A thesis submitted in partial fulfilment of the requirement for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1982

A directly heated screw conveyor dryer with a rice-husk fired furnace was constructed. The performance characteristics of both the dryer and the furnace were studied. The rice husk feed rate did not show any direct relationship with the increase in hot air temperature. The difference of flue gas and heating surface temperatures varied from 10 to 27°C. The breakage of paddy due to its movement in the screw conveyor for 6 to 7 passes was quite low, The grain residence time was a function of screw conveyor radiation speed and varied from 85 to 260 seconds depending on the rpm and grain moisture content. The conduction drying of paddy was represented adequately by a simple logarithmic model and its modified form in terms of grain moisture ratio as a function of drying time. The parameters of the drying equation could be related with the initial grain moisture content, heating surface temperature and the screw speed along with their interactions. The effect of auger speed was significant on the drying rate constant in both models. The higher the screw speed the faster was the drying for any given surface temperature. The effect of grain initial moisture content on the drying constant was not significant independently for both models, but its interaction with rpm and grain moisture content had strong influence on the drying rate. The milling test resulted in poor milling recovery and head yield for the experimental samples in comparison with the control, In view of the poor grain quality initially, the milling trials need further investigation at various stages of drying.