【Paper】
Thermodynamic Study of the Behavior of Elements with Low Boiling Points in the Melting Process
Shohichi Osada*, Morihiro Osada*, Masayuki Kokado** and Masanori Tokuda***
* Environment and Waterworks Solutions Division, Nippon Steel Corporation
** Bureau of Environment, Tokyo Metropolitan Government
*** National Institution for Academic Degrees and University Evaluation
† Correspondence should be addressed to Shohichi Osada:
Environment & Waterworks Solutions Division, Nippon Steel Corporation
（6-3 Otemachi 2-Chome, Chiyoda-ku, Tokyo, 100-8071 Japan）

Abstract
To clarify the behavior of low-boiling-point heavy metals in the melting process of wastes, the suitability of simulations using thermodynamic models was investigated by comparing the results of simulations with those of actual operations undertaken in an incineration-residue melting furnace in a test plant.
Results of the simulations indicate that melting conditions such as melting temperature and oxygen partial pressure greatly affect the behavior of low-boiling-point heavy metals in the melting process. In particular, we obtained data on the behavior of Pb because its presence can cause environmental problems when molten slag is utilized.
As melting temperature increased and oxygen partial pressure decreased, the volatilization of Pb increased and the content of Pb in the molten slag became lower. In addition, the actual operations of a test plant confirmed that most Pb volatilizes into gas and the Pb content of molten slag is kept as low as 60-70mg/kg. These results confirm the accuracy of the simulation test.

Key words: thermodynamics, melting furnace, waste, heavy metals, molten slag