GASIFICATION OF SEWAGE SLUDGE UNDER FLUIDIZED BED CONDITION

Abstract

Gasification of sewage sludge (SS) is a thermochemical process that converts sludge particles into syngas, providing an environmentally acceptable alternative to the usual methods of SS disposal, such as landfilling, agricultural land application, and incineration. The present study investigates the gasification of SS in a fluidized bed. Specifically, it explores the influence of several important operation parameters which is temperature, equivalence ratio (ER), and steam-to-fuel ratio (S/F) on the product syngas composition. The experiments were carried out at 650°C, 750°C, and 850°C; ER of 0.2, 0.3, and 0.4; and S/F ratios of 0.5, 1, and 1.5. In total, 36 experiments were performed. This study demonstrates a direct correlation between temperature and hydrogen and carbon monoxide production levels and an inverse correlation between temperature and carbon dioxide and methane formation rates. Aerobic activity has a positive influence on organic matter degradation, identified the value of 0.2 as the optimal ER, which yielded the highest yields of hydrogen and carbon monoxide. It further promoted water-gas shift reactions, which increased hydrogen generation as S/F increased, but the optimal S/F that led to the highest hydrogen production was above the range used in this study. The experimental data was further validated with Aspen Plus process simulation which showed similar correlation between trends of operating parameters with syngas composition, however simulation results showed higher hydrogen generation compared to experimental results.