Thermochemical behaviour of chlorine-containing material in biosludge during analytical pyrolysis

Thermochemical behaviour of the air-dried solid matter of two different waste materials (activated sludge and a mixture of biosludge and bark) from a kraft pulp mill was investigated in the temperature range 250-650°C during analytical pyrolysis. No significant differences in the pyrolytic properties of these materials were found, the primary mass loss occurring at 350-500°C. In both cases, at 450°C, all organically bound chlorine (70-80% of the total chlorine) in the original feedstocks was released, mainly in the form of hydrogen chloride. Results indicated that pyrolysis prior to combustion of biosludge is one attractive way of releasing organically bound chlorine and reducing the possibility of forming environmentally harmful chlorinated compounds.