聚乙烯在等离子体射流水平床内的热解特性

Characteristics of Pyrolyzing Polyethylene in a Horizontal Plasma Jet Reactor

为了强化等离子体射流与有机固体废弃物的混合接触和反应特性,提出了一种有别于常规下行床结构的水平床,并以有机固体废弃物中的聚乙烯(PE)为热解对象,研究了直流电弧氮等离子体射流水平床内PE的热解特性,考察了PE进料速率对热解产物的分布影响,并比较了不同反应器结构参数下的PE热解气体产物中氢气浓度。结果表明,PE热解产物中以氢气和纳米炭黑为主,有少量的低碳烃。进料速率对热解气体主产物氢气浓度的影响最大,而对低碳烃浓度影响甚小。作为水平床中连接等离子体射流与反应腔的中间石墨接头的出进口直径比越大,越有利于PE穿越等离子体射流的湍流边界进入射流的高温区域,更好地热解制氢。水平床反应腔内的保温石墨管的长度对水平床出口氢气浓度影响不大,PE热解反应在水平床的石墨接头内已迅速完成。

In order to strengthen interaction of plasma jet flow with organic solid waste （OSW）, a laboratory-scale horizontal direct current electric arc thermal plasma jet reactor was developed and the characteristics of polyethylene （PE） pyrolysis were investigated in the plasma jet reactor using N2 as working gas. Effects of PE feed rate on the products distribution of plasma pyrolysis were examined, as well as the effects of structural parameters of plasma jet reactor on H2 concentration at outlet. The results showed that H2 and nano black carbon were obtained as the main products, with a small amount of low molecular hydrocarbon. PE feed rate had the greatest effect on H2 concentration at outlet, little effect on the outlet concentration of low molecular hydrocarbon. The graphite joint functioned as the link of plasma jet and reaction chamber in the plasma jet reactor, as well as the entrances of plasma jet and PE feedstock. The higher the ratio of outlet diameter to inlet diameter in graphite joint, the more easily the PE feedstock crossed the turbulent boundary layer of plasma jet and entered into the high temperature region, thus the pyrolysis of PE could be promoted and H2 yield of plasma pyrolysis was improved. The length of insulation graphite tube packed in the reaction chamber of the plasma jet reactor played little effect on the generation of Ha, which meaned PE pyrolysis process finished in graphite joint.