VII LIEKKIPÄIVÄ, 4.4.2016, Lahti
Effect of temperature gradient on morphology and chemistry of superheater deposits
Markus Engblom*, Daniel Lindberg, Jonne Niemi, Leena Hupa
Åbo Akademi University, Piispankatu 8, 20500, Turku
*corresponding author (markus.engblom@abo.fi)
Abstact
Effect of temperature gradient on synthetic granular salts representing boiler deposits has been
studied using a laboratory method. Investigated salts are mixtures of NaCl/Na2SO4 or KCl/K2SO4.
Experiments show alkali chlorides to be transported due to gas phase diffusion down the
temperature gradient toward the steel surface. This is a new insight into intra-deposit phenomena
occurring during deposit aging. This work presents results from the experiments and discusses the
implications of the alkali chloride transport for boiler deposits. Densification of porous deposits as
well as change in the local chemical composition of the deposit may have implications for boiler
deposit removability and superheater corrosion. Comparison to boiler deposit cross sections
reported in literature shows alkali chloride transport to occur also in boiler environment when
burning straw. Future work includes sampling of boiler deposits to understand better the occurrence
and extent of alkali chloride transport in various boiler types and for different fuels.