Thermal pyrolysis characteristics of polymer flocculated waste activated sludge

Polyelectrolyte conditioning is a common practice in wastewater management. This paper experimentally elucidated the thermal pyrolysis characteristics of waste activated sludge at a temperature range of 300-900 K (27-627 degrees C) using thermogravimetric analysis (TGA) in inert atmosphere, with especial attention on the effect of polyelectrolyte flocculation (using cationic polyacrylamide). On the pyrolysis rate vs temperature plot two maxima were noted. At the heating rate of 8 degrees C/min, polyelectrolyte does not influence the pyrolysis process. As higher heating rates (14 and 20 degrees C/min), on the other hand, flocculation to charge neutralization point would enhance the rate of thermal pyrolysis. A simple two parallel-reaction kinetic model is applied to interpret the experimental data. Possible roles of flocculant on sludge pyrolysis are discussed on the basis of change in sludge structures and the hindrance of surface reactions of sludge particles.