DWC Technology

Conventional scheme for the separation of
three components
In the first column, the intermediate volatility component B reaches a
maximum somewhere in that tower, but necessarily must be lower.
This represents a thermodynamic loss (remixing) that is unavoidable in
the sequential distillation scheme.

Alternative Arrangement
The two towers are thermally integrated to one tower. The first portion of
the tower is pre-fractionator, and the second portion of the tower is main
tower. The feed enters into the side of the pre-fractionator. The entire A
and some fraction of B will go over the wall to the upper section of the
main tower. The remaining fraction of B and the entire amount of C will
go under the wall to the lower section of the main tower. The top, bottom
and side product in the main tower will be A, B and C, respectively.
This arrangement can remove remixing.