Flue gas desulfurization can be classified into the following six main categories:
- wet scrubbers
- spray dry scrubbers
- sorbent injection processes
- dry scrubbers
- regenerable systems
- combined SO2/NOx removal processes
FGD units are installed in 27 countries. Planned FGD installations are subject to uncertainty; especially where they are intended for new coal-fired plants which may be delayed or deferred depending on market conditions.
Wet scrubbers take the lead followed by spray dry scrubbers and sorbent injection systems in the FGD market throughout the world. Regenerable and combined SO2/NOx processes have a small share and the trend is not expected to change in the short-term according to current plans for new FGD installations. New developments in sorbent injection technologies are in progress and this type of FGD is expected to become more widely used in older coal-fired plants.
The summarised description of the technologies on this website is mainly drawn from the detailed IEA Coal Research reviews on FGD technologies (including low cost retrofit options), installations, and performance and experience by Fukasawa (1997), Soud (1994), Soud and Takeshita (1994) and Takeshita and Soud (1993).