Material and chemical composition of municipal solid waste incineration bottom ash fractions with different densities

Abstract

Bottom ash is the main solid residue from municipal solid waste incineration (MSWI). The material can be utilised in the construction industry but high requirements for this option are often not met by material generated during ordinary bottom ash treatment. Hence, the objective of the present study is to investigate the suitability of density separation for bottom ash to generate mineral material fractions with different properties. MSWI bottom ash samples were sieved to a size of 2–4 mm and 4–8 mm, respectively, washed and dried before being fed to a density separation processes. Thereby, the density fractions 3000 kg/m3 were generated and, subsequently, sorted into mineral material, glass, metals and unburnt organic matter. Mineral material with a density above 2400 kg/m3 and even more above 3000 kg/m3 shows a very high content of Fe, Cu and Zn of up to 448,000 mg/kg, 61,000 mg/kg and 44,000 mg/kg, respectively. Hence, the high density fraction of mineral material could be used as a raw material for metal production. Glass with a density above 2400 kg/m3 has a Pb content of up to 87,000 mg/kg, while the Pb content of lower density glass is decreased.