Analysis of mechanically agitated fluid-particle contact dryers

Incorporation of agitation to spouted and fluidized bed dryer result in sig nificant increases in the drying capacity (Q(s)), although product retentio n persist, which is reduced by increasing the air flow. The physical phenom ena occurring in these dryers with several liquid substrates was analyzed a nd the residence time distributions (RTD) were obtained by the use of dye t racers. The residence time (tau) was found to be a function of the rate of agitation (n) and reaches a minimum at n = n(opt), which was characteristic for each type of substrate, and where maxima also appeared for the drying capacity (Q(s) = Q(smax)) and the heat transfer coefficient (Nu(p) = Nu(pma x))The RTD can be modeled by series of consecutive dryers and a modified Va nderschuren and Delvosalle model can be employed to calculated moisture of the dry product.