Recovery and reuse of fly ash from municipal solid waste

摘要

In order to take advantage of the energy available from non-traditional sources of biomass and wastes, thermal recovery systems must deal with the by-products resulting from the operation. Typically, two major by-products are produced; bottom ash and fly ash, the material collected from scrubbers, baghouse filters and electrostatic filters. It is this latter material that causes environmental concern because of the enrichment of metals such as zinc, lead cadmium and copper caused by the concentrating mechanism of vaporization during the thermal processing of the biomass and subsequent condensation on the solid phase ash particles entrained in the gas stream. For most fly ash by-products, the enrichment is not large enough to be of commercial interest for metal recovery, however the concentration is sufficient for environmental concern and to prevent usage of the fly ash as a silica additive for cement manufacture or for construction applications. The chemical and thermal characterization of municipal solid waste fly ash was carried out and the results used to interpret the speciation and formation mechanisms of the metal contaminants. The results show that the removal and separation of the contaminant species is possible using thermal treatment technology.