Describe a chemical method for removing acidic gases from industrial chimney waste. - Leaving Cert Chemistry - Question A - 2016

One effective chemical method for removing acidic gases from industrial chimney waste is known as scrubbing.

Scrubbing Process

Scrubbing involves the use of a scrubbing liquid, typically a solution containing a base, to react with and neutralize the acidic gases present in the exhaust. The most commonly used scrubbing agent is limestone, which is chemically represented as calcium carbonate (CaCO₃).

1. Chemical Reaction: When sulfur dioxide (SO₂) is present in the gas stream, it can react with calcium carbonate to form calcium sulfate (CaSO₄) as follows:

   $$$$

ightarrow ext{CaSO}_3 + ext{CO}_2$$

This reaction indicates that the calcium carbonate reacts with sulfur dioxide to produce calcium sulfite and carbon dioxide.

2. Further Neutralization: To maximize the effectiveness of this chemical method, the calcium sulfite produced can further oxidize into calcium sulfate. This oxidation can occur naturally or can be facilitated, leading to process efficiency. The step can be represented as:

   $$$$

ightarrow ext{CaSO}_4$$

3. Additional Agents: Alternative scrubbing agents may also include calcium oxide (CaO), hydroxide compounds, and other amines or zeolites that operate through similar neutralization reactions. Each of these compounds contributes to mitigating the acidic components in the chimney waste.

Conclusion

In summary, scrubbing is a reliable chemical technique that utilizes specific agents like calcium carbonate to effectively remove acidic gases, thus reducing harmful emissions from industrial processes.