Views: 0 Author: Site Editor Publish Time: 2026-05-14 Origin: Site
The tubular air preheater consists of bundles of parallel steel tubes arranged in a staggered configuration, with tube ends welded to tube plates to form a box-like structure (tube box) . Heat transfer occurs through the tube walls:
Hot flue gas (typically 250–400°C) flows either inside or outside the tubes
Ambient combustion air passes on the opposite side
Counterflow arrangement maximizes heat transfer efficiency
Two common orientations exist:
Vertical type – Flue gas flows vertically through tubes
Horizontal type – Flue gas flows horizontally
When flue gas contains corrosive components and temperature drops below 130°C, dew point corrosion can occur. In such cases:
Enamel-coated tubes or glass tubes are recommended
Two-stage designs (rotary + tubular in series) can keep exhaust temperature above acid dew point
Advantage | Why It Matters | Limitation | Mitigation Strategy |
High Durability | Robust steel tubes withstand high temperatures and pressures | Large footprint | Requires significant installation space |
Suitable for Large-Scale Operations | Ideal for power plants and high-capacity industrial boilers | Low-temperature corrosion | Use enamel/glass tubes or maintain flue gas above acid dew point |
Handles Heavy Dust Loads | Can operate in environments with significant soot and ash from coal or solid fuels | Ash accumulation & fouling | Install soot blowers (pneumatic or steam); design for cleaning access |
Low Maintenance | No moving parts; simple static construction | Inlet tube erosion | Use protective coatings at flue gas inlet area |
Good Sealing Performance | Low theoretical air leakage compared to rotary types |
Tubular air preheaters are widely used in :
Power plant boilers (coal-fired, biomass)
Industrial steam boilers
Chemical process heaters
Metallurgical furnaces
Cement kilns
Waste heat recovery systems
Modern tubular air preheaters incorporate:
Modular tube box design – Facilitates replacement of individual tube bundles
Expansion joints – Accommodate thermal expansion at operating temperatures up to 150°C+ preheat
Baffles – Direct airflow to enhance turbulence and heat transfer
Finned tubes – Increase heat transfer surface area by 30–50%
Soot blowers – Pneumatic or steam-powered systems for ash removal
Insulation – 100–150 mm mineral wool layers minimize heat loss
