Wind tunnel validation of a model for high pour rate pneumatic cane cleaning systems

This paper reports on the experimental validation of a mathematical model of the process of separation of trash and leaves from cane billets during pneumatic cleaning. It forms part of an on-going study aimed at establishing the relationships between fundamental mechanisms which govern the performance of pneumatic cane cleaning systems. Wind tunnel measurements of collection efficiencies and photographic trajectory observations were obtained as a function of variations in air flow rate, trash-tobillet weight ratio, launch velocity, depth of cane bed and billet length. Trends predicted using the particle interaction model were shown to compare well with measured values. Both predicted and photographically observed particle trajectories indicate that the separation of trash from Cqne is a diffusion-like process with little evidence of impenetrable blockage of one particle type by the other. The implication of this blockage phenomenon with regards to achieving higher efficiencies by increasing the cleaning system size is that such gains may be limited primarily by the practicalities of maintaining a uniform air velocity in the extraction chamber at high pour rates.