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To produce quicklime, high calcium carbonate rocks, including limestone, are burned in industrial kilns at 1100–1450 °C. As a consequence of the high temperatures, the carbonate rock can break and decrepitate into fine material, causing operational problems and material losses. In the present paper, an industrial case study on thermal decrepitation was performed on Boda Limestone from the Jutjärn quarry in Dalarna, Sweden. We analyzed 80 limestone samples for thermal decrepitation; furthermore, the correlation with chemical composition was statistically analyzed. The experiments were complemented by a detailed analysis of thermally-induced cracking at a range of temperatures (ambient, 500 °C, 800 °C, and 1150 °C) for two limestone samples with similar chemical compositions but with very different decrepitation behaviors. Decrepitation was analyzed by an in-house method, the chemical composition by XRF, and the thermally-induced cracking was investigated by SEM and image analysis. No strong correlation was found between thermal decrepitation and the chemical composition of the limestone. For the sample with low thermal decrepitation, a dense narrow network of fractures was found after full calcination; however, this network was not observed in the sample with high thermal decrepitation. A plausible explanation for the different decrepitation behaviors is that this fracture network releases internal stress and stabilizes the calcined rock. The obtained results can help in predicting limestone thermal decrepitation, enabling increased resource efficiency in quicklime production.

Carbonation of quicklimes degrades their quality and can occur when process temperatures become sufficiently low. This risk can be heightened in process atmospheres containing high CO2 and steam. To assess this, carbonation experiments involving atmospheres with different CO2 concentrations and steam were performed at 700 °C on 2.5–5 mm quicklime granules derived from sedimentary and metamorphic limestones. The carbonation extents of the quicklimes derived from metamorphic limestones during the fast stage were higher, corresponding with their larger specific surface areas. However, SEM analysis revealed that these quicklimes had fine structures with relatively small pores that likely became blocked during carbonation, causing plateauing of carbonation that appeared to be mainly limited to particle surfaces. The presence of steam caused only mild enhancements in carbonation of these quicklimes. Contrastingly, the quicklimes derived from sedimentary limestones had lower specific surface areas that concurred with their thicker structures and larger pores. The carbonation extent during the initial fast stage was correspondingly lower, but carbonation progressed at a sustained rate thereafter. The resulting high carbonation extents appeared to be facilitated by the larger pore volumes available for carbonate growth, including locations inside particles. The presence of steam greatly enhanced the carbonation of these quicklimes. Overall, every quicklime exhibited high carbonation extents despite being granular-sized. Moreover, their distinctive carbonation behaviors and microstructures could be delineated by their parent limestone type. These findings should be considered when carbonation in high CO2 atmospheres may occur, e.g., during cooling in electrical lime kilns.