Coarse quartz

For imaging XPS, this process was carried out on a kaolinite and coarse quartz (above 20 nm stokes radius) 1 1 mix. 

Percent by weight in each size Coarse quartz Fine quartz... 

Detailed studies on the effect of surface-area and heat of wetting are not available. However, it is known that the heat of wetting of silica gel, which is a highly porous material, is approximately 30 cal per g (approximately 200 times that of coarse quartz as shown in Table 46). 

For the Si02-H20 system the possibility of impurity contents being the determining factor has been eliminated (21). It was also shown (II, 22) that the Avariation with specific area can be generated from an initially coarse quartz powder by extensive grinding and subsequent fractionation into a series of particle size samples. The various AH0 s obtained from AH/s (see Equation 1) for Si02 samples outgassed at 160° C. and 10 6 mm. of Hg are listed in Table I. 

A typical sequence of reactions may be demonstrated on the most widely utilized system Na2C03 — CaCO —S1O2 (soda-limestone-quartz). Silica is introduced as a relatively coarse quartz sand and on heating it undergoes modification inversions which are not substantial for the melting process. It is not volatile and melts only at 1726 C. CaC03 begins to decompose perceptibly from about 600 C upwards and the dissociation pressure reaches atmospheric pressure at 898 C. The rate of... 

As Table 7-16 shows, the relative abundances of the major elements in the aerosol do not differ greatly from those in bulk soil, crustal rock, or average shale—that is, the elements are neither greatly enriched nor seriously depleted. A good match with any of the three reference materials is not obtained, however. The differences must be significant, since they are greater than conceivable analytical errors. Consider silicon as an example. Tables 7-13 and 7-16 indicate an average Si/Al ratio of 2.7, which is lower than that for either bulk soil or crustal rock and is more similar to that in shales. Fly ash exhibits a particularly low Si/Al ratio. It is possible that the low aerosol value in heavily industrialized Tees-side (Table 7-13) is due to a mixture of natural and combustion aerosols, but this explanation cannot be extended to the remote continental aerosol. A more likely explanation for the silicon deficiency is the size distribution of the Si/Al ratio in soil particles. The very coarse quartz particles, which are rich in silicon, are not readily mobilized. Since only the fine fraction of soil particles contributes to aerosol formation, the Si/Al ratio in the aerosol will be determined by that of silts and clays (see Table 7-7 for definitions). Common clay... 

Naito and Ono in 1953 reported the relationships between three size fractions of raw feed (greater than 30 pm, 20 to 30 pm, and 10 to 20 pm) and their burnabilities, concluding that (1) coarse quartz increased the difficulty of burning and (2) a few percent alkalies and magnesia as mineralizers greatly improved sintering. Microscopically it was shown that... 

Poorly burned clinker frequently contains many small belite clusters. If the raw mix contains coarse quartz grains, belite clusters appear even in well-burned clinker, and the alite size has a wide range. 

Dusty clinker (poor nodulization) and snowmen (a) Unfavorable temperature distribution (b) Too little melt (c) Too much coarse quartz, lime, slag (d) Heavy alkali circulation resulting in early crystal growth of belite and free lime and large silicate crystal size (Miller, 1980)... 

Photograph 7-11 Extremely heterogeneous clinker containing large concentrations of loosely packed yellow-amber belite and alite with a wide range of crystal sizes and, like the belite, a nonuniform distribution. Free lime is abundant (dark, round crystals). Sandy, silica-rich raw feed with coarse quartz. Gas-fired dry-process kiln, 3000 tons/day. (S A6631)... 

Large alite Long flame, slow heating rate (Ono, 1981) coarse limestone or calcite in feed (Akatsu and Monna, 1966) coarse quartz (Ono, 1954) long thickening time in oil-well cements (Reeves, Bailey, and McNabb, 1984)... 

Increasing size of alite Coarse rawfeed, coarse quartz, increase in firing temperature, decrease in strength (Long, 1983)... 

Coarsely crystalline alite surrounded by finer-grained alite and free lime Coarse quartz and locally high lime saturation factor converting previous beiite nest to alite (Miller, 1980)... 

Pore-oentered belite nests with relatively large, densely paoked crystals, producing large alite at higher temperature if lime is available Coarse quartz in feed (Long, 1982a)... 

Tight belite crystals in nests with sparse liquid phase Coarse quartz (Miller, 1981 Gille and others, 1965)... 

Large patches of belite belite nests from coarse quartz Selective reaction of raw mix components clay at lower temperature than that for quartz, muscovite, hornblende, and Ca-feldspars resulting in early nodulation (micronodules) and clinker dust with high lime saturation factor (Fundal, 1980)... 

Relatively large belite inclusions in elite, large belite crystals (45 pm) Abundance of coarse quartz in feed belite and alite became much smaller upon use of finely ground friable silica (Dorn, 1980)... 

Yellow nested belite Coarse quartz, lack of lime diffusion into nest (Dorn, 1985)... 

Photograph 7-34 Belite crystals comprising sharply delineated nest around pore (black), probably the site of a coarse quartz grain in the feed. Coal- and coke-fired, dry-process kiln. (S A6654)... 

Photograph 7-35 Clear belite ring around central pore formed by silica mobilization during sintering of coarse quartz in feed. (S A6655)... 

Photograph 7-37 Bimodal belite in laboratory-burned clinker made from a raw feed containing coarse quartz sand. Large nest of tightly packed belite crystals and much smaller crystals showing wide lamellae. Note gradational color response in nital etch of nest. 55% of the alite crystals were said to be greater than 75 pm. 

With the use of Ono s Method and microscopy of raw feed, clinker, cement, gypsum, and kiln dust, coupled with laboratory burns and sieve analysis of the raw feed, Vanisko (1978) demonstrated the deleterious effect of belite nests in development of mortar strength. He showed that coarse quartz was correlated with numerous large belite nests and, when the raw sand was separately and more finely groimd, mortar strengths jumped to 41 MPa. 

Scheubel (1989) characterized the sintering processes of two raw materials, one with silica distributed as clay minerals and the other with coarse quartz. With the former material, the reaction that forms the silicates in the short sintering zone with a steep temperature profile was said to be dependent primarily on the physical parameters of the melt (diffusion constant) and the mean path length for elemental migration. With the raw material containing coarse quartz and burned with a shallow temperature profile, coarsely crystalline belite which had formed... 

Centurione and Kihara (1994) tested the application of F.L. Smidth s burnability equations and methods, including those of Fundal (1979), Theisen (1992), and Miller (1980), in an analysis of 12 samples of raw feed and corresponding clinkers. Cenfurione and Kihara used an hydrochloric acid digestion mefhod fo calculate Cj25 and concluded that coarse quartz (>45 pm) and limestone (>125 pm) should not exceed 2% and 6%, respectively, by weight of sample. 

To illustrate the effects of excessive coarse quartz and other coarse siliceous materials, an extremely nonuniform clinker was made from microcrystalline limestone, a sand containing fragments of quartz and feldspar-rich volcanic rocks, and other rocks and minerals. IR, (.g = 7.6%, = 2.1%, and "F " (feldspar... 

Dorn, J.D., "The Influence of Coarse Quartz on the Raw and Finish Products of a Modern Cement Plant," presented at the American Ceramic Society Pacific Coast Regional Meeting, San Francisco, California, October 26-29, 1980. 

Dorn, J.D., "The Influence of Coarse Quartz in Kiln Feed on the Quality of Clinker and Cement," Proceedings ofthe Seventh International Conference on Cement Microscopy, International Cement Microscopy Association, Ft. Worth, Texas, 1985, pp. 10-23. 

Sas, Laszlo, 1997, "Effect of Coarse Quartz and Limestone Grains on the Properties of Raw Meal, Clinker and Cement," Proceedings of the 10th International Congress on the Chemistry of Cement, Gothenburg, Sweden, Vol. 1, Paper 11048,8 pp. 

With this the main object of the clinkering process, i.e., the formation of the valuable compound C3S, has been achieved, and it is this that requires and justifies the effort and cost of heating the raw materials to the high clinkering temperature, in addition, the liquid phase promotes other reactions, e.g., involving relatively coarse quartz or limestone particles. 

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