Microstructure and Properties of Carbon Block Refractories Containing Thermally Oxidized Anthracite for Blast Furnaces

Carbon block refractories containing thermally oxidized anthracite (TOA) and additives of Al and Si were prepared for use in blast furnaces. The TOA was obtained by treating electrically calcined anthracite (ECA) using the thermal oxidation method. It was then introduced into carbon blocks by partially or totally replacing the ECA raw materials. The microstructure and properties of carbon block refractories heated in a coke bed at 1400 degrees C were investigated. The results revealed that TOA accelerated the formation of beta-SiC whiskers and beta-Sialon phases in carbon block refractories because TOA has higher reactivity than ECA. Properties such as the cold compressive strength, mean pore diameter, <1 mu m pore volume ratio and thermal conductivity of carbon block refractories with TOA were improved remarkably compared with those without TOA. It was suggested that the in-situ-formed ceramic phases in the matrix and on the aggregates both had a strengthening effect on the carbon block refractories. Moreover, the whiskers formed in the matrix were more favorable for forming an excellent microporosity structure as they filled the pores while the whiskers on the aggregates were more beneficial for reducing the interface thermal resistance between the aggregates and matrix, thus promoting the thermal conductivity of the carbon block refractories.