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As a thermodynamically equivalent arrangement of dividing-wall column,Petlyuk sequence contributes greatly on energy conservation that become a hot topic.It is shown in many papers that a typical Petlyuk column used for benzene-toluene-xylene(BTX) separation can save more than 30% [1]energy compared with the best conventional scheme.In this paper,an operating condition optimization problem of the Petlyuk column was conducted.Reflux ratio and bidirectional flow of interconnecting streams are adjusted to minimize the reboiler heat duty (QR) while all products are qualified.The Petlyuk sequence creates several potential operating problems,especially values of interconnecting flows which are predominant influences in controlling products purities,but their selection ranges are determined by reflux ratio and feed condition simultaneously.Detailed steps from simulation to optimization of Petlyuk column for BTX separation are described.Four cases with different feed compositions,subcooled liquid,saturated liquid and saturated gas at 137.931kPa pressure have been illustrated to demonstrate the analysis.In these cases,sequential modular algorithm is used,and an extra simulation for find initial values of four interconnecting flows is added.Two constraints are also added to search approximate feasible domains of MV and ML which represent gas and liquid streams from main column to prefractionator,respectively.It is shown that bad initial values of four interconnecting can make simulations not convergence,even if MV and ML are both in feasible domains.And some values of MV and ML can convergence in simulation use ASPEN PLUS,but it make temperature distribution of prefractionator unreasonable.Optimization results indicate that good initial values make simulation convergence quickly,and reasonable feasible domains of MV and ML are the basis of optimization.Different feed conditions can bring about corresponding optimal designs.For a given design,reflux ratio has significant influence on QR,big reflux ratio brings about big energy consumption.And at the same reflux ratio,a point in feasible domains of MV and ML is exist that provides minimum QR.Values of MV and ML are the chief influence factors of products purities.