Abstract

The feasibility of co-combustion of tannery sludge and coal as well as mono-combustion of the sludge was analyzed by tracking the migration of Cr in the sludge and its bottom ash. Most of the Cr was found to be fixed in the bottom ash during combustion when the temperature was not over 600°C. For further analysis of the migration behaviour of Cr after combustion, speciation of Cr in bottom ash was determined by BCR (Community Bureau of Reference) method. It was found that a great deal of Cr was converted from oxidizable fraction in sludge to exchangeable fraction in bottom ash. Moreover, acid leaching test indicated Cr stabilized in the original sludge became easier to leach from the bottom ash. These facts suggest the environmental risk of Cr in the ash is much higher than in the original sludge. Therefore, co-combustion of sludge and coal without any further treatment is not a feasible way to dispose of Cr enriched tannery sludge.