Spheroidal coal

Exposures in the Black Beauty mine, near the surface in the main slope, show normal unaltered coal of a high volatile C rank. That this has most probably been affected by the intrusion of the dike is evidenced by high concentrations of spheroidal coal or coal apples. Johnson (JO) has reported on spheroidal coal and concluded that development of these structures is related in this area to the igneous intrusions. Further into this mine the entire seam becomes altered to natural coke in rooms headed toward the dike. In these areas mining had to be terminated for this reason. Large areas are exposed,... 

Within the Black Beauty mine the spheroidal coal has a reflectance value of 0.75%. Reflectance of the coke described above is 2.86%. 

The major mechanism of generation of both the natural and anthropogenic StA is a pyrolysis in the gas- or condensed-phase of the carbon-containing material. The microphysical characteristics of the resulting StA depend on the specific nature of the source so, for instance, the particles produced by oil combustion have a coral-like structure and an effective spherical shape the pyrolysis of coal gives particles in the form of spheres, with a great amount of smaller, randomly oriented spheroids inside them [11]. 

Sintered deposits form at the furnace exit at lower gas temperatures and in zones subject to rapid changes in direction. The deposit is composed of spheroidal particles, <40p, bound together by a molten substance. In those cases where substantial quantities of coarse pyrites are liberated from the pulverized coal, the spheroids are nearly pure FeaOa, as shown in Figure 11. The matrix contained silica, alumina, iron, and potassium, and has an initial deformation temperature of 1832°C, as determined by differential thermal analysis. The heavier pure iron spheroids deposit as a result of inertial impact. The mineral source of the molten phase is most likely illite. 

Measurements of spheroidal carbonaceous particles made by Solovieva et al. (2002) in surface sediments of lakes on the same transects as those studied here corroborate a wider extent of particulate fallout around Vorkuta. This class of particle, which is an emission product of coal combustion, was present at sites 1.1 and 1.6 at higher concentrations than at any of the other remote sites examined in the study area (e.g. sites 3.2 and 2.2). 

Figure 4. SEM photograph of a spheroidal carbonaceous particle from (he combustion of coal, showing a convoluted surface texture, previously thought typical of oil combustion and used in fuel-type apportionment ofSCPs.

The nature of their formation and their porosity means that both oil and coal SCPs are never spherical. However, they do have some degree of sphericity to their morphology and for this reason they are termed spheroidal. IASs are spherical and come in a variety of colours from colourless through yellow, red, brown and black, depending on their elemental, and in particular iron, content. Therefore, the counting of black spheres and terming them SCPs (e.g., Larsen et al., 1996) may lead to further confusion as to the exact nature of the particle types included in the enumeration. Here, spherical fly-ash particles of any colour are deemed IASs and are precluded from being identified as SCPs for that reason. 

The machine SorTech has developed uses a rotating conical bowl with a cone angle, surface roughness and rotational speed calculated to best suit the particular classification requirement. The machine concept is based on the observation that for particles sliding over a surface of roughness comparable to the particle size, the apparent friction coefficient depends on the particle size. The complete machine is fully enclosed, has a small footprint and a very modest power requirement, and depending on size can process powder at the rate of kilograms to tons per hour. To date, classification has been obtained with several different metal spheroidal particles, coal powder, crushed limestone, fly ash, calcium carbonate and other powders. 

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