The Influence of Hevry Metals Distribution in Thermal Process of MSWI Fly Ashes by Washing Pretreatment

• Main Authors: Yi-Ming, Chen, 陳一銘
• Other Authors: Sue-Huai, Gau
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/76313074077987553379

碩士 === 淡江大學 === 水資源及環境工程學系 === 91 === The incineration process of municipal solid waste will accompanies a large number of fly ashes, and the TCLP (Toxicity Characteristic Leaching Procedure) shows it is hazardous waste, which can’t be treated by landfill or reuse directly. Solidification is used to apply in the fly ashes handling, but the product is still unstable. Thermal treatment methods are the most popular alternatives in many countries; however, the most metallic chlorides are easily to evaporate through the flue gas. In this study, flue gas is collected, and discuss by the mass balance analysis to discover the behavior of heavy metals during the thermal treatment process of MSWI fly ash. The washing of the fly ash was also executed before the thermal treatment as a comparison, in order to lower down the harmful calcium ion and chloride. The fly ash samples were collected from the cyclone and bag-house blow downs separately in a MSWI, the different temperature and retention time were designed in the experiments to simulate the melting condition. A tube furnace was adopted, the behavior of Pb, Zn, Cu and Cd were analyzed. The results show that the cyclone ash is easy to melt without pre-washing, but the reacted ash is difficult to reach its melting point. For this reason washing pretreatment was used to extract Ca and Cl in order to decrease the melting point. The results showed that, when the cyclone ashes and pre-washed reaction ashes reached their melting point, Pb is the most easily to evaporate, the evaporation ratio reached 99 %, and the reaction rate is also the fast one. The evaporation ratio of Cd, Cu and Zn are 90 %, 80 % and 57%, respectively. The most portion of the heavy metals are evaporated accompany with the flue gas during the thermal treatment operation, it is not stabilized in the slag; it should be pays much attention during the thermal treatment process.