Co-Incineration of Sludge in a Circulating Fluidized Bed

Operating results show that the co-incineration of sludge with higher calorific fuels, such as coal, biomass or residue derived fuel (RDF) in circulating fluidized bed (CFB) boilers has good operating characteristic and is in general a practical method for thermal sludge disposal. This study focuses on three circulating fluidized bed boiler plants in Germany that co-incinerate various fiber processing sludge, inherently composed of poorly biodegradable cellulose and lignin, and their related operational experience. The operating datashow varying impacts on the plant performance, mechanical load and emission values depending on the sludge composition and co-incineration share. In particular fiber sludge with high ash and limestone contents affect heating surface cleaning cycles and Nitrogen oxide (NOx) emissions.

In the past few years, the European legal framework, such as the Integrated Pollution Prevention and Control Directive (2008/1/EC) and Waste Framework Directive (2008/98/EC) has led to a broad discussion on sustainable solutions for the disposal of sludge.

In the past, sludge landfill was a preferred disposal method; however, in many cases landfill is no longer a practical solution because of the decrease in space available for landfills, the rising disposal fees and the growing concern about the impact of landfilling on the environment, considering potential contaminations with heavy metals and persistent organic pollutants.

Thermal utilization of sludge is an attractive and sustainable disposal method for environmental and economic reasons. Thermal treatment reduces and minimizes the solid mass and volume to be disposed and maximizes the reduction of pollutants and toxins contained in the sludge, leading to lower disposal cost and energy recovery.

The main drivers for the growing number of thermal sludge treatment solutions are the increasing number of land disposal regulations and restrictions, the political drive for waste to energy practices, the demand for final solutions without soil pollution risks, the decreasing cost difference to land disposal and the development of renewable energy sources.

Sludge can be incinerated in mono-incineration plants, i.e. mainly bubbling fluidized bed furnaces, or co-incinerated with other high calorific fuels, e.g. in cement kilns or circulating fluidized bed furnaces.

Copyright: © TK Verlag - Fachverlag für Kreislaufwirtschaft
Quelle: Waste Management, Volume 3 (Oktober 2012)
Seiten: 9
Preis inkl. MwSt.: € 0,00
Autor: Dipl.-Ing. Johannes Sbaschnigg
Dipl.-Ing. Helmut Anderl
Dr. Sebastian Kaiser
Dipl.-Ing. Matthias Zöhrer

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