电弧炉熔融医疗垃圾焚烧灰的实验研究

Experimental Study on Melting of Hospital Waste Incineration Ash by Electric Arc Furnace

利用处理量为2 kg的直流电弧炉对医疗垃圾焚烧的底灰、底灰与布袋飞灰的混合灰分别进行熔融实验研究,并比较了熔融前后灰和熔渣的化学成分、物相、微观形貌、浸出毒性及重金属残留率．结果表明,底灰主要由复杂的硅酸盐晶体组成,布袋飞灰含有大量的硬石膏(CaSO_4)、氯化钠(NaCl)晶体,熔融后两种熔渣均为无定形非晶态的玻璃熔岩．底灰、混合灰熔融后减容率分别达到78％和80．5％;熔融前布袋飞灰浸出液中Pb,Cd,Zn浓度远超过危险废物填埋限值,熔融后的熔渣中重金属固化在Si-O网格中,渗沥液中浓度极低,完全符合环保要求．熔融后2种熔渣中Pb,Cd,Zn的残留率较低,而且混合灰熔渣中重金属残留率均低于底灰熔渣．

The pilot-scale melting experiment of hospital waste incineration ash using a 2 kg DC electric arc furnace was carried out. The melting characteristics of bottom ash alone, and a mixture of bottom ash with bag fly ash were examined in terms of chemical composition, mineralogy, morphology, leaching behavior and residual fraction of heavy metals. The experimental results indicate that the bottom ash mainly consists of silicates, and major crystalline phases of bag fly ash are CaSO4 and NaCl, two kinds of melted slag are single-phase amorphous, glassy product. Volume reductions of two slags in comparison to the bottom ash and mixed ash respectively reach 78% and 80.5%. The Pb, Cd and Zn leaching concentrations of bag fly ash far exceed the hazardous waste landfill regulatory thresholds, the obtained slag is environmentally acceptable, possibly because heavy metals in the slag are combined into the Si-O network by the melting process. Residual fractions ofPb, Cd and Zn in two slags are low, and residual fraction of heavy metals in sample SLAG2 is lower than that in sample SLAG1.