Evaluation of cracks in paddy dried by solar drum dryer

The drying process is one of the most important and effective steps in the post-harvest processing of paddy, which is effective in improving the quality of its conversion to white rice and decrement the percentage of cracks created in the grain. In the present study, aimed to reduce energy consumption in the process of paddy drying and also to eliminate the adverse effects of fixed bed dryers in rice mills, a solar rotary dryer was designed and built. The main rotating tank of the device was made of a mesh plate and covered by a fixed cylinder made of galvanized sheets. The mesh plate distributes and passes air evenly in different directions and reduces the moisture content of the paddy. An electric motor of 0.75 hp was used to ensure the rotational motion of the main tank of the device. In this regard, the effect of a rotary solar dryer on reducing moisture content and the number of cracks created in paddy of Hashemi cultivar, and also the effect of airspeed on reducing its humidity were investigated. The paddies were dried at a temperature range of 43 to 46 ° C with a rotary dryer. The crack development response in the product was investigated with initial humidity of 11, 14, and 16% water-based. The stress crack index (SCI) was used to quantify the stress cracks created in paddy grains. The results obtained from the number of cracks index in rice grains showed that the solar rotary dryer has acceptable performance and the solar collector can provide the desired temperature conditions for drying rice paddy (43 to 46 degrees Celsius). Studies on the amount of stress crack index of paddy and its comparison with the stress crack index of paddy dried with batch dryer showed that drying paddy by rotary method significantly decreases the crack in brown rice.