Development And Application Of Magnesia-chrome Brick For Dry-process Cement Rotary Kiln

This paper describes the influence of production condition of the dry-process cement rotary kiln on the service life of the magnesia-chrome brick. The raw materials and the production process of magnesia-chrome brick for cement kiln were optimized. A high quality direct-bonded magnesia-chrome brick LZMGe-8A for the large-size dry-process cement rotary kiln was developed in order to substitute the imported products. The wear mechanism of the magnesia-chrome brick LZMGe-8A was investigated by the analysis of the microstructure, the measurement of chemical and physical properties of the used bricks, and the simulated thermal shock & corrosion tests.The optimization of the raw materials and the production process indicate that a high-quality magnesia-chrome brick with excellent performance and good microstructure can be produced by selecting the synthesized materials with the perfect grain size distribution which has higher C/S and K/(A+F) ratios and lower content of CaO and SiO₂, by adding grain sized chrome ore and additives, and by means of high pressure press and perfect sintering temperature pattern. The products were used for the lining around the firing zone of the dry-process cement rotary kiln of Huaxin Cooperation which has the production of 5000t/d and lasted more than one year, achieving a service life longer than that created by the imported products with the highest level in the world. So this product has subsitituted the imported one to be used for the lining around the firing zone of the dry-process cement rotary kiln.The research on the damage mechanism of the brick shows that the peeling resulted from the brittle structure of the brick could be attributed to caustic mass from the compounds of potassium, sodium, sulphur, chlorine in cement raw materials and fuels which infiltrated into the pores in the bricks in the form of vapor and liquid and transformed alternatively from liquid to solid or from solid to liquid while the temperature waved. The penetration of the liquid phase from the cement clinker could result in structure spalling on the hot face of the brick. It is the co-action of thermal shock and the caustic mass that brings forth the damage of magnesia-chrome bricks. And therefore it is an important measure to reduce the damage on the direct bonded magnesia-chrome bricks to lower the porosity and promote the thermal shock resistance of the bricks.