Activated carbon is a highly versatile absorbent material that is widely used for abatement processes. In the waste industry it is often used in treatment of odours or entrapment of volatile organic compounds (VOCs). Typically enclosed within a filter cartridge with a porous paper or fabric material the vapours are drawn through the filter to remove VOCs or odorous gases in the air stream.
Activated carbon has a very open surface structure with fine channels running through it. This provides a very large active surface area. The VOCs and odorous organic compounds are attracted to the surface of the carbon which traps the compound within the carbon structure. The carbon remains active and removes the compounds efficiently until nearly all the carbon surface and cavities are saturated with compound. This is like a sponge soaking up water. Once saturated the carbon needs to be replaced.
The activated carbon has the advantage that it can be regenerated. The saturated carbon can be heat treated in an oxygen free environment at a high temperature. This boils off the volatile compounds from the surfaces and because there is no oxygen in the atmosphere neither the gases nor the carbon gets burnt. Boiling off the volatile compounds regenerates the activity of the carbon and allows it to be re-used as absorbent.
The gases which are evaporated from the carbon (off gasses) can then be treated using various techniques: -
- Solvent recovery
In cases where solvents have been absorbed in the carbon the solvent vapours can be chilled and condensed to recover the wet solvents. This would only be used if there were large volumes of valuable solvents being collected on a regular basis.
- High calorific vapours
Small quantities of flammable vapours can be directed into the fuel input of a boiler where burning of the vapours can supplement the energy generation of the boiler at the same time as destroying the vapours.
- Vapour destruction
Some vapours have little calorific value but still need to be treated to eliminate the odorous or toxic qualities of the vapours. This can be done by chemical treatment or by injecting into a high temperature oxygen rich environment where the temperature and oxygen break down the vapours and destroy them.
Carbon filters are often used to deodorise Anaerobic Digestion plants. The odours from incoming food wastes, which have started fermenting or rotting, are drawn through the carbon filters to absorb the odorous vapours. These filters are usually built into industrial building extraction units which stop the odours from escaping to the surrounding area.
They are similarly used on in-building compost facilities.
They are also used in paint spray booths. The residual solvent vapours from the paint spraying process are trapped in the carbon reducing the potential escape of solvents into the atmosphere.
Carbon filters are also used in water systems to help remove contaminants from the water.
The market for activated carbon is predicted to continue to grow with increased usage in the water supply business, odour management from water treatment plants and waste facilities. Consumption of activated carbon may increase by up to 20% over the next 20 years.
If you need help with odour management or require an Odour Management Plan then we are able to help. If you would like us to help you with odour related problems then please contact us:- www.wasteplansolutions.co.uk , email [email protected] , or call 01604 859961.