Trace elements and fly ash utilisation (Sloss, 03-2007)

Many trace elements such as chromium and mercury are toxic. The leaching of trace elements from fly ash is usually monitored at ash storage and disposal sites to ensure that they do not leak into the natural environment at elevated concentrations. Preparatory studies are commonly carried out to ensure that the use of fly ash and other coal by-products in agricultural applications such as soil amendment and landfill do not lead to contamination of soil or groundwater. The concentrations of chromium and radioactive trace elements are also limited in cement and concrete applications as a result of recently tightened legislation. Coal fly ash can be the major source of chromium and radioactivity in these applications.

This report draws together data on the concentrations of trace elements in fly ash from both conventional and advanced coal-fired power plants. It examines and evaluates the analytical techniques required to determine the concentrations of trace element species in fly ash and to predict their behaviour in applications such as cement and concrete. The legislated limits for trace elements in fly ash for use in the construction industry and other applications are summarised.

The report examines the variation in trace element partitioning with different furnace technologies and pollution control systems. New and emerging technologies to reduce emissions of pollutants such as mercury and fine particulates will affect the trace element concentration of ash. The report summarises how these changes may affect the marketing potential of the ash produced.