What effect does maintaining gases above dew point have on air heaters?

Maintaining gases above the dew point is crucial for preventing corrosion within air heaters and other components of a heating system. When gases cool and fall below the dew point, moisture can condense and form water droplets. This moisture combines with other constituents in the flue gases, such as sulfur oxides and nitrogen oxides, which can lead to the production of acidic solutions. These acids are highly corrosive and can significantly damage the materials of the air heater, leading to costly repairs and reducing the lifespan of the equipment.

By ensuring that the gases remain above the dew point, the condensation of water is avoided, which helps to maintain the integrity of the air heater and extends its operational lifetime. In addition to preserving equipment, this practice can improve overall system reliability and reduce maintenance needs, translating into operational cost savings.

While the other choices have their own relevance in different contexts, the primary effect of maintaining gases above the dew point focuses on the prevention of corrosion, which is a critical consideration in the operation and maintenance of air heaters.