Bauxite from Qingzhen is calcined for refractories applications. Three fuel sources with different amounts of residual ash and ferric oxide were used for bauxite calcination in a rotary kiln. It is found the quality,including the content of ferric oxide,bulk density,apparent porosity and water absorption,of the bauxite is highly influenced by the fuel source of rotary kiln. In essence,the effect of fuel on the quality of bauxite is attributed to the amount of ferric oxide introduced by the fuel. Introduction of a modest quantity of ferric oxide is beneficial for promoting the densification of bauxite.
In-situ magnesia-rich spinel fiber was formed resulting from the addition of ferrocene into MgO-C refractory matrixes. The formation of in-situ spinel fiber was detected to start at 1300 ℃. The amount, diameter and length of the fibers increased with rising temperature. Ferrocene may have catalytic effects on the growth of the fibers in two aspects. First, the reaction between MgO and C and the decomposition of Al4C3 may be catalyzed at high temperature. Suitable concentration gaseous phase is then created for vapor-vapor reaction which could result in the in-situ formation of fibers. Second, Fe nanoparticle produced from ferrocene can act as catalytic droplets and catalyze the growth of the fibers. The fibers are formed via the vapor-liquid-solid and vapor-solid mechanisms. In terms of chemical thermodynamics, the partial pressure of CO and Mg(g) are found to play an important role in the in-situ fibers formation. Different concentration of vapors affects the size, amount and composition of the fibers at different temperatures. The mechanical properties of MgO-C brick was found to be improved by ferrocene addition.
