Performance evaluation of the IRRI Rotary Dryer in Partial drying of paddy under field condition

Date

1987

Abstract

The performance of a continuous-flow rotary dryer was evaluated in partial drying of freshly harvested IR-60 paddy from high moisture levels down to 18.0% wet basis (or 22% dry basis) in one pass. Intended for farm-level use, the dryer was made simple in design by IRRI through features like manual rotation of the drum, use of crop residues as fuel, and construction of the furnace shroud from soil mixed with paddy straw. Preliminary test results showed that both grain flow rate and retention time of paddy in the rotary dryer were affected significantly by hopper opening and drum inclination. At a constant drum rotational speed of 7.0 rpm and full hopper opening of 44 mm, the logarithms of grain flow rate and retention time were found to decrease and increase, respectively, as drum inclination increases. During partial drying of wet paddy samples, furnace temperatures ranged from 400 to 800°C, drum surface temperatures from 172 to 231°C, while paddy temperatures ranged from 60° to 80°C. The initial moisture values of 22.2, 26.1 and 28.1% wet basis (or 28.4, 35.2 and 39.0 % dry basis) of paddy samples were reduced to the safe moisture level of 18.0% w.b. (22% d.b.) in one pass at average drying times of 19.1, 28.3, and 29.7 minutes, respectively. The effective drying capacity of the rotary dryer was about 45.2 kg/hr or 0.45 tons/day, which may be adequate to relieve peak harvest demands thereby avoiding handling delay problems. Significant differences were obtained in both final moisture content and effective drying rate and initial moisture content, implying that the higher the initial moisture content, the higher the effective drying rates at low drum inclinations. Gelatinizations of the starch molecules of high moisture paddy partially dried might have resulted in higher total milling and head rice recoveries than those of the control samples but this needs to be verified carefully in the laboratory. Statistical analysis showed a highly significant effect of initial moisture content especially on head rice yield for both one and two passes through the rotary dryer. To avoid the destruction of rice seed viability, the rotary dryer should not be used. Drying costs may be reduced by using crop residues as fuel, although overall thermal efficiencies obtained for partialdrying seem low.

Document Type

Master Thesis

Language

English

LC Subject

Grain--Drying, Rice--Drying

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 995 1987 A2 I76

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