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Separate Calcination in Cement Clinker Production

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Separate Calcination in Cement Clinker Production Separate Calcination in Cement Clinker Production A laboratory scale study on how an electrified separate calcination step affects the phase composition of cement clinker Amanda Vikström Master thesis, 30 hp M.Sc. in Energy Engineering, 300 hp Department of Applied Physics and Electronics, Spring term 2021 Separate Calcination in Cement Clinker Production A laboratory scale study on how an electrified separate calcination step affects the phase composition of cement clinker Amanda Vikström [email protected] Master Thesis in Energy Engineering Department of Applied Physics and Electronics Umeå University Examiner: Robert Eklund Supervisors: Matias Eriksson, José Aguirre Castillo and Bodil Wilhelmsson Performed in collaboration with Cementa AB and the Centre for Sustainable Cement and Quicklime Production at Umeå University 31 may 2021 Abstract Cement production is responsible for around 7% of the global anthropogenic carbon dioxide emissions. More than half of these emissions are due to the unavoidable release of carbon dioxide upon thermal decomposition of the main raw material limestone. Many different options for carbon capture are currently being investigated to lower emissions, and one potential route to facilitate carbon capture could be the implementation of an electrified separate calcination step. However, potential effects on the phase composition of cement clinker need to be investigated, which is the aim of the present study. Phases of special interest are alite, belite, aluminate, ferrite, calcite, and lime. The phase composition during clinker formation was examined through HT-XRD lab-scale experiments, allowing the phase transformations to be observed in situ. Two different methods of separate calcination were investigated, one method in which the raw meal was calcined separately, and one method where the limestone was calcined separately. The former yielded an alite amount similar to that of the reference experiments, whereas the latter method yielded a lower amount. It could, unfortunately, not be excluded that the difference was due to poor experimental conditions, and additional experiments are needed to investigate the matter further. The study does, however, indicate that a calcined raw meal might be used to produce a clinker of similar phase composition concerning major phases belite, aluminate, ferrite, alite, and free lime. A raw meal containing calcined limestone might, however, need longer residence time at clinkering temperature too obtain similar phase composition. In addition, a raw meal containing calcined limestone was observed to be carbonated to a greater extent upon reheating than a calcined raw meal. Further experiments are needed to fully understand the effects on clinker composition of an electrified separate calcination step, and several improvements to the experimental method are given in the study. Acknowledgements Many people have helped and supported me throughout the work of this master thesis; I hope you all know how grateful I am. This master thesis was done in collaboration with Cementa AB and the Centre for Sustainable Cement and Quicklime Production at Umeå University. I would like to thank my industrial supervisors José Aguirre Castillo and Bodil Wilhelmsson for providing me with an interesting project, as well as your thoughts and advice throughout the process. A special thanks to José who helped me perform the experiments at Cementa’s plant in Slite, as well as the time-consuming analysis of the XRD data. José performed the whole analysis of one of the experiments, and supervised my analysis of the other three experiments. I am very grateful for his commitment to this project and the warm welcome I received during my stay in Slite. A big thanks to my university supervisor Matias Eriksson, who has always been available to answer my questions and give meaningful advice. Matias has managed to find the perfect balance between challenging me in my academic work, while still providing guidance when I needed it. His support with my writing has been especially important, without him this thesis would have ended up three times as long without ever getting to the point. I would also like to thank my steering group consisting of Markus Broström, Markus Carlborg, and Tina Hjellström, who have been giving their feedback and thoughts on my work throughout the semester. Especially Markus Carlborg who has spent endless hours trying to teach me XRD analysis prior to the start of my master thesis. His patience and never-failing support has been invaluable. I would also like to acknowledge the Thermochemical Energy Conversion Laboratory, TEC-lab, at Umeå University for sharing research infrastructure, enabling me to carry out a large part of my work from Umeå. I would also like to express my gratitude to everyone working at TEC-lab for welcoming me into your group and making my office days both educational and tremendous fun. A special thanks to Nils Skoglund and Charlie Ma who introduced me to the exciting field of thermal energy conversion 1.5 years ago, and inspired me to continue my engineering studies when I was hopelessly unmotivated. Without them, I would probably never even have made it to starting my master thesis. Lastly, I would like to thank my family and friends for their support and encouragement throughout the whole process. Contents 1 Abbreviations .......................................................................................................................................... 1 1.1 Cement chemical nomenclature ....................................................................................................... 1 1.2 Experiment specific abbreviations ............................................................................................... 1 1.3 Other .............................................................................................................................................. 1 2 Introduction ............................................................................................................................................ 2 3 Background ............................................................................................................................................. 3 3.1 The cement production process.................................................................................................... 3 3.1.1 Raw materials and pre-treatment ............................................................................................ 4 3.1.2 Preheating and calcination ....................................................................................................... 4 3.1.3 Cement kiln................................................................................................................................ 4 3.1.4 Cooling and post-treatment ...................................................................................................... 5 3.2 The main phases in cement clinker .............................................................................................. 5 3.2.1 Alite ............................................................................................................................................ 5 3.2.2 Belite .......................................................................................................................................... 6 3.2.3 Aluminate .................................................................................................................................. 6 3.2.4 Ferrite ........................................................................................................................................ 6 3.3 Calcination in cement production ................................................................................................ 6 3.4 Clinker phase chemistry ................................................................................................................ 7 3.5 Quantitative analysis of the phases in cement clinker ................................................................ 8 4 Experimental .......................................................................................................................................... 8 4.1 Sample preparation ....................................................................................................................... 8 4.2 In situ HT-XRD experiments........................................................................................................ 9 4.3 Qualitative and quantitative phase analysis ............................................................................... 11 5 Results and discussion ......................................................................................................................... 12 5.1 Temperature determination ....................................................................................................... 12 5.2 Clinker formation ........................................................................................................................ 12 5.3 Influence of separate calcination ................................................................................................ 19 5.3.1 Temperatures up to calcination .............................................................................................. 19 5.3.1 Temperatures from calcination to clinkering ........................................................................ 19 5.3.2 Cooled clinker .........................................................................................................................
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