Optimal superstructure-based design and synthesis of hydrocarbon biorefinery via fast pyrolysis, hydrogen production and hydroprocessing pathway

This paper is concerned with the process design and synthesis of hydrocarbon biorefinery under economic and environmental considerations. A superstructure is developed that consists of fast pyrolysis, bio-crude collection, hydroprocessing, and hydrogen production sections. Multiple process alternatives are included in the superstructure for process optimization. Three hydrotreating feed options with different bio-crude ratios and hydrotreating catalysts are placed; natural gas steam reforming, bio-crude steam reforming and biomass gasification are employed for hydrogen generation. A bi-criteria mixed integer nonlinear programming (MINLP) model is proposed to maximize the economic performance measured by the net present value (NPV) and minimize the environmental impact quantified by global warming potential (GWP). The bi-criteria MINLP model is solved with the ε-constraint method, and the resulting Pareto curve reveals the trade-off between the economic and environmental behaviour of the process. The two "good choice" optimal designs indicate a unit cost of $3.43 and $5.26 per gallon of gasoline equivalent (GGE), corresponding a net greenhouse emission of 1.95 and 2.04. kg CO2-eq/GGE, respectively.