HYBRID SPINELS TECHNOLOGY FOR BASIC BRICKS IN CHEMICALLY HIGHLY LOADED CEMENT ROTARY KILNS

摘要

For brittleness reduction in basic bricks for cement rotary kilns different flexibilising agents are used. For the application in cement rotary kilns, minerals from the spinel group AB_2X_4 are mainly used. State of the art are magnesia-alumina-spinel (spinel, MgAl_2O_4), iron-alumina-spinel (hercynite, FeAl_2O_4) and manganese-alumina-spinel (galaxite, MnAl_2O_4). Due to the high use of secondary fuels, , the refractory material in cement rotary kilns is increasingly contaminated by volatile compounds like K_2O, SO_3 and Cl. This causes a densification of the brick's micro structure and even spallings of hot face brick parts. Since this chemical attack generally leads to a shorter service life of the refractory material, it was the target to develop brands with an outstanding thermo-mechanical behavior even under strong densification by alkali salts. At tests of Young's Modulus by ultrasonics bricks with spinel and hercynite showed quite diverging characteristics. Based on these trials it was possible to develop bricks with hybrid spinels technology, which did not only show excellent thermo-mechanical properties but also an outstanding performance in chemically highly loaded cement rotary kilns.