Prerequisites for proper combustion in boiler furnace

Proper combustion requires an adequate supply of air (fuel-air ratio) and good atomization of the supplied fuel.

1. Air supply

The fan, damper, register, swirler vanes and (vortice) plates, and quarl designed to supply the correct quantity of air for efficient combustion suitably agitated to allow proper mixing.
The air is generally heated on larger plant to:
- prevent thermal shocking
- improve the combustion process
- improve plant efficiency (bled steam and regenerative)

2. Fuel

It is important that fuel properly prepared: filtered and preheated (in case of HFO) for proper combustion. Fuel preparation is essential for proper atomizing. The burner giving fuel some axial (for penetration) and angular (for mixing) velocity. For effective atomization the viscosity of the fuel is critical, for fuels heavier than gas or diesel oils some degree of heating is required. It should be noted that the temperature of the fuel should not be allowed to raise too high as this can not only cause problem with fuel booster pumps but also can cause flame instability due to premature excessive gasification. The smaller the droplet size the greater the surface areas/volume ratio is, this increases evaporation, heating and combustion rate.