Influence of Kaolin and Silica on some Refractory Properties of Pingell, Zircon Sand

Abstract

100kg of zircon sand raw material was obtained from Pingell, Toro Local Area of Bauchi State while silica and kaolin were used as the additive materials in different proportions. The materials as received were wet and in large chunks, and was sun dried prior to crushing with Jaw crusher and sieved with the sieve of size 100 µ to obtain fine powder particles. Samples of various compositions were prepared from the powder particles of Zircon sand (X); Zircon sand and silica (Y); zircon sand, silica and kaolin (Z) and mixed together based on the experiment’s program with a predetermined amount of water in the mixer. Refractory brick test specimens were prepared by standard methods from samples A, B and C and subjected to refractory test such as apparent porosity, bulk density, cold crushing strength, linear shrinkage, thermal shock and refractoriness in order to evaluate the effects of adding silica and gypsum to Pingell zircon sand and investigate its suitability as raw material for refractory brick production and furnace linings. From the result obtained, the average porosity of X, Y and Z is 13.5, 18.3 and 21.6 % respectively while the respective bulk density are 3.2, 2.0 and 1.8 g/cm3. The values of the cold crushing strength for samples X, Y and Z are respectively 25.5, 23.4 and 18.8 MN/m2 but the firing shrinkage is 4.5, 5, and 6.5 %. Thermal shock resistance of 26, 20 and 22 cycles were obtained respectively for X, Y and Z. Refractoriness of 1600, 1580 and 1610 0C were obtained respectively for samples X, Y and Z. The porosity, firing shrinkage and refractoriness increased with increase in the addition of silica and kaolin to zircon sand whereas the bulk density, thermal shock resistance and cold crushing strength of zircon sand decreased with the addition of silica and kaolin but the addition of silica reduced the refractoriness of the zircon sand. The addition of silica and kaolin in the appropriate proportions improved the refractory properties of the zircon sand and hence will find applications in the production of refractory bricks and furnace lining.