Why Is An Air Preheater Used?

An air preheater is used to recover waste heat from exhaust or flue gas and transfer it to incoming combustion air. This increases overall system efficiency and reduces fuel consumption.

Key Reasons an Air Preheater Is Used

1. Improve Thermal Efficiency

By preheating combustion air, less fuel is required to reach the target flame temperature. This directly increases boiler, furnace, or kiln efficiency.

2. Reduce Fuel Consumption

Warmer combustion air improves fuel–air mixing and combustion stability, leading to lower fuel usage and reduced operating costs.

3. Recover Waste Heat

Air preheaters capture heat that would otherwise be lost with exhaust gases, making them a critical component of waste heat recovery systems.

4. Increase Combustion Stability

Preheated air promotes faster ignition and more complete combustion, especially important for:

• Low-grade fuels

• High-moisture fuels

• Large industrial burners

5. Reduce Emissions

Better combustion efficiency leads to:

• Lower CO and unburned hydrocarbons

• Reduced overall CO₂ emissions per unit of heat generated

6. Increase System Capacity

In some systems, preheating the air allows the same boiler or furnace to:

• Generate more steam

• Reach higher process temperatures
  without increasing fuel input.

7. Improve Cold-Start Performance

Air preheaters help stabilize combustion during startup and low-load operation by preventing flame instability caused by cold intake air.

Typical Applications

• Power plant boilers

• Industrial furnaces and kilns

• Waste incinerators

• Process heaters

• Cement and steel plants

Common Types of Air Preheaters

• Recuperative (tubular or plate-type)

• Regenerative (rotary/Ljungström)

• Heat pipe air preheaters