磁旋转弧等离子体技术处理高分子废弃物的研究

发布时间：2018-01-26 17:52

本文关键词： 等离子体聚合物裂解乙炔废弃物热力学模拟　出处：《浙江大学》2017年博士论文　论文类型：学位论文

【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。
[Abstract]:Polymer materials have been widely used in various industries, but because of their stable properties, large volume and various additives, polymer wastes are more difficult to deal with than ordinary municipal solid waste. At present, the main treatment methods of polymer waste are separation and reuse, pyrolysis, landfill and so on, but the scope of application is narrow, and catalyst requirements are high. Based on the characteristics of high temperature, high enthalpy and high reaction activity of thermal plasma, a new method of treating polymer waste by magnetic rotation arc plasma pyrolysis is proposed in this paper. The cracking properties and laws of many kinds of polymers were studied and the acetylene rich product gas was obtained. In this paper, polyethylene is selected as the representative material of straight chain polyolefin, and the input power and feed rate are studied systematically. The effect of working gas velocity and excitation current on the pyrolysis results. The results show that under the condition of controlling the system power and working gas velocity and increasing the feed rate properly. The product gas with acetylene content above 10% can be obtained by pyrolysis of polyethylene by magnetic rotation arc hydrogen plasma. The selectivity and yield of acetylene can reach 85% and 75% respectively. The specific energy consumption of acetylene is only 15 kWh-1 / kg-C2H2.The cracking law is analyzed by the theory of unit specific enthalpy and H / C ratio. The correlation between pyrolysis technical parameters and specific enthalpy and H / C ratio was revealed. Polypropylene and polystyrene were used as representative materials. The plasma cracking properties of polyolefin containing alkyl branched chain and aromatic ring branched chain were studied. The results showed that the existence of simple alkyl branched chain had little effect on the polymer cracking. The existence of aromatic branching chain will lead to serious coking phenomenon at high power. The reason is that the aromatic ring structure is easy to break open at low temperature to form 路Ch radical and participate in gasification. The plasma pyrolysis of the oxygen-containing polymer was studied with polyethylene terephthalate as the representative material at higher temperature. The formation of CO in the pyrolysis products is mainly in the form of CO, which can inhibit the formation of hydrocarbon products such as acetylene and ethylene, which belongs to the competition relationship, especially under the high power. Co is the dominant product with high stability. At the same time, the presence of oxygen element can inhibit coking in the reactor at high power. Synthesis gas can be produced by non-hydrogen plasma pyrolysis. The thermodynamic equilibrium of polymer pyrolysis system is calculated by using homogeneous / heterogeneous equilibrium model on the basis of Gibbs free energy method. The calculated results of homogeneous phase model can well reflect the change trend of gaseous hydrocarbon products content with the system temperature and the ratio of hydrogen to carbon, but it can not reflect the coking of the system. Although the heterogeneous model can reflect the formation of coking (carbon black), the proportion of solid carbon in the carbon element is different from the experimental results. Due to the existence of quenching section in the experimental equipment, the content of acetylene in the product gas will decrease, and a small part of ethylene will be produced. Methane and other byproducts that do not exist in the thermodynamic equilibrium state of 3000 K.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X705

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