Indirect and Direct Heaters


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General arrangement of direct process air heater




Process air heater can also be delivered as indirect heaters in which a combustion chamber with a burner is equipped also with a heat exchanger that transfer the heat from the combustion gasses to the clean process air.

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Combustion Gas - to - Process air heat exchanger (indirect process air heater). This units has a capacity of 120,000 Nm³/h process air @ 650°C installed at Sam Nam, Korea and Bakrei Kasei, Indonesia. Read more about gas-to-gas heat exchangers.



These direct and indirect heating of process air are alternatives to numerous other ways to heat up process air (using, steam, thermal oil, electrical heating etc) by process air heaters.


The most efficient and cheapest way to heat up air / gas is to have the flame of a burner in the air/gas stream. This direct heating means that the combustion exhaust gas is mixed with the air/gas. With this direct heating you will be able to achieve very high temperature on the air/gas. However in certain applications this cannot be allowed.

TT BOILERS direct process air heater are developed and designed especially for high temperature and large air/gas flows. The flame of the burner is kept stabilised by a special profile of the air/gas flow.


1 MW direct process aitr heater ready for delivery

                  Internal lining (refractory) of the combustion chamber and access for the burner.

See also our range of exhaust air incinerators used for elimination of of odours which use a slightly different design of combustion design.