What is a Boiler Economizer?

Boiler Economizer Diagram Ilustration

Economizer is a mechanical device used to reduce energy consumption or perform other useful functions such as heating fluid.  Economizers recycle energy produced within a system or take advantage of differences in environmental temperature to achieve increased efficiency.

Boiler Economizer

Boiler economizers are heat exchange devices that heat a liquid, usually water, up to but usually does not exceed the boiling point of liquid. Economizers are so named because they can utilize the enthalpy of the fluid flow is hot, but not hot enough to be used in the boiler, so that the enthalpy recovery is more useful and improve boiler efficiency. They are a device fitted to a boiler which saves energy by using exhaust gas from the boiler to heat the cold water used to fill it.

Modern boilers, such as in coal power plants, still equipped with economizers that are descendants of the original design of the Green. In this context they are often referred to as the feed water heater and hot condensate from the turbine before it is pumped to the boiler.

Economizers are typically used as part of the heat recovery steam generators in combined cycle power plant. In the HRSG, water passes through economizer, boiler and superheater then later. It also prevents flooding economizer in the boiler with liquid water is too cold to boiling given flow rate and boiler design.

A typical application of economizers in steam powerplants to capture waste heat from boiler stack gases (exhaust gas) and transfer to the boiler feed water. This increases the temperature of boiler feed water, lowering the required energy input, in turn reducing the level required for firing the boiler rated output. Economizers lower the stack temperature can cause condensation of combustion gases and acid corrosion serious equipment damage if care is not taken in the design and material selection.