本文關鍵詞： 等離子體 聚合物 裂解 乙炔 廢棄物 熱力學模擬　出處：《浙江大學》2017年博士論文　論文類型：學位論文

【摘要】：高分子材料在各行業(yè)中得到了非常廣泛的應用,但由于其性質(zhì)穩(wěn)定、體積大且含有各種添加劑,高分子廢棄物比普通城市生活垃圾更難處理,也更具危害。目前高分子廢棄物的處理方法主要有分離復用、熱解、填埋等,但存在應用范圍窄、催化劑要求高、易生成二次污染物等不足。本文利用熱等離子體高溫、高焓、高反應活性的特點,提出磁旋轉(zhuǎn)弧等離子體裂解處理高分子廢棄物的新方法,研究多種不同類型高分子的裂解性能及其規(guī)律,得到富含乙炔的產(chǎn)品氣,為實現(xiàn)高分子廢棄物的無害化和資源化提供了新的可能。本文首先選取了聚乙烯作為直鏈聚烯烴類的代表物質(zhì),系統(tǒng)研究了輸入功率、進料速率、工作氣體流速及勵磁電流對裂解結果的影響。研究表明,在控制體系功率與工作氣體流速較低、適當提高進料速率的情況下,以磁旋轉(zhuǎn)弧氫等離子體裂解聚乙烯可以獲得乙炔含量在10%以上的產(chǎn)品氣,乙炔選擇性與收率分別可以達到85%和75%以上,乙炔比能耗僅為15 kWh/kg-C2H2。利用單位比焓理論及H/C比理論分析了裂解規(guī)律,揭示了裂解技術指標與比焓及H/C比的相關性。以聚丙烯和聚苯乙烯為代表物質(zhì),研究了含有烷基支鏈和芳香環(huán)結構支鏈的聚烯烴的等離子體裂解性能。研究表明,簡單烷基支鏈的存在對聚合物裂解的影響較小,而芳香結構支鏈的存在會導致在高功率下出現(xiàn)較為嚴重的結焦現(xiàn)象,導致產(chǎn)品氣的收率降低。其原因在于芳香環(huán)結構在較低溫度下易于開環(huán)斷裂形成·CH自由基并參與氣化,而在較高溫度下則是結焦的前驅(qū)體。以聚對苯二甲酸乙二醇酯為代表物質(zhì),研究了含氧聚合物的等離子體裂解。研究表明,氧元素在裂解產(chǎn)物中主要以CO的形式存在,CO的形成對乙炔、乙烯等烴類產(chǎn)物的生成有抑制作用,屬于競爭關系,特別是在高功率下,CO是穩(wěn)定性較高的優(yōu)勢產(chǎn)物。同時氧元素的存在對高功率下反應器內(nèi)的結焦有一定的抑制作用。對于含氧量較高的原料,可以采用非氫等離子體裂解制取合成氣。以吉布斯自由能法為原理,利用均相/非均相平衡模型進行了聚合物裂解體系的熱力學平衡計算,結果表明,均相模型的計算結果可以較好地體現(xiàn)氣態(tài)烴類產(chǎn)物的含量隨體系溫度、體系氫碳比的變化趨勢,但不能反映體系結焦的情況;而非均相模型雖然能體現(xiàn)結焦(炭黑)的產(chǎn)生,但是固態(tài)碳在碳元素中所占的比重與實驗結果存在較大差異。結焦越少的體系,均相模型與實驗結果的吻合越好。由于實驗裝置中淬冷段的存在,產(chǎn)品氣中乙炔的含量會有所下降,且生成少部分乙烯、甲烷等在3000～4000K范圍熱力學平衡狀態(tài)下不存在的副產(chǎn)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.
【學位授予單位】：浙江大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：X705

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