Optimal synthesis of integrated process for co-production of biodiesel and hydrotreated vegetable oil (HVO) diesel from hybrid oil feedstocks

Current vehicles use biodiesel and diesel's blends to minimize engine modifications while encouraging the use of renewable fuels. Biodiesel combustion reduces CO2 emissions but has poorer fuel properties than diesel. A promising renewable diesel alternative is hydrotreated vegetable oil (HVO) diesel with diesel-like fuel properties, overcoming the biodiesel limitations. However, HVO diesel processing requires higher capital expenses than biodiesel. In the present work, we defined a synthesis network superstructure to optimize the integrated production of biodiesel and HVO diesel. We identified processing blocks inside the superstructure and defined equipment, operating conditions and yields of each processing block based on literature. After that, we performed individual rigorous simulations in Aspen Plus V8.8 and Aspen Process Economic Evaluator V8.8 for the processing blocks to store conversion, separation, energy and equipment parameters for a fixed processing flowrate. Then, we defined a superstructure as a mixed integer non-linear programming (MINLP) problem coded in GAMS 24.4.6, that minimized the total manufacturing costs per gasoline gallon equivalent under different scenarios, computing also the water used and CO2-Equiv. for comparison purposes. The results showed that the optimal integrated production synthesis path, including hydrogen in-situ production as integration factor, reduced the total manufacturing costs in around 24 % in comparison to the co-production without integration. The novelty of the present work relies on two main points: the process synthesis of a new integrated biodiesel-HVO diesel production superstructure, and the use of a combined rigorous simulation and MINLP-using-simplified-models evaluation approach to relax the rigorous search for the optimal synthesis path.