Flue Gas Desulphurisation (FGD) Systems

Recently, the Indian Environment Ministry has made a significant policy change by exempting most coal-fired power plants in the country from the mandatory installation of Flue Gas Desulphurisation (FGD) systems. These systems are intended to reduce sulphur dioxide (SO₂) emissions, a major contributor to air pollution and acid rain.

About Flue Gas Desulphurisation (FGD):

Flue Gas Desulphurisation (FGD) is a technology used to remove sulphur dioxide (SO₂) from the exhaust gases of coal-fired power plants. Since SO₂ is one of the main contributors to acid rain, particulate matter pollution, and various health problems, reducing its emissions is crucial for improving air quality and protecting ecosystems.

The FGD process generally involves the use of substances like:

• Limestone (CaCO₃)

• Lime (CaO)

• Ammonia (NH₃)

These react with SO₂ in the flue gases to neutralize it and form by-products that are less harmful.

Types of FGD Technology:

Several different FGD technologies can be implemented to reduce SO₂ emissions:

1. Dry Sorbent Injection (DSI):

   • Involves injecting limestone or lime into flue gases before they pass through dust collectors.

   • Suitable for certain plant configurations but requires effective dust collection systems.

2. Wet Limestone Scrubbing:

   • Involves the use of a limestone slurry to absorb SO₂, converting it into gypsum (CaSO₄·2H₂O).

   • This is the most commonly used method for large-scale power plants.

3. Seawater FGD:

   • Uses the alkalinity of seawater to neutralize SO₂.

   • Common in coastal plants due to low installation costs, but its use is limited to regions near coastlines.

Recent Policy Changes and Exemption Decision:

India had earlier mandated, through the Environment Ministry, that all coal-fired thermal power plants must install FGD systems by 2017 in order to curb SO₂ emissions. The 2015 mandate required approximately 180 coal-fired plants (comprising 600 units) to comply with the new emission norms.

However, as of now, only about 8% of these plants have installed FGD systems, and the bulk of installations are from NTPC (National Thermal Power Corporation), a public-sector entity. The delay in meeting the deadline has been attributed to several challenges, including:

• Vendor shortages

• High costs of FGD installation

• Delays caused by the COVID-19 pandemic

• Anticipated increase in power tariffs due to the added cost of installing and operating the FGDs.

In light of these challenges, the Environment Ministry recently made a policy exemption for most plants, citing several factors:

• Indian coal has a lower sulphur content compared to coal in many other regions, leading to lower SO₂ emissions.

• SO₂ levels near power plants with and without FGDs have shown to be similar in several studies.

• Some research suggests that sulphates formed from SO₂ emissions may actually have a cooling effect on the atmosphere, potentially mitigating global warming to a small extent.

Implications and Concerns:

While the exemption may seem to alleviate immediate financial and logistical burdens for power plants, it has sparked concern among environmentalists and experts for several reasons:

1. Long-term Environmental Impact:

   • The continued reliance on coal-fired plants without adequate SO₂ control may still lead to severe air quality issues, particularly in densely populated regions.

   • Acid rain from unfiltered SO₂ can have harmful effects on soil, water bodies, agriculture, and human health.

2. Global Climate Commitments:

   • India has made international climate commitments to reduce its carbon intensity and transition toward cleaner energy sources. The exemption from FGD requirements may delay the transition to sustainable energy.

3. Missed Opportunities for Technological Development:

   • The delay in the widespread installation of FGD systems might delay the adoption of advanced pollution control technologies that could create jobs, improve energy efficiency, and contribute to India's green economy.

4. Risk of Undermining National Air Quality Standards:

   • The decision might undermine national efforts to achieve stringent air quality standards, particularly in regions heavily dependent on coal power. This could exacerbate health issues, especially respiratory illnesses.

Conclusion:

The exemption of coal-fired power plants from mandatory installation of Flue Gas Desulphurisation (FGD) systems is a significant shift in India’s environmental policy. While it might offer immediate relief to plants facing financial and logistical challenges, the long-term effects of this decision on air quality, public health, and India's climate commitments remain uncertain.