Dynamics of heterogeneous azeotropic distillation columns

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Abstract
A new dynamic model has been developed for heterogeneous azeotropic distillation columns, which is capable of automatically detecting and accounting for multiple liquid phases on trays at each instant of time. Extensive dynamic simulations have been carried out for the heterogeneous distillation of ethanol, water and benzene. Our results are in general agreement with prior work, which shows that this class of separations can be expected to exhibit multiple steady states, complex dynamic behavior, and parametric sensitivity. One of the most unexpected results was that these systems exhibit parametric sensitivity with respect to small changes in column pressure. For systems vented to the atmosphere, small increases in the barometric pressure lead to loss of interface in the decanter over a 24‐hour period. If small pressure variations of this sort are left uncontrolled long enough, the entire separation will fail. Small decreases in the barometric pressure do not have such a disastrous effect.