(140e) Miniaturization of Metallic Micro-Separator/Classifier and Its Application to Emulsions

Applicability of a micro-separator/classifier, whose structure was originally proposed at IMRET7 (Ookawara, et al., 2003, 2004), to an oil-in-water emulsion is experimentally examined in this paper. The metallic micro-separator/classifier, whose width and depth of the main microchannel were originally 200 and 150 microns in the previous study (Ookawara et al., 2005), is further miniaturized for performance intensification. All the dimensions of the functional parts are proportionally reduced by a 1/2. The new device, which is fabricated by means of photolithography and diffusion bonds (Dai Nippon Printing Co., Ltd.), has six built-in curved microchannels each with a bifurcation at one end. For the feed emulsion, a small amount of vegetable oil is dispersed in deionized water with surfactant using an ultrasonic homogenizer. The emulsion is fed into the microchannels and is discharged from the inner and outer branches that form the bifurcations. The numerical size distribution (NSD) of oil droplets in the feed and discharge is measured by a particle size analyzer. The polydisperse NSD of the feed emulsion typically falls into the range of 0.5 to 50 microns. In this study, it is assumed that total droplet number density is proportional to the absorbance of the emulsion regardless of the NSD. The reduced grade efficiency and the grade purity coefficient are evaluated based on the droplet number density, NSD and flow rates in the inner and outer branches. It is found that both cut-size and pressure loss are much smaller than those of existing hydrocyclones. It can be concluded, therefore, that the miniaturized micro-separator/classifier is applicable to liquid-liquid separation of emulsions with the intensified separation efficiency.

[Acknowledgements]

This research was partially supported by a Grant-in-Aid for Scientific Research (A) (No. 17206079) from the Japan Society for the Promotion of Science (JSPS). The authors are most grateful to Dr. David Street for valuable advice on the present study.

[References]

[1] Ookawara, S., Higashi, R., Street, D., Ogawa, K., 2003, 2004. Feasibility study on concentration of slurry and classification of contained particles by microchannel. Book of Abstracts of 7th International Conference on Microreaction Technology, Lausanne, Switzerland, 231-233, (2003), Chemical Engineering J. 101, 171-178 (2004).

[2] Ookawara, S., Oozeki, N., Ogawa, K., 2005. Experimental Benchmark of a Metallic Micro-Separator/Classifier Compared with Representative Hydrocyclone. IMRET8 in 2005 AIChE Spring Meeting, Atlanta, USA, 129g.