B3-CV-14B th reinforced bearing up to size see page Fl Bevel-helical speed reduction gearbox B3

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

perature of 5 the raw rice straw and husk are not converted to milky white ash even after their long exposure. It is necessary to pretreat them with mineral acids at the elevated temperature for 1 to remove their metallic impurities forthe production of pure white ash by complete combustion. The acid treated straw and husk samples of 2-cm bed thickness subjected to 4 to 5C furnace temperatures correspond to the complete combustion times of about 3 and 1.5 , for the production of milky white ash. The diffractograms of both untreated and acid-treated straw and husk at 5 for bed depth of 2 cm show no sharp peak, thus indicating that the silica in the white ashsamples is amorphous in nature. As the bed temperature may exceed the critical tempera-ture of 7 for crystallinity of amorphous silica at higher bed depth and higher furnace temperature, furnace temperature of 4 and bed depth of 2 cm are suitable for the production of pure amorphous silica from acid treated straw and husk (. 6.2 Pure Silicon from Rice Husk and Straw The amorphous silica available from rice husk and straw nds varied uses, depending on its form and purity. It is used as an antisticking agent, as reinforcing material in rubber, as ller in paper, and as base material in silicate industries. Because amorphous silica is active, it can be reduced to silicon at comparatively lower temperature by metallothermicreduction and other processes. Solar grade and semiconductor grade silicon have to bevery pure. Conversion and Utilization of Biomass 8 The processes developed for conversion of rice husk silica to silicon is described in the subsequent paragraphs. 6.2.1 Calcium Reduction Process The pure rice husk silica can be reduced to silicon of reasonable purity by using calcium as strong reducing agent. The white ash obtained by burning rice husk at about 5 is leached with moderately hot concentrated mineral acids to remove most of the solubleimpurities present in it. The material is then tho