A standard distillation simulation model for a superfractionator is compared to a simulation with a "folded" model that eliminates model unit operation recycle loop convergence to minimize execution time. The folded simulation method incorporates the overhead vapor recompressor system of the heat pump inside the distillation unit operation. This brings the power of advanced convergence techniques for distillation to bear on the overall recycle problem. On an example case for the propene-propane system the execution time dropped by a factor of 18.8 when going from the standard recycle approach to the once-through folded approach. This leads to significant engineering time savings in optimizing the design of complex plants for multiple operating conditions. Additionally, the computationally efficient approach of the folded method simplifies the resource demands of real-time process optimization systems.
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