"A STUDY ON GRAIN DRYING"EFFECT OF DIFFERENT AIR DISTRIBUTION METHODS ON RICE DRYING IN GRAIN BINS

Abstract

Rice, one of the world's leading food crops, is usu all y harvested at moisture contents above safe storage levels and requires additional d rying. In Egy pt the total planted area of rice approached about 1.508 million feddan producing 6.18 Tg. (R.R.T.C., 2004). Various systems of drying are employed and the effici ency of these systems is becomi ng increasingly important wi th the ever tightening supply of fossi l fuel s (Verma eta/, 1985). As air passes through a column of grain, drying does not occu r uniformly throughout the depth. In general, the grain can be considered to be in one of three zones: d ry, drying, and wet. As the air enters the grain, drying begins nearest the air inlet, and as the drying proceeds, a drying zone is established that moves through the grai n. The depth of the drying zone w ill depend upon the condition of the entering air, the initial grain moist ure content, and the a ir-flow rate (Shove and Olver, 1967). In-storage d rying wi th su pplemental heat involves d ry ing of a relativel y

l arge batch of gra in. It i s carried out in bins of vary ing capacity up to I 00 tons. Venti lation is accomplished by blowing slightly heated a ir, 4• to 12·c above ambie nt temperature through a duct system or through one centrall y pl aced cy linder, as is the case for batch drying. In-storage d ry ing may a l so be carri ed out on a bar floor prov ided with a sowerful fan and a sat isfactory system of floor and lateral ducts with air flow rates ra nge from 80 to 165 m3/h per ton of grain

(M ujumdar, 1995) .

One function of a n air-distribution system during in-storage d ry ing or aeration operation is to d istribute air as uniformly as possible. Uniform air flow is important in producing uniform d ry ing. (Lampman and Hukill, 1968).