If fatty acids and odoriferous substances are to be distilled at as low a temperature
as possible, distillation must be carried out at low absolute pressures effected by the
vacuum system. The boiling point of the fatty acids and the vapor pressure of the
odoriferous materials decrease as the absolute pressures decreases. The required low
absolute pressure, usually between 2 and 4 mbar, is commonly generated by vacuum
systems consisting of a combination of steam jet ejectors, vapor condensers, and
mechanical vacuum pumps. Special vacuum systems have been developed to reach
lower pressures and operating costs and, at the same time, reduce emissions by a
more efficient condensing of the volatiles. In the dry condensing systems, the sparge
steam is condensed on surface condensers working alternatively. The remaining
noncondensables are removed by mechanical pumps or by a vacuum ejector system