Semi-Dry Flue Gas Desulphurisation (FGD) is used for removing sulphur dioxide (SO2) from the exhaust flue gas in Coal- and Oil-Fired Power Plants and Large Scale Waste Incineration Plants. In this process a single rotary atomiser centred in the top of the absorber vessel (SDA - Spray Dryer Absorber) distributes and atomises the reagent which is constituted of Lime Slurry. Also the flue gas enters from the top and therefore the system can be defined as a top-entry co-current flow.
This process can achieve reduction between 80% and 90% and therefore it is used for relatively small
to medium size boilers using low to medium sulphur coal (1,5%).

The chemical process between and hydrated lime can be simplified as follows:








One of the advantages of this process is that, if compared with Wet FGD, the waste water treatment system is not necessary,  since water is completely evaporated in the absorber.

Although this process is called desulphurisation, it is important to highlight that there is a very high efficiency also on other pollutants like HCl.

Termokimik applies this process from Waste-to-Energy Plants to Utility Boilers rated up to 600 MW.
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