Effects of impurities on phase equilibrium in quicklime and cement clinker production

The production of quicklime and cement clinker are energy-intensive processes resulting in significant CO2 emissions. Fuel switching, electrified heating, and carbon capture have gained attention as means of addressing this. Conventional production processes are direct-fired, meaning that the impurities, which originate from either quarries or fuels, interact with the product, influencing process performance and product quality. The suggested strategies for addressing CO2 emissions will alter the process conditions. For example, introducing electrified heating using plasma would shift the process atmosphere to primarily CO2, possibly affecting volatilisation and recirculation. The overall aim of this thesis was to generate new knowledge on the impact of impurities under process conditions in the context of the shift towards more sustainable quicklime and cement clinker production. Limestone surface impurities and their effects on quicklime product quality were evaluated. Ash-quicklime interactions were studied both on a laboratory scale and using multicomponent chemical equilibrium calculations (MECs). The volatilisation of minor elements in cement clinker production was investigated on a laboratory scale, and using a counter-current MEC-model with both a conventional combustion atmosphere and high-CO2 atmosphere. The detailed analysis of the limestone surface layer showed enrichment of impurities. However, quicklime sampled from a parallel flow generative kiln (PFR) showed low amounts of reactants from surface impurities, which were suggested to contribute to build-ups and increased levels of lime-kiln dust instead. Laboratory-scale studies of coal ash and quicklime interactions and MECs showed that typical cement clinker phases are thermodynamically stable at the coal ash-quicklime interface. Porosity and pore-size distribution were evaluated in pure quicklime samples and quicklime samples exposed to olive pomace, pine bark, and wheat straw ash. Olive pomace ash