Characterization of fluidized bed pyrolysis of sewage sludge by time-resolved pressure measurements

Conference Dates

June 19-24, 2016


The management of sewage sludge in an economically and environmentally acceptable manner is one of the critical issues facing society today. Due to industrialization and urbanisation, production of wastewater sludge has dramatically increased in the last years and this is expected to continue in the future. The environmental legislation is becoming more and more restrictive as regards landfilling of this biodegradable waste and the use of sewage sludge in agriculture is often hindered due to the possible presence of heavy metals and pathogens. The disposal of wastewater sewage sludge by means of thermochemical conversion appears to be a potentially useful strategy to avoid landfill disposal and, at the same time, to exploit sludge as a source of energy and valuable chemicals. Fluidization technology applied to thermochemical processes, like combustion, gasification and pyrolysis, is an attractive option, due to its favorable characteristics: inherent operational flexibility, high efficiency, low pollutant emissions, ability to effectively accomplish destruction of micro-pollutants and pathogens (Werther and Ogada, 1999). Devolatilization of sewage sludge granules during thermochemical processing in fluidized beds plays a crucial role in the design and performance of fluidized bed converters. Uneven axial and radial distribution of volatile matter in the fluidized-bed combustor/gasifier is commonly experienced in industrial units and is determined by in-bed emission of volatile matter which is responsible for the enhancement of axial fuel particle segregation. On the other hand, the competition between fuel devolatilization and radial solids mixing crucially affects the radial distribution of volatile matter across the reactor and emphasizes the relevance of the devolatilization kinetics to volatile matter segregation. Short devolatilization times promote the release of volatile matter above the bed and close to the fuel feeding points.

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