Evaporator with wiped film as the reboiler of the vacuum rectifying column

Vacuum distillation and rectification of heat-sensitive substances is usual ly accompanied by some thermal decomposition, which can be minimized by dec reasing the operating temperature and by reducing the contact time of the d istilled mixture with heated surfaces. A considerable reduction of the resi dence time can be acheived in reboilers of the evaporator type with liquid film, which produce vapours for the vacuum rectifying column. This paper de scribes such a reboiler-evaporator with wiped liquid film with two evaporat ing surfaces. On one of them, the evaporation of the original feed takes pl ace, on the second, the evaporation of the reflux from the column occurs. T he experimental results of separation efficiency of the vacuum rectifying c olumn with a reboiler of the type described in the laboratory scale, are pr esented with dependence on feed, reflux and temperature conditions in the r ebolier. With suitable heating of the reflux surface it is possible to cont rol the vapour and liquid flows in the column. (C) 1999 Elsevier Science B. V. All rights reserved.