Quantification and distribution of extractable metals of MSWI bottom ash in view of its valorization in China

摘要

Metal recovery from bottom ash was deemed to be significant to achieve a higher stability of bottom ash and recycle valuable extractable metals. In China, the existing rugged industrial production ignores the actual metal distribution and thus fails to exploit the utilization potential of recoverable metals in bottom ash. Based on these findings, this work was proposed to obtain a comprehensive and in-depth study on the recoverability of metals in bottom ash. First, the particle size distribution and elemental composition of the bottom ash were analyzed. Then, complete information on the recoverable metals in bottom ash fractions with different sizes was obtained by washing, sorting, crushing, density separation and XRF (X Ray Fluorescence) analysis. The results showed that the smaller than 5 mm fraction accounted for up to 60% of the bottom ash, and the 5-20 mm fractions accounted for about 15%. The material characterization revealed that the contents of recoverable Fe, stainless steel, Al and Cu in bottom ash were averagely 9.01%, 0.136%, 0.78% and 0.08%, respectively. About 50% of Fe, 68% of Al, 61% of Cu, and 22% of stainless steel were distributed in smaller than 10 mm fraction. Particularly, Fe was evenly distributed among 0-2 mm, 2-5 mm, 5-10 mm fractions, and the content was between 5.41% and 7.5%. Non-magnetic stainless steel was mainly distributed in 20-40 mm and larger than 40 mm fractions. The highest share of Al was present in the fractions between 5 mm and 20 mm, accounting for 48% of the total aluminum. About 45.6% of the Cu was enriched in the 5-10 mm fraction. However, the Zn content was less than 0.01%. This work provides an in-depth understanding and information on metal recovery as well as promisingly guide ash utilization.