(263a) Process Intensification of Algae Oil Extraction to Biodiesel

Dilute algae are often grown in raceways or bioreactors by photosynthesis using carbon dioxide in flue gas. After being harvested, algae oil must be extracted before being transesterified to biodiesel. This process, which generates a carbon-neutral, renewable, liquid fuel, has been shown to be competitive with other liquid fuel sources (Silva et al., 2014). Herein, we introduce the use of carbon dioxide microbubbles to lyse algae cell walls, releasing triglyceride oils, combined with their transesterification using methanol. Process designs are compared with conventional extraction/transesterification processes, showing the profitability advantages (reduced energy utilization and installed equipment costs) of the proposed intensification processes. At lower temperatures and intermediate pressures, carbon dioxide causes methanol to dissolve in the triglyceride phase and triglyceride to dissolve in the methanol phase, increasing the transesterification reaction rate. This paper presents a 3-reversible reaction transesterification model, coupled with multiphase equilibria (VLLE), for a large-scale, continuous biodiesel process. It introduces an algorithm for solving the steady-state reactor model – to be utilized for optimizing the intensified process in future work.

Silva, E. Soliman, F. Cameron, L.A. Fabiano, W.D. Seider, E.H. Dunlop, A.K. Coaldrake, 2014. Commercial-scale biodiesel production from algae. Ind. Eng. Chem. Res., 53, 5311-5324.