Device and method for sintering and grinding limonite into pellet fine powder and removing crystal water

Abstract

The invention discloses a device and a method for sintering and grinding limonite into pellet fine powder and removing crystal water, the device comprises a vertical mill, tuyere rings are arranged around a millstone of the vertical mill, a powder concentrator is arranged above the millstone, a blanking hopper is arranged on the lower side of the powder concentrator, a blanking pipe is arranged in the center of the blanking hopper, and the vertical mill is provided with a coarse powder outlet and a returned material inlet. The blanking hopper is connected with a coarse powder transfer device through a coarse powder outlet, the coarse powder transfer device is connected with an air inlet of the roasting furnace, an air outlet of the roasting furnace is connected with a flue gas inlet, a discharge port of the roasting furnace is connected with a return material inlet through a roasting return material device, and the return material inlet is connected with a blanking pipe. According to the method, the limonite sintering powder with the large particle size is ground into the pellet fine powder through the vertical grinding machine, free water in the limonite sintering powder is removed while the pellet fine powder is ground, part or even all of crystal water in the limonite can be removed with the high heat utilization rate, and the yield of the pellet fine powder is improved. And the adverse effect caused by crystal water release in the pellet roasting process is reduced.

Description

Technical Field

[0001] The invention relates to a pellet preparation process and equipment, in particular to a device and method for grinding limonite sintered powder into pellet concentrate and removing crystal water. Background Art

[0002] Limonite pellet concentrate is one of the raw material varieties for pelletizing. The raw material particle size of 20 mesh accounts for ≥80%. In addition to free water, it also contains a certain proportion of crystal water. The crystal water of limonite pellet concentrate is released during the pellet roasting process, which not only consumes a large amount of high-quality heat, but also increases the risk of pellet explosion. The particle size of limonite sintered powder is generally 0-10mm, and it is generally used as a sintering raw material. If the limonite sintered powder is ground to the particle size of pellet concentrate, by removing part of its crystal water, not only can the price difference between pellet concentrate and sintered powder be obtained, but also due to the reduction of crystal water, the grade of limonite is improved, and the adverse effect of the release of crystal water on the pellet during the pellet roasting process is also reduced.

[0003] Limonite sintered powder generally contains a certain amount of free water and a certain amount of crystal water. In the process of grinding limonite sintered powder into limonite pellet fine powder through vertical mill, in order to prevent the material layer from being compacted and affecting normal grinding, hot air is usually required to remove the free water, so that the moisture content of the finished pellet fine powder is about 1%. After being ground by the grinding roller, the material is thrown to the wind nozzle ring around the grinding disc, and the finer material after being crushed is blown to the powder concentrator by the hot air ejected from the wind nozzle ring for selection. Since the inlet flue gas temperature of the vertical mill is usually 200-300℃, the temperature is relatively low, and in the area of ​​the wind nozzle ring outlet, the water in the material is quickly evaporated, the flue gas temperature quickly drops to 80℃, and the contact time between the material and the high temperature flue gas of 200-300℃ is very short, so it is difficult to remove the crystal water in the material. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a device and method for grinding limonite sintered powder into pellet powder and removing crystal water. The coarse limonite sintered powder is ground into pellet powder by a vertical mill. While grinding the pellet powder, in addition to removing free water in the limonite sintered powder, part or even all of the crystal water in the limonite can be removed with a higher heat utilization rate, thereby improving the iron grade of the limonite pellet powder, reducing the adverse effects of the pellets on the pellets due to the release of crystal water during the pellet roasting process, and increasing the amount of limonite used in the pellets.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A device for grinding sintered limonite into pelletized fine powder and removing crystal water comprises a vertical mill, the vertical mill comprises a grinding disc, a tuyere ring is arranged around the grinding disc, a smoke inlet is arranged on the tuyere ring, a powder classifier is arranged above the grinding disc, a smoke outlet is arranged on the upper side of the powder classifier, the smoke outlet is connected to the air inlet of a bag dust collector, the air outlet of the bag dust collector is connected to a discharge pipeline, the discharge pipeline is provided with a main exhaust fan, a drop hopper is arranged at the lower side of the powder classifier, a discharge pipe is arranged at the center of the drop hopper, a return material outlet is arranged below the tuyere ring, the vertical mill is provided with a coarse powder outlet and a return material inlet, the drop hopper is connected to a coarse powder reverse transportation device through the coarse powder outlet, the coarse powder reverse transportation device is connected to the air inlet of a roasting furnace, the air outlet of the roasting furnace is connected to the smoke inlet, the discharge port of the roasting furnace is connected to the return material inlet through the roasting return device, and the return material inlet is connected to the discharge pipe.

[0006] Furthermore, the bottom of the drop hopper is provided with a buffer groove, the inner wall of the buffer groove is provided with a discharge port, and the outer wall of the buffer groove is connected to the coarse powder outlet.

[0007] Furthermore, the coarse powder transfer device includes a mixer, the feed inlet of the mixer is connected to the coarse powder outlet, the air inlet of the mixer is connected to the discharge pipeline of the main exhaust fan outlet, and the discharge port of the mixer is connected to the air inlet of the roasting furnace.

[0008] Furthermore, the roasting furnace includes a vertical cylindrical furnace body, a burner is provided in the center of the top of the furnace body, an air inlet is provided on the upper part of the side wall of the furnace body along the tangential direction, an air outlet is provided on the lower part of the side wall of the furnace body along the tangential direction, spiral blades are provided inside the side wall of the furnace body between the air inlet and the air outlet, and a discharge port is provided in the center of the bottom of the furnace body.

[0009] Furthermore, a fluidizer is provided around the discharge port, and the air inlet of the fluidizer is connected to the air outlet of the roasting furnace through a fluidizing fan; the pipeline between the air outlet of the roasting furnace and the smoke inlet is connected to the discharge pipeline through a smoke regulating valve.

[0010] Furthermore, the roasting return material device includes a return material conveyor, the loading end of the return material conveyor is connected to the discharge port of the roasting furnace through a high-temperature air lock valve, and the unloading end of the return material conveyor is connected to the return material inlet.

[0011] Furthermore, the return material outlet is connected to the return material inlet through a mill return material device; the mill return material device includes an external circulation belt conveyor, an external circulation bucket elevator, and a three-way valve. The feeding end of the external circulation belt conveyor is connected to the return material outlet, and the discharging end of the external circulation belt conveyor is connected to the feeding end of the external circulation bucket elevator. The discharging end of the external circulation bucket elevator is respectively connected to the waste slag buffer bin and the return material inlet through the three-way valve, and the external circulation belt conveyor is provided with an iron remover.

[0012] A method for grinding sintered limonite powder into pelletized powder and removing crystal water: sintered limonite powder is fed to a grinding disc through a feeding pipe, the sintered limonite powder is ground into powdery material by the grinding disc, small particles of the powdery material overflowing from the edge of the grinding disc are transported upward by a high-temperature airflow sent out by a nozzle ring and pass through a powder classifier, the small particles of the powdery material are divided into coarse powder that does not meet the particle size requirement and fine powder that meets the particle size requirement by the powder classifier, the fine powder is discharged from the vertical mill through the flue gas outlet, and then collected by a bag dust collector, and the coarse powder enters a dust collector. The hopper sends all or part of the coarse powder in the hopper to the roasting furnace for roasting through the coarse powder reverse conveying device to remove the crystal water in the coarse powder. A part of the coarse powder after roasting is discharged through the discharge port of the roasting furnace, and then sent to the return inlet of the vertical mill through the return device, and is put into the grinding disc again through the discharge pipe for grinding. The other part of the coarse powder after roasting is discharged through the air outlet of the roasting furnace with the high-temperature flue gas, and then enters the flue gas inlet of the nozzle ring, and then is mixed with the newly ground powdered material overflowing from the edge of the grinding disc and dried.

[0013] Furthermore, the large particles of the powdered material overflowing from the edge of the grinding disc are discharged through the return material outlet below the nozzle ring, and then sent to the return material inlet of the vertical mill through the mill return device, and then put into the grinding disc for grinding again through the discharge pipe.

[0014] Furthermore, the coarse powder is roasted at a temperature of 900-1000°C; and the temperature of the high-temperature flue gas introduced into the tuyere ring is not less than 400°C.

[0015] Compared with the existing pelletizing process, the present invention has the following advantages: 1) In the traditional vertical mill system for grinding limonite into pellet powder, the mill inlet is usually ≤300℃. Due to the low flue gas temperature and the short residence time of the material in the high temperature zone, it is difficult to remove the crystal water. The present invention can remove part or even all of the crystal water in the process of preparing pellet powder, thereby improving the iron grade of limonite pellet powder, reducing the adverse effect of the pellets on the pellets due to the release of crystal water during the pellet roasting process, and increasing the amount of limonite used in the pellets.

[0016] 2) The process of removing crystal water of the present invention has a high heat utilization rate: Usually, the sintered coarse powder of limonite is removed from the crystal water by using a rotary kiln or other methods. The temperature of the material and tail gas after roasting is usually high, and a lot of heat is taken away, resulting in low heat utilization rate. In the present invention, the material is roasted during the process of grinding the sintered powder of limonite into fine powder with very small particles, because the particles become smaller, the specific surface area is larger, the contact area with the hot roasting flue gas is large, and the heat transfer efficiency is high; The high-temperature material after roasting re-enters the mill and is mixed with the raw materials. Through solid-solid and solid-gas heat transfer, the heat carried by the high-temperature material itself is used as part of the heat source required for raw material grinding and drying, and finally the temperature of the high-temperature material is reduced to a lower temperature, saving roasting heat consumption and improving heat utilization rate. The high-temperature flue gas after roasting enters the mill and is continuously utilized as the grinding, ventilation and drying heat source of the mill, thus saving roasting heat consumption and improving heat utilization rate.

[0017] 3) Compared with independent rotary kiln roasting and independent grinding, this solution organically combines the powder making and roasting steps, saving investment and land. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the device of the present invention.

[0019] Figure 2 This is a schematic diagram of the vertical mill structure.

[0020] Figure 3 Schematic diagram of the roasting furnace structure.

[0021] Figure 4 This is a schematic diagram of the air inlet structure of the roasting furnace.

[0022] Figure 5 This is a schematic diagram of the roasting furnace air outlet structure.

[0023] In the figure: 1-vertical mill; 2-bag dust collector; 3-main exhaust fan; 4-discharge pipeline; 5-roasting furnace; 6-mixer; 7-high temperature air lock valve; 8-fluidizing fan; 9-return material conveyor; 10-smoke inlet; 11-coarse powder outlet; 12-smoke regulating valve; 13-external circulation belt conveyor; 14-external circulation bucket elevator; 15-three-way valve; 16-waste slag bin buffer; 17-iron remover; 18-grinding disc; 19-nozzle ring; 20-powder selector; 21-smoke outlet; 22-feeding hopper; 23-feeding pipe; 24-raw material inlet; 25-return material outlet; 26-return material inlet; 27-furnace body; 28-burner; 29-air inlet; 30-air outlet; 31-spiral blade; 32-discharge port; 33-fluidizer; 34-reversible conveyor; 35-buffer tank. DETAILED DESCRIPTION

[0024] The present invention will be further explained below in conjunction with the accompanying drawings.

[0025] like Figures 1 to 3As shown, a device for grinding sintered limonite into pelletized powder and removing crystal water of the present invention comprises a vertical mill 1, the vertical mill 1 comprises a grinding disc 18, a tuyere ring 19 is arranged around the grinding disc 18, the tuyere ring 19 is provided with a flue gas inlet 10, a powder selector 20 is arranged above the grinding disc 18, a flue gas outlet 21 is arranged on the upper side of the powder selector 20, the flue gas outlet 21 is connected to the air inlet of the bag dust collector 2, the air outlet of the bag dust collector 2 is connected to the exhaust pipeline 4, the exhaust pipeline 4 is provided with a main exhaust fan 3, the powder selector 20 A drop hopper 22 is arranged on the lower side, a discharge pipe 23 is arranged at the center of the drop hopper 22, a return material outlet 25 is arranged below the nozzle ring 19, and the vertical mill 1 is provided with a coarse powder outlet 11 and a return material inlet 26. The drop hopper 22 is connected to a coarse powder transfer device through the coarse powder outlet 11, the coarse powder transfer device is connected to an air inlet 29 of the roasting furnace 5, the air outlet 30 of the roasting furnace 5 is connected to a smoke inlet 10, and a discharge port 32 of the roasting furnace 5 is connected to the return material inlet 26 through the roasting return device, and the return material inlet 26 is connected to the drop pipe 23.

[0026] In the present invention, a buffer tank 35 is provided at the bottom of the drop hopper 22, a discharge port is provided on the inner side wall of the buffer tank 35, and the outer side wall of the buffer tank 35 is connected to the coarse powder outlet 11. The coarse powder that does not meet the particle size requirement selected by the powder selector is accumulated along the drop hopper to the inner buffer tank 35, and the coarse powder in the buffer tank 35 can be discharged from the vertical mill 1 through the coarse powder outlet 11, and then sent to the roasting furnace 5 through the coarse powder reverse conveying device. A regulating valve is provided at the coarse powder outlet 11 to adjust the discharge amount of the coarse powder, and the coarse powder in the buffer tank 35 can also be discharged through the discharge port and directly returned to the grinding disc for re-grinding.

[0027] When the vertical mill is working, the sintered limonite powder to be ground is sent to the discharge pipe through the raw material inlet, and is put into the grinding disc through the discharge pipe. The sintered limonite powder is ground into powdery materials by the grinding disc. The large particles of the powdery materials overflowing from the edge of the grinding disc are discharged through the return outlet below the nozzle ring, and the small particles of the powdery materials overflowing from the edge of the grinding disc are transported upward by the high-temperature airflow sent out by the nozzle ring and pass through the powder classifier. The small particles of the powdery materials are divided into coarse powder that does not meet the particle size requirements and fine powder that meets the particle size requirements by the powder classifier. The fine powder is discharged from the vertical mill through the flue gas outlet and then collected by the bag dust collector. The coarse powder is returned to the grinding disc through the drop hopper and ground again. The above process is repeated to make the particle size of the powdery material change from coarse to fine until it meets the particle size requirement set by the powder classifier. The coarse powder in the hopper is sent to the roasting furnace for roasting through the coarse powder reverse conveying device. The high-temperature flue gas generated by the roasting furnace can remove part or even all of the crystal water in the coarse powder, thereby improving the iron grade of the limonite pellet concentrate. The coarse powder after roasting can enter the return material inlet through the roasting return material device and be put into the grinding disc again through the discharge pipe for grinding. The high-temperature flue gas generated by roasting can be passed into the flue gas inlet of the nozzle ring to dry the newly ground powdered material overflowing from the edge of the grinding disc.

[0028] Furthermore, in the above process, since the interior of the discharge pipe and the discharge hopper are isolated from each other, the coarse powder after roasting will only come into contact with the newly added limonite sintered powder in the discharge pipe, and will not come into contact with the coarse powder in the discharge hopper.

[0029] In the present invention, the coarse powder transport device delivers the coarse powder into the roasting furnace by pneumatic conveying. Figure 1 As shown, the coarse powder transfer device includes a mixer 6, the feed port of the mixer 6 is connected to the coarse powder outlet 11, the air inlet of the mixer 6 is connected to the discharge pipeline of the air outlet of the main exhaust fan 3, and the discharge port of the mixer 6 is connected to the air inlet of the roasting furnace 5. The main exhaust fan 3 provides the air volume and air pressure required by the air nozzle ring 19, and the coarse powder in the drop hopper 22 passes through the mixer 6 and forms a gas-solid two-phase flow with the flue gas from the outlet of the main exhaust fan 3, and enters the air inlet of the roasting furnace 5 from the tangential direction.

[0030] The removal of crystal water from the material requires sufficient flue gas temperature and sufficient time. Figures 3 to 5 As shown, the roasting furnace 5 includes a vertical cylindrical furnace body 27, a burner 28 is provided in the center of the top of the furnace body 27, an air inlet 29 is provided on the upper part of the side wall of the furnace body 27 along the tangential direction, an air outlet 30 is provided on the lower part of the side wall of the furnace body 27 along the tangential direction, a spiral blade 31 is provided inside the side wall of the furnace body 27 between the air inlet 29 and the air outlet 30, and a discharge port 32 is provided in the center of the bottom of the furnace body 27.

[0031] The burner of the roasting furnace can generate flue gas with a sufficiently high temperature, and the furnace temperature of the roasting furnace can reach 900~1000℃. The spiral blades can be set to make the material move in a spiral line in the furnace, thereby extending the residence time of the material in the roasting furnace. Through the height and diameter of the roasting furnace and the pitch of the spiral blades, as well as the length of the pipeline between the roasting furnace and the vertical mill, the sum of the time for the material to move inside the roasting furnace and the time for the material to move with the flue gas from the roasting furnace to the mill nozzle ring is controlled to reach a certain time, thereby achieving the removal of 10%~100% of the crystal water.

[0032] In addition, the particle size of the material is the main factor affecting the dehydration time and heat and mass transfer. Reducing the particle size of the material will increase the dehydration speed of the material and shorten the dehydration time. The smaller the material particles are, the larger their specific surface area will be, the more fully they will contact with the flue gas, and the faster the heat conduction will be. In the present invention, the process of the material particle size changing from coarse to fine during the pulverizing process is utilized, and before the particle size reaches the qualified particle size, this part of the material is contacted with the high-temperature flue gas under a state of high specific surface area. Each time the material is ground, the particle diameter becomes smaller once, and generally the qualified particle size can be reached after several grindings. Each time the material particles become smaller, before re-entering the grinding disc for grinding, they are first sent to the roasting furnace for roasting once, and the contact time between the particles and the high-temperature flue gas is doubled. Due to the relationship between heat conduction and water migration, the dehydration of the particles is a process from the outside to the inside, and the surface of the particles is more easily dehydrated. If there is a part that has not been completely dehydrated inside the large particles, it will be easily exposed in the process of its particle size becoming smaller before reaching the qualified particle size, which is conducive to removing water in the subsequent roasting process.

[0033] like Figure 1 and 3 As shown, the coarse powder moves along the spiral track from the air inlet 29 at the upper part of the furnace body 27 to the air outlet 30 at the lower part of the furnace body 27 along the two-phase flow. A part of it settles at the bottom of the furnace body 27 and is sent to the roasting furnace 5 through the discharge port 32 through the roasting return device. The other part is suspended in the flue gas and is discharged from the air outlet 30 of the roasting furnace 5 along with the flue gas, and then transported to the nozzle ring 19 of the vertical mill 1 through the flue gas inlet 10. This part of the flue gas is used as a heat source and ventilation airflow to dry and transport the newly ground powdered material overflowing from the edge of the grinding disc. At the same time, the heat carried by the material temperature of this part of the roasted coarse powder material entering the vertical mill with the flue gas collides with the newly ground material inside the vertical mill, and its own heat is also transferred to the newly ground material and flue gas as part of the drying heat source.

[0034] In the present invention, a fluidizer 33 is provided around the discharge port 32, and the air inlet of the fluidizer 33 is connected to the air outlet 30 of the roasting furnace 5 through the fluidizing fan 8. The coarse powder settled at the bottom of the roasting furnace 5 is buffered in the roasting furnace, and the flue gas discharged from the roasting furnace 5 is extracted by the fluidizing fan 8 through the provided fluidizer 33, and fluidizing air is blown into the fluidizer 33, so that the material at the bottom 5 of the roasting furnace is in a fluidized state. At this time, the coarse powder is still in a temperature environment where crystal water can be removed, which is conducive to removing crystal water from the material.

[0035] like Figure 1 As shown, in order to facilitate the adjustment of the flue gas flow entering the vertical mill 1, the pipeline between the air outlet 30 of the roasting furnace 5 and the flue gas inlet 10 is connected to the exhaust pipeline 4 through the flue gas regulating valve 12, and a part of the gas in the exhaust pipeline 4 can be directly sent to the flue gas inlet 10 through the flue gas regulating valve 12.

[0036] like Figure 1 and 2 As shown, the roasting return device includes a return conveyor 9, the feeding end of the return conveyor 9 is connected to the discharge port 32 of the roasting furnace 5 through the high-temperature air lock valve 8, and the discharge end of the return conveyor 9 is connected to the return inlet 26, and the return inlet 26 is connected to the discharge pipe 23. The coarse powder is discharged from the discharge port at the bottom of the roasting furnace through the high-temperature air lock valve, and is transported to the return inlet of the mill through the roasting return conveyor, and then continues to be ground on the surface of the grinding disc together with the new limonite sintered powder raw material. The heat carried by the material temperature of this part of the coarse powder material collides with the newly ground material inside the mill, and transfers its own heat to the newly ground material and flue gas as part of the drying heat source.

[0037] like Figure 1 As shown, the return material outlet 25 is connected to the return material inlet 26 through the mill return material device. When the vertical mill is working, the large particles of the powdered material overflowing from the edge of the grinding disc are discharged through the return material outlet below the nozzle ring. This part of the material can also be sent to the return material inlet through the mill return material device, and then put back into the grinding disc for re-grinding. The mill return material device includes an external circulation belt conveyor 13, an external circulation bucket elevator 14, and a three-way valve 15. The feeding end of the external circulation belt conveyor 13 is connected to the return material outlet 25, and the discharging end of the external circulation belt conveyor 13 is connected to the feeding end of the external circulation bucket elevator 14. The discharging end of the external circulation bucket elevator 14 is respectively connected to the waste slag bin buffer 16 and the return material inlet 26 through the three-way valve 15. The external circulation belt conveyor 13 is provided with an iron remover 17.

[0038] The large particles of powdered materials overflowing from the edge of the grinding disc cannot be transported upward by the high-temperature airflow provided by the nozzle ring, and are transported downward through the return outlet, and then transported to the discharge pipe of the vertical mill through the external circulation belt conveyor, external circulation bucket elevator, and three-way valve, and then continue to grind together with the new limonite sintered powder raw materials on the surface of the grinding disc. Large iron debris (bolts, iron blocks, etc.) is removed by the iron remover set by the external circulation belt conveyor. Under different working conditions, the powdered materials discharged through the return outlet can enter the waste slag bin cache through the three-way valve. A reversible conveyor can be set under the waste slag bin cache, so that the materials in the waste slag bin cache can be returned to the mill through the external circulation bucket elevator for further grinding, or can be discharged.

[0039] The method for grinding sintered limonite powder into pelletized powder and removing crystal water of the present invention comprises the following steps: the sintered limonite powder is fed to a grinding disc through a feeding pipe, the sintered limonite powder is ground into powdery materials through the grinding disc, the small particles of the powdery materials overflowing from the edge of the grinding disc are transported upward by a high-temperature airflow sent out by a nozzle ring and pass through a powder classifier, the small particles of the powdery materials are divided into coarse powder that does not meet the particle size requirement and fine powder that meets the particle size requirement by the powder classifier, the fine powder is discharged from the vertical mill through a flue gas outlet, and then collected by a bag dust collector, the coarse powder enters a drop hopper, all or part of the coarse powder in the drop hopper is sent to a roasting furnace for roasting through a coarse powder reverse transport device, and the coarse powder roasting temperature is 900-1000 ℃ to remove the crystal water in the coarse powder. Part of the coarse powder after roasting is discharged through the discharge port of the roasting furnace, and then sent to the return material inlet of the vertical mill through the return device, and is put on the grinding disc again for grinding through the discharge pipe. Another part of the coarse powder after roasting is discharged through the air outlet of the roasting furnace with the high-temperature flue gas, and then enters the flue gas inlet of the nozzle ring. The temperature of the high-temperature flue gas entering the nozzle ring is not less than 400℃, and then it is mixed with the newly ground powdered material overflowing from the edge of the grinding disc and dried; the large particles of the powdered material overflowing from the edge of the grinding disc are discharged through the return material outlet below the nozzle ring, and then sent to the discharge pipe of the vertical mill through the mill return device, and are put on the grinding disc again for grinding.

[0040] The effect of this method For example, a kind of limonite powder produced in Indonesia, with a particle size of 0~10mm, 21% free water, 12% crystal water, has the following composition:

[0041] The pellet powder ground by the device and method of the present invention has a particle size of 20 mesh accounting for ≥80%, free water 1%, and crystal water 9.6%, which can meet the requirements for pellet production.

[0042] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A device for sintering limonite into pelletized powder and removing crystal water, comprising a vertical mill, the vertical mill comprising a grinding disc, a tuyere ring arranged around the grinding disc, a smoke inlet arranged on the tuyere ring, a powder classifier arranged above the grinding disc, a smoke outlet arranged on the upper side of the powder classifier, the smoke outlet connected to the air inlet of a bag dust collector, the air outlet of the bag dust collector connected to a discharge pipeline, a main exhaust fan arranged on the discharge pipeline, a drop hopper arranged at the lower side of the powder classifier, a drop pipe arranged at the center of the drop hopper, a return outlet arranged below the tuyere ring, characterized in that: The vertical mill is provided with a coarse powder outlet and a return material inlet. The discharge hopper is connected to the coarse powder transfer device through the coarse powder outlet, the coarse powder transfer device is connected to the air inlet of the roasting furnace, the air outlet of the roasting furnace is connected to the smoke inlet, the discharge port of the roasting furnace is connected to the return material inlet through the roasting return material device, and the return material inlet is connected to the discharge pipe.

2. According to the device for grinding sintered limonite powder into pelletized powder and removing crystal water as described in claim 1, the bottom of the drop hopper has a buffer groove, the inner wall of the buffer groove is provided with a discharge port, and the outer wall of the buffer groove is connected to the coarse powder outlet.

3. The device for grinding sintered limonite powder into pelletized powder and removing crystal water according to claim 1, characterized in that: The coarse powder transfer device comprises a mixer, the feed inlet of the mixer is connected to the coarse powder outlet, the air inlet of the mixer is connected to the discharge pipeline of the main exhaust fan outlet, and the discharge port of the mixer is connected to the air inlet of the roasting furnace.

4. The device for grinding sintered limonite powder into pelletized powder and removing crystal water according to claim 1, characterized in that: The roasting furnace comprises a vertical cylindrical furnace body, a burner is arranged in the center of the top of the furnace body, an air inlet is arranged in the tangential direction on the upper part of the side wall of the furnace body, an air outlet is arranged in the tangential direction on the lower part of the side wall of the furnace body, spiral blades are arranged inside the side wall of the furnace body between the air inlet and the air outlet, and a discharge port is arranged in the center of the bottom of the furnace body.

5. The device for grinding sintered limonite powder into pelletized powder and removing crystal water according to claim 4, characterized in that: A fluidizer is arranged around the discharge port, and the air inlet of the fluidizer is connected to the air outlet of the roasting furnace through a fluidizing fan; the pipeline between the air outlet of the roasting furnace and the smoke inlet is connected to the discharge pipeline through a smoke regulating valve.

6. The device for grinding sintered limonite powder into pelletized powder and removing crystal water according to claim 1, characterized in that: The roasting return material device comprises a return material conveyor, a loading end of the return material conveyor is connected to a discharge port of the roasting furnace through a high-temperature air lock valve, and a discharge end of the return material conveyor is connected to a return material inlet.

7. The device for grinding sintered limonite powder into pelletized powder and removing crystal water according to claim 1, characterized in that: The return material outlet is connected to the return material inlet through a mill return material device; the mill return material device includes an external circulation belt conveyor, an external circulation bucket elevator, and a three-way valve. The feeding end of the external circulation belt conveyor is connected to the return material outlet, the discharging end of the external circulation belt conveyor is connected to the feeding end of the external circulation bucket elevator, and the discharging end of the external circulation bucket elevator is respectively connected to the waste slag buffer bin and the return material inlet through the three-way valve, and the external circulation belt conveyor is provided with an iron remover.

8. A method for grinding sintered limonite powder into pelletized powder and removing crystal water according to the device of claim 1, characterized in that: The sintered limonite powder is fed to the grinding disc through a feed pipe, and the sintered limonite powder is ground into powdery materials by the grinding disc. The small particles of the powdery materials overflowing from the edge of the grinding disc are transported upward by the high-temperature airflow sent out by the nozzle ring and pass through the powder classifier. The small particles of the powdery materials are divided into coarse powder that does not meet the particle size requirements and fine powder that meets the particle size requirements by the powder classifier. The fine powder is discharged from the vertical mill through the flue gas outlet and then collected by the bag dust collector. The coarse powder enters the discharge hopper. All or part of the coarse powder in the discharge hopper is sent to the roasting furnace for roasting through the coarse powder reverse conveying device to remove the crystal water in the coarse powder. A part of the coarse powder after roasting is discharged through the discharge port of the roasting furnace, and then sent to the return inlet of the vertical mill through the return device, and then fed to the grinding disc again through the feed pipe for grinding. The other part of the coarse powder after roasting is discharged through the air outlet of the roasting furnace with the high-temperature flue gas, and then enters the flue gas inlet of the nozzle ring, and then mixed with the newly ground powdery materials overflowing from the edge of the grinding disc and dried.

9. The method for grinding sintered limonite powder into pelletized powder and removing crystal water according to claim 8, characterized in that: The large particles of powdered materials overflowing from the edge of the grinding disc are discharged through the return material outlet below the nozzle ring, and then sent to the return material inlet of the vertical mill through the mill return device, and then put into the grinding disc for grinding again through the discharge pipe.

10. The method for grinding sintered limonite powder into pelletized powder and removing crystal water according to claim 8, characterized in that: The coarse powder roasting temperature is 900~1000℃; the temperature of the high-temperature flue gas entering the nozzle ring is not less than 400℃.

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