Azeotropic distillation with an internal decanter

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.