Coal lithotypes

As stated before, volatile carbon % is considered to be one of the most important parameters of hydroliquefaction. Also a fairly good linear relationship between the volatile carbon % in coal and low temperature tar yield from coal is found in Morwell brown coals, based on the data from the State Electricity Commission of Victoria (SECV) in Australia, as shown in Fig.9 Therefore, the low temperature tar yield is also estimated to be an important parameter. In addition, the color tone of brown coal (lithotypes) is shown in this figure. From this figure, it is observed that both volatile carbon % and low temperature tar yield are in a fairly good relation to the color tone of brown coal. Thus, as proposed by the Australian researchers, the color tone of brown coal is considered to be an important parameter. 

This paper summarizes our understanding of the geochemistry of sulfur in coal in the following areas 1) abundance of sulfur in coals of major coal basins in the U.S., 2) distribution of sulfur in coal lithotypes and macerals, 3) characteristics and geochemical significance of sulfur-containing organic compounds,... 

Coal lithotypes are megascopically recognizable components of coal. Several nomenclatures have been used to identify the lithotypes [see Damberger et al. (54) for a review of several common classifications]. Coal lithotypes have fairly distinct maceral compositions, which originate from different combinations of plant materials and evolve along somewhat different paths during coalification. 

Figure 1. Coal lithotype variation in a 1.73-meter vertical column of Herrin (No. 6) Coal, Jefferson County, IL.

Based on macropetrographical criteria (determination of the lithotypes by visual examination with the naked eye) 15 brown coal lithotypes were selected for the investigations described in the following they represent more than 90 % of the main seam. 

Figure 3 shows these 15 brown coal lithotypes arranged according to stratification (unbanded to banded coal) and texture (plant tissue content). 

Micropetrography evaluates the coal components ascertainable by microscopy. Figure 4 shows an extract of the results obtained from the combined maceral-microlithotype analysis after the International Handbook of Coal Petrography of the 15 brown coal lithotypes. 

Figure 3. Macropetrographical classification of 15 brown coal lithotypes from the Rhenish area. (Reproduced with permission from Ref. 2. Copyright 1981, Schriftleitung Braunkohle.)...

Subsequent to the petrographical coal analysis, both a chemical and a chemo-physical investigation were carried out. Figure 7 shows the chemical and physical properties of the investigated brown coal lithotypes. 

Figure 8. Heating value of the brown coal lithotypes as a...

In order to establish statistically usable data on the briquetting behaviour of Rhenish brown coals, the 15 brown coal lithotypes were briquetted under identical conditions (water content, grain size distribution and mould pressure) with a laboratory press. 

Two gasification processes under development, namely High Temperature Winkler Gasification (HTW) and hydrogasification of lignite (HKV), encouraged to study the gasification behaviour of various brown coal lithotypes (15). 

The lithotype profile was investigated in greater detail with the product composition of the different brown coals being reported in Tables 1 and 2. A distinct decrease in the total concentration of detectable oxidation products occurs with darker lithotypes (Table 1). This result is consistent with increasing aromaticity (Figure 2) and the preferential attack on aromatic structures by the pertrifluoroacetic acid reagent. The total destruction of the tertiary structure within the brown coal lithotypes is evidenced by their low yield of insoluble products (Residue) which is primarily composed of mineral matter. 

Product Composition of Brown Coal Lithotypes Pertrifluoroacetic Acid Oxidation Mixtures... 

Weight % of initial coal lithotype appearing as oxidation product. 

The neutral material is thought to derive primarily from molecules trapped within the macromolecular coal matrix (13). This theory is supported by the structural independence exhibited by the neutral chromatograms to variations in coal lithotype. The presence of multiple hydroxyl substitutional isomers is thought to reflect oxidation by the reagent mixture. 

This study reports the monocarboxylic fatty acid content of a series of brown coal lithotypes from the Latrobe Valley, Victoria, Australia. We have looked both at the solvent-extractable, or free, fatty acids (which include those extractable as esters or intact lipids) and at those that are released upon hydrolysis (saponification) of the residue after solvent extraction. The latter are presumably bound chemically to the coal matrix (kerogen) and are therefore designated as bound acids. The total acids are taken as the sum of the free and bound acids. 

It should be pointed out that the lithotype classification for brown coal does not conform to that for black coal. To date, the International Committee for Coal Petrology (ICCP) has not finalized a brown coal lithotype classification however, it is generally agreed that a lithotype classification should be based on macroscopic characteristics that can be determined in open cut faces. This principle has been followed in classifying the Latrobe Valley coals according to a system developed and used by the State Electricity Commission of Victoria (SECV) (25). 

Samples. Brown coal lithotype samples were taken from a bore core from the Flynn field in the Loy Yang region of the Latrobe Valley, Victoria, Australia. The brown coal deposits in this area are believed to be Miocene to Eocene in age. All five lithotype samples were taken at depths between 93 and 100.5 m below the surface in a 120-m core and were provided by the SECV. The black coal sample was from the Upper Hunter region (Permian) of New South Wales (Sydney Basin), Australia, and had a carbon content of 81.3%, dry, ash-free basis (DAF). This sample was provided by the Australian Coal Industry Research Laboratories Ltd. (ACIRL). The characteristics of these samples are set out in Table II. 

Acid groups such as triterpenoid acids, dicarboxylic acids, and hydroxy acids also are present in brown coal. Although this paper is restricted to the monofatty acid levels and distributions in brown coal lithotypes, these other acid types also have been observed to vary in level and distribution with lithotype and may, in fact, prove to be useful as indicators of the depositional environments. 

Figure 1. Relationship between actual percent pyrite and percent of total integrated intensity for Pyrite Bragg Reflection for various coal lithotypes.

The coal lithotype of coal layer No. 15-1 and No. 15-3 are both semibright and semidull coal (Table 2), and coal structures of each delamination of coal seam No. 15 are all from types of primary texture to cataclastic texture, which are advantageous to preservation of H S generated from the buried and evolution stage of coal seam No. 15 and provide prerequisite for HjS abnormity in certain areas of coal seam No. 15. 

Coal lithotypes represent the macrostructure of coal and are, in fact, descriptive of the coal. A piece of coal will usually exhibit a definite banded appearance due to the accumulation of different types of plant debris during the formation of the organic sediment (White, 1911 Thiessen, 1931 Muller et al., 1990 ... 

Microlithotypes The microscopic analogs of the coal lithotypes and, hence, represent a part of the fine microstructure of coal associations of coal macerals with the proviso that the associations should occur within an arbitrary minimum bandwidth (50 pm, 50 x 10 mm). 

Fusain is fossil charcoal, a coal lithotype sometimes called mother-of-coal . Fusain is dominated by the inertinite maceral group (see coal) and composed of carbon rich, partially oxidised plant remains. The material has no fuel value but produces a velvety black pigment, similar to charcoal. However, this can also refer to a charcoal crayon made of the wood of the spindle tree (Euonymus europaeus L.), called in French fusain, and drawings made thereof (OED, 2002, citing nineteenth century examples). 

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