废塑料与兰炭混合燃烧动力学分析

Kinetic Analysis of Mixed Combustion of Waste Plastics and Semi-coke

通过热重法研究了废塑料和兰炭混合物的燃烧特性,分析了着火温度(Ti)、燃尽温度(Tf)、燃烧率(x)、点火指数(C)、综合燃烧特性指数(S)等参数的变化规律。运用体积模型(VM)、随机孔模型(RPM)和未反应核心模型(URCM)三种动力学模型对混合物的燃烧率曲线进行计算,得到不同的拟合曲线,比较拟合效果。结果表明:废塑料和兰炭混合物的燃烧过程由少量水分蒸发、挥发分析出、固定碳燃烧三个阶段组成。在兰炭中添加废塑料会改善兰炭的燃烧性能,随着废塑料配加量的增加,混合物的着火温度降低,平均燃烧速率、点火指数和燃烧特性指数均增加;增大升温速率对混合物的燃烧有促进作用。在三种动力学模型中,随机孔模型(RPM)的拟合结果优于体积模型(VM)和未反应核心模型(URCM)的拟合结果;由RPM模型计算的活化能E和指前因子k0具有相同的变化规律,存在明显的'补偿效应';随着废塑料配加量的增加,活化能先降低后增加,表明废塑料和兰炭混合燃烧存在协同效应。

The combustion characteristics of waste plastic and semi-coke mixture were studied with thermogravimetric method.The variation rules of ignition temperature(Ti),burnout temperature(Tf),burning rate(x),ignition index(C)and comprehensive combustion characteristic index(S)were analyzed.Three kinds of kinetic models about volume model(VM),random pore model(RPM)and unreacted core model(URCM)were used to calculate the burning rate curve of the mixture,and different fitting curves were obtained to compare the fitting effects.The results show that the combustion process of the blend consists of three stages:evaporation of a small amount of water,seperation of volatilization,and combustion of fixed carbon.Addtion of waste plastics to the semi-coke will improve the combustion performance of the semicoke.With the amount of waste plastics increasing,the ignition temperature of the mixture decreases,while the average burning rate,ignition index and combustion characteristic index increase.The increase of the heating rate will promote the combustion of the mixture.By comparing three models,the fitting results of random hole model(RPM)are superior to the volume model(VM)and the unreacted core model(URCM).The activation energy Eand the pre-exponential factor k0 calculate by the RPM model have the same variation law,and there are significant'compensation effect'.With the amount of waste plastic added increasing,the activation energy decreases first and then increases,indicating that there is a synergistic effect in the combustion of waste plastics and semi-coke mixture.