Study on low-temperature catalytic pyrolysis of residual sludge

The low-temperature catalytic pyrolysis of sludge is a new developing technology with the dual characteristics of sludge treatment and energy recovery. It was used to treat residual sludge produced by an urban wastewater treatment plant. Pyrolysis conditions, like residence time and final pyrolysis temperature and catalyst, were varied so that their influence on the characteristics of the resulting products could be studied. With the help of thermal gravimetric analysis (TGA) for residual sludge and GC/MS analysis for derived oil, it was discussed about the reaction mechanism of pyrolysis process. Results showed that using catalyst decreased the char fraction yield and increased the oil fraction yield while that of the quality of oil also improved. Furthermore, the final pyrolysis temperature needed for maximising the fuel oil yield fell from 450 °C to 400 °C, maximum oil yields increased from 34.53% to 38.71%, and the heating value of oil was higher. The main reaction mechanism could be presumed the evaporation of aliphatic compound and the conversion of protein from 200 °C to 450 °C.