Superheater tube corrosion in recovery boilers

Deposit formation and corrosion of recovery boiler superheater tubes are known to be interrelated with boiler chemistry and the design, as well as the operation conditions in an extremely complex way. After a short review of typical superheater corrosion conditions in the past, a brief summary is given about the work on particulate formation and agglomeration in the flue gas path. Deposit formation mechanisms, deposition fluxes, transformation processes, deposit heat conductivity and heat transfer, as well as transport of deleterious species in the deposits is illuminated by model calculations. Corrosion processes and materials performance is discussed with reference to the results of materials exposures in industrial recovery boilers, and in laboratory corrosion tests. As a conclusion, current needs and likely future trends in the materials technology of superheaters of modern recovery boilers typically operating firing high solids liquors and with low sulphur emissions are summarised