Comparison of rotary dryer with conventional fixed bed dryer for paddy drying, milling quality and energy consumption

Operation of a rotary dyer (RD) was compared with conventional fixed bed dryer (FBD). Drying time, trends of moisture content and specific energy consumption for water evaporation were investigated for drying of Iranian paddy cultivar., rice milling quality such as husking, milling recovery (MR) and head rice yield (HRY), were studied. Result showed that, using FBD decreased drying time and saved energy 8 and 6.78 percent, respectively. Specific energy consumption in NRD was 10.48 MJ per one kilogram of removed water and it was 6.82 percent more than FBD.  Paddy moisture contents and temperatures differences at top and bottom layers of FBD were 2 percent and 6°C, respectively. High thermal stress in low layers of FBD increased grains cracking chance in milling process. The type of dryer did not have significant effect on dehusking process, but MR and HRY were 2.7 and 7.6 percent respectively more when paddy dried with RD.