Kaolin refractories for the lining of the iron notch of a 5000-m3 blast furnace

Abstract

The formation of the black core in large kaolin bricks during the firing process is caused mainly by the reducing medium which develops in the central part of these high-density refractories, graphitizes the carbon, and converts some of the high-valence iron and titanium oxides to low-valence oxides. The principal sources of the reducing medium inside the brick are the spent sulfite liquor and the sulfur- and carbon-containing impurities of the starting material. The likelihood of a black core being formed increases with the density of the green product and the rate at which the kiln temperature is raised. The properties of the light-colored outer and black inner zones are dissimilar so that cracks are formed during heating and cooling. In a joint project with the Zaporozhe Refractories Plant the Ukrainian Scientific-Research Institute for Refractories developed a method of producing high-density kaolin brick without black core. The method was used to produce about 200 tons of bricks measuring 345×150×150 mm and 230×150 ×150 mm for the lining of the iron notches of the 5000-m3 No. 9 blast furnace of the Krivoi Rog Metallurgical Plant.