The upper operating temperature of tubes in heat exchangers/steam generators is strongly
influenced by the degradation that can occur because of the reaction of the
exchanger/generator tubing with the deposits that accumulate on the surface of the tubes. In
fact, severe corrosion has been observed in some biomass fired systems, particularly with
elevated potassium and chlorine concentrations in the deposits. Wood gasifiers have recently
been and are currently being constructed at several sites in North America. In these systems,
the syngas is burned to produce steam and the performance of the heat exchanger tubes under
ash deposits is of great concern. As temperatures of the heat exchangers are increased in an
effort to increase their operating efficiency, the performance of the tubes is of greater interest.
The corrosion behavior of alloy steel tubes as a function of temperature has been investigated
by exposing samples of selected alloys to ash collected from the steam generator fired by
syngas produced in wood gasifiers. This study compares corrosion rates from laboratory
exposures of synthesis gas and ash at 500°C and 600°C.
Keywords: biomass gasification, corrosion, ferritic steels, boiler tubes