There are two styles of hot air (preheated air) burners:

  • Self recuperative
  • External recuperator

Self recuperative burners such as the immersion burner, use waste gas directly. The heat exchanger is built into the rear of the burner and the waste gas from the furnace is caused to vent from the furnace via the burner.  In operation, the the heat exchanger is cooled by combustion air which is heated on its way to the burner nozzle. In some cases the pressure drop though the heat exchanger must be compensated by the use of an integral educator. Mark IV Air Cooled immersion burners are available directly from Burns Energy Systems.



  • Combustion efficiency in the range of 65% - 72%
  • Compact
  • Simple pipework arrangement compared with hot air systems
  • Relatively simple to retrofit existing equipment
  • Individual controls


Hot air burners utilizing external recuperators are usually setup to accept combustion air at maximum 450C. Preheated combustion air is generated by an external heat exchanger. In a multi-burner system, hot air from the heat exchanger is ducted to each burner using insulated pipework. As the hot air is roughly 2.5 times the volume of cold combustion air, the ductwork must have a larger cross sectional area.



  • Usually a single recuperator is required
  • Combustion efficiency ranges between about 55% - 65%
  • Ductwork is relatively expensive
  • Duct cross-sectional area is relatively large
  • Hot air valves are required
  • Zone temperature control possible for multi burner zones
  • Individual pressure compensated fuel control is recommended

The main problem with this style of recuperation is that if there are problems with the heat exchanger, whole furnace zones must be taken down for repairs. For the self recuperative style of equipment, individual burners can be serviced. In some cases the burner must be replaced, in others the heat exchanger can be repaired or replaced.


High capacity recuperative aggregate burner.
CFD simulation of recuperative burner firing on gas.
High velocity self-recuperative burner firing with natural gas.

Industrial furnace equipment specialists

Burns Energy Systems - Industrial Furnace Spacialists