Synthesis of augmented biofuel processes using solar energy

A method for synthesizing augmented biofuel processes, which improve biomass carbon conversion to liquid fuel (η_carbon) using supplemental solar energy as heat, H₂, and electricity is presented. For a target η_carbon, our method identifies augmented processes requiring the least solar energy input. A nonconvex mixed integer nonlinear programming model allowing for simultaneous mass, heat, and power integration, is built over a process superstructure and solved using global optimization tools. As a case study, biomass thermochemical conversion via gasification/Fischer–Tropsch synthesis and fast‐hydropyrolysis/hydrodeoxygenation (HDO) is considered. The optimal process configurations can be categorized either as standalone (η_carbon ≤ 54%), augmented using solar heat (54% ≤ η_carbon ≤ 74%), or augmented using solar heat and H₂ (74 ≤ η_carbon ≤ 95%). Importantly, the process H₂ consumption is found to be close to the derived theoretical minimum values. To accommodate for the intermittency of solar heat/H₂, we suggest processes that can operate at low and high η_carbon. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2533–2545, 2014