Fractionation of softwood fiber (TMP) using a rotating cone

a rotating cone was used to fractionate fibers from a 100% softwood pulp at a consistency of 0.95% +/- 0.02%. The rotating cone fractionators used in this study had two unique features: (a) their surfaces were constructed fro m a sieve mesh, thereby introducing a "rough" surface, and (b) the point of feed delivery was offset from the cone's axis of rotation. Six fractions w ere collected at different angular positions in a specially designed collec tion assembly. Fractionation performance was enhanced by aligning the first collection zon e with the dispersed spray originating at the transition boundary on the ri m of the cone. The design parameters of the cone (surface roughness, cone a ngle, and cone diameter) were studied in detail. The design of the feed dis tributor (shape and opening area) was also studied. Results showed that the best fractionation performance was obtained using cones with an angle of 3 0 degrees made from 20-mesh screens. A large, elliptically shaped feed dist ributor gave the best fractionation performance. The results suggest the po ssibility of scale-up based on constant tip speed at a given flow rate.