Lignite also known as firewood coal is a mineral coal with the lowest degree of coalification. It is a brown black, lusterless low-grade coal between peat and bituminous coal. Strong chemical reactivity, easy weathering in the air, not easy to store and transport. Because it is rich in volatile matter, which is up to more than 40%, it is easy to burn and smoke. The lignite has large moisture and is easy to be weathered and broken in the air. The physical and chemical properties of the lignite determine the difficulties in the grinding process. If the traditional ball mill is used for grinding, not only the output is extremely low, but also the operation is very inconvenient, and the utilization rate of heat energy is extremely low. The vertical roller mill has become the ideal choice for the industrial application of lignite. As the manufacturer of lignite vertical roller mill, Guikuang Machinery will introduce the principle of lignite vertical roller mill in the following.
The moisture of lignite is very high. Generally, the moisture of raw materials arriving at the plant is as high as about 30%. If the traditional ball mill is used for grinding, it must be very difficult. Not only is the output extremely low, but also the operation is very inconvenient. The production needs must be met by greatly expanding the equipment model, so that the energy consumption will be very large. All investments and high energy consumption operations will also bring high operating costs to the owner. Secondly, the volatile matter of lignite is very high, up to more than 40%, with low ignition point and easy combustion, so we must pay special attention to the temperature control of the system in the grinding process. Thirdly, the calorific value of lignite is very low, generally lower than 13376kJ/kg, with low calorific value and high combustion capacity; Therefore, the equipment used for grinding must be able to achieve a relatively high production capacity, otherwise it cannot meet the calcination needs of the kiln system. The last thing to say is the use of wear-resistant parts. Lignite often contains more gangue and other kinds of ore components, causing great damage to vulnerable parts. Therefore, we must fully consider the structural design and material design of wear-resistant parts to meet the requirements of grinding conditions. Considering the above factors and the operation effect of on-site equipment, most of Guikuang’s owners will choose vertical roller mill to grind lignite.
The structure of GKLM pulverized coal vertical roller mill is basically the same as that of ordinary pulverized coal vertical roller mill, but there are great differences in matching of each component: its grinding device is the grinding device of the pulverized coal vertical roller mill, but the powder concentrator is matched with the dynamic and static combined separator of GKLMX pulverized coal superfine vertical roller mill, which greatly enhances the drying capacity of the mill while ensuring the grinding effect, and can solve the problem of high moisture content of lignite raw materials. Equipped with large explosion-proof superfine separator, structure of the lignite grinding mill still uses traditional tire type roller surface and bowl type disc lining; The main reducer and grinding roll are equipped with a forced thin oil lubrication system; The valves and oil pumps in the hydraulic system are fully automatic controlled. The working mechanism of the vertical roller mill pulverizing lignite is: the motor drives the reducer to rotate, the grinding plate is directly connected with the reducer, and rotates with the reducer thrust plate. The materials go down to the middle of the grinding plate through the fully sealed belt weigher. The materials spread around the grinding plate through centrifugal force and enter under the grinding roller for pulverizing. The fine materials after grinding are carried into the powder concentrator by the high-speed air flow at the wind ring, and the finished products enter the dust collector through the high-speed rotating rotor, Non finished products will fall freely from the ash hopper onto the grinding plate for re grinding.