Influence of process conditions on the rate of activation of chars derivedfrom pyrolysis of used tires

Used tires were pyrolyzed in a nitrogen-purged 3 kg static bed, batch react or. The char was subsequently activated in an equimolar mixture of either s team and nitrogen or carbon dioxide and nitrogen. Activation was a two-stag e process, with an initial more rapid gasification of carbonized rubber dep osits followed by less rapid gasification of carbon black. The activation e nergy in steam was 201 kJ mol(-1) The burnoff achieved by carbon dioxide un der otherwise identical conditions to that of steam was on average 72% of t hat found when steam was used. The reactivity of acid-demineralized char in steam was around 22% less than that of raw char. It was suggested that cal cium ions in the raw tire char catalyzed the gasification reactions. The ti re pyrolysis temperature had an unclear influence on the rate of activation of the derived chars. The influence of particle size on the rate of activa tion was also investigated, and the results are discussed in terms of ash c ontent and distribution. The outflow gas composition and gross calorific va lue of the gas were also determined in relation to activation conditions. B ET surface areas of the derived activated carbons reached a maximum of 640 m(2) g(-1).