Characteristics of element distributions in an MSW ash melting treatment system

Thermal treatment of municipal solid waste (MSW) has become a common practice in waste volume reduction and resource recovery. For the utilization of molten slag for construction materials and metal recovery, it is important to understand the behavior of heavy metals in the melting process. In this study, the correlation between the contents of elements in feed materials and MSW molten slag and their distributions in the ash melting process, including metal residues, are investigated. The hazardous metal contents in the molten slag were significantly related to the contents of metals in the feed materials. Therefore, the separation of products containing these metals in waste materials could be an effective means of producing environmentally safe molten slag with a low hazardous metals content. The distribution ratios of elements in the ash melting process were also determined. The elements Zn and Pb were found to have a distribution ratio of over 60% in fly ash from the melting furnace and the contents of these metals were also high; therefore, Zn and Pb could be potential target metals for recycling from fly ash from the melting furnace. Meanwhile, Cu, Ni, Mo, Sn, and Sb were found to have distribution ratios of over 60% in the metal residue. Therefore, metal residue could be a good resource for these metals, as the contents of Cu, Ni, Mo, Sn, and Sb in metal residue are higher than those in other output materials.     

Phosphate recovery from phosphorus-rich solution obtained from chicken manure incineration ash

The recovery of phosphorus from waste is very important for Japan because Japan has no natural phosphorus resources. In order to recover phosphorus from incineration ash of chicken manure, an acid dissolution–alkali precipitation method was investigated. Phosphorus content in the ash was 8%. The ash was treated with hydrochloric acid to obtain phosphorus-rich solution. Phosphorus could then be recovered as a precipitant by adding sodium hydroxide solution into the phosphorus-rich solution and gradually changing the pH in the solution to 3, 4, and 8. At pH 3, a small amount of phosphorus was precipitated to remove iron, which would cause coloring of subsequent precipitants. At pH 4, 84% of the phosphorus in the original solution could be recovered as CaHPO₄ · 2H₂O with a purity of 92%. At pH 8, 8% of the phosphorus in the phosphorus-rich solution could be recovered as identified hydroxyapatite. A recovery rate of 92% phosphorus as CaHPO₄ · 2H₂O and identified as hydroxyapatite was achieved.     

Leaching behavior and mineral speciation of cement-solidified boiler fly ash from industrial waste incineration containing waste tires

Journal of Material Cycles and Waste Management - This study characterizes the leaching behavior of fuel raw boiler fly ash (BFA) and cement-solidified/stabilized raw boiler fly ash (SBFA). X-ray...