Kaj Thomsen

Kaj Thomsen

Associate Professor

Søltofts Plads

Building: 229, 204

2800 Kgs. Lyngby


Phone: 45252860

Fax: 4588 2258

Research in phase equilibria for solutions containing salts or sour gases. Development and application of thermodynamic models for solutions that contain salts (Extended UNIQUAC).

Research in phase equilibria for solutions that contain ions is essential in relation to the absorption of carbon dioxide from the flue gas from power plants. By absorption of carbon dioxide carbonate, hydrogen carbonate, carbamate, and additional ions are formed depending on the solvent. The simulation of this absorption requires a thermodynamic model for salt solutions (electrolyte solutions). Phase equilibria in solutions consisting of carbon dioxide, ammonia, and water can be accurately described by the Extended UNIQUAC electrolyte model.

This research can also be used for predicting the water activity in multi component solutions of food preservatives. The thermodynamic model is able to predict the water activity in a mixture based on parameters determined from binary systems. This can be used for improving the quality of food and minimizing the amount of preservatives in food as the water activity is determining for the growth potential of micro organisms.

In the oil industry and during the production of geothermal energy, salts may precipitate and form scale inside tubes and valves. This happens when solutions of salts that have an increased solubility at high temperature and pressure are cooled and depressurized. Relevant salts are gypsum, barium sulfate, strontium sulfate, calcium carbonate, magnesium carbonate, and more. By using the Extended UNIQUAC model, the risc of precipitation can be calculated.

Salt influences the vapor-liquid equilibrium of alcohols and other organic solvents in water. In some cases, a liquid-liquid split takes place by adding salts to mixtures of water and organic solvents. In some cases this phenomenon can be used for separating water from organic solvents instead of performing a distillation.

By combustion of biomass to produce electricity and district heating, a fly ash consisting of soluble salts is produced. Some of the soluble salts could be used as fertilizer if they were not mixed with heavy metal salts. Because of the content of heavy metals, the fly ash can not be deposited in landfills. The heavy metal salts therefore have to be separated from the remaining part of the fly ash. By modeling the system consisting of an aqueous solution of the components of the fly ash, a process for separating the fly ash into its pure components can be developed.



1994 - 1997 Ph.D. in Chemical Engineering - Technical University of Denmark
1989 - 1994 M.Sc. in Chemical Engineering - Technical University of Denmark

Academic grades


Professional experience

2002 - Associate Professor (KT-DTU) - Technical University of Denmark, Department of Chemical Engineering
1999 - 2002 Assistant professor (KT-DTU) - Technical University of Denmark, Department of Chemical Engineering
1997 - 1999 Assistant research professor (KT-DTU) - Technical University of Denmark, Department of Chemical Engineering


Danish (speaking, reading, and writing), English (speaking, reading, and writing), German (reading), French (reading)


Thermodynamics of solutions with salts. Modeling of the thermodynamic properties of solutions with salts including modeling of solid-liquid, vapor-liquid and liquid-liquid equlibrium. Post combustion CO2 capture.

International experience

2006, August to December: Visiting Professor at Department of Chemical and Biological Engineering, University of Wisconsin-Madison, USA

2008, April, Gave workshop on Aqueous solution thermodynamics at University of Cape Town, Cape Town, South Africa

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  • Energy Procedia

    ISSNs: 1876-6102

    Elsevier BV, Netherlands

    BFI (2017): BFI-level 1, Scopus rating (2015): SJR 0.378 SNIP 0.481, ISI indexed (2013): ISI indexed no

    Central database


  • Fluid Phase Equilibria

    ISSNs: 0378-3812

    Elsevier BV, Netherlands

    BFI (2017): BFI-level 2, Scopus rating (2015): SJR 0.89 SNIP 0.955, ISI indexed (2013): ISI indexed yes

    Central database


  • Industrial & Engineering Chemistry Research

    ISSNs: 0888-5885

    Additional searchable ISSN (Electronic): 1520-5045

    American Chemical Society, United States

    BFI (2017): BFI-level 2, Scopus rating (2015): SJR 0.976 SNIP 1.116, ISI indexed (2013): ISI indexed yes

    Central database


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