Study On The Mineralizing Effect Of Rare Earth Elements On The Sintering Of Cement Clinker And Application Of Its Tailings In Cement Production

The investigation is based on the characteristic rare earth elememts minerals (i.e. ion absorptive rare earth ores ) of Jiangxi province. Owing to high abundance of Ce,Y,La, Nd in the REE ores of south China, the study focuses on these four REEs oxides. Their mineralizing effect on the sintering of cement clinker is discussed. And the tailings of ion absorptive REE ore in the south of Jiangxi Province are used as a substitute for clay in preparation of cement raw meal. Its influence upon the minerals formation and performance of Portland cement clinker is studied.By means of up to date techniques such as DTA, ICP-AES , X-Ray diffraction, optical microscopy , SEM and traditional method (chemical analysis), the study is made on the the properties of raw materials,the effect of REEs oxides and rare earth tailing on the decomposition of carbonate and sinterability of the raw meal, the mineral morphology and composition of cement clinker,and mechanical properties of cement. The results show that REEs oxide have little effect on the decomposition of carbonate and they improve the sinterability of the raw meal;they also promote the formation of alite and growth of clinker minerals,and have beneficial effect on the uniformity of crystal size and well-distributed minerals. But some REEs result in the corrosion of alite when they are excessive,which may influence the hydration reactivity of alite.When clinker is well sintered, REEs oxide and its tailing improve the strength of cement clinker, and have little effect on setting time of cement. The raw meals which consist of rare earth tailing have high amount of arenaceous quartz, sinterability of the them are inferior to the sample which no rare earth tailing is added into accordingly. With improved grinding fineness of the raw material ,sinterability of the these samples will be better, thus this kind of rare earth tailing could be utilized as a substitute for clay to yield Portland cement clinker with high performance.By using the method of SEM-EDS,the distribution of REEs oxide in cement clinker is determined. Combined with mineral morphology of cement clinker, preliminary research on mechanism of promotion of REEs on the sintering of cement clinker is made. The results show that in the sintering process of clinker more La and Ce are distributed in the silicate phase, which form into solid solution with it ; The dopping effects of La and Ce induce the aberrance of stress field of diffusive medium, which decrease the activation energy of particles diffusing, and accelerate particles diffusing during the solid state reaction. It makes the solid state reaction speedy and the amount of solid solutions more formed in alite, thus improves the performance of cement clinker.