Electrical Engineering XYZ MCQs
In a steam power plant, the feed water coming to the economizer is heated plant the feed water coming to the economizer is heated using;1
- LP steam
- HP steam
- Direct heat in the furnace
- Flue gas
Correct answer: 4. Flue gas
Explanation: In a steam power plant, an economizer is a heat exchanger device that preheats water before it enters the boiler. The primary purpose of the economizer is to improve the efficiency of the steam generation process by utilizing waste heat from the flue gases that exit the boiler.
When fuel is burned in the furnace of a boiler, it releases heat energy, which heats up water to produce steam. However, not all of the heat energy from the fuel combustion is converted into useful work; some of it is lost with the hot flue gases that exit through the chimney.
The economizer is placed in the path of these hot flue gases. As the flue gases pass through the economizer, they transfer some of their heat energy to the water flowing through the economizer tubes. This preheated water then enters the boiler where it requires less additional heat to reach the desired steam temperature and pressure.
So, the feed water coming to the economizer is heated using the waste heat from the flue gases, making “Flue gas” the correct answer. The other options, LP steam, HP steam, and direct heat in the furnace, are not typically used to heat the feed water in the economizer.