Previous columns in this series have examined a number of combustion topics, such as stoichiometry, heat balances and thermal efficiency.

An exothermic gas atmosphere can prevent surface oxidation during the heat treatment of metals.

There are at least two ways to describe a furnace’s thermal performance. The percent-available heat^[1] indicates thermal efficiency, while the adiabatic flame temperature^[2] indicates heat-transfer intensity. Both factors can be used to indicate a furnace’s productivity.

Much of the heat produced by fuel combustion is unavailable for productive use.

Last month’s article showed how to make a system balance when the material and heat balances were coupled.

Maintaining the efficiency of a heating process depends on knowing (or calculating) the heat of combustion of a fuel. In some cases, it’s sufficient to use an approximate value, such as 1,000 BTU/ft³ for natural gas.

Efficient process heating requires recovery of the largest possible fraction of a fuel’s combustion heat into the material being processed. There are many avenues of loss in the operation of a heating process. Typically, the dominant loss is energy leaving with the offgas.