Context: Union Minister for Power and New and Renewable Energy (NRE) RK Singh recently presided over a high-profile meeting to review the results of a study conducted by IIT-Delhi on ambient atmospheric sulphur dioxide (SO2) concentrations and the effect of installing flue gas desulphurisation (FGD) technology on SO2 emissions in various categories of cities, as defined by them.

About FGD Technology

• Flue Gas Desulphurisation technology is essential for removing Sulfur Dioxide (SO2) from exhaust emissions.

• Burning fossil fuels like coal and oil produces flue gas with high SO2 content.

• Approximately 95% of the sulfur in these fuels converts to SO2 during combustion.

• The Ministry of Environment, Forest & Climate Change has mandated FGD systems for all coal-based TPPs. FGD technology is crucial for maintaining a clean and safe environment.

There are three major types of FGD systems used globally:

1. Dry Sorbent Injection: Uses limestone to remove SO2.

2. Wet Limestone Based: Utilizes a slurry of water and limestone.

3. Sea Water Based: Employs sea water for SO2 removal.

FGD systems are highly efficient, capable of removing over 90% of SO2 from flue gas emissions.

FGD Process

• The FGD process involves the use of absorbents to eliminate SO2 from flue gas.

• Common absorbents include ammonia, sodium sulfite, lime, or limestone slurry.

• The process is typically carried out in a scrubber tower (absorber tower).

• The uncleaned flue gas is sprayed with a scrubbing slurry, a mixture of water and limestone.

• A chemical reaction occurs, bonding most of the SO2, effectively removing up to 95% of the sulfur dioxide.

About SO2

• SO2 is a toxic gas produced by burning fossil fuels containing sulfur.

• It is a major air pollutant affecting human health and the environment.

• It is a precursor to acid rain, which damages forests, freshwater, soils, insects, aquatic life, and man-made structures.

Environmental and Health Implications

• Acid rain, resulting from SO2, leads to the corrosion of steel structures such as bridges and the weathering of stone buildings and statues.

• SO2 is also detrimental to human health, primarily affecting the respiratory system.