Numerical modeling of the mass transport and chemistry of a simplified membrane-divided chlor-alkali reactor

A numerical model has been developed to predict the local concentrations of chemical species throughout the anolyte compartment in a simplified chlor- alkali reactor with a flow channel defined by a pair of parallel-plate elec trodes. Mass transport by diffusion, migration, and advection has been appr oximated by numerically solving the Nernst-Planck equation for each species , coupled with a set of nonlinear and linear algebraic equations describing the chemistry and electroneutrality. The predicted concentration profiles for protons, chloride ions, chlorine, and hypochlorous acid/hypochlorite io ns exhibit large concentration changes in the membrane boundary layer. The sharp pH increase from a bulk value of 2 to ca. 6 at the membrane would all ow the undesirable local decomposition of hypochlorite to chlorate ions, wh ich are produced in industrial reactors. (C) 2000 The Electrochemical Socie ty. S0013-4651(00)03-106-2. All rights reserved.