Pressure Swing Distillation
Pressure swing distillation is a specialized type of distillation that has the ability to
separate azeotropic feeds without the aid of additives. This process has a series of
distillation columns that operate at different pressures in order to break the azeotrope.
The first column operates at one pressure to separate a small amount of ethanol from
the mixture. The distillate from this column is then sent to another distillation column
that operates at a different pressure, breaking the azeotrope, and separating a little
more ethanol. The bottoms of the column is sent back to the feed as a recycle stream.
This repeats with a number of towers until the desired volume percentage of ethanol is
achieved. Although successful, this method is not feasible for the purification of
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ethanol to 99.5% v/v as it requires high energy consumption. It also requires many
large columns which would result in high capitol costs. “Pressure swing distillation can
be used to break an ethanol‐water mixture that forms an azeotope. The process
consists of three or more columns operating at different pressures”