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Project Leader and Principal UC
Investigators
R.P. Singh
S.M. Henderson
G.E. Miller
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Objective
To increase the energy efficiency of rice dryers; to determine the
optimum time in terms of moisture content of rice when it is most economical
to transfer rice from a column dryer to a deep-bed dryer; to develop
computer-aided simulations of rice drying for evaluating the dryer
performance in terms of energy efficiency, rice quality, and increased
capacity.
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"Tempering times currently used in commercial rough rice drying may be
much longer than necessary." |
Since the project was not funded at the requested level, the objectives
presented in the proposal were only partially accomplished. Research
emphasis was placed on examining moisture movement inside rice grain to
provide information on drying rates of California-grown rice and on the
tempering process. Moisture diffusivity in the rice hull, bran layer and
starch endosperm was determined. It was found that the rice hull provides
the maximum resistance to moisture movement. Temperature and drying time (or
degree of moisture removal during drying) have the greatest effect on
tempering time. Initial grain moisture content and relative humidity of the
drying air have a minimal effect in comparison to the above variables. In
the multi-pass drying of rough rice, the degree of tempering between passes
will affect the final moisture content of the grain. Tempering times
currently used in commercial rough rice drying may be much longer than
necessary. In simulation studies, for temperatures ranging from 35° to 55°C
and other typical drying conditions, tempering was 95 percent complete in
less than two hours and fully complete in less than five hours.A new drying system, spouted-bed drying, was examined for drying rough
rice. This research was made possible by a private manufacturer who has
loaned the unit for experimental trials. The preliminary results indicate a
major improvement in reducing the drying time when compared to conventional
cross-flow dryers. In addition, this drying system results in uniform grain
drying time, thus, significantly reducing milling quality loss during the
drying operations.
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