What process must occur for solid or liquid fuels to combust effectively?

For solid or liquid fuels to combust effectively, they must vaporize. Combustion is a chemical reaction that requires a fuel to mix with an oxidizer, typically oxygen from the air, and this reaction often occurs in the gaseous phase.

In the case of solid or liquid fuels, they initially need to transform into a vapor to facilitate this mixing. For example, in solid fuels like coal or wood, the combustion process begins with pyrolysis, where heat breaks down the solid fuel into smaller molecules, most of which then vaporize. Similarly, liquid fuels like gasoline or diesel need to vaporize to form a mixture with air that can ignite and sustain combustion.

When a fuel is in its liquid or solid state, it cannot mix effectively with the oxygen needed for combustion until it vaporizes. Thus, vaporization is a critical step for ensuring that the fuel can participate in the combustion reaction, releasing energy and producing combustion products such as carbon dioxide and water.