Vertical mill application:

Vertical mill is an energy-saving, versatile new type of powder grinding equipment, suitable for industries such as cement, power, chemicals, and non-metallic minerals. It is particularly applicable for grinding black clinker in cement plants and preparing raw materials in white cement factories. With its high efficiency, low electricity consumption, large drying capacity, easily adjustable product fineness, uniform particle size, easy control of chemical composition, low noise, minimal metal wear, dust-free operation, simple system process flow, small land occupation, and cost-effective investment, it has been widely used in the cement and non-metallic mineral industries both domestically and internationally.

Main Structure and Functions:

The RHM and PRM vertical mills are mainly composed of separators, grinding rollers, grinding disks, pressure devices, reducers, electric motors, and casings, etc.

The separator is a crucial component that determines the fineness of the product. It consists of adjustable drive mechanisms, wheels, air guide vanes, casings, coarse powder discharge cones, and exhaust outlets, similar in working principle to the classifier.

The grinding rolls are the main components 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 fixed on the output shaft of the reducer, with the upper part serving as the material bed, featuring a circular groove on it.

The pressurizing unit is a component that supplies grinding pressure, consisting of a high-pressure oil station, hydraulic cylinder rods, accumulators, etc., capable of applying sufficient pressure to the roller 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 reducer, while hot air enters the mill through the inlet. Material falls onto the center of the disc from the feed opening, moving towards the edge due to centrifugal force. 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 picked up by the air ring's airflow. Larger particles fall back onto the disc for re-grinding. As the material flows through the separator, under the action of guide vanes and the rotor, coarse material falls onto the disc in a conical hopper, while fine powder exits with the airflow and is collected in the system's dust collection unit, which is the final product. The material is dried during contact with the gas, reaching 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 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 moisture content of the raw materials.

2. Large drying capacity; vertical mill uses gas to convey material. When processing materials with high moisture content, it can control the air temperature to achieve the required moisture level. Inside the vertical mill, it can dry materials with up to 12-15% moisture content, whereas ball mills can only dry materials with up to -4% moisture.

3. The product's chemical composition is stable with uniform particle distribution. Since the material stays in the vertical mill for only 2-3 minutes, compared to 15-20 minutes in ball milling, the chemical composition of the product produced by the vertical mill can be quickly measured and corrected. The fluctuations in product 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 quickly adjusted by changing the speed of the separator rotor, resulting in a uniform particle size, which is advantageous for calcination.

4. The process is simple, with a small building area and minimal space requirement. 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 straightforward, the layout is compact, and the building area is only 50-60% of that required for a ball mill system.

5. Low noise, minimal dust, and a clean operating environment. The vertical mill operates with no direct contact between the grinding roller and the grinding disc, eliminating the metallic impact sounds of steel balls colliding with each other or with the lining in ball mills. Due to its reduced noise level, it is approximately 20-25 decibels quieter than ball mills. Additionally, the vertical mill is equipped with an integral seal, operating the system 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, and the service life of the roller sleeves and lining plates for grinding cement raw materials exceeds 8,000 hours, with an operational rate up to 95%.

7. Economical usage.