The Effects of Firing Temperatures on the Performance of Insulating Firebricks Containing Different Proportions of Alumina and Sawdust

This work studied the effects of firing temperatures on the refractory properties of insulating firebricks produced from a blend of hydrometallurgically purified clay, high alumina cement and sawdust. Twenty grams out of a bulk (1000 Kg) of clay obtained from Ipetumodu in Nigeria was analyzed for size range, consequent upon which the remaining bulk was sieved to 100 μm, being the average size. The bulk was there after leached under a predetermined condition (1.6 mol/dm3 of oxalic acid at 70oC for 150 min and 200 rev/min agitation speed) and cylindrical samples (5 cm diameter by 5 cm high) containing different quantities of high alumina cement (5% - 20%) and sawdust (1% - 5%) were prepared, dried at 110oC and subsequently fired at 900oC, 1100oC, 1300oC and 1500oC, at the rate of 4oC/min and soaked for 2 hrs. These samples were subjected to different refractory tests (permanent linear change, modulus of rupture, bulk density, cold crushing strength and apparent porosity). Even though samples containing more than 20% alumina crumbled at elevated temperatures, it was still observed that the bricks performed to expectations at lower alumina contents, even at 1500oC. The sample containing 3% sawdust and 10% alumina cement however, gave the desired requirement for preparing good insulating firebricks with reliable phase integrity, as revealed by scanning electron microscopy (SEM).

Production of Refractory Lining for Diesel Fired Rotary Furnace, from Locally Sourced Kaolin and Potter’s Clay

This research was conducted to formulate a refractory lining recipe for lining diesel fired rotary furnace from locally sourced kaolin, using locally sourced potter’s clay as binder. Six samples (A-F) of kaolin clay mined locally from Apata II area, Ondo road, in Ile-Ife,Nigeria, were roasted at 1200oC held for 8 hours, mixed with different percentages of raw kaolin and appropriately made into briquettes using potter’s clay of good plasticity as binder. The samples were tested for various refractory properties. The result showed that sample mixes A (100% chamotte), B (80% chamotte, 20% rawkaolin) and C (60% chamotte, 40% raw kaolin) are considered to have good properties. However, the optimum material-mix for the refractory bricks lining, with particular reference to the highest thermal shock resistance was found to be 80% chamotte mixed with 20% raw kaolin.

Production and Characterization of Porous Insulating Fired Bricks from Ifon Clay with Varied Sawdust Admixture

The effect of compositions of saw dust admixture on thermal conductivity and other mechanical/refractory properties of Ifon Clay was investigated. The raw clay gotten from Ifon in Ondo state was first processed to very fine particles and characterized using SEM/EDX, XRD and XRF. Sawdust from mahogany tree procured from a saw mill in Akure the State capital of Ondo State was also dried to remove moisture present. A composite mixture of this dried saw dust with the processed clay was made at various proportions of the saw dust, with a little addition of water for plasticity. Sam- ples of cylindrical dimensions were then produced from the mounting press by the process of compaction with a very high pressure. The samples were dried and then finally fired in the furnace at 1000?C for a final curing. Properties which include thermal shock resistance, bulk density, cold crushing strength, thermal conductivity and porosity were obtained by the appropriate standard test methods. The microstructures of the fired samples were also characterized with SEM using back scattered secondary imaging. The results show that the amount of sawdust admixture affects the properties variously;porosity increases with percentage increase in sawdust admixture while the thermal conductivity and other properties of the sample reduce with percentage increase in sawdust admixture. It was concluded that for structural insulating bricks where compressive strength is important the sawdust admixture should not exceed 10 to 15 percent.