DESIGN AND CONTROL OF FIXED BEDS AFFECTED BY CATALYST DEACTIVATION (OPTIMAL)

On-line measurements of temperature and concentration and the global rate at any reference state of catalyst can be used to estimate a measure of catalyst deactivation. A feedback control policy is obtained from this measure of catalyst deactivation for manipulating the reactor outlet conversion or yield in any desired manner. This feedback control enables one to obtain the desired conversion or yield without any knowledge of deactivation kinetics, and the results are applicable to any type of deactivation. The feedback control policy has been verified by experiment based on ethylene oxidation reactions over a silver catalyst using a laboratory shell-and-tube reactor. Excellent agreements have been reached between the theory and the experiment.; The problem of finding the optimal piecewise control policy has been formulated as multivariable optimization problem. The optimal policy is one of increasing conversion. The constant conversion policy corresponds to the limiting case where the number of piecewise steps approaches infinity. This optimal piecewise control is suitable for on-line implementation in conjunction with the on-line estimation of the extent of catalyst deactivation. An optimal continuous control policy for parallel and reversible reactions has also been solved using the technique of calculus of variations. It is shown that a direct substitution method is more efficient than the commonly used method of applying the Pontryagin maximum principle.; The optimal control policies can easily be taken into consideration for reactor design. This combination of process design and control with due consideration of catalyst deactivation for both is shown to result in a substantial improvement of the reactor performance.