Developments in FGD
AUTHOR: Hermine N Soud
DATE: March 2000
Flue gas desulphurisation (FGD) is the principal method of controlling SO2 emissions from utility size pulverised coal combustion. On smaller plants, and where by-product disposal is not an issue, furnace sorbent injection with limestone followed by spray dry scrubbing can achieve very high removal efficiencies and does not entail the high costs involved in using lime as a sorbent. In such a configuration, the technology can be applied at facilities firing higher sulphur coals than can be used when these systems are applied individually. Combining duct sorbent injection with fabric filters is also an attractive option with smaller and older plants.
Development continues to aggregate the removal of several air pollutants including SO2, NOx, fine particulate matter and trace elements (especially mercury) in a single process. However, for new and large power stations, where a larger amount of by-product is generated, the usual choice continues to be wet scrubber technology to control SO2 emissions. Capital costs have reduced greatly over the last three decades. Operating and maintenance costs of wet scrubbers have always been competitive with all the other technologies. This is due to the high removal efficiencies achieved, availability and cost of the limestone sorbent and sale of the system by-products. They are also capable of processing flue gas from different types of coal with high sulphur content.