Flue Gas Loss
Flue gas loss is the energy carried out of the stack by hot combustion gases. It is usually the single largest loss in a fired boiler or furnace, and it grows with excess air and stack temperature — both controllable through combustion tuning and heat recovery.
Every fired heater sends hot gases up the stack; the heat in them is lost unless recovered. Two factors drive the loss: stack temperature (reduced with economisers and air preheaters that recover that heat) and excess air (minimised with oxygen-trim combustion control). Cutting flue gas loss is typically the highest-impact efficiency measure on a boiler or furnace.
Related terms
Boiler Efficiency · Economiser · Waste Heat Recovery · Superheat
Where this applies
Commissioning a new boiler · Retrofitting waste-heat recovery · Retrofitting a boiler economiser · Adding flue-gas oxygen trim control · Preheating combustion air · Sequencing and allocating load across multiple boilers · Controlling air preheater leakage · Optimising stack damper and furnace draught