Applicability of Egyptian limestones for calcination

摘要

The calcination product of limestone is a strategic industrial product. This work evaluates the suitability of AlKoraymat-AIZafarana limestones for calcination. These limestones are near to the electrical and gas stations of the Alkoraymat area, Egypt. Spot samples and channel samples were collected and tested for their petrographic, chemical and mineral composition using transmitted light microscopy, X-ray micro-tomography, scanning electron microscopy, X-ray fluorescence, X-ray diffraction, differential and thermo-gravimetric analyses. The representative channel samples were calcined in a muffle furnace at 1000°C for different decarbonation times and then analysed for the free lime determination by applying the Sugar method. About 5 million tons of chemically pure limestone are estimated at Alkoraymat. The average CaO content is 55% and the total impurity oxides (SiO_2, Al_2O_3 and Fe_2O_3) is 0-73%. The limestone microstructure is mainly grain-supported and dominated by Nummulites cemented by neomorphic-sparitic groundmass. The optimum calcination condition is 1000°C for 1 h for all channel samples. Some samples show higher calcination rate than the others due to their characteristic inter-particle together with the intra-particle pores. The post-calcination distribution maps of the limestone purity and free lime indicate that these limestones could be quarried in the SE direction for calcination and lime production.