GAS SEPARATION USING MEMBRANES .1. OPTIMIZATION OF THE SEPARATION PROCESS USING NEW COST PARAMETERS

This is the first in a series of papers presenting new concepts for th e development of membranes for gas separation. In this paper two new c ost parameters, which are useful for costing and optimization of membr ane gas separation systems, are described. The new parameters, cost pe rmeability and effective selectivity, can be used to show the directio n to be taken in membrane research and development. The new parameters are shown to predict accurately the cost of membrane separation plant by correlating bids from membrane plant suppliers using the new param eters with cross-flow design equations. The parameters are used to opt imize the membrane gas separation of hydrogen and carbon monoxide for two commercially available membrane systems in a process to manufactur e acetic acid. The membrane separation is compared with the currently used method, cryogenic flash distillation. Economic evaluation methods are developed to compare different separation methods so that the pro cess as a whole can be optimized. The evaluation shows that, for membr ane gas separation, it is important to find the optimum degree of sepa ration; when membrane separation is evaluated at the separation specif ication for the established cryogenic method, membranes are not compet itive; however, when the process is optimized for membrane separation, the cost of separation reduces to less than 60% of the cryogenic sepa ration.