Variables affecting heat utilization

For a given furnace design and the daily heat requirements, GAH is fixed and it is required to supply this much of heat on per day basis, we can calculate

(5)

If heat supply is the critical factor in determining the process throughput then GAH can not determine the throughput, we have to consider the NAH

(6)

Heat utilization or fuel utilization according to equation 5 is inversely proportional to GAH/kg of fuel. We can derive the factors affecting heat utilization by considering eq.1

Air adjustment: Calorific value (CV) of fuel is the energy obtained on complete combustion of fuel with theoretical amount of air. Excess air, air leakage, furnace draft, fuel/air ratio will control the fuel consumption

Sensible heat of reactant; this heat directly adds to the furnace, fuel consumption will decrease.
POC temperature: an increase in POC temperature will increase fuel consumption

Incomplete combustion or un-burnt fuel; corresponding to incomplete combustion part of the CV of fuel is lost in POC.

Reference: P.Mullinger and B. Jenkins: Industrial and process furnaces
                   O.P. Gupta: elements of fuels. furnaces and refractories.
                   R. Schumann: Metallurgical Engineering Ptinciples