A Fundamental Study on the Change in Composition of Fireside Deposits with Time in Kraft Recovery Boilers

Jonne Niemi, Daniel Lindberg, Markus Engblom, Honghi Tran

Research output: Contribution to journalArticleScientificpeer-review


Accumulation of fireside deposits on heat transfer tube surfaces is a persistent problem in Kraft recovery boiler operation. In a given boiler, the deposit composition varies with location. Even at a given location, the composition varies across the deposit layer. This study systematically investigates what makes deposit compositions heterogeneous. An entrained flow reactor with an air-cooled probe was used to collect and age synthetic deposits. Results confirm NaCl and KCl migration towards colder temperatures due to evaporation and condensation. In addition, liquid phase movement towards colder temperatures was confirmed. High-alkali chloride melt penetrates the deposit and precipitates at colder temperatures, leading to enrichment of corrosive alkali chloride species close to the steel. The results imply that liquid phase movement within recovery boiler deposits can accelerate corrosion.

Original languageUndefined/Unknown
Pages (from-to)45–52
JournalJ-For: the Journal of Science and Technology for Forest Products and Processes
Issue number2
Publication statusPublished - 2018
MoE publication typeA1 Journal article-refereed


  • alkali salt deposits
  • boiler deposits
  • kraft recovery boilers

Cite this