The total re
ux condition can be achieved by operating the column at nite feed and
product output with a very high re
ux rate or by operating it with no further input
of feed and no withdrawal of products and maintaining the internal boil-up and re
ux
(Seader and Henley, 1998). For a given separation, a minimum number of stages (Nmin)
is required under the total re
ux condition.