Development of a clay-rich interval above a limestone substrate in the Condroz region of southern Belgium

Ranst, Éric Van; Mees, Florias; Bock, Laurent; Langohr, Roger

doi:10.1016/j.catena.2014.05.012

Cited by 4 publications

(2 citation statements)

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“…Impurities that originate in materials deposited simultaneously with CaCO 3 (s) and that are dispersed throughout the formation are classified as homogeneous impurities. Impurities that appear as inclusions or as loosely embedded materials formed during the sedimentation process often occur as layers in the deposit [45] and are classified as heterogeneous impurities. Common impurities are clay and siliceous matter, and the major impurity elements are Si, Al, Fe, and Mg [44,46].…”

Section: Introductionmentioning

confidence: 99%

Impact of Limestone Surface Impurities on Quicklime Product Quality

Eriksson,

Sandström,

Carlborg

et al. 2024

Minerals

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Quicklime is produced through the thermal processing of limestone in industrial kilns. During quarry operations, fine particulate quarry dust adheres to limestone lump surfaces, increasing the bulk concentration of impurities in limestone products. During thermal processing in a kiln, impurities such as Si, Mg, Al, Fe, and Mn react with Ca, reducing quicklime product quality. Which reactant phases are formed, and the extent to which these result in a reduction in quality, has not been extensively investigated. The present study investigated as-received and manually washed limestone product samples from two operational quarries using elemental compositions and a developed predictive multi-component chemical equilibrium model to obtain global phase diagrams for 1000–1500 °C, corresponding to the high-temperature zone of a lime kiln, identifying phases expected to be formed in quicklime during thermal processing. The results suggest that impurities found on the surface of the lime kiln limestone feed reduce the main quality parameter of the quicklime products, i.e., calcium oxide, CaO (s), content by 0.8–1.5 wt.% for the investigated materials. The results also show that, in addition to the effect of impurities, the quantity of CaO (s) varies greatly with temperature. More impurities result in more variation and a greater need for accurate temperature control of the kiln, where keeping the temperature below approximately 1300 °C, that of Hatrurite formation, is necessary for a product with higher CaO (s).

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Section: Introductionmentioning

confidence: 99%

Impact of Limestone Surface Impurities on Quicklime Product Quality

Eriksson,

Sandström,

Carlborg

et al. 2024

Minerals

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“…Homogenous impurities co-deposit with the limestone and are dispersed throughout the formation. Heterogeneous impurities appear as inclusions or as loosely embedded materials and are formed during the sedimentation process; they are seen as layers in the deposits [7][8][9]. Quicklime quality is influenced by factors like kiln configuration and fuel characteristics, but it is primarily influenced by the composition and characteristics of the raw material: the limestone feed rock [8,10].…”

Section: Introductionmentioning

confidence: 99%

Characterization of Limestone Surface Impurities and Resulting Quicklime Quality

Sandström,

Carlborg,

Eriksson

et al. 2024

Minerals

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Quicklime, rich in CaO(s), is generated by calcining limestone at high temperatures. Parallel-flow regenerative lime kilns are the most energy-effective industrial method available today. To prevent major disruptions in such kilns, a high raw material quality is necessary. Under some conditions, impurity-enriched material may adhere to limestone pebbles and enter the kiln. In this study, limestone and corresponding quicklime were analyzed to evaluate the extent and composition of surface impurities and assess the effect on quicklime product quality, here defined as free CaO. This was performed by sampling and analyzing limestone, quarry clay, laboratory-produced quicklime, and industrially produced quicklime with XRF, SEM/EDX, and XRD; interpretations were supported by thermodynamic equilibrium calculations. In the laboratory-produced quicklime, the surface impurities reacted with calcium forming Larnite, Gehlenite, Åkermanite and Merwinite, reducing the quicklime quality. The results showed that the limestone surface layer comprised 1.2 wt.-% of the total mass but possessed 4 wt.-% of the total impurities. The effect on industrially produced quicklime quality was lower; this indicated that the limestone surface impurities were removed while the material moved through the kiln. Multicomponent chemical equilibrium calculations showed that the quarry clay was expected to be fully melted at 1170 °C, possibly leading to operational problems.

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