Abstract

Zirconia-added magnesia-spinel bricks composed mainly of magnesia (MgO) and spinel (MgO・Al2O3) are extensively used in burning zone of cement rotary kilns because they have good coating adhesion and high corrosion resistance to the clinker melt while maintaining their high spalling resistance. Recently, however, the wear of the bricks has increased due to unstable coating conditions arising from the increasing use of waste as fuels and raw materials in the cement burning process. In this paper we present zirconia-added magnesia-spinel brick with high resistance to both corrosion and spalling as well as good coating adhesion under severe conditions. It contains approximately 90% MgO, featuring high corrosion resistance. Although magnesia-spinel bricks with less content of spinel have generally less spalling resistance, putting different types of spinel with proper size has enabled the brick to possess the trade-off properties. Moreover, adding minor amounts of two types of raw materials to the brick has made it possible to improve the coating adhesion properties and infiltration resistance to the cement constituents. The developed brick by such techniques also exhibited higher corrosion resistance than the brick without zirconia addition in a rotary slag test. The reason for these improved properties is that the brick has an enhanced bonding in the matrix and dense microstructure as well as high refractoriness compounds of calcium zirconate, leading to reduction of the cement infiltration. The developed brick was installed at the burning zone where the linings are exposed to harsh environment caused by the utilization of large amounts of waste. It demonstrated superior performance to our competitor’s brick and has been highly valued by our clients.