THEORETICAL AND EXPERIMENTAL INVESTIGATION OF BULK MATERIAL FLOW IN A PNEUMATIC SEPARATION CHAMBER FOR CHOPPED SUGARCANE

A two-phase flow study of pneumatic separation of chopped sugarcane components in a countercurrent flow chamber was conducted. Flow parameters were experimentally measured and a theoretical model for the motion of chopped sugarcane components was developed.;The dominant factors influencing the overall performance of the pneumatic separator of sugarcane components are the ratio of the particle directional variation in velocities and the air velocity in the chamber. For minimum loss of billets the mixture proportion by weight is a factor to consider. When the proportion of billets and tops is 83.0 and 10.3 percent respectively and the mean air velocity is 15.9 m/sec (52.1 ft/sec) only 0.07 percent of the billet will be lost and 10.0 percent of the tops will be removed by the pneumatic separator. For all feed and loading conditions, all of the detached leaves were removed.;The air velocity, the feed rate and the voidage were correlated for sugarcane pneumatic handling at the onset of choking. For the system tested a mean feed rate equal to 4.0 Lb/sec-ft('2) (19.7 Kg/sec-m('2)), will require a minimum air velocity equal to 40.3 Ft/sec (12.3 m/sec) for dispersion. At these values the voidage in the duct is 0.99. Below this voidage value and at the specified air velocity choking will occur.;The overall drag coefficient for billets was in the range 0.96 to 0.49, averaging 0.64. The values for tops that have a more rugged surface ranged from 0.92 to 0.47, averaging 0.69. The drag coefficients for leaves ranged from 0.65 to 0.35, averaging 0.49.;Separation efficiency of 55 (+OR-) 5 percent could be achieved at a feed rate equal to 11.3 Kg/sec. (25.0 Lb/sec.) and a loading ratio equal to 29.8. At high feed rates the proportion of tops that accompanied the clean cane for further processing increased. High top separation and thus a high system separation efficiency will be achieved if air velocity is above 15.0 m/sec but below 25.0 m/sec. This will ensure that an appreciable amount of tops will be removed since their terminal velocity is below 15 m/sec. In this range billet loss will be minimum since billet terminal velocity exceeds 15.0 m/sec and is close to 25.0 m/sec.