What Is a Boiler Economizer? Definition, Function, Types, Advantages

What Is a Boiler Economizer?

A boiler economizer (or economiser) is a heat recovery device installed in the boiler’s tail-end flue gas path. It captures residual heat from exhaust gases (typically 250–350°C) to preheat boiler feedwater before it enters the steam drum. By transferring waste heat to water, it reduces fuel consumption, lowers flue gas temperatures, and improves overall boiler efficiency by 10–15%.

How Does It Work?

1. Flue Gas Passage: Hot combustion exhaust gases exit the boiler and flow through the economizer tubes or coils.
2. Heat Transfer: Cool feedwater is pumped through the economizer’s tube bundle, absorbing heat from the flue gas.
3. Preheated Feedwater: The warmed feedwater enters the boiler at an elevated temperature, requiring less additional heat to reach boiling point.
4. Efficiency Gain: Raising feedwater temperature by approximately 10 °C can boost boiler efficiency by around 2%.

Boiler Economizer Schematic

Gas boiler with economizer on top (Integrated economizer boiler):

Gas boiler with economizer in front (Split economizer boiler):

Types of Boiler Economizers

Boiler economizers come in several configurations to suit different applications:

1. Non‐Condensing Economizer
   • Lowers flue gas temperature above the dew point to avoid acid condensation.
   • Recovers sensible heat only, with minimal corrosion risk.
2. Condensing Economizer
   • Cools flue gas below the water‐vapor dew point, recovering both sensible and latent heat.
   • Higher heat recovery but requires corrosion‐resistant materials.
3. Shell‐and‐Tube Economizer
   • Feedwater flows through tubes inside a shell; flue gas passes around them.
   • Robust and suitable for high pressures; however, it occupies more space.
4. Plate or Finned‐Tube Economizer
   • Employs compact plate packs or finned tubes to maximize surface area.
   • Ideal for small‐footprint and retrofit applications.

Additional specialized designs include circular (“in‐stack”) economizers and modular skid‐mounted units for ease of installation.

Advantages of FangKuai Boiler Economizers

According to FangKuai’s product literature, their economizer solutions offer:

• High Heat‐Recovery Efficiency: Custom‐engineered finned‐tube arrangements extract maximum heat from flue gases.
• Corrosion‐Resistant Materials: Alloy steels and protective coatings withstand acidic condensate in condensing units.
• Compact, Modular Design: Factory‐assembled skid units simplify installation and retrofit on existing boilers.
• Low Maintenance: Smooth tube surfaces and easy‐access headers streamline cleaning and inspections.
• Enhanced Fuel Savings: Typical installations deliver a 5–10% reduction in fuel consumption, translating to rapid ROI.

These advantages help boiler operators achieve lower operating costs and reduced emissions, in line with modern efficiency standards.

Conclusion

Economizers pay for themselves fast by capturing heat your boiler would otherwise waste—warming feedwater ahead of time so you burn less fuel, cut emissions, and keep steam or hot water flowing smoothly. FangKuai’s tough, modular units grab extra heat from flue gases and their sleek design makes cleaning a snap, so you save on both fuel bills and maintenance headaches.