【作者】 阮菊俊；

【导师】 许振明；

【作者基本信息】 上海交通大学 ， 环境工程， 2012， 博士

【摘要】 电子废弃物蕴含丰富的资源,被称为“城市矿山”。目前,国内外电子废弃物的处理与资源化过程中普遍存在着资源利用效率低、技术及装备简易落后、易带来二次污染等问题。开发新工艺、新设备成为电子废弃物资源化领域的迫切需求。本文在分析了废弃硒鼓、废旧冰箱箱体物料组分的基础上,设计了废弃硒鼓、废旧冰箱箱体资源化工艺。建立了涡流分选的涡流力模型,颗粒分离距离计算模型,为废弃硒鼓、废旧冰箱箱体资源化关键技术涡流分选提供理论基础。在理论分析的基础上,构建了废弃硒鼓、废旧冰箱箱体资源化生产线,并对生产线各工序的操作参数进行了优化,实现了废弃硒鼓、废旧冰箱箱体的破碎解离-涡流分选。并对废弃硒鼓、废旧冰箱箱体资源化生产线进行了环境风险分析。在分析废弃硒鼓和废旧冰箱箱体物料组分的基础上,分别提出了废弃硒鼓的封闭破碎、旋风/除尘、磁选、涡流分选和废旧冰箱箱体的封闭破碎-活性炭吸附-气流分选-磁选-涡流分选的回收工艺。涡流分选由于影响因素众多,生产中分离效率低,难以满足生产需要。通过正交试验设计的方法,研究了涡流分选过程中操作参数对涡流分选的影响。实验结果表明磁辊转速与输送带喂料线速度之差(ωR-v)为影响涡流分选的关键因素,输送带喂料速度(v)为一般因素,接料位置(H)为次要因素。喂料速度越小,磁辊转速与输送带喂料线速度之差越大,分选效果越好;接料位置0.9 m为实验室涡流分选机最佳接料位置。建立了涡流分选涡流力模型,并通过对颗粒运行轨迹中脱离角(α0)的计算表明,计算结果与实验结果相吻合。与以前模型相比,新建的模型增加了对颗粒因素(圆形颗粒半径,矩形,三角形片状颗粒的长、宽、高、周长)和磁辊参数(磁辊直径,磁辊表面磁场强度)的分析。新建的涡流力模型可用来指导涡流分选操作参数调节,涡流分选机结构设计,和物料的破碎。建立了涡流分选颗粒分离距离计算模型,对颗粒运行轨迹中磁场逃逸点进行了研究。与以前模型相比,新模型增加了磁场边界、接料位置等涡流分选影响参数。模型可用来预测涡流分选效果。模型建立过程中得出了颗粒尺寸因素>磁场转速因素>颗粒形状因素的涡流分选影响因素关系。根据涡流力模型和颗粒分离距离计算模型总结出了提高涡流分选分离效率的方法,并在此基础上设计了分选性能更好的涡流分选机。根据设计的工艺,采用新设计的涡流分选机及其它机械设备,分别构建了废弃硒鼓、废旧冰箱箱体资源化生产线,并通过总结出的提高涡流分选的方法与实验对生产线涡流分选工序及其它工序的操作参数进行了优化。(i)废弃硒鼓资源化生产线优化的操作参数为:破碎机转速1200 rpm,筛网筛孔尺寸15 mm,破碎机装备冷凝水系统;旋风分离器风机风速1.4 m/s;布袋除尘器风机风速0.3 m/s;磁选机转速350 rpm (3.3 m/s);涡流分选机喂料速度40 rpm (0.4 m/s),磁辊转速800 rpm (7.5 m/s)。生产线总功率190 kW,回收能力500 kg/h,回收率98.2 %。(ii)废旧冰箱箱体资源化生产线优化的操作参数为:破碎机转速1800 rpm,筛网筛孔尺寸10 mm,破碎机外壁装备冷凝水系统;活性炭吸附塔风机转速1200rpm,管道气流入口筛网筛孔孔尺寸0.5 mm;气流分选机风机风速0.95 m/s;磁选机转速350 rpm (3.3 m/s);涡流分选机喂料速度: 40 rpm (0.4 m/s),磁场转速1000 rpm (7.5 m/s)。生产线总功率240 kW,回收能力773.8 kg/h,回收率达97.6%。对废弃硒鼓资源化生产线噪声排放水平、空气颗粒物浓度、碳粉泄漏情况,对废旧冰箱箱体资源化生产线噪声排放水平,CFC-11泄漏情况,空气颗粒物浓度及其中重金属浓度,和各工序余灰中重金属浓度进行了监测和分析。(i)废弃硒鼓资源化生产线环境风险分析结果为:破碎,搅拌-磁选工序噪声排放水平超过90 dB(A)(职业安全健康噪声标准),采用隔声罩处理后,噪声排放水平降至67.6 dB(A);空气颗粒物浓度(TSP、PM10)达我国室内空气质量标准,TSP中碳粉有机组分浓度最高为0.026 mg/m3,PM10中未检测到碳粉有机组分,生产线不存在碳粉泄漏危害人体健康的危险。(ii)废旧冰箱箱体资源化生产线环境风险分析结果为:破碎工序噪声水平超过90 dB(A)(职业安全与健康噪声标准),经隔声罩处理后噪声水平降至69.7dB(A);破碎机和气流分选机附件检测到浓度6-9 mg/m3和5-7 mg/m3的CFC-11气体,其值低于我国规定的氟化物排放浓度标准(11 mg/m3);破碎机腔内CFC-11浓度较高(216-739 mg/m3),但由于活性炭吸附塔的作用,车间内和活性炭吸附塔气流出口处均未检测到CFC-11气体;空气颗粒物(TSP、PM10)浓度符合我国室内空气质量标准,且其中重金属浓度不会威胁人体健康;生产线余灰中检测到铜(1672-11925 mg/kg)、铅(356.1-11490 mg/kg)、锡(211.9-686.5 mg/kg)三种重金属,铜的最高浓度超过土壤环境质量标准30倍,铅的最高浓度超标20倍。以上研究为破碎废弃硒鼓、废旧冰箱箱体涡流分选提供了理论基础,提出了高效、环保、经济可行的废弃硒鼓、废旧冰箱箱体无害化处置方法,同时也为回收其它电子废弃物提供了技术储备与参考。更多还原

【Abstract】 E-waste has been considered as“city-mine”due to containing aboundant metals. However, there was a lack in recovery technology and heavy secondary pollution had been produced. Developing new technologies and equipments have been the pressing demand for recovering e-waste. In this study, recovery technologies of waste toner cartridges (TCs) and refrigerator cabinets (RCs) were proposed based on the analysis of their components. Eddy current separation was employed as a key technology in the recovery technologies. Then, for improving the separation rate of eddy current separation (ECS), model of eddy current force and models for calculating the separation distance between different kinds of particles were constructed. Based on the proposed recovery technologies, production lines for recovering waste TCs and RCs were constructed and the operation paramenters of every process were studied. In finals, risk assessments of the recovery lines were made on their environment-friendly performance.Based on the analysis of comprised materials and pollution factors, a recovery technology of waste TCs was proposed including closed shearing, cyclone separation, bag-type dust collection, magnetic separation, and ECS. For preventing the leakage of CFC-11 gas, recovering technology of waste RCs was proposed after analysing the comprised materials. It included closed shearing, activated carbon adsorption, air current separation, magnetic separation, and ECS.In the recovery technologies of waste TCs and waste RCs, separation rate of ECS was low because of its abundant influenced factors. According to orthogonal experimental design, operation parameters of ECS were investigated. The experimental results indicated that speed difference between feeding speed and rotation speed of magnetic field (ωR-v) was the key influencing factor. Feeding speed was general influencing factor. Collection position of particles was subordination influencing factor. Separation rate was improved as the increasing of (ωR-v) and the decreasing of feeding speed. Collection position 0.9 m was the optimizing parameters of the eddy current separator in lab.New models for computing the acting force between particle and eddy current separator were established for guiding operation of ECS, configuration design of separator, and shearing mode of materials. The models were tested by the calculation and investigation of detachment angle (α0) of particle in ECS. Compared to former models, new models had the advantage on providing more detailed shape parameters of particle such as radius, length, width, thickness, and circumference. Furthermore, influencing factors of magnetic drum radius and magnetic field intensity of separator surface were added in the new models.Models for calculating separation distance between different particles in ECS were established for investigating the influencing factors. The models can be used to forecast separation quality of ECS by calculating the separating distances. Based on the analysis of the calculated separation distances, sequence of the influencing factors was derived as: particle size>rotation speed of magnetic field>shape of particle. Then, the approaches for improving the separation quality of eddy current separation were discussed. A new eddy current separator was designed for obtaining better separation quality according to the suggestion of the approaches. Additionally, the investigation of the exiting point of particle from magnetic field boundary extended the scope of theoretical investigation of ECS.Production lines of recovering waste TCs and waste RCs were constructed in enterprise based on the proposed recovery technologies. The operation parameters of every process were researched.(i) Optimized operation parameters of the recovering line of waste TCs were given in follows. Rotation speed of shearing machine was 1200 rpm, size of screen hole of shearing machine was 15mm, and circulating water should be fixed on shearing machine. Wind speed of the fans of cyclone separation and bag-type dust collector were 1.4 m/s and 0.3 m/s respectively. Rotation speed of magnetic separator was 350 rpm (3.3 m/s). Feeding speed of eddy current separator was 40 rpm (0.4 m/s), rotation speed of magnetic drum was 800 rpm (7.5 m/s).The recovery capability of waste TCs recovery line was 500 kg/h and recovery rate was 98.2% with the power demand 190 kW.(ii) Optimized operation parameters of the recovering line of waste RCs were given in follows. Rotation speed of shearing machine was 1800 rpm, size of the screen hole of shearing machine was 10mm, and circulating water should be fixed on shearing machine. Rotation speed of the fan of activated carbon adsorption tower was 1200 rpm. Wind speed of the fan of air current separator was 0.95 m/s. Rotation speed of magnetic separator was 350 rpm (3.3 m/s). Feeding speed of eddy current separator was 40 rpm (0.4 m/s), rotation speed of magnetic drum was 1000 rpm (7.5 m/s). The recovery capability of waste RCs recovery line was 773.8 kg/h and recovery rate was 97.6% with the power demand 240 kW.Risk assessment of the recovering line of waste TCs were made on noise level, density of airborne particles, and leakage of toner in recovering process. Risk assessments of the recovering line of waste RCs were made on noise levels, leakage of CFC-11, density of airborne particles, and the exposure of heavy metals in the recovering process.(i) Results of risk assessment of the recovering line of waste TCs were given in follows. Noise levels of shearing and agitating-magnetic separation exceeded 90 dB(A) (Occupational Safety and Health Standards). After employing acoustic hood, the noise level was controlled to 67.6 dB(A). Concentrations of airborne particles (TSP、PM10) met the the Indoor Air Quality Standard of Chinese. The highest density of organic particles from toner in TSP samples was 0.026 mg/m3, and little organic particle was found in PM10 samples. It meant that little risk was brought to human healthy by organic particle of toner in recovering process.(ii) Results of risk assessment of the recovering line of waste RCs were given in follows.Noise levels of shearing process exceeded 90 dB(A) (the Occupational Safety and Health Standards). After employing acoustic hood, the noise level was controlled to 69.7 dB(A). Concentrations of CFC-11 around shearing machine and air current separation were 6-9 mg/m3 and 5-7 mg/m3, lower than the concentration of fluoride in Ambient Air Quality Standard of Chinese. Although high concentration (216-739 mg/m3) of CFC-11 was detected in the inner of shearing machine, little CFC-11 was detected in workshop and the gas outlet of actived carbon adsorption tower due to its running. the concentrations of airborne particles (TSP、PM10) met the Indoor Air Quality Standard of Chinese and the concentration of heavy metals in TSP and PM10 were safe for workers. High concentrations of copper (1672-11925 mg/kg), lead (356.1-11490 mg/kg), and tin (211.9-686.5 mg/kg) were detected in the residual ashes of the recovering line, and concentrations of copper and lead exceeded the heavy metal concentrations in Environment Quality Standard for Soils thirtyfold and twentyfold respectively.This study offered the theoretical basis of eddy current separation for recovering waste toner cartridges and refrigerator cabinets. Meanwhile, high-efficiency, environment-friendly, and cost saving production lines for recovering waste toner cartridges and refrigerator cabinets were developed. The works of this study may contribute little to the technology informations for e-waste recovering.更多还原