【Paper】
Re-synthesis Mechanisms for PCBs and Chlorobenzenes in Fly Ash by Particle Size
Masaki Takaoka*, Nobuhiro Tanigaki*†, Nobuo Takeda* and Takeshi Fujiwara*
* Department of Urban & Environmental Engineering, Graduate School of Engineering, Kyoto University
*† Environment Plant Project Section, Steel Plant & Environmental Engineering Div., Nippon Steel Corporation
† Correspondence Should be addressed to Masaki Takaoka:
（Yoshida-Honmachi, Sakyo-ku, Kyoto, 606-8501 Japan）

Abstract
We focused on separating fly ash by particle size in order obtain fractions with different compositions. We then conducted heating experiments on each fraction under a variety of temperature and atmospheric conditions in order to understand the re-synthesis mechanisms of chlorinated aromatics in fly ash and the distributions of PCBs and chlorobenzenes（CBzs）by fly ash particle size. As a result, we found that the contributions of metal catalysts and unburned carbon in the formation of PCBs and CBzs were dependent on heating temperature. The homologue patterns of PCBs and CBzs were almost the same in all fractions of fly ash in the heating experiments. This indicates that all fractions of fly ash had the same formation patterns. The effect of atmosphere on the formation of chlorinated aromatics showed no difference among the fractions. HCl in a nitrogen atmosphere with 10％ oxygen did not promote generation of PCBs and CBzs in fly ash. We confirmed that metal chlorides in fly ash were important as a chlorine source rather than HCl gas for the formation of chlorinated aromatics in fly ash.

Key words: fly ash, particle size, PCBs, unburned carbon, formation mechanism