Products Distribution During Sewage Sludge Pyrolysis in a Sand and Olivine Fluidized Bed Reactor: Comparison with Woody Waste

Abstract

The purpose of this article is to improve the understanding on sewage sludge (SS) pyrolysis behavior in a fluidized bed reactor between 700 and 890 °C. The experiments were carried out under a pure nitrogen atmosphere using sand and olivine as bed materials. The results gathered in this paper highlight the impact of temperature and bed materials on various performance criteria. It was observed that the use of olivine as a bed material affects the composition of the syngas, especially the fraction of the light hydrocarbons CH 4 and C 2 H X. It was also noticed that increasing the pyrolysis temperature yielded more syngas and reduced the condensable species and char quantities. Furthermore, an increase in temperature led to an increase in the fraction of benzene in tars. Comparing different kinds of fuels revealed that SS pyrolysis yields less syngas than pinewood and more syngas than municipal green waste. SS pyrolysis led to significantly higher CH 4 and C 2 H X yields than woody waste, as well as a higher tar quantity. It was also noticed that BTEX compounds account for 70% of the tars produced during the pyrolysis of each of the fuels that were studied at 850 °C. Findings show that the thermal decomposition of SS generates a syngas rich in H 2 (25-37 mol%), CO (23-40%), CO 2 (6-19%), CH 4 (9-21%) and C 2 H X (4-17%). The syngas lower heating value is varying between 14,000 and 22,000 kJ/Nm 3 .