Heat exchanger material optimization possibilities with corrosion probe measurements

As the world moves towards zero emission solutions, the substitution of fossil fuels through alternative fuels, e.g. waste and biomass, is of great interest. One of the most serious problems such plants face is severe corrosion. Often corrosion limits the maximum achievable operation temperature and pressure, and in worst-case uncontrolled corrosion leads to the emergency shutdown of boiler. The repair actions due to corrosion failures are highly expensive. Thus different monitoring systems are used to follow and estimate the progress of corrosion phenomena in the processes. Corrosion monitoring gives valuable information from the boiler operation and its effects on the corrosion and thus provide tools for proactive boiler operation to avoid hazardous operating modes and to extend the life of tubes and pipings. Systematic monitoring provides a cost-effective way to improve reliability of critical components, reduces unscheduled breakdowns and increases overall business profitability. Probes can also be used to define the critical temperature ranges of materials for example during the planning of foreseeing changes in operational parameters. The paper describes the corrosion measurement campaigns carried out at boiler burning industrial and municipal solid waste. Two types of air-cooled probes were used in the studies: One multisample probe to compare corrosion behaviour of alternative superheater materials and one temperature gradient probe to determine the temperature regions with acceptable corrosion rates in the operation conditions.