The purpose of this study is to experimentally investigate the desulfurization and dechlorination characteristics of seashell and limestone in two waste-coal co-firing circulating fluidized beds of 50 kg⁄h with different heights (15 m and 6 m). The tested wastes were Japanese RDF and Chinese waste, whilst the employed coals had varied fuel ratios of either 4.5 or 8.8. It was shown that the efficiencies of desulfurization and dechlorination were both higher for seashell than for limestone. At four times and beyond of the stoichiometric ratio of Ca over sulfur and chlorine, i.e. at Ca⁄(S+2Cl) › 4.0, the efficiencies of seashell for desulfurization and dechlorination reached more than 99 % and 80 %, respectively. Under the quoted conditions these efficiencies were only 95 % and 70 % for limestone. Meanwhile, it was found that the calcined seashell had a mean pore size four times bigger than that of calcined limestone, and this was considered to be the cause for the preceding different efficiencies. That is, when the bigger pores existing in calcined seashell allowed the desulfurization and dechlorination reactions to take place throughout the sorbent particles, those reactions were possible only on particles′ surface for limestone. Furthermore, the work clarified that the dusulfurization and dechlorination efficiencies for the tested different wastes, coals and circulating fluidized beds could be unified according to Ca⁄(S+2Cl) ratio.
The compo-casting technology of ceramics and cast iron is expected to be one of the major casting technologies that can expand the application fields of cast iron. This technique allows the heat energy of the molten metal to be utilized to produce cast iron products which are added with functions of ceramic materials. The largest problem in compo-casting technology is generation of cracks caused by thermal shock. Although this crack generation can be prevented by reducing the thermal stress by means of preheating ceramics, the necessary preheating temperature is considerably high and its precise controlling is difficult at the practical foundry working sites. In this study, we tried to numerically predict the critical preheating temperature of ceramics using the thermal stress analysis in unsteady heat transfer and the Newman's diagram, and found that the preheating of ceramics to reduce thermal stress could be substituted with placing an appropriate cast iron cover around the ceramics. Excellent results were obtained by using a method whereby a ceramic bar was covered with a flake graphite cast iron cover and fixed in a sand mold and then molten metal was poured. Then, two or three ceramics were examined at the same time under the compocasting condition. As a result, three specimens could be done at the same time by adjusting the cover space to 15mm. Moreover, irregular shape ceramics were examined under the compocasting condition. As a result, the compocasting could be done by devising the cover shape. In each condition, it was confirmed that the cover shape made from the analytical result was effective to the compocasting by doing the thermometry of the specimens.