Importance of the selection of feed tray location on the optimum design of a heterogeneous azeotropic distillation column with p-xylene feed impurity

摘要

In the production of aromatic acid, such as terephthalic acid, tiny amounts of one reactant (in this study, p-xylene) may also enter into the acetic acid dehydration column through the feed stream. In this work, the process design flowsheets with and without this tiny impurity are both considered. For the case with this tiny impurity in the feed stream, a side stream is necessary to purge out this impurity, otherwise, accumulation of this impurity will occur inside the column. If only optimum side-stream location and its flow rate are considered in the optimization search, it is found that the TAC (total annual cost) and the operating cost of this acetic acid dehydration column become much higher by just adding extremely small amount of p-xylene in the feed stream. With careful selection of the feed tray location, significant TAC.as well as energy savings for the operation of this column can be realized.