In view of the limited natural resources and the protection of the global environment, a process for treating the waste materials discharged from industrial production and human life is strongly requested to be developed. A multi smelter was proposed, which consists of coke packed bed in the lower part and free board where fine materials are fluidized during operation in the upper part. It can reduce significantly the volume, eliminate toxicity and recover some materials such as metals, because it has high temperature that can melt waste and reducing atmosphere. Many melting tests were done successfully from February 1999 using the multi-smelter constructed at Osaka Prefecture University. This reactor can treat the waste materials of 1 ton/day. In this operation test, industrial waste materials like used TV sets, air conditioners and refrigerators was melted without secondary emission of dangerous materials like dioxin. In this multi-smelter, the packed bed part seems to play an important role for melting metallic wastes effectively and for achieving a stable operation. On the basis of this foresight, a two-dimensional mathematical model has been proposed, which considered transport phenomena of heat, mass and momentum together with melting and chemical reactions in the high temperature packed bed for processing waste materials. Numerical simulation was conducted to investigate in-furnace phenomena and effects of operating conditions on the process stability. As the results, the process characteristics such as distributions of gas concentration, temperature and velocity have been obtained; they are useful to evaluate the performance of the multi-smelter and to improve the operations leading to less energy consumption and more waste materials treatment. The results showed the multi-smelter is a useful process for melting some kind of waste materials like used refrigerators, air-conditioners, the major part of which were originally made from iron and plastics.