Production of hydrogen from algae: Integrated gasification and chemical looping

Due to their high potential and beneficial characteristics, algae is considered as very promising energy source in future. In this study, an integrated conversion system of algae to hydrogen is proposed with the objective of high total energy conversion efficiency. The proposed system mainly covers algal drying, gasification, and chemical looping. To facilitate optimum heat circulation throughout the proposed system, enhanced process integration is adopted. It combines exergy recovery and process integration technologies in order to achieve a wasted energy, hence the total energy efficiency can be improved significantly. In the proposed system, to convert algae to hydrogen, steam gasification and syngas chemical looping are integrated as the main conversion. Iron oxide is employed as the oxygen carrier, and is circulated among the reactors in the chemical looping module. Process modeling and calculation is performed using ASPEN Plus, and the total energy efficiency, including hydrogen production and power generation, is evaluated. Several operating parameters including target moisture content in drying, steam-to-biomass ratio in gasification, and chemical looping pressure, are observed. From the results, it is shown that the proposed system is potential to convert algae to hydrogen with high total energy efficiency, which is higher than 70%. Both target moisture content and steam-to-biomass ratio influence strongly the total energy efficiency. On the other hand, chemical looping pressure show insignificant effect to total energy efficiency.