VinylMet - Recovery of heavy metals from MSWI slag

To date, PVC waste that cannot be recycled in the EU has mostly been thermally utilised (or destroyed) in conventional waste incineration plants without flue gas cleaning or in FLUWA without chlorine recovery. The incineration of non-recyclable PVC waste in a Swiss MSWI plant with flue gas cleaning is a chemical recycling process, as the chlorine it contains is recovered as hydrochloric acid. In an earlier project (VinyAcid), it was found that the dosed addition of PVC sorting residues in MSWI plants not only produces more acid, but surprisingly also shifts heavy metals from the slag into the filter ash. This second effect has a double ecological benefit. Firstly, the quality of the slag is improved and secondly, additional recovery of heavy metals from the filter ash is made possible. The project aims to improve our understanding of the thermodynamics and kinetics of the thermal mobilisation of heavy metals in the form of their chlorides. To this end, the existing literature is compiled and gaps in knowledge are closed through experimental and laboratory investigations. In final tests in a waste incineration plant, PVC waste is deliberately added to one furnace line, while the second line is fed normally without ‘additional’ PVC addition. The transfer of heavy metal chlorides from the slag to the filter ash is quantified by chemically analysing the incineration residues (mainly filter ash and slag).