AGGLOMERATION CHARACTERISTICS OF SILICA SAND-RICE HUSK ASH MIXTURES AT ELEVATED-TEMPERATURES

Rice husk, a major by-product of the rice milling process, can be a si gnificant energy resource in rice producing countries because of its h igh energy content. Fluidized bed gasifiers have been proposed for the recovery of energy from rice husk. The major advantage of fluidized b ed gasifiers over fixed bed gasifiers ir the high mass and heat transf er capability due to very high percentage of inert bed material such a s silica sand. In addition, the vigorous mixing and agitation of solid particles in fluidized beets promote a uniform temperature distributi on and a high conversion efficiency. However, attempts to utilize rice husk as a feed in fluidized bed gasifiers have been unsuccessful beca use of the high ash content of rice husk that may result in the agglom eration of inert bed materials at high temperatures. it this work, the effect of rice husk ash content (0.0, 5.0, 10.0, 15.0, 200, and 25.0% ) on the agglomeration characteristics of silica sand was investigated at various temperatures (750, 850, 900, 950, and 1000 degrees C) usin g a muffle furnace A light microscope, an environmental scanning elect ron microscope, and an energy dispersive X-ray analyzer were used to c haracterize the structural changes and elemental makeup of the samples . There was no indication of agglomeration below 850 degrees C, but at temperatures of 850-1000 degrees C the silica sand loosely agglomerat ed in the presence of rice husk ash at all levels of ash content. The effect was more pronounced at 1000 degrees C. The chemical interaction of the SiO2 and the low melting temperature mineral oxides (k(2)O, Na 2O, and P2O5), present in notably low concentrations in rice husk ash, appeared to be the mechanism resulting in the formation of the loose agglomerates.