Hydration-resistant lime refractories from Egyptian limestone and ilmeniteraw materials

Four refractory lime batches were processed from the pure limestone economi cally available at Beni Khaled, El Menia, Egypt up to firing at 1550 degree sC using a two-stage firing process. The ferry-ilmenite ore existing at Abu Ghalaga, Eastern Desert was added as a dopant material in amounts of 0.5, 1.0, 2.0, 3.0%. Densification parameters and hydration resistance of the fi red grains were investigated. The most dense hydration resistant grains wer e selected to assess their refractory quality by determining load-bearing c apacity and thermal shock resistance. These results were interpreted in the light of phase composition and microstructure of the fired grains. It is c oncluded that dense and hydration resistant lime grains can be processed by doping the pure limestone powder with 2.0-3.0 wt.% of ferry-ilmenite befor e firing up to 1550 degreesC. Such level of ilmenite content has contribute d in the densification of lime particles in the solid state and also by lim ited amount of the developed liquid phase. Hence. direct-bonded lime networ k is formed with partial interruption by a platey calcium-alumino-ferrite-t itanate phase. which crystallized on cooling from the liquid phase at the g rain boundaries of the lime-lime network. This improves the bulk density of fired grains to about 3.2-3.3 g/cm(3) and its rate of hydration to 4.15-3. 80 g/h without significant deterioration of its load-bearing capacity and t hermal shock resistance. (C) 2001 Elsevier Science Ltd and Techna S.r.l. Al l rights reserved.