Study On The Kinetics Of The Forming Process Of High Alite Content Cement Clinker

The performance of clinker could be improved remarkably by increasing the content of Alite in clinker. However, the formation of Alite is most difficult in all the clinker minerals, some problem will be caused with the increase of Alite. In this thesis, some researches were carried out about the kinetics of the forming process of minerals and the kinetics of crystallizing process of Alite in high Alite content cement clinkers. The concentration of ions in Alite and the morphology of Alite under different physical and chemical conditions were also studied in this dissertation. Clinkers with high content of Alite were manufactured in our lab and in two plants, and the physical properties of them were tested.The results showed that the burnability of clinker can be improved by reasonable parameters (such as fineness), doping foreign ions and appropriate raw meal properties. With a reasonable fineness, the smaller particle size is in favor of solution and diffusion, thus the apparent activation energy of Alite formation can be decreased. The temperature of liquid phase formation was reduced and the properties of liquid phase were improved by adding some ions and industrial slag into the raw meals. High quality clinkers can be produced by adjusting the chemical composition of raw meal, adopting a reasonable parameters and appropriate burning temperature during the manufacturing process in plants.The burnability of clinkers was improved remarkably by adopting a two-steps burning method, and the sintering temperature was decreased by more than 100℃with pioneers (main components are Belite, C3A and C4AF) burned at 1350℃(TC group). As for TC group, since most Alite formed at 1300℃, it could be concluded that the nucleation of Alite was prevalent. With the increase of temperature, Alite crystals grew quickly in the range of 1300℃to 1400℃and preferred to M1 form. But the rate of growth became slower with the decrease of supersaturation while the temperature exceeded 1400℃. And Alite preferred to M3 form with silicate zonation, especially at the border of a pioneer particle. According to the results, it can be basically made sure that the effect of liquid phase is stronger than the effect of"crystal seed"of C2S, and the corporate effect of them is better.The solid solubility of ions in Alite depends on the concentrations of ions in clinkers at a large extent. The mass fraction of Al,Fe,Mg,P fluctuated in a narrow range and the polymorphic form showed no obvious change according to the XRD patterns with the increase of silica modulus (SM). The solid solubility of Al increased and Fe decreased with the increase of alumina modulus (IM). The XRD patterns of Alite showed remarkable different while MgO existed in clinkers.As for the clinkers burned at different temperatures or different cooling conditions, the solid solubility of ions in Alite was different. The mass fractions of ions decreased while the quenching temperature decreased. With the increase of temperature, the solid solubility of Fe decreased. The XRD patterns of Alite extracted from clinkers burned at lower temperatures(1350℃) is similar to the typical patterns of R form Alite. The solid solubility of Al was higher in Alite burned at an oxidation environment while the solid solubility of Fe was higher in Alite burned at a reducing environment.The results of experiments on manufacture of clinker with high Alite content showed that the burnablity and the strengths of clinker were improved with F/P doped in the raw meals. Clinkers with an expectant photographic structure and higher strengths could be produced while steel making slag (SMS) or phosphorus making slag (PMS) was introduced into raw meals.We should pay more attention to the microstructure of clinker not just concentrate on the content of free lime (f-CaO) during the manufacturing process in a plant. The results of the twice industrial experiments basically met the goals of"two 70%"(the C3S content is about 70.0w% and the 28d'strength is about 70.0MPa). In a word, clinkers with high performance can be produced in a plant with a reasonable chemical composition, parameters of raw meal and an appropriate heating condition.