The development and application of a novel non-polar oil recovery process utilizing a non-dispersive solvent extraction method to coalesce and recover oil from a bio-cellular aqueous slurry is a needed process. The process could apply to recovery of algal oil from a lysed algae slurry, recovery of omega fatty acids from a bio-cellular aqueous feed, recovery of beta-carotene from a biocellular aqueous feed and for the removal from produced water in oil production and similar applications. The technology utilizes a microporous hollow fiber (MHF) membrane contactor. The novel recovery process can be coupled to a collecting fluid (a non-polar solvent such as heptane, a biodiesel mixture or the previously extracted oil) that is circulated through the hollow fiber membrane. In cases where the biodiesel mixture or the previously extracted oil is used, the solvent recovery step (e.g., distillation) can be eliminated.
Researchers at The University of Texas at Austin have developed a method which involves recovering algae oil from lysed algae concentrate using hydrophobic MHF membrane with or without the use of a solvent. While algae make oil, there is no simple, economical method for extracting the oil directly from an aqueous slurry. Drying algae is usually needed for solvent extraction, and the biomass is exposed to toxic solvents. Other methods such as supercritical extraction are uneconomical for commodity products like fuel. Solvent extraction is somewhat promising but requires distillation of an extract to separate the solvent from the oil. Also, a steam stripper is usually required to recover the residual solvent dissolved/entrained within the exiting algal concentrate. The solvent extraction technique requires a contactor/phase separation equipment, a distillation system, and a steam stripper, along with heat exchangers, surge tanks, pumps, steam, and cooling water.
The invented process requires only a membrane system with pumps; no steam or cooling water is required. The technique does not require intimate contact between the lysed algae concentrate and solvent. The use of a hydrophobic MHF membrane provides a non-dispersive method of coalescing and recovery of the algae oil. The lysed algae concentrate is fed on the shell side while the algal oil is fed on the fiber side. The algal oil acts to sweep and then remove the coalesced oil within the tube surface of the hollow fibers. A natural fatty acid may be added to the algae concentrate to minimize fouling on the fiber outer surface and increase oil coalescence. The invention eliminates the need of a distillation system or a stripper to recover the solvent thereby reducing the capital and operating cost of the overall oil recovery process.
The novel process could be used in a wide variety of commercially significant applications such as:
- recovery of released or secreted algae oil from an aqueous mixture
- recovery of insoluble hydrocarbon and hydrocarbon-rich molecules from aqueous mixtures
- recovery of omega fatty acids from an aqueous mixture
- recovery of beta-carotene from an aqueous mixture
- removal of oil from produced water in petroleum exploration/production