How can nitrogen oxides in flue gases be effectively reduced?

The effective reduction of nitrogen oxides (NOx) in flue gases is best achieved by employing catalysts, which facilitate chemical reactions at lower temperatures, leading to the breakdown of these harmful compounds. Utilizing catalytic converters is a proven method; they contain catalysts that promote the conversion of nitrogen oxides into nitrogen and oxygen.

In this context, option B is not the most effective method because reducing the percentage of air during combustion can lead to incomplete combustion, potentially producing more carbon monoxide and unburned hydrocarbons. In contrast, increasing the combustion temperature, increasing combustion pressure, and using catalytic converters are all methods that can help manage NOx levels. Increasing temperature typically leads to higher NOx formation, while increased combustion pressure may also impact emission levels without the aid of appropriate catalysts. Thus, the best answer emphasizes the use of catalytic converters as a more effective means of reducing nitrogen oxide emissions in flue gases, demonstrating a targeted approach to controlling pollutants in the context of power engineering.