Since communities and companies are deciding to dispose sludges of different origin in a safe and nonpolluting way, more and more sludge is burnt either in mono-combustion or co-combustion units. Lurgi Energie und Entsorgung GmbH, one of the most experienced fluidized bed designer, is commissioning two bubbling bed incinerators of totally different incinerator size in 2002. In France the smallest fluidized bed incinerator ever built by Lurgi with a cross-sectional bed area of 4 m2 is designed to burn 750 kg (d.m.)/h sewage sludge. In spite of the small size it consists of all equipment necessary for sewage sludge incineration, including a disc dryer, a thermal oil boiler for heat recovery and a complete state of the art flue gas cleaning system. Air pollutants are removed in a circulating fluidized bed adsorber (CFB) designed in accordance with the new Lurgi CIRCOCLEAN® process. In United Kingdom the largest bubbling bed incinerator ever built by Lurgi with a cross-sectional bed area of 32 m2 is going to start its operation in 2002. The plant burns a mixture of thickened and mechanically dewatered primary and secondary sludge and different plastic residues from waste paper recycling plants. In order to provide sufficient disposal capacity of the waste material generated at the Kemsley Paper Mill site some parts of the installation consist of parallel streams or units (e. g. waste material handling and storage). The overall design throughput rate of mixed waste material is 22.8 t(a.r.)/h, corresponding to a thermal load of 29.1 MW. Due to the specific properties of the paper sludge, the formed ash can be used as an adsorbent/reactive compound for the capture of acidic pollutants. The flue gas cleaning system consists of a zeolite dosing unit to remove dioxins/furanes upstream of a baghouse filter. The paper presents the main design parameters of both disposal facilities and peculiarities of the burnt materials in comparison to other sludges. Since the plants are still in the commissioning phase only problems that might occur during the operation of the plant and tendencies in the operation behavior are described.
Corrosion in the Flue Gas Cleaning System of a Biomass-Fired Power Plant
