Preparation Of MgO-CaZrO₃-Ca₂SiO₄ Materials And Their Corrosion Resistance To Cement Clinker

The natural dolomite and zircon are used as raw materials,and the ratio of mixture is designed according to the final phase of MgO-CaZrO₃-Ca₂SiO₄ material.The reaction course of dolomite and zircon in this composition,the effect of dolomite pretreatment and mechanical activation on the sintering properties,and the influence of additive type and addition amount on the structural stability of MgO-CaZrO₃-Ca₂SiO₄ material were studied.Finally the corrosion resistance of the MgO-CaZrO₃-Ca₂SiO₄ material in this experiment to cement clinker was studied.The following conclusions were obtained:?1?The reaction process of dolomite and zircon was studied.Under the condition of zircon's existence,the decomposition of dolomite changes from two steps into one step.And the CaO and MgO formed by decomposition cause a greatly decrease about temperature of zircon decomposition.The decomposed ZrO₂ preferentially reacts with CaO to form CaZrO₃.The larger CaO/SiO₂ ratio promotes the conversion of the intermediate phase of magnesium calcium silicate to Ca₂SiO₄.?2?The reaction of calcined dolomite and digested light burned dolomite with zircon can effectively improve the reaction sintering performance of MgO-CaZrO₃-Ca₂SiO₄ materials.After sintering at 1600?,the MgO-CaO-ZrSiO₄ system mixture can prepare MgO-CaZrO₃-?-Ca₂SiO₄ material with a porosity of 9%,bulk density up to 3.30g/cm³ and a high degree of direct bonding;The MgO-CaZrO₃-?-Ca₂SiO₄ material prepared by the Mg?OH?₂-Ca?OH?₂-ZrSiO₄ system mixture has a porosity of 12%and a bulk density of 3.23g/cm³,which is slightly lower than the former.The sintering performance of the materials prepared by the two systems was significantly enhanced after mechanical activation.The material prepared by the MgO-CaO-ZrSiO₄ system mixture showed a porosity less than 1%and bulk density up to 3.60 g/cm³.The material prepared by Mg?OH?₂-Ca?OH?₂-ZrSiO₄ system has a porosity less than 2%and a bulk density of 3.45 g/cm³.?3?The reason for powdering of MgO-CaZrO₃-Ca₂SiO₄ materials and the effects of additives on the structural stability of the materials were investigated.The results shows that:during the reaction sintering of MgCa?CO₃?₂-ZrSiO₄ mixture,Ca₂SiO₄ would be created.In the process of cooling,Ca₂SiO₄ undergoes multiple phase transitions,in which the change from?-Ca₂SiO₄ to?-Ca₂SiO₄ at about 500°C is accompanied by a volume expansion of about 12%,resulting in cracking and powdering of the final material.Both adding Y₂O₃ and moderate La₂O₃,the powdering phenomenon disappeared after high temperature firing,but the materials added with BaO still pulverized.?4?The effects of calcium-silicon ratio and different additives on the corrosion resistance of MgO-CaZrO₃-Ca₂SiO₄ materials to cement clinker were investigated.As the ratio of CaO/SiO₂ increased,the penetration area of the refractory first increased and then decreased.When the molar ratio of CaO/SiO₂ is 4:1,the corrosion ratio of the material was the smallest,about 23.2%.After adding 1wt.%Y₂O₃ and La₂O₃ respectively,the corrosion area of the materials were reduced.The material with molar ratio of CaO/SiO₂ of 4:1 and 1wt.%Y₂O₃addition showed the smallest corrosion area,about 14.86%.From the viewpoint of microstructure,the MgO particles in the material with a molar ratio of CaO/SiO₂ of 3.5 and1wt.%Y₂O₃ addition were moderately combined to form a dense protective layer,which was the best in resisting the corrosion resistance to cement clinker.