Exam Question

### (a) The Mechanism of Combustion and Factors for Good Combustion (6 Marks)
The mechanism of combustion in a boiler furnace is a controlled, continuous, exothermic chemical reaction where the chemical energy stored in fuel oil is converted into thermal energy. This process involves several sequential stages:
1. **Atomisation:** The fuel oil, after being heated to the correct viscosity and pressurised, is forced through a specially designed burner/atomizer. This breaks the liquid fuel into a fine mist of millions of tiny droplets, drastically increasing the surface-area-to-volume ratio, which is essential for rapid vaporisation and mixing with air.
2. **Vaporisation:** As the atomized fuel droplets are sprayed into the hot furnace, they absorb radiant heat from the refractory and the existing flame. This heat causes the droplets to vaporize, changing their state from liquid to a combustible gas.