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Modeling the influence of magnesium from alternative raw materials on the chemistry of Portland cement clinker
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
2023 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Modellering av inverkan av magnesium från alternativa råmaterial på Portland cementklinker kemi (Swedish)
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 [en]
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: urn:nbn:se:umu:diva-213098ISBN: 9789180700863 (electronic)ISBN: 9789180700856 (print)OAI: oai:DiVA.org:umu-213098DiVA, id: diva2:1789922
Public defence
2023-09-14, Aula Biologica, Biologihuset, Umeå, 13:00 (Swedish)
Opponent
Supervisors
Funder
Vinnova, 2014-04073Vinnova, 2015-02519Vinnova, 2015-04541Swedish Energy AgencyAvailable from: 2023-08-24 Created: 2023-08-21 Last updated: 2023-08-22Bibliographically approved
List of papers
1. A predictive chemistry model for the cement process
Open this publication in new window or tab >>A predictive chemistry model for the cement process
2008 (English)In: Zement, Kalk, Gips International: ZKG international, ISSN 0949-0205, Vol. 61, no 7, p. 60-70Article in journal (Other academic) Published
Abstract [en]

A tool has been developed that enables prediction of the chemistry in cement production with thermodynamic phase equilibrium calculations. Reactions in gas, solid and liquid phases are calculated in the process from preheating tower, including exhaust gas cleaning, through rotary kiln, clinker cooler and ends at the output of clinker. The simulated values are compared to measured or calculated data from a full scale plant. This is a cement plant producing 2000 t clinker per day using both traditional and alternative fuels. The chemistry model shows good agreement especially on material chemistry at various places in the process and on composition of the clinker. A new way to define fuels is used and is straightforward and reliable. In the future work the model has to be improved and more elements are to be added to the thermodynamic database.

Place, publisher, year, edition, pages
Gutersloh, Germany: Bauverlag BV, 2008
Keywords
Kiln, process model, cement clinker
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:umu:diva-85998 (URN)
Funder
Swedish Energy Agency
Available from: 2014-02-14 Created: 2014-02-14 Last updated: 2023-08-22Bibliographically approved
2. Simulation of oxy-fuel combustion in cement clinker manufacturing
Open this publication in new window or tab >>Simulation of oxy-fuel combustion in cement clinker manufacturing
2015 (English)In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 27, no 1, p. 42-49Article in journal (Refereed) Published
Abstract [en]

A thermodynamic process model is used as an evaluation tool. Full oxy-fuel combustion is evaluated for circulation of 20–80% of flue gases to the burn zone of a rotary kiln. The full oxy-fuel combustion simulations exhibit altered temperature profiles for the process. With 60% recirculation of flue gases, the temperature in the burn zone is comparable to the reference temperature, and carbon dioxide concentration in the flue gases increases from 33 to 76%. If water is excluded, carbon dioxide concentration is 90%. The partial oxy-fuel combustion method is evaluated for 20 and 40% recirculation of flue gases from one cyclone string to both calciners. Fuel and oxygen feed to the burning zone and calciners are optimised for the partial oxy-fuel scenario. The lowest specific energy consumption is desired while maximising the amount of carbon dioxide theoretically possible to capture. By introducing partial oxy-fuel combustion with 20% recirculation of flue gases in the carbon dioxide string, total carbon dioxide emissions increases by 4%, with 84% possible to capture. Within the limits of the model, the introduction of full oxy-fuel and partial oxyfuel combustion is possible while maintaining product quality. When simulating partial oxy-fuel combustion, the energy consumption will increase even when no power consumption for the production of oxygen is included.

Place, publisher, year, edition, pages
Thomas Telford: ICE Publishing, 2015
Keywords
cement clinker production, process modell, oxy-fuel combustion
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:umu:diva-86361 (URN)10.1680/adcr.13.00068 (DOI)000351286400006 ()2-s2.0-84937509423 (Scopus ID)
Available from: 2014-02-24 Created: 2014-02-24 Last updated: 2023-08-21Bibliographically approved
3. On the phase chemistry of Portland cement clinker
Open this publication in new window or tab >>On the phase chemistry of Portland cement clinker
2015 (English)In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 27, no 1, p. 50-60Article in journal (Refereed) Published
Abstract [en]

This paper describes the formation of a phosphorous belite solid solution and its impact on alite formation. A sub-solidus phase relation for the ternary system silicon dioxide–calcium oxide–phosphorus pentoxide (SiO2–CaO–P2O5) is reported. The ternary system is based on Rietveld refinements of X-ray diffraction patterns from experimental tests. The overall picture is based on known phase diagrams, relevant Rietveld refinements models, stoichiometric relationships as a function of increasing phosphorus pentoxide concentration and vacancy theories for solid solutions of phosphate belites. A tool is developed for predicting the chemistry of the product as well as the chemistry during heating when producing Portland cement clinker. A thermodynamic database for phase chemistry calculations of clinkering reactions has been created and evaluated. Suitable compounds and solution species have been selected from the thermochemical database included in FactSage software. Some solution compositions have been uniquely designed to allow for the proper prediction of the cement clinker chemistry. The calculated results from the developed database for heating raw materials in cement clinker production and cooling of the product are presented in this paper. The calculated results provide a good prediction of the phases and quantities formed during heating and non-equilibrium cooling. The prediction of the amounts of alite, belite and aluminoferrite phases in the product according to the Scheil method is good. The temperature interval for the existence of all of the major phases is relevant. The thermodynamic data for a solution phase of alite with substituting ions of primarily magnesium oxide and phosphorus pentoxide would improve the predictability of the developed database.

Place, publisher, year, edition, pages
Thomas Telford, 2015
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:umu:diva-89699 (URN)10.1680/adcr.13.00071 (DOI)000351286400007 ()2-s2.0-84937510640 (Scopus ID)
Available from: 2014-06-10 Created: 2014-06-10 Last updated: 2023-08-22Bibliographically approved
4. Raw meal and slag reactions during cement clinker formation
Open this publication in new window or tab >>Raw meal and slag reactions during cement clinker formation
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.

National Category
Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-162764 (URN)
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
5. Early formation of belite in cement clinker raw materials with slag
Open this publication in new window or tab >>Early formation of belite in cement clinker raw materials with slag
2021 (English)In: Advances in Cement Research, ISSN 0951-7197, E-ISSN 1751-7605, Vol. 33, no 6, p. 249-256Article in journal (Refereed) Published
Abstract [en]

Analytical methods for characterising cement raw meal during heating in different atmospheres were investigated. The effect of replacing limestone with 10 wt% slag on the formation of incipient belite and precursors of the clinker liquid in the temperature range 600–1050°C was quantified using thermogravimetry, X-ray diffraction and equilibrium calculations. The results showed that when calculating the lime saturation factor, slags were favoured to sand, resulting in lower amounts of quartz and C2S in the samples containing slag than the reference sample. This suggests that silicon dioxide in slag minerals did not react in this temperature range. The multi-component equilibrium results supported the phase formation sequence established. Allowing for the possible kinetic influences the potential solids solutions offered with the software was a valuable asset. The results showed that the effect of using slags to reduce the carbonate and sand content in a raw meal on potential amounts of incipient C2S was negative. At present, more detailed knowledge is needed regarding how blast-furnace slag and basic oxygen furnace slag contribute to the formation of intermediary compounds such as incipient C2S, C3A, C2F and C4AF in the solid phase at temperatures over 1050°C and affect the formation of C3S.

Place, publisher, year, edition, pages
ICE Publishing, 2021
National Category
Ceramics
Identifiers
urn:nbn:se:umu:diva-185292 (URN)10.1680/jadcr.19.00150 (DOI)000662866700002 ()2-s2.0-85108236894 (Scopus ID)
Available from: 2021-06-28 Created: 2021-06-28 Last updated: 2023-08-21Bibliographically approved
6. Comparison of FToxid and Gtox thermodynamic databases used for simulating clinker minerals
Open this publication in new window or tab >>Comparison of FToxid and Gtox thermodynamic databases used for simulating clinker minerals
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Process Engineering Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:umu:diva-213111 (URN)
Available from: 2023-08-22 Created: 2023-08-22 Last updated: 2023-08-22

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