Coal Combustion Products

Coal Combustion By-Products (CCBs) are the incombustible inorganic matter in coal that is leftover after the burning process. These materials produced primarily from the combustion of coal in coal-fired power plants. These by-products include:

Fly ashBottom ashBoiler slagFlue gas desulphurisation gypsum

Coal combustion products (CCPs) can play an important role in concrete production. The characteristics and physical properties of CCRs vary. In general, the size, shape, and chemical composition of these materials determines their beneficial reuse as a component of building materials or as a replacement for other virgin materials such as sand, gravel, or gypsum.

1. Fly Ash: (60 percent of all coal combustion waste)

Fly ash is comprised of tiny particles removed from our flue gas by emissions control devices.

Fly ash can be used to replace or supplement cement in concrete. It produces a concrete that is strong and durable, with resistance to corrosion, alkali-aggregate expansion, sulphate and other forms of chemical attack.

Among the most significant environmental benefits of using fly ash over conventional cement is that greenhouse gas (GHG) emissions can be significantly reduced.

Fly ash also serves as filler in wood and plastic products, paints and metal castings.

2. Bottom Ash: (12 percent of all coal combustion waste)

Bottom ash is made up of larger particles, such as sand and small rocks within the coal, collected in the bottoms of boilers.

Bottom ash is used to manufacture cement or to replace native materials in landfill construction.

3. Flue-gas Desulfurization Gypsum : (24 percent of all coal combustion waste)

Flue-gas desulfurization (FGD) materials  are produced by chemical “scrubber” emission control systems that remove sulfur and oxides from power plant flue gas streams.

FGD gypsum is used in agricultural applications to treat undesirable soil conditions and to improve crop performance.

FGD materials are used in mining and land reclamation activities.

4. Boiler Slag:  (4 percent of all coal combustion waste)

These molten ash collected at the base of furnaces that is quenched with water and shatters into smooth, glassy black particles. It is a by-product produced from a wet-bottom boiler.

It can be used as a raw feed for manufacturing portland cement clinker, as well as for skid control on icy roads.

Boiler slag is also used for roofing granules and as blasting grit.