A kind of mixed phosphate rock co-disposal pellet roasting system and method

Abstract

The application discloses a kind of mixed phosphorite collaborative disposal pellet roasting system and method, the system includes the mixed phosphorite pretreatment unit, proportioning unit, pelletizing unit, cloth unit and roasting cooling unit in turn series connection setting.This application existing phosphorite processing phosphorite powder cannot be reused, causing resource waste problem, simultaneously realizes the collaborative disposal of different types of low-grade phosphorite powder, solves the problem that existing phosphorite processing phosphorite powder source is narrow and a large amount of stockpiling causes land resource waste, realizes the resource utilization of phosphorite powder, also greatly saves land resources.The block ore product quality prepared simultaneously is good, intensity is high, subsequent transport is facilitated, and the transportability is strong;It also has the characteristics that structure layout is simple, system component organization is orderly and reasonable, and the amount of layout site demand is small, which greatly saves land resources, can meet various topographic requirements, and has wide application range.

Description

Technical Field

[0001] This invention relates to various technologies for the resource utilization of low-grade phosphate rock powder, specifically to a pellet roasting system and method for the co-processing of mixed phosphate rock, belonging to the field of low-grade phosphate rock powder reuse 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] 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.

[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 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

[0005] In response to the problems of low utilization rate of low-grade phosphate rock powder, 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 pellet roasting system and method for co-processing mixed phosphate rock. This system can coordinate and batch various low-grade phosphate rock powders with different properties, and after raw material pretreatment, it can be used to prepare finished phosphate rock pellets required for yellow phosphorus production. This can not only effectively utilize powdered phosphate resources, expand the source of raw materials, alleviate the problem of raw material shortage for yellow phosphorus enterprises, but also effectively reduce raw material costs and greatly save land resources.

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

[0007] According to a first embodiment of the present invention, an improved pellet roasting system for co-processing mixed phosphate rock is provided:

[0008] A pellet roasting system for co-processing mixed phosphate rock includes a mixed phosphate rock pretreatment unit, a batching unit, a pelletizing unit, a feeding unit, and a roasting and cooling unit. These units are connected in series according to the material flow direction. The mixed phosphate rock pretreatment unit includes a high-calcium phosphate rock powder buffer silo, a high-silica phosphate rock powder buffer silo, and a bulk material buffer silo arranged in parallel. The discharge ends of the high-calcium phosphate rock powder buffer silo, the high-silica phosphate rock powder buffer silo, and the bulk material buffer silo are all connected to the feed end of a vertical mill via a first large-angle belt conveyor. A flue gas furnace is located on one side of the vertical mill, and its exhaust port is connected to the air inlet of the vertical mill via a flue gas pipe. The discharge port of the vertical mill is connected to the feed inlet of a pulse belt dust collector via a discharge duct. The bottom discharge end of the pulse belt dust collector is connected to the feed end of the batching unit. Preferably, the first inclined belt conveyor is also equipped with an iron remover.

[0009] In this invention, a combination of a vertical mill with hot air separation and a pulse belt dust collector is used. A front-loading receiving bin is installed before the vertical mill to receive fine ore and bulk materials, and a direct-drive quantitative feeder is installed below the bin to control and adjust the feed rate. After grinding, the material undergoes air classification, baghouse dust collection, and screw conveying before entering the fine ore bin. The exhaust gas after dust collection is sent to a desulfurization and denitrification device for further treatment, and is discharged into the atmosphere after meeting emission standards. To protect the mill, a permanent magnet separator is installed on the first inclined belt conveyor to remove any iron particles that may be present in the raw material.

[0010] In this invention, vibration anti-blocking devices are installed at the bottom of the high-calcium phosphate rock powder buffer silo, the high-silica phosphate rock powder buffer silo, and the bulk material buffer silo near the outlet. In addition, a feeding gate is installed at the outlet of each silo, and a quantitative feeder (direct-drive type) is installed below the feeding gate. The feeding gate and the quantitative feeder are controlled by computer to discharge different raw materials.

[0011] Preferably, an explosion-proof duct is also extended from the discharge duct, and an explosion-proof valve is installed on the explosion-proof duct.

[0012] Preferably, the exhaust port of the pulse belt dust collector is connected to the desulfurization and denitrification device through a pulverized coal fan and an external exhaust pipe.

[0013] In this invention, a manual slide gate valve is installed at the outlet of the dust hopper below the pulse bag filter, a rotary valve is installed below the manual slide gate valve, and a screw conveyor (which can rotate in both directions) is installed below the rotary valve.

[0014] Preferably, the batching unit includes a mixed powder silo, a biomass straw silo, and a dust silo. The feed end of the mixed powder silo is connected to the bottom discharge end of a pulse belt dust collector via a screw feeder. The discharge ends of the mixed powder silo, biomass straw silo, and dust silo are all connected to the feed end of the pelletizing unit via a batching belt conveyor. Preferably, the feed end of the dust silo is also equipped with a dust receiving device.

[0015] In this invention, multiple mixing powder silos, biomass straw silos, and dust silos can be provided. Typically, two mixing powder silos, one biomass straw silo, and one dust silo are designed. The two ends of a screw conveyor are connected to the inlet of one mixing powder silo, and the forward and reverse rotation of the screw conveyor transports the powder ore from the pulse bag filter to the two mixing powder silos respectively. Furthermore, vibration anti-blocking devices and automatic or manual gate valves are also installed at the outlets of the mixing powder silos, biomass straw silos, and dust silos. The biomass straw silo is connected to a batching belt conveyor via a direct-drive quantitative feeder, while the mixing powder silos and dust silos are both connected to the batching belt conveyor via fully sealed quantitative feeders. In addition, an impeller feeder can be installed between the manual gate valve of the dust silo and its fully sealed quantitative feeder.

[0016] Preferably, the pelletizing unit includes a high-intensity mixer, a mixing silo, and a pelletizer. The feed end of the high-intensity mixer is connected to the discharge end of the batching belt conveyor, and the discharge end of the high-intensity mixer is simultaneously connected to the feed ends of multiple mixing silos via the mixing belt conveyor and several plow-type unloaders. A pelletizer is installed below the discharge port of each mixing silo. The discharge ends of all pelletizers are connected to the feed end of the fabric distribution unit via a green pellet belt conveyor. Preferably, a weighing scale is also installed at the discharge end of the green pellet belt conveyor. The pelletizer is a disc pelletizer.

[0017] In this invention, several plow-type unloaders are installed on the batching belt conveyor, and multiple mixing bins are arranged in parallel below the batching belt conveyor. The discharge port at the head of the batching belt conveyor is connected to the inlet of one of the mixing bins. Then, the remaining mixing bins are located below each plow-type unloader. At the same time, a vibrating bucket is installed at the discharge port of each mixing bin. A quantitative belt feeder is installed below the vibrating bucket and connected to the feed end of the pelletizer.

[0018] In this invention, each pelletizing series consists of one mixing silo, one quantitative belt feeder, and one disc pelletizer. The mixture from the high-intensity mixer, along with green pellet return material, is transported to the pelletizer and then distributed to each mixing trough via a plow-type unloader. The feeding equipment under the troughs uses a quantitative feeder (variable frequency speed control), whose feed rate can be automatically adjusted according to a set value. The mixture rolls and grows into pellets under suitable moisture conditions in the pelletizer. Due to centrifugal force and gravity, the pellets automatically overflow from the disc and are conveyed to the screening and distribution system via a green pellet conveyor (e.g., the effective volume of a single mixing trough is approximately 25 m³). 3 Storage time is 30-45 minutes, using The disc pelletizing machine features frequency conversion speed regulation and adjustable disc tilt angle (manual adjustment). The residence time of materials in the disc can be adjusted by changing the disc tilt angle and rotation speed. The output of qualified raw pellets per unit is 20-25 t / h.

[0019] Preferably, the material distribution unit includes a roller screen, a roller screen distributor, and a bottom material hopper. The feed end of the roller screen is connected to the discharge end of the green ball belt conveyor. The undersize material outlet of the roller screen is connected to the feed end of the roller screen distributor via a wide belt conveyor. The oversize material outlet of the roller screen distributor is connected to the feed end of the calcination and cooling unit via an oversize chute. The bottom material hopper is arranged parallel to the roller screen distributor, and its bottom outlet is connected to the feed end of the calcination and cooling unit via a bottom material distribution device. The connection point between the two is upstream of the connection point between the oversize chute of the roller screen distributor and the feed end of the calcination and cooling unit. Preferably, both the oversize material outlet of the roller screen and the undersize material outlet of the roller screen distributor are connected to the feed end of the mixing belt conveyor via a return belt conveyor.

[0020] Preferably, the screen aperture of the roller screen is 20-35 mm, more preferably 25-30 mm. The screen aperture of the roller screen distributor is 10-18 mm, more preferably 12-16 mm.

[0021] In this invention, the screening particle size of green pellets is generally 30mm and 15mm. After passing through a pendulum belt conveyor, the green pellets are evenly distributed onto a roller screen. Unqualified pellets larger than 30mm are removed from the screen. The remaining 30mm green pellets are further homogenized by a wide belt conveyor and transported to a small pellet roller screen distributor (roller screen distributor). Qualified green pellets of 15mm to 30mm are evenly distributed onto the roasting device. Unqualified pellets smaller than 15mm are removed from the screen. A crushing roller is installed at the end of the roller screen to crush large pellets, preventing them from being directly returned to the pelletizing process, which would affect pelletizing efficiency and green pellet quality. Unqualified green pellets are collected and transferred via a return belt conveyor and ultimately returned to the pelletizing system for re-pelleting. An automatic material thickness measuring device is installed above the roasting device to control the material layer thickness by automatically adjusting the operating speed of the roasting device. To protect the roasting equipment, a bottom material laying system is set up, using natural phosphate rock blocks as the bottom material. When there are not enough natural phosphate rock blocks, some finished products can be selected as the bottom material.

[0022] Preferably, according to the material flow direction, the calcination cooling unit includes a drying section 1, a drying section 2, a preheating section, a calcination homogenization section, a cooling section 1, and a cooling section 2 arranged in series. Each of the drying sections 1, 2, preheating, calcination homogenization, cooling section 1, and cooling section 2 is covered with a wind hood and has an independent air box at its bottom. Preferably, a material hopper is also provided below each air box. A double-layer ash discharge valve is also provided inside each air box. The feed end of the drying section 1 is connected to the chute of the roller screen distributor and the discharge end of the bottom material spreading device.

[0023] Preferably, the system also includes a hot air utilization unit, which comprises a cooling fan, a regenerating fan, a drying exhaust fan, a main exhaust fan, a multi-tube dust collector, a first bag filter, a second bag filter, a pipeline heater, and several air supply pipes. The cooling fan is connected to the bottom air inlet of the second cooling section via a first air supply pipe and to the bottom air inlet of the first cooling section via a second air supply pipe. 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 supply pipe. The bottom air outlet of the first drying section is connected to the air inlet of the first bag filter via a fourth air supply pipe. The air outlet of the first bag filter is connected to the chimney via a fifth air supply pipe, and a drying exhaust fan is mounted on the fifth air supply pipe. The top air outlet of the first cooling section is connected to the top air inlet of the calcination homogenization section via a sixth air supply pipe and to the top air inlet of the preheating section via a seventh air supply pipe. A pipeline heater is mounted on the sixth air supply pipe. The bottom air outlet of the roasting homogenization section is connected to the air inlet of the multi-tube dust collector via the eighth air supply pipe. The air outlet of the multi-tube dust collector is connected to the top air inlet of the second drying section via the ninth air supply pipe. A regenerating fan is installed on the ninth air supply pipe. The bottom air outlet of the preheating section is connected to the air inlet of the first bag filter via the tenth air supply pipe. The bottom air outlet of the second drying section is connected to the air inlet of the second bag filter via the eleventh air supply pipe. The air outlet of the second bag filter is connected to the desulfurization and denitrification unit via the twelfth air supply pipe. A main exhaust fan is installed on the twelfth air supply pipe.

[0024] In this invention, green pellets undergo drying, thermal solidification, and cooling processes sequentially in the roasting and cooling unit. The roasting and cooling unit is equipped with a fixed screen to sieve the roasted product, removing materials <5mm, which are then collected, transferred, and returned to the original ore stockpile. Materials ≥5mm are treated as finished products; most are transferred to the electric furnace system for the production of yellow phosphorus, while a small portion is recycled as bottom material to the bottom material hopper at the feeding end of the roasting device (e.g., a grate-type thermal solidification machine with specifications of 4.7×63m, a material layer thickness of 240mm on the grate (including an 80mm bottom material thickness), and a total residence time of approximately 40–15 minutes). Furthermore, a pipeline heating furnace is installed to supplement the system with heat. The roasting device employs a heat-cascade utilization hot air unit, using cold air to carry heat from the cooling section, forming high-temperature flue gas at different temperatures. This recovers waste heat from the system, which is then used as heat for the preceding drying and thermal solidification processes, thereby reducing fuel consumption. The loose pellets entrained in the roasting unit, the dust collected in the bellows, and the material underscreened at the tail end are collectively referred to as bulk materials. These bulk materials will be collected, transported, and returned to the raw material storage yard. During the cascade utilization of high-temperature flue gas, a high-temperature multi-tube dust collector will be installed to remove dust from the flue gas to protect the circulating fan. After cascade utilization, the flue gas will eventually form a portion of low-temperature flue gas, of which the flue gas from the drying section and the preheating section does not contain NO. XPollutants such as SO2 are removed from this portion of the flue gas by a bag filter to remove dust, and then it is directly discharged into the atmosphere through a drying exhaust fan; in addition to dust, the flue gas from the second drying stage also contains NO. X Pollutants such as SO2 are removed by a bag filter and then further purified by a desulfurization and denitrification unit before being discharged. The dust concentration at the bag filter outlet is ≤10mg / Nm³. 3 The dust collected by each dust collector is returned to the dust batching silo in the batching area via a pneumatic conveying system for recycling as raw materials.

[0025] Preferably, the system also includes a finished product screening unit, which comprises 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 port of the fixed screen via a finished product belt conveyor. The first discharge port of the three-way feeder is connected to a finished product inclined belt conveyor. The second discharge port of the three-way feeder is connected to the feed end of the bottom material silo via a bottom material inclined belt conveyor. Preferably, a natural phosphate ore silo is also provided on the bottom material inclined belt conveyor.

[0026] Preferably, the system also includes a bulk material collection unit, which comprises a bulk material belt conveyor, a bulk material inclined belt conveyor, and a bulk material silo. The feed end of the bulk material belt conveyor is connected to both the undersize discharge chute of the fixed screen and the discharge ports of all bulk material hoppers. The discharge end of the bulk material belt conveyor is connected to the bulk material silo via the bulk material inclined belt conveyor.

[0027] In this invention, a silo wall vibrator and an electro-hydraulic sector valve are installed at the bottom outlet of the bulk material silo. The collected bulk material is lowered into the bulk material conveying mechanism (e.g., a bulk material transport vehicle) through the electro-hydraulic sector valve, and the bulk material is returned to the bulk material buffer silo through the bulk material conveying mechanism.

[0028] Preferably, the system further includes a dust collection unit, which comprises a first dust pneumatic conveying pipe, a second dust pneumatic conveying pipe, and a third dust pneumatic conveying pipe. The inlet end of the first dust pneumatic conveying pipe is connected to the dust outlet of a multi-tube dust collector, and its other end is connected to the inlet of a dust hopper. The inlet end of the second dust pneumatic conveying pipe is connected to the dust outlet of a first bag filter, and its other end is connected to the inlet of a dust hopper. The inlet end of the third dust pneumatic conveying pipe is connected to the dust outlet of a second bag filter, and its other end is connected to the inlet of a dust hopper. Each of the first, second, and third dust pneumatic conveying pipes has an independently installed hopper pump at its inlet end.

[0029] According to a second embodiment of the present invention, a method for roasting pellets by co-processing mixed phosphate rock is provided:

[0030] A method for roasting pellets from mixed phosphate rock co-processing, or a method for roasting pellets from mixed phosphate rock co-processing using the system described in the first embodiment, the method comprising:

[0031] 1) Mix high-calcium phosphate rock powder, high-silica phosphate rock powder, and optional bulk materials to obtain mixed mineral powder. Then, grind the mixed mineral powder to obtain fine phosphate rock powder.

[0032] 2) Mix fine phosphate rock powder, phosphorus-containing dust (phosphorus-containing dust collected in the system) and biomass straw pellets in proportion to obtain pelletizing mixture.

[0033] 3) The pelletizing mixture is added to the pelletizer for pelletizing, and the resulting green pellets are screened to obtain large, medium, and small pellets. The large and small pellets are crushed and returned to step 2) for further mixing. The medium pellets proceed to the next process.

[0034] 4) The pellets obtained in step 3) are fed into the roasting device for roasting. The roasted finished pellets are then cooled and screened before being transported to the finished product warehouse for storage.

[0035] 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% and a CaO content of no less than 40 wt%. More preferably, it is a phosphate rock powder with a P2O5 content of 10-15 wt% and a CaO content of 45-55 wt%.

[0036] 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% and a SiO2 content of no less than 40 wt%. More preferably, it is a phosphate rock powder with a P2O5 content of 10-15 wt% and a SiO2 content of 45-55 wt%.

[0037] Preferably, 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, preferably not greater than 0.125 mm. The amount of bulk material added is 3-12% of the total mass of high-calcium phosphate rock powder and high-silica phosphate rock powder, more preferably 5-10%.

[0038] Preferably, in step 2), the mixing mass ratio of the mixed mineral powder, phosphorus-containing dust, and biomass straw pellets is 85-90:5-10:5-9. Preferably, the biomass straw pellets are modified biomass straw pellets treated with calcium hydroxide solution. For example, biomass straw pellets (including but not limited to corn straw, sorghum straw, rice straw, reed straw, etc.) are soaked in a calcium hydroxide solution (e.g., 0.01-1 mol / L) for 0.1-5 hours, then filtered dry before being added to the batch.

[0039] Preferably, in step 3), the particle size of the medium-sized spheres is 5-20 mm, more preferably 8-16 mm. Clusters with a particle size larger than the medium-sized spheres are called large spheres, and clusters with a particle size smaller than the medium-sized spheres are called small spheres.

[0040] 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.

[0041] Preferably, natural phosphate rock lumps are used as the base material during the roasting process. The particle size of the natural phosphate rock lumps is 15-30 mm, preferably 20-25 mm. The P2O5 content in the natural phosphate rock lumps is 15-25%, preferably 18-20%. The thickness of the base material is 50-85 mm, preferably 60-75 mm. The thickness of the material layer for the intermediate pellets is 100-200 mm, preferably 120-180 mm.

[0042] In this invention, high-calcium phosphate rock and high-silicon phosphate rock are mixed and ground, which greatly expands the range of raw materials. High-silicon phosphate rock has low hardness and is relatively easy to grind, but after fine grinding, it has poor hydrophilicity and a low static pelletizing index (generally less than 0.25), resulting in weak pelletizing. High-calcium phosphate rock has high hardness and is relatively difficult to grind, but after fine grinding, it has good hydrophilicity and a large static pelletizing index (generally greater than 0.5), resulting in better pelletizing. After fine grinding, the pelletizing index is generally greater than 0.35, and the green pellet strength can be met without the addition of binders. By combining high-hardness and low-hardness mineral powders, the grinding process uses material to grind material, reducing grinding energy consumption. At the same time, the acidity can be well adjusted, and the acidity of the obtained pellets is generally greater than 0.85, which can reduce the amount of flux added in subsequent electric furnace phosphorus production.

[0043] In this invention, by adding biomass straw bins to the batching unit, the biomass straw is distributed in the green pellets, providing diffusion channels for internal moisture during drying and greatly increasing the rate of water vapor escape. At the same time, the biomass straw fibers in the green pellets can improve the adhesion between phosphate rock powder particles, thereby increasing the strength of the green pellets. In addition, the biomass straw in the green pellets provides some heat during subsequent roasting, which helps the green pellets to solidify at high temperatures, further improving their physical strength and chemical properties.

[0044] 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.

[0045] In this invention, a high-powered mixer is used for mixing and granulation, which can improve the granulation effect, resulting in better particle size distribution and better granule strength.

[0046] In this invention, the low-temperature bulk material is mixed with phosphate rock powder and then finely ground. Under the action of high-strength low-temperature calcined pellets, the energy consumption of fine grinding can be further reduced, the efficiency of fine grinding can be further improved, and the effect of fine grinding can be further enhanced.

[0047] In this invention, the synergistic processing of phosphate rock with high calcium content and phosphate rock with high silicon content is achieved by mixing the two in a certain proportion. This can increase the pelleting properties of the materials. In addition, the chemical properties of the two are different, which can further improve the roasting intensity of the pellets.

[0048] In this invention, the hot air generated during cooling is recycled to provide heat for drying, preheating, and other processes. Furthermore, waste heat is fully recovered through cascade utilization. The exhausted exhaust gas is discharged after dust removal, desulfurization, and denitrification, significantly reducing heating energy consumption and increasing environmental benefits. In addition, various bulk materials and dust generated in the system are recycled, realizing the recovery and utilization of valuable resources while avoiding direct discharge that pollutes the environment.

[0049] In this invention, each belt conveyor (a belt conveyor for material transport) consists of one or more conveyors connected in series, and each conveyor may or may not be equipped with a weighing mechanism (such as a metering scale).

[0050] In this invention, the raw material blocks need to undergo transportation and heat treatment to become finished phosphate ore blocks, with roasting temperatures exceeding 1000℃. This requires the raw material blocks to possess sufficient strength to prevent excessive breakage during transportation and significant bursting during heat treatment. Therefore, this invention incorporates biomass straw into the raw material blocks. The biomass straw is distributed throughout the raw material blocks, providing diffusion channels for internal moisture during drying, significantly increasing the rate of water vapor escape and effectively preventing bursting caused by rapid evaporation of water molecules at high temperatures. Simultaneously, the fibers of the biomass straw in the raw material blocks enhance the adhesion between phosphate ore particles, improving the strength of the biomass blocks. Furthermore, the biomass straw in the biomass blocks provides some heat during subsequent roasting, facilitating high-temperature consolidation of the raw material blocks and further improving their physical strength and chemical properties.

[0051] 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.

[0052] In this invention, the height of the high-calcium phosphate rock powder buffer silo, the high-silica phosphate rock powder buffer silo, and the bulk material buffer silo 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.

[0053] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0054] 1. This invention effectively solves the problem of resource waste caused by the inability to reuse phosphate rock powder in existing phosphate rock processing. At the same time, it realizes the synergistic treatment of different types of low-grade phosphate rock powder, solves the problem of land resource waste caused by the narrow source of phosphate rock powder and large-scale stockpiling in existing phosphate rock processing, realizes the resource reuse of phosphate rock powder, and also greatly saves land resources.

[0055] 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.

[0056] 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

[0057] Figure 1 This is a schematic diagram showing the connection relationship between the various units of the system described in this invention.

[0058] Figure 2 This is a schematic diagram of the structure of the mixed phosphate rock pretreatment unit and the batching unit of the system described in this invention.

[0059] Figure 3 This is a schematic diagram of the structure of the ball-forming unit of the system described in this invention.

[0060] Figure 4 This is a schematic diagram of the structure of the material feeding unit, roasting and cooling unit, and finished product screening unit of the system described in this invention.

[0061] Figure reference numerals: 1: Mixed phosphate rock pretreatment unit; 101: High-calcium phosphate rock powder buffer silo; 102: High-silica phosphate rock powder buffer silo; 103: Bulk material buffer silo; 104: First inclined belt conveyor; 105: Vertical mill; 106: Flue gas furnace; 107: Flue gas pipe; 108: Discharge duct; 109: Pulse belt dust collector; 110: Explosion-proof duct; 111: Iron separator; 112: Explosion-proof valve; 113: Pulverized coal fan; 114: External exhaust duct; 15: Desulfurization and denitrification device;

[0062] 2: Batching unit; 201: Mixed powder silo; 202: Biomass straw silo; 203: Dust silo; 204: Screw feeder; 205: Batching belt conveyor; 206: Dust receiving device;

[0063] 3: Pelletizing unit; 301: High-intensity mixer; 302: Mixing silo; 303: Pelletizer; 304: Mixing belt conveyor; 305: Plow-type unloader; 306: Green pellet belt conveyor; 307: Measuring scale;

[0064] 4: Fabric spreading unit; 401: Roller screener; 402: Roller screener distributor; 403: Bottom material silo; 404: Wide belt conveyor; 405: Bottom material spreading device; 406: Return belt conveyor;

[0065] 5: Calcination and cooling unit; 501: Drying stage 1; 502: Drying stage 2; 503: Preheating stage; 504: Calcination homogenization stage; 505: Cooling stage 1; 506: Cooling stage 2; 507: Air hood; 508: Air box; 509: Bulk hopper; 510: Double-layer ash discharge valve;

[0066] 6: Hot air utilization unit; 601: Cooling fan; 602: Regenerating fan; 603: Drying exhaust fan; 604: Main exhaust fan; 605: Multi-tube dust collector; 606: First bag filter; 607: Second bag filter; 608: Pipeline heating furnace;

[0067] 7: Finished product screening unit; 701: Fixed screen; 702: Three-way feeder; 703: Finished product belt conveyor; 704: Finished product steep-angle belt conveyor; 705: Bottom material steep-angle belt conveyor; 706: Natural phosphate ore bin;

[0068] 8: Bulk material collection unit; 801: Bulk material belt conveyor; 802: Bulk material steep-angle belt conveyor; 803: Bulk material bin;

[0069] 9: Dust collection unit; 901: First dust pneumatic conveying pipeline; 902: Second dust pneumatic conveying pipeline; 903: Third dust pneumatic conveying pipeline; 904: Silo pump.

[0070] L1: First air supply duct; L2: Second air supply duct; L3: Third air supply duct; L4: Fourth air supply duct; L5: Fifth air supply duct; L6: Sixth air supply duct; L7: Seventh air supply duct; L8: Eighth air supply duct; L9: Ninth air supply duct; L10: Tenth air supply duct; L11: Eleventh air supply duct; L12: Twelfth air supply duct. Detailed Implementation

[0071] 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.

[0072] A pellet roasting system for co-processing mixed phosphate rock includes a mixed phosphate rock pretreatment unit 1, a batching unit 2, a pelletizing unit 3, a feeding unit 4, and a roasting and cooling unit 5. These units are connected in series according to the material flow. The mixed phosphate rock pretreatment unit 1 includes a high-calcium phosphate rock powder buffer silo 101, a high-silica phosphate rock powder buffer silo 102, and a bulk material buffer silo 103 arranged in parallel. The discharge ends of the high-calcium phosphate rock powder buffer silo 101, the high-silica phosphate rock powder buffer silo 102, and the bulk material buffer silo 103 are all connected to the feed end of a vertical mill 105 via a first large-angle belt conveyor 104. A flue gas furnace 106 is installed on one side of the vertical mill 105, and the exhaust port of the flue gas furnace 106 is connected to the air inlet of the vertical mill 105 via a flue gas pipe 107. The discharge port of the vertical mill 105 is connected to the inlet of the pulse belt dust collector 109 via the discharge duct 108. The bottom discharge end of the pulse belt dust collector 109 is connected to the inlet of the batching unit 2. Preferably, the first steeply inclined belt conveyor 104 is also equipped with an iron separator 111.

[0073] Preferably, an explosion-proof duct 110 is also led out from the discharge duct 108, and an explosion-proof valve 112 is provided on the explosion-proof duct 110.

[0074] Preferably, the exhaust port of the pulse belt dust collector 109 is connected to the desulfurization and denitrification device 115 through the pulverized coal fan 113 and the external exhaust pipe 114.

[0075] Preferably, the batching unit 2 includes a mixing powder silo 201, a biomass straw silo 202, and a dust silo 203. The feed end of the mixing powder silo 201 is connected to the bottom discharge end of the pulse belt dust collector 109 via a screw feeder 204. The discharge ends of the mixing powder silo 201, the biomass straw silo 202, and the dust silo 203 are all connected to the feed end of the pelletizing unit 3 via a batching belt conveyor 205. Preferably, the feed end of the dust silo 203 is also equipped with a dust receiving device 206.

[0076] Preferably, the pelletizing unit 3 includes a high-intensity mixer 301, a mixing silo 302, and a pelletizer 303. The feed end of the high-intensity mixer 301 is connected to the discharge end of the batching belt conveyor 205. The discharge end of the high-intensity mixer 301 is simultaneously connected to the feed ends of multiple mixing silos 302 via a mixing belt conveyor 304 and several plow-type unloaders 305. A pelletizer 303 is installed below the discharge port of each mixing silo 302. The discharge ends of all pelletizers 303 are connected to the feed end of the fabric distribution unit 4 via a green pellet belt conveyor 306. Preferably, a weighing scale 307 is also installed at the discharge end of the green pellet belt conveyor 306. The pelletizer 303 is a disc pelletizer.

[0077] Preferably, the material distribution unit 4 includes a roller screen 401, a roller screen distributor 402, and a bottom material hopper 403. The feed end of the roller screen 401 is connected to the discharge end of the green ball belt conveyor 306. The undersize material outlet of the roller screen 401 is connected to the feed end of the roller screen distributor 402 via a wide belt conveyor 404. The oversize material outlet of the roller screen distributor 402 is connected to the feed end of the calcination and cooling unit 5 via an oversize chute. The bottom material hopper 403 is arranged parallel to the roller screen distributor 402, and its bottom outlet is connected to the feed end of the calcination and cooling unit 5 via a bottom material distribution device 405. The connection point between the two is upstream of the connection point between the oversize chute of the roller screen distributor 402 and the feed end of the calcination and cooling unit 5. Preferably, the oversize material outlet of the roller screen 401 and the undersize material outlet of the roller screen distributor 402 are both connected to the feed end of the mixing belt conveyor 304 via the return belt conveyor 406.

[0078] Preferably, the screen aperture of the roller screen 401 is 20-35 mm, more preferably 25-30 mm. The screen aperture of the roller screen distributor 402 is 10-18 mm, more preferably 12-16 mm.

[0079] Preferably, according to the material flow, the calcination cooling unit 5 includes a drying section 501, a drying section 502, a preheating section 503, a calcination homogenization section 504, a cooling section 505, and a cooling section 506 arranged in series. Each of the drying sections 501, 502, 503, 504, 505, and 506 is covered by a wind hood 507 and has an independent wind box 508 at its bottom. Preferably, a material hopper 509 is also provided below each wind box 508. A double-layer ash discharge valve 510 is also provided inside each wind box 508. The feed end of the drying section 501 is connected to the chute of the roller screen distributor 402 and the discharge end of the bottom material distribution device 405.

[0080] Preferably, the system further includes a hot air utilization unit 6, which includes a cooling fan 601, a regenerating fan 602, a drying exhaust fan 603, a main exhaust fan 604, a multi-tube dust collector 605, a first bag filter 606, a second bag filter 607, a pipeline heating furnace 608, and several air supply pipes. The cooling fan 601 is connected to the bottom air inlet of the second cooling section 506 via the first air supply pipe L1 and to the bottom air inlet of the first cooling section 505 via the second air supply pipe L2. The top air outlet of the second cooling section 506 is connected to the top air inlet of the first drying section 501 via the third air supply pipe L3. The bottom air outlet of the first drying section 501 is connected to the air inlet of the first bag filter 606 via the fourth air supply pipe L4. The air outlet of the first bag filter 606 is connected to the chimney via the fifth air supply pipe L5. A drying exhaust fan 603 is installed on the fifth air supply pipe L5. The top air outlet of the first cooling section 505 is connected to the top air inlet of the roasting homogenization section 504 via the sixth air supply pipe L6 and to the top air inlet of the preheating section 503 via the seventh air supply pipe L7. A pipe heating furnace 608 is installed on the sixth air supply pipe L6. The bottom air outlet of the roasting homogenization section 504 is connected to the air inlet of the multi-tube dust collector 605 via the eighth air supply pipe L8. The air outlet of the multi-tube dust collector 603 is connected to the top air inlet of the drying section 502 via the ninth air supply pipe L9. A regenerating fan 602 is installed on the ninth air supply pipe L9. The bottom air outlet of the preheating section 503 is connected to the air inlet of the first bag filter 606 via the tenth air supply pipe L10. The bottom air outlet of the drying section 502 is connected to the air inlet of the second bag filter 607 via the eleventh air supply pipe L11. The air outlet of the second bag filter 607 is connected to the desulfurization and denitrification device 115 via the twelfth air supply pipe L12. A main exhaust fan 604 is installed on the twelfth air supply pipe L12.

[0081] Preferably, the system further includes a finished product screening unit 7, which includes a fixed screen 701 and a three-way feeder 702. The feed end of the fixed screen 701 is connected to the discharge end of the cooling section 506. The feed end of the three-way feeder 702 is connected to the discharge port of the fixed screen 701 via a finished product belt conveyor 703. The first discharge port of the three-way feeder 702 is connected to a finished product inclined belt conveyor 704. The second discharge port of the three-way feeder 702 is connected to the feed end of a bottom material inclined belt conveyor 705 connected to a bottom material bin 403. Preferably, a natural phosphate ore bin 706 is also provided on the bottom material inclined belt conveyor 705.

[0082] Preferably, the system also includes a bulk material collection unit 8, which comprises a bulk material belt conveyor 801, a bulk material inclined belt conveyor 802, and a bulk material hopper 803. The feed end of the bulk material belt conveyor 801 is connected to the undersize discharge chute of the fixed screen 701 and the discharge ports of all bulk material hoppers 509. The discharge end of the bulk material belt conveyor 801 is connected to the bulk material hopper 803 via the bulk material inclined belt conveyor 802.

[0083] Preferably, the system further includes a dust collection unit 9, which comprises a first dust pneumatic conveying pipe 901, a second dust pneumatic conveying pipe 902, and a third dust pneumatic conveying pipe 903. The inlet end of the first dust pneumatic conveying pipe 901 is connected to the dust outlet of the multi-tube dust collector 605, and its other end is connected to the inlet of the dust hopper 203. The inlet end of the second dust pneumatic conveying pipe 902 is connected to the dust outlet of the first bag filter 606, and its other end is connected to the inlet of the dust hopper 203. The inlet end of the third dust pneumatic conveying pipe 903 is connected to the dust outlet of the second bag filter 607, and its other end is connected to the inlet of the dust hopper 203. Each of the first, second, and third dust pneumatic conveying pipes 901, 902, and 903 is independently equipped with a hopper pump 904.

[0084] Example 1

[0085] like Figure 1-4 The system describes a pellet roasting system for co-processing mixed phosphate rock. The system includes a mixed phosphate rock pretreatment unit 1, a batching unit 2, a pelletizing unit 3, a feeding unit 4, and a roasting and cooling unit 5. These units are connected in series according to the material flow. The mixed phosphate rock pretreatment unit 1 includes a high-calcium phosphate rock powder buffer silo 101, a high-silica phosphate rock powder buffer silo 102, and a bulk material buffer silo 103, all arranged in parallel. The discharge ends of the high-calcium phosphate rock powder buffer silo 101, the high-silica phosphate rock powder buffer silo 102, and the bulk material buffer silo 103 are all connected to the feed end of a vertical mill 105 via a first large-angle belt conveyor 104. A flue gas furnace 106 is located on one side of the vertical mill 105, and the exhaust port of the flue gas furnace 106 is connected to the air inlet of the vertical mill 105 via a flue gas pipe 107. The discharge port of the vertical mill 105 is connected to the inlet of the pulse belt dust collector 109 via the discharge duct 108. The bottom discharge end of the pulse belt dust collector 109 is connected to the inlet of the batching unit 2. A magnetic separator 111 is also installed on the first steepest angle belt conveyor 104.

[0086] Example 2

[0087] The same as in Example 1, except that an explosion-proof duct 110 is also extended from the discharge duct 108, and an explosion-proof valve 112 is installed on the explosion-proof duct 110.

[0088] Example 3

[0089] Example 2 is repeated, except that the exhaust port of the pulse belt dust collector 109 is connected to the desulfurization and denitrification device 115 through the pulverized coal fan 113 and the external exhaust pipe 114.

[0090] Example 4

[0091] The embodiment 3 is repeated, except that the batching unit 2 includes a mixing powder silo 201, a biomass straw silo 202, and a dust silo 203. The feed end of the mixing powder silo 201 is connected to the bottom discharge end of the pulse belt dust collector 109 via a screw feeder 204. The discharge ends of the mixing powder silo 201, the biomass straw silo 202, and the dust silo 203 are all connected to the feed end of the pelletizing unit 3 via a batching belt conveyor 205.

[0092] Example 5

[0093] The embodiment 4 is repeated, except that a dust receiving device 206 is also provided at the feed end of the dust bin 203.

[0094] Example 6

[0095] The embodiment 5 is repeated, except that the pelletizing unit 3 includes a high-intensity mixer 301, a mixing silo 302, and a pelletizer 303. The feed end of the high-intensity mixer 301 is connected to the discharge end of the batching belt conveyor 205. The discharge end of the high-intensity mixer 301 is simultaneously connected to the feed ends of multiple mixing silos 302 via a mixing belt conveyor 304 and several plow-type unloaders 305. A pelletizer 303 is installed below the discharge port of each mixing silo 302. The discharge ends of all pelletizers 303 are connected to the feed end of the fabric distribution unit 4 via a green pellet belt conveyor 306.

[0096] Example 7

[0097] Example 6 is repeated, except that a weighing scale 307 is also installed at the discharge end of the green pellet conveyor 306. The pelletizer 303 is a disc pelletizer.

[0098] Example 8

[0099] The embodiment 7 is repeated, except that the material distribution unit 4 includes a roller screen 401, a roller screen distributor 402, and a bottom material hopper 403. The feed end of the roller screen 401 is connected to the discharge end of the green ball belt conveyor 306. The undersize material outlet of the roller screen 401 is connected to the feed end of the roller screen distributor 402 via a wide belt conveyor 404. The oversize material outlet of the roller screen distributor 402 is connected to the feed end of the calcination and cooling unit 5 via an oversize chute. The bottom material hopper 403 is arranged side by side with the roller screen distributor 402, and its bottom outlet is connected to the feed end of the calcination and cooling unit 5 via a bottom material distribution device 405. The connection point between the two is upstream of the connection point between the oversize chute of the roller screen distributor 402 and the feed end of the calcination and cooling unit 5.

[0100] Example 9

[0101] Example 8 is repeated, except that the oversize material outlet of the roller screen 401 and the undersize material outlet of the roller screen distributor 402 are both connected to the feed end of the mixing belt conveyor 304 via the return belt conveyor 406.

[0102] Example 10

[0103] Example 9 is repeated, except that the screen aperture of roller screen 401 is 30mm. The screen aperture of roller screen distributor 402 is 15mm.

[0104] Example 11

[0105] Repeating Example 10, except that, according to the material flow, the calcination cooling unit 5 includes a drying section 501, a drying section 502, a preheating section 503, a calcination homogenization section 504, a cooling section 505, and a cooling section 506 arranged in series. Each of the drying sections 501, 502, 503, 504, 505, and 506 is covered by a wind hood 507 and has an independent wind box 508 at its bottom. A material hopper 509 is also provided below each wind box 508. A double-layer ash discharge valve 510 is also provided inside each wind box 508. The feed end of the drying section 501 is connected to the chute of the roller screen distributor 402 and the discharge end of the bottom material distribution device 405.

[0106] Example 12

[0107] The system repeats Embodiment 11, except that it further includes a hot air utilization unit 6, which includes a cooling fan 601, a regenerating fan 602, a drying exhaust fan 603, a main exhaust fan 604, a multi-tube dust collector 605, a first bag filter 606, a second bag filter 607, a pipeline heating furnace 608, and several air supply pipes. The cooling fan 601 is connected to the bottom air inlet of the second cooling section 506 via the first air supply pipe L1 and to the bottom air inlet of the first cooling section 505 via the second air supply pipe L2. The top air outlet of the second cooling section 506 is connected to the top air inlet of the first drying section 501 via the third air supply pipe L3. The bottom air outlet of the first drying section 501 is connected to the air inlet of the first bag filter 606 via the fourth air supply pipe L4. The air outlet of the first bag filter 606 is connected to the chimney via the fifth air supply pipe L5. A drying exhaust fan 603 is installed on the fifth air supply pipe L5. The top air outlet of the first cooling section 505 is connected to the top air inlet of the roasting homogenization section 504 via the sixth air supply pipe L6 and to the top air inlet of the preheating section 503 via the seventh air supply pipe L7. A pipe heating furnace 608 is installed on the sixth air supply pipe L6. The bottom air outlet of the roasting homogenization section 504 is connected to the air inlet of the multi-tube dust collector 605 via the eighth air supply pipe L8. The air outlet of the multi-tube dust collector 603 is connected to the top air inlet of the drying section 502 via the ninth air supply pipe L9. A regenerating fan 602 is installed on the ninth air supply pipe L9. The bottom air outlet of the preheating section 503 is connected to the air inlet of the first bag filter 606 via the tenth air supply pipe L10. The bottom air outlet of the drying section 502 is connected to the air inlet of the second bag filter 607 via the eleventh air supply pipe L11. The air outlet of the second bag filter 607 is connected to the desulfurization and denitrification device 115 via the twelfth air supply pipe L12. A main exhaust fan 604 is installed on the twelfth air supply pipe L12.

[0108] Example 13

[0109] The system repeats Embodiment 12, except that it also includes a finished product screening unit 7, which includes a fixed screen 701 and a three-way feeder 702. The feed end of the fixed screen 701 is connected to the discharge end of the cooling section 506. The feed end of the three-way feeder 702 is connected to the discharge port of the fixed screen 701 via a finished product belt conveyor 703. The first discharge port of the three-way feeder 702 is connected to a finished product inclined belt conveyor 704. The second discharge port of the three-way feeder 702 is connected to the feed end of a bottom material silo 403 via a bottom material inclined belt conveyor 705. A natural phosphate ore silo 706 is also provided on the bottom material inclined belt conveyor 705.

[0110] Example 14

[0111] The system repeats Embodiment 13, except that it also includes a bulk material collection unit 8, which comprises a bulk material belt conveyor 801, a bulk material inclined belt conveyor 802, and a bulk material silo 803. The feed end of the bulk material belt conveyor 801 is connected to both the undersize discharge chute of the fixed screen 701 and the discharge ports of all bulk material hoppers 509. The discharge end of the bulk material belt conveyor 801 is connected to the bulk material silo 803 via the bulk material inclined belt conveyor 802.

[0112] Example 15

[0113] The system repeats Embodiment 14, except that it further includes a dust collection unit 9, which comprises a first dust pneumatic conveying pipe 901, a second dust pneumatic conveying pipe 902, and a third dust pneumatic conveying pipe 903. The inlet end of the first dust pneumatic conveying pipe 901 is connected to the dust outlet of the multi-tube dust collector 605, and its other end is connected to the inlet of the dust hopper 203. The inlet end of the second dust pneumatic conveying pipe 902 is connected to the dust outlet of the first bag filter 606, and its other end is connected to the inlet of the dust hopper 203. The inlet end of the third dust pneumatic conveying pipe 903 is connected to the dust outlet of the second bag filter 607, and its other end is connected to the inlet of the dust hopper 203. Each of the first, second, and third dust pneumatic conveying pipes 901, 902, and 903 is independently equipped with a hopper pump 904.

[0114] Example 16

[0115] A method for roasting pellets from mixed phosphate rock in a co-processing manner, the method comprising:

[0116] 1) Mix high-calcium phosphate rock powder, high-silica phosphate rock powder, and optional bulk materials to obtain mixed mineral powder. Then, grind the mixed mineral powder to obtain fine phosphate rock powder.

[0117] 2) Mix fine phosphate rock powder, phosphorus-containing dust and biomass straw pellets in proportion to obtain pelletizing mixture.

[0118] 3) The pelletizing mixture is added to the pelletizer for pelletizing, and the resulting green pellets are screened to obtain large, medium, and small pellets. The large and small pellets are crushed and returned to step 2) for further mixing. The medium pellets proceed to the next process.

[0119] 4) The pellets obtained in step 3) are fed into the roasting device for roasting. The roasted finished pellets are then cooled and screened before being transported to the finished product warehouse for storage.

[0120] Example 17

[0121] Example 16 is repeated, except that in step 1), the high-calcium phosphate rock powder is a phosphate rock powder with a P2O5 content of 10-15 wt% and a CaO content of 45-55 wt%. The high-silica phosphate rock powder is a phosphate rock powder with a P2O5 content of 10-15 wt% and a SiO2 content of 45-55 wt%. 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. The amount of bulk material added is 5%-10% of the total mass of high-calcium phosphate rock powder and high-silica phosphate rock powder.

[0122] Example 18

[0123] Repeat Example 17, except that in step 2), the mixing mass ratio of the mixed mineral powder, phosphorus-containing dust, and biomass straw pellets is 85-90:5-10:5-9.

[0124] In step 3), the particle size of the medium-sized spheres is 5-20 mm. Clusters with a particle size larger than the medium-sized spheres are called large spheres, and clusters with a particle size smaller than the medium-sized spheres are called small spheres.

[0125] 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.

[0126] During the roasting process, natural phosphate rock lumps are used as the base material. The particle size of the natural phosphate rock lumps is 15-30 mm. The P2O5 content in the natural phosphate rock lumps is 15-25%. The thickness of the base material is 50-85 mm. The thickness of the intermediate pellet layer is 100-200 mm.

[0127] Application Example 1

[0128] The mixed phosphate rock was processed using the system described in Example 15 and the method described in Example 18.

[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 mixed at a mass ratio of 5.5:4 to obtain mixed mineral powder. The mixed mineral powder was then ground, and the powder with a particle size of less than or equal to 0.125 mm was collected as fine phosphate rock powder.

[0130] Corn stalks are crushed to a particle size of less than 2.5 mm to obtain stalk pellets. Phosphate rock powder, phosphorus-containing dust, and corn stalk pellets are then mixed at a mass ratio of 94:5:1 to obtain a pelletizing mixture. This mixture is fed into a pelletizer for pelletizing, and the resulting green pellets are screened to obtain green pellets with a particle size range of 8-17 mm.

[0131] Natural lump ore with an average particle size of 20mm (P2O5 content of approximately 20.8%) is laid as the base material, with a thickness of 70mm. Then, a layer of green pellets (phosphate rock pellets) is laid on top of the base material, with a thickness of 170mm. After the base material is laid, it is sent to a roasting device and roasted at 1200℃ for 30 minutes. After roasting, the finished pellets are cooled, and clinker pellets ≥5mm are collected as finished phosphate rock pellets and transported to the finished product warehouse for storage.

[0132] Application Example 2

[0133] Repeat Example 1, except that 7% of the mass of the mixed mineral powder is added to the mixed mineral powder.

[0134] Application Example 3

[0135] The application of Example 1 was repeated, except that high-calcium phosphate rock powder and high-silica phosphate rock powder were mixed at a mass ratio of 5:4.

[0136] Application Example 4

[0137] The modified straw pellets were obtained by repeating Example 1, except that before mixing the straw pellets with the phosphate rock powder, they were first soaked in a 0.02 mol / L calcium hydroxide solution for 1 hour and then filtered dry.

[0138] Comparative Example 1

[0139] Repeat Example 1, but only use high-calcium phosphate rock powder.

[0140] Comparative Example 2

[0141] Repeat Example 1, but only use high-silica phosphate rock powder.

[0142] Comparative Example 3

[0143] The practical application is repeated in Example 1, except that the high-calcium phosphate rock powder and the high-silica phosphate rock powder are mixed in a mass ratio of 1:1.

[0144] Comparative Example 4

[0145] Example 1 was repeated, except that high-calcium phosphate rock powder and high-silica phosphate rock powder were mixed in a mass ratio of 4:5.

[0146] Comparative Example 5

[0147] The application of Example 1 was repeated, except that biomass straw was not used.

[0148] The finished phosphate rock pellets obtained in each of the above application examples and comparative examples were subjected to various quality tests, and the test results are shown in the table below:

[0149]

[0150]

Claims

1. A method for roasting pellets from mixed phosphate rock in a co-processing manner, characterized in that: The method includes: 1) High-calcium phosphate rock powder, high-silica phosphate rock powder, and optional bulk materials are mixed to obtain mixed mineral powder; then the mixed mineral powder is ground to obtain fine phosphate rock powder; the high-calcium phosphate rock powder is phosphate rock powder with a P2O5 content of not more than 15 wt% and a CaO content of not less than 40 wt%; the high-silica phosphate rock powder is phosphate rock powder with a P2O5 content of not more than 15 wt% and a SiO2 content of not less than 40 wt%; the mixing mass ratio of high-calcium phosphate rock powder to high-silica phosphate rock powder is 1.2-1.6:1; 2) Mix fine phosphate rock powder, phosphorus-containing dust and biomass straw pellets in a certain proportion to obtain pelletizing mixture; the mixing mass ratio of mineral powder, phosphorus-containing dust and biomass straw pellets is 85-90:5-10:5-9. 3) Add the pelletizing mixture to the pelletizing machine to form pellets, and screen the obtained green pellets to obtain large, medium 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; 4) The pellets obtained in step 3) are fed into the roasting device for roasting. The roasted pellets are 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 high-calcium phosphate rock powder is phosphate rock powder with a P2O5 content of 10-15wt% and a CaO content of 45-55wt%.

3. 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% and a SiO2 content of 45-55wt%.

4. The method according to claim 1, characterized in that: The mixing mass ratio of high-calcium phosphate rock powder to high-silica phosphate rock powder is 1.3-1.45:

1.

5. The method according to claim 1, characterized in that: The average particle size of the mixed mineral powder is no greater than 0.15 mm.

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

7. The method according to claim 1, characterized in that: The amount of bulk material added is 3-12% of the total mass of high-calcium phosphate rock powder and high-silica phosphate rock powder.

8. The method according to claim 7, characterized in that: The amount of bulk material added is 5-10% of the total mass of high-calcium phosphate rock powder and high-silica phosphate rock powder.

9. The method according to claim 1, characterized in that: In step 2), the biomass straw pellets are modified biomass straw pellets treated with calcium hydroxide solution.

10. The method according to claim 1, characterized in that: In step 3), the particle size of the medium-sized sphere is 5-20 mm; spheres with a particle size larger than the medium-sized sphere are called large spheres, and spheres with a particle size smaller than the medium-sized sphere are called small spheres.

11. The method according to claim 10, characterized in that: In step 3), the particle size of the medium ball is 8-16 mm.

12. The method according to claim 1, 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.

13. The method according to claim 12, 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.

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