Design and Analysis of Multiple Thermally Coupled Configurations Using Column Profile Maps

This presentation introduces a method for rapidly assessing the feasibility of multiple thermally coupled separation units. The Column Profile Map technique has been applied to the design of a variety of quaternary feeds for a column consisting of a main column with various combinations of side rectifiers and/or strippers, as well as a fully thermally coupled column. The graphical nature of the technique allows one to easily assess feasible designs for systems with less than four components, but may be algebraically extended to higher-order systems using an eigenvector technique. Iso-reflux plots are presented as a tool to evaluate the minimum operating conditions of a specific column that also shows part of an Attainable Region and places bounds on operability. The fully thermally coupled arrangement is shown to require the least amount of heat addition for a variety of feeds, but also has by far the lowest thermodynamic efficiencies. We have further found that, subject to feed compositions, multiple side strippers, in agreement with modern crude refinery practice, have good first law expenditures with efficiencies comparable to other thermally coupled structures.