Experimental evaluation, simulation and optimization of a commercial heated-air batch hay drier .1. Drier functional performance, product quality, and economic analysis of drying

This paper considers the engineering design, operation, functional performance, product quality, and economic analysis of a natural gas heated-air batch hay drier that operates with an automatic bale wagon. The automatic bale wagon and a track are used for loading and off-loading stacks of alfalfa and timothy hay en masse to and from the drier. The newly developed batch hay drier has two identical drying units in a gable roof building, and each drying unit has a large axial flow fan which forces about 450 m(3)/min of air by negative pressure through 22-32 t (a maximum of five stacks) of small rectangular hay bales placed to dry on the perforated extended metal grate floor of the drier. Top plenum swing-away frames, with attached polyethylene curtains, were used for effectively sealing the vertical sides and one end of the hay stacks. Batches of hay, initially at about 25-40% moisture content wet basis (w.b.) were successfully dried to 12-15% final moisture content in 17-37 h at moderate drying air temperatures of 45 +/- 5 degrees C. The drying capacity was 1.0 t dried hay/h, specific fuel consumption 26 m(3)/t, specific energy consumption 4790 kJ/kg water evaporated, and drying energy cost Canadian $5.82/t when hay was dried from an initial moisture content of 30% w.b. to a final value of 15% w.b. The hay produced by the drier was of high quality with an attractive green color. (C) 1996 Silsoe Research Institute