(587f) Aspen Simulation for the Hydrothermal Liquefaction of Algae to Generate Fuels and Chemicals

In recent years, microorganisms, including algae, yeasts, and bacteria, have been studied as potential feedstocks for hydrocarbon-based fuels and chemicals to displace petroleum in an ever-increasing market for fuels and chemicals.  Cultivating these organisms using wastewater streams takes advantage of aqueous systems that are high in nutrient and carbon resources and makes for a cheaper feed than farm grown, single strain algae.  In addition, most wastewaters (municipal and industrial) are generally mineralized using microbial activity.  Algae, in particular, have relatively high growth rates, reduce CO₂ emissions, and can be cultivated to produce large lipid fractions.  
            In this work, conversion of algae using hydrothermal liquefaction (HTL) is proposed.  HTL is a non-traditional “catalytic” approach to converting algae to biocrude and other chemical compounds through medium temperature (280 - 370°C), high pressure (10 – 20 MPa) reactions in aqueous conditions.  HTL eliminates the need for dewatering algae before reaction, as the water is both a reactant and a “catalyst”, thus saving energy in comparison to other biomass conversion techniques.  The resulting biocrude is readily fractionated from its aqueous components. This study employs an Aspen model for the process development from algae growth through the HTL reaction and finally separation of the various fractions, including decantation, distillation, and solvent-solvent extraction. The process has been optimized for reduction of hazardous wastes and for energy savings using heat integration techniques.