Q1: The main function of the deaerator used in the thermal power plant is to

ANS:C - remove dissolved gases from feed-water.

1. Throttle down the steam pressure: Throttling down steam pressure refers to the reduction of steam pressure in the steam distribution system. This process is typically achieved using control valves or other devices that regulate the flow of steam. However, the main function of a deaerator is not to throttle down steam pressure. Instead, a deaerator is primarily designed to address issues related to feed water quality before it enters the boiler system.
2. Enhance feed water temperature: While some deaerators may have the capability to slightly increase the temperature of the feed water, this is not their main function. The primary purpose of a deaerator is to remove dissolved gases from the feed water. Enhancing feed water temperature may be a secondary benefit of the deaeration process, as heating the feed water can help in the removal of dissolved gases, but it is not the primary goal.
3. Remove dissolved gases from feed-water: This is the correct function of a deaerator. Dissolved gases such as oxygen and carbon dioxide in the feed water can cause corrosion and other problems in the boiler and steam system. The deaerator removes these dissolved gases by preheating the feed water and then mechanically removing the gases through the process of steam stripping or vacuum extraction. This helps prevent corrosion and ensures the proper functioning and longevity of the boiler system.
4. Remove non-condensable gases from condenser: While removing non-condensable gases from the condenser is important for maintaining proper vacuum levels and preventing air ingress into the condenser, this is not the function of a deaerator. Non-condensable gases are typically removed from the condenser using vacuum pumps or air extraction systems. The primary role of a deaerator is to address issues related to feed water quality, not to remove gases from the condenser.

In summary, while each of these functions may be important in the operation of a thermal power plant, the main function of a deaerator is to remove dissolved gases from feed-water to prevent corrosion and ensure the proper functioning of the boiler system.