Furthermore, if the cycle time is too short, the bed sees a mean inlet feed pressure, and no separation occurs. Likewise, an infinitely slow cycle time means steady operation, and again, no separation. Thus an optimum cycle time exist;. The objectives of the optimization can be either product purity or capacity, or a combination of both.The scope of Part I of this paper is the determination of the experimental optimum pressure wave form and cycle time for the methane-nitrogen-molecular sieve system. The theory of Part I1 indicates that the family of square waves encompasses the optima for a system in dynamic equilibrium. Therefore, the variables of cycle time, yo of time at maximum feed pressure, no feed flow, and minimum (exhaust) feed pressure were experimentally explored. Other quantities, such as bed length and diameter, feed composition, temperature and molecular sieve parameters, were not varied.The model of this system was previously developed for the in:tantaneous equilibrium assumption and is employed here. The theoretical optimization procedures were both an analysis of the model partial differential equations and an extension of the procedure of Horn and Lin, based on the Pontryagin Maximum Principle.Hence, the scope of this work includes the experimental

and higher flow rates, for which adsorption rate limitations may become significant. Second, unless the permeability is constant, the optimal timing of the control sequence will vary and unless corrections for this are made in the control, suboptimal operation will result. To avoid this problem, adsorbent particles that resist abrasion and maintain a constant flow resistance should be used. The round particles used in this research were found to be satisfactory.Another factor that affects the operation of the adsorber is the length of the column. Unlike most chemical process equipment, decreased length increases the capacity of this system (within certain limits). To achieve the same product composition for shorter lengths, higher frequencies are required. Since the optimal frequency increases as the inverse of the square of the length (Kowler, 1969), shorter lengths would require faster operation. This result is valid for flow rates for which adsorption rate limitations can be neglected. In fact, since the optimal frequency increases so quickly as length decreases, the performance of the controlling solenoid valves may limit the achievement of the optimal frequency for shorter lengths. Despite these limitations, it is clear that attempts should be made to use shorter lengths of column to increase capacity and decrease equipment costs at the same time.Having found (theoretically) the optimal feed bound-ary cyclic control of (maximum pressure, zero flow, minimum pressure) and having gained a better understanding of the design parameters, a cyclic adsorption system can now be more properly designed. For the separation of gas mixtures for which there exists an adsorbent with a high relative volatility, the cyclic adsorption process may well be of commercial value.