A distillation column with an internal decanter is used to separate a mixtu
re containing five some oxygenated and hydrocarbons and having at least thr
ee carbon atoms, and water. One of the species is partially miscible with w
ater, as well as another organic species. Both binary pairs exhibit azeotro
pes above the minimum bubble-point temperature. The column is very sensitiv
e to small disturbances which can lead to flooding, poor product quality, a
nd migration of an embedded two-liquid phase region within the column. Thes
e disturbances can cause the column to move from one steady state to anothe
r for the same specifications. Multiple operating regimes are exhibited, wi
th unusual transitions between them. Two regions involving multiple steady
states are observed, one of which involves the partial-miscibility of two o
rganic phases. The dynamics of moving interfaces between trays having one-
and two-liquid phases, as well as controllers to insure that unwanted trans
itions do not occur, are examined. (C) 2000 Elsevier Science Ltd. All right
s reserved.