(271f) A Novel Approach to Preliminary Design and Performance Analysis of Membrane Reactors

To optimally handle a reactor design duty for an existing or newly developed process, an engineer should properly consider the effects of numerous process variables such as operating temperature, pressure, feed composition, etc. on the reactor performance. On the other hand, for a typical reactor synthesis problem, in order to have an optimum performance-set of conversion, selectivity, yield and the required reactor dimensions, effect of all those variables should be appropriately evaluated in their wide possible range of variations via a comprehensive objective function. Therefore, exerting an optimal reactor design is obviously a challenging task, as it represents a complex multi-objective and multivariable optimization problem. In this manner, a quick directing the design method towards the optimal range of operating conditions, improves the reactor and plant design efficiency considerably.

Reactor synthesis duties for many important processes in chemical engineering requires comprehensive and efficient analysis tools to cope with their complex reaction network. Oxidative coupling of methane (OCM) which regains attentions nowadays is one of these processes. In this process, dealing with the huge amount of reported kinetic data and different proposed reactor concepts requires an efficient optimization approach. The main contribution of this work is to create such a general, comprehensive and efficient tool in order to consider the effect of different process variables on the reactor design and optimization. It should be emphasized that this approach is distinguishable from the conventional reactor design approaches, where either multi-scenario generation is followed or the effect of manipulation of one variable at the time would be studied.

In the proposed approach the optimality of the achievable reactor performance is analysed for the simultaneous manipulation of two independent variables along the effect of different sets of selected dependent variables. In this way, it is possible to represent effects of two independent variables, for instance, temperature and feed composition on the yield, along with the corresponding required reactor length and conversion simultaneously. Moreover, a graphical representation makes it possible to analyse the feasible and optimal performance range corresponding to the effect of the several dependent operating variables in a quick and straightforward approach.

In this work, the achievable performance in case of desired-product selectivity, yield and conversion are evaluated systematically in order to find the optimum range of operation for the OCM process. This approach is applied for a plug flow reactor, a conventional porous packed bed membrane reactor and a proposed pack bed membrane reactor using three different types of catalysts in the wide range of operating conditions. The results show that tracking the optimum area of operation has a monotonic direction under some range of operating conditions, whereas it reflects a qualitative trade-offs under some other ranges of operating conditions. For all investigated reactor concepts and catalysts, the likelihood of optimal operating conditions are found, and the best corresponding performance for all of them are reported.