To effectively reduce sulphur oxides in flue gas, which method is most appropriate?

The most appropriate method for effectively reducing sulfur oxides (SOx) in flue gas is scrubbing the flue gas with lime or limestone. This process involves using a slurry of lime or limestone in a scrubber system, where the flue gases are brought into contact with the alkaline solution. The chemical reaction between the sulfur oxides and the alkaline material leads to the formation of inert compounds, primarily calcium sulfate, which can be safely disposed of or utilized in other applications.

This method is particularly effective because it not only reduces the concentration of sulfur oxides before they are released into the atmosphere but also allows for the removal of other acid gases, enhancing overall emission control. The use of lime or limestone as a scrubbing agent is widely recognized in industrial applications, especially in power generation and other energy-related sectors, for its cost-effectiveness and proven efficiency in reducing SOx emissions.

The other methods mentioned have their relevance but do not target sulfur oxides as directly or effectively as scrubbing with lime or limestone. Staged combustion can help reduce overall emissions by minimizing the formation of nitrogen oxides (NOx), while reducing excess air can improve combustion efficiency but may not significantly impact sulfur oxides. Lowering the furnace temperature might reduce some emissions but