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

Abstract

Provided are an air duct structure of a vertical roller mill, and a vertical roller mill. The air duct structure of the vertical roller mill comprises an outer housing (9) and a grinding disc (1) provided on the lower portion of the inner side of the outer housing; air inlets (2) are formed in the lower portion of the outer housing; an air outlet (3) is formed in the upper portion of the outer housing; an air inlet duct (4) located below the grinding disc, a pre-sorting air duct (5) located below the outer periphery of the grinding disc, and an ascending air duct (6) located on the side portion of the outer housing are provided inside the outer housing; the air inlet duct is communicated with the air inlets; partition plates configured to disperse powder are provided in the pre-sorting air duct; the ascending air duct is communicated with the air outlet; and airflow introduced from the position below the grinding disc sequentially passes through the air inlet duct, the sorting air duct and the ascending air duct. The present vertical roller mill can improve the efficiency of powder selection, reduce energy consumption and prolong the device service life.

Description

A vertical roller mill air duct structure and vertical roller mill Technical Field

[0001] The invention belongs to the technical field of vertical roller mill equipment, and in particular relates to an air duct structure of a vertical roller mill and the vertical roller mill. Background Art

[0002] The vertical roller mill is a widely used device in industry, primarily designed for efficient grinding and comminution of powder particles. Its unique vertical layout allows for a top-down process of feeding powder particles, followed by compression and friction from the rollers, to reduce the particles to the desired size. Vertical roller mills are crucial in cement production. They are widely used in coal and ore grinding processes, reducing coal and ore to a fine powder for subsequent sintering and blending steps. This not only improves production efficiency but also helps ensure consistent cement quality. The use of vertical roller mills in the cement industry has contributed significantly to improving production efficiency, saving energy, and reducing carbon emissions. The working method 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 as the grinding disc rotates, and are crushed and ground by the downward squeezing of the grinding roller. The crushed powder particles are picked up by the hot air entering the air ring at the edge of the grinding disc and brought into the powder classifier for sorting. The coarse powder after sorting returns to the discharge cone in the center of the grinding disc, mixed with the new feed, and undergoes secondary grinding. The qualified fine powder enters the collecting device as the finished product for collection. Some large particles of powder that are difficult to grind cannot be picked up by the hot air at the air ring and enter the external circulation system through the slag discharge port.

[0003] At present, there are still some problems and shortcomings in the air duct design structure of the vertical roller mill, which affect the stability, powder selection efficiency and service life of the equipment.

[0004] First, the vertical roller mill features a typical air-carrying design. The bottom air duct conveys hot air upward, passing through the air ring and carrying the ground powder particles ejected from the grinding rollers and grinding discs to the classifier located at the top of the equipment for screening. However, this design presents several challenges. Due to the high velocity of the powder particles in the air duct, they are subjected to high-speed erosion, causing wear and tear on internal components such as the outer casing, the roller bell sleeve, and the outer surface of the classifier's return cone. This wear and tear significantly reduces the equipment's service life, necessitating frequent replacement of damaged components and increasing maintenance costs.

[0005] Secondly, the classifier located above the vertical roller mill has a variety of factors that affect its efficiency. This is particularly true for high-surface-area, ultrafine powders. Consequently, the circulating load on the powder particles within the vertical roller mill is relatively high and significant. This makes it difficult to maintain a stable feed concentration to the classifier, often experiencing fluctuating conditions. This fluctuation in feed concentration to the classifier prevents optimal classifying efficiency over time, impacting production efficiency and product quality in the cement manufacturing process. In the production of manufactured sand using a vertical roller mill, the gap between the grinding rollers allows some unground powder particles to be thrown off the grinding discs due to the centrifugal force. This results in frequent circulation of the powder particles through the grinding system, resulting in increased energy consumption.

[0006] In summary, the problems and shortcomings of vertical roller mills caused by their air duct design primarily include increased component wear and fluctuating separation efficiency. These issues not only increase equipment maintenance costs but also affect production efficiency and product quality stability, requiring resolution and improvement in design and operation.

[0007] Summary of the Invention

[0008] In response to the problems existing in the prior art, the present invention provides an air duct structure of a vertical roller mill and a vertical roller mill that solve the problems of severe component wear, fluctuation in powder selection efficiency, and poor stability in production efficiency and product quality existing in the current vertical roller mill.

[0009] The present invention is implemented as follows: an air duct structure of a vertical roller mill, characterized in that it includes an outer shell and a grinding disc arranged at the lower inner part 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 interior of the outer shell is provided with an air inlet located below the grinding disc, a pre-sorting air duct located below the periphery of the grinding disc, and an ascending air duct located on the side of the outer shell, the air inlet is connected to the air inlet, a partition for breaking up the powder is provided in the pre-sorting air duct, the ascending air duct is connected to the air outlet, and the airflow introduced from below the grinding disc passes through the air inlet, the sorting air duct and the ascending air duct in sequence.

[0010] Advantages and effects:

[0011] The air duct structure of the vertical roller mill proposed in this invention includes a pre-sorting duct, providing critical support for the efficient operation of the entire grinding system. In this duct design, the grinding disc is surrounded by a pre-sorting duct, into the upper port of which the semi-finished and finished powder particles ejected by the grinding disc fall. Within this duct, the powder particles are dispersed downward under the influence of gravity, simultaneously broken up by partitions and dried by the hot air flow. This process, through the design of the pre-sorting duct, achieves preliminary screening and drying of the powder particles, creating more favorable conditions for subsequent processing steps.

[0012] By initially separating coarse powder particles, the pre-sorting air duct allows these particles to be discharged at the bottom of the duct, effectively reducing energy consumption in the system and further enhancing overall efficiency. The provision of a pre-sorting air duct is particularly important for powder particles with high specific surface area and ultra-fine separation. Secondly, due to factors such as the spacing between the grinding discs, some powder particles may not be completely ground during the grinding process and are ejected by the centrifugal force of the grinding discs. The introduction of the pre-sorting air duct allows these unground particles to be captured and separated, effectively reducing the number of times the powder particles circulate in the grinding system and reducing energy consumption.

[0013] Furthermore, the innovative air duct design in this technical solution connects the pre-separation duct and the ascending air duct into a single cavity. This annular cavity design allows dust-laden air to be transported within it, thereby reducing the impact of wind on the internal components of the vertical roller mill. This not only helps extend the life of the equipment but also reduces maintenance during long-term operation, further improving its reliability and stability.

[0014] In summary, the pre-classification air duct design within the vertical roller mill's air duct structure offers multiple advantages for efficient grinding system operation. By performing initial separation, drying, and extracting graded sand products, it improves separation efficiency, reduces energy consumption, and extends equipment life. This design not only has significant application value in cement manufacturing but also provides valuable insights for grinding processes in other fields.

[0015] In the above technical solution, preferably, it includes an annular inner baffle, an annular outer baffle and an inner shell, wherein the annular inner baffle is spaced apart below the outer edge of the grinding disc, and the outer ring portion of the annular inner baffle forms a positive step structure downward from the outer edge of the grinding disc, and the annular inner baffles form the annular air inlet duct; the annular outer baffle is spaced apart at the lower inner side of the outer shell, and the annular outer baffle forms an outer inverted step structure surrounding the positive step structure, and the pre-sorting air duct is formed between the annular outer baffle and the annular inner baffle; the inner shell is arranged inside the outer shell, and the rising air duct is formed between the inner shell and the outer shell. The annular inner baffle in the pre-sorting air duct forms a positive step structure and rotates with the grinding disc. The structural design of the annular inner baffle can not only break up and screen the powder particles entering the pre-sorting air duct, but also play a role in air supply and flow field optimization. That is, the air inlet duct is divided into several air chambers by an annular inner partition, and rotates with the grinding disc. Hot air is introduced from the bottom of the air duct. The circular rotation of the air partition makes the air volume introduced into each air chamber evenly distributed, avoiding the occurrence of wind short circuit.

[0016] In the above technical solution, preferably, the annular inner baffle is installed on the lower part of the grinding disc through a rib frame, and the annular inner baffle is coaxial with the grinding disc and is driven to rotate by the grinding disc.

[0017] In the above technical solution, preferably, the annular inner baffles and the annular outer baffles are alternately arranged in a direction from the upper opening to the lower opening of the sorting air duct.

[0018] In the above technical solution, preferably, the annular outer baffle located at the top is connected to the inner shell, and the annular outer baffle located at the bottom is connected to the outer shell.

[0019] In the above technical solution, preferably, a spiral baffle is provided between the outer shell and the inner shell, forming a spiral upward air duct between the outer shell and the inner shell, surrounding the centerline of the outer shell. This spiral upward air duct not only optimizes the flow field distribution and reduces local eddies for gas rising from top to bottom, but also provides a localized sedimentation effect.

[0020] In the above technical solution, preferably, the angle between the upper plate surface of the annular inner baffle and the upper plate surface of the annular outer baffle is 90°.

[0021] In the above technical solution, preferably, the angle between the upper plate surface of the annular outer partition and the horizontal plane is A3, 40° <A3<80°。

[0022] In the above technical solution, preferably, the width of the annular inner partition is L3, the width of the annular outer partition is L4, 3 / 2 <L3 / L4<3 / 1。

[0023] Another object of the present invention is to provide a vertical roller mill, wherein the vertical roller mill is provided with the above-mentioned air duct structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a schematic structural diagram of Example 1 of the present application;

[0025] FIG2 is a front cross-sectional view of Example 1 of the present application;

[0026] FIG3 is a schematic diagram of the installation structure of the annular inner partition and the annular outer partition in the present application;

[0027] FIG4 is a schematic structural diagram of the rising air duct in this application;

[0028] FIG5 is a schematic diagram showing the positional relationship among the air inlet duct, the sorting air duct and the rising air duct in the present application;

[0029] FIG6 is a schematic diagram of the positional geometric parameters of the annular inner baffle and the annular outer baffle in the present application;

[0030] FIG7 is a schematic structural diagram of Example 2 of the present application;

[0031] FIG8 is a front cross-sectional view of Example 2 of the present application;

[0032] FIG9 is a schematic structural diagram of Example 3 of the present application;

[0033] FIG10 is a schematic structural diagram of Example 4 of the present application;

[0034] FIG11 is a schematic structural diagram of Example 5 of the present application;

[0035] FIG12 is a schematic structural diagram of Example 6 in this application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] To address the current issues of severe component wear, fluctuating powder selection efficiency, and poor stability in production efficiency and product quality in vertical roller mills, the present invention provides an air duct structure for a vertical roller mill and a vertical roller mill. This air duct structure can improve the powder selection efficiency of the vertical roller mill, reduce energy consumption, and extend the service life of the equipment. To further illustrate the structure of the present invention, a detailed description is provided below with reference to the accompanying drawings:

[0038] Example 1

[0039] Refer to Figures 1 and 2 , which illustrate a vertical roller mill. The mill comprises an outer shell and a grinding disc 1 located at the lower inner portion of the outer shell. An air inlet 2 is located at the lower portion of the shell, and an air outlet 3 is located at the upper portion of the outer shell. As is known to those skilled in the art, the grinding disc in a vertical roller mill is a key grinding element and typically consists of a horizontal circular disc. The pressure exerted on the grinding disc by the rotating grinding rollers grinds the raw material to the desired fineness.

[0040] Inside the outer shell are an air inlet duct 4 located below the grinding disc, a pre-classification duct 5 located below the outer periphery of the grinding disc, and an updraft duct 6 located on the side of the outer shell. The air inlet duct connects to the air inlet. The pre-classification duct is equipped with a baffle to disperse the powder. The hot air flow introduced below the grinding disc passes through the air inlet duct, the classifying duct, and the updraft duct in sequence.

[0041] In this embodiment, specifically, the partition includes an annular inner partition 7 and an annular outer partition 8, and the shell includes an outer shell 9 and an inner shell 10. The annular inner partition is spaced below the outer edge of the grinding disc, and the outer ring portion of the annular inner partition forms a positive step structure downward from the outer edge of the grinding disc, and an annular air inlet is formed between the annular inner partitions. The air inlet of the vertical roller mill is circular or polygonal, arranged around the circumference of the grinding disc, and consists of a cavity between the positive step structure formed by the grinding disc and the radial outer portion of the annular inner partition. The bottom end of the air inlet is flush with the bottom of the grinding disc. The bottom of the grinding disc is connected to a number of ribs 11 evenly distributed in the annular direction. The ribs are air baffles and rotate with the grinding disc, thereby dividing the air inlet into a number of air inlet chambers. The air inlet adopts a volute-type tangential setting or a setting perpendicular to the bottom of the air inlet.

[0042] The annular outer partition is spaced apart at the lower inner portion of the inner shell, and the annular outer partition forms an outer inverted step structure surrounding the positive step structure, and a pre-sorting air duct is formed between the annular outer partition and the annular inner partition.

[0043] Please refer to Figure 3. In this embodiment, the pre-sorting air duct is distributed in a circular shape 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 inner side of the pre-sorting air duct, which is a positive step structure, is connected to the outer extension of the grinding disc; the top annular outer baffle of the pre-sorting air duct, which is an inverted step structure, is connected to the inner shell at the upper end, and the annular outer baffle at the lower end is connected to the outer shell, and the two annular outer baffles are respectively located on the outside of the entrance of the rising air duct, and the entrance of the rising air duct is formed between the annular outer baffles at both ends. Furthermore, 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 annular inner baffle is installed on the lower part of the grinding disc through a rib frame. The annular inner baffle is coaxial with the grinding disc and is driven to rotate by the grinding disc. The annular inner baffle and the annular outer baffle are alternately arranged from the upper opening to the lower opening of the sorting air duct.

[0044] The pre-sorting air duct is composed of two groups of circular or polygonal conical rings that are separated from each other by a certain distance, overlapped up and down, and concentrically arranged with each other, that is, it is composed of a stepped screening group on the radial outside and an air guide group on the radial inside. A screening zone is formed between the radially outer and radially inner ring groups, and the diameter of the upper end of the screening zone is larger than that of the lower end of the screening zone.

[0045] Refer to Figure 5. After grinding, the powder particles are ejected from the grinding disc and fall onto the topmost annular inner baffle, which is arranged in a straight staircase. Gravity then forces them onto the opposite annular outer baffle, alternating between the inner and outer baffles in a zigzag pattern. Hot air from the inlet duct enters through the gaps between the inner baffles, pre-sorting and drying the powder particles as they fall. Pre-sorted light powder particles follow the airflow through the outer baffle into the ascending duct, while heavier coarse powder falls to the next baffle, where it is thoroughly dispersed and air-sorted with each impact. After passing through all the baffles, the powder finally falls from the lower end of the pre-sorting duct into the vertical roller mill's discharge outlet. Fine powder, carried into the ascending duct by the airflow through the outer baffle, enters the outlet for secondary sorting.

[0046] Please refer to Figures 5 and 6. The specific parameters of the pre-sorting air duct in this embodiment are as follows:

[0047] (1) For the sorting material entering the pre-sorting air duct, the feed concentration Cs is 2.6~5.0kg / m 3 .

[0048] (2) There are multiple annular outer baffles, and the length, angle, and spacing between the radial outer ring parts of each annular outer baffle in the annular outer baffle forming an inverted step structure are the same; the number of annular inner baffles is the same as the number of annular outer baffles, and the length, angle, and spacing between the radial outer ring parts of each annular inner baffle in the annular inner baffle forming a positive step structure are the same.

[0049] (3) The partition is set as shown in Figure 6. The angle A2 between the upper plate surface of the inner annular partition and the outer annular partition is 90°; the angle between the upper plate surface of the outer annular partition and the horizontal plane is A3, 40°. <A3<80°。

[0050] (4) The width of the inner annular partition is L3, and the width of the outer annular partition is L4, 3 / 2 <L3 / L4<3 / 1。

[0051] (5) The number of annular inner baffles is the same as the number of annular outer baffles, both of which are N.

[0052] (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 conducive to the separation of coarse particles.

[0053] (7) The vertical distance between the lower edge of the annular inner baffle and the upper surface of the adjacent annular outer baffle below it is D1, and the vertical distance between the lower edge of the annular outer baffle and the upper surface of the adjacent annular inner baffle below it is D2, then 1.5 / 1 <D1 / D2<2 / 1。

[0054] Please refer to Figure 4. The inner shell is arranged inside the outer shell, and an ascending air duct is formed between the inner shell and the outer shell. A spiral partition 12 is provided between the outer shell and the inner shell, and the spiral partition forms a spiral ascending air duct around the center line of the outer shell between the outer shell and the inner shell. The ascending air duct connecting the pre-sorting air duct and the air outlet of the vertical roller mill is set as a cavity, and the cavity can be used as an ascending air duct for air material transportation, which can not only reduce the long-term erosion of the internal components of the vertical roller mill by the wind, extend the service life, and reduce the amount of routine maintenance. Moreover, the interior of the cavity is set in a spiral shape, which can not only optimize the flow field distribution and reduce local vortices for the gas rising from top to bottom, but also play a role in local sedimentation.

[0055] Example 2

[0056] This embodiment provides an ultrafine product grinding equipment. Please refer to Figures 7 and 8. On the basis of the vertical roller mill provided in Example 1, a dynamic powder classifier 13 can be set between the grinding part and the air outlet of the vertical roller mill, and the air outlet of the dynamic powder classifier is the air outlet of the vertical roller mill. The dynamic powder classifier on the upper part of the vertical roller mill is a sorting cage mechanism, and the sorting cage is the main component. Its working principle is to feed the ground raw materials into the rotating sorting cage. During the rotation of the sorting cage, due to the action of centrifugal force, finer particles will be pushed to the inner periphery of the sorting cage, while coarser particles will move toward the outside. Finer particles are guided out of the air outlet on the upper part of the outer shell under the action of airflow, while coarser particles fall to the grinding disc for re-grinding.

[0057] The dynamic powder separator air inlet is composed of an inner shell and an outer shell, each forming an ascending air duct. The upper end of the inner shell is connected to the bottom of the dynamic powder separator air inlet, and the upper end of the outer shell is connected to the upper end of the dynamic powder separator air inlet. In this embodiment, by adding a dynamic powder separator, the vertical roller mill can perform multi-stage separation, improving separation efficiency and reducing system circulation load.

[0058] Example 3

[0059] Please refer to Figure 9, which shows a process system for producing ultra-fine product powder grinding. 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 discharged from the vertical roller mill and fed into the small bin through the elevator 15 can be mixed in. The air outlet of the vertical roller mill is connected to the dust collecting device 17, through which the ultra-fine powder particles are collected as finished products. The circulating fan 18 is connected to the air outlet of the dust collecting device, and 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 further recycling, and the other path of hot air is directly discharged to the chimney 19. This system improves the sorting efficiency and sorting accuracy through multi-stage gradient sorting, can achieve product particle size control, reduce the system circulation load, reduce system energy consumption, reduce the workshop height, and save investment costs.

[0060] Example 4

[0061] Please refer to Figure 10 , which shows a process system for producing manufactured sand using the vertical roller mill of Example 1. The system includes a raw material buffer bin 16, the vertical roller mill 14 of Example 1, a powder selector 20, a vibrating screen 25, and a de-powdering mechanism 22. The de-powdering 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 manufactured sand. The bottom discharge port of the vertical roller mill is connected to the vibrating screen 25, which returns the powder particles above the screen to the vertical roller mill via an elevator 15. The air outlet of the vertical roller mill is connected to the inlet of the powder selector, which is connected to the cyclone, which is connected to the circulating fan.

[0062] The powder particles are crushed, ground and pre-sorted by the vertical roller mill 14 and then enter sorting equipment such as the vibrating screen and powder separator, thus realizing efficient, low-energy and clean production of machine-made sand.

[0063] This embodiment is also provided with a flow stabilization bin, which ensures the stability of the powder particles entering the mill, improves the crushing and grinding efficiency of the vertical mill, reduces system output fluctuations, ensures stable operation of the system, improves energy utilization, reduces production energy consumption, improves equipment operation safety, and reduces operation failure rate.

[0064] The raw materials enter the vertical roller mill from the raw material bin via a conveyor belt. After grinding and pre-sorting, the coarse particles move downward under the action of gravity. The powder particles after de-powdering enter the vibrating screen. The vibrating screen is provided with a certain size of sieve holes. The particles that meet the size requirements pass through the vibrating screen into the finished product and form finished sand. The vibrating screen in this example can be set with a sieve hole size according to different needs. For example, the sieve hole diameter is 2.36mm or 1.18mm. Accordingly, particles smaller than 2.36 or smaller than 1.18mm are used as finished sand. Particles that do not meet the requirements and are larger than the sieve hole size of the vibrating screen are returned to the vertical roller mill for grinding and then the next cycle is carried out. Fine powder smaller than 0.075mm or 1.18mm passing through the vertical roller mill's outlet is driven upward by the gas. The gas carries the fine powder from the classifier into the cyclone. The coarse material (0.075-1.18mm) at the bottom of the classifier is used as a manufactured sand product. The cyclone separates the fine powder from the gas, and the fine powder enters the next process. The gas enters the circulating fan. After passing through the circulating fan, part of the gas returns to the vertical roller mill, and part is discharged into the atmosphere through the chimney 19, completing the de-powdering process. The above embodiment is suitable for a process system where the moisture content of the powder particles is less than 2.5%.

[0065] In a vertical roller mill, the ground and pre-sorted powder particles move downward under gravity, are discharged through the bottom outlet of the pre-sorting section, and enter a vibrating screen for screening, resulting in a mixed manufactured sand product with a particle size smaller than a certain value. Simultaneously, the fine powder at the outlet of the vertical roller mill is driven upward by the airflow, where it is separated by the powder concentrator, removing the harmful fine powder and entering the next process.

[0066] This technology replaces the original cone crusher, twin-rotor sand making machine, vertical shaft impact crusher, etc., reduces the content of needle-like particles in the product, reduces the content of fine powder in machine-made sand, improves the product quality of machine-made sand, improves the energy utilization rate of sand making, reduces production energy consumption, is conducive to large-scale production, improves resource utilization, improves concrete performance, and is beneficial to project quality.

[0067] Example 5

[0068] Please refer to FIG. 11 . Different from the fourth embodiment, the outlet of the circulation fan in this embodiment is further provided with a dust collector 24 and a tail exhaust fan 23 in sequence.

[0069] After passing through the circulating fan 18, part of the gas enters the dust collector, and after dust removal by the dust collector, it is discharged into the atmosphere through the tail exhaust fan and chimney 19. The dual fan system consisting of the circulating fan 18 and the tail exhaust fan is used to increase the on-site dust collection effect. The dust collector can reduce the dust emission concentration to 5mg / m 3This achieves ultra-clean emissions, benefiting the environment. The tail exhaust fan also facilitates regulation of circulating air volume, especially when the moisture content of the incoming powder exceeds 2.5%, and the finished product requires a high moisture content (for example, manufactured sand for dry mortar with a moisture content of less than 0.5%). This allows the humid air to be discharged, reducing condensation within the system and extending pipe life. Hot air can also be connected in series before sorting to dry the powder particles after grinding in the vertical mill, preventing condensation from affecting the entire circulation system.

[0070] Example 6

[0071] The difference from the fourth embodiment is that, as shown in Figure 12, the vibrating screen 25 of this embodiment is provided with several layers of screens with different apertures. The screens are arranged in one or more layers, and can be screened step by step to meet the needs of multiple products.

[0072] The vibrating screen in this embodiment has two layers of screens: the upper layer has a 4.75mm aperture and the lower layer has a 2.36mm aperture. Particles larger than 4.75mm above the upper layer are returned to the roller mill for grinding. Particles between 2.36 and 4.75mm are used as coarse sand, while particles below 2.36mm are used as medium and fine sand. This technology has the advantage of enabling the production of machine-made sand products of varying particle sizes, improving production efficiency and reducing operating costs.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An air duct structure of a vertical roller mill, characterized in that: It includes an outer shell and a grinding disc arranged at the lower inner part 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, and is characterized in that: the interior of the outer shell is provided with an air inlet duct located below the grinding disc, a pre-sorting air duct located below the periphery of the grinding disc, and an ascending air duct located on the side of the outer shell, the air inlet duct is connected to the air inlet, the pre-sorting air duct is provided with a partition for breaking up the powder, the ascending air duct is connected to the air outlet, and the airflow introduced from below the grinding disc passes through the air inlet duct, the sorting air duct and the ascending air duct in sequence.

2. The air duct structure of the vertical roller mill according to claim 1 is characterized in that include: an annular inner baffle, the annular inner baffle being spaced apart below the outer edge of the grinding disc, the outer ring portion of the annular inner baffle forming a positive step structure downward from the outer edge of the grinding disc, and the annular air inlet duct being formed between the annular inner baffles; an annular outer baffle, the annular outer baffle being spaced apart at the lower inner portion of the outer shell, the annular outer baffle forming a peripheral inverted step structure surrounding the positive step structure, the pre-sorting air duct being formed between the annular outer baffle and the annular inner baffle; The inner shell is arranged on the inner side of the outer shell, and the rising air duct is formed between the inner shell and the outer shell.

3. The air duct structure of the vertical roller mill according to claim 2, characterized in that: The annular inner partition is mounted on the lower portion of the grinding disc via a rib frame. The annular inner partition is coaxial with the grinding disc and is driven to rotate by the grinding disc.

4. The air duct structure of the vertical roller mill according to claim 3, characterized in that: The annular inner baffles and the annular outer baffles are alternately arranged in a direction from the upper opening to the lower opening of the sorting air duct.

5. The air duct structure of the vertical roller mill according to claim 4, characterized in that: 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.

6. The air duct structure of the vertical roller mill according to claim 5, characterized in that: A spiral partition is provided between the outer shell and the inner shell, and the spiral partition forms a spiral rising air duct between the outer shell and the inner shell that surrounds the center line of the outer shell.

7. The air duct structure of the vertical roller mill according to claim 6, characterized in that: The angle between the upper plate surface of the annular inner partition plate and the upper plate surface of the annular outer partition plate is 90°.

8. The air duct structure of the vertical roller mill according to claim 6, characterized in that: The angle between the upper plate surface of the annular outer partition and the horizontal plane is A3, 40° <A3<80°。 9. The air duct structure of the vertical roller mill according to claim 8, characterized in that: The width of the annular inner partition is L3, and the width of the annular outer partition is L4, 3 / 2 <L3 / L4<3 / 1。 10. A vertical roller mill, characterized in that: The vertical roller mill is provided with the air duct structure according to any one of claims 1 to 9.

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