Typical Applications of Finned Tube Tube Bundle Economizers

Typical Applications of Finned Tube Tube Bundle Economizers

Finned tube tube bundle economizers are widely used in scenarios where flue gas conditions are relatively clean and where high heat transfer efficiency and space utilization are required. Its core advantage is to enhance heat transfer efficiency and reduce equipment volume by increasing the heat transfer area (finned extended surface area).

Environments with high flue gas cleanliness and low abrasion

1. Large coal-fired power station boilers (low ash coal)

Background: Large power station boilers are mostly powered by washed low ash power coal (ash content usually <10%), with fine fly ash particles in the flue gas, low concentration, low abrasion, and compact space in the tailrace flue (need to be arranged with multi-stage heating surfaces, e.g., air pre-conditioner, denitration device, etc.).

Advantages of finned tube:

fins (e.g. spiral fins, H-shaped fins) can increase the heat transfer area by 3-10 times compared with that of light tube, which greatly improves the heat transfer efficiency and realizes in-depth recovery of flue gas waste heat in the limited space (lowering the temperature of exhaust flue gas to 120-150℃);

low ash flue gas is less abrasive to the fins and there is no need for frequent replacement of the tube bundles, so it is suitable for long term and stable operation;

when using the process of high-frequency welded fins and so on, the combination of fins and the base tube is close and vibration-resistant, so it has strong resistance to vibration. With high-frequency welded fins and other processes, the fins are tightly bonded to the base tube and have strong vibration resistance, which makes them suitable for power station boilers with high smoke velocity (10-15 m/s).

2. Natural Gas / Gas Boilers

Background: Natural gas combustion flue gas is almost ashless (containing only trace amounts of CO₂, H₂O and NOx), with extremely high cleanliness and no wear and tear problems, but requires high equipment compactness (gas boilers are often used in buildings and industrial parks where space is limited).

Advantages of finned tube:

Ultimate compactness: under the same heat transfer capacity, the volume of finned tube economizer is only 1/3-1/5 of light tube, suitable for installation in the narrow space at the end of gas boiler;

High efficiency heat transfer: the heat transfer coefficient between flue gas and water (or vapor-water mixture) is improved significantly, and the temperature of exhaust flue gas can be lowered to 80-100 ℃ (close to the dew point, but corrosion should be avoided), so the energy saving rate is increased by 5%-8%;

No risk of accumulation of ash, long maintenance cycle (only periodic inspection is required). Long maintenance cycle (only need to check the fins periodically for looseness, no need for frequent ash cleaning).

Low Ash, Low Viscosity Biomass or Specialty Fuel Boilers

1. Formed Biomass Boilers (Pellets, Briquettes)

Background: Formed biomass (e.g., wood pellets, straw briquettes) combusts well, with a low concentration of ash in the flue gas (< 5%), fine particles, and virtually no fibrous impurities, and less abrasive and slagging properties.

Advantages of finned tube:

Compared with light tube, more waste heat can be recovered in the same space (e.g. reduce exhaust temperature from 200℃ to 140℃), which improves the boiler efficiency by 3%-5%;

Avoiding the difficulty in arranging the tail flue due to the large size of light tube, it is suitable for the compact design of small and medium-sized molding biomass boilers.

2. Methanol / Ethanol and other clean fuel boilers

Background: Alcohol fuel combustion flue gas mainly contains CO₂ and H₂O, no ash, no corrosive impurities (very low sulfur content), and no risk of abrasion or corrosion of the heating surface.

Finned Tube Advantages:

Maximize the heat transfer potential of clean flue gas, enhance heat transfer through fins, reduce exhaust temperature, and improve fuel utilization;

Small size of the equipment makes it suitable for integration in small boilers or distributed energy systems.

Waste Heat Recovery Scenarios Requiring High Heat Transfer Efficiency

1. Combined Cycle Power Plants (Gas - Steam Combined Cycle)

Background: Gas turbine exhaust temperature is high (400-600°C), and the heat needs to be recovered from the waste heat boiler to generate steam, but the flue space of the waste heat boiler is compact, and the exhaust gas is clean flue gas (containing little NOₓ and no ash).

Advantages of finned tube:

Adopting high-frequency welded spiral finned tube or flat finned tube can realize high efficient heat exchange of high-temperature flue gas in limited space and improve the efficiency of combined cycle;

Stable high-temperature resistance (high bonding strength between fins and base tube without the risk of cracking by thermal stress), adapting to the fluctuation of temperature in the exhaust gas of gas turbine.

2. Waste heat recovery from industrial kilns (e.g. glass kilns, ceramic kilns)

Background: Some industrial kilns (e.g. oil/gas fired glass kilns) have high flue gas temperatures (300-500°C) and low dust content (after preliminary dust removal) at the end of the kiln, which makes it suitable for recovering the heat to preheat the boiler feed water by means of a coal economizer.

Advantages of finned tube:

High heat transfer efficiency can quickly reduce the flue gas temperature and waste heat;

Compact structure, can be flexibly arranged in the narrow space at the end of the kiln, without affecting the main process operation.

Scenarios with limited space and resistance control

1. Marine boilers

Background: Marine boilers have extremely limited space for installation (restricted by the ship structure), and the flue gas resistance needs to be controlled (to avoid increasing the energy consumption of the fan, which affects the ship's service life).

Advantages of finned tube:

Low fin or corrugated fin design, while increasing the heat transfer area, the flue gas resistance is only slightly higher than light tube (usually 500-800 Pa), which meets the energy consumption requirements of the ship's power system;

Compact structure to fit the space of the ship's hull, and strong vibration resistance (the fins are not easy to fall off when the ship sails over the bumps).