Liptinite macerals

Liptinites generally make up about 5%-15% of most North American coals. They are usually more abundant in the Appalachian coals than any other US coals except cannel and boghead types where they dominate. At a reflectance of 1.35-1.40, most of the liptinite macerals disappear from coal. Cannel and boghead coals are petrographically distinguished from humic coals by both their maceral composition and texture. They have an abundance of liptinite macerals (sporinite in can-nels and alginite in boghead coal) and a relative low level of vitrinite and inertinite macerals. 

Sporinite is the most common of the liptinite macerals and is derived from the waxy coating of fossil spores and pollen. It generally has the form of a flattened spheroid with upper and lower hemisphere compressed until they come together. The outer surface of the sporinite macerals often shows various 

FIGURE 4.3 Photomicrographs of macerals from western Canadian low-volatile bituminous coal V, vitrinite F, fusinite Sc, sclerotinite SF, semifusinite and MM— massive micrinite or macrinite. 

FIGURE 4.4 Photomicrographs of macerals from Canadian coals (a) Alberta medium-volatile coal SF, semifusinite V, vitrinite and F, fusinite. (b) Alberta subbituminous coal V, vitrinite F, fusinite SF, semifusinite and E, exinite. (c) Same as in (b) but under fluorescent light, (d) Sydney, Nova Scotia high-volatile bituminous coal V, vitrinite M, micrinite and E, exinite. 

FIGURE 4.5 Representation of a cross-sectional view through a megaspore. (From Murchison, D. and Westoll, T.S., Eds., Coal and Coal-Bearing Strata, Elsevier, New York, 1968.) 

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Macerals. Coal parts derived from different plant parts, are referred to as macerals (13). The maceral names end in "-inite" as do the mineral forms of rocks. The most abundant (about 85%) maceral in U.S. coal is vitrinite, derived from the woody tissues of plants. Another maceral, called liptinite, is derived from the waxy parts of spores and poUen, or algal remains. The liptinite macerals fluoresce under blue light permitting a subdivision based on fluorescence. A third maceral, inertinite, is thought to be derived from oxidized material or fossilized charcoal remnants of early forest fires. 

The behavior of macrinite and micrinite in industrial processes is not clearly understood. As stated above, many U.S. petro-graphers treat both of these constituents as MinertM coal constituents. On the other hand, overseas workers have observed that micrinite may not be inert during carbonization. Because some micrinite appears to have been generated during the progressive coalification of the liptinite macerals, it might, instead, be quite reactive. 

The reactive role of liptinite macerals in liquefaction has been partially documented (50,68). However, recent work has shown that unaltered sporinite often is encountered in the residues from both batch and continuous liquefaction runs. For example, sporinite was a common component in the residues of a high volatile A bituminous coal after hydrogen-transfer runs at 400° for 30 minutes (70). In spite of the relative unreactivity of the sporinite in this instance, the vitrinite clearly had reacted extensively because vitroplast was the predominant residue component. The dissolution rate of sporinite from some coals, even at 400°C, may be somewhat less than that of vitrinite. 

Block coals" are dull coals that break into large blocks because they have fewer vitrain and clarain bands, but have a composition higher in liptinite macerals, which are tough. 

Two distinct types of fusible material occur in coals. One type is aliphatic-rich and associated with the liptinite macerals and the other is contained in the aromatic-rich macerals and particularly the vltrinites of bituminous coals. 

The technique also yields quantitative spectra that are characteristic of both the individual maceral type and the rank of the coal. It is now also well established that all of the liptinite macerals (coal components derived from the resinous and waxy plant material) and many of the vitrinite macerals (coal components derived from woody tissue of plants) will fluoresce, and that some recently discovered liptinite macerals can only be identified by their fluorescence properties. 

In a study of the fluorescence properties of the Brazil Block seam (Parke Co., IN), a somewhat different approach was used. In this case, about a hundred individual spectra were taken on a variety of fluorescing liptinite macerals. Although the macerals from which the spectra were tkane were not identified at the time of measurement, photomicrographs in both normal white-light and fluorescent light were taken for documentation. The spectral parameters for each spectrum were calculated and these data were subjected to cluster analysis to test the degree to which the... 

Figure 12 gives an example how the content of volatile matter and that of the hydrogen-rich liptinite maceral correlate. 

Q. o macerals, I = inertinite 1 macerals, L liptinite macerals, S Mod. = organic sulfur ... 

The major petrographic feature of the liptinite group of macerals is that they all have a reflectance that is lower than the vitrinite macerals in the same coal. This group of macerals is very sensitive to advanced coalification and the exinite macerals begin to disappear in coals of medium-volatile rank and are absent in coals of low-volatile rank. When the exinite macerals are present in a coal, they tend to retain their original plant form and thus they are usually plant fossils phyterals). The phyteral nature of the liptinite macerals is the main basis on which they are classified. 

The third liptinite maceral is resinite, which is a term generally employed to include all of the resinous constituents of coals and also includes the resinified essential oils of lignites and bituminous coals. The fourth exinite maceral is alginite, which is formed from the remains of algal bodies and is, in fact, the principal component of boghead coals (torbanites). 

On the other hand, micrinite is composed of smaller material and is believed to be a maturation product of protoplasm. Micrinite occurs as very fine granular particles of high reflectance and is commonly associated with the liptinite macerals but sometimes gives the appearance of actually replacing the liptinite. Micrinite is frequently, but not always, found in association with microspores. It is also found in the sapropelic (cannel and boghead) coals. Both macerals are virtually structureless. 

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