Tubular Air Preheater


A Tubular Air Preheater is an heat transfer equipment which captures the heat from the flue gas and transfers it to the air. This heated air is utilized for the combustion process in an boiler. Its purpose is to enhance thermal efficiency by capturing heat from the flue gas, thereby augmenting efficiency by minimizing heat loss in the flue gas. Typically installed in thermal power plants, it is positioned next to the economizer coils in the boiler. It is designed accordingly to the operating conditions & requirements of the customer.

Tubular Air Preheater


Constructed primarily with either vertical or horizontal tubes, this type of preheater utilizes steel tubes operating at low to medium temperatures. TAPH tubes with a diameter of 40 to 65 mm and a thickness of 2.0 to 2.5 mm are welded to the tube sheets with utmost care to avoid damage from welding heat. Tube Length, Tube diameter, Number of Tubes and Tube bundles in APH is designed based on the heat transfer area required to achieve the Estimated outlet temperature of air. Airflow can be either inside/outside of the tubes and the arrangement of the tubes can be inline/staggered.


The air preheater receives hot flue gases from the boiler through the flue gas inlet positioned at the top and atmospheric air enters through the air inlet. Both air and flue gases flow in a crossflow manner, and the tubes efficiently absorbs heat from the flue gases and transferring it to the atmospheric air. Positioned at the bottom of the preheater is a soot hopper designed to collect and store soot and ash. This process effectively preheats the air, preparing it for further combustion in the boiler.


Tubular Air Preheaters confer several advantages to power generation facilities and process plants, including

  • Stability of combustion is improved by usage of hot air
  • Elevating efficiency in steam boilers
  • Reducing excess air
  • Increasing steam-generating capacities of boilers
  • Helping energy conservation by extracting surplus heat from flue gases
  • Greater stability to steam boilers by recycling existing hot air
  • Less unburnt fuel particle in flue gas thus complete combustion is achieved


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