components in addition to the isobutene. These inerts go out the top of the column. The production rate is set by the flow controller on the isobutene feedstream. The ethanol concentration on a suitable tray in the column is maintained by manipulating the ethanol fresh feed. Reboiler heat input controls a tray temperature in the stripping section to maintain ETBE product quality.
The tert-amyl methyl ether (TAME) reactive distillation system considered in the next section has similar chemistry (two reactants and only one product), and an internal composition controller is required to balance the reaction stoichiometry. There is a recycle stream of one of the reactants in the TAME system, but this occurs because of the existence of azeotropes that carry some of this reactant out of the column with the inerts present in the feed.
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