A novel hydrodynamic separation technology for algae dewatering

Details

Event The 2nd International Conference on Algal Biomass, Biofuels and Bioproducts

Authors

Hsieh, Huangpin B.
Kole, Ashutosh
Armin R. Volkel
Technical Publications
June 10th 2012
This paper describes a novel hydrodynamic separation technology (HDS) for algae dewatering. HDS uses customized fluid flow patterns in a curved channel to focus suspended particles into a concentrated band and achieves separation by placing a splitter near the channel exit. Two categories of algae based on size differences were dewatered with two versions of HDS devices. Spirulina, often used as a food supplement, has a cork-screw shape with 30-50 m diameter and 200-300m length, separates well with an HDS particle separator device. Starting from a concentration of 0.8 g/l, we achieved a 6-fold increase to 4.6 g/l with over 97% harvesting efficiency, using an HDS device that has an 80:20 split ratio. An increase in concentration can be obtained with a second HDS connected in series to further reduce the total concentrate volume to less than 5%. When the size of the algae is smaller than the cutoff of separation for HDS (15m), polymer is used to promote flocculation. S. dimorphus, an algae species that is small (<10m), was separated by adding a flocculent (chitosan) to promote growth of larger aggregates. The resulting large flocs were separable with a low pressure (1.2psi) HDS floc separator, which also preserved the integrity of the loose aggregates. We also present a case where algae used for organic matters degradation in a wastewater pond was successfully dewatered and concentrated 10-fold in a single HDS separation. The focusing and separation of particles by HDS is primarily due to a combination of hydrodynamic forces (drag, virtual mass, and shear), which causes a size rather than density dependent separation. This enables concentration of particles with densities equal or close to that of their surrounding fluid without using significantly amount of energy, such as a centrifuge, or chemicals, lowering the cost of algae dewatering in biofuel production.

Citation

Hsieh, H. B.;Vlkel, A. R.; Chang, N. E.; Melde, K.; Kole, A. A novel hydrodynamic separation technology for algae dewatering. The 2nd International Conference on Algal Biomass, Biofuels and Bioproducts; 2012 June 10-13; San Diego, CA.

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