Coal Wyodak

A recent study in these laboratories (75) on calcium carbonate precipitation from Wyodak coal has confirmed the relationship between ion-exchangeable calcium and the appearance of calcium carbonates during liquefaction. These experiments were performed on samples of the subbituminous coal which had been demineralized, to ensure that all carboxylic acid groups were in the acidic form, and subsequently exchanged with varying amounts of calcium ions. 

In this Laboratory, several potential liquid-phase treating agents have been studied at 225-275°C—that is, at temperatures well below 325°C, which appears to be the initiation temperature for pyrolysis of the coals studied here. Working with Wyodak coal in a ZnC -water melt at 250°C, Holten and coworkers (2,3) discovered that addition of tetralin increased the pyridine solubility of product to 75%, compared to 25% without tetralin. About 10 wt-% of water is required in the melt, because pure ZnC melts at 317°C. 

Table 1. Effect of Operating Variables on Incorporation of Methanol and on Corrected H/C Ratios C273 g ZnCl, 50 g Wyodak coal)...

Figure 8. Comparison of Number of Bonds per Bead for a) Original Wyodak Coal (initial crosslinks = 290, initial extract yield = 7.4%, oligomer length = 10 and hard bonds = 200) and c) Modified Wyodak Coal (initial crosslinks = 600, initial extract yield = 21.5%, oligomer length = 4 and hard bonds = 0). b and d Compare the Fluid Fraction and Extract Yield for Original Wyodak Coal and Modified Wyodak Coal, Respectively.

Alkylation Studies. Several preliminary experiments were completed to compare the extent of alkylation obtained with our coal pretreatment method to that obtained with Sternberg and Liotta alkylation. Results for Wyodak coal are summarized in Table III. Clearly, our procedure provides a very mild alkylation treatment compared with the other two methods and does not appear to be sensitive to differences in alkyl chain length (methyl vs. propyl). The increase in THF solubiliw was also small this result again suggests only a small extent of alkylation and in addition, shows that only minimal ion exchange (for example Ca by H ) occurred in the coal mineral matter. The effect of each pretreatment method on low severity liquefaction reactivity is discussed in the next section. 

Results From Ambient Pretreatment Experiments Using Wyodak Coal... 

Figure 3 shows the effect of reaction temperature on the liquefaction reactivity of methylated (3 hrs, 100/1 methanol/HCl wt. ratio) and untreated Wyodak coals using DHP solvent. Mildly treating the coal (approx. 0.2 methyl groups added/100 carbon atoms) resulted in THF conversion improvements of about 21 wt% at 315 C, 23 wt% at 350 C, and 14 wt% at 400 C. Clearly, mild pretreatment enhances reactivity over the entire range of observed conversion levels. This result is very significant since it shows that our pretreatment procedure is beneficial at conversion levels of commercial interest, and thus, represents more than a laboratory curiosity. 

Figure 2. Effect of Alkyl Group Size on Coal Liquefaction Reactivity of Treated Wyodak Coal at I w Severity Reaction Conditions.

Figure 3. Effect of Reaction Temperature on Liquefaction Reactivity of Methylated and Untreated Wyodak Coal.

Figure 5. Effect of Various Pretreatment Methods on Enhancement of Low Severity Wyodak Coal Liquefaction Reactivity.

Figure 6. Subtractive Photoacoustic Fourier Transform Infrared Spectrum of Propylated Wyodak Coal.

Such bridges in coal structure have been reported only recently. Alkyl substituted methylene and ethylene bridges have been detected in a Wyodak coal by Benjamin et al.. In the present study, some of the branched chain bridges may have been formed by rearrangement of the straight chain bridges during transalkylation. ... 

Illinois coal Wyodak coal Cyclop araffinic Paraffinic... 

Table XII. Ring Number Distributions for Coal Liquids Produced from Illinois No. 6 and Wyodak Coal Using Different Processing Conditions, Weight Percent Total Coal Liquid Basis...

H-Coal naphthas and distillates derived from Illinois No. 6 (Burning Star Mine) and Wyodak coals were supplied by Hydrocarbon Research, Inc. The naphthas and distillates were blended in the appropriate proportions to obtain a whole syncrude derived from each coal. Properties of these syncrudes are shown in Table I. For comparison, Table I also shows properties of the SRC-II syncrude used in the study described in the previous chapter. The SRC-II syncrude was derived from a West Virginia coal (Pittsburgh Seam, Blacksville No. 2 Mine of the consolidated Coal Company). The H-Coal and SRC-II syncrudes are not directly comparable because the coals used to derive these syncrudes differ. 

Figure 1. Chromatographic observations for pristine and exposed samples of low sulfur Wyodak coal. Elemental sulfur emerges at 38.3 minutes under the conditions of the analysis. A. Unconcentrated extract of APCSP-2. B. The extract of APCSP-2 after 20-fold concentration. C. Unconcentrated extract of exposed Wyodak coal. D. The same extract after 20-fold concentration. (Adapted with permission from ref. 6. Copyright 1985 Fuel.)...

Figure 4. Effect of reactor configuration on yields (Wyodak coal 300 psi 1050°F)...

Wyodak coal from Wyoming was selected as a suitable low-rank Western coal for this study. It is inexpensive to produce and is available in an abundant supply. Additionally, the regulations in Wyoming permit the extraction of coalbed methane, making it attractive for C02 sequestration and coalbed methane recovery. Coal would be mined from this region gasified to produce hydrogen then the C02-rich off gas would be injected into unmineable coal beds. 

The elemental analysis and heating value of the selected Wyodak coal is given in Table 1. 

Table 1. Wyodak coal analysis for this study...

Parsons Infrastructure and Technology Group Decarbonized Fuel Plants for Vision 21 Applications, WYODAK Coal Substitution DOE/FETC Report, April 13, 1999. 

TABLE III. RELATIONSHIP BETWEEN REACTION TIME, TEMPERATURE, REACTION SEVERITY AND CONVERSION OF WYODAK COAL TO PYRIDINE SOLUBLES... 

MAF Coal Conversions to Pyridine Solubles. MAF coal conversions, based on ash analyses, are shown for each coal-solvent combination in Figure 3. Subbituminous coal is converted more slowly, resulting in lower conversions at identical reaction severities than bituminous coal. Maximum conversions are higher with bituminous coal, approaching 90 percent on an MAF basis for the Monterey coal compared to about 75 percent for Wyodak coal. 

Figure 4. Elemental analyses of SRC from liquefaction of Wyodak coal in —019 solvent (prepared by distillation)...

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