The influence of flow maldistribution on the performance columns containing random packings: a model study for constant relative volatility and totalreflux

The effect of maldistribution of liquid and vapor in a column with random p acking is terms of its effect on the specific pressure drop (Delta p/H),(2 phi), the HETP, and the total accomplish a given separation. A percolation model for the pressure drop has been used where, discussed and quantified i n pressure drop Delta p(2 phi), required to the hydraulic calculations pres ented although other available models could also be applied. The HETP at to tal reflux was estimated with the Fenske equation. These particular simulat ions demonstrate that the specific pressure drop (Delta p/H)(2 phi), the RE TP and the total pressure drop Delta p(2 phi),, are sensitive functions of the degree of maldistribution as well as of the degree of separation desire d. We further demonstrate that local operating line-equilibrium curve pinch es can develop even at total reflux in the presence of maldistribution, and that these pinches further exasperate the reduced column performance due t o the maldistribution alone. Finally, a differential equation relating the liquid and vapor distributions within the column is elaborated. This equati on has as its basis the assumption that the radial pressure gradient within the column is, on average, zero. (C) 1999 Elsevier Science B.V. All rights reserved.