Chemistry – Inorganic chemistry | e-Consult

The combustion of fossil fuels (coal, oil, and gas) that contain sulfur releases sulfur dioxide (SO₂) into the atmosphere. SO₂ is a major air pollutant with significant environmental impacts.

Acid Rain: SO₂ reacts with water in the atmosphere to form sulfurous acid (H₂SO₃), which then further reacts to form sulfuric acid (H₂SO₄). This sulfuric acid is a major component of acid rain. Acid rain damages forests, acidifies lakes and streams, harming aquatic life, and corrodes buildings and monuments.

Respiratory Problems: SO₂ is a respiratory irritant. Inhaling SO₂ can worsen respiratory conditions like asthma and bronchitis, and can also cause respiratory problems in healthy individuals.

Visibility Reduction: SO₂ can contribute to haze and reduced visibility, impacting transportation and tourism.

Two methods to reduce SO₂ emissions from power plants are:

1. Flue Gas Desulfurization (FGD): This method involves using a chemical process to remove SO₂ from the flue gases before they are released into the atmosphere. Typically, a wet scrubbing process is used, where the flue gas is passed through a spray of alkaline substances, such as lime (calcium oxide) or limestone (calcium carbonate). The SO₂ reacts with the alkaline substance to form calcium sulfite or calcium sulfate, which can then be collected as a solid waste product. The principle is based on the chemical reaction of SO₂ with a base to form a less harmful compound.

2. Using Sulfur-Free or Low-Sulfur Fuels: This involves switching to fuels with lower sulfur content, such as low-sulfur coal or using natural gas as a fuel source. Natural gas contains very little sulfur. This directly reduces the amount of SO₂ produced during combustion. The principle is simple: less sulfur in the fuel means less SO₂ is released.