FLUIDIZED BED COMBUSTION: SEWAGE SLUDGE CHARACTERIZATION

RODRIGUEZ R., PALACIOS C., ECHEGARAY M., HEKTOR K., UDAQUIOLA S.

Río de Janeiro

Congreso; 2nd Mercosur Congress on Chemical Engineering-4th Mercosur Congress on Process Systems Engineering; 2005

Univerisdad Federal de Río de Janeiro-Instituto militar de Ing.-PLAPIQUI-Universidad Nacional de Litoral

The design of fluidized bed incinerators for sewage sludge requires knowledge about the sludge characteristics in order to improve process efficiency and reduce contamination. The percentages of ashes and organic compounds as well as humidity have to be determined. A high percentage of humidity results in an increased auxiliary fuel consumption. Sewage sludge may contain high concentration of heavy metals. Most of these can be found in the ashes and tails of the burning process. Heavy metals fractions are a potential risk to human health. Trace metal compounds enriched in fine particles are emitted in the sub-micron scale, mostly containing Hg, Pb and Cd. Since Hg can be dragged with the gas flow, it has to be removed, for example by using an adsorption with active coal. In this work, the analysis of the dry sewage sludge and the ashes focussing on Hg, As, Pb, Cd and Cr concentrations were done. The results suggest that sewage sludge must be treated as an hazardous waste and therefore demands special care in its final deposition. This aspect has to be considered in the design of the combustion process. Other important parameters, such as particle size distribution, density, superficial area, porous volume and porous diameter of the dry sludge were determined. These values among fluidizing velocity, thermophysical properties and chamber design are of significance to the heat transfer coefficient in fluidized bed combustion.