Physical coal density

Physical properties Density Specific gravity Pore structure True density as measured by helium displacement Apparent density Specification of the porosity or ultrafine structure of coals and nature of pore structure between macro, micro, and transitional pores... 

Flotation. The coal is finely ground down to release the inorganic pyrite particles. These may then be separated physically through density differences (density of pyrite about 5.0gcm , density of coal 1.2-1.5 gcm ). This method is not feasible, however, on the large scale required. 

Physical Properties. Physical properties of waste as fuels are defined in accordance with the specific materials under consideration. The greatest degree of definition exists for wood and related biofuels. The least degree of definition exists for MSW, related RDF products, and the broad array of ha2ardous wastes. Table 3 compares the physical property data of some representative combustible wastes with the traditional fossil fuel bituminous coal. The soHd organic wastes typically have specific gravities or bulk densities much lower than those associated with coal and lignite. 

Physical Methods of Examination. Physical methods used to examine coals can be divided into two classes which, in the one case, yield information of a stmctural nature such as the size of the aromatic nuclei, ie, methods such as x-ray diffraction, molar refraction, and calorific value as a function of composition and in the other case indicate the fraction of carbon present in aromatic form, ie, methods such as ir and nuclear magnetic resonance spectroscopies, and density as a function of composition. Some methods used and types of information obtained from them are (41) ... 

The other physical measurements (4,6), except for diamagnetic susceptibiUty (4) and possibly density (4), are primarily of interest for determining chemical stmctural properties of coal. 

In practice, we have a number of solid fuels, for example biofuels (forest or agricultural derived biofuels), coal, municipal solid waste (MSW) and many others [23]. A fuel bed is composed of varying sizes of solid-fuel particles, also called polydispersed solid-.fuels [15]. The fuel chemistry is different depending on whether it is coal, biofuel or MSW. The fuel bed can be dry or consist of moisture. The fuel physics are for example, particle size distribution, particle shape, particle density and bed permeability. 

DENSITY MEASUREMENTS. Helium densities of the extracts were determined so that the gravimetric sorption data could be converted to volume fractions needed to calculate x parameters. The results of these measurements are shown in Table III. The density of the extract was observed to decrease with increasing size of the added alkyl group. These results are qualitatively similar to those of Liotta t al.(14), who studied the effects of O-alkylation on the physical structure of the native Illinois No. 6 coal. 

Bituminous Coala.—Bituminous coal bears a general resemblance to the last, inasmuch as both contain the same substances, varying in. relative quantity. Analysis, however, cannot always determine between them, ai,d the physical marks noted in the preceding pages must be observed narrowly before deciding. For the most part, the density of bituminous coal is greater than that... 

In on effort to establish the mechanism of coal flotation and thus establish the basis for an anthracite lithotype separation, some physical and chemical parameters for anthracite lithotype differentiation were determined. The electrokinetic properties were determined by streaming potential methods. Results indicated a difference in the characteristics of the lithotypes. Other physical and chemical analyses of the lithotypes were mode to establish parameters for further differentiation. Electron-microprobe x-ray, x-ray diffraction, x-ray fluorescent, infrared, and density analyses were made. Chemical analyses included proximate, ultimate, and sulfur measurements. The classification system used was a modification of the Stopes system for classifying lithotypes for humic coals. 

The distillation method of moisture determination requires collection and determination of the water evolved from the coal when the sample is heated in a boiling solvent that is itself immiscible with water. The solution and extraction methods require either solvent extraction of the water from the coal (followed by subsequent determination of the water content of the solvent) or use of a standard reagent that will exhibit differences in concentration by virtue of the water in the coal. A nonthermal solvent method of determining moisture involves the use of an extraction procedure in which the coal is shaken with a solvent that extracts the water from the coal. The degree of change in some physical property of the solvent, such as density, is then used as a measure of the water extracted. 

When determining the physical properties of coal, there is often considerable debate about the correctness of the results obtained from measurements by two or more different analytical techniques. Provided that the methods and/or equipment used was capable of producing high-quality data, the pertinent issues relate to whether or not the sample properly prepared and properly measured and whether or not the analytical parameters applied correctly in the data-handling step(s). Thus, the concept of different techniques yielding different, albeit correct results can apply to the measurement of physical properties such as density, porosity, particle size, and surface area. 

Amestica and Wolf (12) in a study closely related to the one described herein, measured the conversion of Illinois No. 6 coal in toluene and ethanol. Their results clearly showed that conversions increased with temperature and solvent density but were not detailed enough to show the time dependence of the conversion. However, a result important to this study was that toluene converts coal to liquids without significantly reacting itself. After reaction, 98% of the toluene used was recovered versus only 73 -85% of the ethanol in runs using it. Ethanol is a hydrogen donor and reacts extensively with the coal. While toluene probably reacts with coal to a small extent, its effect was primarily physical in nature. As such, it is a good candidate for studying the effects of a supercritical solvent on coal liquefaction kinetics since the enhancement effect of supercritical conditions is physical in nature. 

Physical cleaning of various coals by oil agglomeration reduced levels of As, Cr, Pb, Mn, Mo, Ni, and V by 50-80%, while levels of some other trace elements were reduced by lesser amounts (20). Oil agglomeration appeared to be more effective at removing trace elements than the wet concentrating table or float/sink density separations. This may be related to an increase in the liberation of mineral matter associated with grinding to produce the relatively fine particle sizes required in the oil agglomeration technique. 

Experimental results in many situations show a high correlation between particle density and the chemical or physical property of interest. They also show a relatively low correlation between particle size and the chemical or physical property of interest. Some data collected by Bilonick (1989) on percent ash in coal and shown in Figure B.l illustrate this phenomenon quite well. Higher-density particles have higher percent ash content regardless of the particle volume. On the other hand, higher-volume particles with the same density have about the same percent ash content. 

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