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1. Working principle and types: There are many different forms of vertical mills, but their working principle is essentially the same. All these types of mills are equipped with grinding rollers (or grinding elements equivalent to grinding rollers), which move along a horizontal circular path on the grinding table. Through the vertical pressure applied externally to the grinding rollers, the material on the grinding table is subjected to both compression and shear forces, thereby being crushed. The grinding process of the material involves: an electric motor driving the grinding disk to rotate through a reducer; the material falls from the feed opening into the center of the grinding disk, moves toward the edge of the disk under the effect of centrifugal force, and is crushed by the grinding rollers. The ground material then leaves the grinding disk and is carried upward by high-speed air currents to a separator integrated with the vertical mill. The coarse powder returns to the grinding disk after passing through the separator to be ground again ； The fine powder flows out of the mill with the gas and is collected in the system’s dust collection device, where it becomes the product. Inside the vertical mill, the material is transported by pneumatic means, which requires a high air flow rate; thus, waste heat gas can be utilized to carry out both drying and grinding operations. The grinding elements of vertical mills used in cement production come in various forms, including cylindrical, frustum-shaped, and spherical shapes; the surfaces of the grinding rollers can also be flat, curved, or convex. The forces applied to the grinding roller to keep it in close contact with the material bed along the grinding path include spring pressure, hydraulic pressure, and so on. 2. Structure: The diagram below shows a schematic of the vertical mill’s structure; it consists of a separator, grinding rollers, a grinding disc, a pressure application device, a reducer, a motor, and a housing. In the figure, A, B, C, D, and E represent the main structural dimensions of Wumo. The separator is an important component for ensuring the fineness of the product; it consists of a drive system, rotor, air guide vanes, housing, a coarse powder discharge cone, and an air outlet. The grinding roller is the main component used for crushing and grinding materials; it consists of a roller sleeve, a roller core, a shaft, bearings, and a roller support. Each mill has 2 to 4 grinding rolls. The grinding disc is fixed to the vertical shaft of the reducer, and the reducer drives the grinding disc to rotate. The shapes of the grinding discs vary among different types of vertical mills; these discs are composed of a disc base, lining plates, retaining rings, and other components. The pressure application device is an important component that provides the grinding pressure; it consists of a high-pressure oil station, hydraulic cylinders, tie rods, accumulators, etc., and is capable of applying sufficient pressure to the grinding rollers to crush the material. The pressure-applying device can also be a spring. The reducer is required to not only reduce speed and transmit power to drive the grinding disc, but also bear the weight of the grinding disc and the material, as well as the grinding pressure. 3. POLYSIUS type vertical mill: The structure of the Polysius vertical mill is shown in the figure above. It has two pairs of grinding rollers, with each pair consisting of two narrow rollers mounted on the same shaft and capable of rotating at different speeds. The grinding disc has two annular grooves, and the grinding roller is tire-shaped, pressing against these grooves during operation. The relative sliding speed between the grinding roller and the grinding plate is low, and the grinding roller can swing; thus, even when the grinding roller sleeve and the grinding plate lining are worn out, good grinding performance is still maintained, without affecting the grinding effect. The roller sleeve has a symmetrical structure, allowing it to be used on the other side after one side becomes worn out. The grinding process of the material involves the use of grinding rollers that apply pressure to the material through hydraulic and pneumatic mechanisms, thereby crushing it. The crushed material is moved toward the edge of the grinding disk, where air streams emitted from nozzles surrounding the disk lift this material into the separator. After separation, the coarse powder is collected and returned to the grinding disc, while the fine powder is collected and discharged in the dust collector. At low gas flow rates, the coarse powder cannot be lifted by the upward airflow; it passes through the nozzle ring and falls out of the mill, where it is transported by a bucket elevator to the feed device of the vertical mill and fed back into the mill for further grinding. The characteristics of this cycling mode are as follows: ① By adjusting the air ring valve, the fineness of the product can be changed, and the load on the material bed inside the mill can be kept uniform and stable, thereby improving the grinding efficiency ； ②The external circulation of coarse particles helps to reduce the power consumption of the fan as well as the overall electrical consumption of the system.