Characterization of Limestone Surface Impurities and Resulting Quicklime Quality
Author:
Sandström Karin123ORCID, Carlborg Markus12ORCID, Eriksson Matias124ORCID, Broström Markus12ORCID
Affiliation:
1. Centre for Sustainable Cement and Quicklime Production, Department of Applied Physics and Electronics, Umeå University, SE-901 87 Umeå, Sweden 2. Thermochemical Energy Conversion Laboratory, Department of Applied Physics and Electronics, Umeå University, SE-901 87 Umeå, Sweden 3. Industrial Doctoral School for Research and Innovation, Umeå University, SE-901 87 Umeå, Sweden 4. The Swedish Mineral Processing Research Association—MinFo, Marieviksgatan 25, SE-100 44 Stockholm, Sweden
Abstract
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.
Funder
Nordkalk AB SMA Mineral AB Heidelberg Materials Cement Sverige AB the Ellen Walter Lennart Hesselman Foundation the Swedish Mineral Processing Research Association—MinFo the Industrial Doctoral School for Research and Innovation at Umeå University the Swedish Energy Agency
Reference49 articles.
1. Schorcht, F., Kourti, I., Scalet, B.M., Roudier, S., and Sancho, L.D. (2013). Best Available Techniques (BAT) Reference Document for the Production of Cement, Lime and Magnesium Oxide, European Commission, Joint Research Centre, Institute for Prospective Technological Studies. 2. 3D-DEM-CFD simulation of heat and mass transfer, gas combustion and calcination in an intermittent operating lime shaft kiln;Krause;Int. J. Therm. Sci.,2017 3. Lime Shaft Kilns;Piringer;Energy Procedia,2017 4. Cwik, K., Broström, M., Backlund, K., Fjäder, K., Hiljanen, E., and Eriksson, M. (2022). Thermal Decrepitation and Thermally-Induced Cracking of Limestone Used in Quicklime Production. Minerals, 12. 5. Investigation and prediction of sticking tendency, blocks formation and occasional melting of lime at HT (1300 °C) by the overburning test method;Vola;Constr. Build. Mater.,2021
|
|