Factors Determining the Element Behavior in Municipal Solid Waste Incinerators. 2. Laboratory Experiments

Laboratory experiments with synthetic samples are conducted to obtain information on the evaporation behavior of metals in incinerators. In combining the results obtained through field measurements presented in a companion paper in this issue, hypotheses are postulated on the influence of physical and chemical conditions as well as of kinetics on the evaporation behavior of the chosen elements in the furnace bed. These are validated by thermal treatment of bottom ash samples in the laboratory. A temperature increase of from 500 °C to 900 °C causes higher transfers of most metals into the gaseous phase. Mo and Sb are the exceptions. Chlorine availability generally favors evaporation. Increasing oxidative conditions cause lower Sn transfers. Transfer of the elements Cd, Mo, Sb, Sn, and Zn is negatively affected by their reaction with reaction partners other than oxygen and chlorine occurring in municipal solid waste. Oxidation of organic carbon to CO and CO2 as well as HCl formation determine the distribution of temperature, redox conditions, and chlorine availability in the furnace bed. First indications are obtained on the residence times of goods under these different local conditions. The knowledge acquired can be used to design new incinerators with "tailor-made" products that can either be recycled or landfilled without an adverse environmental impact for the long term. For this purpose, mechanical processing techniques, thermal treatments at temperatures between 500 °C and 1100 °C, and high-temperature treatments (>1100 °C) including melting processes will have to be combined.