A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Environment, Resources and Development

Thesis (Ph.D.) - Asian Institute of Technology, 1988

Accelerated drying of paddy was investigated in specifically designed and constructed experimental rotary conduction heating units. Paddy having moisture content in the range of 18 to 24% was dried using heating surface temperatures of 100 to 150 0c and exposure times up to 100 min in a continuous recirculating batch operation. A two-stage paddy drying operation with tempering of warm grain for two hours after each stage was found satisfactory for general use. A generalized drying model was developed for estimating the moisture removal from paddy during conduction heating in any given equipment in terms of mean bulk grain temperature determined from the time temperature history. The milling qualities of paddy such as head rice yield and milled rice whiteness could be maintained close to those of shade-dried control until the bulk grain temperature reached 60 0c. In general, conduction heating of paddy for accelerated drying led to a better grain quality in comparison with conventional drying practices. Also there was no evidence of gelatinization of starch in rice kernels due to conduction heating.