Finned Tube Economizer for Steam Boilers

Finned Tube Economizer for Steam Boilers

A finned tube economizer for steam boilers is a key device for recovering waste heat in boiler systems, which can improve the thermal efficiency of boilers and reduce energy consumption.

Structure and Composition

It is mainly composed of finned tubes, inlet and outlet headers, bends, frames, and other auxiliaries. The finned tubes are the core components, usually arranged in a line or staggered pattern. The headers are used to connect and distribute the finned tubes, the bends are used to change the flow direction of the fluid, and the frame plays a role in supporting and fixing the entire device.

Working Principle

The finned tube economizer is installed in the convective flue of the boiler. The low-temperature feed water (usually the softened water at the outlet of the deaerator, with a temperature of 100-120°C) enters the tube side of the economizer and flows along the tube bundle under the push of the water pump. The high-temperature flue gas discharged from the boiler furnace (with a temperature of over 1000°C) passes through the superheater, reheater, high-temperature economizer, and air preheater in sequence, and its temperature drops to 180-250°C before entering the shell side of the finned tube economizer. The flue gas and feed water flow in opposite directions, and the sensible heat of the flue gas is transferred to the feed water inside the tube through the wall of the finned tube, raising the temperature of the feed water to 130-160°C, while the temperature of the flue gas drops to 100-130°C. The heated feed water is sent to the high-temperature economizer for further heating, and the cooled flue gas enters the dust collector and desulfurization tower for subsequent treatment.

Advantages

High Heat Transfer Efficiency: The finned tubes significantly expand the heat transfer area. For example, a finned tube with a diameter of 50mm can increase the surface area per meter from about 0.16㎡ of a bare tube to 0.8-1.5㎡. At the same time, the fins change the flow state of the flue gas, making it turbulent, which enhances the convective heat transfer effect. Compared with bare tube economizers, the heat transfer efficiency of finned tube economizers can be increased by 30%-50%.

Good Energy-saving Effect: In industrial boilers, the heat loss of exhaust gas accounts for more than 60% of the total heat loss of the boiler. The finned tube economizer recovers the waste heat of the exhaust gas and uses it to preheat the boiler feed water or heat the combustion air, reducing fuel consumption. For example, a 10t/h steam boiler can save 50-100 tons of standard coal per year after using a finned tube economizer.

Strong Environmental Adaptability: The finned tubes can resist the adverse factors in the flue gas through material optimization and structural design. Materials such as corrosion-resistant alloys (such as ND steel, stainless steel) or aluminized low-carbon steel are used to resist acidic corrosion in the flue gas. A reasonable fin pitch (usually 5-15mm) is designed to reduce dust accumulation, and it is equipped with an online ash cleaning device to ensure stable operation in complex flue gas conditions.

Flexible Design Adaptability: According to different boiler types and flue gas parameters, the structure parameters of the finned tubes can be adjusted. For high-temperature flue gas, finned tubes with large fin pitches and thick walls can be used; for flue gas with high dust content, serrated or spiral fins can be selected; for small boilers, compact finned tube groups can be used to meet the needs of different boiler systems.

Types

According to the manufacturing process, it can be divided into welded finned tube economizers and rolled finned tube economizers. The former has a lower cost but a large amount of welding work, while the latter has less welding work but a higher cost. From the perspective of the overall structure, it can be divided into tube-shell type and flue-type finned tube economizers. The tube-shell type has a relatively compact structure and is suitable for occasions with high requirements for heat transfer efficiency; the flue-type is more convenient for installation and maintenance in large boiler flue systems.

Application Scope

It is widely used in various steam boiler systems, including coal-fired boilers, hot water boilers in power plants, refineries, and other industrial applications. It can be used in both natural circulation and forced circulation boiler systems to recover the heat of flue gas and transfer it to the boiler feed water, improving the energy utilization efficiency of the boiler system.