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Raw meal and slag reactions during cement clinker formation
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. (Thermochemical Energy Conversion Laboratory)
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
2019 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

Natural limestones as raw material for OPC clinker manufacturing contribute to emissions of CO2gases during the production of clinker. In addition, the mining of limestone can regionally be controlledby restrictions due to environmental concerns. Slags from the steel industry can replace limestone tominimize the use of the mineral deposits. Both materials have similar chemistry and are compatible asraw materials.Utilizing slags raises questions about how slag particles will react with other raw meal components asthe temperature in the kiln increases during clinker formation. This study establishes the chemical andmineralogical aspects of replacing a portion of the limestone with slags. Of interest is how the materialsreact during the formation of the liquid phase and the formation of phases containing MgO.Three different slags were examined, a basic oxygen furnace slag BOF, a crystalline blast-furnace slagand a granulated blast-furnace slag. In the study, the microstructural causes of reactivity, as well asmineral formation in the transition zone between raw meal components, developing liquid phase andslag particles were studied. Heated raw meals were studied using HT-QXRD, QXRD, SEM andthermodynamic modeling to describe the reactions of particles at higher temperatures. The resultsshow that the formation of clinker minerals is strongly influenced by the type and amount of slag. Thus,a careful selection must be done of both composition and quantity of metallurgical slags for naturallimestone replacement in order to maintain clinker quality.

Place, publisher, year, edition, pages
2019.
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:umu:diva-162764OAI: oai:DiVA.org:umu-162764DiVA, id: diva2:1346484
Conference
15th International Congress on the Chemistry of Cement, Prague, Czech Republic, September 16–20, 2019
Available from: 2019-08-28 Created: 2019-08-28 Last updated: 2023-08-21Bibliographically approved
In thesis
1. Modeling the influence of magnesium from alternative raw materials on the chemistry of Portland cement clinker
Open this publication in new window or tab >>Modeling the influence of magnesium from alternative raw materials on the chemistry of Portland cement clinker
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Modellering av inverkan av magnesium från alternativa råmaterial på Portland cementklinker kemi
Abstract [en]

The methods used in this thesis work were a combination of computational and modeling based laboratory experiments.

Thermodynamic process modeling of the cement clinker process offers a tool for evaluating how changes in raw materials and process parameters affect the clinker quality. Work with finding suitable replacement raw materials involves investigating the chemical compatibility of potential alternative materials. Such replacement materials may be metallurgical slags, although there are some unsolved issues with the quantities of certain metals and particularly Mg in these materials.

For predicting the formation of clinker mineral phases, cooling calculations are used in order to reproduce the temperature history in the full scale process. A chemistry model including a solid solution phase based on C2S and phosphate was developed along with the recommendation for continued work on clinker phases with solid solutions to include MgO. A thermodynamic database for phase chemistry calculations of clinkering reactions was created and evaluated. Suitable compounds and solution species were selected from the thermochemical database included in FactSage software. The extent and quality of the required thermodynamic data via available databases is generally satisfactory, except for certain properties of some of the main clinker phases. One example is the lack of a thermodynamic model for the alite solid solution. That is, the composition of the phase available in the database representing alite does not contain the minor elements Al, Fe and Mg. Therefore, it is difficult to predict the quantity and distribution of Mg in the clinker, with varying total content of MgO. Thus, one of the goals/objectives was to improve thethermodynamic model of alite as a solid solution of 3CaO-SiO2-xAl2O3-yFe2O3-zMgO. To achieve this, it was assumed that a mix of compounds with adjusted Henrian coefficients representing the solid solution clinker phase alite was in equilibrium with the clinker melt.

The distribution of MgO was studied in synthetic clinker compositions with quantities ranging from 0.5 to 10 wt-%. Synthetic clinker mixes were heated to 1450°C and studied with Rietveld refinements of X-ray diffraction data and SEM-EDS analysis. In addition, the mechanisms of how slag and lime particles react facilitating the diffusion of MgO into the developing clinker melt and the formation of incipient belite were studied.

The calculated results provide a good prediction of the quantities and composition of the clinker phases formed during heating and non-equilibrium cooling. The solubility of MgO in the clinker and the quantity of periclase formed is in fair agreement with published data. Thus, this thesis work shows that using a mix of compounds with adjusted activities in alite together with available standard thermodynamic data and the Scheil cooling method had good potential for evaluating alternative raw materials.

Also, the work has identified weak points in the process modeling and suggest improvements to be made in future research work.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2023. p. 94
Keywords
Thermodynamic modeling, process modeling, Portland cement, clinker, periclase, magnesium oxide, alite, Scheil calculation, solid solutions
National Category
Physical Chemistry Chemical Process Engineering
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-213098 (URN)9789180700863 (ISBN)9789180700856 (ISBN)
Public defence
2023-09-14, Aula Biologica, Biologihuset, Umeå, 13:00 (Swedish)
Opponent
Supervisors
Funder
Vinnova, 2014-04073Vinnova, 2015-02519Vinnova, 2015-04541Swedish Energy Agency
Available from: 2023-08-24 Created: 2023-08-21 Last updated: 2023-08-22Bibliographically approved

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Viggh, ErikBoström, DanWilhelmsson, Bodil

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