Bottom ash refers to the non-combustible constituents of coal with traces of combustibles embedded in forming clinkers and sticking to hot side walls of furnace during the furnace working. The portion of the ash that escapes up the chimney or stack is, however, referred to as fly ash. The clinkers fall by themselves into the water or sometimes by poking manually, and get cooled.

The clinker lumps get crushed to small sizes by clinker grinders mounted under water and fall down into a trough from where a water ejector takes them out to a sump. From there it is pumped out by suitable rotary pumps to dumping yard far away. In another arrangement a continuous link chain scrapes out the clinkers from under water and feeds them to clinker grinders outside the bottom ash hopper.

Bottom ash may be used as an aggregate in road construction and concrete, where it is known as furnace bottom ash (FBA), to distinguish it from incinerator bottom ash (IBA), the non-combustible elements remaining after incineration. It was also used in the making of the concrete blocks used to construct many high-rise flats in London in the 1960s

See also

• Fly-ash

External links

• EcoSmart Concrete : A site dedicated to the use of Fly ash and other supplementary cementing materials in concrete.