ABSTRACT
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Linear grid and in-duct burners were used for many years to heat air for drying operations before use in co-generation systems became widespread. Some of the earliest heating systems were merely a gas lance inserted into the air stream. Other systems mixed fuel and air in an often-complicated configuration to fire into a relatively low-temperature recirculating process air stream with oxygen depleted by combustion or water vapor. General use in high-temperature, depleted oxygen streams downstream of gas turbines began in the early 1960s and such systems were used to increase steam production in waste heat boilers for process use in industrial applications, or to drive steam turbine-generators for electrical peaking utility plants. Gas turbines have become larger and more efficient in the intervening years, and duct burner supplemental heat input has increased correspondingly.
