Fused spheroids

StUl another ore preparation is the nodulizing process where the ore is heated in a rotary kiln to incipient fusion. The tumbling action in the kiln causes the phosphate ore to cohere and form spheroidal agglomerates. Combustion of carbon monoxide from the furnaces is used along with supplemental fuel to supply heat to 1300—1500°C. A boring bar is used near the kiln discharge to aid in breaking up the fused ore. The material is then cooled, cmshed, and screened to the appropriate size for furnace feed. 

The chondrules contained in the chondrites contain olivine, pyroxene, plagiok-lase, troilite and nickel-iron they can make up 40-90% of the chondrites. Chondrules are silicate spheroids, fused drops from the primeval solar nebula. Because of their differing constitution, chondrites are further subdivided one group in particular is important for the question of the origin of life, and has thus been intensively studied—that of the carbonaceous chondrites. 

When one thinks in terms of the many fused-ring isomers with unsatisfied valences at the edges that would naturally arise from a graphite fragmentation, this result seems impossible there is not much to choose between such isomers in terms of stability. If one tries to shift to a tetrahedral diamond structure, the entire surface of the cluster will be covered with unsatisfied valences. Thus a search was made for some other plausible structure which would satisfy all sp valences. Only a spheroidal structure appears likely to satisfy this criterion, and thus Buckminster Fuller s studies were consulted (see, for example, ref. 7). An unusually beautiful (and probably unique) choice is the truncated icosahedron depicted in Fig. 1. As mentioned above, all valences are satisfied with this structure, and the molecule appears to be aromatic. The structure has the symmetry of the icosahedral group. The inner and outer surfaces are covered with a sea of v electrons. The diameter of this C o molecule is 7 A, providing an inner cavity which appears to be capable of holding a variety of atoms. ... 

The composition of CCP containedthe following phases Ti, TiOj (rutile), TiN (see Table 5.4). There were no other phases of titanium oxides except Ti02 (rutile). In accordance with SEM, the CCP of pTi consisted of fused aggregates (Figure 5.21c) formed from the melt, while the initial Ti particles were spheroidal. 

The carbon black structure describes the pattern of how the primary particles are fused together into aggregates. Carbon black aggregates can vary in shape from individual spheroidal particles to more clustered and fibrous aggregate types. Figure 5.16 shows the highly structured aggregate of ENSACO 250. 

The intrinsic kinetics of reduction. The reduction rate was measured by thermogravimetric analysis (TGA) under conditions of particle sizes of 0.034 mm-0.054mm, H2 flow of 175ml-min temperatures at 350°C, 375°C, 400°C, 475°C, and 500° C, respectively. The effect of diffusion has been eliminated at such particle size range. If the shape of catalyst is taken as spheroid, reduction of fused iron catalysts can be described by SCM. The intrinsic kinetics of reduction is expressed as in Eq. (5.45). 

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