What are the benefits of boiler combustion air pre-heater ? (Energy Efficiency Tip of the Day)

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Tip summary

·       Combustion air preheaters are similar to economizers in that they transfer energy from the flue gases back into the system. In these devices, however, the energy is transferred to the incoming combustion air.

·       The efficiency benefit is roughly 1% for every 40°F increase in the combustion air temperature.

·       Changes in combustion air temperature directly affect the amount of combustion air supplied to the boiler and may increase or decrease the excess air.

·       There are two main types: recuperative and regenerative air heaters, Tubular or recuperative air pre-heaters are provided in boilers of medium and small range of steam generation.

·       Steam coil air pre-heaters are another type. These are used only during startup of the boiler to prevent low temperature corrosion. This air heater does not contribute to improving the efficiency of boilers, but are provided to improve availability. It is seen that during start up the chances of low temperature corrosion is high, and hence the need to provide the steam coil air heaters is evident.

·       Both economizer and air pre-heaters are called heat recovery systems in a boiler. Were it not for these heat recovery systems, present day boilers would be operating at much lower efficiency levels.

·       Issues to be considered during design and retrofit:

o  Flue gasses sulfur content (Dew point corrosion).

o  Flue gas back pressure.

o  Preheating effect on excess O2.

Proposed actions

o  Flue gases content and boiler efficiency

o  Evaluate the possibility and suitable type of preheater.

o  Evaluate the economics of the required changes.


o  System retrofit will have a medium cost with quick ROI.



o  Estimated energy savings range: 5%.


o  Combustion air preheaters can improve boiler efficiency by 5% but it needs careful evaluation and design.

o  Please share this tip with others to share knowledge and increase energy efficiency awareness.

o  Please contact me for any advice or support about this issue or other energy management issues.

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My blog: www.360proactiveengineer.com

#Energy #energyefficiency #energymanagement #steam #steamsystem #sustainable #sustainability #engineering #engineer #chemicalengineering #combustion #360practiveengineer #combustionairpreheater

Magdy Aly

Energy manager, Energy efficiency consultant Passionate to help others to save Energy and Environment.

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