การเตรียมและการหาลักษณะสมบัติของอิฐฉนวนทนไฟโดยใช้กากตะกอนชุบผิวอะลูมิเนียม เถ้าแกลบ และเถ้าลอย

Abstract

Insulating refractory brick is known as a ceramic refractory which can withstand to high temperature and apply in furnace or severe temperature area. Significant properties include high porosity, low density, heat resistance and low thermal conductivity. This study focused on the utilization of industrial wastes of aluminium anodizing sludge, rice husk ash and fly ash as raw materials of an insulating refractory brick. The chemical and phase composition of these raw materials are consisted of alumino-silicate compound which could replace common natural raw materials in ceramic industry. Moreover, the ground rice husk can be sued as a pore former. Ball clay and white cement are used as binders. The optimum composition of this insulating refractory brick is composed of aluminium anodizing sludge : rice husk ash : fly ash :ball clay : rice husk : white cement in the mass ratio of 60 : 17 : 10 : 15 : 11.2, respectively. The mixture was shaped by a hydraulic pressing machine with a pressure of 2.5 MPa. The pressed specimens were fired for the organic matter burnt out at 600℃ for 2 hours. The temperature was then ramped to 1325 ℃ for sintering for 2 hours. The bulk density of samples was 0.81±0.00 g/cm, water absorption was 86.16±0.35%, and apparent porosity was 70.65±0.37%, closed to that of the commercial insulating refractory bricks values. The coefficient of thermal expansion from 50-1000 ℃ was 6.92x10⁶℃ which is slightly higher than that of the commercials. The thermal shock resistance tested at 1200℃ for 5 cycles, showed that the strength was reduced by 30.26% which rather similar to commercial as 0.55±0.01 MPa owing to the lacking of mullite phase which support the strength of ceramic materials, as found in commercial insulating bricks. The main phases composition in specimen were corundum and anorthite.