Coal continued structure

Jhe distribution of hydrogen types in coals continues to be a subject of considerable interest in coal structure studies. Published data indicate that the fraction of aromatic hydrogens usually increases with increasing rank, but the absolute values depend on the specific analytical method used (7). Hydrogen type analysis of a single coal based on the application of NMR spectroscopy to the soluble fraction from depolymerization with phenol-BFa has been reported by us (3). The conversion of coal to soluble fragments in substantial yields under very mild conditions permits a reliable determination of the hydrogen types by NMR analysis, and these results can be extrapolated to the parent coal with considerable confidence. 

The literature on the subject of coal composition, structure, and use has grown significantly during the last two decades, as interest in coal research has continued. The future of coal science looks bright as researchers continue to make significant contributions to the elucidation of the structure, composition, and physicochemical behavior of coal. New analytical techniques have made an important contribution to these advances. The objective of this chapter is to provide a brief review of the state of the art of coal science and technology. 

Structurally, the Shilbottle Coalfield is relatively simple. The strata strike approximately 45°N and dip about 10° to the SE. Antithetic extensional faults disturb seam continuity locally (Fig. 6), and a single major fault system striking approximately 85°N (cropping out in the vicinity of Whittle Fig. 6) down-throws the coal to the north by some 200 m. 

Since the work reported by McCartney et al. (9), ultrathin sections of other, more heterogeneous components and mixtures of components of coals of different rank have been prepared and observed. Procedures for minimizing artifacts have been learned and followed, and experience in observation has led to avoiding obvious faults. These sections were often not as large and continuous as those of homogeneous vitrinites, but adequate areas were available for electron microscopy. Observations of these various components revealed ultrafine structures of different size and form. Some of the structures can be correlated with those deduced from other direct or indirect study techniques others are unfamiliar and novel, and suggested interpretations are tentative. 

Electrical conductivity depends on several factors, such as temperature, pressure, and moisture content of the coal. The electrical conductivity of coal is quite pronounced at high temperatures [especially above 600°C (1112°F)], where coal structure begins to break down. Moisture affects electrical conductivity to a marked extent, resulting in a greatly increased conductivity. To prevent any anomalies from the conductance due to water, the coal is usually maintained in a dry, oxygen-free atmosphere, and to minimize the problems that can arise, particularly because of the presence of water, initial measurements are usually taken at approximately 200°C (392°F) and then continued to lower temperatures. 

We present here the preliminary results of our attempt to develop a new method for the analysis of pyrite in coal and lignite. It is well known that sulfur in coal is present in different forms. In particular, although the iron sulfide in coal is generally pyrite ( 1), other iron sulfides are frequently present. For example, iron disulfide occurs as marcasite, a rhombic crystalline form, as well as pyrite, a cubic crystalline form. Perhaps the term disulfide sulfur should be used to replace the pyritic sulfur more commonly quoted, as recently suggested by Youh (2). Since the chemical reactivity of these two disulfides of iron is similar, our method will record them equally well. Nonetheless, we will continue to refer to the pyrite determinations here, although we are really talking about the chemical species FeS2 rather than a particular crystalline structure. 

The prevalence of structural types based on aromatic or heteroaromatic nuclei among chemicals available from coal tar or petroleum contrasts with the structural types that represent the major groups of natural products. Chemicals from natural sources are a rich source of structural diversity and reflect the complexity of biological systems in which the processes of biosynthesis and the biological roles of molecules have undergone continual change and modification. 

Victorian brown coal occurs in five major lithotypes distinguishable by color index and petrography. Advantage has been taken of a rare 100 m continuous core to compare and contrast chemical variations occurring as a function of lithotype classification. For many parameters there is a much greater contrast between the different lithotypes than there is across the depth profile of (nearly) identical lithotypes. Molecular parameters, such as the distributions of hydrocarbons, fatty acids, triterpenoids and pertrifluoroacetic acid oxidation products, together with gross structural parameters derived from IR and C-NMR spectroscopic data, Rock-Eval and elemental analyses and the yields of specific extractable fractions are compared. 

Despite the well-known association and trapping of liquid hydrocarbons within the coal structure, liquid hydrocarbons apparently are continuously generated and expelled from coal. Nevertheless, residual quantities of liquid hydrocarbons are normally trapped within the coal macromolecular matrix. These trapped liquid hydrocarbons are probably converted to gas during continued coalification. 

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