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Flue Gas Recirculation (FGR)

Flue gas recirculation (FGR) is a highly effective technique for reducing NOx emissions in various types of combustion processes. In the case of multiple hearth incinerators, FGR systems move flue gas from the feed hearth to a hearth below the volatile burning hearth. Recirculating the flue gas works to reduce NOx in 2 ways:
  1. The cooled, mostly inert, recirculated flue gas serves to cool the incinerator, adsorbing heat and lowering peak hearth temperatures.
  2. When mixing mostly inert flue gas with combustion air, the oxygen content is reduced. This reduction in oxygen content acts to limit NOx production by reducing one of the elements needed for the reaction that produces NOx.
Beyond reducing NOx, FGR can have several other benefits when used in a multiple hearth incinerator, including:
  • Reduction in fuel usage
  • Reduced slag formation
  • Reduced flare-up during feed stoppage
  • Increased operational stability
  • Complete ash burnout
  • Reduced THC emissions
Chavond-Barry Engineering Corp. is experienced in the design and implementation of FGR systems for multiple hearth incinerators. More information, including performance data from previous installations and reports, are available upon request.

Click the button below to see the "Method and apparatus for controlling combustion in a furnace" written by the company owner Louis T. Barry to learn more about controlling combustion in the furnace using flue gas recirculation.
Videos below demonstrate the effect of Flue Gas Recirculation (FGR) on combustion within a Multiple Hearth Furnace.
Combustion without FGR.
Combustion with FGR.