A FLEXIBLE ALGORITHM FOR SIMULATION AND OPTIMIZATION OF CONTINUOUS DISTILLATION. P. Skovborg Calsep A/S, Lyngby Hovedgade 29, DK-2800Lyngby, Denmark and M. L. Michelsen Department of Chemical Engineering, TechnicalUniversity of Denmark,DK-2800Lyngby, Denmark ABSTRACT A flexible computer algorithm for simulation and optimization of a continu- ous distillation column has beendeveloped. The specifications required from the userare component properties and the column setupin addition to speci- fications of distillaterate and reflux. Product specifications such as product yields or product purity can also be handled.A rigorous Naphtali- Sandholm procedure is used to solve the full set of columnequations,for given values of distillate rateand reflux. An nested loop approach is used when product purities or yields are specified. It is basedon exact column profile sensitivities with respect to changes in distillate rateor reflux. The sensitivities areeasily calculated fromthe analytical derivatives used in the basic Naphtali-Sandholm procedure. The sensitivities may also be utilizedto determine optimum feed stage locations. INTRODUCTION Continuous distillation is a very common and widelyused separation process used in the chemicalindustry,petroleum industry and other related indus- tries. Algorithms for simulating the steady stateoperation of multistage columns have been known for manyyears and exist in manyvariations.The present work presents an extension of the most general of thesealgorithms (Naphtali and Sandholm,1971) whichenables handling of moreflexible input specifications and optimization with respect to feed stage locations. THEORY The Basic DistillationProblem The basis for the present algorithm is the set of equations which formulates the general distillation problem. These equations are: NC*NST component material balances: (1) 8255