KINETICS OF CARBON-DIOXIDE ACTIVATION OF CHARS DERIVED FROM WASTE TIRES

摘要

Carbon injection is a promising mercury-control method for coal-powered plants, and the use of low-cost activated carbons derived from waste tires is considered for this application. In this study, the kinetics of CO_2 activation of the tire-pyrolysis char were determined. TGA experiments were run at different temperatures, and gasification reactivities were used to prepare Arrhenius plots. The apparent activation energy in the temperature range 900-965 ℃ was found to be relatively independent of burn-off (E = 220 ± 4 kJ/mol). In contrast, the activation energy at the low temperature range (900-917 ℃) increased with burn-off from 252 kJ/mol at 5% burn-off to about 340 kJ/mol at burn-offs above 50%. This may be a result of most reactive active sites being consumed at early stages of activation and more oxidation-resistant sites being responsible for burn-off at more advanced stages. The burn-off dependence at higher temperatures (917-965 ℃) was opposite, with the activation energy dropping from 211 kJ/mol at 5% burn-off to 175-185 kJ/mol at burn-offs above 60%.