MEMBRANE PLANTS OF MODULAR DESIGN FOR DIFFUSION-CONTROLLED GAS SEPARATIONS

This paper considers the design of multistage membrane plants operatin g in the diffusion controlled region where gas flux is proportional to the differences in the gas partial pressure across the membrane. The flow inside the modular stages was assumed to be fully mixed and the s tages were connected in a simple countercurrent mode. The design metho d was thus particularly aimed at separations involving inorganic membr anes. A flexible algorithm was used to define the interstage flow sequ ence and the plant was assumed to be built of modules of the same size ; only the number of modules assigned to a stage was allowed to vary. Trial and error was used to obtain convergence of the plant mass balan ce. The criteria for optimisation are discussed. Predictions of module behaviour for the fully mixed and the more realistic plug flow cases are considered in an appendix. Based on this comparison, the applicabi lity of the current design methods for stage cuts above 0.2 is questio nable.