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Flender/Flender Gear Units/Bevel-helical speed reduction gearboxes B3

Particles Removal of moisture as well as pufng of cereal grains is traditionally practiced in south- east Asian countries using heated particles in direct contact with the grain. However, nolarge-scale commercial unit has yet been available for drying grains by this technique. heated-sanddrying system has been reported to be very effective for drying paddy (2% moisture content). One part of paddy is mixed with two parts of sand(1C) in rotating drum for 5 min (. The discharged mixture of sand and grain is separated by screen, and the sand is recycled to the drum. While the grains are parboiled in situ, there is simultaneous removal of moisture from the grains. Moisture removal is very rapid if the sand temperature is increased to 1 2C and mixed with paddy for 1 . signicant increase in yield of head rice is noted compared withthat of shed-dried sample. Removal of grain moisture from 2% to 1% (db) is possiblewith either small sand/grain ratio with moderately high sand temperature, or with largesand/grain ratio with low initial sand temperature (. From an energy point of view, larger sand/grain mass ratio with higher initial sand temperature is favored. 4 CONVECTION DRYING The most popular grain-drying technique is convection drying. In this system, the heat transfer for drying is accomplished by direct contact between the wet material and stream of hot gas (generally air). The vaporized moisture is carried away from the grain by the heating medium. Both continuous and batchwise convection-drying systems are practicedfor drying wet grains. Convection drying can be further subdivided, as given in Fig. 1. 4.1 Natural Air Drying Natural air drying is essentially in situ drying of grain that is contained in bins commonly used for grain storage. The bin is equipped with fan or blower, duct system, perforated Fig. 1 Classication of convection grain-drying system. 1 Das and Chakraverty oor, and exhaust vents for the moist air to escape. The primary need in thi