Coal Combustion Products (CCP)
Coal Combustion Products is the generic term used to describe all residues emanating from the combustion of coal.
The variety of CCPs depend upon:
- combustion technology (pulverised coal, fluidised bed, etc)
- collection technology (bagfilters, electrostatic precipitators)
- treatment of flue gases prior to release (desulphurisation, ammoniation, etc).
Environmental benefits:
Significant environmental benefits accrue when CCPs are used.
- for every ton used to replace cement, the release to the atmosphere of one ton of CO2 , a greenhouse gas, is avoided
- incorporation in soil to improve fertility
- pasteurisation of sewage sludge
- immobilisation of toxic elements
- counteracting acid mine drainage
- rehabilitation of minespoil and slimes dams
- backfilling of mines to prevent subsidence
Given South Africa’s abundant coal resources, large quantities of CCPs are produced both in the generation of electricity (ESKOM) and the production of liquid fuel (SASOL).
Description: Eskom utilises pulverised coal combustion to fire their boilers. This creates fly ash, a fine powdery residue collected from either electrostatic precipitators or bagfilters, prior to releasing the flue gases to the atmosphere.
Uses & benefits:
Building and construction industry Fly ash is widely applied where it is used as a cement extender (blended cements) or an ingredient in its own right in concrete (supplementary cementitious material).
Advantages in concrete:
- enhanced workability (less water)
- improved durability
- reduced heat of hydration
- reduced alkali-silica reaction
- reduced shrinkage
- reduced sulphate attack
Polymer industry
- fly ash can be used as a functional filler in plastics and rubber. Its particle shape aids processing and reduces the amount of polymer required.
Description: A sand-like product removed from the base of a pulverised fuel boiler.
Uses & benefits:
- A feedstock for the production of cement clinker and as an aggregate for the manufacture of concrete masonry units (bricks and blocks).
This product is generated when using large lumps of coal when firing a grate furnace.
Description: SASOL produces a coarse clinker-like ash during the gasification of coal for the production of liquid fuels.
Uses & benefits:
- Used in the manufacture of bricks and blocks.
Description: A fluidised bed ash arises when combustion is achieved by means of fluidisation of the coal.
Uses & benefits:
- Widely used internationally but not currently available in South Africa.
Fluidised Gas Desulphurisation (FGD) product
Description: The alkaline scrubbing of exhaust gases to remove SO2 gives rise to an FGD gypsum product.
Uses & benefits:
- The FGD Gypsum is used for wallboard (gypsum board) manufacture, as a set regulator for cement and in agriculture as a soil enhancer.
