Studies and Investigations related to the Development of a Potato-Rock Separator

Abstract

This thesis reports work on a two-part research towards the development of an improved Potato-rock separator. The work was carried out in the industrial setting of a factory named Allan Equipment (AE) at Prince Edward Island. First part of the work involved improvement of a ‘wave bed’ based separator unit that was developed and built by this company. The second part of the work involved development of a new type of potato-rock separator using fluidized bed principles. In part one, we used fluid dynamics simulation to understand why the existing design of AE gave poor performance and discovered that it is due to non-uniform air flow distribution caused by their current duct layout and air plenum design. CFD simulation suggested change in fan arrangement, which was done by AE in their full-scale commercial unit. Our experiments on this modified unit confirmed the more uniform flow distribution CFD simulation predicted. Since this improvement was not adequate for AE, we used CFD simulation to further evaluate other options. CFD simulation predicted that addition of a perforated plate in plenum chamber could result in more uniform air distribution. AE implemented this change. Our experiment on this unit confirmed the improvements predicted by CFD. AE wanted further modification to have certain velocity distribution above their wave bed. This part of the work was done without simulation but by building plates of different hole size and arrangements. Experiments on these different designs showed the best combination of hole and arrangement to best meet the requirement of AE. In the second part we designed and built a bench scale fluidized bed of sand to explore if bubbling fluidized bed can be used to separate mixture of potato and rocks which are order of magnitude larger than the bed particles. After measuring pressure drop characteristics of the fluidized bed system, we dropped mixture of potato and rocks. We fluidized the bed at different fluidizing velocities and found that such over sized particles can be separated, but the degree of separation is a function of fluidization velocities. We measured the segregation of the particles along the depth of the bed with change in fluidizing velocity. Finally, we found the optimum velocity for these particles. Thus, this work established the potential of development of new type of potato-rock separator based on fluidized bed principles.