Optimization of batch electrodialysis for hydrochloric acid recovery using orthogonal collocation method

Electrodialysis (ED) is a feasible method for acid recovery where it can separate and also concentrate the separated acid involved from the feed stream. To ensure maximum ED performances, the optimum operating conditions must be obtained. In this work, a dynamic optimization i.e. the orthogonal collocation method was applied to obtain those optimum operating conditions. The mathematical model of the ED for this case study has been taken from Rohman et al. [1] and the dynamic optimization problems were solved using the dynopt code package [2]. Five objective functions were considered in this study: minimize process time (P1), minimize the dilute concentration (P2), minimize energy consumption (P3), maximize degree separation (P4) and maximize operation profit (P5). From the simulation results, the control trajectories of P5 was chosen to be the most effective control operation in order to achieve the minimum process time for 99% degree of separation. The control trajectory achieved was reliable and practical. Moreover, the process time achieved for P5 was 51.6% faster than the P2, 60.7% faster than P3 and 7.9% faster than P4. The effect of different aspects of optimization towards ED performances was also studied.

Research highlights
► Time, HCl concentration, energy usage, separation degree and profit are optimized.
► The effect of different aspects of optimization towards ED performances is studied.
► For 99% degree of separation, the time required varies from one case to another.
► Control trajectory of maximum profit case is the most effective control operation.