BEIJING POWER EQUIPMENT GROUP (BPEG) is the leading manufacturer of mills in China. BPEG has been manufacturing mills since the end of 1950's. They are therefore one of our oldest products.
Today an extensive range of them is available for a great variety of industrial engineering and these mills are, in most instances, designed to the customer's requirements. BPEG's product spectrum includes, for instance, medium speed mills and low speed tube ball mills and so on. For new plants and techniques, BPEG has frequently been a pioneer (trend-setter) in the planning and developing of the required powder making engineering.
A grinding table rotating round a vertical axis is driven by a planetary gearbox. The grinding rollers, mounted in fixed positions, are pressed down on the table under loading. The axes of the grinding rollers are inclined at 12°~15°, in combination with the grinding surface of the table they achieve optimum grinding effect, as experience in actual plant operation shows.
Operation and design features
The raw coal is fed centrally from above through the classifier mounted over the mill or from one side onto the rotating grinding table. On passing under the rollers the coal is ground by their action assisted by the pressure of the hydropneumatic spring loading of the roller. When the roller travels over the bed of material on the table, a system of loading frame and rods connected to the working piston of a hydraulic cylinder causes oil to be displaced from the space below the piston into hydropneunatic accumulators.
The pulverized coal is flung by centrifugal force into the zone over the nozzle ring (louver air ring) surrounding the table. Where the coal particles are swept upwards by the stream of hot air into the classifier. The intimate contact with the hot air causes the moisture contained in the coal to evaporate spontaneously, so that the desired exit temperature of the pulverized product from the mill (70°~120°) is already attained in the grinding chamber. The oversize particles rejected by the classifier fall back onto the grinding table for further size reduction. The fine particles, i.e., the finished product, are carried out of the classifier with the air.
Range of types
ZGM mills equipped with three rollers are used for coal grinding. The increase of radius of grinding table is applied in mills with a mean radius of grinding table from 650mm upwards.
Control Behavior of ZGM Coal mills
ZGM mills can be controlled within the range from 25 percent to 100 percent of throughout capacity.
Central grinding plants are operated at a constant throughput rate, which can be adapted to inter-mediate storage capacity for the pulverized coal.
Maintenance of ZGM roller grinding mills comprises:
-Changing the oil of the bearing in which the rollers are mounted, changing the oil in the gearbox
-Replacement of worn parts
-Removing reject material (if this operation is not mechanized).
Changing the grinding elements can be accomplished simply and quickly with special tools, via the hinged housing segment without disassembling the housing or ducts.