Bottom ash is part of the non-combustible residue of combustion in a power plant, boiler, furnace or incinerator. In an industrial context, it has traditionally referred to coal combustion and comprises traces of combustibles embedded in forming clinkers and sticking to hot side

walls of a coal-burning furnace during its operation. 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 bottom hopper of a coal-burning furnace and are cooled. The above portion of the ash is

is also referred to as bottom ash.
Most bottom ash generated at U.S. power plants is stored in ash ponds, which can cause serious environmental damage if there are structural failures of the ponds.
In a conventional water impounded hopper (WIH) system, the clinker lumps get crush

ed 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. In another arrangement a continuous link chain scrapes out the clinkers from under wate