Research On MgO-CaO-ZrO₂ Brick For Precalciner Kiln

Because of the rapid development of the world economy, cement industry have been made great progress since 1950's. With the development of new precalcined technique and bigger size of cement kiln, the refractory for rotary cement kilns have to bear more and more influences of thermal load, mechanical stress, chemical corrosion.At the end of 1970, the Magnesia-chromite brick is eliminated gradually in the developed countries due to the demand of environment protection, subsequently, the dolomite brick, the Magnesia-spinel brick and MgO-CaO-ZrO₂ brick appeared gradually. The Dolomite brick has the stability of chemistry and appetency, which result in the superior coating adherence and corrosion resistance to cement raw meal. It also has the disadvantages of hydration and bad thermal-shock resistance. Spinel brick has the good thermal-shock resistance, however it have the disadvantages of the bad coating adherence and high heat-conducting rate.The MgO-CaO-ZrO₂ brick are perfect refractory for cement kilns at high temperature because they have good corrosion resistance, excellent thermal-shock resistance, and good coating adherence. The research of the MgO-CaO-ZrO₂ brick abroad is on the basis of the high pure raw materials and the high cost, so it is difficult to be used widely in China.In this research, 95 moderate pure magnesia clinker, 97 high pure magnesia, 96 fused magnesia clinker, lightweight limestone, Desilicated zirconia, Calcium zirconate, and a little additive be made full use to produce the materials composed of MgO,CaO.ZrO₂,2CaO.SiO₂ 3CaO.SiO₂ on the basis of pre-experimental data. The materials sintered in 98.5m high temperature kiln are prepared by necessary craft measures. By testing the sample, we analyze the effects of chemical compositions, additive, and sintered temperature on sample performances. The experimental results show that by the reasonable blending of raw materials and craft measures, MgO-CaO-ZrO2 materials with good performance can be prepared. When CaO/SiO₂≥1.87+0.455ZrO₂/ SiO₂(quality ratio), the phase with high melting point appears and the properties of the materials at high temperature are better. In order to make theappearance of the product fulfill the request, the raw materials content withcalcium carbonate is no more than 12Wt%.In order to attain good performance, sintered temperature is more than 1680 °C. The refractory with environmental protection have more thermal-shock resistance than Magnesia-chromite brick bonded directly. It has also higher temperature of refractoriness under load and good coating adherence. The research provides a feasible technical route for the refractory free chrome for rotary cement kilns in our country.