UPSC CSE Prelims 2011

Correct Option

Coal combustion in thermal power plants releases several gases into the atmosphere:

• Carbon dioxide (CO₂): This gas is a primary product of the complete combustion of carbon present in coal. It is a major greenhouse gas.
• Oxides of nitrogen (NOx): These compounds are formed when nitrogen and oxygen from the air react at the high temperatures achieved during combustion.
• Oxides of sulphur (SOx): The sulphur content naturally present in coal is oxidized during combustion, leading to the emission of sulphur dioxide (SO₂) and sulphur trioxide (SO₃). These contribute to acid rain.

Therefore, all three listed substances are significant emissions from coal combustion at thermal power plants.

Incorrect Options

Options (a), (b), and (c) are incorrect as they do not encompass all the major gaseous emissions resulting from coal combustion in thermal power plants. Coal combustion is a complex process that simultaneously produces carbon dioxide, oxides of nitrogen, and oxides of sulphur, along with other pollutants like particulate matter and heavy metals.