Bottom ash

Overview of bottom ash in power plants

Bottom Ash

Intermountain Power Plant, Utah, where bottom ash is produced.

Bottom ash is a byproduct of the combustion of coal in thermal power plants. It is the non-combustible residue that falls to the bottom of the furnace during the burning process. Unlike fly ash, which is carried out of the furnace with the flue gases, bottom ash is collected at the bottom of the boiler.

Composition and Characteristics

Bottom ash is typically composed of a variety of materials, including unburned carbon, silica, alumina, and iron oxide. The specific composition can vary depending on the type of coal used and the combustion process. Bottom ash is generally coarse and granular, with a texture similar to sand or gravel.

Collection and Handling

In a power plant, bottom ash is collected in a water-filled hopper located at the bottom of the furnace. The ash is then removed from the hopper and transported to a disposal site or processing facility. Handling of bottom ash requires careful management to prevent environmental contamination and to ensure safe disposal.

Uses of Bottom Ash

Bottom ash can be used in a variety of applications, including:

• Construction aggregate: It can be used as a substitute for sand and gravel in construction projects.
• Cement production: Bottom ash can be used as a raw material in the manufacture of cement.
• Landfill cover: It can be used as a daily cover material in landfills to reduce odor and pest problems.

Environmental Concerns

The disposal and management of bottom ash pose several environmental challenges. If not properly managed, bottom ash can leach heavy metals and other contaminants into the soil and groundwater. Therefore, regulations often require that bottom ash be disposed of in lined landfills or used in applications that minimize environmental impact.

Related Pages

• Fly ash
• Coal combustion products
• Thermal power station
• Environmental impact of coal