A crude distillation unit model suitable for online applications

A steady state, multicomponent distillation model particularly suited for f ractionation of crude oil has been developed based on equilibrium stage rel ations. For a mixture of C components, the present formulation uses C + 3 i teration variables namely the mole fractions of the components, temperature , total liquid and total vapor flow rates on each stage. This choice of var iables makes the present model numerically stable and robust rendering a se parate initial guess computation unnecessary. An improved scheme of numberi ng the equilibrium stages when side strippers are present, was found to be advantageous with respect to computation time, Selected example problems ha ve been included from literature as well as industry to demonstrate the eff icacy and usefulness of the method. The accuracy of predictions and speed o f solution of the model equations are particularly suited for online applic ations such as online optimization. (C) 2001 Elsevier Science B.V. All righ ts reserved.