Article pubs.acs.org/EF
Predictive Kinetics Model for an Industrial Waste Tire Pyrolysis Process Jean-Remi Lanteigne,† Jean-Philippe Laviolette,† Gilles Tremblay,‡ and Jamal Chaouki*,† Chemical Engineering Department, École Polytechnique de Montréal, C.P. 6079, Succursale Centre-Ville, Montréal, Québec H3C 3A7, Canada ‡ Ecolomondo Corporation, 3435 Pitfield Boulevard, St. Laurent, Québec H4S 1H7, Canada †
ABSTRACT: A new pyrolysis model was developed to predict the individual product (noncondensable volatiles, condensable volatiles, and char) yield for Ecolomondo’s industrial waste tire pyrolysis process. This novel predictive kinetics-based model couples product selectivity data obtained from thermogravimetric analysis experiments to a global single-step decomposition reaction term to reproduce the nonlinear relationship between product selectivity and temperature. A transient energy balance based on a lumped capacitance method was also used to calculate the tire shred temperature using the rotary drum wall temperature as an input. The kinetics model was compared to experimental oil production data from the industrial process as well as existing models in the literature. It is shown that the model can successfully predict the oil production of the industrial process and the model accuracy is greater for smooth operating conditions. On the other hand, other pyrolysis models from the literature failed to accurately predict the oil production.
1. INTRODUCTION Waste tire management is a major issue, and despite an intensification of recovery efforts, a significant part of waste tires is not yet used. In the United States, the Rubber Manufacturers Association (RMA)1 estimated that approximately 15% of the 5 million tons of generated waste tires in 2009 remain unmanaged. Moreover, 12.6% of the managed tires are landfilled, and 40.3% are burned as a tire-derived fuel. Recent life-cycle analysis has demonstrated that landfilling has the worst environmental impact for waste tire management.2 On the other hand, the environmental impacts of thermochemical treatments, such as pyrolysis and gasification, were shown to be significantly lower than incineration, which is currently the most widely used thermal process.1,3 The development of reliable industrial pyrolysis and gasification technologies could open new possibilities for the sustainable management and commercial recovery of waste tires. On a smaller scale, pyrolysis may be techno-economically more interesting compared to gasification because a need of less process equipment and a lower operating temperature results in significantly lower initial capital investments.4 In addition, the pyrolysis oil produced from conventional waste tires typically contains high fractions of diesel-like fuel,5 which makes it attractive for commercial energy applications. It is estimated that as much as 67.9% of the annually generated waste tires could be reoriented toward pyrolysis processes.1 Pyrolysis is an anaerobic thermal decomposition process. Waste tire pyrolysis yields three products: (1) a carbon-based powder (solid) named char, (2) an oily liquid rich in hydrocarbons, and (3) a noncondensable gas composed of hydrogen and light hydrocarbons. The respective yield of the three pyrolysis products as well as their chemical composition will depend upon the pyrolysis conditions: (1) temperature, (2) residence time, (3) particle size, and (4) pressure. Several pyrolysis processes that promote specific reaction conditions © 2013 American Chemical Society
have therefore been proposed and developed. These pyrolysis processes have been categorized into three main types based on the pyrolysis conditions: (1) conventional (slow) pyrolysis, (2) fast (or ultrafast) pyrolysis, and (3) vacuum pyrolysis. Table 1 summarizes the characteristic operating conditions of the three types of pyrolysis. Table 1. Types of Pyrolysis with Their Approximate Operating Parameters parameter type of pyrolysis
temperature (°C)
residence time (s)
particle size (mm)
pressure (kPa)
conventional (slow) fast or ultrafast vacuum
300−450
300−3600
5−50
100−500
450−750 450−750
0.5−10 10−300
