| 1. |
- Hökfors, Bodil, 1971-, et al.
(författare)
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Improved Process Modeling for a Lime Rotary Kiln Using Equilibrium Chemistry
- 2012
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Ingår i: Journal of engineering technology. - : American Society for Engineering Education. - 0747-9964. ; 29:1, s. 8-18
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Tidskriftsartikel (refereegranskat)abstract
- This article describes an improved process model for simulation of the manufacturing process of lime in a rotary kiln. The model simulates ideal behavior of complex chemical systems with an assumed homogenous mixing without time-dependent factors. It is a totally predictive model that excludes the empirical parameters. The model is a chemical phase equilibrium model that calculates the final product in a non-equilibrium mode, according to established methods. The phase chemistry is among the most complex found in the literature for lime manufacturing. The thermodynamic data used in the model is based on 11 components (Ca, Si, Al, Fe, K, S, Cl, C, H, O and N). The fuel has an important role in the lime manufacturing process. Special attention is required since it is fed directly into the process via the burner and can influence the process and final product. In the model, the fuel is defined in order to have it behave in a realistic way, and operational data from a full scale lime plant verify the simulation results. The simulated amounts of gas and solids correlate well with operational data. The predicting chemical composition of the product needs improvement by adding more system components and their related compounds to the thermodynamic database. Simulation results from co-combustion of coal and processed waste based fuel oil that it is a versatile tool for predicting product quality and amount, temperature profiles of the rotary kiln, and exhaust gas composition and amount.
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| 2. |
- 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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| 3. |
- 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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| 4. |
- Hökfors, Bodil, 1971-
(författare)
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Phase chemistry in process models for cement clinker and lime production
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The goal of the thesis is to evaluate if developed phase chemical process models for cement clinker and lime production processes are reliable to use as predictive tools in understanding the changes when introducing sustainability measures.The thesis describes the development of process simulation models in the application of sustainability measures as well as the evaluation of these models. The motivation for developing these types of models arises from the need to predict the chemical and the process changes in the production process, the impact on the product quality and the emissions from the flue gas.The main chemical reactions involving the major elements (calcium, silicon, aluminium and iron) are relatively well known. As for the minor elements, such as sodium and potassium metals, sulphur, chlorine, phosphorus and other trace elements, their influence on the main reactions and the formation of clinker minerals is not entirely known. When the concentrations of minor and trace elements increase due to the use of alternative materials and fuels, a model that can accurately predict their chemistry is invaluable. For example, the shift towards using less carbon intensive fuels and more biomass fuels often leads to an increased phosphorus concentration in the products.One way to commit to sustainable development methods in cement clinker and lime production is to use new combustion technologies, which increase the ability to capture carbon dioxide. Introducing oxy-fuel combustion achieves this, but at the same time, the overall process changes in many other ways. Some of these changes are evaluated by the models in this work.In this thesis, a combination of the software programs Aspen Plus™ and ChemApp™ constitutes the simulation model. Thermodynamic data from FACT are evaluated and adjusted to suit the chemistry of cement clinker and lime.The resulting model has been verified for one lime and two cement industrial processes.Simulated scenarios of co-combustion involving different fuels and different oxy-fuel combustion cases in both cement clinker and lime rotary kiln production are described as well as the influence of greater amounts of phosphorus on the cement clinker quality.
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| 5. |
- Hökfors, Bodil, 1971-, et al.
(författare)
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Reducing the CO2 footprint of cement production by electrification
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Transformative actions in CO2 emitting industries are needed to reach the Paris climate agreement.The cement industry, which is responsible for 5-7% of the global CO2 emissions, has the possibility tomake a difference.Cement production is related to two sources of CO2; 1/3 from combustion of fuels and 2/3 fromcalcination of limestone in the cement raw meal. If all the fuels were to be substituted with non-fossilelectricity, the environmental gain would be significant. Cementa and Vattenfall are evaluatingpossibilities on how electricity can be used to substitute fuels in the cement production by 2030.By using electricity for heating, several positive effects are achieved in the production process. Thecleanness of the exhaust gas will be higher due to elimination of volatiles from fuels. The energyconsumption decreases due to lesser volume of gas to be heated. This is related to the exclusion ofnitrogen gas in the process.A feasibility study comprising literature survey and small scale tests have been performed. Electricalheating techniques showing potential are; microwave heating, plasma torches, flash calcination withelectrical heating, hydrogen combustion and a combination of the mentioned techniques.The most relevant finding is that the combustion related CO2 emissions will be eliminated; thecapturing step will be enhanced since the CO2 gas from calcination is clean and accordingly the needof storage or utilization of CO2 is decreased.
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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, Bodil, 1971-, et al.
(författare)
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Speciation of trace and minor elements in cement clinker production
- 2015
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Ingår i: 14th International Congress on the Chemistry of Cement 2015.
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Konferensbidrag (refereegranskat)abstract
- Trace and minor elements like arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), antimony (Sb), thin (Sn), thallium (Tl), vanadium (V) and zinc (Zn) are important in cement clinker manufacturing. Even in low concentrations these elements influence the production processes, the quality of the products and the environment. The environmental issues are the volatility of elements at high temperatures to the atmosphere and the leachability of elements from concrete products to the surroundings. If a prediction tool was available of the fate of elements to the gas phase and to the cement clinker phases several advantages could be achieved. Therefore a calculation tool is developed based on thermodynamic equilibrium calculations with a two-step method. Most of the thermodynamic data are taken from the FactSageTM database 6.4 and the solutions phases are adjusted for cement clinker and similar applications.The tool estimates the volatility of the elements at a temperature below onset of melt formation during production and after formation of melt. The results from the simulations are volatility of each element at low and high temperature and if the element is non-volatile it concentrates in the condensed phases.In this article four sets of full scale industrial data from a cement clinker and a lime production plant are used to evaluate the prediction tool. The results comprise an inventory of the extent of thermodynamic data for selected trace and minor elements, thermodynamic calculations with distribution to gas or condensed phases with input from full scale measurements, the influence of oxidizing, less oxidizing and slight reducing conditions on the behavior of elements, results from full scale industrial measurements and a comparison between the calculated and the measured distribution of elements. For the cement clinker production eleven elements and for the lime production twelve elements are considered.
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| 8. |
- 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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