||The objective of this study was to utilize an electric arc furnace （EAF）in a steel mill to melt municipal incinerator fly ash （MIFA）of different sources （Plants K1 and K2） and evaluate its effectiveness in aspects of environment and economy. The results of full-scale tests have shown that slag thus generated by the EAF was found to be non-hazardous based on the TCLP result and also met the standard of CNS 14602. However, EAF dust thus obtained remained hazardous as it was originally a listed waste by Taiwan EPA. Test results have indicated that this novel treatment technology would not deteriorate the quality of steel billets and bars produced. Moreover, when melting MIFAs from Plant K1（with 2.00 wt％ of MIFA） and Plant K2 （with 3.28 wt％ of MIFA）, the air quality in the steel mill surroundings and off-gas from the stack were all below the regulatory limits. Thus, it would not cause additional pollution problems from this practice. Based on the total capacity of EAFs in Taiwan, it was estimated that these EAFs would be capable of melting fly ash generated by municipal incinerators in Taiwan. |
From the economic perspective, this melting practice would not lower the production rate of EAF steel-making and increase the tap-to-tap cycle time, consumption of electrical energy, consumption of oxygen, and consumption of graphite electrodes. Furthermore, through this novel practice, the contents of MIFA have turned out to be able to replace some portions of quick-lime and coke powder required for steel-making. Test results have also shown that 1 wt％ of MIFA injection would generate additional 8.93 kg of slag and 2.76 kg of EAF dust.
It was found that an additional cost of NT＄318 per ton of MIFA treated would be resulted through this practice. This treatment cost is very low as compared with NT＄8,000 per ton of waste treated by solidification and followed by landfilling. Assuming a melting cost of NT＄5,000 per ton of MIFA is charged by EAFs, it would save more than ten million NT＄ per year for a municipal incinerator with an annual generation of 5,840 tons of MIFA. On the other hand, for a mini-mill with an annual capacity of 264,000 tons of billets, it would have an additional income of 37 million NT＄ if 3 wt％ of MIFA is melted while making steel.