An environmentally friendly method for electrochemically regenerating alkali-sorbent (NaOH) and recovering sulfur in the flue gas as H2SO4, while producing H2 as a clean energy source from flue gas desulfurization (FGD) residuals in an electromembrane reactor, was proposed in this article. To optimize and improve the performance, the optimal operating conditions were deduced from the numerical simulation and validated using experimental data. Under the optimized conditions, the current efficiencies of alkali-sorbent regeneration and H2SO4 reached 84 and 87%, respectively, which is comparable to those obtained in the chlor-alkali industry. Therefore, this method has the potential to be scaled up. If this technology is integrated into an existing FGD facility, the money-consuming chemical process could be transferred into a renewable resource and clean energy conversion process. (c) 2014 American Institute of Chemical Engineers