高钙特征焚烧飞灰的加速碳酸化处理及对重金属浸出特性的影响

针对生活垃圾焚烧飞灰的高钙含量特征,在室温下采用CO2对焚烧飞灰在液固比(L∶S)为0.25∶1的条件下进行加速碳酸化处理,考察加速碳酸化处理对焚烧飞灰中重金属(As、Cd、Cu、Zn、Sb、Pb)浸出特性的影响.焚烧飞灰XRD分析表明,加速碳酸化处理后飞灰中的Ca(OH)2和CaClOH衍射峰消失,而CaCO3的衍射峰增多,且强度增加.加速碳酸化处理后飞灰中铅的形态发生了改变,并且能够检测到铜的化合物.TG/DTA分析表明,焚烧飞灰在440℃之前增重达到5.70%,SEM-EDS分析证实了Ca(OH)2(s)+CO2(g)→CaCO3(s)反应的发生.焚烧飞灰加速碳酸化处理后的TCLP浸出实验表明,碳酸化时间在2 h内,重金属的浸出浓度除Cd保持不变外都显著下降;而当碳酸化时间超过50 h后,重金属的浸出浓度除Pb外普遍高于飞灰未经碳酸化处理时的浸出浓度.

Accelerated Carbonation of High Ca Content Municipal Solid Waste Incineration Fly Ash and Impact on Leaching of Heavy Metal

The accelerated carbonation of high Ca content Municipal Solid Waste Incineration (MSWI) fly ash was investigated with an L:S ratio of 0.25: 1 to study the effect of accelerated carbonation on the leaching of critical heavy metals (As, Cd, Cu, Zn, Sb, Pb) in the fly ash. The results of XRD analysis showed after carbonation the peaks of Ca(OH)_2 and CaClOH disappeared, while the peaks of CaCO_3 became intense. After carbonation, the mineral phase of Pb was changed and Cu compound (CuTi_(2.05)S_4) was identified. The TG/DTA analysis showed the weight gain of the fly ash before 440℃ reached 5.70% . Furthermore, the SEM-EDS analysis confirmed the occurrence of the reaction of Ca(OH)_2 (s) + CO_2 (g)→CaCO_3 (s) . The TCLP test of carbonated fly ash revealed that the leaching concentration of the critical heavy metals, except Cd, decreased within the carbonation time of 2 h. When the carbonation time was longer than 50 h, the leaching concentration of critical heavy metals, except Pb were higher than that of un-carbonated fly ash.