Clinker grindability

The subject of clinker grindability also has microscopical aspects and the most complete literature survey, to date, is that of Hills (1995) who enumerated most of the prevailing agreed-upon relations (such as decreasing alite crystal size increasing grindability). Other variables on which the interpretations were not as clear cut (such as percent liquid phase) were also listed. 

Kawamura, S. and others, "The Estimation of Clinker Grindability by Microscopy (Ono Method)," Reviews, 36th General Meeting, Cement Association... 

Scheubel, B., "Microscopic Examination of Cement Clinker Using the Linear Traverse Technique for Determination of Clinker Grindability," Zement-Kalk-Gips, Vol. 36, No. 11,1983, pp. 624-627. 

Theisen, K., "Estimation of Cement Clinker Grindability," Proceedings of the 15th International Conference on Cement Microscopy, International Ce-mentMicroscopyAssociation,Dallas,Texas,1993, pp. 1-14. 

The charge levels on 9 and 10 Mills were also increased during the installation of the classifier in accordance with Sturtevant s recommendations, as part of the conversion to closed cireuit. The variation in clinker grindability is also a significant factor, as other mill throughputs were low in November and December, and improved again at the beginning of the year. 

Maximum production was attained with maximum air flow through the separator. The new system is still susceptible to changes in clinker grindability, but not as markedly as it was on open circuit. 

The measured true density of clinker is typically 3150-3200 kg m the value calculated from the X-ray densities and typical proportions of the individual phases is about 3200kgm" The difference is probably due mainly to the presence of pores inaccessible to the fluids used in the experimental determination. Using mercury porosimetry. Butt et al. (B35) determined pore size distributions and discussed their relations with burning and cooling conditions and grindability. 

The other question deals with the coimnon or separate grinding of slag and clinker. As a matter of fact the fineness of every component of binder is important, because at cotmnon grinding slag, as having lower grindability, will be always collected in a coarser fraction... 

Tachihata, Kotani, andjyo (1981), in a laboratory study of the relationships between rate of heating, raw meal fineness, and other factors, concluded that clinkers with large crystal sizes in a narrow size range showed unfavorable grindability, and that cracks within the crystals and atthe boundaries were some of the most important factors in grindability. 

Grindability of quickly cooled clinker is good. Amber belite is ground at the last stage. J.M. Butt (1974) stated that good grindability of quickly cooled clinker is due to plenty of micropores in the interstitial phase. 

Large belite nests were shown to be indicative of poor grindability, even though the same clinker may have relatively high porosity. Clusters of belite crystals remained undivided even at the final grinding stage. 

Personal correspondence from Ono (1979) listed some of his preliminary conclusions relating grindability, burning conditions, and clinker microstructure ... 

Scheubel (1988) found that the alite chord length could be used to construct a cumulative crystal size curve, the data from which were used to evaluate heating rates and retention times in various kiln systems. High-quality clinkers were said to have uniform granulometry, small silicate crystals, and easy grindability. 

Dusty clinker, coarsely crystalline silicates, low-porosity nodules, poor grindability Slow temperature rise, higher clinkering temperature, longer time in burning zone and transition zone (Wolter, 1985)... 

Hills, L.M., The Effect of Clinker Microstructure on Grindability, RP331, Portland Cement Association, Skokie, Illinois, 1995,124 pp. 

Ono, Y., "Microscopical Observation of Clinker for the Estimation of Burning Condition, Grindability, and Hydraulic Activity," Proceedings of the Third International Conference on Cement Microscopy, International CementMicroscopyAssociation,Hous-ton, Texas, 1981, pp. 198-210. 

Petersen, I.F., "The Pore Structure and the Grindability of Clinkers," Ciments, Betons, Platres, Chaux, No. 726,1980, pp. 297-301. 

Sansoni, G., and Zybell, H., "Grindability Tests with Portland Cement Clinkers. Preparation and Microscopic Testing of Clinkers," Silikattechnik, Vol. 25, 1974, pp. 87-93 (in German). 

Tachihata, S. Kotani, H. and Jyo, Y., "Study on the Grindability of Clinker," Reviews, 35th General Meeting of the Cement Association of Japan, 1981, pp. 33-35. 

Raw meals for high-belite chnkers are relatively easy to bum, and the consumption of energy is reduced, mainly because of a reduced CaCOj content. Compared with ordinary Portland cement clinkers, it is possible to reduce the binning temperature by up to about 100 °C and along with it the NO emission. At the same time the grindability of the clinker is improved (Ludwig and Pohlman, 1986). 

The various constituents of Portland clinker differ in their grindability. In general, the grindability declines in the order calcimn sulfate>alite> almninate>ferrite>belite. As a consequence, different cement particle size fractions may vary in their phase composition. 

To obtain sulfobelite cement the clinker that is produced must be ground to a specific surface area similar to that of ordinary Portland cement. Gypsum or anhydrite must be added only if the amount of anhydrite in the clinker is insufficient. The grindability of sulfobelitic clinkers is better than that of typical Portland cement clinkers. 

In clinker grinding, the gypsum, being more readily grindable, tends to be concentrated in the finer particle size fractions of the product. So does any fly-ash that may be added, whereas blastfurnace slag becomes concentrated in the coarser fractions. 

The soundness, chemical resistance and strength of the cement, as well as the grindability of the clinker, are affected by the rate of cooling applied to the clinker. 

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