Preparation Of Periclase-spinel-calcium Aluminate Refractories For Cement Rotary Kilns

With the formulation of carbon peaks and carbon neutrality,the refractory kiln linings used in traditional cement rotary kilns can’t meet the requirements of energy savings and emission reduction.The transition zone of the cement rotary kiln has high surface temperatures and high heat loss due to the difficulty of coating and the high thermal conductivity of the refractory used.Lightweight refractories not only have a low thermal conductivity,their corrosion resistance,room temperature physical properties,and high temperature performance are not worse than those of dense refractories,while lowering pollutants and conserving energy.In this paper,sintered magnesia,corundum,magnesia-alumina spinel,and cement materials were firstly held at 1350°C for 1h and 6h,respectively,and the corrosion resistance of magnesia-alumina refractory raw materials to cement materials was investigated using scanning electron microscopy(SEM),X-ray diffractometry(XRD),and Factsage.The spinel-calcium aluminate multiphase lightweight aggregates were synthesized using magnesite,dolomite,and industrial alumina as raw materials.With this as a particle,spinelpericlase-calcium aluminate refractories were prepared using sintered magnesia powder as the matrix.Following an investigation into how the phase composition of the synthetic raw material affected its physical characteristics at room temperature,refractoriness under load,and corrosion resistance to cement materials,the following conclusions were drawn:(1)In the cement rotary kiln at 1350°C,magnesia,corundum,and magnesia alumina spinel particles as the raw materials of magnesia-aluminum refractories,reacted with silicate cement materials for 1 h and 6 h,respectively.Among them,with the increase of time the intergranular corrosion layer of magnesia particles becomes thicker,magnesia particles react with cement materials to produce a small amount of liquid phase at high temperature,so its corrosion resistance to cement materials is the best.The corundum particles react with the cement material to produce a reaction overlayer that protects it to a certain extent and therefore has better corrosion resistance.Spinel particles and cement materials generate more liquid phase at high temperatures,and the viscosity is low.The high-temperature liquid phase intrudes into the spinel particles through the grain boundary.Therefore,the corrosion resistance of cement materials is poor.(2)Spinel-aluminate multiphase materials with low water absorption can be synthesized using magnesite,dolomite,and industrial alumina as raw materials by solid-phase reaction sintering method at 1650°C for 4 h that can be used as light-weight refractory aggregates.Meanwhile,using magnesite,calcium carbonate,and industrial alumina as raw materials Ca2Mg2Al28O46 was synthesized at 1750 °C for 4 h with high water absorption and low room temperature compressive strength,but it can significantly improve the lightweight of refractory materials.(3)Spinel-periclase-calcium aluminate refractories with high room temperature compressive strength can be prepared using synthesized spinel-calcium aluminate multiphase materials as aggregates.The high strength is due to the good bond between the synthesized lightweight aggregates and the periclase matrix.(4)The periclase-spinel-calcium aluminate refractory has excellent corrosion resistance to cement materials and a sufficiently high refractoriness under load,so it can be used in the transition zone of a cement rotary kiln.