Producing Insulating Refractory Bricks with Kaolin and Sawdust
Malu S. Peter Calabar, Nigeria
Journal Medwell. 2007. ¹2. p. 170 - 175
Abstract: This study was carried out to exploit kaolin and sawdust from local environs for the production ofinsulating refractory bricks, used in the construction of ceramic kilns, glass furnaces and gas-fired or electricovens. Results of the study show that kaolin and saw dust mix in the ratio of 1:1 by volume is found suitablefor producing good-quality insulating refractory bricks.
INTRODUCTION
The term refractory means hard to fuse. Refractorymaterials are generally employed for the construction offurnace flues, crucibles, etc., used in high temperatureoperations because of their resistance to the corrosiveaction of gases and slag present therein (Rashidi, 1986).High temperatures are involved in the industries dealingwith the treatment of ores and other materials for themanufacture of metallurgical, chemical, glass and ceramicproducts. As such, equipment used for the treatment ofthese materials must sustain the operating temperaturesand other working conditions such as corrosive and loadconditions. The objective of this research, is to find out ifthe mixture of Kaolin and sawdust can produce insulatingrefractory bricks that can be used in the construction ofannealing ovens (used as backers for glass furnaces) andceramic kilns-used by visual artists to fire works of art.
There are different types of refractory materialsnamely aluminosilicate, silica, dolomite, magnetite andchrome base, carbon, insulating, to mention just a few.However, this research focuses on insulating refractorymaterials. Insulating refractory materials are speciallyformulated to have a highly porous structure, low thermalconductivity and high thermal insulating propertiessuitable for minimizing heat losses and maximizing heatconservation in furnaces (Chester, 1973). Insulatingrefractory materials can be produced using fire clay mixedwith specific quantity of combustible materials like abinding agent (Olson, 1975). Other materials that haveinsulating refractory properties are glass wool, slag wool,vermiculite and ceramic fibres. China clay is sometimeused where very high-temperature refractory propertiesare required.
MATERIALS AND METHODS
The Kaolin used in this research was obtained fromkankara village in Katsina state. Two wooden mouldsmeasuring 31 ^25^6 cm and 52x32x6 cm were constructed.The sawdust was obtained from the wood workshop,ABU Zaria. Other materials used include a plastic bucket,a shovel, a large black polythene sheet, water and aceramic kiln for firing.
Kaolin and sawdust, which formed the major rawmaterials used, were measured in the ratio of 1:1 byvolume using a plastic container of 30 cm3. They werethoroughly mixed together (dry mixing) on the floor usingthe shovel to break the large lumps of kaolin into finerparticles. Water was added gradually and further mixingcontinued using the shovel until the desired viscosity ofthe mixed batch was obtained.
The mixed batch was covered with a black polythenesheet to prevent air from penetrating and also to facilitatethe aging period (fermentation of the batch). The agingperiod may take up to 5-10 days before the desired textureis achieved (Ewule, 1988). However, for the purpose ofthis study, due to the change in climatic condition(harmmatan season) the aging period was extended to twoand half weeks before the desired texture was achieved.After aging, the batch was ready for brick moulding.
Slab moulding: Before the brick moulding processcommenced, a large polythene sheet was spread on thefloor (to prevent the brick from sticking to the floor) andthe moulds placed on it, ready for filling-in of batchmixture. The bricks were made by dipping the woodenmould in water before filling each mould with batchmixture and the top smoofhened using a heavy metal ironslab to attain the desired levelness.