The vertical mill is a type of milling equipment widely used in cement, chemical industry, coal and electricity industries, featured by a small size, low energy consumption, little noise, simple process and compact arrangement, etc, setting crushing, drying, milling and selecting in one. Therefore, it’s the preferred equipment for grinding and milling raw materials for a modern cement plant.
This type of mill mainly consists of the powder classifier, rollers device, millstones device, compressing device, speed reducer, motor and the shell part. The separator is an energy-saving powder-classification device with high efficiency. The roller is used to grind and crush the materials. The millstone is fixed on the output shaft of the speed reducer where the mill roller grinds the material. The compressing device is the part that provides the grinding force sufficient to crush the material. .
Ⅰ. The Open-loop System of the Single-pulse Dust Remover In this system, the raw material is transferred into the raw material storage bin through the bucket elevator, and then, it will be conveyed into the air-lock feeder by the belt conveyor after being weighted and de-ironed. This process can prevent the air from entering while the raw material is being transferred into the mill. The product collection is preformed by a pulse dust remover, which reduces the number of the equipment and simplifies the configuration of the system. The collected product will be transferred into the finished product bin by the screw feeder through the bucket elevator. This system is capable of drying the moist material that entered the mill. .
Ⅱ. The Closed-loop System of the Cyclone and Pulse Dust Remover.
The differences between this system and the open-loop system of the single-pulse dust remover are that: the product collection of this system is performed by a group of cyclone dust removers, and part of the air from the induced draft fan is led into the mill for cyclic utilization, which can reduce the work load and the air amount that passes through the dust collector. A pulse dust remover may be used as the final dust removing device. .
Ⅲ. The Closed-loop System of the Single-pulse Dust Remover.
The differences between this system and the single collector system are that: the collected product of this system is conveyed into the finished produce storage bin by the pneumatic conveying system. At the same time, most of the air from the induced draft fan is led into the mill for cyclic utilization. .
1. Low operation cost:
(1) High grinding efficiency. the vertical mill grinds the material with the mill roller and the material bed, which makes the energy consumption quite low. Compared with the ball-milling system, the power consumption of the grinding system is decreased by 40-50％. And the power-saving effect is significant due to the increasing humidity of the raw material.
(2) Little metal loss. The lining plate and mill roller are made of special material, which reduces the operation cost and prolongs the service life and achieves high usage.
(3) Equipped with an external cycling device, which further reduces the power consumption.
(4) Large particle size of the material is transferred into the mill. The particle size is up to 5％ of the diameter of the mill roller, as 40~100mm in general. Thus, the secondary crushing can be left out when using large and medium sized vertical mills.
2. Low construction cost:
(1) The process of the vertical mill is simple. Compared with the ball-milling system, the area occupied by the vertical mill is reduced by about 50%, and the construction cost is reduced by 70%. The construction area is small, so little space is occupied.
(2) The vertical mill sets crushing, drying, grinding and classification conveying in one, the system is simple and the arrangement is compact. It can be arranged in the open air, which contributes to the low construction cost.
3. Easy and reliable operation:
(1) Equipped with an automatic control device, and the remote control can be achieved, which simplifies the operation.
(2) Provided the device used to prevent the direct contact between the roller jacket and the lining plate of the millstone, which can avoid the crushing and strenuous vibration.
4. Strong drying capability. The vertical mill conveys the material by airflow. The inlet air temperature can be controlled when the material with large content of moisture is being grinded so that the final moisture requirement for the product is reached. the material with the moisture content of 12~15％can be dried inside the vertical mill. This is not to be achieved even by a drying ball mill, because it is only capable to dry the material with moisture of 3~4％.
5. The product quality is stable and the particle size graduation is uniform. The material stays inside the mill just for a short time, which makes it is easy to inspect and control the particle size and the chemical composition, so the product quality is stable.
6. Convenient in maintenance. The hydro-cylinder, turnover swim arm, roller jacket and the lining plate can be replaced within a short time during maintenance.
7. Environment friendly, energy-saving; small vibration, low noise and less dust. The operating environment is clean, which is consistent with the environmental protection requirements.
The vertical mill mainly consists of the separator, mill roller, millstone, compressing device, speed reducer, motor and the shell part. According to the locations of the conditioning tower and the dust remover, there are two arrangement programs for the vertical mill, namely: three-fan system and double–fan system. The product is collected by the dust collector. This arrangement mode can reduce the working negative pressure and the air amount passing through the dust collector. Either an electric dust collector or a bag-type dust collector can be used as the final dust-removing device. The dust collecting device can be an electric dust collector or a bag-type dust collector.
This system reduces the number of the equipment and simplifies the system configuration. The working principle is as follows: The motor drives the millstone to rotate through the speed reducer. At the same time, hot air enters the vertical mill through the air inlet. The material falls onto the central part of the mill plate through the feed opening. Due to the centrifugal force, the material moves towards the edge of the mill plate from the central part. It will be grinded and crushed by the mill roller when it passes through the circular groove on the mill plate. The crushed material will go on moving towards the edge of the millstone until it is carried away together with the air flow at the air ring, while the large-particle material drops onto the mill plate for further grinding.
When the material in the air flow goes through the separator on the upper part, the coarse material will fall onto the millstone due to the function of the guiding blade. The fine material will go out of the mill together with the airflow and be collected by the dust collector of the system. The collected powder is namely the product processed by the mill. The material is dried to the required temperature and humidity in the process of contacting with the shell part. The required coarseness/fineness of the product can be achieved by adjusting the angle of the guiding fan blade (the small-sized vertical mill can not be adjusted) and rotating speed of the separator.