What is the primary function of an economizer in a thermal power plant?

The primary function of an economizer in a thermal power plant is to recover waste heat from the flue gases leaving the boiler. By capturing this heat, the economizer preheats the incoming feedwater before it enters the boiler. This process enhances the overall efficiency of the system by reducing the amount of energy required to reach the necessary temperature and pressure for steam generation.

In doing so, the economizer contributes to lowering fuel consumption, reducing emissions, and improving overall thermal efficiency. This heat recovery is crucial, as significant energy can be wasted through heat loss in the flue gases, and recovering it helps to minimize this loss.

The other options hint at different functions unrelated to the primary role of the economizer. For example, recycling steam is not the economizer's job but rather relates to systems like steam condensate return systems. Similarly, maintaining water levels in the boiler is managed by feedwater control systems, which ensure the boiler operates safely. Generating electricity from exhaust gases is not a function performed by an economizer; this is typically achieved through a combined cycle or other technologies designed for energy recovery from exhaust sources.