2014 Volume 93 Issue 11 Pages 1220-1226
To clarify the chlorine behavior of waste plastics injected into CaCO3 calcination furnace, destination of Cl was estimated by thermodynamic calculation. Calculation result showed that chlorine in waste plastics was discharged to the exhaust gas as HCl at 900 ℃ and Cl content in CaO was negligible thermodynamically. Next, chlorination/dechlorination test of CaO using an electric furnace and Cl containing waste plastics injection test into commercial CaCO3 calcination furnace have been carried out. In chlorination/dechlorination test in electric furnace, chlorination/dechlorination rate of CaO at 600 ℃ was faster than those at 900 ℃. From results of SEM measurement, CaCl2 formed on the surface of CaO was detected. It is considered that CaCl2 melted at 900 ℃ inhibited chlorinated / dechlorination reaction. In waste plastics injection test at commercial CaCO3 calcination process, Cl content in CaO was affected by waste plastics speed into furnace. In case of high speed injection of waste plastics, the residence time of CaCl2 in furnace was longer than that of low speed injection. Result of the analysis of off-gas and dust from furnace, showed that HCl was not in off-gas but high concentration of Cl was included in that fine dust. It was considered to have sufficient time to declorination reaction of CaCl2. Therefore, it is considered that most of Cl in waste plastics was discharged as a fine dust in the commercial process.
