1156 posts
Burning Question 63
What in your opinion would be the effect, on clinker properties (reactivity, granulometry, hardness...) of having a high LSF (97-98) and silica module(SM) of 2.8 and a low alumina module (AM) around 1.3-1.4? Would the high LSF tend to rise the C3S content, improving early strengths? High MS would shift the relationship C3S/C2S towards more C3S? also improving later strengths...if so, doing the opposite would rise the C2S and also the late strengths...but lowering the early ones?
What about granulometry? We have seen that low AM, but lower LSF and SM gives a better granulometry and a darker clinker ... would you think that it will be the same under the conditions cited before (high LSF and high SM)? We produce a pozzolanic cement (20 per cent substitution) and would like to improve our late strengths. I believe it can only be done by working on the clinker, besides improving all the milling conditions, like Blaine and fineness, mill fill, gas flow, etc ... Please let me know your opinion.
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1156 posts
Re: Burning
High LSF will certainly increase the C3S content and the early strength of your cement. The high SM will increase the total silicates rather than specifically the C3S, and strengths at all ages. If you reduce the SM you can expect strengths to go down. The darker colour with low AM arises because of the increase in the C4AF content at the expense of the C3A and will apply at the high LSF and SM, although colour will lighten as the SM rises due to less total flux (C4AF and C3A). In terms of granulometry the effects are more difficult to predict and depends of your definition of good granulometry. Lower AM and therefore higher C4AF may increase the size ofthe clinker nodules due to earlier liquid formation in the kiln, however, C3A can be a more effective flux than C4AF due to the higher relative volume compared to C4AF.
I certainly agree that improving clinker quality and mineralogy is the key to strength enhancement and control in all types of blended cement, including pozzolanic cements. Please look for an article in the February 2003 issue of International Cement Review which talks about this topic as implemented at the Ladce factory of Cementaren Povazska in Slovakia.
1156 posts
1156 posts
Re: Burning
No, there is no precise formula for the relationship between kiln speed and feed rate. This depends on the degree of preparation (calcination) of thefeed at the kiln inlet and the progression of this feed preparation along the kiln length. However, there are "rules of thumb" and guidelines you can use for various kiln process types. What type of kiln are you operating?