Coal of various

The open-column technique is commonly applied in the case of crude oils (being the least complex geochemical organic mixtures). MPLC, high-pressure liquid chromatography (HPLC), and PTLC are more often applied to more complex samples, especially those dominated by more polar compounds, such as hydrothermal bitumens or samples showing terrestrial organic matter input, such as extracts or pyroly-sates of coals of various ranks. 

The only published work on the diffusion of gas in coals of different rank appears to be that of Bolt and Innes (2) who studied the diffusion of carbon dioxide from eleven samples of coal at 38°C. They found the diffusion coefficient to range from 3.5 to 9.2 x 10 8 sq. cm./sec., with no apparent correlation with coal rank. Diffusion data on coals of different rank at temperatures higher than 38°C. have only been reported by the present authors (6). It has been shown (7) that the diffusion of inert or noble gases from coal above room temperatures can be rigorously analyzed by using simple diffusion theory, and that true diffusion parameters of the micropore systems can be obtained. In this paper our measurements on the unsteady state release of argon from coals of various rank, over a temperature range, are reported. 

In this equation dW/dt is the rate of sorption, k. is the experimental rate constant for sorption, W, is the equilibrium sorption, W is the amount of sorption at time t = t, and h is the experimental rate constant for desorption. Thus, the sorption rate was found to be proportional to the square of the concentration of unoccupied sites, and the desorption rate was proportional to the square of the concentration of occupied sites. These rate equations are not general solutions to Fick s law of diffusion. The experimental rate constants for sorption were found to be non-linearly dependent on methanol pressure and seemed to correlate with the amount of surface sorbed methanol in different ways for coals of various rank. 

Nandi, S. P., and P. L. Walker The Diffusion of Nitrogen and Carbon Dioxide from Coals of Various Ranks. Fuel 43, 385/393 (1964). 

Badzioch and Hawksley [9] carried out experiments on the pyrolysis of 11 British coals of various ranks in a laminar flow reactor. They studied pyrolysis at temperatures up to 1000°C, heating coal particles to decomposition in 30-110 ms at a rate between 25000 and 50000°C/s. The volatile product yield in rapid heating was 1.3-1.8 times higher than that found from the difference between the proximate volatile matter of coal and that of char. 

Overall, IGC appears to be a reproducible method for following the chemical and physical changes that occur when coals are heated in an inert atmosphere. Differences in the transition temperature and enthalpies of sorption can be observed for coals of various rank. PyHRMS results indicate that the minor transitions observed in the intermediate temperature region are a result of the loss of volatile matter from the coal. 

It might be expected that coals high in pyrite (e.g., bituminous) would be more reactive than coals that have lower pyrite contents (e.g., subbituminous and lignites). Twenty coals of various ranks were tested by Gulf under SRC-II process conditions 30 wt. percent coal, 440-465°C, 1800-2250 psia H2, one-hr residence time. Coals which processed well had pyritic sulfur or iron contents greater than 1.5%, and were generally Eastern and Interior Province bituminous coals ( 0 ). C5 oil yields (875°F") ranged from 30-35% for coals with pyritic sulfur contents of 1.0 to 1.5% to 40-45% for coals with pyritic sulfur contents of 2.0 to 3.0%. 

In a series of papers Fu and Blaustein229-231 reported that coals of various ranks readily evolved enough of their volatiles to initiate and sustain the discharge at power... 

In another series of experiments Friedel and coworkers268"270) studied the distribution of gaseous products from the laser irradiation of coals of various ranks and particle sizes in various atmospheres. In vacuum experiments the total gas yield varied inversely with coal rank, showing a four-fold increase between anthracite and lignite. The product gas composition as a function of volatile matter in coal is shown in Fig. 20. Yields of acetylene and hydrogen generally increased between anthracite... 

Fig. 19. H cramps spectra of coals of various rank sub subbituminous hvb high volatile bituminous mvb medium volatile bituminous Ivb low volatile bituminous anthr. anthracite. (Reprinted from Bronniman and Madel, " 1989, with kind permission from Elsevier Sdence Ltd.)...

Figure 3 is a collection of C CP/MAS spectra of coals of various rank.9 These spectra are representative of the appearances of most of the CP/MAS spectra of coals that we have seen. They consist primarily of bands in two regions. These are the range from about 170 to about 90 ppm and from about 80 to about 0 ppm. The first band consists mainly of aromatic carbon resonances, and the latter is due mainly to aliphatic carbons. The "aromatic" and "aliphatic" bands are relatively featureless, but some reproducible shoulders can be discerned on some of the peaks, especially for the lower-rank coals. Indeed, some of the lignites show a considerable degree of fine structure, as exemplified by the spectrum of Byrd Stadium lignite shown in Figure 4. This additional fine structure can be attributed to specific structural features (e.g., a shoulder at about 155 ppm attributed to oxygen-substituted carbon in a phenolic system).

Other trends that have been explored in terms of C CP/MAS fg values of coals of various rank are heating values, atomic H/C ratios, fixed carbon, and temperature effects.9a,b,e... 

Figure 3. C CP/MAS spectra oj coals of various rank. All spectra in this and other figures were obtained at 15 MHz, unless otherwise indicated, (Reproduced, with permission, from Ref. 9b.

Network models use lattice statistics to quantitatively describe the thermal breakup of the coal macromolecu-lar stmcture and interpret the interrelationships in the lattice characteristics of coal, tar, and char. The capability of one network model to predict total volatiles and char release for a large number of coals of various rank without the use of any fitting parameters was illustrated in Fig. 7. Char is formed from charring reactions within the network and from cross-linking of nonvolatile metaplast. 

The effect of time of extraction on yields of extract (using bituminous coals of various ranks and primary aliphatic amines as solvents) differs according to whether (1) the coal is shaken in a tube with the solvent at room temperature or (2) it is extracted in a Soxhlet thimble near the boiling point of the solvent. 

Jurkiewicz, A., Wind, R.A., and Maciel, G.E. The use of magnetic resonance parameters in the characterization of premium coals and other coals of various ranks. 1990 69 830-833. 

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