Pulverization of coal system

What is pulverization of coal? Explain pulverization of coal system.

Pulverization of coal- 

Pulverization of coal is defined as crushing of large size coal particles into powdered coal for effective and rapid burning.

Pulverization coal system-

Large capacity power plants (capacity about 100 MW) uses coal pulverization system. The pulverization of coal is done for to increase the surface area so it increases the rate of combustion.

The powdered form coal is easy to burn and it burn effectively. Therefore, Pulverization of coal increases thermal efficiency.

The pulverized coal is obtained by grinding coal in pulverising mills. The types of mills used are

a)     Ball mill

b)    Ball and race mill

c)     Bowl mill

d)    Hammer mill

Elements of pulverized coal system-

   1)    Main hopper

   2)    Weighter

   3)    Service hopper

   4)    Pulverising mill

   5)    Separator

   6)    Cyclone

   7)    Dust bin

   8)    Burner

Diagram-

fig. Pulverization of coal system

 Working of pulverized coal system- 

In main hopper crushed coal is supplied. The coal is weighted in weighter before supplied to service hopper. 

In pulverizing mill, coal received from service hopper and hot air is supplied from burner. Hot air is used for drying of coal particles.

The pulverized air-fuel mixture is supplied to separator and the large particles of coal again returned to the pulverizing mill.

Fine particles are passed to cyclone where fine particles are separated from air. The fine particles from the cyclone fall in the dust bin. Fine particles in the dust bin with hot air supplied to the burner. 

The secondary hot air is supplied to the burner so it increases combustion efficiency.

Advantages of pulverized coal system-

   1)    It is smoke free process.

   2)    It reduce air requirement during burning and promote faster burning.

   3)    It gives complete combustion.

   4)    It provides high combustion efficiency.

   5)    Any type of coal can be used as it is used in powdered form.

   6)    It has no ash handling problems.

   7)    Furnace volume required is less.

   8)    External surfaces are free from corrosion.

   9)    No standby losses.

Disadvantages of pulverised coal system-

   1)    It is costly system.

   2)    Capital cost is high.

   3)    Operational cost is high.

   4)    Maintenance cost is high.

   5)    Skilled operators and labours are required.

   6)    It causes pollution due to fine dust particles.

   7)    It requires special starting equipments.