For materials sensitive to heat damage, a vacuum drum
dryer may be used to reduce drying temperature. A
vacuum drum dryer is similar to other drum dryers except
that the drums are enclosed in a vacuum chamber. In
continuous vacuum drum dryers, receivers and air locks
are designed to provide appropriate seal. Equipment and
operation of vacuum drum dryers are relatively expensive,
which limits vacuum drum drying to only high-value
products or products that cannot be produced more
economically by other means.