Upper Freeport coal

Two bituminous coals of moderate ash content were chosen for this paper to illustrate this method of determining coal-mineral association. The first sample was an Upper Freeport coal with 1.3% moisture, 9.88% ash, and 1.56% total sulfur. The second sample was an Indiana No. 3 coal having 10.5% moisture, 7.35% ash, and 4.26% total sulfur. Both coals had been precleaned at a coarse particle size, ground to minus 325 mesh (44 ym), and then separate samples were cleaned by float-sink and by froth flotation techniques, as described elsewhere [5]. Analyses of the feed coals are included in Table I. 

The first method chosen to express the coal-mineral association results is in terms of the weight fraction of mineral matter in the individual particles, as determined from their cross section. The resulting distribution is comparable to the so-called "grade distributions" used in the mineral industry [8,9]. Such a distribution is included in Table II for the Upper Freeport coal. The data in the table indicate that pyrite is preferentially liberated as compared to quartz or kaolinite. About 78% of the pyrite is in particles containing more than 80% mineral matter, which should be easily removed by density-based separations. 

Figure 2. Distribution of selected minerals in Upper Freeport coal as a function of area-equivalent particle diameter (ym).

Figures 6 and 7 show the coal-mineral association for the same Upper Freeport coal sample expressed in terms of the amount of mineral matter on the surface of the particles. There is considerable difference between these two figures and Figures 4 and 5. While Figure 4 shows that about 80% of the mineral matter is present in particles containing more than 40% mineral matter (i.e., less than 60% coal). Figure 6 indicates that only 16% of the mineral matter is associated with particles for which more than 40% of the surface is covered by mineral matter. Indeed, about 70% of the mineral matter is found in particles with more than 80% of the surface covered by coal. Also, the preferential liberation of pyrite noted in terms of bulk composition is absent when association is measured in terms of particle surface.

Thus, the above results for the Upper Freeport coal indicate that density-based processes (e.g., float-sink separation) should be able to remove significant amounts of mineral matter, while surface-based processes (e.g., froth flotation) will likely be unable to reduce the mineral content significantly. Results of cleaning tests reported elsewhere [5] have generally verified these predictions. 

However, the coal-mineral association results for the Indiana coal, when expressed in terms of particle surface in Figures 10 and 11, again show that mineral liberation is less than when the association is considered in terms of bulk properties. But in terms of particle surface, the mineral matter in the Indiana coal appears to be a little better liberated than it is in the Upper Freeport coal. And, like the Upper Freeport sample, no preferential association or liberation of minerals is noted when the association is expressed in terms of particle surfaces. 

Analysis of coal-mineral association in samples of Upper Freeport and Indiana No. 3 coals showed significant differences in the association of minerals with the coal matrix. In terms of bulk properties, the mineral matter was generally more liberated in the Upper Freeport coal than in the Indiana No. 3 coal. Also, based on bulk properties, pyrite was found to be preferentially liberated in the Upper Freeport coal, while no such preferential liberation was observed for minerals in the Indiana No. 3 coal. For both coals, the... 

Interestingly, Upper Freeport coal shows two distinct mass spectral patterns in 230-270 C range (Figure 6c), which contains homologous series at m/z 156,170,... 

Low volatile bituminous Pocahontas 3 coal shows different early mobile phase components in terms of alkylsubstituted benzenes (m/z 92, 106, 120) and further shows similar components (several homologous ion series) compared to medium volatile bituminous Upper Freeport coal (e.g. at m/z 192,206,220,234 m/z 216, 230, 244, 258 and m/z 266, 280,294). From the above observations on seven coals, it is clear that there is a chemically and/or physically distinct mobile phase, at... 

Figure 6. Thermally extracted mobile phase components over different temperature intervals from Lewiston-Stockton and Upper Freeport coals.

Table I. Maceral Composition of Upper Freeport Coal...

Table I summarizes the petrography of the Upper Freeport coal examined at five sites shown in Figure 2. Earlier detailed study in the region of the type section (7) established a persistence of beds over a distance of 23 miles (sites 1, 2, and 3 in Table I and Figure 2). Irregularities of the basal portion of the coal were not sufficient to obscure the analytical results of the main bed. The petrographic characteristics of mined coal was significantly altered when an overlying bed (F coal) was included as Upper Freeport coal. The coal at these three sites are high volatile A bituminous in rank.

Figure 2. Sample locations—Upper Freeport coal 1—Harmar Mine, 2— Springdale Mine, 3—Armstrong Mine, 4—Coral strip mine, 5—Houtzdale...

Figure 3. Correlation of Upper Freeport coal beds in Houtzdale quadrangle by layers having similar petrographic analyses...

Ruppert, L.F., Minkin, J.A., McGee, JJ. and Cecil, C.B. (1992) An unusual occurrence of arsenic-bearing pyrite in the Upper Freeport coal bed, west-central Pennsylvania. Energy and Fuels, 6(2), 120-25. 

The results from the IGC experiment on Upper Freeport Coal (APCS No. 1) are presented in Figure 3. There are three retention mechanisms likely to affect the IGC results. These mechanisms include molecular sieving, surface adsorption, and the dissolution of the probe in the stationary phase. The observed retention behavior results from the combination of the effects operating under the given conditions. The specific retention volume, Vg, is given by the sum of the retention terms in Equation 1 ... 

Figure 3. Plot of the log of the retention volume versus the Inverse of temperature for Upper Freeport coal.

A comparison between the IGC results for Upper Freeport coal with results obtained via Giesler plastometry is presented in Figure 8. The marked increase in retention volume that indicates the start of the third region correlates well with the initial softening temperature. For the coals investigated thus far, the transition is observed in the IGC 10 to 15 0 before the initial softening temperature. 

Figure 10. Comparison of inverse gas chromatography experiments on the Upper Freeport coals that have undergone various oxidative treatments.

Coal, Soil Organic Matter and Other Related Materials. - 5.5.1 Coals and Carbonaceous Materials. C - The extract from carbon disulfide/AT-methyl-2-pyrrolidinone mixed solvent extraction of Upper Freeport coal at room temperature has been fractionated with acetone and pyridine into three fractions, and solid-state NMR measurements of these fractions have been measured. 

Takanohashi, T. and lino, M. 1995. Investigation of associated structure of upper freeport coal by solvent swelling. Energy Fuels, 9 788-793. 

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