/ A 14. GS: CIR &* GjUX S^J 18.3% Extract + 81.7% residuet 15.0% Extract + 85.0% residue 10.0% Extract + 90.0% residue 5.0% Extract + 95.0% residue 1.0% Extract + 99.0% residue 375 399 428 474 99 3,500 none none none none none 350 385 420 472 125 > 37,500 335 387 422 475 120 12,600 1/2 360 391 425 475 115 10,700 1/2 367 394 426 474 107 8,000 380 402 435 480 100 1,700 382 405 433 481 99 62 (1) (2) (3) (4) (4) (4) (5) (6) * Blends made up on basis of air-dry values, t Made up to duplicate original coal. ** (l) Coal swells to \ height Gieseler barrel. (5) Swelling equals the swell- (2) Residue can be poured from Gieseler crucible. ing of original coal. (3) Pyridine extract swells out of crucible. (6) In the plastic state this (4) Blends swell to 2/3 height Gieseler barrel. blend does not swell. ILLINOIS STATE GEOLOGICAL SURVEY PYRIDINE EXTRACT r.E CHLOROFORM EXTRACT n-HEXANE EXTRACT 21 987654321 987654321 Percent Oxygen Content of Coal Investigated Fig. 1. - Yields of extracts versus oxygen content of the coals investigated. DISCUSSION The following discussion is limited to the eight specially prepared samples of coal. The original samples were selected to represent a progressive increase in rank from high-volatile B bituminous to low-volatile bituminous coal. It must be emphasized that to project similar conclusions to other coals may be misleading. In table 1, the samples A to H are arranged in order of decreasing oxygen content. Figure 1, plotted on a linear scale, demonstrates the relationship be- tween yields of pyridine, chloroform, and n-hexane extracts and amount of oxygen in the coals investigated. The amount of oxygen is shown as decreasing to conform, in general, with the increase in rank. With the exception of the D or Willis Coal, the samples indicate that as the oxygen content progressively decreases, the percentage of extracts increases to a maximum, then decreases. As compared to the chloroform and n-hexane extract, the curve for pyridine extract is unsymmetrical. This will be discussed later. Figure 2 shows the relationship between the progressively decreasing vola- tile matter and oxygen contents of the coals investigated and their maximum Gieseler fluidities. The volatile matter and oxygen contents are plotted on a linear scale and the fluidities on a logarithmic scale. Here, as in figure 1, the point represent- ing sample D or Willis Coal does not appear to follow the general relationship for oxygen versus fluidity. It may be added that, in spite of possible error reflected in the calculation of oxygen in the ultimate analysis of coal, the curve shown in figure 1 appears to be symmetrical and indicates that as the amount of oxygen in coal decreases, the maximum Gieseler fluidity increases to a maximum, then decreases. In contrast, the Gieseler maximum fluidity of coal is independent of the volatile matter content if the volatile matter is greater than 39 percent on a moisture- and ash-free basis. For volatile matter less than 39 percent, it appears that as the volatile matter decreases (or rank increases), the Gieseler maximum fluidity decreases. Figure 3 shows the yields of pyridine extracts as a function of the Gieseler maximum fluidities for the eight coals investigated. The decreasing yields of extracts are plotted on a linear scale and the maximum fluidities on a logarithmic PLASTIC PROPERTIES OF COAL scale. As the rank, of the coal in- creases the yields of pyridine extract increase and maximum fluidities in- crease up to a maximum; then, as the rank continues to increase, the yield of extract and maximum fluidity de- crease. Both the ascending and de- scending parts of the curve appear to approach a straight-line relationship. Figure 4 shows the yields of chloroform and n-hexane extracts as a function of the Gieseler maximum fluidities. The data are plotted on a 10.000 • Fig. 3. - Maximum Gieseler fluidity versus percentage of pyridine extract. 100,000 r 39 37 Percent 35 33 31 29 27 25 23 Volatile Matter, M-A free bosis Percent 7 6 5 4 3 Oxygen, M-A free basis Fig . 2. - Maximum Gieseler fluidities versus volatile matter and oxygen contents. 22 21 20 19 Percent Pyridine scale similar to that of figure 3. Attention is called to the fact that a more direct relationship is appar- ent between the chloroform and n- hexane extracts and their maximum fluidities than between the pyri- dine extracts and their fluidities. During the pyridine extrac- tion procedure it was noted that the amount of swelling of the pyri- dine residue progressively de- creased as rank of coal increased. For example, the dried pyridine residue of Coal B had a volume approximately twice as great as 1,000 D and H 10 ILLINOIS STATE GEOLOGICAL SURVEY 100,000 that of its parent coal. In contrast, the volume of the dried pyridine resi- dues of coals F, G, and H appeared to be similar to those of the original coals. It might be postulated that as = 10.000 swelling of coal in contact with pyri- dine becomes greater, the probability of dispersion of coal particles in the solvent would increase. This behavior has been previously reported and dis- cussed by Pierron et al. (1959). Such an assumption also is indicated by comparing the shape of the pyridine extract curve in figure 1 to those of the chloroform and n-hexane curves. If the interaction of pyridine with coal caused only solution with no colloidal dispersion of coal particles, it might be expected that the pyridine extract values for samples B and C would be lower and thus would contribute to a more symmetrical curve. Pursuing this line of thinking with reference to figure 3, it is interest- ing to note that if the determined yields of pyridine extract for coals B and C are high by approximately 4 percent and 3 percent respectively, due to colloidally dispersed coal particles, the values would fall on the right-hand portion of the curve thus permitting construction of a single curve without a doubled back portion. In other words it would indicate a more direct relation between yields of pyridine extract and maximum fluidity regardless of the rank of coals studied. Point D in figure 3 would not fall on the single curve so con- structed, but this might be explained by the fact that sample D was shown to con- tain a considerably larger amount of inertinite than the other coals (table 2). Table 4 compares the molecular weights and atomic H/C and O/C ratios of pyridine, chloroform, and n-hexane extracts for the coals investigated. As the rank of the coals increases from sample A to sample H, the H/C and O/C ratios of the pyridine extracts remain more or less constant, but the molecular weights de- crease from 1600 to 1175. Such decrease in molecular weight may be related to the lesser amount of dispersed particles of the parent coal in the extract as the rank increases. The chloroform extracts indicate similar H/C and O/C ratios, but as rank increases the molecular weights increase from 490 to 575. The n-hexane extracts show similar H/C and O/C ratios, and as in the case of chloroform extracts, as rank increases molecular weights increase from 380 to 525. Table 5 shows free swelling indexes, Gieseler plasticity data of coal C, pyridine residue and extract, and blends made of extract and residue. A blend of 98765 43210 Percent Chloroform Extract Percent n-Hexane Extroct Fig. 4. - Maximum Gieseler fluidity versus percentage of chloroform and n-hexane extracts. PLASTIC PROPERTIES OF COAL 11 18.3 percent pyridine extract and 81.7 percent residue was made to duplicate the original percentage composition of the coal on an air-dried basis. Other blends were made up of respectively 15, 10, 5, and 1 percent extract and 85, 90, 95 and 99 percent residue. An addition of 5 percent of extract to the residue increased the free swelling index from 1 to 6 or to a value approximately equivalent to that of the original coal. The progressive addition of extract to residue progressively lowered the softening and fusion temperatures, had little effect on the maximum and setting temperatures, and increased the plastic ranges and maximum fluidities. Stephens (1958) reported similar results when pitch was added to coal. Nevertheless it appears that addition of 5 or 10 percent pyridine extract to residue induces plastic properties in a temperature range similar to the plastic temperature range of the original coals but with considerably greater maximum fluidities than those of the original coals. CONCLUSIONS 1) Data are presented to indicate that yields of extract obtained with each solvent increase with decrease of oxygen content of samples to a maximum and then decrease with further decrease of oxygen content. Attention is called to the possibility that extract yields for certain of the coals possibly may have been high due to colloidal dispersion of coal in the solvent. 2) Yields of extracts for each solvent are proportional, although not neces- sarily directly proportional, to fluidities of the coals as measured by the Gieseler plastometer. 3) For the eight coals studied, the pyridine, chloroform, and n-hexane extracts for each coal show similar analyses. 4) The data presented indicate that fluidity is related to the quantity of extract obtained rather than to difference in kind of extract. 5) Addition of pyridine extract to nonplastic residue induces fluidity higher than that of the original coal. REFERENCES Marshall, C. E., Harrison, J. A., Simon, J. A., and Parker, M. A., 1958, Petrographic and Coking Characteristics of Coal: Illinois Geol. Survey Bull. 84. Pierron, E. D., Rees, O. W., and Clark, G. L., 1959, Plastic properties of coal: Illinois Geol. Survey Circ. 269. Rees, O. W., and Pierron, E. D., 1954, Plastic and swelling properties of Illinois coals: Illinois Geol. Survey Circ. 190. Stephens, J. N., 1958, The effect of pitch additions on the fluidity of coal: Coke and Gas, July 1958, p. 296-297 and 302. Illinois State Geological Survey Circular 288 11 p., 4 figs., 5 tables, 1960 ■ miiur*t JUwdofi£vico6vn CIRCULAR 288 ILLINOIS STATE GEOLOGICAL SURVEY URBAN A ■$•<"■»??*$• 1U