Air pre-heater pre-heats (increases the temperature) the
air supply to the furnace with the help of hot the gases.
It is installed between the
economizer and the chimney.
A tubular type air pre-heater is shown in figure. It
consists of a large number of tubes. Flue gases pass through the tube. Air
flows over the tubes. Baffles are provided to pass the air number of times over
the tubes. A soot hopper is provided at the bottom to collect the soot.
Figure: Air pre-heater
Hot flue gases pass through the tubes of air pre-heater
after leaving the boiler or economizer. Atmospheric air is allowed to pass over
these tubes. Air and flue gases flow in opposite directions. Baffles are
provided in the air pre-heater and the air passes number of times over the
tubes. Heat is absorbed by the air from the flue gases. This pre-heater air is
supplied to the furnace to air combustion.
efficiency is increased.
rate is increased.
is accelerated with less soot, smoke and ash.
grade and inferior quality fuels can be used.