Multi-scale modelling of an electrodialysis with bipolar membranes pilot plant and economic evaluation of its potential

Abstract

Sodium hydroxide and hydrochloric acid are widely used chemicals in different industrial sectors. To minimize costs and risks associated with transportation, handling and storage, these hazardous chemicals can be produced in situ employing electrodialysis with bipolar membranes (EDBM). This work presents a multi-scale model capable of simulating large scale EDBM units with complex stack configuration (i.e., internal staging) that can be used to design and optimize the process. The model was validated in two different process configurations using experimental results obtained from an EDBM pilot plant. Discrepancies between model and experimental results in the range of 2–11 % were obtained. The validated model was used to conduct a techno-economic evaluation adopting the feed and bleed configuration. Results show that current efficiency increases as the current density rises. At 600 A m−2, values of current efficiency between 72 % and 96 % were found for sodium hydroxide concentration in the range of 0.5–1 mol L−1. The levelized cost of sodium hydroxide (LCoNaOH) was evaluated, in the same range of concentrations, demonstrating that values between 280 and 370 € ton−1 can be obtained, fixing the electricity prince (0.1 kWh kg−1) and the triplet specific cost (600 US$ m−2). Moreover, assuming a reduced cost of electricity and triplet to 0.05 kWh kg−1 and 300 US$ m−2, respectively, an absolute minimum of 140 € ton−1 was found for the target 0.5 mol L−1. A double stage EDBM configuration was simulated to show the scale-up potentials of the multi-scale model. A reduction in the LcoNaOH of 10 % was obtained for a target concentration of 1 mol L−1. These results prove the attractiveness of the EDBM technology for producing in situ chemicals.