The Role of Potassium in the Melting Behaviour of Recovery Boiler Smelt: An Experimental Study and Thermodynamic Analysis

Daniel Lindberg, Niklas Koivunen, Leena Hupa, Mikko Hupa

Research output: Contribution to journalArticleScientificpeer-review


Potassium and chlorine are the two main non-process elements that can be significantly enriched in the pulping and recovery process due to the high solubility of potassium and chloride salts in liquor. Both elements have a significant effect on the melting and flow properties of recovery boiler smelt. Therefore, a laboratory study was conducted to measure the melting behaviour of synthetic smelt mixtures rich in potassium and of smelt samples with varying potassium contents. The melting of the mixtures was measured with a simultaneous TGA/ DSC apparatus. Solidus (T-0), liquidus (T-100), and phase transitions were measured during sample heating and cooling. The experimental results were compared to results from thermodynamic modelling. The largest differences between calculated and measured solidus and liquidus temperatures occurred for K-rich mixtures. The new experimental data can be used to improve the accuracy of thermodynamic models for predicting the melting of K-rich recovery boiler smelts and deposits. This new information is important because some mills let their potassium levels rise.
Original languageUndefined/Unknown
Pages (from-to)56–64
Number of pages9
JournalJ-For: the Journal of Science and Technology for Forest Products and Processes
Issue number3
Publication statusPublished - 2018
MoE publication typeA1 Journal article-refereed

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