Brown coal characterization

It is important to realize that the bed moisture content of soft brown coals is significantly higher than the equilibrium moisture holding capacity, a parameter which is used to characterize higher rank coals. This is illustrated in Table 1 for a range of Victorian brown coals. 

Figure 7. Chemo-physical characterization of the brown coal lithotypes subjected to investigation. (Reproduced with permission from Ref. 19. Copyright 1983, Schriftleitung Braunkohle.)...

The example of application of the statistical prediction method represented in Figure 4 contains a Czechoslovakian brown coal of group 1 which experience has shown to be a particularly vicious fouling coal and a GDR brown coal of group 3 which tends toward behavior of a salt coal but whose operational behavior, while complicated, can be controlled. The values calculated for fg and fp coincide with practical experience while the parameter Rg indicates that the Czechoslovakian coal is harmless whereas the GDR coal is characterized as uncontrollable by available technologies. 

The rate of the oxidation process is determined by the reactivity of the starting carbon and oxidizer. The greater the reactivity of the substrates the lower the temperature of the process in which uniform formation of the pores in the granules is observed. In the case of carbonaceous materials the cokes of brown coals show the greatest reactivity, and the cokes of hard coals the smallest activity. The cokes of pit coals show an intermediate reactivity. This is connected with the earlier mentioned ordering of the crystallographic structure of carbon, which is of significant importance in the case of modification of carbon deposits contained in the carbon-mineral adsorbents in which the carbonaceous compound may be characterized by a differentiated chemical and physical structure. Thus the surface properties of hydrothermally modified complex adsorbents are defined by the course of three processes ... 

F. Skvara, L. Kopecky, V. Smilauer, Z. Bittnar, Material and structural characterization of alkali activated Low-calcium brown coal Fly Ash, J. Hazard. Mater. 168 (2009) 711-720. 

The humic acids offered commercially by some manufacturers are not recommended as reference materials. These substances are usually obtained from terrestrial sources such as peat or brown coal. They lack strict quality control, Le., the composition differs from batch to batch. Furthermore, these comp>ounds are poorly characterized, even in terms of elemental composition and ash content. Further information on this problem has been provided by Malcolm and McCarthy (1986). 

Skvdra, R, Kopecky, L., Smilauer, V., and Bittnar, Z. Material and stmctnral characterization of alkali activated low-calcinm brown coal fly ash. 

Characterization of brown coal coke produced in rotary hearthfumaces... 

High-resolution NMR spectrometry was used first by Brown and Ladner for structural characterization of coal pyrolysis products (3). Other workers have extended this type of analysis to coal extracts (4) and coal hydrogenation products (5,6,7), A recently published com-... 

Nevertheless, it is surprising how often one refers to elemental analysis to confirm the presence of a humic or fulvic acid. It is useful in determining whether a brown, macromolecular acidic material is from a coal, soil, marine sediment, or kerogen. It is most useful in characterizing structural trends in a specific environment, such as in sediments or soil profiles. Atomic ratios, especially 0/C ratios, are the simplest way to display elemental composition of humates. They also help one devise hypothetical structures for humates. As a guide in the synthesis of artificial humic substances, they are invaluable. In addition, atomic ratios help the investigator identify nonhumate contaminants. 

Fourier Transform Infrared (FT-IR) Spectroscopy is one of the most versatile techniques available for providing analytical data on the raw materials, the process chemistry and the products. Dispersive infrared spectroscopy has traditionally been an important tool in fuel characterization since most organic and mineral components absorb in the IR. Discussions of applications to coal may be found in Lowry (1 ), van Krevlen (2 ), Friedel O), Brown (O, Brooks, Durie and Sternhell ( 5) Friedel and Retcofsky (O and references cited therein. But FT-IR with its advantages in speed, sensitivity and data processing has added new dimensions. 

Bituminous materials are dark brown or black, semi-solid or liquid, thermoplastic mixtures of hydrocarbons derived from natural or synthetic processes in which hydrocarbon mixtures have lost their volatile components leaving a denser residue. Natural bitumens come from exposed and weathered petroleum and rock deposits. Synthetic bitumens come from the residue remaining after the distillation of petroleum, coal tar, and other organic materials like wood and peat. The complexity of the high molecular weight hydrocarbon oils and resins bitumens contain make complete chemical characterization impossible. The terms bitumen, tar (8007-45-2), pitch (61789-60-4), and asphalt (8052-42-4) apply to any of these substances, although pitch and tar also describe the sticky resins that exude from various trees. 

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