Effect of high heating rates on products distribution and sulfur transformation during the pyrolysis of waste tires

Fast pyrolysis offers a promising efficient way for the resourceful disposal of waste tires and heating rate was a key influence factor on products properties. However, the heating rates of the widely used experimental apparatus (like thermogravimetric) were generally outside the scope of most fast pyrolysis devices. To better guide actual pyrolysis process, the present study focused on the effects of high heating rates (ranged from 60 to 6000 °C/min) on products distribution and sulfur transformation during waste tires pyrolysis. And experiments were conducted at temperatures from 425 °C to 575 °C by using a self-designed photothermal reactor. The results showed that increasing heating rates posed slight effect on the products yields at 425 °C while obviously decreased char yield by forming more gases at higher temperatures. Moreover, high heating rates promoted the fast cracking of tires to form more radical fragments, leading to the formation of numerous small-molecule H2, CH4 and H2S. Meanwhile, secondary reactions among nascent volatiles remarkably increased the fraction or aromatic compounds in the pyrolytic tar especially at 500 °C and 575 °C. Although high heating rates hardly changed the carbon distribution characteristics in the char, increasing heating rate from 60 to 600 °C/min significantly reduced sulfur content in the char, regardless of the final pyrolysis temperature. These findings were believed to well support the application of fast pyrolysis technique for the disposal of waste tires.