污泥辅助飞灰水热-热解处置产物制备陶粒

Preparation of ceramsites with fly ash originated from sewage sludge-assisted hydrothermal coupled pyrolysis process

应开发非填埋式飞灰无害化与资源化处理处置技术的迫切需要,采用污泥辅助水热耦合热解工艺对飞灰进行脱毒脱氯,利用污泥的硅铝质组分辅助飞灰水热-热解处置产物制备陶粒;并阐明了烧结过程有害重金属的固化行为与固化机制。结果表明,在1200~1250℃的温度下,烧制20 min可成功制备密度等级为900~1200级的高强陶粒;其最优抗压强度超过19 MPa,吸水率、有害物质含量(氯化物含量≤0.0005%,硫含量≤0.22%)等指标均符合GB/T 17431.1-2010国家标准。高温焙烧过程形成的铝硅酸钙和磷灰石矿物有助于重金属的固化稳定。陶粒的残渣态重金属比例超过85%,浸出毒性低于GB 5085.3-2007规定的限值,重金属潜在生态风险处于轻微水平。飞灰经污泥辅助水热-热解处置后的产物制备陶粒可作为飞灰资源化利用的途径之一。

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 sludgeassisted 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 of900~1 200 level could be successfully prepared by firing the green pellets for 20 min at the temperature of1 200~1 250 ℃ and the optimal compressive strength was up to 19 MPa. Water absorption, harmful substance content(chloride content≤0.000 5 %, 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.