the top of the vertical furnace.

[0048] In this invention, the shuttle feeder of the vertical shaft furnace is simultaneously connected to the pelletizer and the natural phosphate ore bin. The natural phosphate ore bin is connected to the green pellet feeding and conveying mechanism via a large-angle belt conveyor for lump ore. When the vertical shaft furnace is started, natural phosphate ore can be fed into the furnace, or natural phosphate ore and green pellets can be fed into the furnace alternately. The vertical shaft furnace employs counter-current heat exchange. Green pellets are loaded into the furnace from the top via the shuttle feeder. Due to the uniform discharge of the discharge equipment, the green pellets move uniformly towards the bottom of the furnace. Hot flue gas from the combustion chamber enters the furnace through the burner nozzles, exchanging heat with the green pellets from bottom to top. The green pellets undergo drying and preheating from top to bottom, then enter the roasting and homogenization zone for high-temperature consolidation reaction. They are then cooled to below 600°C through the lower part of the vertical shaft furnace before being discharged. The most important aspect of the entire process is ensuring the airflow distribution of the furnace charge to achieve good permeability and uniform roasting. Green pellets that pass the roller screen grading are distributed onto the green pellet drying bed inside the furnace via a shuttle distributor. The thickness of the material layer is generally 150–200 mm, and the specific thickness can be adjusted according to the temperature of the exhaust gas under the drying grate and the furnace conditions. A ridge-shaped drying bed (the drying bed is triangular in shape) is used, with a top angle of 100°–110°. The hot flue gas rising from the preheating zone and the hot flue gas exiting from the guide wall mix under the drying bed, and the mixed gas exchanges heat with the descending green pellets to achieve the drying purpose. After 5–6 minutes of drying on the drying bed, the green pellets are basically dried and reach the furnace throat, entering the preheating zone. After preheating, the green pellets descend to the vertical furnace roasting section, where the roasting temperature is 1100–1300℃ (preferably 1150–1250℃). The vertical furnace is heated by high-temperature flue gas from the circular horizontal combustion chambers on both sides of the furnace. The combustion chamber temperature is regulated by controlling the gas flow rate and air flow rate of the burners to ensure a stable roasting temperature. Hot air from the cooling section is sent into the combustion chamber by a combustion blower as combustion air, allowing the combustible gas to burn fully at high temperatures, producing even hotter flue gas. The pellets move downwards from the roasting zone of the vertical shaft furnace into the soaking zone. Due to the presence of guide walls, most of the cooling air passes through these walls, with a small amount providing oxygen to ensure an oxidizing atmosphere in the soaking zone. Inside the soaking zone, the phosphate ore grains further grow, crystal transformation continues, the pellets further shrink and densify, the crystal structure is further improved, and the pellet strength is increased. Simultaneously, the unroasted pellets from the roasting section can be roasted in the soaking zone, which is essentially a continuation of the roasting section. Cooling air blown in from both sides of the lower part of the vertical shaft furnace exchanges heat with the high-temperature pellets through the cooling chamber, initially cooling them to a temperature of 300–600°C. After becoming hot flue gas, most of the cooling air rises along the low-resistance guide walls and merges with the flue gas from the roasting section, reaching the bottom of the green pellet drying bed as hot air for green pellet drying. The hydraulically driven toothed roller unloader, located at the bottom of the vertical shaft furnace, supports the entire feed column and serves a dual function of crushing (to prevent agglomeration) and discharging. The toothed roller is equipped with a matching hydraulic station. After passing through the toothed roller unloader, the pellets are continuously and evenly discharged from the furnace by an electric vibrating feeder and unloaded into the hot chain conveyor.When the combustion fan malfunctions, a portion of the air can be diverted to the combustion chamber via the cooling fan and ductwork. The low-temperature, dust-laden exhaust gas emitted from the top of the vertical shaft furnace has a temperature of 110℃~150℃. After being precipitated by the main electrostatic precipitator, it enters the desulfurization and denitrification unit via the main exhaust fan, and is then discharged through the chimney. The dust discharged from the electrostatic precipitator hopper is pumped through a pneumatic conveying pipeline to a dust silo for recycling.

[0049] In this invention, the cooling unit is a multi-stage belt cooler, which includes four stages of belt cooling (stage 1, stage 2, stage 3, and stage 4) and a hood covering them, arranged sequentially according to the material flow. Pellet ore is transported and unloaded onto the belt cooler via a chain conveyor for cooling. The cooled temperature is less than 120°C. Cooling blowers below stage 4 blow air into stage 4 for cooling, and cooling blowers below stage 3 blow air into stage 3 for cooling. Air from stage 4 is drawn into stage 2 for cooling, and air from stage 2 is drawn into stage 1 for cooling. Air from stage 2 is sent to the vertical shaft furnace combustion chamber for combustion support, and air from stage 1 is sent to the drying cylinder for drying the ore powder. The hot air generated during cooling is recycled to heat the raw material drying and the vertical shaft furnace combustion chamber. Waste heat is fully recovered through cascade utilization. The exhausted gas is discharged after dust removal, desulfurization, and denitrification, significantly reducing heating energy consumption and increasing environmental benefits.

[0050] In this invention, cooled pellets are conveyed to the finished product screening system via a belt conveyor. Bulk material from the cooler and dust collected from the bellows are collected by a scraper conveyor and sent to the finished product screening system along with the cooled pellets. The cooled pellets are screened using a cantilever bar screen to remove particles smaller than 5mm. Undersized pellets are stored in a powder silo, with a discharge valve at the bottom for truck transport to a temporary phosphate rock powder storage area. Qualified finished products are conveyed to the finished product silo via a belt conveyor. The finished product silo is equipped with an electro-hydraulic sector valve for unloading. One finished product silo has a truck transport route to the electric furnace, while the remaining finished product silos are conveyed to the electric furnace via belt conveyors.

[0051] In this invention, various powders and dust generated during the process are recycled and reused, which can realize the recycling of valuable resources and avoid direct discharge and environmental pollution.

[0052] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0053] 1. This invention couples high-calcium phosphate rock powder and high-silicon phosphate rock powder, which cannot be reused in existing phosphate rock processing, to solve the problem of resource waste caused by the large amount of stockpiled phosphate rock powder in existing phosphate rock processing, as well as the problem of land resource waste caused by large-scale stockpiling. It realizes the efficient reuse of phosphate rock powder as a resource and also greatly saves land resources.

[0054] 2: This invention greatly improves the lumping performance of dust collector ash by compounding it with bentonite or by modifying the dust collector ash. At the same time, it further improves the strength of the raw material blocks by bridging it with biomass straw, effectively ensuring the quality of the finished block mineral products. It can also accommodate more dust collector ash and improve the utilization efficiency of the dust collector ash.

[0055] 3: This invention adds biomass straw during the mixing and pelleting process. Through the bridging effect of biomass straw, the strength of the green pellets is further improved, while the bursting loss of the pellets during heat treatment is greatly reduced. This effectively ensures the quality and yield of the finished pellets. It also helps to accommodate more bulk and powder materials, improves resource recycling efficiency, and reduces environmental pollution.

[0056] 4. The finished pellets obtained by this invention have a concentrated and stable particle size distribution, good permeability, and low pulverization rate under the high-temperature reducing atmosphere of subsequent yellow phosphorus production, which can greatly reduce the amount of dust in phosphorus production. Furthermore, 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 lump ore phosphorus production, improve phosphorus purity, and thus enhance economic benefits. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the overall structure of the system described in this invention.

[0058] Figure reference numerals: 1: High-calcium phosphate rock powder silo; 2: High-silica phosphate rock powder silo; 3: Drying device; 301: Cylindrical dryer; 302: Wet dust collector; 303: Drying fan; 304: Drying exhaust stack; 305: Hot air furnace; 306: Sedimentation tank; 307: Sludge drying device; 308: Dry sludge conveying mechanism; 4: Grinding device; 401: Roller screen; 402: Grinding buffer silo; 403: High 404: Reversible quantitative feeder; 405: Iron separator; 5: Temporary mineral powder stockpile; 501: Grab crane; 6: Dust silo; 7: Bentonite silo; 8: Biomass straw silo; 9: High-intensity mixer; 10: Mixing silo; 11: Disc pelletizer; 12: Roller screen; 1201: Returning pellet belt conveyor; 13: Natural phosphate lump ore silo; 1301: Large-angle belt conveyor for lump ore. 14: Shuttle feeder; 15: Vertical shaft furnace; 16: Vibratory feeder; 17: Hot chain conveyor; 18: Toothed roll crusher; 19: First cooling section; 20: Second cooling section; 21: Third cooling section; 22: Fourth cooling section; 23: Air hood; 24: First circulating air duct; 25: Second circulating air duct; 26: Third circulating air duct; 27: Fourth circulating air duct; 28: Finished product screen; 29: Finished product silo; 30: Powder silo; 31: Main flue gas dust collector; 32: Main exhaust fan; 33: Desulfurization and denitrification device; 34: Chimney; 35: Pneumatic conveying silo pump; 36: Pneumatic dust conveying pipeline; A: Mineral powder feeding conveyor; B: Mineral powder discharging conveyor; C: Drying discharging conveyor; D: Grinding discharging conveyor; E: Green pellet conveyor; F: Green pellet feeding conveyor; G: Screen material conveyor. Detailed Implementation

[0059] 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.

[0060] A phosphate rock roasting production system includes a phosphate rock pretreatment unit, an auxiliary material distribution unit, a pelletizing unit, a screening and distribution unit, a roasting unit, a cooling unit, and a finished product processing unit. The phosphate rock pretreatment unit and the auxiliary material distribution unit are arranged in parallel, and according to the material flow, both the phosphate rock pretreatment unit and the auxiliary material distribution unit are connected in series with the pelletizing unit, the screening and distribution unit, the roasting unit, the cooling unit, and the finished product processing unit.

[0061] Preferably, the phosphate rock pretreatment unit includes a high-calcium phosphate rock powder silo 1, a high-silica phosphate rock powder silo 2, a drying device 3, and a grinding device 4. A phosphate rock powder feeding and conveying mechanism A is connected to the feed ends of both the high-calcium phosphate rock powder silo 1 and the high-silica phosphate rock powder silo 2, respectively, to transport phosphate rock powder from the outside to either the high-calcium phosphate rock powder silo 1 or the high-silica phosphate rock powder silo 2 for pre-storage. The discharge ends of the high-calcium phosphate rock powder silo 1 and the high-silica phosphate rock powder silo 2 are connected to the feed ends of the drying device 3, the grinding device 4, and the pelletizing unit, respectively, via a phosphate rock powder discharge conveying mechanism B. The discharge end of the drying device 3 is connected to the feed end of the grinding device 4 via a drying discharge conveying mechanism C. The discharge end of the grinding device 4 is connected to the feed end of the pelletizing unit via a grinding discharge conveying mechanism D. Preferably, a discharge vibrating bucket, a disc feeder, and a quantitative feeder are separately and sequentially installed between the discharge end of the high-calcium phosphate rock powder silo 1 and the feed end of the phosphate rock powder discharge conveying mechanism.

[0062] Preferably, the mineral powder feeding conveyor A, the mineral powder discharging conveyor B, the drying discharging conveyor C, and the grinding discharging conveyor D each independently include one or more belt conveyors, and each belt conveyor may or may not be equipped with a pear-shaped unloader.

[0063] Preferably, the phosphate rock pretreatment unit further includes a temporary phosphate rock storage yard 5, which is connected to the discharge end of the phosphate rock feeding and conveying mechanism A. A grab crane 501 is also installed on the temporary phosphate rock storage yard 5. The grab crane 501 transports the stored phosphate rock to the high-calcium phosphate rock silo 1 and / or the high-silica phosphate rock silo 2.

[0064] Preferably, the drying device 3 includes a cylindrical dryer 301, a wet scrubber 302, a drying fan 303, and a drying exhaust stack 304. According to the airflow direction, the cylindrical dryer 301, wet scrubber 302, drying fan 303, and drying exhaust stack 304 are connected in series. The material discharge end of the cylindrical dryer 301 is connected to the feed end of the drying discharge conveying mechanism C. Preferably, the drying device 3 also includes a hot air furnace 305, a sedimentation tank 306, and a sludge drying device 307. The hot air outlet of the hot air furnace 305 is connected via a hot air pipe to an air inlet located on the side of the material discharge end of the cylindrical dryer 301. The dust outlet of the wet dust collector 302 is connected to the inlet of the sedimentation tank 306, the sludge outlet of the sedimentation tank 306 is connected to the inlet of the sludge drying device 307, and the discharge outlet of the sludge drying device 307 is connected to the temporary mineral powder stockpile 5 through the dry sludge conveying mechanism 308.

[0065] Preferably, the grinding device 4 includes a roller screen 401, a grinding buffer chamber 402, and a high-pressure roller mill 403 arranged in series. The feed end of the roller screen 401 is connected to the discharge ends of the ore powder discharge conveying mechanism B and the drying discharge conveying mechanism C. The discharge end of the high-pressure roller mill 403 is connected to the feed end of the grinding discharge conveying mechanism D. Preferably, the discharge end of the grinding buffer chamber 402 is connected to the feed end of the high-pressure roller mill 403 and the feed end of the grinding discharge conveying mechanism D respectively through a reversible quantitative feeder 404. More preferably, a vibration anti-clogging device is also provided on the side wall of the discharge end of the grinding buffer chamber 402. An iron remover 405 is also provided on the roller screen 401.

[0066] Preferably, the auxiliary material delivery unit includes a dust bin 6, a bentonite bin 7, and a biomass straw bin 8 arranged in parallel. The discharge ends of the dust bin 6 and the bentonite bin 7 are independently and sequentially connected in series with a vibration anti-blocking device, a star-shaped ash discharge valve, a screw feeder, and a sealed belt scale. The discharge ends of all sealed belt scales are connected to the mineral powder discharge conveying mechanism B. The discharge end of the biomass straw bin 8 is sequentially connected in series with a discharge vibrating hopper, a disc feeder, and a quantitative feeder. The discharge end of the quantitative feeder is connected to the mineral powder discharge conveying mechanism B.

[0067] Preferably, the pelletizing unit includes a high-intensity mixer 9, a mixing silo 10, and a disc pelletizer 11 arranged in series. The feed end of the high-intensity mixer 9 is connected to the discharge end of the mineral powder discharge conveying mechanism B. The discharge end of the disc pelletizer 11 is connected to the screening and distribution unit via a green pellet conveying mechanism E. A discharge vibrating hopper, a disc feeder, and a quantitative feeder are also arranged in series between the mixing silo 10 and the disc pelletizer 11. Preferably, the green pellet conveying mechanism E includes one or more belt conveyors.

[0068] Preferably, the pelletizing unit includes multiple sets of mixing bins 10 arranged in parallel and a disc pelletizer 11.

[0069] Preferably, the screening and distribution unit includes a roller screen 12 and a natural phosphate ore bin 13. The feed end of the roller screen 12 is connected to the discharge end of the green ball conveying mechanism E. The large ball discharge end and the small ball discharge end of the roller screen 12 are both connected to the feed end of the mixing bin 10 via a return ball belt conveyor 1201. The medium ball discharge end of the roller screen 12 is connected to the feed end of the vertical shaft furnace roasting unit via a green ball feeding conveyor F. The natural phosphate ore bin 13 is arranged parallel to the roller screen 12, and the discharge end of the natural phosphate ore bin 13 is connected to the green ball feeding conveyor F via a large-angle lump ore belt conveyor 1301. Preferably, the green ball feeding conveyor F includes one or more belt conveyors.

[0070] Preferably, the vertical shaft furnace roasting unit includes a shuttle feeder 14, a vertical shaft furnace 15, an electric vibratory feeder 16, and a hot chain conveyor 17 arranged in series. The feed end of the shuttle feeder 14 is connected to the discharge end of the green ball feeding and conveying mechanism F. The discharge end of the hot chain conveyor 17 is connected to the feed end of the cooling unit. Preferably, a toothed roller crusher 18 is also provided between the discharge end of the vertical shaft furnace 15 and the electric vibratory feeder 16. Preferably, a combustion fan and a cooling fan are also provided on one side of the vertical shaft furnace 15. The combustion fan is connected to the combustion chamber at the top of the vertical shaft furnace 15 through a combustion fan duct, and the cooling fan is connected to the cooling chamber at the bottom of the vertical shaft furnace 15 through a cooling fan duct.

[0071] Preferably, the cooling unit is a multi-stage belt cooler, which includes, in sequence according to the material flow direction, a first cooling stage 19, a second cooling stage 20, a third cooling stage 21, a fourth cooling stage 22, and an air hood 23 covering them. The feed end of the first cooling stage 19 is connected to the discharge end of the hot chain conveyor 17, and the discharge end of the fourth cooling stage 22 is connected to the feed end of the finished product processing unit.

[0072] Preferably, the lower air inlets of the cooling third section 21 and the cooling fourth section 22 are each connected to a blower via independent ducts. The upper air outlet of the cooling fourth section 22 is connected to the upper air inlet of the cooling second section 20 via a first circulating duct 24, and the lower air outlet of the cooling second section 20 is connected to the combustion air blower of the vertical furnace 15 via a second circulating duct 25. The upper air outlet of the cooling third section 21 is connected to the upper air inlet of the cooling first section 19 via a third circulating duct 26, and the lower air outlet of the cooling first section 19 is connected to the air inlet of the cylindrical dryer 301 via a fourth circulating duct 27. Preferably, an exhaust fan is also installed on the fourth circulating duct 27.

[0073] Preferably, the finished product processing unit includes a finished product sieve 28, a finished product bin 29, and a powder bin 30. The feed end of the finished product sieve 28 is connected to the discharge end of the cooling section 22. The discharge end of the finished product sieve 28 is connected to the feed end of the finished product bin 29, and the discharge end of the finished product sieve 28 is connected to the feed end of the powder bin 30. Both the discharge ends of the finished product bin 29 and the powder bin 30 are equipped with electro-hydraulic sector valves.

[0074] Preferably, the finished product processing unit includes multiple finished product bins 29, and the discharge end of the finished product screen 28 is connected to the feed ends of the multiple finished product bins 29 via an over-screen material conveying mechanism G. The over-screen material conveying mechanism G includes one or more belt conveyors and / or heavy-duty unloading vehicles.

[0075] Preferably, the vertical shaft furnace roasting unit further includes a main flue gas dust collector 31, the inlet of which is connected to the top flue gas outlet of the vertical shaft furnace 15 via a flue gas conveying pipe. The exhaust outlet of the main flue gas dust collector 31 is connected to the chimney 34 via an exhaust pipe, on which a main exhaust fan 32 and a desulfurization and denitrification device 33 are sequentially installed. The bottom dust outlet of the main flue gas dust collector 31 is connected to the feed end of the dust silo 6 via a pneumatic conveying pump 35 and a pneumatic dust conveying pipe 36.

[0076] Example 1

[0077] like Figure 1 As shown, a phosphate rock roasting production system includes a phosphate rock pretreatment unit, an auxiliary material distribution unit, a pelletizing unit, a screening and distribution unit, a roasting unit, a cooling unit, and a finished product processing unit. The phosphate rock pretreatment unit and the auxiliary material distribution unit are arranged in parallel, and according to the material flow, both the phosphate rock pretreatment unit and the auxiliary material distribution unit are connected in series with the pelletizing unit, the screening and distribution unit, the roasting unit, the cooling unit, and the finished product processing unit.

[0078] The phosphate rock pretreatment unit includes a high-calcium phosphate rock powder silo 1, a high-silica phosphate rock powder silo 2, a drying device 3, and a grinding device 4. A phosphate rock powder feeding and conveying mechanism A is connected to the feed ends of both the high-calcium phosphate rock powder silo 1 and the high-silica phosphate rock powder silo 2, respectively, to transport phosphate rock powder from external sources to either silo 1 or silo 2 for pre-storage. The discharge ends of the high-calcium phosphate rock powder silo 1 and the high-silica phosphate rock powder silo 2 are connected to the feed ends of the drying device 3, the grinding device 4, and the pelletizing unit via a phosphate rock powder discharge conveying mechanism B, respectively. The discharge end of the drying device 3 is connected to the feed end of the grinding device 4 via a drying discharge conveying mechanism C. The discharge end of the grinding device 4 is connected to the feed end of the pelletizing unit via a grinding discharge conveying mechanism D. Preferably, a discharge vibrating bucket, a disc feeder, and a quantitative feeder are separately and sequentially installed between the discharge end of the high-calcium phosphate rock powder silo 1 and the feed end of the phosphate rock powder discharge conveying mechanism.

[0079] Example 2

[0080] The embodiment 1 is repeated, except that the mineral powder feeding conveyor A, mineral powder discharging conveyor B, drying discharging conveyor C, and grinding discharging conveyor D each independently include one or more belt conveyors, and each belt conveyor may or may not be equipped with a pear-shaped unloader.

[0081] Example 3

[0082] The embodiment 2 is repeated, except that the phosphate rock pretreatment unit also includes a temporary phosphate powder stockpile 5, which is connected to the discharge end of the phosphate powder feeding and conveying mechanism A. A grab crane 501 is also installed on the temporary phosphate powder stockpile 5. The grab crane 501 transports the stockpiled phosphate powder to the high-calcium phosphate powder silo 1 and the high-silica phosphate powder silo 2.

[0083] Example 4

[0084] The drying device 3 is repeated in embodiment 3, except that it includes a cylindrical dryer 301, a wet scrubber 302, a drying fan 303, and a drying exhaust stack 304. According to the airflow direction, the cylindrical dryer 301, wet scrubber 302, drying fan 303, and drying exhaust stack 304 are connected in series. The material discharge end of the cylindrical dryer 301 is connected to the feed end of the drying discharge conveying mechanism C. The drying device 3 also includes a hot air furnace 305, a sedimentation tank 306, and a sludge drying device 307. The hot air outlet of the hot air furnace 305 is connected to an air inlet located on the side of the material discharge end of the cylindrical dryer 301 via a hot air pipe. The dust outlet of the wet dust collector 302 is connected to the inlet of the sedimentation tank 306, the sludge outlet of the sedimentation tank 306 is connected to the inlet of the sludge drying device 307, and the discharge outlet of the sludge drying device 307 is connected to the temporary mineral powder stockpile 5 through the dry sludge conveying mechanism 308.

[0085] Example 5

[0086] The embodiment 4 is repeated, except that the grinding device 4 includes a roller screen 401, a grinding buffer chamber 402, and a high-pressure roller mill 403 arranged in series. The feed end of the roller screen 401 is connected to the discharge ends of the ore powder discharge conveying mechanism B and the drying discharge conveying mechanism C. The discharge end of the high-pressure roller mill 403 is connected to the feed end of the grinding discharge conveying mechanism D.

[0087] Example 6

[0088] Example 5 is repeated, except that the discharge end of the grinding buffer chamber 402 is connected to the feed end of the high-pressure roller mill 403 and the feed end of the grinding discharge conveying mechanism D through the reversible quantitative feeder 404.

[0089] Example 7

[0090] Example 6 is repeated, except that a vibration anti-blocking device is also provided on the discharge end side wall of the grinding buffer chamber 402. An iron remover 405 is also provided on the roller screen 401.

[0091] Example 8

[0092] The embodiment 7 is repeated, except that the auxiliary material delivery unit includes a dust bin 6, a bentonite bin 7, and a biomass straw bin 8 arranged in parallel. The discharge ends of the dust bin 6 and the bentonite bin 7 are independently and sequentially connected in series with a vibration anti-blocking device, a star-shaped ash discharge valve, a screw feeder, and a sealed belt scale. The discharge ends of all sealed belt scales are connected to the mineral powder discharge conveying mechanism B. The discharge end of the biomass straw bin 8 is sequentially connected in series with a discharge vibrating hopper, a disc feeder, and a quantitative feeder. The discharge end of the quantitative feeder is connected to the mineral powder discharge conveying mechanism B.

[0093] Example 9

[0094] The embodiment 8 is repeated, except that the pelletizing unit includes a high-intensity mixer 9, a mixing silo 10, and a disc pelletizer 11 arranged in series. The feed end of the high-intensity mixer 9 is connected to the discharge end of the mineral powder discharge conveying mechanism B. The discharge end of the disc pelletizer 11 is connected to the screening and distribution unit via a green pellet conveying mechanism E. Between the mixing silo 10 and the disc pelletizer 11, a discharge vibrating hopper, a disc feeder, and a quantitative feeder are also arranged in series. The green pellet conveying mechanism E includes one or more belt conveyors.

[0095] Example 10

[0096] Example 9 is repeated, except that the pelletizing unit includes multiple sets of parallel-arranged mixing bins 10 and a disc pelletizer 11.

[0097] Example 11

[0098] The embodiment 10 is repeated, except that the screening and distribution unit includes a roller screen 12 and a natural phosphate ore bin 13. The feed end of the roller screen 12 is connected to the discharge end of the green ball conveying mechanism E. Both the large ball discharge end and the small ball discharge end of the roller screen 12 are connected to the feed end of the mixing bin 10 via a return ball belt conveyor 1201. The medium ball discharge end of the roller screen 12 is connected to the feed end of the vertical shaft furnace roasting unit via a green ball feeding conveyor F. The natural phosphate ore bin 13 is arranged parallel to the roller screen 12. The discharge end of the natural phosphate ore bin 13 is connected to the green ball feeding conveyor F via a large-angle lump ore belt conveyor 1301. The green ball feeding conveyor F includes one or more belt conveyors.

[0099] Example 12

[0100] The embodiment 11 is repeated, except that the vertical furnace roasting unit includes a shuttle feeder 14, a vertical furnace 15, an electric vibratory feeder 16, and a hot chain conveyor 17 arranged in series. The feed end of the shuttle feeder 14 is connected to the discharge end of the green ball feeding and conveying mechanism F. The discharge end of the hot chain conveyor 17 is connected to the feed end of the cooling unit.

[0101] Example 13

[0102] Example 12 is repeated, except that a toothed roll crusher 18 is also provided between the discharge end of the vertical furnace 15 and the electric vibratory feeder 16.

[0103] Example 14

[0104] The embodiment 13 is repeated, except that a combustion fan and a cooling fan are also provided on one side of the vertical furnace 15. The combustion fan is connected to the combustion chamber at the top of the vertical furnace 15 through a combustion air duct, and the cooling fan is connected to the cooling chamber at the bottom of the vertical furnace 15 through a cooling air duct.

[0105] Example 15

[0106] The embodiment 14 is repeated, except that the cooling unit is a multi-stage belt cooler, which includes, in sequence according to the material flow, a first-stage cooling section 19, a second-stage cooling section 20, a third-stage cooling section 21, a fourth-stage cooling section 22, and an air hood 23 covering them. The feed end of the first-stage cooling section 19 is connected to the discharge end of the hot chain conveyor 17, and the discharge end of the fourth-stage cooling section 22 is connected to the feed end of the finished product processing unit.

[0107] Example 16

[0108] The embodiment 15 is repeated, except that the lower air inlets of the cooling section 21 and the cooling section 22 are each connected to a blower via independent ducts. The upper air outlet of the cooling section 22 is connected to the upper air inlet of the cooling section 20 via the first circulating duct 24, and the lower air outlet of the cooling section 20 is connected to the combustion air blower of the vertical furnace 15 via the second circulating duct 25. The upper air outlet of the cooling section 21 is connected to the upper air inlet of the cooling section 19 via the third circulating duct 26, and the lower air outlet of the cooling section 19 is connected to the air inlet of the cylindrical dryer 301 via the fourth circulating duct 27. An exhaust fan is also installed on the fourth circulating duct 27.

[0109] Example 17

[0110] The process is repeated in Example 16, except that the finished product processing unit includes a finished product sieve 28, a finished product bin 29, and a powder bin 30. The feed end of the finished product sieve 28 is connected to the discharge end of the cooling section 22. The discharge end of the finished product sieve 28 (over-sieve) is connected to the feed end of the finished product bin 29, and the discharge end of the finished product sieve 28 (under-sieve) is connected to the feed end of the powder bin 30. Both the finished product bin 29 and the powder bin 30 are equipped with electro-hydraulic sector valves at their discharge ends.

[0111] Example 18

[0112] The embodiment 17 is repeated, except that the finished product processing unit includes multiple finished product bins 29, and the discharge end of the finished product screen 28 is connected to the feed ends of the multiple finished product bins 29 through an over-screen material conveying mechanism G. The over-screen material conveying mechanism G includes one or more belt conveyors and a heavy-duty unloading vehicle.

[0113] Example 19

[0114] The embodiment 18 is repeated, except that the vertical shaft furnace roasting unit further includes a main flue gas dust collector 31. The inlet of the main flue gas dust collector 31 is connected to the top flue gas outlet of the vertical shaft furnace 15 via a flue gas conveying pipe. The exhaust outlet of the main flue gas dust collector 31 is connected to the chimney 34 via an exhaust pipe, on which a main exhaust fan 32 and a desulfurization and denitrification device 33 are sequentially installed. The bottom dust outlet of the main flue gas dust collector 31 is connected to the feed end of the dust silo 6 via a pneumatic conveying pump 35 and a pneumatic dust conveying pipe 36.

[0115] Example 20

[0116] A method for producing phosphate rock by vertical shaft roasting using the system described in Example 19, the method comprising:

[0117] 1) After pre-treating the phosphate rock powder through the phosphate rock pre-treatment unit, high-calcium phosphate rock powder and high-silica phosphate rock powder are obtained; then the high-calcium phosphate rock powder and high-silica phosphate rock powder are mixed to obtain mixed mineral powder;

[0118] 2) Mix the mineral powder, dust (collected dust from the system), bentonite, and biomass straw pellets in proportion to obtain pelletizing mixture;

[0119] 3) Add the pelletizing mixture to the pelletizing machine for pelletizing, and screen the obtained green pellets to obtain large pellets, seed pellets and small pellets; the large and small pellets are crushed and returned to step 2) for mixing; the medium pellets enter the next process;

[0120] 4) The pellets obtained in step 3) are fed into a vertical furnace for roasting. The roasted pellets are then cooled by a belt cooler and screened by a screening machine before being transported to the finished product warehouse for storage.

[0121] Example 21

[0122] Example 20 is repeated, except that the high-calcium phosphate rock powder is phosphate rock powder with a P2O5 content of no more than 15 wt%, a CaO content of no less than 40 wt%, and a water content of 6-10%; and the high-silicon phosphate rock powder is phosphate rock powder with a P2O5 content of no more than 15 wt%, a SiO2 content of no less than 40 wt%, and a water content of 6-10%.

[0123] Example 22

[0124] Repeat Example 21, except that the particle size of the medium sphere is 5-20 mm; spheres with a particle size larger than the medium sphere are called large spheres, and spheres with a particle size smaller than the medium sphere are called small spheres.

[0125] Example 23

[0126] Repeat Example 22, except that 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.

[0127] Application Example 1

[0128] Phosphate ore roasting in a vertical shaft furnace was carried out using the system described in Example 19 and the method described in Example 23.

[0129] High-calcium phosphate rock powder (P2O5 content approximately 13.6%, CaO content approximately 47.2%) and high-silica phosphate rock powder (P2O5 content approximately 14.4%, SiO2 content approximately 45.8%) were pretreated (dried and roller-milled) respectively, and then mixed to obtain a mixed mineral powder with a particle size not greater than 0.125 mm and a moisture content of approximately 8.2% (the mixing mass ratio of high-calcium phosphate rock powder to high-silica phosphate rock powder was 1.3:1).

[0130] Mixed mineral powder, dust, bentonite, and corn stalk particles are vigorously mixed at a mass ratio of 97:6:3:1 to obtain a pelletizing mixture. This mixture is then pelletized in a disc pelletizer. The resulting green pellets are screened, and green pellets with a particle size of 8-16 mm are fed into a vertical shaft furnace with natural lump ore (P2O5 content 22.20%) using a shuttle feeder and calcined at 1200℃ for 5 hours. After cooling and toothed roller crushing, the sintered pellets are conveyed via a hot chain conveyor to a multi-stage belt cooler for further cooling. The cooled pellets are then screened to collect finished pellets with a particle size of not less than 5 mm.

[0131] Application Example 2

[0132] The application of Example 1 was repeated, except that the dust collector ash was mixed and ground with potassium feldspar to obtain modified dust collector ash (the amount of potassium feldspar added was 2.5% of the total mass of the dust collector ash).

[0133] Application Example 3

[0134] The modified straw pellets were obtained by repeating Example 1, except that the corn straw pellets were soaked in a 0.02 mol / L calcium hydroxide solution for 1 hour and then filtered dry.

[0135]

[0136]

Claims

1. A method for producing phosphate rock by vertical shaft furnace roasting, characterized in that: The method includes: 1) After pretreating the phosphate rock powder through a phosphate rock pretreatment unit, high-calcium phosphate rock powder and high-silica phosphate rock powder are obtained; then, the high-calcium phosphate rock powder and high-silica phosphate rock powder are mixed to obtain mixed mineral powder; the high-calcium phosphate rock powder is phosphate rock powder with a P2O5 content of not more than 15wt%, a CaO content of not less than 40wt%, and a moisture content of 6-10%; the high-silica phosphate rock powder is phosphate rock powder with a P2O5 content of not more than 15wt%, a SiO2 content of not less than 40wt%, and a moisture content of 6-10%. 2) Mix the mineral powder, dust collector ash, bentonite, and biomass straw pellets in the specified proportions to obtain a pelletizing mixture; 3) The pelletizing mixture is added to the pelletizer for pelletizing, and the obtained green pellets are screened to obtain large, medium and small pellets; the large and small pellets are crushed and returned to step 2) for mixing; the medium pellets enter the next process; the particle size of the medium pellets is 5-20mm; pellets with a particle size larger than the medium pellets are large pellets, and pellets with a particle size smaller than the medium pellets are small pellets; 4) The pellets obtained in step 3) are fed into a vertical furnace for roasting. The roasted pellets are then cooled by a belt cooler and screened by a screening machine before being transported to the finished product warehouse for storage.

2. The method according to claim 1, characterized in that: In step 1), the mixing mass ratio of high-calcium phosphate rock powder to high-silica phosphate rock powder is 1.2-1.6:1; the average particle size of the mixed mineral powder is not greater than 0.15 mm.

3. The method according to claim 1, characterized in that: In step 1), the high-calcium phosphate rock powder is phosphate rock powder with a P2O5 content of 10-15wt%, a CaO content of 45-55wt%, and a water content of 8-9%.

4. The method according to claim 1, characterized in that: In step 1), the high-silica phosphate rock powder is phosphate rock powder with a P2O5 content of 10-15wt%, a SiO2 content of 45-55wt%, and a water content of 8-9%.

5. The method according to claim 2, characterized in that: In step 1), the mixing mass ratio of high-calcium phosphate rock powder to high-silica phosphate rock powder is 1.3-1.45:

1.

6. The method according to claim 5, characterized in that: In step 1), the average particle size of the mixed mineral powder is no greater than 0.125 mm.

7. The method according to any one of claims 1-6, characterized in that: In step 2), the mixing mass ratio of mineral powder, dust, bentonite, and biomass straw pellets is 92-98:3-8:1-5:0.5-2.

8. The method according to any one of claims 1-6, characterized in that: The biomass straw pellets are modified biomass straw pellets treated with calcium hydroxide solution.

9. The method according to any one of claims 1-6, characterized in that: In step 4), the roasting temperature is 1100-1300℃ and the roasting time is 1-10h; the pellet size of the pellets transported to the finished product silo after screening is not less than 5mm.

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

Images