Flue Gas Desulphurisation (FGD)

Source: TH

Context: A study commissioned by the Office of the Principal Scientific Adviser has recommended rolling back the 2015 order mandating Flue Gas Desulphurisation (FGD) installation across all coal plants.

About Recent Study and Its Outcome:

• Key Recommendation: FGD installation should be mandated only for plants burning imported or high-sulphur coal (>0.5% sulfur content), not for all coal plants.

• Findings: 92% of Indian coal is low-sulphur (0.3–0.5%). Stack heights and climatic conditions in India naturally disperse SO₂ emissions, limiting local air quality threats. Full FGD rollout would consume significant freshwater and add 69 million tonnes of CO₂ emissions by 2030 while marginally reducing SO₂. Acid rain is not a major environmental issue in India as per IIT Delhi’s 2024 study.

• 92% of Indian coal is low-sulphur (0.3–0.5%).

• Stack heights and climatic conditions in India naturally disperse SO₂ emissions, limiting local air quality threats.

• Full FGD rollout would consume significant freshwater and add 69 million tonnes of CO₂ emissions by 2030 while marginally reducing SO₂.

• Acid rain is not a major environmental issue in India as per IIT Delhi’s 2024 study.

Note: This study report can be used to justify arguments in the UPSC Mains exam. It is not particularly important for the Prelims examination.

About Flue Gas Desulphurisation (FGD):

• What is FGD?

• A process used to remove sulphur dioxide (SO₂) from exhaust flue gases of fossil fuel power plants, mainly coal-fired stations, improving air quality.

• Introduction in India: Introduced via Ministry of Environment’s 2015 notification requiring all thermal plants to install FGD units by 2018 (now delayed to 2027-29 in phases).

• Types of FGD:

• Once-through (Non-regenerable): Sorbent is disposed of after use, sometimes as by-products like gypsum. Regenerable: Sorbent is regenerated, producing useful products like elemental sulphur or sulfuric acid.

• Once-through (Non-regenerable): Sorbent is disposed of after use, sometimes as by-products like gypsum.

• Regenerable: Sorbent is regenerated, producing useful products like elemental sulphur or sulfuric acid.

• How it Works?

• Flue gases are treated with an absorbent (like limestone slurry) that reacts with SO₂, forming by-products such as gypsum. Pre-treatment with electrostatic precipitators and denitrification units removes ash and nitrogen oxides.

• Flue gases are treated with an absorbent (like limestone slurry) that reacts with SO₂, forming by-products such as gypsum.

• Pre-treatment with electrostatic precipitators and denitrification units removes ash and nitrogen oxides.

• Key Features:

• Removes up to 95% of sulphur dioxide. Improves air quality, limiting acid rain and respiratory illnesses. FGD gypsum can be reused in construction (cement, plaster).

• Removes up to 95% of sulphur dioxide.

• Improves air quality, limiting acid rain and respiratory illnesses.

• FGD gypsum can be reused in construction (cement, plaster).

• Limitations:

• High Cost: Approx ₹1.2 crore per MW installation. Water Usage: Increases freshwater dependency. Energy Consumption: Reduces plant efficiency and raises operational CO₂ emissions. Waste Management: Disposal of FGD by-products needs careful handling.

• High Cost: Approx ₹1.2 crore per MW installation.

• Water Usage: Increases freshwater dependency.

• Energy Consumption: Reduces plant efficiency and raises operational CO₂ emissions.

• Waste Management: Disposal of FGD by-products needs careful handling.