Regions of Optimality for Separation System Synthesis Using Rigorous Modeling, Stochastic Optimization, and Column Stacking

Alternatives for the separation of
three-component zeotropic mixtures
are compared using simulation optimization with the total annual cost
as the objective function. Conventional two-column sequences with
and without column stacking are compared with three types of dividing-wall
columns (DWCs). All processes are modeled with a rigorous process
simulator and optimized using simulated annealing. The results are
represented using ternary maps and used to regress parameters of a
model that predicts the relative cost of process alternatives as a
function of the feed composition, relative volatilities, and ease
of separation index. The results highlight the importance of considering
column stacking when choosing a process alternative for the ternary
separation: in some cases, the region where the stacked two-column
configuration is preferable to a dividing-wall column is significantly
larger than the area where a conventional two-column configuration
is preferable to a dividing-wall column.