Overview
An air preheater transfers heat from hot flue gas to the combustion air entering a boiler, kiln or process furnace. Preheating the air raises combustion efficiency, reduces stack heat loss and lowers fuel consumption. The cold-end wall temperature, acid dew point and dust loading govern material selection and fin spacing.
Features
- Recovers flue gas heat to raise combustion efficiency and save fuel
- Reduces stack heat loss and emissions
- Stable structure for continuous boiler and furnace operation
- Tube and fin materials selected against flue gas composition and temperature
- Can be combined with a flue gas cooler or a complete waste heat recovery system
Materials and specifications
| Tube material | Carbon steel high-frequency welded finned tube |
| Optional materials | ND steel, stainless steel, corrosion-resistant alloy |
| Heated medium | Combustion air |
| Heat source | Boiler or furnace flue gas |
| Design inputs | Flue gas flow and temperature, air flow and target outlet temperature, sulphur content |
| Configuration | Finned tube bundle with casing and duct connections |
Typical applications
| Application | Description |
|---|---|
| Utility boilers | Combustion air preheating. |
| Industrial boilers | Efficiency improvement and fuel saving. |
| Industrial kilns | Waste heat recovery and combustion optimisation. |
| Petrochemical furnaces | Combustion air preheating. |
| Metallurgy | Furnace waste heat utilisation. |
FAQ
What is the difference between an air preheater and a flue gas cooler?
They are often used together. A flue gas cooler mainly reduces the flue gas temperature, while an air preheater uses that heat to warm combustion air. In many projects the two duties are combined in one recovery system.
Will low-temperature corrosion occur?
Sulphur-bearing flue gas can condense and corrode the cold end. The cold-end wall temperature must be checked and the tube and fin material selected for the acid dew point.
Can an air preheater be retrofitted?
Yes. A retrofit needs a check of flue gas pressure drop, available space and duct connections. Send the system drawing and layout conditions.