Interphase transport and multistage separations. Final report, September 1, 1984--August 31, 1994

This report gives a summary of the research accomplished under this project which included: Collocation analysis of multistage separation systems; Heat and mass transport fundamentals; Fractionation tray modeling; and Computational and statistical methods. The large equation sets encountered in tray-by-tray modeling of distillation systems are a major obstacle in computer-aided process engineering. The authors addressed this difficulty by approximating the multistage equations with much smaller sets, obtained by orthogonal polynomial interpolation over the stages. A new approach to column design was initiated when they discovered how to extend their collocation formulas to modules containing non-integer numbers of stages. This extension proved equally useful for column simulations in the presence of more than one liquid phase. They also investigated strategies to handle locally steep concentration profiles and high-purity separations. As a basis for realistic modeling of fractionating trays, a comprehensive comparison of various computation methods for multicomponent mass transfer was undertaken. A theoretical study was carried out for asymptotic forms for heat and mass transfer rates in boundary layers. Newton`s method was used in several of the computational algorithms for equation solving, parametric sensitivity analysis and nonlinear parameter estimation. The authors investigated modifications of the Newton method designed to achieve convergence over a wider range of initial guesses. Other computer codes have been enhanced as a result of this project