GRAIN DRYING POTENTIAL WITH NATURAL AIR IN BOTUCATU (SP)

Abstract

Computer simulation was used to determine ambient air grain drying potential in Botucatu (São Paulo State) based on equilibrium moisture content for safe storage for one year. Hourly weather records, dry bulb temperature and relative humidity, from March to June, 1971, were used as input data for the simulation program. The same 1°C temperature rise due to drawing the air over the fan motor was assumed. Results showed that ambient air grain drying systems operating continuously aren’t feasible to reduce the moisture content of soybeans, corn, sorghum and edible beans to the moisture levels recommended for safe storage. Simulation procedure using continuous fan operation also indicated the feasibility to dry rough rice in spite of restriction within some periods along of four analysed months. Selective ambient air drying, based on restricting fan operation to daily hours when the drying potential of the air is highest, indicated a decreasing ambient air drying feasibility in the following sequence: rough rice, with daily fan operation above 13 hours in less restrictive periods, and corn, with selective drying process accomplishing below 11 hours, being unfeasible to achieve in more restrictive periods. In this procedure it wasn't possible to reduce equilibrium moisture content of the grain sorghum and edible beans to levels for safe storage. Average relative humidity higher than 71%, 68% and 61% didn’t allow to achieve equilibrium moisture content levels for safe storage for rough rice, soybeans and corn, respectively.

KEY-WORDS: Drying; ambient air; rough rice; edible beans; corn; soybeans; grain sorghum; equilibrium moisture content.