Kinetic Analysis Of Waste Tire Pyrolysis

Waste tire,which has been regarded as‘black pollutant’,is a typical organic solid waste with high thermal resistance,biodegradation resistance and mechanical damage resistance.Waste tire pyrolysis is a thermal degradation of waste tire into syngas,pyrolytic oil and pyrolytic char in the absence of oxygen.The products could be transformed into high value-added products.Compared with incineration,burial and other waste tire dispose methods,pyrolysis possesses both economic and environmental benefits.Kinetic analysis of waste tire thermochemical conversion could quantitatively characterize the reaction process of waste tire pyrolysis which could provide the direct reference for the optimizing operating conditions and the design of waste tire pyrolysis reactors.However,in industrial applications,the heating rate of waste tire could reach 100°C/s or more（such as waste tire fast pyrolysis in the fluidized bed reactor）.Thus,the kinetics of waste tire pyrolysis under a low heating rate which is based on the traditional commercial thermal gravimetric analyzer could not accurately represent the real reaction process of waste tire in the industrial applications.In this study,based on the idea of wire mesh reactor,a new thermogravimetry device which could heat the sample at a fast heating rate with a wireless power supply technology and measure the sample temperature and mass without contacting was optimized to investigate the kinetics of waste tire pyrolysis under the high heating rate.Also,the slow and fast pyrolysis kinetics of waste tire were investigated by iso-conversional method and the variation of reaction mechanism was analyzed.The combination of two kinetics could provide a new idea for the design and optimization of waste tire pyrolysis reactor The main results are as follows:（1）The kinetic parameters of waste tire slow pyrolysis were determined and analyzed by the iso-conversional methods,compensation effect method and master plot method.The results showed the pyrolysis process of waste tire could be separated into three stages:drying,devolatilization of waste tire and degradation of refractory organic compounds.Under the condition of the low heating rate,during the whole pyrolysis process of waste tire,the activation energy ranged from 119.37 to 306.22 k J/mol.In general,during the initial and final stages of waste tire pyrolysis the reaction rate was dominated by diffusion model.While the degradation of main organic components such as natural rubber,butadiene styrene rubber occurred,the reaction rate was controlled by model F3.It was found from the analysis of waste tire pyrolysis products that with the increase of the pyrolysis temperature,the contents of H₂and CH₄ in pyrolysis gas increased from 37.36%,20.01%to 44.20%,25.60%,respectively.The content of aliphatic hydrocarbon compounds in the pyrolytic oil decreased by 42.30%,and the content of aromatic compounds increased by 98.10%gradually.In the pyrolytic char,the oxygen-containing functional groups decreased and the degree of unsaturation increased.（2）The kinetic parameters of waste tire flash pyrolysis were determined and analyzed by the iso-conversional method and compensation effect method.The results showed that compared with the waste tire slow pyrolysis experiment,with the greatly increase of heating rate,the degradation period was greatly reduced.Meanwhile,the residual mass fraction of waste tire also showed a trend of gradual decline.Under the condition of high heating rate,the activation energy ranged from 119.37 to 306.22 k J/mol,which was much lower than that of slow pyrolysis.For the conversion stage 0.05～0.55,the rate of pyrolysis reaction was mainly controlled by the nucleation and growth mechanism.Meanwhile,for the conversion stage0.60～0.85,the reaction mechanism was F2 model.In the solid product of flash pyrolysis,the aromatization degree of pyrolytic char was obviously reduced.However,the increase of the heating rate hardly caused any change of the surface morphology and physical structure.