Abstract

Waste melting furnaces play a vital role in Japan because they make it possible to incinerate and melt industrial and household wastes at high temperatures, contributing to solution of landfill shortage problems and establishment of resource recycling society. Waste melting furnaces are classified depending on the type of waste and disposal process and the properties required for the refractory lining vary according to the furnaces. Since refractory lining is exposed to intensive corrosive conditions at high temperatures, alumina-chromia brick is typically applied in waste melting furnaces. For alumina-chromia brick used in rotary type waste melting furnaces, it is necessary to have both corrosion resistance to molten slag and spalling resistance to mechanical stress during rotation and thermal shock. In general, the higher the content of chromia in alumina-chromia brick, the weaker the spalling resistance. In order to achieve a longer lifetime of the brick in actual kilns, it needs to contain a smaller amount of chromia but have high corrosion resistance.

In this study, we investigated the relationship between chromia content in the matrix of alumina-chromia brick and the corrosion index from the rotary drum corrosion test. The test results demonstrated that the corrosion resistance was improved with increasing matrix chromia content. In the test samples, a reaction zone consisting of iron oxide, alumina and chromia was observed at the brick-slag boundary. The microstructure observation revealed that brick with higher matrix chromia content has a wider reaction zone with well densified structure, leading to enhancing corrosion resistance. Employing this technique enabled us to develop the alumina-chromia brick with both high corrosion and spalling resistance.