Flue Gas Desulphurisation (FGD) is the state-of-the art technology used for removing sulfur dioxide (SO2) from the exhaust flue gas in Coal and Oil Fired Power Plants. In the so called "wet limestone-gypsum" process, an aqueous slurry of finely ground limestone is introduced into an absorber and put in intimate contact with the
flue gas containing . This process can achieve reduction efficiencies up to 99% and therefore is almost
the only possibility for medium to high sulphur content coal.

The chemical reactions that take place inside the absorber, which consists of an open spay tower with a recycle tank, can be summarised as follows:



Multiple spray stages with dedicated pumps provide efficient absorption.The recycle sump is equipped with
side-mounted agitators which are specially designed for homogeneous suspension of solids. Oxidation air sparging is achieved through a dedicated network of pipes injecting air in proximity of agitators impellers in order to give uniform dispersion of humidified oxidation air.  


Fresh limestone suspension is fed into the absorber sump in order to maintain the desired slurry pH. A proportionate amount is withdrawn from the tank as gypsum-produced slurry.

A simplified block diagram of the Wet FGD Process is shown in the following picture.

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

The advanced automation, the excellent reliability and the saleable by-product (gypsum) leads to a moderate operating cost. As a consequence it has become a standard for big size units.

Termokimik has more than 15 years experience in Wet FGD systems, ranging from very small pilot plant up to 600 MW Coal Fired installations.



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