Drying Performances and Economic Investigations of Forced Convectional Re-circulating Paddy Dryer

Kyaw Cho Cho Thin, Phyu Phyu Thant

The main objective of this study is to investigate forced convectional re-circulating paddy dryer with three main aspects such as technical operation, drying performances, and economic analysis. To cover the primary aim of research, various initial moisture contents 30%, 25%, 20% and 16% wet basis of paddy are dried until final or safe moisture content of 14% wet basis. Technical operations including drying temperature requirement, water removal rate, mass flow rate of drying air, electrical and thermal energy consumptions are evaluated. Drying temperature of paddy dryer is assumed according to ambient temperature and its range varies within 60-44℃. In electrical energy consumption, both main mechanical drying machines, and supporting machines such as conveyors and elevators are considered. Maximum and minimum electrical energy consumptions are 578.36 kWh and 101.78 kWh for 30% and 16% initial moisture content paddy drying respectively. Since holding capacity of paddy dryer is 30 tonnes in average, specific thermal energy consumption differs within 19.209 kWh/tonne and 3.393 kWh/tonne. In terms of thermal energy, paddy dryer works with rice husk heating system. Thus, husk consumption is estimated to require 163.878 kg/hour for maximum drying time, and 136.565 kg/hour for minimum drying. Drying performance results indicate that average drying time required is about 7 hours with consideration of tempering while average drying capacity is about 4.813 tonne dry paddy/hour. Maximum drying rate of paddy dryer is 0.027 kg water/hour and 0.007 kg water/hour is for minimum rate. The resultant drying efficiency is 62.874% in average that represents further evidence of good paddy drying performance. Economic analysis is studied with milling quality achievement, operation cost, and profit for one-kilogram rice. Exceptional amount of rice that is about 95.75% is recovered after milling, and so this provides leading to extensive profit achievement by using forced convectional re-circulating paddy dryer.