A new algorithm was developed for the solution of the equations that describe multicomponent, multistage separation processes operating at steady state. The algorithm is based on the use of newly defined energy and volatility parameters as the primary successive approximation variables. A third parameter was defined for each stage as a unique combination of the liquid and vapor phase rates and the temperature, and the quasi‐Newton method of Broyden was employed to iterate on these parameters. The exceptional stability of the new algorithm in very difficult cases, as well as its efficiency in easy cases, are demonstrated using a variety of example problems.

Greek Letters= correcting factor of the component liquid molar Hayden, J. G., and J. P. O'Connel, "A Generalized Method for Predicting Second Virial Coefficients," Ind. Eng. Chem. Process Des. Deu., 14,3 (1975 (1977). Holland, C. D., "Multicomponent Distillation," Prentice-Hall Inc., Englewood Cliffs, NJ (1963). Holland, C. D., and P. T. Eubank, "Solve more Distillation Problems. Part 2: "Partial molar enthalpies calculated," Hydrocarbon Processing, 53, 11 (1974). Holland, C. D., and P. G. Pendon, "Solve more Distillation Problems. Part 1. Improvements give Exact Answer," Hydrocarbon Processing, 53,7 (1974). Holland, C. D., and M. S. Kuk: "Solve more distillation problems. Evaluate existing columns," Hydrocarbon Processing, 54,7 (1975). Holland, C. D., G. P. Pendon, and S. E. Gallum, "Solve more distillation problems. Part 3: Application to absorbers," Hydrocarbon Processing, 54,l (1975) 27,1197 (1972). Wang, J. C., and G. E. Henke, "Tridiagonal matrix for distillation," H ydrocarbon Processing, 45,155 (1966). A Residence-Time Model for Trickle-Flow Reactors Incorporating Incomplete Mixing Stagnant RegionsA model for the liquidphase residence time in a trickle-flow reactor has been derived and experimentally verified using a tracer input. The model, termed the Ideal Plug Flow Stagnancy Model, postulates that the prime liquid-phase dispersive mechanism in such reactors is the interchange between the dynamic and stagnant regions. Unlike previous models, however, it does not require the assumption of perfect mixing in the stagnant zones. While the results of the study confirm that the mixing is incomplete, they show clearly that back mixing rather than molecular diffusion is the dominant exchange mechanism. SCOPETrickle-bed catalytic reactors find applications in situations where it is necessary or expedient to contact a gas and a liquid phase in a fixed-bed reactor. Such reactors are usually operated in the cocurrent mode to allow high flowrates of liquid and gas, which would cause flooding in countercurrent situations. Of course, cocurrent operation implies that the gas-liquid transfer resistance is not rate-limiting. The boundary between the gas and liquid phases is not fixed, but fluctuates in a highly complex manner as the fluids interact in finding their way through the Dacked bed.Kin-Mun Kan is presently at the