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FP5

CORBI Résumé de rapport

Project ID: ENK5-CT-2001-00532
Financé au titre de: FP5-EESD
Pays: Finland

Corrosion data on superheater alloys for waste and biomass boilers: Specific effects of H2O and deposits

Several boiler tube materials including 2.25Cr-1Mo, X10,X20, AC 66, Alloy 625, Esshete 1250, TP347h and San 28 were tested for 360 hours under various corrosive atmospheres (N2-O2-HCl-H2O-CO2)at 500 - 600°C with and without filter and cyclone ashes.

Thereby, specific mass gains of samples, chemical changes of ashes and the corrosion products were investigated resp. determined. High temperature exposure tests showed that the mass gains for the samples covered with cyclone ashes were higher than for those covered with filter ashes and for uncovered samples. In the case of HCl addition, mass gains were increased by increasing the water content and mass gains with covering of cyclone ash were higher than those with filter ash. Nickel-based alloys exhibit most corrosion resistance.

Moreover, the formation of gaseous chlorine by the reaction of alkali-chlorides with metal oxides was thermodynamically calculated by the FactSage-program and further calculations were to conduct in System (Alkalis- HCl- H2O- O2- CO2).

Local reactions of KCl particles with bare metal surfaces and oxide scales were studied after deposition of KCl particles by thermophoretic migration. It was found that adhesion of particles on the bare metal surface is much better than on a preoxidized material. Furthermore local reaction (melt formation) between the metallic surface of pure iron and the KCl particles could be observed after short time reaction of a covered sample at 300°C.

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Markku ORJALA
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