【作者】 郭进；

【导师】 郭玉文； 张建强；

【作者基本信息】 西南交通大学 ， 环境工程， 2016， 硕士

【摘要】 在资源日益枯竭和节能减排双重背景下,“城市矿产”开发技术已经成为当今社会研究的热点之一。作为“城市矿产”的重要组成部分,废塑料再生不仅可充分利用有限资源创造可观经济价值,同时可有效防止废塑料对环境的污染,具有明显的环境效益和经济效益。不同种类塑料的分离是塑料再生利用过程中的难点,本论文以包装塑料、报废汽车塑料和电子废弃物塑料为研究对象,利用实验室自制浮选设备,通过优化浮选设备参数,利用不同试剂浸润特点选择性调控塑料的可浮性,实现了混合塑料的高效分离,建立了多种废混合塑料的浮选技术流程,为废塑料再生利用提供技术支撑。以分离塑料包装废物中PET为目标,考察了润湿液种类和浓度对浮选效果的影响。结果表明,当选择70mg/L十二烷基硫酸钠作为润湿剂时,一级浮选PET/PVC/PC/PE效果达到最佳,其中PE为上浮料,PET、PVC和PC为下沉料。当使用3mol/L的NaOH改性PET/PVC/PC混合塑料后,选择8mmol/L DBS作为润湿剂时,二级浮选分离PET效果达到最佳,其中96.44%的PET下沉,PVC和PC的上浮率分别达到92.91%、97.45%。通过两级浮选分离回收得到的PET的纯度为90.91%。以分离汽车中4种主体塑料为目标,考察了浮选液流量、溶气罐压力、润湿液浓度等因素对浮选效果的影响。结果表明,当溶气罐压力0.22 MPa、浮选液流量10 L/min,润湿液中ρ(单宁酸)为15 mg/L时,一级浮选PP(聚丙烯)、ABS(丙烯腈-丁二烯-苯乙烯)、PC(聚碳酸酯)、PVC(聚氯乙烯)效果达到最佳,其中PP和ABS的上浮率分别为100%、98.63%,PC和PVC下沉率分别为98.95%、100%；当溶气罐压力为0、浮选液流量6 L/min,润湿液中ρ(单宁酸)为10 mg/L时,二级浮选完全分离PP/ABS;当溶气罐压力0.24 MPa,浮选液流量10 L/min,润湿液采用10 mg/L单宁酸和10 mmol/L癸二酸二丁酯,二级浮选分离PC/PVC效果达到最佳,PC上浮率为92.87%、PVC下沉率为91.41%。通过两级浮选分离,PP、ABS、PC、PVC的最终分离率分别达到100%、98.63%、92.87%和91.41%。为实现PS/ABS混合塑料的浮选分离,考察了润湿液种类和浓度对浮选效果的影响。结果表明,改变湿润剂的种类和浓度对PS/ABS分选影响很大,当润湿液中ρ(单宁酸)为40 mg/L时,PS和ABS再生塑料的上浮率分别为1.08%和100%;当润湿液中ρ(十二烷基硫酸钠)为30mg/L时PS和ABS电子废弃物壳体塑料实现最佳分离效果,其中PS下沉率100%,ABS上浮率98.5%。通过红外光谱分析可知,ABS三种塑料的分子结构相似、导致其具有相近的上浮率,而PS再生塑料和电子废弃物壳体塑料与原生塑料相比分子结构具有较大差异、且亲水性更强,这是PS/ABS再生塑料和电子废弃物壳体塑料均可实现高效分离的关键因素。更多还原

【Abstract】 With the rapid depletion of resource and initiatives of energy conservation and emission reduction today, the study on urban minerals developing tecnology has become the focus. As an important part of urban minerals, waste plastic can not only create considerable economic value by recycling but also reduce plastic polution in the environment, which has obvious environmental and economic benefits. However, it is always a difficulty to separate different kinds of plastics in the recycling process. This paper studied plastics from packaging, End-of-life vehicle and electronic waste with experimental flotation equipment, and achieved efficient separation of various types of plastic mixture, and established the flotation technological process of waste plastics by optimizing equipment parameters and selectively regulating plastic floatability with different reagents, which provided tecnical support for waste plastic recycling.It is difficult to separate interior plastic components of end-of-life vehicles (ELVs) due to their complex types. As flotation has been considered as one of most efficient plastic separation technologies, efficiency of separating interior plastic components of ELVs with flotation technique was exploringly studied in this paper. Aiming at separating four kinds of interior plastic components of ELVs, a designed flotation column was used in laboratory to investigate the effects of parameters, such as flotation fluid flow, dissolved-air tank pressure and wetting agent concentration, on the flotation behaviors. The results showed that the primary flotation of PP/ABS/PC/PVC achieved the optimal effect with PP/ABS as floating materials and PC/PVC sinking materials under 15mg/L of tannic acid as wetting agent. 0.22MPa of dissolved-air tank pressure and 10L/min of flotation fluid flow. Floating rates of PP/ABS were 100% and 98.63% respectively while sinking rates of PC/PVC were 98.95% and 100% respectively. In secondary flotation, PP and ABS were separated completely under 10mg/L of tannic acid as wetting agent, 0MPa of dissolved-air tank pressure and 6L/min of flotation fluid flow. PC/PVC separation in the secondary flotation achieved the optimal effect with PC floating rate being 92.87% and PVC sinking rate being 91.41% respectively, under 10mg/L of tannic acid and 10mmol/L dibutyl sebacate as wetting agent,0.24MPa of dissolved-air tank pressure and lOL/min of flotation fluid flow. After two stages of flotation screening, the separating rates of PP, ABS,PC and PVC finally reached 100%,98.63%, 92.87% and 91.41% respectively, which indicated that the two-stage flotation process developed could achieve effectively separate the four kinds of mixed plastics. The two-stage flotation process developed has broad application prospects in separating interior plastic components of ELVs.Flotation, as one efficient waste plastic separation technology, is an effective method to improve the recycling rate of packaging waste. Polyethylene terephthalate (PET) widely used in packaging industry, has a large number of consumption and high recovery value. Aiming at separating PET from plastic packaging wastes, a designed flotation column was used in laboratory to investigate the effects of parameters, such as wetting agent species and wetting agent concentration, on the flotation behaviors. The results showed that the primary flotation of PET/polyvinyl chloride(PVC)/polycarbonate(PC)/polystyrene(PS)achieved the optimal effect with PS as floating materials and PET/PC/PVC sinking materials under 70mg/L of sodium dodecyl sulfate as wetting agent. When 3mol/L sodium hydroxide used to modify the mixed plastics and 8mmol/L of dibutyl sebacate (DBS) used as wetting agent, PET/PC/PVC separation in the secondary flotation achieved the optimal effect with PET floating rate being 3.56% and PC/PVC floating rate being 97.45% and 92.91% respectively. After two stages of flotation screening, the purity of recycled PET finally reached 90.91%, which indicated that the flotation process developed could effectively separate PET from four kinds of mixed plastics.To separate plastic mixture of PS/ABS, impacts of different wetting reagents at different concentrations on flotation effect of three kinds of mixture were researched. The results showed that, the type and concentration of wetting reagents effected the separation of PS/ABS mixture very much. When the p (tannic acid) in wetting solution was 40 mg/L, floating rates of recycled PS and ABS were 1.08% and 100% respectively. When the p(sodium dodecyl sulfate) was 30mg/L in wetting solution. PS/ABS from electronic waste plastic shell achieved optimum separation, with the PS sink rate 100% and ABS floating rate 98.5%. According to the infrared spectroscopy spectra, similar molecular structures of three kinds of ABS resulted in a similar floating rate. While compared with the molecular structure of virgin PS, molecular structures of recycled PS and PS from electronic waste plastic shell changed much leading to higher floatability.which is the key factor to efficiently separate recycled PS/ABS and PS/ABS from electronic waste plastic shell.更多还原