What is the mechanism of economizer?

Economizer is one of steam boiler’s equipment which is used to heat feedwater before it is supplied into steam drum. Economizer is the heat exchanger equipment to increase boiler efficiency by absorbing heat recovery of flue gases. The lower temperature of flue gas out from stack, the heat loss will be less and the fuel which is needed to convert water into steam will be also less in certain circumstances. So it can be said that economizer can save the fuel efficiently.  Economizer will make temperature of feedwater higher, so steam boiler can produce steam easily.

The heating process of water in the economizer is like an heat exchanger, water is distributed inside tubes and flue gas outside tubes. The hot flue gas outside tubes flow and making contact with outside surface tube, so the heat transfer occur between hot flue gas and surface metal tubes by convection. Water inside tubes receives heat transfer from metal tubes, so temperature of water is higher than before enter economizer. Contact of flue gas flow to feedwater flow is regular and perpendicular. It is controlled and regulated by setting the flue gas flow.

Furthermore, feedwater that has been heated in economizer is sent to steam drum through connecting pipes. In the steam drum, feedwater will be boiler water and be heated again in water wall tubes to be saturated steam and superheater will make it as superheated steam.

The advantages of using economizer as initial heater are as follow:

- The metal wall of steam drum will not easy to be contracted, shrivel and broken because the incoming water is not cold condition so the cost maintenance will be smaller.

-  Increase steam boiler efficiency and decrease heat loss.

-  Save the fuel needed to perform combustion process

-  The size of furnace can be smaller because the requirement heat surface is less than without using economizer.