Flue Gas Desulphurization (FGD)
Context: A high-powered committee chaired by Principal Scientific Advisor (PSA) Ajay Sood has proposed that India should discontinue the mandatory use of Flue Gas Desulphurisation (FGD) units in most coal-fired Thermal Power Plants (TPPs).
Important Pointers:
Definition: Flue Gas Desulphurisation (FGD) is a technology used to remove sulphur compounds, especially sulphur dioxide (SO₂), from exhaust emissions of power plants and industries.
FGD Efficiency: FGD systems can eliminate up to 95% of SO₂ from flue gases through chemical absorption processes.
Absorbents Used: Common absorbents include ammonia, sodium sulphite, and more widely, lime or limestone slurry (CaCO₃-based).
FGD Process Setup: In wet limestone scrubbing, unclean flue gas is sprayed in an absorber (scrubber) tower with a mixture of water and limestone.
Chemical Reaction: SO₂ in the gas reacts with the scrubbing slurry to form calcium sulphite or gypsum, thus reducing emissions effectively.