World Wide Coal Combustion Products Network


Glossary of terms

Fly ash

The finer ash produced in a coal fired power station, which is collected using electro-static precipatators. Sometimes spelt as 'fly ash'. This is also know as Pulverised Fuel Ash (PFA) is some countries. About 85% of the ash produced is fly ash.

Furnace Bottom Ash (FBA)

The coarse ash that falls to the bottom of a furnace. The molten ash adheres to the boiler tubes, eventually falling to the base of the furnace. In many furnaces there is a water system that rapdily cools this ash, so called 'wet bottomed' furnace. Usually <15% of the ash produced is FBA.


Hollow ash particles that form in the furnace gas stream. Sometime these particles will contain smaller ash spheres. They float on water and are usually collected from lagoons, where ash/water disposal systems are being used. Only 1 to 2% of the ash produced are cenospheres and with the reduction in ash/water transportation, fewer are collected/available.

Conditioned ash

Where fly ash is mixed with a proportion of water (10 to 20% by dry mass typically) in order that it can be transported in normal tipping vehicles without problems with dust for sale or disposal.

Flue Gas De-sulfurisation

Where a source of Calcium is injected into the furnace gas stream to remove sulfur compounds. A typical system may consist of ground limestone in water being passed through the gas stream. The sulfur compounds convert the calcium carbonate to calcium sulfate, or gypsum, which is used in the wallboard industry for general construction.

Abbreviations & explanation

ACAA American Coal Ash Association.
See for more information.
ADAA Ash Development Association of Australia
BOFA Boosted Over Fire Air – a way of reducing NOx emissions from a power station.
BSI British Standards Institute
CEN European Committee for Standardisation or Comité Européen de Normalisation – the European standards body
CIRCA Canada Industries Recycling Coal Ash
ECOBA European Coal Combustion Products Association e.V. See for more information.
FABM Fly Ash Bound Mixture as used in the EU.
FGD Flue Gas Desulfurisation
HBM Hydraulically Bound Mixtures – same as FABM, but not necessarily containing any fly ash!
JCOAL Japan Carbon Frontier Organisation
KPI Key Performance Indicators. Now associated with environmental and sustainability factors, but can be associated with any measurable parameter.
LOI Loss On Ignition – the measure of unburnt or partially burnt coal within an ash sample.
NCAB National Coal Ash Board - Israel
REACH Registration, Evaluation and Authorisation of Chemicals, the EU registration system for 'substances/chemicals'.
SOFA Separated Over Fire Air – a way of reducing NOx emissions from a power station.
UKQAA The United Kingdom Quality Ash Association
UPS Polish CCP Union

The ACAA produced in 2003 a more detailed glossary which you can download here.