The aim of a heat recuperator is to transfer the heat contained in the
outlet air, having temperatures of 80-95șC, from the spray dryer and to utilize
it e.g. to preheat the drying air. But it is also possible to use the
recuperated heat to heat water for cleaning purposes or air for heating rooms.
In the following only preheating of the drying air is discussed.
In
principle, there are two different recuperating systems:
- Air-to-Air
- Air-Liquid-Air
Both systems are incorporated after the fines separator. However,
incorporating a bag filter prior to the heat recuperator increases the
efficiency, as deposits on the heat surface cannot be completely avoided even
with correctly selected air velocities in the dust-loaded air. It is possible
to operate the recuperator several days without cleaning, but should it prove
necessary to clean the equipment, this is done by means of a built-in CIP
system.
If the heat recuperator is designed to cool the outgoing air
below the condensation temperature (depending upon moisture content per kilo
dry air), also the condensation enthalpy is used for preheating. In this case a
bag filter is installed prior to the heat re-cuperator to avoid deposits in the
intermediate zone between the dry and wet area. Even bigger savings are then
possible than the ones described below, which are all calculated without
condensation.
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