New Tools for the Computer-Aided Design of Nonideal Distillation Systems

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The area of computer aided process design has advanced substantially in the recent past. Among some of these recent developments are new methods to design complex industrial systems. There is an economic incentive to develop such engineering tools provided they are simple and accurate and are able to discriminate between process alternatives very early in the life of a project in order to eliminate designs that are unsafe, uncontrollable, as well as uneconomic. An area of both commercial and academic interest which has not been successfully addressed to date is the design of nonideal, multicomponent distillation systems. When the process streams form an ideal mixture, existing conceptual design methods provide efficient means for narrowing down the possible distillation sequences to a small number of promising alternatives. These can then be designed and costed in more detail using simulator-based techniques. For nonideal and azeotropic mixtures, however, there exist no procedures or tools for choosing between different nonideal distillation sequences without carrying out extensive full-scale computer aided simulations and costing. The PI plans to develop a new class of techniques for computer aided analysis, design and synthesis of nonideal and azeotropic distillation systems. The methods exploit geometric properties of the nonlinear discrete dynamical system representation of the steady state composition profiles in the composition state space. The procedure can be extended to include multicomponent reactive distillation columns. The technique also provides a procedure for determining the minimum flows and the number of theoretical stages in each column section for reflux ratios above the minimum without the necessity of lengthy iterative schemes, as is the current practice. The PI plans to look at commercially important situations including non-sharp splits, multiple-feed columns, and tangent pinches.