Air duct structure of a vertical roller mill and vertical roller mill

Abstract

The application discloses a kind of air duct structure of vertical roller mill and vertical roller mill, belong to vertical roller mill equipment technical technical field, the air duct structure of vertical roller mill includes shell body and is located in the lower part of millstone of the inboard of shell body, the lower part of shell body is equipped with air inlet, the upper part of shell body is equipped with air outlet, it is characterized in that: the inside of shell body is equipped with the air inlet duct located below the millstone, the pre-sorting air duct located below the periphery of millstone, the ascending air duct located in the side of shell body, the air inlet duct is communicated with the air inlet, the pre-sorting air duct is equipped with baffle for scattering powder, the ascending air duct is communicated with the air outlet, the airflow guided into below the millstone sequentially passes through the air inlet duct, sorting air duct and ascending air duct.This vertical roller mill can realize the promotion of powder selection efficiency, the reduction of energy consumption and the extension of equipment service life.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of vertical roller mill equipment, and particularly relates to an air duct structure of a vertical roller mill and the vertical roller mill. BACKGROUND

[0002] A vertical roller mill is a widely used device in the industrial field, mainly used for efficient grinding and crushing of powder particles. Its unique feature is its vertical layout, from top to bottom, powder particles are fed, and the action of roller extrusion and friction grinds the powder particles into the required particle size. In the field of cement production, the vertical roller mill is of great significance. It is widely used in the process of coal and ore grinding, which grinds coal and ore into fine powder for subsequent sintering and mixing processes. This not only improves production efficiency, but also helps to ensure the quality consistency of cement. The use of vertical roller mills in the cement industry has made positive contributions to improving production efficiency, saving energy, reducing carbon emissions, etc. The working mode of the vertical roller mill is that the raw materials enter the vertical roller mill through the feeding device, and the powder particles move from the center to the edge of the grinding disc while being crushed and ground by the downward extrusion of the grinding roller. The crushed powder particles at the edge of the grinding disc are carried by the hot air in the air ring and are brought into the powder separator for separation. The coarse powder returned to the center of the grinding disc is mixed with new feed and undergoes secondary grinding. The qualified fine powder is collected as finished product, and part of the difficult-to-grind large particle powder cannot be carried by the hot air in the air ring and is discharged through the slag discharge port into the external circulation system.

[0003] At present, the air duct design structure of the vertical roller mill still has some problems and shortcomings, which affects the stability, powder separation efficiency and service life of the equipment, etc.

[0004] Firstly, the vertical roller mill belongs to a typical air-borne material design structure. The bottom air duct transports hot air upward, through the air ring, carrying the ground powder particles thrown out from the grinding roller and grinding disc, to the powder separator located at the upper part of the equipment for screening. However, this design structure has some problems. Due to the high flow speed of the powder particles in the air duct, the powder particles are subjected to high-speed scouring in the air duct, which causes the parts inside the air duct, such as the middle and outer shell bodies, the grinding roller horn sleeve, and the powder separator return cone, to be easily worn. This wear problem greatly reduces the service life of the equipment, and frequent replacement of damaged parts is required, increasing maintenance costs.

[0005] Secondly, the powder concentrator located at the upper part of the vertical roller mill, its powder concentration efficiency is affected by many factors. Especially for high specific surface area, ultra-fine powder particles, the powder concentration effect is not good. Therefore, the circulating load of the powder particles in the vertical roller mill is relatively large, and the circulating load is more significant. This leads to the feeding concentration of the selected powder machine to be difficult to maintain stable, often in the "high and low" working condition. The fluctuation of the feeding concentration of the powder concentrator makes the powder concentration efficiency cannot be kept in the best state for a long time, which affects the production efficiency and product quality in the cement manufacturing process. For the production of machine-made sand by the vertical roller mill, due to the existence of the grinding roller spacing, part of the unground powder particles are thrown out of the grinding disc under the action of the centrifugal force of the grinding disc, so that the powder particles circulate in the grinding system more times and consume more energy.

[0006] In summary, the problems and shortcomings caused by the air duct design structure of the vertical roller mill mainly include aggravation of component wear and fluctuation of powder concentration efficiency. These problems not only increase the maintenance cost of the equipment, but also affect the stability of production efficiency and product quality, which need to be solved and improved in design and operation. SUMMARY

[0007] In view of the problems existing in the prior art, the present application provides an air duct structure of a vertical roller mill and a vertical roller mill for solving the problems of severe component wear, fluctuation of powder concentration efficiency, poor stability of production efficiency and product quality of the existing vertical roller mill.

[0008] The present application is implemented as follows: an air duct structure of a vertical roller mill, characterized in that it comprises an outer shell and a grinding disc arranged at the lower part of the inner side of the outer shell, the lower part of the outer shell is provided with an air inlet, and the upper part of the outer shell is provided with an air outlet, characterized in that: the inner part of the outer shell is provided with an air inlet duct located below the grinding disc, a pre-selection air duct located below the periphery of the grinding disc, and an upward air duct located at the side of the outer shell, the air inlet duct is communicated with the air inlet, the pre-selection air duct is provided with a baffle for scattering the powder, the upward air duct is communicated with the air outlet, and the airflow introduced below the grinding disc passes through the air inlet duct, the pre-selection air duct and the upward air duct in sequence.

[0009] Advantages and effects:

[0010] The air duct structure of the vertical roller mill provided by the present application comprises a pre-selection air duct, which provides key support for the efficient operation of the entire grinding system. In this air duct design, the pre-selection air duct surrounds the grinding disc, and the semi-finished and finished powder particles thrown out of the grinding disc fall into the upper port of the pre-selection air duct. In this air duct, the powder particles fall from top to bottom under the action of gravity, are scattered by the baffle, and the hot airflow plays a drying role. This process realizes the preliminary screening and drying of the powder particles through the design of the pre-selection air duct, which creates more favorable conditions for the subsequent processing steps.

[0011] By the preliminary separation of coarse particle powder particles, the pre-selection air duct enables these particles to be discharged at the bottom of the air duct, thereby effectively reducing the energy consumption in the system and further enhancing the overall work efficiency. In particular for high specific surface area, ultra-fine powder particles, the setting of the pre-selection air duct is more important. Secondly, due to factors such as mill disc spacing, part of the powder particles may not be fully ground during the grinding process and be thrown out by the mill disc centrifugal force. The introduction of the pre-selection air duct enables these unground particles to be captured and separated, effectively reducing the number of cycles of the powder particles in the grinding system and reducing the consumption of energy consumption.

[0012] In addition, the innovative design of the air duct structure in the technical solution makes the connection between the pre-selection air duct and the ascending air duct into a cavity. This annular cavity design allows dust-laden air to be transported therein, thereby reducing the degree of wind scouring of the internal components of the vertical roller mill. This not only helps to prolong the service life of the equipment, but also reduces the amount of maintenance during long-term operation, further improving the reliability and stability of the equipment.

[0013] In summary, the pre-selection air duct in the air duct structure of the vertical roller mill provides multiple advantages for the efficient operation of the grinding system. Through preliminary separation, drying, and particle size sand product discharge, it achieves the improvement of the powder selection efficiency, the reduction of energy consumption, and the extension of the service life of the equipment. This design not only has significant application value in the field of cement manufacturing, but also provides a useful reference for powder grinding processes in other fields.

[0014] In the above technical solution, preferably, including annular inner partition plate, annular outer partition plate and inner shell, the annular inner partition plate is spaced below the outer edge of the mill disc, the outer ring part of the annular inner partition plate forms a positive step structure downward from the outer edge of the mill disc, and the annular inner partition plates form the air inlet duct in a ring shape; the annular outer partition plate is spaced at the lower part of the inner side of the outer shell, the annular outer partition plate forms a peripheral inverted step structure arranged around the positive step structure, and the annular outer partition plate and the annular inner partition plate form the pre-selection air duct; the inner shell is arranged inside the outer shell, and the inner shell and the outer shell form the ascending air duct. The annular inner partition plate in the pre-selection air duct forms a positive step structure and rotates with the mill disc. The structural design of the annular inner partition plate not only has a dispersing and screening effect on the powder particles entering the pre-selection air duct, but also has the functions of air supply and flow field optimization. That is, the annular inner partition plate of the air inlet duct is arranged as several air chambers, and rotates with the mill disc. Hot air is introduced from the bottom end of the air duct, and the circumferential rotation of the air baffle plate uniformly distributes the air volume introduced into each air chamber, avoiding the short-circuiting of air.

[0015] In the technical scheme, preferably, the lower part of the grinding disc is installed with the annular inner baffle through a rib frame, the annular inner baffle is coaxial with the grinding disc and is driven to rotate by the grinding disc.

[0016] In the technical scheme, preferably, the annular inner baffles and the annular outer baffles are alternately and spacedly arranged from the upper opening to the lower opening of the pre-sorting air duct.

[0017] In the technical scheme, preferably, the annular outer baffle at the top is connected to the inner shell, and the annular outer baffle at the bottom is connected to the outer shell.

[0018] In the technical scheme, preferably, a spiral baffle is arranged between the outer shell and the inner shell, and the spiral baffle forms a spiral-shaped ascending air duct around the center line of the outer shell. The spiral-shaped ascending air duct can not only optimize the flow field distribution and reduce local vortex for the gas rising from top to bottom, but also can play a role in local settlement.

[0019] In the technical scheme, preferably, the included angle between the annular inner baffle and the upper plate surface of the annular outer baffle is 90°.

[0020] In the technical scheme, preferably, the included angle between the upper plate surface of the annular outer baffle and the horizontal plane is A3, and 40°<A3<80°.

[0021] In the technical scheme, preferably, the width of the annular inner baffle is L3, the width of the annular outer baffle is L4, and 3 / 2<L3 / L4<3 / 1.

[0022] Another object of the present application is to provide a vertical roller mill provided with the air duct structure. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structural schematic diagram of embodiment one in the present application;

[0024] Figure 2 is a front view of embodiment one in the present application;

[0025] Figure 3 is a mounting structure schematic diagram of the annular inner baffle and the annular outer baffle in the present application;

[0026] Figure 4 is a structural schematic diagram of the ascending air duct in the present application;

[0027] Figure 5 is a positional relationship schematic diagram of the air inlet duct, the pre-sorting air duct and the ascending air duct in the present application;

[0028] Figure 6 is a schematic diagram of the position geometry of the annular inner baffle and the annular outer baffle in the present application;

[0029] Figure 7 is a structural schematic diagram of Example Two in the present application;

[0030] Figure 8 is a front cross-sectional view of Example Two in the present application;

[0031] Figure 9 is a structural schematic diagram of Example Three in the present application;

[0032] Figure 10 is a structural schematic diagram of Example Four in the present application;

[0033] Figure 11 is a structural schematic diagram of Example Five in the present application;

[0034] Figure 12 is a structural schematic diagram of Example Six in the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0036] To solve the problems of severe wear of components, fluctuation of powder selection efficiency, poor production efficiency and product quality stability of the current vertical roller mill, the present application provides a vertical roller mill air duct structure and a vertical roller mill. The vertical roller mill air duct structure can improve the powder selection efficiency of the vertical roller mill, reduce energy consumption and prolong the service life of the equipment. In order to further illustrate the structure of the present application, the detailed description is as follows in combination with the drawings:

[0037] Example One

[0038] Please refer to Figure 1 and Figure 2 , a vertical roller mill, the vertical roller mill includes a shell and a grinding disc 1 arranged at the lower part of the inner side of the shell. The lower part of the shell is provided with an air inlet 2, and the upper part of the shell is provided with an air outlet 3. As known by those skilled in the art, the grinding disc of the vertical roller mill is a key grinding element, which is usually composed of a horizontal disc. The pressure applied to the grinding disc by the rotating grinding roller grinds the raw material into the required fineness.

[0039] The inner part of the outer shell is provided with an air inlet channel 4 below the grinding disc, a pre-sorting air channel 5 below the periphery of the grinding disc, and an ascending air channel 6 at the side of the outer shell. The air inlet channel is connected to an air inlet. The pre-sorting air channel is provided with a baffle for dispersing the powder. The hot air introduced below the grinding disc passes through the air inlet channel, the pre-sorting air channel, and the ascending air channel in sequence.

[0040] In this embodiment, specifically, the baffle includes an annular inner baffle 7 and an annular outer baffle 8, and the shell includes an outer shell 9 and an inner shell 10. The annular inner baffles are arranged at intervals below the outer edge of the grinding disc, and the outer ring part of the annular inner baffle forms a positive step structure downward from the outer edge of the grinding disc. The annular inner baffles form a ring-shaped air inlet channel therebetween. The air inlet channel of the vertical roller mill is circular or polygonal, is arranged around the circumference of the grinding disc, and is composed of the cavity between the positive step structure formed by the grinding disc and the radially outer part of the annular inner baffle. The bottom end of the air inlet channel is flush with the bottom of the grinding disc. The bottom of the grinding disc is connected to a plurality of circumferentially and evenly arranged rib frames 11, which are baffle plates and rotate with the grinding disc, thereby dividing the air inlet channel into a plurality of air inlet chambers. The air inlet is tangentially arranged in a volute shape or is arranged vertically to the bottom of the air inlet.

[0041] The annular outer baffles are arranged at intervals at the inner side of the lower part of the inner shell, and the annular outer baffles form a reverse step structure around the periphery of the positive step structure. The pre-sorting air channel is formed between the annular outer baffles and the annular inner baffles.

[0042] Please refer to Figure 3 In this embodiment, the pre-sorting air channel is annularly distributed along the grinding disc and is flush with the outer edge of the upper end of the grinding disc. The top annular inner baffle of the positive step structure at the inner side of the pre-sorting air channel is connected to the outer edge of the grinding disc. The top annular outer baffle of the reverse step structure of the pre-sorting air channel is connected to the inner shell at the upper end, and the lower annular outer baffle is connected to the outer shell. The two annular outer baffles are located outside the inlet of the ascending air channel, and the annular outer baffles at both ends form the inlet of the ascending air channel. Further, the annular outer baffle at the top is connected to the inner shell, and the annular outer baffle at the bottom is connected to the outer shell. The lower part of the grinding disc is installed with the annular inner baffles through the rib frames. The annular inner baffles are coaxial with the grinding disc and are driven to rotate by the grinding disc. The annular inner baffles and the annular outer baffles are alternately and intervaliy arranged from the upper opening to the lower opening of the pre-sorting air channel.

[0043] The pre-sorting air channel is composed of two groups of circular or polygonal conical rings arranged at a certain distance from each other, overlapping each other, and concentrically with each other, i.e., a step sieve group at the radially outer part and an air guide group at the radially inner part. The sieve zone is formed between the ring groups at the radially outer part and the radially inner part, and the upper end of the sieve zone has a larger diameter than the lower end.

[0044] Please refer to Figure 5, the powder particles after grinding are thrown out of the grinding disc and fall on the uppermost annular inner baffle in a positive ladder step, and then fall on the annular outer baffle on the opposite side due to gravity, and the powder particles fall alternately on the annular inner baffle and the annular outer baffle in a Z shape. The hot gas flow from the air inlet passes through the gap between the annular inner baffles, and the powder particles are pre-separated and dried by the hot gas flow during the falling process. The pre-separated light powder particles will pass through the annular outer baffle and enter the rising air duct with the gas flow, and the coarse powder with a larger mass will fall to the next layer of baffle and be fully dispersed and air separated during each falling and impacting process. After passing through all the baffles, the powder material falling from the pre-separation air duct at the lower end port enters the vertical roller mill and is discharged from the discharge port. The fine powder carried by the gas flow from the annular outer baffle into the rising air duct will be subjected to secondary separation at the air outlet.

[0045] Please refer to Figure 5 、 Figure 6 , the specific parameters in the pre-separation air duct of the embodiment are as follows:

[0046] (1) For the separated material entering the pre-separation air duct, the feeding concentration Cs is 2.6-5.0 kg / m 3 .

[0047] (2) The annular outer baffles are multiple, and the length, angle, and spacing between the radial outer ring portions of each annular outer baffle in the annular outer baffles forming a reverse ladder structure are the same. The number of annular inner baffles is the same as that of annular outer baffles, and the length, angle, and spacing between the radial outer ring portions of each annular inner baffle in the annular inner baffles forming a positive ladder structure are the same.

[0048] (3) The baffles are arranged as shown in Figure 6 . The included angle A2 between the upper plate surface of the annular inner baffle and the annular outer baffle is 90°; the included angle A3 between the upper plate surface of the annular outer baffle and the horizontal plane is 40°<A3<80°.

[0049] (4) The width of the annular inner baffle is L3, and the width of the annular outer baffle is L4, 3 / 2<L3 / L4<3 / 1.

[0050] (5) The number of annular inner baffles is the same as that of annular outer baffles, both being N.

[0051] (6) The structure of the annular inner baffle and the annular outer baffle exists under the premise of the central air inlet structure, thereby forming a flow field structure that is beneficial to the separation of coarse particles.

[0052] (7) The vertical distance between the lower edge of the annular inner baffle and the upper plate surface of the adjacent annular outer baffle located below is D1, and the vertical distance between the lower edge of the annular outer baffle and the upper plate surface of the adjacent annular inner baffle located below is D2, then 1.5 / 1<D1 / D2<2 / 1.

[0053] Please refer to Figure 4 , the inner shell is arranged inside the outer shell, and the inner shell and the outer shell form an upward air duct. A spiral partition 12 is arranged between the outer shell and the inner shell, and the spiral partition forms a spiral upward air duct around the center line of the outer shell. The upward air duct between the pre-sorting air duct and the air outlet of the vertical roller mill is arranged as a cavity, and the air material can be transported as the upward air duct in the cavity. Not only can it reduce the long-term erosion of the internal components of the vertical roller mill by the wind, prolong the service life, and reduce the amount of maintenance. Moreover, the cavity is arranged in a spiral shape, which not only optimizes the flow field distribution and reduces local vortex for the gas rising from top to bottom, but also plays a role in local sedimentation.

[0054] Example Two

[0055] This embodiment provides a superfine product grinding equipment. Please refer to Figure 7 and Figure 8 , on the basis of the vertical roller mill provided in Example One, a dynamic powder classifier 13 can be arranged between the grinding part of the vertical roller mill and the air outlet, and the air outlet of the dynamic powder classifier is the air outlet of the vertical roller mill. The dynamic powder classifier at the upper part of the vertical roller mill is a sorting rotating cage mechanism, and the sorting rotating cage is the main component. Its working principle is to send the ground raw materials into the rotating sorting rotating cage. During the rotation of the sorting rotating cage, due to the action of centrifugal force, finer particles will be pushed to the inner periphery of the sorting rotating cage, and coarser particles will be attracted to the outside. Finer particles are guided out of the air outlet at the upper part of the outer shell under the action of airflow, while coarser particles fall to the grinding disc for regrinding.

[0056] The air inlet of the dynamic powder classifier is composed of an inner shell and an outer shell constituting the upward air duct. The upper end of the inner shell is connected to the bottom of the air inlet of the dynamic powder classifier, and the upper end of the outer shell is connected to the upper end of the air inlet of the dynamic powder classifier. In this embodiment, by adding the dynamic powder classifier, the vertical roller mill can perform multi-stage sorting, improve the sorting efficiency, and reduce the system circulating load.

[0057] Example Three

[0058] Please refer to Figure 9A superfine product grinding production process system. Fresh powder particles are fed into the vertical roller mill through the raw material buffer bin 16, and a small amount of coarse powder particles fed into the vertical roller mill through the elevator 15 can also be mixed. The air outlet of the vertical roller mill is connected to the dust collection device 17. Through the dust collection device, superfine powder particles are collected as finished products. The circulating fan 18 is connected to the air outlet of the dust collection device. The hot air from the circulating fan is divided into two paths. One path of hot air enters the vertical roller mill 14 as circulating air for recycling. The other path of hot air is directly discharged to the chimney 19. This system improves the separation efficiency and accuracy through multi-stage gradient separation, realizes product particle size control, reduces system circulating load, reduces system energy consumption, reduces workshop height, and saves investment cost.

[0059] Example Four

[0060] Please refer to Figure 10 A machine-made sand production process system using the vertical roller mill of Example One for machine-made sand production. It includes a raw material buffer bin 16, a vertical roller mill 14 of Example One, a powder separator 20, a vibrating screen 25, and a powder removal mechanism 22. The powder removal mechanism includes a cyclone 21 and a circulating fan 18. The outlet of the raw material bin is connected to the powder particle inlet of the vertical roller mill for machine-made sand. The bottom discharge port of the vertical roller mill is connected to the vibrating screen 25. The vibrating screen returns the powder particles on the screen to the vertical roller mill through the elevator 15. The air outlet of the vertical roller mill is connected to the inlet of the powder separator. The air outlet of the powder separator is connected to the cyclone. The air outlet of the cyclone is connected to the circulating fan.

[0061] The powder particles are crushed and ground by the vertical roller mill 14, and then enter the vibrating screen, powder separator, and other separation equipment to realize efficient, low-energy, and clean production of machine-made sand.

[0062] This embodiment also has a flow stabilizing bin that ensures the stability of the powder particles entering the mill, improves the crushing and grinding efficiency of the vertical mill, reduces system yield fluctuations, ensures stable operation of the system, improves energy utilization, reduces production energy consumption, improves equipment operation safety, and reduces operation failure rate.

[0063] The raw material enters the vertical roller mill from the raw material bin through the conveying belt. The powder particles after grinding and pre-separation are separated. The coarse particles move downward under the action of gravity. The powder particles after powder removal enter the vibrating screen. The vibrating screen is provided with screen holes of a certain size. The particles meeting the size requirements pass through the vibrating screen to form the finished product, i.e. the finished sand. The vibrating screen of the present example can be provided with screen holes of different sizes according to different requirements, for example, the screen hole diameter is 2.36 mm or 1.18 mm. Accordingly, the particles smaller than 2.36 mm or 1.18 mm are used as the finished sand. The particles larger than the vibrating screen hole size that do not meet the requirements are returned to the vertical roller mill for grinding and the next cycle. The fine powder smaller than 0.075 mm or 1.18 mm from the air outlet of the vertical roller mill moves upward under the action of gas. The gas carrying the fine powder enters the cyclone from the powder separator. The coarse material at the bottom of the powder separator, i.e. 0.075-1.18 mm, can be used as a machine-made sand product. The cyclone separates the fine powder and the gas. The fine powder enters the next process. The gas enters the circulating fan. Part of the gas after the circulating fan returns to the vertical roller mill. Part of the gas is discharged to the atmosphere through the chimney 19 to complete the powder removal. The above embodiment is suitable for a process system in which the moisture content of the powder particles is less than 2.5%.

[0064] The powder particles after grinding and pre-separation move downward under the action of gravity, are discharged from the bottom discharge port of the pre-separation part, enter the vibrating screen, and are screened through the vibrating screen to obtain a mixed machine-made sand product smaller than a certain particle size. At the same time, the fine powder from the air outlet of the vertical roller mill is carried upward by the airflow. Under the action of the powder separator, the harmful fine powder is separated and enters the next process.

[0065] The technology replaces the original cone crusher, double-rotor sand making machine and vertical shaft impact crusher, reduces the content of needle-shaped particles in the product, reduces the fine powder content of the machine-made sand, improves the product quality of the machine-made sand, improves the energy utilization rate of the sand making, reduces the production energy consumption, is beneficial to large-scale production, improves the resource utilization rate, improves the performance of the concrete, and improves the engineering quality.

[0066] Example Five

[0067] Please refer to Figure 11 Unlike example four, the outlet of the circulating fan of the present example is further provided with a dust collector 24 and a tail exhaust fan 23.

[0068] Part of the gas after the circulating fan 18 enters the dust collector. After dust removal by the dust collector, the gas is discharged to the atmosphere through the tail exhaust fan and the chimney 19. The double-fan system composed of the circulating fan 18 and the tail exhaust fan increases the dust collection effect on site. The dust collector can reduce the dust emission concentration to 5 mg / m 3The following realizes ultra-clean emission, which is beneficial to environmental protection. Meanwhile, the setting of the tail exhaust fan is beneficial to the adjustment of the circulating air volume. Especially when the moisture of the ground material is greater than 2.5%, the finished product has a high requirement on the moisture content (for example, the dry mortar uses machine-made sand with a moisture content less than 0.5%), the wet air can be discharged to reduce the condensation of the wet air in the system and improve the service life of the pipeline. The hot air can also be connected in series before the separation, so that the ground material particles after the vertical mill grinding can be dried to avoid the influence of water vapor condensation on the entire circulating system.

[0069] Embodiment six

[0070] Different from embodiment four, referring to Figure 12 The vibration screen 25 of the embodiment is provided with a plurality of layers of screen meshes with different aperture diameters. The screen meshes are arranged in one layer or multiple layers, and can be gradually screened to realize the demand of multiple products.

[0071] The vibration screen of the embodiment is provided with two layers of screen meshes. The upper layer of the vibration screen has a mesh aperture diameter of 4.75 mm, and the lower layer of the screen mesh has a mesh aperture diameter of 2.36 mm. The particles with a size greater than 4.75 mm above the upper layer of the screen mesh are returned to the roller mill for grinding again. The particles with a size between 2.36 mm and 4.75 mm are used as coarse sand products. The products with a size less than 2.36 mm are used as medium sand and fine sand products. The technical advantage of the embodiment is that different particle grade machine-made sand products can be produced, the production efficiency is improved, and the operation cost of the enterprise is reduced.

[0072] The above only describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. An air duct structure of a vertical roller mill, characterized by, The vertical roller mill comprises an outer shell and a grinding disc arranged at the lower part of the inner side of the outer shell, the lower part of the outer shell is provided with an air inlet, and the upper part of the outer shell is provided with an air outlet, characterized in that: the inner part of the outer shell is provided with an air inlet channel located below the grinding disc, a pre-sorting air channel located below the periphery of the grinding disc, and an upward air channel located at the side of the outer shell, the air inlet channel is communicated with the air inlet, the pre-sorting air channel is provided with a baffle for scattering powder, and the upward air channel is communicated with the air outlet, and the air flow introduced below the grinding disc passes through the air inlet channel, the pre-sorting air channel and the upward air channel in sequence. Further comprising: annular inner baffles, which are arranged at intervals below the outer edge of the grinding disc, the outer ring part of the annular inner baffles is formed as a positive step structure downward from the outer edge of the grinding disc, and the annular inner baffles form the annular air inlet channel therebetween; annular outer baffles, which are arranged at intervals at the lower part of the inner side of the outer shell, the annular outer baffles form a reverse step structure around the periphery of the positive step structure, and the annular outer baffles and the annular inner baffles form the pre-sorting air channel therebetween; an inner shell, which is arranged at the inner side of the outer shell, and the upward air channel is formed between the inner shell and the outer shell; the lower part of the grinding disc is provided with the annular inner baffles mounted by a rib frame, the annular inner baffles are coaxial with the grinding disc and are driven to rotate by the grinding disc.

2. The air duct structure of the vertical roller mill according to claim 1, characterized in that: The annular inner baffles and the annular outer baffles are alternately arranged at intervals from the upper opening to the lower opening of the pre-sorting air channel.

3. The air duct structure of the vertical roller mill according to claim 2, characterized in that: The annular outer baffles at the top are connected to the inner shell, and the annular outer baffles at the bottom are connected to the outer shell.

4. The air duct structure of the vertical roller mill according to claim 3, characterized in that: A spiral baffle is arranged between the outer shell and the inner shell, so that the upward air channel is formed between the outer shell and the inner shell in a spiral shape around the center line of the outer shell.

5. The air duct structure of the vertical roller mill according to claim 4, characterized in that: The included angle between the upper plate surface of the annular inner baffle and the annular outer baffle is 90°.

6. The air duct structure of the vertical roller mill according to claim 4, characterized in that: The included angle between the upper plate surface of the annular outer baffle and the horizontal plane is A3, and 40°<A3<80°.

7. The air duct structure of the vertical roller mill according to claim 6, characterized in that: The width of the annular inner baffle is L3, and the width of the annular outer baffle is L4, and 3 / 2 8. A vertical roller mill characterized by: The vertical roller mill is provided with the air channel structure according to any one of claims 1-7.

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