DEVELOPING A CORROSION RESISTANT RAMMING MIX FOR LINING FRITTING FURNACES USING KAOLIN FROM SELECTED STATES IN NIGERIA

Abstract

Refractory materials are important to ceramic heat processes. A process like the frit production needs refractory that is resistant to attack by molten glass. However, lack of such refractory seems to be one of the causes of slow development of indigenous glaze production in Nigeria. This study focused on fortification of locally available kaolin in some selected States in Nigeria for the production of corrosion resistant refractory for the lining of frit furnaces. Kaolin samples were randomly taken from seven deposits (Omifun deposit in Ondo State, Ijero and Ikere deposits in Ekiti State, Okpella deposit in Edo State and Onibode, Akiegun, and Siun deposits in Ogun State) using composite sampling method. The x-ray diffraction (XRD) and the proton induced x-ray emission (PIXE) methods were used for mineralogical and chemical analysis respectively. Atterberg method was used to assess the plasticity of the clay samples. The multiple-criteria decision-making (MCDM) method was employed for selecting the right clay for fortification based on the criteria of apparent porosity, kaolinite content, anatase content, and plasticity index. The selected clay was blended with graphite, alumina, and zircon in a stepwise mode until the right combination of material of the appropriate ratio was reached. The selected composition was then subjected to corrosion resistance test. Result shows that the kaolin sample from Okpella deposit with kaolinite content of 94.06%, anatase content 0.83%, and plasticity index 16.03 and apparent porosity of 30 % when fired at 1200oC, ranked best for fortification. Graphite reduces the desirable physical-mechanical properties like density and increases porosity of the clay samples. Alumina imparts higher density on the clay than zircon but zircon stabilized with magnesium oxide imparts the highest density. The sample with 5% alumina has the required physical-mechanical property at the temperature of 1250oC. Sample with 5% alumina and 10% of MgO stabilized zircon shows the highest resistance to molten glass attack. There is no evidence 3 of degradation of the lining of the prototype furnace by the frit and no contamination of the frit by the lining. Inclined plane shows prospect for adaptability in the construction of mini fritting furnace as a driving force to cause frit to flow out of the furnace during melting. Clay of high kaolinite content, if fortified appropriately, can be a source of raw material for lining fritting furnaces. The inclusion of zircon is recommended for clay intended to be used for lining furnaces. In whatever form zirconium is to be used, it is recommended to be stabilized with calcium oxide (CaO) or magnesium oxide (MgO). The clay deposits in Ogun State especially the Siun solomo deposits and Akiegun, needs further exploration. The peculiar behaviour of Omifun deposit clay requires further investigation in order to unravel the reason for its incessant cracks when fired. Both the lining and the prototype furnace are recommended to be scaled up for production of frit to boost glaze production in the study area.