Development of Electrical Porcelain Insulatorfrom Local Ceramic Raw Materials andIndustrial Waste.

Abstract

In this study, two clay materials Bombawuha (BC) and Denkaka (DC), two feldspar materials Arerti (AF) andwolkite (WF) and Chancho sand (CS), as well as sugarcane bagasse ash (SCBA) and sugarcane fly ash (SCFA)wastes collected from Wonji Shewa sugar factory of Ethiopia were investigated to be used as a potential rawmaterials for producing quality electrical porcelain insulators. A 5kg of each samples of the aforementioned rawmaterials were collected and processed from deposits located at Bombawuha (6° 05′ 20′′ N and 38° 46′ 30′′ E),Denkaka (8° 33' 36" N, 39° 10' 29" E), Wolkite (8° 16′ 50′′ N and 37° 46′ 40′′ E), and Arerti (90o 6' and 90o 5' N and39o 46' and 39o 26' E), and Chancho (9° 18' 29.1240'' N and 38° 45' 11.2320'' E), respectively. They were dried, andground to sieve size of 63μm for clays, feldspars, and sugarcane bagasse ash and 45μm for sand, then themineralogy, chemical composition, thermal property, plasticity, and particle size distribution of raw materials werecharacterized by using x-ray diffractometry (XRD), atomic absorption spectrometer (AAS), Thermogravimetryanalysis (DTA-TG), Atterberg plasticity test, sieve-hydrometer analysis, respectively. Based on the raw materialschemical compositions different w% of mixed feldspar, bombawuha clay and quartz raw materials as well as SCBAwere selected to be used and accordingly six (6) different porcelain insulator body compositions without SCBA(labeled Batch-1, Batch-2, and Batch-3) and with SCBA (labeled: Batch-4, Batch-5, and Batch-6) were formulated.A total of two hundred four (204) (one hundred sixty two (162) a cylindrical shaped for physical and electricalstrength test plus forty two (42) rectangular-shaped for mechanical strength test) bodies of the desired formulationswere prepared. The batches were fired at firing temperature of 1200°C, 1250°C, and 1300°C and firing time of1.5hr, 2hr and 2.5hr. Finally, the fired products were investigated for their physical properties (water absorbance,bulk density, and apparent porosity), electrical properties (dielectric strength), mechanical strength (flexuralstrength/modulus of rupture), phase analysis by XRD and microstructure by SEM-EDS. XPS were also used tocomplement the XRD data. The aforementioned properties of porcelain insulators were analyzed as a function offiring temperature and time. Only those fired samples which possess good electrical properties were used formechanical test. The XRD and AAS results revealed that unlike Denkaka clay in Bombowha clay, kaolinite mineralwas found to be a major mineral constituent with appreciable silica (46.72 wt%) and alumina (35.32 wt%) content, ithas relatively higher level of clay fractions (20.58%); and has middle range plasticity index (PI = 11.2%) which issuitable and encouraging for optimal behavior in pressing and drying. The ratio of Al2O3/SiO2 met the requiredamount for mullite phase formation during the porcelain body's sintering. This was observed in the DTA curve at1001.23 oC. The Arerti (AF) contains mainly albite and the Wolkite feldspar (WF) is predominantly composed ofanorthoclase minerals with less alkali contents (Na2O, K20) of <6wt %. The sugarcane ashes (SCBA and SCFA)waste contained SiO2 (65.06+ %) as a major oxide, and followed by Al2O3 (10.88+ %), which is comparable tonatural feldspar, and it has higher alkaline oxides (K2O and Na2O) content and iron oxide as compared to naturalfeldspars. This implies the sugarcane waste ashes can be used as an alternative to substitute the natural feldspar withproper formulation in which the SCBA is a preferred materials over SCFA as it contained relatively higherproportions of refluxing agent (8.66%). Among the tested porcelain insulator bodies without SCBA, the test bodywith composition of 40% Clay, 40% feldspar and 20% quartz (Batch-3) and fired at 1250 °C for 2 h exhibited waterabsorbance of 0.17%, apparent porosity of 0.42%, bulk density of 2.45 g/cm3, the dielectric strength of 8.22 kV/mmand flexural strength of 43.63 MPa, which satisfies the required properties for quality porcelain insulators.Moreover, the physical-mechanical properties and dielectric strength measured for each porcelain sample withSCBA confirmed batch SCBA10 with the composition of (10% SCBA waste, 50% BC, 30% mixed Feldspar (AFand WF in 50:50%), and 10% CS) fired at 1250°C and at firing time 2.5hr was found to have the dielectric strengthof 6.14 kV/mm, dielectric strength of 42.53 MPa and water absorption of 0.35%, which satisfies the obligatoryproperties for quality porcelain insulators. In conclusion, the experimental result of this study confirmed thatstandard quality porcelain electrical insulators could be produced using locally available raw materials (Clay,Feldspar, and quartz) and the partial replacement of Feldspar by sugarcane bagasse ash (SCBA) waste in Ethiopia atoptimized condition.