Pulverizer- Lifeline of coal Industry

Generally,  pulverizer or grinder is a mechanical device which is used for grinding different types of materials. Pulverizer machines are used to grind materials into tiny shards including glass, aluminum, coal, rock, concrete, plastic, resin, tires, and other medical waste. Impactors, crushers, shredders, hammer mills, ring mills, and double roll granulators are different types of pulverizers that have found application in several industries.  Commonly, they are used in coal industry, plastic industry, in fossil fuel power plants and coal fired power plants.In coal industry, the main application of pulverizer is to crush the coal to fine powder. In plastic industry, they are used for plastics pulverizing, which includes PVC recycling, compounding, rotational molding and master batching. Apart from this, soil pulverizers are also used to breakup, smooth and prepare dirt areas such as arenas for use, or to prepare rough dirt areas for primary seeding.Types of  Pulverizer

Pulverizers are available in a wide range including ring and cage mill pulverizer, coal pulverizer, demolition pulverizer. ball mills, ball and tube mills, MPS mills, bowl mills, El mills, Roll wheel, vertical mills, turbo mills, hammer mills and more.Some commonly used coal pulverizers are:

1) Low Speed - like ball tube mills2) Medium Speed - like bowl, ball and race roller mills3) High Speed - The high speed mills are used mainly for ligniteBall tube mills are either suction or pressurized type. In the suction type, the exhauster is used for lifting the milled coal from the pulverizer to the furnace through a cyclone. The tube mills have a large circular drum, with adequate ball charge, which is rotated at about 70-75% of the speed at which the ball charge would be held against the inner surface by centrifugal force. In this mill the grinding balls can be replenished on the line.In the pressurized type, the hot primary air is used for drying the coal and to transport the milled coal to the furnace. Leakage in the mill area is high in this technique.Usually three types of balls are used in ball mill with three different diameters. Most of the ball mills had a single inlet and outlet, but now a days ball are used in both ends to feed coal and also for taking out pulverized coal. Ball mills are always preferred to be operated at full capacity because the power consumption of this type of mill is high at lower loads when compared with other types. Ball mills can be designed for a very high capacity like 60-80 tons per hour output for a specific coal.Vertical spindle millsVertical spindle mill is commonly used large steel balls ranging from 2 to 6 rings for pulverizing. Vertical spindle mill comes in types like conical rollers with shallow bowl, deep bowl, etc. These types of mill are designed normally up to 50-60 tons per hour for a specific coal, whereas several vertical mills are designed with 90 tons per hour output.High speed impact millsHigh speed impact mills are mainly used in pulverizing lignite. Today all boiler designers opt to use ball or vertical spindle mill for coal other than lignite. This type of mill uses a central horizontal shaft which has a number of arms, and a beater of different design is attached to these arms to beat the coal to be pulverized.While selecting the type of mill boiler, the coal characteristics, the overall system being used, and the maintenance requirement must be considered carefully.Tips to improve the performance of Pulverizers:In order to boost the performance of a  pulverizer,  engineers should be able to successfully optimize pulverizer performance through its tolerance, settings, methodical testing and analysis. Extra care should be given on the internal performance relationships and their dependence upon externally controlled parameters. Usually, Pulverizers utilize relatively obscure applications of simple engineering principles.