Electrochemical membrane recovery of halides from waste hydrogen halide streams

A novel gas phase electrochemical membrane process has been developed for the recovery of halides from waste hydrogen halide streams. Using a molten salt as all electrolyte, the process first decomposes hydrogen halides into their elemental constituents. Furthermore, the constituents are then separated into a hydrogen enriched waste stream and a molecular halogen (or hydrogen halide) product stream. Removal and current efficiencies of greater than 90% have been achieved in free electrolyte trial using hydrogen chloride process streams. Similar values (with current densities as high as 1.1 A/cm(2)) have been obtain for single cell trials using hydrogen bromide process streams. The salient features of this system include one step separation using non-exotic membrane, electrode, and housing materials resulting in an operating cost of under $0.02/lb(m) of bromine produced and under $0.04/lb(m) of chlorine produced (based on a preliminary economic analysis and conservative cost of electricity at $0.05/kwh).