【作者】 张亚莉；

【导师】 李小斌； 于先进；

【作者基本信息】 中南大学 ， 冶金工程， 2012， 博士

【摘要】 在资源紧张和金属价格上涨的情况下,低品位、难处理矿的开发成为我国有色金属工业资源战略的一个重要方向。本文以含银的铁酸锌型低品位氧化锌矿为研究对象,采用现代测试技术,结合机理分析和实验研究,系统深入地研究了锌、铅和银综合提取的工艺和理论。本论文提出了低温焙烧-水浸提锌,浸出液除铁后返锌冶炼系统净化工序,水浸渣再氯盐一步浸出铅银的新工艺。论文首先研究了焙烧过程的热力学,对含锌化合物与硫酸反应进行热力学分析,主要涉及铁酸锌、氧化锌、硅酸锌与硫酸反应的可能性,为低品位氧化锌矿焙烧-水浸提锌工艺的提出及研究提供理论依据；在锌提取阶段,比较直接酸浸和焙烧-水浸两种方案发现,采用焙烧-水浸提锌效果最好。通过XRD、 SEM-EDS等测试分析,明确焙烧前后、水浸后主要元素的物相变化；实验研究了焙烧温度、焙烧时间、硫酸用量、水浸液固比、水浸时间、水浸温度和搅拌速度对锌浸出率的影响及该过程中其它金属元素的行为。结果表明,焙烧参数对锌浸出率影响较大,水浸参数影响较小。在下列条件下锌的浸出率达到80%以上：硫酸用量为矿质量的70%,焙烧时间和温度分别为2.5h和523K；焙砂在室温和液固比为4时浸出0.5h。对锌浸出液采用双氧水氧化中和除铁,除铁效果较好。对体系中银和铅的相关固相化合物在氯盐体系的溶解特性进行了研究。运用双平衡原理,确定了体系中各种离子的平衡浓度,绘制了浓度关系图。这为铅银的氯盐一步浸出工艺提供了理论依据。研究了铅银的氯盐一步浸出动力学机理,该浸出过程是典型的液固多相反应,通过试验发现其符合未反应核收缩模型,当搅拌速率大于400r/min时,排除了外扩散对浸出过程的控制；采用化学反应控制和内扩散控制模型对浸出反应进行拟合,确定了速率控制步骤为内扩散控制；在实验基础上,通过计算得到铅、银浸出的表观反应活化能分别为26.8kJ·mol-1和26.5kJ·mol-1,浸出过程受温度影响较大。铅银浸出的动力学半经验方程为：根据动力学分析可知,铅、银浸出反应的速率和粒径成反比,与氯盐浓度成正比。研究了水浸渣中铅银的氯盐一步浸出工艺。考察了NaCl浓度、添加剂用量、液固比、酸度和浸出时间对浸出率的影响。结果表明：加入添加剂对铅浸出率没有影响,但可以提高银的浸出率。铅、银的浸出率随氯盐浓度、液固比的增加而增加；盐酸加入量对铅的浸出影响较小,对银的浸出影响较大。温度在60℃以下时,铅、银的浸出率较低。铅银氯盐一步浸出的最佳工艺条件为：反应温度90℃,NaCl浓度390g/L,添加剂用量15mL/10g渣,液固比7：1,HC1加入量3mL/10g渣,浸出时间3h。该条件下铅的浸出率达到95%,银的浸出率达到90%。更多还原

【Abstract】 With the depletion of ores and rapid rising of the metal price, the processing of low grade, difficult processing ore becomes an important strategic aspect of the nonferrous metal industry. Theoretical and technical studies on the extraction of the valuable metals from low grade zinc ores in details were carried out with the modern testing technology and some meaningful conclusions were obtained.A new process of "low temperature roasting-water leaching, leaching solution returned to purifying process in zinc smelting system after removal of iron, chloride leaching of silver and lead from slags after water-leaching" was proposed. The thermodynamics was studied which was mainly related to the possibility of reactions about franklinite, zinc oxide, zinc silicate and sulfuric acid. This will provide the theoretical basis for the research on the processing of low grade zinc oxide ore by roasting-water leaching. At the stage of zinc extraction, according to mineral analysis by XRD、EDS and SEM, the phasa transitions were determined before and after roasting and water-leaching; the effects of various parameters, such as roasting temperature, roasting time, the amount of sulfuric acid, leaching time, leaching temperature, and liquid/solid ratio on zinc leaching rate were studied. Systematic studies indicate that high zinc leaching rate can be achieved under the following conditions:sulfuric acid addition,70%weight of zinc oxide ore; duration,2h; temperature,250℃at roasting stage; and room temperature, liquid/solid ratio4, and duration time0.5h at leaching.In this work, the dissolving characteristic and the condition converting to another phase of each phase in the systerm were studied; the equilibrium concentrations of various ions were determined based on simultaneous balance principle and charge muutrality in Ag2SO4-PbSO4-HCl-NaCl-H2O system. These provide theoretical basis for chloride leaching of silver and lead simultaneously.The dissolution kinetics of silver and lead by chloride simultaneously from residues after zinc extraction have been investigated.The dissolution kinetics followed a shrinking core model, with inter-diffusion through gangue layer as the rate determining step. This finding is in accordance with the apparent activation energy (Ea) of26.8kJ/mol (Ag) and26.5kJ/mol (Pb), and a linear relationshipbetween the rate constant and the reciprocal of squared particle size. The order of reaction with respect to sodium chloride concentration, temperature andparticle size were also achieved. The rate of reaction based on diffusion-controlled processcan be expressed by semi-empirical equations.The process of treating the residue after zinc extraction by chloride leaching was developed. The effects of experimental conditions, such as reaction temperature, sodium chloride concentration, liquid-solid ratio, acidity as well as reaction duration, were investigated. The results show that the additive does not affect leaching rate of lead while it can increase leaching rate of silver significantly. The leaching rate of silver and lead were augmented with increasing the concentration of sodium chloride and liquid-solid ratio; the amount of hydrochloric acid has little influence on the lead extraction, but has more effect on that of the silver. The optimum process conditions are obtained, which are leaching temperature90℃, sodium chloride concentration390g/l, additive amount15ml/10g residue, liquid-solid ratio7:1, acidity3ml/10g residue, time3h. Under these conditions leaching rates of lead and silver can reach about95%and90%.更多还原