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Show 7 . 3 For preventing heat damage of slag tap area and damages to the furnace wall, it is effective to provide water cooling by water tubes covered with refractory materials. This will enable a continuous six-month operation. However, it consumes heat, and a design to minimize cooling loss is essential. When fly ash is added to the load, the basicity of the ash goes up, raising the melt temperature. Also K 2 0 and Na2 0 contained in the fly ash lower the heat resistance of the refractory materials. These factors accelerate the furnace wall deterioration, making it difficult to maintain six-month continuous operation, 7.4 It is recommended to adopt a radiant-heat air heater, and also use of water-jet cooler which will provide instantaneous pass-through of heavy-metal deposition temperature rangp. This will prevent blockage and erosion of exhaust gas system and ensure safe operation. 7 . 5 Even with the most suitable burner and furnace design available at present, and a system designed to minimize exhaust gas heat loss, ash loading in real life can not always go continuously. Pre-heating time can lengthen, and it must be included in calculating the operational cost of a furnace. Acknowledgment I wish to thank the staff of Tokyo Gas Company whose assistance was very helpful in resolving furnace characteristics using gas burners. References 1) Development of Surface Melting Furnace. Takuma Technical Review Vol.3, No.l, pp.24-31 (1995). Kiyoshi Shibata and Masahide Nishigaki 2) Collection of papers for 14th presentation meeting of Energy Resources Association, pp.201-206 (1995). Yoshihisa Kawai, Dawei Liu, Kiyoshi Shibata etal. 3) Mixed Melting of Hy Ash and Incombustibles by Surface Melting Furnace. Collection of papers for the 5th presentation meeting of Waste Association, pp.339-342 (1994). Kiyoshi Shibata, Masahide Nishigaki, Dawei Liu and Haruo Nogami. 4) Melting Characteristics of Surface Melting Furnace (Part 1). Environmental Sanitation Technologies Research Vol.8, No.3 pp. 191-195 (1994) Masahide Nishigaki, Haruo Nomura, Dawei Liu & Kiyoshi Shibata. 5) Forum onBottom Ash and Hy Ash Disposal'94, pp.37-52, 1994, Masahide Nishigaki 15 |