| 1. |
- Adolfsson, Daniel, et al.
(författare)
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Hydraulic properties of sulphoaluminate belite cement based on steelmaking slags
- 2007
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Ingår i: Advances in Cement Research. - : Thomas Telford Ltd.. - 0951-7197 .- 1751-7605. ; 19:3, s. 133-138
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Tidskriftsartikel (refereegranskat)abstract
- Based on modified Bogue calculations, steelmaking slags were combined in order to produce a belite-rich clinker activated with sulphoaluminate. The experiments were conducted on two different mixtures based on steelmaking slags together with additives, namely MixA and MixB. The objective of the present study was to investigate the hydraulic properties of the specimens, using conduction calorimetry, X-ray diffraction and differential scanning calorimetry, and also to measure the mechanical strength of the specimens when hydrated for 2 and 28 days. The compressive strength was satisfactory in relation to the estimated compositions. Both mixtures behaved the same with regard to heat development as well as the amount of ettringite formed during the first 24 h of the hydration.
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| 2. |
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| 3. |
- Adolfsson, Daniel, et al.
(författare)
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Steelmaking slags as raw material for sulphoaluminate belite cement
- 2007
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Ingår i: Advances in Cement Research. - : Thomas Telford Ltd.. - 0951-7197 .- 1751-7605. ; 19:4, s. 147-156
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, slags from the steelmaking industry are described and considered as a potential raw material within the field of sulphoaluminate belite cement. The objective of the study was to investigate the possibility of using a substantial amount of steelmaking slags as raw meal in the manufacture of a sulphobelitic clinker. A further aim was to compare the influence of different slags in relation to the formation of sulphoaluminate and the other clinker phases required. The behaviour of high temperature reactions was investigated by using thermogravimetric analysis coupled with a quadrupole mass spectrometer. Mineralogical observations were carried out through X-ray powder diffraction, and scanning electron microscopy. Three different mixtures and a single ladle slag were prepared using modified Bogue calculations, which are characterised by the assessment of a potential phase composition in order to produce belite-rich cement activated with sulphoaluminate. The results so far prove that steelmaking slags have the potential to be used as raw material, since sulphoaluminate along with polymorphs of dicalcium silicate and ferrite phases were detected after firing at 1200 degrees C in an air atmosphere.
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| 4. |
- Hökfors, Bodil, 1971-, et al.
(författare)
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Modelling the cement process and cement clinker quality
- 2014
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Ingår i: Advances in Cement Research. - : ICE Publishing. - 0951-7197 .- 1751-7605. ; 26:6, s. 311-318
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a recently developed simulation model that can be used as a tool for evaluating sustainable development measures for cement and lime production processes. Examples of such measures are introducing new combustion technologies such as oxy-fuel combustion, using biomass fuel and using alternative materials in the raw material feed. One major issue when introducing process changes is the need to maintain product quality. In some ways, oxygen-enriched air combustion resembles oxy-fuel combustion. The model results were validated and found to be consistent with full-scale operational data for normal running conditions and for a full-scale test with oxygenenriched air. The model shows, for example, that with an additional 1500 m3/h of oxygen, fuel addition at the calciners can increase up to 108% and the raw material feed rate can increase up to 116% for a process with a raw meal feed of 335.5 t/h.
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| 5. |
- Hökfors, Bodil, 1971-, et al.
(författare)
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On the phase chemistry of Portland cement clinker
- 2015
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Ingår i: Advances in Cement Research. - : Thomas Telford. - 0951-7197 .- 1751-7605. ; 27:1, s. 50-60
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Hökfors, Bodil, 1971-, et al.
(författare)
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Simulation of oxy-fuel combustion in cement clinker manufacturing
- 2015
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Ingår i: Advances in Cement Research. - Thomas Telford : ICE Publishing. - 0951-7197 .- 1751-7605. ; 27:1, s. 42-49
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Hökfors Wilhelmsson, Bodil, 1971-, et al.
(författare)
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A predictive chemistry model for the cement process
- 2008
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Ingår i: Zement, Kalk, Gips International. - Gutersloh, Germany : Bauverlag BV. - 0949-0205. ; 61:7, s. 60-70
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 8. |
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| 9. |
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| 10. |
- Viggh, Erik, et al.
(författare)
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Early formation of belite in cement clinker raw materials with slag
- 2021
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Ingår i: Advances in Cement Research. - : ICE Publishing. - 0951-7197 .- 1751-7605. ; 33:6, s. 249-256
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 11. |
- Viggh, Erik, 1957-
(författare)
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Modeling the influence of magnesium from alternative raw materials on the chemistry of Portland cement clinker
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 12. |
- Viggh, Erik, et al.
(författare)
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Raw meal and slag reactions during cement clinker formation
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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