Influence of flexibilisers on basic cement rotary kiln brick properties

The paper analyzes the factors that determine the effectiveness of impact modifiers - elasticizer additives introduced into the basic refractory materials for lining high-temperature zones of cement rotary kilns. These include, above all, the differences in temperature expansion coefficients of the impact modifier and magnesium oxide, and the grain size of the former. As a result of the tests, it was found that the best mechanical properties of refractories based on MgO, containing spinel structured additives, are with hercynite FeO · Al2O3. Also the effect of thermo-chemical loads on the loss of function by the refractories operating at high temperatures was studied.
As a result of 280 studies of used liners conducted in 2010-2015, it was shown that the most common wear factor of the basic bricks in cement rotary kilns is infiltration of alkali salts. Because of their impact the elasticizer has only a very limited effect on the character of corrosion.
The resistance to the clinker melt, determined by the total content of oxides in the refractory which may ingress into the melt, is also important. Since the hercynite additive provides the required physical and mechanical properties of the refractory at a lower content in comparison with other elastifying additives, the total amount of such oxides in the material is also less. On the whole, the studies have shown that the most effective elastifying additive is hercynite. This result is confirmed by a number of tests carried out over more than 20 years.

Author: M. Geith, R. Krischanitz, S. Joerg

Section: Refractories

Keywords: basic refractory material, flexibiliser, spinel, hercynite, thermal expansion, Young’s modulus