DRYING OF BEANS IN INTERMITTENT SPOUTED BED REGIME: ANALYSIS OF ENERGY EFFICIENCY OF THE DRYING PROCESS

摘要

"Carioca" beans, Phaseolus vulgaris L. type, is a grain of high nutritious potential, mainlyrnwith respect to the amount of protein, iron and potassium, as well as carbohydrate, fibber andrnvitamin source. The moisture content of the recently picked beans is too high for goodrnconservation conditions and storage, needing to be dried before packaging. The objective ofrnthis work is the analysis of the drying process of beans in a spouted bed, with intermittentrnconditions of drying air. Experiments carried out in this work consist of two types ofrnintermittent regime: intermittence in the spout, called spouted/fixed bed and intermittence ofrnthe air supply, which was called spouted bed/rest. An Experimental assembly, in laboratoryrnscale, was designed and constructed, containing the dryer, built in acrylic, having a conicalrnbase and a cylindrical column. The factorial planning technique was applied in two levels, tornevaluate the influences of the following process variables: temperature of the drying air,rninitial moisture content of the grains and intermittence time of the air supply or of the fluiddynamicrnregime. Sixteen experiments with intermittent drying of beans were conducted withrnresults of drying curves, drying rates, variation of grains temperature and analysis of thernenergetic efficiency of the drying process. In this paper, the evaluation of the energeticrnefficiencies for each experiment was related to the ones obtained previously in a spouted bedrndryer without intermittence. The energy analysis of the process indicates promising results forrnintermittent conditions, mainly if working with spouted bed/rest type.