Due to the depletion of fossil fuels and associated environmental problems, renewable and more environmental friendly energy options need to be explored. Liquid transportation fuels from the conversion of biomass are promising forms of renewable energy. A process simulation describing the conversion of biomass to liquid transportation fuels has been performed in ASPEN Plus. A process superstructure is designed which considers multiple ways for producing gasoline, diesel, kerosene and propylene at varying design/operation conditions. Biomass is dried and gasified to generate synthesis gas, which is converted to a mixture of hydrocarbons via Fischer-Tropsch synthesis (or Supercritical phase Fischer-Tropsch synthesis 1). A wide variety of products of various qualities can be produced depending on the method used to upgrade the Fischer-Tropsch hydrocarbons, which includes conventional upgrading and ZSM-5 upgrading 2. For wax upgrading, in addition to mild hydrocracking, fluid catalytic cracking, which produces a propylene product besides gasoline and distillate, is also investigated. This study first investigates the product distribution associated with conventional Fischer-Tropsch synthesis and supercritical phase Fischer-Tropsch synthesis. The economics and environmental impacts of mild hydrocracking and fluid catalytic cracking for upgrading wax are analyzed next. Based on rigorous simulation, this study identifies the optimal configurations and the relevant optimal operating conditions under different scenarios (i.e. maximize liquid fuels production, minimize CO2 emissions, and maximize the propylene production).
1. Elbashir, NO; Roberts, CB. Selective control of hydrocarbon product distribution in supercritical phase Fischer-Tropsch synthesis. Abstracts of papers of the American Chemical Society, 2004 (228) U177-U178.
2. Mobil Research and Development Corporation. Slurry Fischer-Tropsch/Mobil two stage process of converting syngas to high octane gasoline; Mobil Research and Development Corporation: Paulsboro, NJ, 1983; U.S. DOE Contract DE-AC22-80PC30022.
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