When the carbon is removed from the system it takes the impurity with it. Typical adsorbates are acetone, trichloroethane, and compounds of mercury. All are toxic in some degree, and any or all may be found in flue gases from power plants. Because old tires are in enormous supply, they have been the object of study for some time by chemical and environmental engineers. This gives us some idea of the potential contribution to commerce and to environmental cleanup.
Some minor components are also present.
The oil and gas are used to supply process heat, and the carbon is then activated. Activation consists of heating the carbon for two to three hours at a temperature between 800 and 900 degrees C. in a stream of steam and nitrogen. Though the two steps of pyrolysis and activation are technically separate and distinct, in practice they may be carried out in the same reactor, first pyrolysis. The experiments were done in two phases. The first was a set of bench-scale trials, using tire material from several sources.