This paper discusses plant-wide control system design of the wet sulfuric acid (WSA) process, which is part of an integrated gasification combined cycle power plant. The regulatory control structure, which ensures energy efficiency and operational stability, was designed by addressing the requirements and constraints of each key unit in the process. We used sensitivity analysis and simple stoichiometric calculation to obtain optimum set points for the controlled variables, which has a direct effect on the energy usage and production rate in the WSA process. In this work, we proposed several controller schemes that ensure efficiency and stability of the WSA process. The results of this work will contribute to improving the process efficiency, thereby facilitating energy efficient and stable operation of the WSA process. (C) 2017 Elsevier Ltd. All rights reserved.