164 POWER PLANT ENGINEERING
(iii) Coal air mixture should move away from the burner at a rate equal to flame front travel in
order to avoid flash back into the burner.
Raw Coal
Bunker
Pulverizer
Feeder
Control
Damper
Primary
Air Fan
Pulverized Fuel
and Air Piping
Pulverized Fuel
Burners
Cold (Tempering) Air
From Forced Draft Fan
Tempering Air
Damper
Hot Air From
Boiler Air Heater
Furnace
Burner Windbox
Fig. 4.28. A Pulverised Coal Burner System.
The various types of burners are as follows :
- Long Flame Burner (U-Flame Burner). In this burner air and coal mixture travels a consid-
erable distance thus providing sufficient time for complete combustion [Fig. 4.29(a)].
- Short Flame Burner (Turbulent Burner). It is shown in Fig. 4.29(b). The burner is fitted in
the furnace will and the flame enters the furnace horizontally.
- Tangential Burner. A tangential burner is shown in Fig. 4.29(c). In this system one burner is
fitted attach corner of the furnace. The inclination of the burner is so made that the flame produced are
tangential to an imaginary circle at the centre.
- Cyclone Burner. It is shown in Fig. 4.29(d). This burner uses crushed coal intend of pulver-
ised coal. Its advantages are as follows :
Coal and Primary
Air
Secondary
Air
Coal and Primary
Air
Secondary
Air
(a)(b)
