ABSTRACT
A centrifuge was conceived and tested especially for the separation of oil as it is usually dispersed in the bilge and ballast water of ships. The centrifuge is unusual in having predominantly axial flow allowing comparatively high throughput and low speed. It has both primary and secondary stages of separation incorporated into the design and is thus capable of operating with high input concentrations. The device was tested in the laboratory using mixers in a storage tank and a centrifugal pump to disperse up to 8 percent oil in water.
Effluent concentrations in the range of 10 ppm were obtained with inputs containing 1000 ppm of No. 2, No. 4 and Nigerian Crude Oils. At higher concentrations ranging up to 58,800 ppm for No. 2 oil and 18,900 for No. 4 oil the effluent contained less than 100 ppm. Centrifuge performance on No. 2 and No. 4 oils containing ten percent Gamlen D was lower than with pure oils. Coalescence occurred but produced drops smaller than with pure oils requiring a modification to the separator design. The input and output oil droplet size distributions were measured using the Coulter particle counter. This permitted an evaluation of separator performance as a function of the drop size content of the oil dispersion and a rational assessment of the design method and its application to the development of future prototypes.
This research effort was jointly sponsored by the U.S. Maritime Administration, Naval Ship Systems Command, and U.S. Coast Guard.