【作者】 黄魁；

【导师】 许振明；

【作者基本信息】 上海交通大学 ， 环境工程， 2011， 博士

【摘要】 废旧电池含有毒有害物质及有价值金属元素,有效安全处置与回收废旧电池中有价值金属,不但可以解决目前因废旧电池所造成的环境污染问题,还可以实现资源循环利用,对我国经济、社会和环境可持续发展及再生资源回收利用具有重要意义。然而,目前缺少低成本、环境友好的废旧电池处理与资源化技术,致使废旧电池难以得到安全的处置与高效资源化。本论文基于循环经济的理念及“减量化、再利用、资源化”的原则,以废旧镍镉和镍氢电池为研究对象,首先对废旧镍镉、镍氢电池化学成分和物理结构进行分析,通过物理结构和化学成分分析,确定镉和铁、镍、钴等磁性金属为回收目标金属,并根据废旧镍镉、镍氢电池的物质组成及镉的易挥发性及铁、镍、钴与其它金属间的磁性强弱的差异,提出破碎、真空蒸馏和磁选工艺结合处理废旧镍镉、镍氢电池的新方法。本论文从废旧镍镉、镍氢电池中各金属组元的真空蒸馏分离热力学、动力学角度出发,研究了真空蒸馏分离镉的原理与机制及主要金属元素的真空蒸馏分离规律,并以此作为理论依据,优化真空蒸馏工艺参数,使有害金属镉得到回收。基于金属间的磁性强弱的差异,本论文采用磁选工艺进一步分离与提纯真空蒸馏后的残余物,对废旧镍镉、镍氢电池中铁、镍、钴的磁选分离机理与规律进行研究,以达到对铁、镍和钴这些有价值金属进行回收的目的。基于废镍镉、镍氢电池各组分在同一温度下具有不同的蒸气压,通过真空蒸馏分离工艺,将镉等低熔点高蒸气压金属从混合金属中分离,本文以2/3AA型号废旧镍镉电池为研究对象,探讨了真空蒸馏分离镉的热力学和动力学、氧化-还原反应机理及蒸发-冷凝规律。结果表明:镉在真空蒸馏过程中经历了从氢氧化物到氧化物到单质到蒸气形态的转化。拆解和破碎过程中,有些塑料及纤维没有被分离,而是粘附着电极材料,在真空蒸馏过程中这些塑料及纤维会随着加热温度的升高而发生热解,产生一氧化碳,还原系统中的氧化物。L₁₆（4⁴）正交实验结果表明:真空蒸馏分离可以将镉从不同品牌和形状的镍镉电池中有效回收。在0.1～3.1 Pa的动态压强,1073 K加热温度,2.5小时加热时间,2 wt%活性炭加入量条件下,五种不同品牌、型号和形状的废旧镍镉电池中镉的回收率超过99.5%,回收的镉的纯度超过99%。基于废旧镍镉、镍氢电池中各金属元素的磁性差异,本文通过磁力分选工艺,在不均匀的磁场中,将铁、镍、钴等磁性金属从真空蒸馏后残余物中分离。磁选实验表明,滚径为0.16米的磁选机,在线速度为0.25-0.5 m/s,颗粒粒径在0.5-2毫米范围内时,磁选的分选效果及回收产物的品质均较好,回收率超过97%以上。磁选工艺使真空冶金后镍镉、镍氢电池的残余物得到进一步分离与提纯,该工艺使真空蒸馏工艺变得更简单、更高效,并且有助于金属的进一步分选和回收。环境效益评估结果表明,采用真空蒸馏分离工艺和机械-物理工艺处理废旧镍镉、镍氢电池,电池中的主要金属成分,尤其是毒性较强、含量较多的镉和镍,被转化为可重复利用的产品,该工艺减轻了镉和镍对环境的危害。经济分析结果表明,采用真空蒸馏分离法和机械-物理法回收镍镉、镍氢电池可以带来一定的经济利益,因此,破碎、真空蒸馏和磁选工艺结合处理废旧镍镉、镍氢电池是一种环境友好、经济可行的方法。更多还原

【Abstract】 Waste batteries contain plenty of hazardous materials and valuable metals. Therefore, recycling of waste batteries is an important subject not only from the treatment for waste but also from the recovery of valuable materials. Resource utilization of waste batteries can protect environment and alleviate bottleneck for economic development constrained by resources shortage. However, a serious environmental problem is presented by waste batteries resulting from lack of relevant regulations and effective recycling technologies. Therefore, it is urgent to develop a recycling technology with high performance and without negative impact to the environment to resolve the problems resulting from waste batteries.Based on circular economy concept and the principle of“reduce, reuse and recycling”, this paper considered the recycling of waste Ni-Cd and Ni-MH batteries. In the first stage of this work, the chemical and physical characterization of waste Ni-Cd and Ni-MH batteries was carried out. According to the chemical and physical characterization results, Cd, Fe, Ni and Co were determined to the recycling target metals. A new process including crush, vacuum distillation separation and magnetic separation was proposed through the chemical and physical characterization of waste batteries. Then this paper investigated the thermodynamic and dynamics theory of the recycling of Cd from waste Ni-Cd and Ni-MH batteries by vacuum distillation separation, and use the thermodynamic and dynamics theory and the distillation fundamentals to optimize operating parameters. The residues were magnetically separated after vacuum distillation separation based on the fact that different materials are extremely different in magnetic property. In order to recover major valuable metals, this paper investigated the fundamentals of magnetic separation process to recover Fe, Ni and Co from waste Ni-Cd and Ni-MH batteries.Based on the difference in vapor pressures of various metals at certain temperature, the metal with high vapor pressure and low boiling point （such as Cd, Zn, etc.） were separated from mixed metallic materials by vacuum distillation separation. With the thermodynamic theory and dynamics analysis, it has been shown that the Cd presented in the form from hydroxide to monoxides, and then presented in the form of Cd vapor in 2/3 AA type waste Ni–Cd batteries, respectively. The plastics and fabric used as a base for the electrolyte in waste Ni–Cd batteries, which were not separated during the dismantling and crushing process, generated CO originated from the pyrolysis in vacuum distillation separation process and acted as a reduction agent to reduce oxides.The L₁₆ （4⁴） orthogonal design performed with waste Ni–Cd batteries showed that it was able to effectively recycle cadmium from waste Ni–Cd batteries of different brands and models by using vacuum distillation separation. The recycling efficiency of Cd exceeded 99.5%, with the purity of 99%, in the condition of pressure = 0.1～3.1 Pa, temperature = 1073 K, heating time = 2.5 h, and the addition of carbon powder = 2 wt %, respectively.The residues after vacuum distillation separation were magnetically separated based on the fact that different materials are extremely different in magnetic property in nonuniform magnetic field. The magnetic separation tests performed with waste Ni–Cd and Ni–MH batteries showed that the size of particles between 0.5 and 2 mm and the rotational speed of separator between 0.25 and 0.5 m/s,with the diameter of 0.16 m,were suitable for magnetic separation, with recycling efficiency exceeding 97%. Magnetic separation process enhanced the recycling of waste Ni–Cd and Ni–MH batteries. It made the subsequent metallurgical recovery process more efficient and simpler, was beneficial to the further separation and recycling, and consequently significantly enhance the resource-utilization efficiency.According to environmental impact assessment results, the process including crush, vacuum distillation separation and magneitic separation can recover major heavy metals, particularly Cd and Ni, from the waste Ni-Cd and Ni-MH batteries and convert them into harmless or reusable products. Economic assessment results demonstrated that this new process for recycling of waste Ni–Cd and Ni-MH batteries will be benefits in economical terms in the industry-scale. Therefore,the proposed process including crush, vacuum distillation separation and magneitic separation was an environmentally friendly and economically feasible method.更多还原