CORROSION AND MATERIALS PERFORMANCE IN BIOMASS FIRED AND CO-FIREDPOWER PLANTS

摘要

In Denmark, biomass such as straw or woodchip is utilized increasingly as a fuel for generatingrnenergy. When straw is combusted, potassium chloride and potassium sulfate are present in ash products,rnwhich condense on superheater components. This gives rise to specific chlorine corrosion problems notrnpreviously encountered in coal-fired power plants. The type of corrosion attack can be directly ascribedrnto the composition of the deposit and the metal surface temperature. In woodchip boilers, a similarrncorrosion rate and corrosion mechanism has on some occasions been observed. Co-firing of straw (10rnand 20% energy basis) with coal has shown corrosion rates lower than those in straw-fired plants. Withrnboth 10 and 20% straw, no chlorine corrosion was seen. This paper will describe the results from in siturninvestigations undertaken in Denmark on high temperature corrosion in biomass fired plants. Resultsrnfrom 100% straw-firing, woodchip and co-firing of straw with coal will be reported. The corrosionrnmechanisms observed are summarized and the corrosion rates for 18-8 type stainless steels are compared.