OPTIMAL POTENTIAL-TIME PROGRAMMING IN ELECTROCHEMICAL BATCH REACTORS

In an electrochemical stirred batch reactor where a series of two reac tions A <-> B <-> D takes place, two practical dynamic optimization pr oblems were analysed. More specifically, the optimal profiles of elect rode potential which achieve the following performances are determined : (i) maximize the final concentration of product B in a specified bat ch period t(f) and fixed final conversion rate of product A; (ii) mini mize the terminal time tf required to reach a specified selectivity of B. The reaction considered here is the reduction of oxalic acid (A) t o glyoxilic acid (B) followed by the reduction of glyoxilic acid to gl ycollic acid (D). The optimization is carried out by means of Pontryag in's maximum principle and the computational technique used is the con trol vector iteration method. The influence of the liquid/solid mass t ransfer coefficients is mainly investigated. It is shown that, for low conversion rates, the optimized and static operating modes achieve th e same performances. For high conversion rates however, the performanc es obtained in realistic operating conditions by applying optimized el ectrode potential profiles, are substantially improved with respect to best static electrode potential values.