Which are the two main types of ash in coal-fired plants?

• A. Fly ash and bottom ash.
• B. Coal ash and ash slurry.
• C. Volatile ash and fixed ash.
• D. Fine ash and coarse ash.

Answer: (A)

Two main types of ash in coal-fired plants are fly ash and bottom ash. When coal burns, the mineral matter splits by size. The fine particles become fly ash, which stays suspended in the flue gas and is captured by particulate control equipment like electrostatic precipitators or fabric filters before the gas goes to the stack. The larger, heavier portion settles to the bottom of the boiler and is removed through the bottom ash system. Fly ash is typically a fine powder and often requires collection and handling for emission control and potential reuse, while bottom ash is coarser and handled separately, sometimes used as aggregate after processing. Other described terms don’t align with the standard plant classifications for ash produced during combustion.