微波碳热还原—超声波强化浸出富铟锌渣的研究

【作者】 王欣；

【导师】 彭金辉； 杨大锦；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2013， 博士

【摘要】 闪锌矿是湿法炼锌最主要的原料,闪锌矿中常伴生有铁和铟,在焙烧工序时铁与锌结合生成含铟的铁酸锌大量存在于焙砂中。然而,焙砂经现有酸浸工艺处理后浸出渣中仍常含有大量的锌、铟等有价金属,目前传统处理此类浸出渣的方法是采用回转窑烟化后进行再酸浸。但经回转窑挥发的烟尘物相非常复杂,且烟尘中仍有大量的硫酸铅及脉石难溶物,导致再酸浸时锌和铟的回收率仍然较低,使得锌、铟资源损失与此类烟尘浸出渣中。本研究针对以上传统工艺回收铟、锌时存在的问题,以此类锌烟尘浸出渣为原料。利用微波碳热还原使烟尘浸出渣中存在的绝大多数铁酸锌被还原；利用超声波强化浸出过程破坏浸出渣颗粒表面的不溶物PbSO4及SiO2等脉石成分形成的包覆层,大大提高了锌和铟的回收率,具体研究如下：1.开展了常规及微波碳热还原铁酸锌的动力学实验研究,在常规加热950℃,碳和铁酸锌的配比(摩尔比)为1：3,粒径74-61μm,加热时间90min的条件下,铁酸锌的最大还原率达到80%；而在微波加热850℃C,碳和铁酸锌的配比(摩尔比)为1：4,粒径89-74gm,微波功率1800W,加热时间60min的条件下铁酸锌的还原率达到85%,虽然微波加热仅提高了5%的还原率,但其不仅降低了反应温度,还大大缩短了反应时间,同时降低了粒度对还原率的影响,且降低了碳的用量。根据动力学分析可知,常规碳热还原的表观活化能大约为11.47kJ/mol,主要控制步骤为扩散控制；而微波碳热还原的表观活化能为31.40kJ/mol,主要控制步骤为化学反应控制。2.对超声波场特征量分布、浸出液中超声空化效果及矿物颗粒受超声波力的作用变化进行了计算机数值模拟,得到主要结论为：提高浸出液中空化效果所需的较佳工艺条件为超声频率20KHz、声强40w/cm2、气泡初始平衡半径5×10-Sm、环境压力1×10SPa、环境温度70℃。3.通过常规及超声波强化浸出的动力学实验研究发现,在常规浸出硫酸初始酸度170g/L、颗粒粒径61-53μm、固液比1：5、温度85℃、浸出时间240min条件下,锌的浸出率达到82%,钢的浸出率达到80%。在超声波强化浸出超声波超声波频率20kHz、功率260W、硫酸初始酸度140g/L、颗粒粒径74-61μm、固液比1：4、反应温度75℃、浸出时间180min的条件下,锌、钢的浸出率都超过了90%。通过动力学的研究可知,常规浸出锌、铟过程的表观活化能为15.46kJ/mol和19.09kJ/mol,扩散控制为反应的主要控制步骤；超声波强化浸出锌、铟过程的表观活化能为33.90kJ/mol和46.70kJ/mol,表面化学反应控制为反应的主要控制步骤。4.为了得到优化的实验工艺参数,采用响应曲面法分别对常规及特中场强化实验进行优化,得到以下结果：常规加热在92min，904℃时就能够获得最大铁酸锌还原率81.29%,而微波加热条件下比常规加热缩短了23%,温度降低了约114℃,铁酸锌的还原率仍保持在85%以上；而浸出结果显示,在温度降低17℃,加入221W的超声波辅助强化条件下,锌的浸出率由常规工艺80.49%浸出率提高到91.22%,铟的浸出率由常规工艺83.45%的浸出率提高到92.99%。综上所述,论文针对现有处理高铁酸锌和高难溶物含量废渣工艺的不足,首次提出了微波加热-超声波强化联合回收有价金属的技术路线,采有动力学、计算机仿真和响应曲面优化等手段对实验工艺及机理进行研究,并从SEM-EDS、XRD和激光粒度分析等微观角度探讨微波和超声波实验的强化机理。更多还原

【Abstract】 The traditional hydrometallurgy procedures applied for Zinc production are roasting, leaching, purification and electro-deposition. However, the common zinc ore is generally associated with iron, which inevitably leads to the generation of zinc ferrite in the roasting process, meanwhile, Indium associated in zinc ore will also replace iron ion or interstitial manner in the zinc ferrite lattice to generate the Indium based zinc ferrite. Because of the strong stability zinc ferrite, it is hard to be treated by acid leaching in conventional hydrometallurgy process, Zinc and Indium are lost in form of Indium based zinc ferrite in the leaching slag. At the same time, the insoluble lead sulfate usually concentrated on the surface of zinc leaching residue, which would hinder the leaching reaction and lead to the lost of large amount of zinc and indium resource. Tradition methods used to deal with such leaching residue could be rotary kiln volatilization, dust capture and acid leaching. However, it should be noted that the fumes phase of rotary kiln dust is complex, which still contains a lot of smoke full of zinc ferrite and lead sulfate, thus, the recovery rate is still low.With the increasing demand on waste resource recycling, the present paper attempts to treat zinc leaching residue by combination of microwave and ultrasonic for the recovery of zinc and indium. First, the microwave heating with carbon is used to decompose the zinc ferrite in the slag, and then ultrasonic is used to enhance the leaching process to break the insoluble materials such as PbSO4and SiO2gangue composition on the surface of slag particles, some meaningful results are obtained.The dynamics on conventional and microwave heating carbon reduction of zinc ferrite are studied, at the conditions of conventional heating of950℃, C/ZnFe2O4of1:3, particle size of74-61μm and heating time of90min, the maximum reduction rate of zinc ferrite is85%; while at the conditions of microwave heating of850℃, C/ZnFe2O4of1:4, particle size of89-74μm, microwave power of1800W and heating time of60min. the maximum reduction rate is90%. The experimental result indicates that the microwave heating has increased only5%reduction rate, however, it not only reduces both the reaction temperature and the reaction time, but also alleviates the effect of particle size on reduction rate. The apparent activation energy of conventional heating is about11.47kJ/mol, the main control step is diffusion control; the apparent activation energy of microwave heating is about31.40kJ/mol, the main control step is chemical reaction control. The reason might be the characters such as penetrating and selectivity of microwave heating, which could optimize heat and mass transfer.In order to guide the ultrasonic enhancing leaching experiment, Matlab is applied for anticipation and simulation of characteristic value of the sound field and the cavitation effect, the following conclusion are obtained: ultrasonic frequency20KHz, sound intensity40w/cm2、Bubble radius of the initial equilibrium5×10-5m、environment stress1×10Pa% temperature70℃; and the force on the mineral particles appears a sine wave form with the past of time, and with mineral particles movement, the force also show irregular variations.The leaching kinetics on conventional and ultrasonic enhancement experiments is studied. At the conventional leaching conditions of sulfuric acid concentration of170g/L, particle size of61-53μm, solid to liquid ration of1:5, temperature of85℃, and leaching time of240min, the leaching rate of zinc and Indium are82%and80%, respectively. At the ultrasonic enhancing leaching conditions of ultrasonic power of260W, sulfuric acid concentration of140g/L, particle size of74-61μmm solid-liquid ratio of1:4, reaction temperature of75℃and reaction time180min, the leaching rate of zinc and Indium are both in excess of90%. Basing on the above results, the ultrasonic enhancing leaching can raise the leaching rate of zinc and indium for at least10%, the reaction temperature, the reaction time and the sulfuric acid consumption are also greatly reduced, moreover, the influence of particle size on the leaching rate is reduced as well. Based on the kinetics, the apparent activation energy of the conventional leaching on zinc and indium are of15.46kJ/mol and19.09kJ/mol, main control steps are diffusion control; the apparent activation energy of ultrasonic enhancing leaching on zinc and indium are33.90kJ/mol and46.70kJ/mol, the main control step is surface chemical reaction control; the kinetics equation of conventional leaching and ultrasonic enhancing leaching have been obtained.In order to get better experimental parameters, both conventional and unconventional experiments are designed using response surface methodology. Compared with conventional heating, the microwave heating can shorten the reaction time and lower the reaction temperature. The biggest zinc ferrite reduction rate of81.29%for conventional heating is obtained at reaction time of92min and reaction temperature of904℃, in contrast, the reaction time of microwave heating is reduced by23%, the reaction temperature is reduced for about114℃while the reduction of zinc ferrite rate is above85%; while in the leaching process, the model of the optimized zinc and Indium Leaching indicates a temperature reduction of17℃with the assistance of ultrasound enhancement, the zinc leaching rate increased from80.49%to91.22%, Indium Leaching rate increased from83.45%to92.99%.In all, aiming at the existing deficiencies of deal with high zinc ferrite and insoluble substance content residue process.The microwave heating with carbon is used to decompose the zinc ferrite in the residue, and then ultrasonic is used to enhance the leaching process to break the insoluble materials on the surface of slag particles at the first time.Then,using kinetics, computer simulation and response surface optimization to research the experimental process and mechanism, and the SEM-EDS, XRD and laser particle size analysis are used to proved strengthening mechanism of microwave and ultrasonic experiment. In conclusion, an effective way is provided for the recovery valuable metal from the unmanageable residue.更多还原