flygaska

Flygaska, or fly ash, is a fine particulate byproduct formed when coal and other fossil fuels are combusted in power plants and industrial furnaces. The particles are carried in the flue gas and are captured by emission control devices such as electrostatic precipitators or fabric filters before the gas is released to the atmosphere.

Composition varies with fuel and combustion conditions. Typical constituents include silica, alumina, calcium oxide, iron oxides, and trace metals. Particle sizes commonly range from submicrometers to tens of micrometers. Fly ash often has pozzolanic properties, which allows it to react with calcium hydroxide in cement.

Fly ash is widely used as a supplementary cementitious material in concrete and cement production, helping improve workability, strength, and durability while reducing cement demand. It is also used in concrete blocks, roadbed material, and mine backfill. In many jurisdictions, its use is subject to standards and leaching tests to ensure environmental safety.

Because fly ash can contain trace amounts of heavy metals and other contaminants, handling and disposal are regulated. Facilities collect a large portion of produced fly ash for reuse, with remaining material placed in landfills or used for fill, subject to environmental permits and monitoring. Ongoing research seeks to optimize beneficial use and minimize risks.

Terminology: In Swedish, flygaska is the term for fly ash; it is a byproduct of thermal power generation and is distinct from bottom ash, which remains at the furnace bottom.