The characteristics of pyrolysis of waste tire with partial oxidation have been investigated in a fluidized bed reactor (0.076m i.d. × 1.2m high). To obtain basic data for the pyrolysis experiment, the mixing index of waste-tire chips/sand mixture has been determined in a cold-model fluidized bed and the combustion kinetics of waste tire char has been determined in a thermobalance reactor.
In the fluidized bed, the waste tire chips act as flotsam and are well mixed with sand at fluidizing velocity higher than 2.5 $U_{mf}$, where the value of mixing index is greater than 0.8.
In the combustion experiment in a thermobalance reactor, the devolatilization of the waste tire chip has been completed within 1-2 min with the weight loss of about 65% and slow burning of the residue char is followed. The combustion rate of waste tire char is found to be first order with respect to oxygen concentration and the activation energy of the reaction is found to be 32.2 kcal/mol. The combustion reaction of waste tire char is well represented by the shrinking core model.
The effects of feed rate of waste tires (0.21-0.52 kg/h), oxygen concentration (0-11%), pyrolysis temperature (700-880℃) and fluidizing velocity (1.5-3 $u_{mf}$) on the product yield (gas, char and oil), composition, energy recovery and heating value of the product gas have been determined in a fluidized bed reactor. The effect of feeding rate of waste tires on the product yield, composition and heating value of the product gas, and energy recovery is found to be insignificant. The effect of oxygen concentration on the yield and production rate of pyrolysis gas is found to be insignificant in the range of 0-6.5 % oxygen concentration but largely decreased at above 6.5 %. With increasing pyrolysis temperature, gas yield increases from 30 to 40% and oil yield decreases, whereas char yield remains constant. Energy recovery linearly increases with increasing pyrolysis temperature. The heating value of product gas increases linearly but total gas production rate decreases, therefore energy recovery remains almost constant with increasing fluidizing velocity.
