Synergistic effect of co-pyrolysis of tea seed shells and scrap tyres and product evaluation

The co-pyrolysis behaviors of tea seed shell (TSS) and scrap tyre (ST) were studied systematically to discuss the potential synergistic effect. The thermogravimetric characteristics of TSS, ST, and their blends were investigated under various heating rates. The results obtained showed that a significant synergetic effect existed during the co-pyrolysis of the blends, in which the experimental mass loss curves were significantly lower than the calculated curves. Increasing the heating rate of blends led to the increase of reaction temperature due to heat transfer hysteresis. According to the TG data, the kinetics parameters of the co-pyrolysis process were calculated by Coats-Redfern method. The activation energies of the pyrolysis of TSS and ST were from 68 to 81 kJ.mol(-1) and 59 to 63 kJ.mol(-1), respectively. The activation energies range of the blends were 44-54 kJ.mol(-1) using the first-order reaction kinetics model, and 56-64 kJ.mol(-1) using the 1.5-order reaction kinetics model, respectively. The co-pyrolysis of the blends required lower activation energy than that of TSS and ST alone, and the energy required for co-pyrolysis reaction decreased with the increase of TSS ratio. Based on the results of DTG, the co-pyrolysis characteristics of TSS and ST in a fixed-bed reactor were further discussed, and the effects of operation parameters, (e.g., mass ratio of TSS to ST, pyrolysis temperature, and residence time), on product distribution and composition were investigated in detail. The results obtained showed that the experimental yields of liquid and solid were higher than that of the theoretical values, corresponding to a lower experimental gas yield, further confirming the existence of synergistic effect during the co-pyrolysis process. By analyzing the composition of liquid derived from co-pyrolysis of the blend within 40 wt.% TSS, it was found that there was a significant difference between the experimental and theoretical values, and the products containing oxygen and nitrogen were significantly reduced.