Vertical mill application:
Vertical mill is a high-efficiency, versatile new powder grinding equipment for energy-saving applications, suitable for industries such as cement, power, chemicals, and non-metallic minerals. It is particularly adapted for the grinding of black clinker in cement plants and the preparation of raw materials in white cement factories. With its high efficiency, low power consumption, strong drying capacity, easily adjustable product fineness, uniform particle size, easy-to-control chemical composition, low noise, minimal metal wear, dust-free operation, simple system process flow, small land occupation, and cost-effective investment, it is widely used in both domestic and international cement and non-metallic mineral industries.
Main Structure and Functions:
The RHM and PRM vertical mills are mainly composed of a separator, grinding roller, grinding disc, pressure device, reducer, motor, and housing, etc.
The separator is a critical component determining the fineness of the product, consisting of a variable-speed transmission, wheels, guide vanes, housing, coarse powder hopper, and outlet, 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 on it.
The pressure unit is a component that provides grinding pressure, consisting of a high-pressure oil station, hydraulic cylinder rod, accumulator, etc., and is capable of exerting sufficient pressure on the mill roll to crush the material.
The reducer not only transmits power but also bears the weight and grinding force of the millstone.
Operating Principle:
The motor drives the grinding disc through a reduction gear, while hot air enters the mill from the inlet. Materials fall onto the center of the disc from the feed opening. Due to centrifugal force, the materials move towards the edge of the disc, crushed by the roller as they pass through the annular grooves. They continue moving towards the edge until they are picked up by the air flow at the wind ring, with larger particles falling back onto the disc for re-grinding. As the materials move through the air flow, they pass through a separator, where coarse materials fall onto the disc from a conical hopper under the action of guide vanes and the separator rotor, while fine powder exits with the air flow. The collected dust in the system's dust collection unit is the product. Materials are dried during contact with the gas to achieve 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 features:
1. High powder grinding efficiency; vertical mills use the powder bed grinding principle to grind materials, featuring low energy consumption. The electrical consumption of the powder grinding system is 20-30% lower than that of the ball mill system, and the energy-saving effect becomes more pronounced with the increase in raw material moisture content.
2. High drying capacity; the vertical mill uses gas conveyance for materials. It can control the inlet air temperature when grinding materials with high moisture content, ensuring the product reaches the desired moisture level. The vertical mill can dry materials with up to 12-15% moisture content, whereas ball mills can only dry materials with a moisture content of up to -4%.
3. The product's chemical composition is stable with even particle grading. Since the material only stays 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 fluctuation in product chemical composition is minimal, which is beneficial for homogenization. Moreover, qualified products in the vertical mill can be separated out 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. Simple process flow, small floor area, minimal space occupation. The vertical mill features a separator, eliminating the need for a classifier and elevator. The dust-laden gas exiting the mill can be directly fed into a dust collector or baghouse, where it is collected as the finished product. Therefore, the process is simple, the layout is compact, and the floor area is only 50-60% of that of the ball mill system.
5. Low noise, minimal dust, and clean operating environment; the vertical mill operates without direct contact between the grinding roller and the grinding disc, eliminating the metallic impact sounds of steel balls colliding in a ball mill or hitting the lining plates. Due to its reduced noise level, it is approximately 20-25 decibels quieter than a ball mill. Additionally, the vertical mill is equipped with an overall seal, and the system operates under negative pressure, resulting in less dust and a cleaner environment.
6. Minimal 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, and the life of the roller sleeve and lining plate for grinding cement raw materials is over 8,000 hours, with an operation rate of up to 95%.
7. Economical to use.
