Enhanced recovery of zinc and lead by slag composition optimization in rotary kiln

回转窑内渣成分优化实现锌铅元素的高效回收

High-efficiency recovery of Zn and Pb from silicon-rich zinc leaching residues is realized in a rotary kiln.Characterizations by means of XRD,SEM,EDS and ICP reveal that the leaching residue contains 12.4 wt.%SiO_(2),16.1 wt.%Zn,and 7.4 wt.%Pb.Thermodynamic analysis shows that metallic vapor of Zn and Pb can be easily generated from the zinc leaching residue at 1150-1250°C inside the rotary kiln.Viscosities and melting points of 13 slag compositions were analyzed and three slag compositions(47wt.%SiO_(2)-23wt.%CaO-30wt.%FeO,40wt.%SiO_(2)-28wt.%CaO-32wt.%FeO,and 40wt.%SiO_(2)-30wt.%CaO-30wt.%FeO)possessed the desirable physical properties,with the melting point and viscosity in the range of 1150-1280°C and 0.2-0.5 Pa·s,respectively.The industrial tests show that adopting the optimized slag composition can contribute to very high recovery rates of Zn and Pb(97.3%for Zn and 94.5%for Pb),corresponding to slags with very low average contents of Zn and Pb(0.51 wt.%Zn and 0.45 wt.%Pb).The National-Standard leaching tests of the water-quenched slags result in 1.82 mg/L Zn,~0.01 mg/L Cu,0.0004 mg/L As,~0.01 mg/L Cd,0.08 mg/L Pb,and~0.02 mg/L Hg in the leachate,verifying the detoxification of the zinc leaching residue at the same time.

在回转窑内从高硅锌浸出渣中实现高效回收锌铅金属。XRD、SEM、EDS及ICP表征结果表明,浸出渣含12.4%SiO_(2)、16.1%Zn和7.4%Pb(质量分数)。热力学分析表明,在回转窑内1150~1250℃的冶炼环境下,锌浸出渣中极易产生锌和铅的金属蒸气。通过分析13种冶金渣成分的黏度及熔点,发现3种渣成分(47%SiO_(2)-23%CaO-30%FeO、40%SiO_(2)-28%CaO-32%FeO、40%SiO_(2)-30%CaO-30%FeO,质量分数)具有合适的物理特性,即熔点和黏度分别为1150~1280℃和0.2~0.5 Pa·s。工业实验表明,采用优化的渣成分,锌和铅的回收率分别高达97.3%和94.5%,冶炼后渣内锌和铅的含量分别低至0.51%和0.45%(质量分数)。水淬渣的国标浸出实验表明,浸出液中含1.82 mg/L Zn、~0.01 mg/L Cu、0.0004 mg/L As、~0.01 mg/L Cd、0.08 mg/L Pb和~0.02 mg/L Hg,证实锌浸出渣同步实现无害化。