Ash deposits characterization in a large-scale municipal waste-to-energy incineration plant

Chemical and mineralogical compositions of deposits from a municipal solid waste incineration plant in Oslo, Norway, have been characterized. Ash deposits are analysed via a combination of scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray powder diffraction (XRD) and X-ray fluorescence (XRF). The results show that the deposits formed have a clear layered structure along the thickness, in terms of density and morphology. The combination of different analytical techniques is also capable of characterizing chemical and mineralogical compositions of the collected deposits along the thickness of the deposits. The key ash transformation and chemical reactions involved in deposits formation in this plant are investigated and summarized. The primary deposits, mainly melted sulphates and chlorides, initially build on heat transfer tube surfaces and act as a sticking surface to particles and aerosols passing by. The secondary deposits are dominated by calcium sulphates, silicates, and calcium and silicon oxides formed in the combustion chamber. Within the deposits, interactions of different mineralogical phases take place, leading to formation of new chemicals and further sintering of deposits.