What Is an Economizer Bundle?

An economizer bundle is a tube bundle heat exchange assembly installed in boilers or waste heat recovery systems to recover residual heat from flue gas. Its primary function is to preheat boiler feedwater before it enters the steam drum, thereby reducing fuel consumption and improving overall boiler efficiency.

Unlike single-tube or compact coil designs, an economizer bundle typically consists of multiple parallel tubes arranged in banks or modules, offering a larger heat transfer surface and higher thermal performance.

Working Principle of an Economizer Bundle

The operating principle of an economizer bundle is based on indirect heat exchange:

• High-temperature flue gas flows across the outside of the tube bundle

• Boiler feedwater flows inside the tubes

• Heat is transferred from flue gas to feedwater

• Preheated water enters the boiler, reducing the required combustion heat

This process lowers exhaust gas temperature and maximizes waste heat utilization.

Key Advantages of an Economizer Bundle

1. Enhanced Heat Transfer Efficiency

The bundle configuration provides a large effective heat transfer area, making it highly efficient for recovering sensible heat from flue gas.

2. Reduced Fuel Consumption

By increasing feedwater temperature, the economizer bundle reduces the boiler’s fuel demand, leading to significant operating cost savings.

3. Lower Stack Temperature and Emissions

Lower exhaust temperature results in reduced thermal losses and helps decrease CO₂ and NOx emissions.

4. Flexible Design and Customization

Economizer bundles can be customized in terms of tube layout, material selection, and size to suit different boiler types and operating conditions.

5. Long Service Life

Proper material selection and structural design allow economizer bundles to operate reliably under high temperature and pressure conditions.

Typical Applications of Economizer Bundles

Economizer bundles are widely applied in:

• Utility and industrial boilers

• CFB and pulverized coal-fired boilers

• Waste heat recovery units

• Power generation plants

• Cement, steel, and petrochemical industries

• Energy-intensive continuous process systems

They are especially suitable for large-capacity boilers with stable flue gas flow.

Materials and Construction of Economizer Bundles

Material selection for an economizer bundle depends on operating temperature, pressure, and flue gas composition. Common materials include:

• Carbon steel for standard boiler applications

• Low-alloy steel for elevated temperatures

• Stainless steel for corrosive or high-dew-point environments

The bundle structure is designed to allow sufficient gas flow, minimize fouling, and support soot-blowing or online cleaning where required.

Economizer Bundle vs. Economizer Coil

Compared with an economizer coil, an economizer bundle generally offers:

• Larger heat transfer surface

• Higher capacity for large boilers

• Modular installation and maintenance advantages

Economizer coils are often used in compact or space-limited systems, while economizer bundles are preferred for medium- to large-scale industrial boilers.

Conclusion

An economizer bundle is a proven and highly efficient solution for boiler heat recovery. By maximizing waste heat utilization, it improves boiler efficiency, reduces fuel consumption, and supports environmental compliance. For industrial facilities seeking long-term energy savings and stable boiler operation, an economizer bundle represents a reliable and cost-effective investment.