ANS:C - release of non-condensable gas from water in the boiler.

The release of non-condensable gases from water in the boiler refers to the presence and subsequent release of gases that do not condense into liquid form at the operating conditions of the boiler. These non-condensable gases, such as oxygen, nitrogen, and carbon dioxide, can dissolve in water under certain conditions and are often present in the feedwater supplied to the boiler. When water is heated in the boiler, especially in areas where high temperatures are reached, these dissolved gases tend to be released from the water and accumulate in the steam phase. The presence of non-condensable gases in the steam can lead to several problems:

1. Corrosion: Non-condensable gases, particularly oxygen, can accelerate the corrosion of metal surfaces within the boiler and associated components. Oxygen can react with the metal to form oxides, leading to the degradation of boiler tubes, drums, and other equipment.
2. Reduced Efficiency: Non-condensable gases can decrease the efficiency of heat transfer in the boiler. They form insulating layers on heat transfer surfaces, reducing the effectiveness of heat exchange and increasing fuel consumption.
3. Steam Quality: The presence of non-condensable gases in steam affects its quality. High concentrations of non-condensable gases can lead to wet steam, which may cause damage to turbines, reduce turbine efficiency, and compromise the performance of steam-driven equipment.

To mitigate the effects of non-condensable gases, boiler operators often employ strategies such as proper deaeration of feedwater, chemical treatments to scavenge oxygen, and periodic purging of accumulated gases from the boiler system. These measures help maintain efficient boiler operation and prolong the lifespan of boiler components.