Waste heat recovery in a boiler refers to the process of capturing and utilizing the heat energy that is typically lost as waste during the combustion or operation of the boiler. Boilers are used to generate steam or hot water for various industrial processes, heating applications, or power generation.
During the combustion of fuel in a boiler, heat is produced, and a portion of this heat is lost through flue gas emissions and other sources. Waste heat recovery systems aim to recover and utilize this lost heat energy, thereby improving the overall energy efficiency of the boiler system.
There are different methods of waste heat recovery employed in boilers, including:
Economizers: Economizers are heat exchangers installed in the flue gas path of a boiler. They capture and preheat the incoming feedwater by transferring heat from the hot flue gases. This reduces the amount of fuel required to raise the temperature of the water, resulting in energy savings.
Condensing Economizers: Similar to standard economizers, condensing economizers also recover heat from flue gases. However, they are designed to extract heat to such an extent that the water vapor in the flue gas condenses. This process releases additional latent heat, further enhancing the heat recovery efficiency.
Heat Recovery Steam Generators (HRSG): HRSGs are used in cogeneration or combined-cycle power plants. They recover waste heat from the exhaust gases of a gas turbine and utilize it to generate steam. This steam can then be used to drive a steam turbine for additional power generation.
Flue Gas Condensation: This method involves cooling the flue gases below their dew point, causing water vapor to condense. The condensation releases heat, which can be recovered and utilized.
By implementing waste heat recovery systems, boilers can significantly improve their energy efficiency, reduce fuel consumption, and lower greenhouse gas emissions. Waste heat recovery is an important consideration in industries and power plants where substantial amounts of heat are generated and lost through boiler operations.