科研之友
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摘要
There is an urgent need to develop non-landfilled treatment and disposal technology for the aim of innocuity and recycling of municipal solid waste incineration (MSWI) fly ash. In this paper, sewage sludge-assisted hydrothermal coupled pyrolysis process was applied to achieve detoxification and dechlorination of MSWI fly ash, while the silico-aluminum component of sludge was contributed to sinter the end-product to make ceramsite. The solidification behavior and mechanism of harmful heavy metals during the roasting process were analyzed in the meantime. The results indicated that high-strength ceramsite with a classified density of 900~1 200 level could be successfully prepared by firing the green pellets for 20 min at the temperature of 1 200~1 250 ℃ and the optimal compressive strength was up to 19 MPa. Water absorption, harmful substance content (chloride content≤0.0005 %, sulfur content≤0.22%) and other indicators met the requirements of national standards GB/T 17431.1-2010. The calcium aluminosilicate and apatite minerals formed during sintering was conducive to the solidification of heavy metals. The residual fraction accounted for more than 85% of the heavy metals species, and the leaching of heavy metals was lower than the limit in GB 5085.3-2007. The potential ecological risk of heavy metals in the ceramiste was at a slight level as well. Therefore, fly ash originated from sewage sludge-assisted hydrothermal-pyrolysis treatment as raw material for preparing sintered ceramsite is one of the potential ways to realize the safe resource utilization of MSWI fly ash.
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