Vertical Mill Applications:
Vertical mills are high-efficiency, energy-saving, and versatile new powder grinding equipment, suitable for industries such as cement, power, chemicals, and non-metallic minerals. They are particularly ideal for grinding black clinker in cement plants and preparing raw materials for white cement factories. With advantages like high efficiency, low power consumption, large drying capacity, easily adjustable product fineness, even particle size distribution, easy control of chemical composition, low noise, minimal metal wear, dust-free operation, simple system process flow, small land occupation, and cost-effectiveness, they are widely used in the cement and non-metallic mineral industries both domestically and internationally.
Main Structure and Functions:
The vertical grinding mills of RHM and PRM models are mainly composed of separators, grinding rollers, grinding rings, pressure devices, reducers, electric motors, and casings, etc.
The separator is a critical component determining the fineness of the product, consisting of a variable-speed transmission, wheels, air guide vanes, housing, coarse powder discharge cone, outlet, etc., similar in working principle to the classifier.
The grinding rolls are the main components used for crushing and grinding materials. Inside the mill, there are two pairs of grinding rolls, each pair mounted on the same shaft and rotating at different speeds.
The millstone is mounted on the output shaft of the reducer, with the upper part serving as the material bed, featuring annular grooves.
The pressure unit is a component that supplies grinding pressure, consisting of a high-pressure oil station, hydraulic cylinder rod, accumulator, etc., and is capable of applying sufficient pressure to the mill rolls for material crushing.
The reducer not only transmits power but also bears the weight and grinding force of the grinding disk.
Operating Principle:
The motor drives the mill disc through a reducer, while hot air enters the mill from the inlet. Material falls onto the center of the disc from the feed opening. Due to centrifugal force, the material moves towards the edge of the disc. As it passes through the annular grooves on the disc, it is crushed by the roller and continues moving towards the edge until it is lifted by the air flow at the wind ring. Larger particles fall back onto the disc for re-grinding. As the material in the air flow passes through the separator, coarse material falls onto the disc due to the action of the guide vanes and the rotor, while fine powder exits with the air flow, collected in the system's dust collection unit as the product. The material is dried during contact with the gas to reach the required product moisture content. By adjusting the angle of the guide vanes and the speed of the separator rotor, products of different fineness can be obtained.
Features:
Compared to ball mills, vertical mills have the following characteristics:
1. High powder grinding efficiency, vertical mills use the material bed powder grinding principle to grind materials, with low energy consumption. The power consumption of the powder grinding system is 20-30% lower than that of the ball mill system, and the electricity-saving effect becomes even more pronounced with the increase of raw material moisture.
2. Large drying capacity; the vertical mill employs gas conveyance for materials. It can control the inlet air temperature when processing materials with high moisture content, achieving the final moisture content in the product. Inside the vertical mill, it can dry materials with up to 12-15% moisture content. Even ball mills for drying can only dry materials to around -4% moisture content.
3. The chemical composition of the product is stable with even particle distribution. Due to the material only staying in the vertical mill for 2-3 minutes compared to 15-20 minutes in a ball mill, the chemical composition of the product produced by the vertical mill can be quickly measured and corrected. The fluctuations in chemical composition are minimal, which is beneficial for homogenization. Moreover, qualified products in the vertical mill can be separated promptly, avoiding over-grinding. The fineness of the product can be rapidly adjusted by changing the speed of the separator rotor, ensuring uniform particle size, which is advantageous for calcination.
4. The process is simple, with a small floor area and minimal space occupancy. The vertical mill is equipped with a separator, eliminating the need for a sifter and hoist. The dusty gas from the mill can directly enter a dust collector or baghouse, and upon collection, it becomes the finished product. Therefore, the process is straightforward, the layout is compact, and the building area is only 50-60% of the ball mill system.
5. Low noise, minimal dust, and clean operation environment. The vertical mill operates without direct contact between the grinding roller and the grinding disc, eliminating the metallic impacts of steel balls colliding with each other or with the lining plates found in ball mills. Due to the reduced noise, it is approximately 20-25 decibels quieter than a ball mill. Additionally, the vertical mill features a complete seal and operates under negative pressure, resulting in less dust and a cleaner environment.
6. Low metal loss and high utilization rate; due to no direct metal contact during the vertical mill's operation, wear is minimal. The unit product wear is typically 5-10 grams per ton. For the grinding of cement raw materials, the roller sleeve and liner have a lifespan of over 8,000 hours, with an operational rate of up to 95%.
7. Economical in use.
