Microwave pyrolysis of sludge for potential use as land application and biofuel

Abstract

AbstractBACKGROUNDA microwave pyrolysis was conducted to treat two sludge cakes for the production of liquid oil and sludge residues. The application of pyrolysis technology, the safety of land disposal of pyrolysis residue, and the quality of the derived biofuel were evaluated.RESULTSResults indicated that the total pore volume increased with increases in the mesopore size range in the case of both sludge residues after increasing the pyrolysis temperature. Low carbon, hydrogen, and sulfur content and high nitrogen content were observed in the oil derived from the chemical industry sludge. As a result, the pyrolysis liquid chemical sludge oils had heat values of 9600 to 9700 kcal kg−1 at 673–1073 K, which was slightly lower than the 9800–10 000 kcal kg−1 found for the petrochemical sludge.CONCLUSIONAfter pyrolysis, the amount of 16 polyaromatic hydrocarbons (PAHs) in the residue and oil were significantly reduced in both the chemical sludge and petrochemical sludge at 673–1073 K. The high pyrolysis liquid oil heat values for both types of sludge indicated their potential for use as a biofuel to produce energy. The 16 PAH content in the pyrolysis residues was higher than the European standard of 6 mg kg−1, and they were thus not acceptable for soil and agricultural applications. However, as reported in the literature, using a pyrolysis temperature above 1073 K may further reduce the PAH content of the pyrolysis residue to meet regulatory standards. © 2019 Society of Chemical Industry