DRYING OF RESIDUAL GRAINS OF ANNATTO IN A HEAT ACCUMULATOR DRYER COMBINED WITH DRYING IN A SOLAR DRYER

摘要

This paper is a study of the drying process of residual grains ofannatto in a heat accumulator dryer during the night combinedwith a solar dryer during the day. Different mathematical modelswere adjusted regarding experimental data for the dryings andfor determining the effective diffusivity for all the processes. Thegrains were divided into two groups; one with oil, reproducing theconditions of the grains after the oily extraction of bixin, and anothergroup without oil. The drying of the annatto grains of during the nightwas performed with a heat accumulator dryer, which consisted ofsolar panel systems that heat water, which is transferred to a thermaltank where it is used as a heat source; during the day a solar dryerwas used. Residual grains of annatto with an initial moisture at~18 % w.b. were dehydrated until they reached ~5 % w.b. Combineddrying using a heat accumulator dryer and a solar dryer proved tobe effi cient, with samples presenting lower amounts of moisturecompared to the control samples. Midilli’s equation was consideredthe best model to represent the kinetics of drying residual grains ofannatto both with and without oil. Grain samples presented effectivediffusivity in the order of 10-9 m2 s-1.