Flue Gas Desulphurisation (FGD)

Flue Gas Desulphurisation Latest News

A recent study commissioned by the Principal Scientific Adviser said that the Union Environment Ministry should roll back its 2015 policy mandating all of India’s 537 coal-fired plants to install a class of equipment called Flue Gas Desulphurisation (FGD).

About Flue Gas Desulphurisation

• In an FGD system, sulphur compounds, particularly sulfur dioxide (SO2), are removed from the exhaust emissions of fossil-fuelled power stations. 
• This is done by means of an industrial process through the addition of absorbents. This can remove up to 95 % of the sulphur dioxide from the flue gas (exhaust gas).
• The wet process has become the main method of FGD in large, fossil-fuelled power plants. 
• In this method, the flue gases are steam-saturated with the absorbent in aqueous solution. 
• Substances such as ammonia or sodium sulphite are used as absorbents; however, the use of lime or limestone slurry (wet limestone scrubbing) is also widespread. 
• The uncleaned flue gas is sprayed in a scrubber tower (absorber tower) with a mixture of water and limestone (scrubbing slurry), whereby most of the sulphur dioxide is bonded by chemical reaction.

Why Do We Need Flue Gas Desulphurisation (FGD)?

• Most fossil fuels (coal, oils, etc.) contain some sulphur. 
• When a fossil fuel is burnt, the sulphur it contains is released to the atmosphere via the process of combustion. 
• Some coals may contain up to 4% sulphur, which is a significant amount considering that a coal power station may burn in excess of 5,000 tonnes of coal per day.
• Sulfur dioxide in itself is a major air pollutant which impacts all life. 
• It is also a precursor of acid rain, which has significant adverse impacts on forests, freshwaters, and soils, in turn killing insect and aquatic life forms, causing paint to peel, corrosion of steel structures such as bridges, and weathering of stone buildings and statues.
• The removal of sulfur dioxide is critical to establishing a safe and clean environment where toxic emissions are kept to a safe level.

Source: TH