Fly ash is comprised of fine or low density particles carried from the boiler in the flue gas stream. It is removed from the flue gas by electrostatic precipitators or bag houses.

Depending on the coal and unit characteristics, fly ash can be 70% to 90% of total ash production. Most older coal units were constructed with wet sluice systems to transport fly ash to unlined storage ponds or impoundments.

Some of these plants have been converted to dry fly ash systems as ponds filled up and needed replacement. Evolving groundwater regulations and markets for the sale of fly ash encouraged this process. Other plants converted wet ash handling systems to dry as part of FGD projects.

More detail on this topic is in a white paper by River Consulting. To find out more, click here.