An all-vanadium dual circuit redox flow battery is an electrochemical energy storage system capable to function as a conventional battery, but also to produce hydrogen and perform desulfurization when surplus of electricity is available by chemical discharge of the battery electrolytes. The hydrogen reactor chemically discharging the negative electrolyte has been designed and scaled up to kW scale, while different options to discharge the positive electrolyte have been evaluated, including oxidation of hydrazine, SO2 and H2S. The system is well suited to convert sulfur dioxide and hydrogen sulfide to harmless compounds while producing hydrogen, with overall system efficiencies from 50 to 70 % for hydrogen production.