26.1.2024

Doctoral thesis on the dynamic processes of deposit ageing in power boilers
 

M.Sc. (Chem. Eng.) Roland Balint’s doctoral thesis in inorganic chemistry will be put forth for public defence at Faculty of Science and Engineering at Åbo Akademi University.

The thesis is entitled Impacts of Time and Temperature Gradient on the Morphology and Chemical Composition of Superheater Ash Deposits.

The public defence of the doctoral thesis takes place on Friday 2 February 2024 at 1PM. Professor Marcus Öhman, Luleå University of Technology, Sweden will serve as opponent and Docent Markus Engblom, Åbo Akademi Univeristy, as custos.

Summary

The results of the thesis help to better understand the dynamic processes of deposit ageing, that take place within ash deposits that form on heat transfer surfaces in power boilers. These processes are induced by the temperature difference between the hot combustion gases and the colder heat transfer surfaces. Deposit ageing causes local changes in the morphology and chemical composition of ash deposits over time after they have formed on heat transfer surfaces. This can increase the corrosiveness of an ash deposit significantly and hamper deposit removability. 

The work in this thesis focused on deposit samples from full-scale boilers, while previous studies have pinpointed the phenomena of deposit ageing in laboratory tests. Nevertheless, well-defined laboratory experiments were also carried out in this work to complement the full-scale data. 

The results of the thesis can be used to predict local changes in deposit chemistry and morphology over time and aid in identifying regions in the boiler that are at an increased risk for heavy corrosion, which may cause costly and unscheduled shutdowns. To avoid this, the information can be utilised by boiler manufacturers and operators to develop suitable countermeasures for deposit-induced operational problems, for example by selecting adequate materials for the surfaces in regions at high risk for deposit-induced corrosion already during boiler manufacturing. In addition, the results can be used to optimize the internal cleaning intervals of heat transfer surfaces during boiler operation, since deposit ageing is a time-dependent phenomenon. By keeping the surfaces clean, both the energy efficiency and the boiler runtime increase. 

Roland Balint was born in 1991, Ingolstadt, Germany. He can be reached by email roland.balint@abo.fi.

The doctoral thesis can be read online through the Doria publication archive.