Heat and plume lost up the stack

Conventional boilers expel flue gas well above ambient temperature, wasting sensible heat, and the warm, moisture-laden plume can condense into a visible white plume that annoys neighbors. Recovering that heat for incoming combustion air or building heating cuts fuel use and can suppress the plume.

Suitable exchanger types and how they work

A stainless plate air preheater transfers flue-gas heat to the combustion air or a separate heating loop. Running the exhaust below its dew point lets a condensing exchanger also recover latent heat, squeezing more efficiency out of the same fuel. An air-to-water recovery loop is an alternative when water heating is the better sink.

Design considerations for flue gas

Flue gas is corrosive, especially below the acid dew point. Specify stainless or alloy plates, provide condensate collection and neutralization, and protect against low-temperature corrosion. Size for the boiler’s flue volume and pressure drop, and ensure the recovered heat has a real use (preheat, space heating, or process) so the savings are captured.