Effect Of High Sulfur Coal On Clinker Sintering And Microstructure Of Portland Cement

With the reduction of high-quality resource day by day, low-quality fuel will gradually be utilized in cement industry. Confined by production technological level of present cement, the range of coal adapted is relatively narrower. The New Dry Process cement enterprises in our country generally use low sulfur soft coal. But the reserve of high sulfur coal resources in our country is quite abundant. Therefore, if high sulfur coal could be utilized in cement industry, it's sure that will abate the complexion of scrambling for resources with other industries and reduce the costs of cement production. But the researches about the utilization of high sulfur coal in cement production are relatively scarce by far. Therefore, in this thesis, the effects of different kinds of high sulfur coals on clinker sintering and microstructure of Portland cement were studied by means of high temperature microscope (HTM), X-ray diffraction (XRD), SEM-DES, petrographic structure analysis and clinker chemical analysis, and the effects of MgO and R20 on high sulfur clinker sintering were studied too. The results can offer the foundation theoretical guidance for the use of high sulphur coal in New Dry Process cement industry.The results show that the sulfur in coal can reduce the formation temperature of clinker liquid, enhance the stabilization ofβ-C₂S and depress the pulverization of clinker, but it has unfavorable effects on burnability of raw mix at higher temperature(≥1300℃) and prevents the formation of C3S, leads to a decrease in the amount of C₃S in clinker and a increase in the amount of C₂S. On the other hand, the existence of sulfur promotes the crystal growth of Alite and Belite, and meliorates the petrographic structure of clinker. C₄A₃S forms below 1250℃, and C₃A could not be formed at the same time. But C₄A₃S decomposes above 1250℃, and C₃A appears after C₄A₃S decomposed. Cement raw material has good desulfurizaion effect at 1350℃and higher temperature, the sulfur remained in clinker mainly dissolves in interstitial phase and in C₂S.Great difference exists in the effect of various sulfur coals on clinker sinterning, which is due to the different sulfur content in coal. In this paper, it is found that there is little influence on clinker sinterning when sulfur content is below 4% in the coal, and high quality clinker can be obtained. But when sulfur content exceeds 5% in coal, the amount of C3S in clinker will obviously decrease, and the quality of clinker worsen.The existence of MgO can improve the bumability of high sulfur raw mix, accelerate C₃S formation and clinker burning, and meliorate the petrographic structure of clinker, mainly improve the crystal form and size of C₃S. And in a certain range, higher amount of MgO in clinker has more evident effect on reducing unfavorable influence of sulfur on clinker minerals formation. R₂O has weaker effect on meliorating high sulfur clinker sintering. And that, the existence of MgO and R₂O at the same time also has evident effect on reducing the harmful influence of sulfur on clinker sintering and petrographic structure. Especially when the amount of MgO is lower, there exists a certain amount of R₂O that has more evident effect on C₃S formation than MgO solely.