Environmental safe and economic deposition of municipal and industrial waste has become one of the main anthropogenic environmental issues worldwide, over the past couple of decades. Incineration has developed into an increasingly popular method to reduce the volume of both municipal and industrial wastes. In addition to reducing the quantity of the waste disposed off in landfills, the benefits of incineration may include stabilization of certain hazardous compounds within the fused ash and energy production from the combustible parts of the waste. Incineration may also create alternative recycling options, such as a filler or active component in construction of materials. A comprehensive chemical characterization of the incinerator ash is important for understanding the need for further treatment of the ash before it is taken to landfill. Furthermore, a comprehensive characterization is essential for evaluating the recycling or reuse potential of the ash, and for addressing potential operational problems related to ash deposition and corrosion. Based on our knowledge on characterization of coal- and biomass-derived ashes, we have realized that bulk-chemical oxide characterization of an ash is not sufficient for understanding the complexity of the material with respect to controlling the impact of ash on boiler performance. Due to an even wider range of elements and chemical species present in municipal solid waste, compared to biomass and coal, the ash formed during waste incineration is likely to be even more complex. As part of a current project on mapping of the ash chemistry in Danish Municipal Solid Waste Incineration (MSWI) plants, different ash fractions, i.e. bottom ash/slag, 2nd-3rd pass ash, and ash from the ESP was collected at four Danish MSWI plants. The ashes have been characterized by use of standard wet chemical analyses as well as by a number of advanced analytical techniques, including, Scanning Electron Microscopy (SEM-EDX), Computer Controlled Scanning Electron Microscopy (CCSEM), Quantitative X-Ray Diffraction (QXRD), and Simultaneous Thermal Analysis (STA), in order to deduce their chemistry and thereby be able to map the boiler ash chemistry in these plants. In addition to an outline of Danish waste management strategies, this paper contains an introduction to each of these analytical techniques, and a comparison of the results obtained as a function of analytical technique and waste incinerator plant.
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