Junya Nishino*, Jujiro Umeda**, Toshiyuki Suzuki**, Ken-ichi Tahara*, Yoshiaki Matsuzawa*, Shun-ichiro Ueno* and Naohito Yoshinari**

* Environmental Process Development Department, Industrial Machine & Plant Development Center, Ishikawajima-Harima Heavy Industries Co. Ltd.
** No.2 Equipment Engineering Department, Engineering Center, Environment & Plant, Ishikawajima-Harima Heavy Industries Co. Ltd.

+ Correspondence should be addressed to Junnya Nishino:
(1 Shin-nakahara- machi Isogo-ku Yokohama 235-8501 Japan)

Abstract

Melting tests of four kinds of ash, are conducted with a DC type electric resistance heated melting system, being renovated to an actual plant size. The obtained results are examined in terms of changes of material balance and heat balance, from scaling up activity, and in terms of the environmental safety of the system products. Complete decomposition of waste materials to harmless states through an incineration process is difficult to achieve. However, an addition of a melting process to the incineration process is found to considerably decrease the heavy metal releasing tendency of the slag being formed from incineration ash, and amounts of dioxins released out of the system. Thus, the system demonstrates its capability of harmlessly decomposing waste materials, almost completely. The demonstration tests show prospective practical applications of the system. Waste gas treatments are indispensable, because large amounts of hazardous materials are contained in incineration ash and fly ash. Potential problems in measures for waste gas treatments for a slag melting furnace, become clearer by conducting experiments with larger equipment. The inherently low volume of flue gas from the developed system, provides flexibility in choosing either a dry process or a wet process for the system, according to possible construction sites. Both of the gas treatment processes demonstrate their compatibility to environmental safety regulations. The power consumption of the melting treatment of the system is 680kWh/t-ash for melting fly ash. Furthermore, a design practice is developed, whereby a small scale waste gas treatment equipment is realized.

Key words: municipal waste incineration, melting treatment of ash, exhaust gas treatment, DC electric joule-heating method, scaling up of plant