Composition and morphology of ash produced in a Waste-to-Energy (WtE) plant

In the present work, the chemical and mineralogical compositions of ashes collected from a Waste-to-Energy (WtE) plant are characterized and evaluated. The ash samples are collected vertically from bottom to top of the right side wall of the primary combustion chamber. The collected ash samples include ash slag formed in the vicinity of the grate and ash deposits formed on the boiler wall. Ash samples are analysed via an X-ray fluorescence (XRF) spectrometer and a scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDX), in order to obtain both bulk and micro chemical compositions. In addition, mineralogical phases in the ash samples are characterized via X-Ray powder diffraction (XRD). It is observed that the slag sample has completely melted into a dense clinker that has a clear layer structure along the thickness. XRF and SEM-EDX analyses on each layer reveal clear differences in chemical compositions and associations of the detected chemical elements. XRD analyses of ash deposits collected from different locations showed that they contain mixtures of salts, silicates and oxides formed during combustion of the MSW. However, concentrations of certain elements are different for ash deposits sampled from different locations, indicating partitioning differences during the transportation from bottom to top of the primary combustion chamber. Accordingly, proper treatment and disposing methods should be considered for the ash deposits collected from different locations in the incineration plant.