垃圾焚烧飞灰中重金属浸出的影响因素

INFLUENCE FACTORS OF HEAVY METALS LEACHING FROM AIR POLLUTION CONTROL RESIDUES

考察不同浸出条件对垃圾焚烧发电厂烟气净化系统飞灰中重金属浸出特性的的影响.研究表明:飞灰浸出时,受飞灰自身性质的影响,翻转式摇床混合和水平振荡摇床混合对飞灰中重金属浸出量的影响不明显;混合8h可使浸出体系达到溶解平衡,16h静置过程对飞灰中重金属溶出的影响不明显;增加浸取剂离子强度对飞灰来说并不会增加重金属元素的溶出;加大液固比(L/S)对飞灰中Pb,Ni和Cd的浸出仅起稀释作用,而Cu,Zn,CT和Hg在L/S<10时浸出液的浓度变化不大,L/S>10时被稀释;在高H+浓度时飞灰中重金属的浸出率大大增加,浸取剂中H+对各元素浸出的影响程度为Pb≈Zn>Cu>Cd>Ni>Cr>As>Hg;在中低H+浓度时,醋酸浸出液中重金属的浓度高于硝酸浸出液,而在>0.2mol·1-1的酸浸取液中,硝酸浸出液中重金属(Hg除外)的浓度大于醋酸浸出液.

Study was carried out on the impact of extraction conditions on leaching characteristics of heavy metals in the air pollution control (APC) residues from municipal solid waste incinerator. It was concluded that rotary agitation and horizontal vibration obtained similar effect on heavy metals leaching due to the character of APC residues. 8 hours of shaking time was long enough for the leaching system to reach dynamic equilibrium, and the heavy metals contents showed little variation after the mixture was set down for 16 hours. Because of the high content of soluble salt in the APC residues, enhancing the ion intensity of the leachant did not promote heavy metals solubility. Leaching behavior of heavy metals varied with the liquid to solid (L/S) ratios. For Pb, Ni and Cd, their concentrations in the elute decreased with the L/S ratio due to dilution, so did Cu, Zn, Cr and Hg under high L/S ratio (>10). While the L/S ratio was less than 10, the leaching concentration of Cu, Zn, Cr and Hg changed little. When H+ concentration increased, the leaching ratio of heavy metals increased obviously with the order of Pb≈Zn > Cu > Cd > Ni > Cr > As > Hg. The concentrations of heavy metals in organic acid leachates were higher than that in inorganic acid leachates when the acid concentration was low, while when the acid concentration was more than 0. 2 mol·1-1, the content of heavy metals (except Hg) in inorganic acid was higher than that in organic acid.