城市矿产中废塑料浮选分离技术研究

发布时间：2018-09-02 08:59

【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。
[Abstract]:Under the dual background of resource depletion and energy saving and emission reduction, the development technology of "urban mineral" has become one of the hotspots in the society. As an important part of "urban mineral resources", the recycling of waste plastics can not only make full use of limited resources to create considerable economic value, but also effectively prevent waste plastics from polluting the environment. It has obvious environmental and economic benefits. The separation of different kinds of plastics is a difficult point in the process of recycling and utilization of plastics. In this paper, packaging plastics, scrap plastics and electronic waste plastics are taken as research objects, and the parameters of floatation equipment are optimized by using self-made floatation equipment in laboratory. The floatability of plastics was controlled selectively by using the characteristics of different reagents soaking, the high efficient separation of mixed plastics was realized, and the flotation process of various waste mixed plastics was established, which provided technical support for recycling and utilization of waste plastics. In order to separate PET from plastic packaging waste, the effect of wetting liquid type and concentration on flotation effect was investigated. The results show that when 70mg/L sodium dodecyl sulfate is chosen as the wetting agent, the effect of first-order flotation PET/PVC/PC/PE is the best, in which PE is the floating-agent and the PC is the sinking material. When NaOH was used to modify PET/PVC/PC mixed plastics, 8mmol/L DBS was chosen as the wetting agent, the effect of secondary flotation separation of PET was the best, and the floatation rates of 96.44% PET and PC reached 92.91% and 97.45% respectively. The purity of PET obtained by two-stage flotation separation and recovery is 90.91%. The effects of the flow rate of flotation liquid, the pressure of dissolved gas tank and the concentration of wetting liquid on the flotation effect were investigated. The results show that when the flow rate of flotation liquid is 10 L / min at the pressure of 0.22 MPa, and the 蟻 (tannic acid) in the wetting liquid is 15 mg/L, the first stage flotation of PP (polypropylene) MPa, (acrylonitrile-butadiene-styrene) PC (polycarbonate) polyvinyl chloride (PVC) is the best. The floatation rates of PP and ABS are 100 and 98.63, respectively. The sinking rates of PC and PVC are 98.95 and 100, respectively. When the pressure of dissolved gas tank is 0, the flow rate of flotation liquid is 6 L / min, and the 蟻 (tannic acid) in wetting liquid is 10 mg/L, PP/ABS; was completely separated by secondary flotation when the flow rate was 10 L / min at the pressure of 0.24 MPa, 10 mg/L tannic acid and 10 mmol/L dibutyl sebacate were used in the wetting liquid, and the best floatation efficiency of PC/PVC was 92.87% and 91.41%. The final separation rate of PPS-ABSP-PC-PVC by two-stage flotation is 100 ~ 98.6392.87% and 91.41% respectively. In order to realize the flotation separation of PS/ABS mixed plastics, the effects of the type and concentration of wetting solution on the flotation effect were investigated. The results show that changing the type and concentration of wetting agent has great influence on the separation of PS/ABS. When 蟻 (tannic acid) in wetting solution is 40 mg/L, the floatation rates of PS and ABS regenerated plastics are 1.08% and 100, respectively. When 蟻 (sodium dodecyl sulfate) in wetting solution is 30mg/L, the best separation effect is achieved for PS and ABS electronic waste shell plastics. The sinking rate of PS is 100% and the floating rate of ABS is 98.5%. The IR spectrum analysis shows that the molecular structure of the three plastics is similar, which leads to similar floating rate, while the molecular structure of the recycled plastics and electronic waste shell plastics is different from that of the original plastics, and the hydrophilicity of the plastics is stronger than that of the original plastics. This is a key factor for the efficient separation of PS/ABS recycled plastics and electronic waste shell plastics.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X705

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