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Keywords:

  • interval methods;
  • output multiplicities;
  • multiple solutions;
  • bifurcation;
  • MSS

Abstract

Multiple steady states are typically discovered by tracing a solution path, including turning points. A new technique is presented here that does not follow this approach. The original problem is solved directly, without tracing a solution path. The proposed branch-and-prune algorithm is guaranteed to find all solutions automatically. Core components of the framework are affine arithmetic, constraint propagation, and linear programming. The C++ implementation is available as an open-source solver and has an interface to the AMPL® modeling environment. In certain difficult cases, only continuation methods have been reported to find the unstable solution automatically. The proposed method seems to be the first published alternative method in those cases. Although this article focuses mainly on distillation, the presented framework is fairly general and applicable to a wide variety of problems. Further, computational results are given to demonstrate this. © 2010 American Institute of Chemical Engineers AIChE J, 2011