ABSTRACT
The industries in Nigeria depend heavily on the use of refractories and their demands are presently being met, to a large extent by the importation of these refractories. Regrettably, about $229 million is expended annually to import these materials into the country. Consequently, it leads to the draining of Nigeria's foreign reserve and these turns negatively affect the economic on the increase of capital expenses. Thus, it has become necessary to explore this clay for the production of refractories locally for blast furnaces in order to reduce their importation and meet the need of technological requirements of the country, and to conserve the much needed foreign exchange. The characterization of clay from Maraban Rido Kaduna State and its application in the production of dense refractory firebricks was investigated. The result shows that the clay was found to disintegrate into smaller angular particles after being mined with cream coloration, moderately hard with smooth texture and in lump sizes (ranging from 5cm to 15cm). Maraban Rido clay had a liquid limit of 41.5%, a plastic limit of 33.5% and a plasticity index of 8%. At firing temperature of 1280oC, the clay changed from cream colour to off-white. The off-white coloration might be due to the presence of low concentrations of iron oxides in the sample. The average firing shrinkage clay samples was 7.1% with little cracks. The X-ray fluorescence elemental analysis results showed Al2O3 and SiO2 to be the dominant oxides at 44.0% and 51.8% respectively. The values of impurity oxides content for the clay sample such are K2O (0.08%), CaO (0.16%), Fe2O3 (1.53%), TiO2 (0.26%) etc. contents of 4.21% are all within the tolerable impurities associated to alumino-silicates group of refractories of about 2 to 5%, make the clay suitable for the production of superheat duty alumino-silicate refractory material. The dense firebricks produced from Maraban Rido clay showed little cracks as-formed, drying and firing at 1500oC with average firing shrinkage value of 7.1%, which is within the recommended values of 7.0-10%. The apparent porosity assessment values for Maraban Rido dense firebricks averaged 33% which does not fall within the recommended values of 15-25%, while the bulk density on the average was 1.75g/cm3, does not fall within the acceptable level of fireclay brick of between 1.9-2.3g/cm3. This could be due to the inadequate compaction pressure during the pressing process, coupled with shapes of the particle of the grog, since the grog is manually crushed and the reaction occurring on firing. The cold crushing strength averaged 294.77kg/cm2 meet the recommended standard of 150kg/cm2 minimum for fireclay, the practical significance of this value will be strong enough to withstand handling, transportation and abrasion in services and the thermal shock resistance on the average gave a value of 30 cycles at temperature of 1200oC, term as an excellent thermal shock resistance. The Maraban Rido clay formed fireclay refractory firebrick which is among the alumino-silicates group of refractories. The Maraban Rido firebrick can be used in moderate heat treatment operation such as lining of regenerative chambers, recuperative chambers, chimney and annealing furnaces.
