Toward Optimal Synthesis of Renewable Ammonia and Methanol Processes (RAMP)
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2018 Elsevier B.V. The conversion and storage of renewables into useful and transportable energy vectors is an outstanding challenge in transitioning to a sustainable energy future. Ammonia and methanol are two promising vectors due to their proven production and transportation infrastructures. Individual processes consuming fossil fuels have been improved and optimized over the years, but there is no clear path forward for incorporating renewables or their coproduction. In this work, we introduce a deterministic global optimization-based process synthesis framework to determine the minimal cost for the coproduction of ammonia and methanol from hardwood biomass and natural gas. This will provide the guideline for future studies into solar and wind energy. A process superstructure with several competing technologies and integration routes is modeled and described. A customized branch-and-bound algorithm is used to solve the resulting mixed-integer nonlinear nonconvex optimization model. Results indicate that the biomass incorporated processes are cost-competitive with pure fossil fuel based processes, and the integration of ammonia and methanol production leads to 4-7% savings.