Partial drying of high moisture shelled corn using a centrifugal crossflow rotary dryer

The study was conducted to investigate and establish the technical operating conditions appropriate for high speed partial drying of high moisture shelled corn as well as the drying parameters as they affect the technical and quality output using the prototype Centrifugal Crossflow Rotary Dryer. An experiment involving a 3 x 4 factorial experiment in CRD was conducted to determine and establish the effect of drum speed and initial moisture content on grain flow rate and residence time. Likewise, a 3 x 3 factorial experiment in CRD was also undertaken to investigate and determine the performance of the dryer in terms of the technical parameters such as moisture reduction rate, drying time, and number of passes as well as the quality aspect5s like stress crack and germination as affected by temperature and initial moisture content. In both experiment, a yellow corn of the hybrid Pioneer 3228 variety with a purity of 98% after shelling was used as the experimental sample. The drum rotational speed has significant effect on the flow rate and grain residence time. Flow rate increases to maximum value with drum speed up to 100 rpm and decreases with further increase in drum seed up to 110 rpm. The residence time follows the same trend but appears to continue to increase with drum speed up to 110 rpm. This was observed for all levels of initial moisture content of grains. The use of higher drying temperature of 100°C generally yielded higher moisture reduction rate and shorter drying time and passes. The negative effect of high drying temperature on stress crack formation and germination was confirmed. Stress crack was observed to be highest at 100°C drying air temperature and 35.9% initial moisture content. The lower drying air temperature of 60°C yielded low percentage of stress crack kernels as well as higher percentage germination. The drying efficiency was recorded at 40.9% using drying air temperature of 60°C for drying shelled corn with 23.9% initial moisture content. The value is well below the limit set by the Philippine Agricultural Engineering Standard (PAES 201:2001) which is 75% minimum for Batch and Continuous flow dryer. Scaling up the dryer in terms of bigger diameter and longer length can improve heat utilization for moisture evaporation and drying efficiency. Generally, the use of lower drying air temperature of 60°C and below is safe for both quality and technical considerations. The use of higher drying air temperature is not recommended under the given condition of the study.