【作者】 张铭；

【导师】 任其龙； 苏宝根；

【作者基本信息】 浙江大学 ， 制药工程， 2017， 博士

【摘要】 高分子材料在各行业中得到了非常广泛的应用,但由于其性质稳定、体积大且含有各种添加剂,高分子废弃物比普通城市生活垃圾更难处理,也更具危害。目前高分子废弃物的处理方法主要有分离复用、热解、填埋等,但存在应用范围窄、催化剂要求高、易生成二次污染物等不足。本文利用热等离子体高温、高焓、高反应活性的特点,提出磁旋转弧等离子体裂解处理高分子废弃物的新方法,研究多种不同类型高分子的裂解性能及其规律,得到富含乙炔的产品气,为实现高分子废弃物的无害化和资源化提供了新的可能。本文首先选取了聚乙烯作为直链聚烯烃类的代表物质,系统研究了输入功率、进料速率、工作气体流速及励磁电流对裂解结果的影响。研究表明,在控制体系功率与工作气体流速较低、适当提高进料速率的情况下,以磁旋转弧氢等离子体裂解聚乙烯可以获得乙炔含量在10%以上的产品气,乙炔选择性与收率分别可以达到85%和75%以上,乙炔比能耗仅为15 kWh/kg-C2H2。利用单位比焓理论及H/C比理论分析了裂解规律,揭示了裂解技术指标与比焓及H/C比的相关性。以聚丙烯和聚苯乙烯为代表物质,研究了含有烷基支链和芳香环结构支链的聚烯烃的等离子体裂解性能。研究表明,简单烷基支链的存在对聚合物裂解的影响较小,而芳香结构支链的存在会导致在高功率下出现较为严重的结焦现象,导致产品气的收率降低。其原因在于芳香环结构在较低温度下易于开环断裂形成·CH自由基并参与气化,而在较高温度下则是结焦的前驱体。以聚对苯二甲酸乙二醇酯为代表物质,研究了含氧聚合物的等离子体裂解。研究表明,氧元素在裂解产物中主要以CO的形式存在,CO的形成对乙炔、乙烯等烃类产物的生成有抑制作用,属于竞争关系,特别是在高功率下,CO是稳定性较高的优势产物。同时氧元素的存在对高功率下反应器内的结焦有一定的抑制作用。对于含氧量较高的原料,可以采用非氢等离子体裂解制取合成气。以吉布斯自由能法为原理,利用均相/非均相平衡模型进行了聚合物裂解体系的热力学平衡计算,结果表明,均相模型的计算结果可以较好地体现气态烃类产物的含量随体系温度、体系氢碳比的变化趋势,但不能反映体系结焦的情况;而非均相模型虽然能体现结焦(炭黑)的产生,但是固态碳在碳元素中所占的比重与实验结果存在较大差异。结焦越少的体系,均相模型与实验结果的吻合越好。由于实验装置中淬冷段的存在,产品气中乙炔的含量会有所下降,且生成少部分乙烯、甲烷等在3000～4000K范围热力学平衡状态下不存在的副产物。更多还原

【Abstract】 Polymer has been widely used in industry and daily life,due to excellent properties.However,severe pollution problems accompany the wide use of polymer because of its high stability,large size and various additives.Polymer waste treatment is achieved nowadays by recycling,landfill and thermal degradation,which suffer from serious secondary pollution or generation of other toxic substances such as dioxin.This article proposed for the first time a new method of producing high-value gas(C2H2,CO)from polymer waste with a rotating direct current arc plasma technology,creating new opportunities for the utilization of polymer waste.Polyethylene was chosen as the representative material of linear polyolefin.Effects of input power,polyethylene feed rate,working gas flow rate and excitation current on the pyrolysis of polyethylene were systematically studied.The results show that product gas with C2H2 content higher than 10%can be obtained with proper input power,high feed rate and low working gas flow rate.The selectivity and yield of C2H2 can reach 85%and 75%,respectively,with the specific energy consumption of C2H2 as low as 15 kWh/kg-C2H2.The relationship between pyrolysis results and specific enthalpy(Ensp)as well as the ratio of H/C is revealed.Pyrolysis of polyolefins with alkyl side chains or aromatic side chains was studied,with polypropylene and polystyrene selected as representative materials.The results indicate that alkyl side chains has little influence on polymer pyrolysis,while aromatic structure tend to break C-C bond to form CH radical at low temperature and tend to be a coke precursor at high temperature.Polyethylene terephthalate(PET)is pyrolyzed to investigate the plasma pyrolysis of polymers with oxygen.The result shows that oxygen’s presents in product gas is mainly in the form of CO,which would inhibits the formation of hydrocarbon products such as C2H2,C2H4 especially at high input power due to its stability at high temperature.The presence of oxygen favors a lower coke formation.For the materials with high O content,non-hydrogen plasma pyrolysis for the production of syngas is a promising method of utilization.Thermodynamic equilibrium calculation was carried out in single-phase equilibrium model and multi-phase equilibrium model based on the Gibbs energy law.The comparison between the calculated results and experimental results show that the single-phase model is better at predicting the gaseous product,while the multi-phase model takes the coking into account.The calculated results of less coking pyrolysis system is more accurate.The polymer waste pyrolysis equilibrium temperature is 3000-4000 K and side products(C2H4,CH4)do not exist at this temperature.But C2H2 content decreases during the quenching section and a small amount of side products will be produced.更多还原