FLUIDIZATION OF POTATO STARCH IN A STIRRED VIBRATING FLUIDIZED-BED

A novel gas-solid reactor for cohesive C-powders such as potato starch is introduced, designed and characterized, the so-called stirred vibr ating fluidized bed. The effects of a sinusoidal vibration of the gas distributor and/or stirring of the bed are investigated. The fluidizat ion index, bed expansion, torque and visual behaviour of the bed are d etermined as a function of air velocity, bed height and moisture conte nt of the starch, stirrer type and speed and vibration frequency and a mplitude. For a potato starch bed of 0.76 m initial height and 0.288 m diameter with a moisture content W = 13.1 weight% dry basis, channel formation can be suppressed only if the aerated bed is effectively sti rred: With flat stirrer blades this can be realized for stirring speed s above 1.67 rps provided the interblade distance is below 124 mm. Eve n then, the bed consists of agglomerates (flocks) of starch. Alternati vely, vibration of the gas distributor of the aerated bed at best resu lts in channel elimination in the lower part of the bed only. Sufficie nt vibration, however, can destroy starch agglomerates even at the sur face of a bed of 0.76 m. By simultaneously applying both vibration and stirring of the aerated bed, it is possible to eliminate both channel ling and starch agglomeration. Even homogeneous fluidization is possib le. Optimal combinations of stirring and vibration parameters are repo rted for various bed heights and moisture contents.