ISSN 1068364X, Coke and Chemistry, 2013, Vol. 56, No. 9, pp. 316–318. © Allerton Press, Inc., 2013. Original Russian Text © V.P. Ivanov, I.S. Bondarenko, 2013, published in Koks i Khimiya, 2013, No. 9, pp. 16–19.

COAL

Differences between Mineral Coal and Extracted Coal V. P. Ivanov and I. S. Bondarenko Kuznetsk Center, OAO VUKhIN, Novokuznetsk, Russia email: [email protected] Received July 17, 2013

Abstract—A distinction is proposed between mineral coal and extracted coal. Mineral coal is a complex nat ural composite that is found in underground beds, while extracted coal is created from mineral coal in work ing those beds. It is important to keep in mind that mineral coal is created by natural processes, whereas extracted coal is produced by human activity. Keywords: composites, mineral coal, extracted coal DOI: 10.3103/S1068364X13090032

In practice, the concepts of mineral coal and extracted coal are regarded as synonymous. That con fuses our understanding of coal and hinders its classi fication for purposes of identification and optimal use. We realize that unraveling these terms might seem a perplexing task. However, it offers the prospect of eliminating indeterminacy in our understanding of two different materials. “Mineral coal is a hard combustible sedimentary rock of plant origin, with some quantity of mineral impurities, that appears in the form of beds or layers among other sedimentary rock,” according to the dic tionary definition [1]. We might add that mineral coal is studied in the geological search for mineral wealth. After calculation of the reserves, appropriate taxation of the corresponding mineral extraction is deter mined. Extracted coal is a raw material, which is the prod uct of earlier work (extraction) and will be later trans formed in various ways [2]. Hence, extracted coal is a product of human activity that has been removed from a bed of mineral coal. The extracted coal may be regarded as a derivative of the mineral coal. In terms of lithological and environmental analy sis, the mineral coal from a particular bed is a coalfor mation facies—that, is a set of physical and geological conditions associated with the accumulation of coal matter [1]. Therefore, the coal extracted from a single bed may reflect not only the properties of the mineral coal but also the conditions characterizing the bed and the extraction technology. When the extracted coal corresponds to two or more types of mineral coal, the blending process must also be taken into account, and the blend, which is an artificially produced coal sample, may be character ized by several specified parameters (a coal batch) or by a single specified parameter (say, the ash content)

when coal extracted from different beds is stored in a single stack (a coal blend). It is clear that mineral coal is a material produced by nature, while extracted coal is a material produced by human activity. This difference is important, espe cially in ranking coal. Note that State Standard GOST 25543–88 recom mends rank assignment only for mineral coal from beds, levels, store segments, etc. If a blend contains extracted coal with different ranks, the rank assign ment for the blend is established by calculating the mean of the parameters for the individual coal compo nents. An ambiguity in the standard may be seen here, since the blending of coal of different ranks in enrich ment is only permitted with the consent of the cus tomer (coke plant). However, we know that, at many mining facilities, the coal from different beds will be very different. At the enrichment facility, however, constraints are established on blending, even if coal from a single mine or even a single bed is sent for enrichment. In other words, at the mining enterprise, extracted coal of different ranks may be mixed, whereas at the enrich ment facility they cannot, but in both cases a coal blend is formed from coal with different coking prop erties. What do mineral coal and extracted coal have in common, and why should we distinguish between them? Note that a material is usually regarded as the stuff from which some product will be made [3]. In coal extraction, a coal mass is produced; from that coal mass, extracted coal is produced; from the extracted coal, enriched coal (coal concentrate) is produced; and so on. All these types of coal are composites. In nature, this is a common structure.

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DIFFERENCES BETWEEN MINERAL COAL AND EXTRACTED COAL Mineral coal consists of sedimentary rock with traces of the initial plant matter and the conditions in which it was formed

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Extracted coal consists of mineralcoal components with different initial plant matter and different processing by humans

A natural composite (a firstorder blend)

An artificial composite (a secondorder blend)

The goal in studying natural coal composites is todetermine their capabilities in terms of clinkering, coking, enrichment, and so on

The goal in studying artificial coal composites is to determine the behavior of the natural composites: their clinkering, coking, enrichment, and other properties

Comparison of mineral coal and extracted coal.

Mineral coal is a composite of natural organic and inorganic structures. Extracted coal is more complex in composition: it is a blend of natural coal composites or extracted coal composites and also a mixture of sig nificantly different natural organic and inorganic structures. Note that we may expediently speak of uni formity and nonuniformity in the case of identical conditions of formation and time. Hence, in natural composites, it is important to determine the ability of the components (macerals, etc.) to interact; in artificial composites, it is impor tant to determine the degree of interaction of the ini tial natural composites. In other words, we first deter mine the capabilities of the mineral coal; and then we determine the capacities of the extracted coal in which those components are present. In the figure, we present a comparison of mineral coal and extracted coal. Confusion may arise when using the term compos ite, since it is often applied to all complex systems that contain several components. However, the science of composites developed with a view to improving the properties of materials—especially polymer compos ites—allows us to better understand coal at any stage of its formation. In nature, composites are commonly found. The current definition of a composite rests on the following stipulations [4]. 1. A composite must be a combination of at least two different materials, separated by a clear boundary. 2. The components of a composite occupy adjacent volumes. 3. The properties of the composite are different from those of any of its components. COKE AND CHEMISTRY

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Mineral coal, a complex rock consisting of many organic and inorganic components, may correctly be regarded as a natural composite. This approach is especially important since, in current practice, the concepts of coal as a mineral in a rock bed and as a coal product in blended form are used interchangeably. Mineral coal consists of natural organic (vitrinite, inertinite, semivitrinite, liptinite) and inorganic (quartz, sulfides, clay minerals, carbonates) compo nents, which have different physicochemical, tech nological, and mechanical properties. Therefore, coal in deposits, which is a nonuniform and complex material, may be regarded as a natural coal composite (a firstorder composite). By contrast, extracted coal is an artificial coal composite (a secondorder com posite). The composite structure of mineral coal is deter mined by the composition of the initial plant matter, which, in turn, is a composite made up of various structural elements (conductive, skeletal, coating, and other elements) with different physicochemical prop erties at the cellular level, on account of the difference in the organic compounds: waxes, tar, acids, etc. (Table 1). Coal contains macerals (in the organic mass), min eral inclusions, and incidental rock. Accordingly, the concept of coal composites per mits a new approach to the creation of artificial blends for the production of blastfurnace coke. From this perspective, the investigation of the composition and structure of mineral coal and extracted coal is associ ated with the introduction of new methods, new terms, and new parameters for coal (such as indus trial–genetic, technological, and consumer charac teristics), as well as unambiguous new standards for the ranking of coal.

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Table 1. Elements of coal’s composite structure Factor

Constituent elements

Plant matter Plant structures Tissue types Coal Petrographic composition Macerals: vitrinite semivitrinite inertinite liptinite Mineral inclusions

Composition of phytocenoses: trees, shrubbery, bushes, grass, moss, algae Roots, stems, leaves, flowers, fruit Covering tissue, mechanical tissue of skeletal system, conducting tissue, excretory tissue Basic coal components: organic mass, macerals, incidental rock Vitrinite, semivitrinite, inertinite, liptinite, and mineral inclusions Telinite, collinite, vitrodetrinite Semitelinite, semicollinite Semifusinite, macrinite, fusinite, sclerotinite, intertodetrinite, micrinite Sporinite, cutinite, resinite, suberinite, alginate, liptodetrinite Clay minerals, iron sulfides, carbonates, silicon oxides, etc

Table 2. Comparison of the microcomponent content of Zh and K coal Donets Basin

Microcom ponents

Zh coal

Vt Sv F L

0.73–1.07 1.00–1.40 1.63–2.27 0.35–0.51

K coal

Kuznets Basin Zh coal

K coal

1.18–1.38 1.1 1.34 1.33–1.52 1.42–1.81 1.73–2.23 1.73–2.86 2.12–2.69 2.22–3.32 0.94–1.08 – –

The significance of such a new approach may be illustrated by means of an example. Consider the organic component of the coal—specifically its microcomponents. Each microcomponent has a par ticular range of properties; for instance, the vitrinite reflectance is significantly different in isometamor phic coal from different basins. Data for Ro in vitrinite, semivitrinite, fusinite, and liptinite from the Donets and Kuznets basins were presented in [5] (Table 2). We see the difference in microcomponents within a single metamorphic stage, at different stages, and in different basins. In extracted coal, the presence of even two nonuni form isometamorphic coals from nearby beds within a single environmental complex will greatly complicate its composition and properties. This is especially true of Balakhonsk coal from the Kuznets Basin—for example, Vt = 58% for coal from the IV Vnutrennii bed and Vt = 45% for coal from the IV Kharakternyi bed in the Krasnogorskaya mine, with Ro = 1.22–1.24%. Note that this is composite coal simply in terms of the vitrinite content. However, such coal is also differently enriched, has different ash composition, and has dif ferent clinkering properties on account of the vitrinite content.

Thus, extracted coal reflects the properties of its individual coal components, which are not averaged out but rather interact in complex ways. The mutual influence of these properties will depend on the kinet ics of the thermochemical reactions and the decom position products of particular components in the coal blends at different temperature intervals if we consider their behavior in bed coking. Therefore, in the thermal decomposition and synthesis of coal components within the blend, the transformation of the coal blend to coke will pass through slow and fast stages, which will be reflected in the structure of the coke formed. In this brief article, we have touched upon some important terminological issues. In future publica tions, we intend to focus on individual aspects of the topic, with the publication of research data regarding mineral coal and extracted coal. REFERENCES 1. Geologicheskii slovar’ (Geological Dictionary), Mos cow: Gosgeoltekhizdat, 1960. 2. Sovetskii entsiklopedicheskii slovar’ (Soviet Encyclope dic Dictionary), Moscow: Sovetskaya Entsiklopediya, 1985. 3. Tolkovyi slovar (Explanatory Dictionary), St Peters burg: Ves’, 2009. 4. http://dic.academic.ru/dic.nsf/ruwiki/16567. 5. Sarbeeva, L.I. and Krylova, N.M., Reflectance of the microcomponents of coal of different metamorphic development, Voprosy metamorfizma uglei i epigeneza vmeshchayushchikh porod (Coal Metamorphism and Epigenesis of the Incidental Rock), Leningrad: Khimiya, 1968, pp. 87–106.

Translated by Bernard Gilbert

COKE AND CHEMISTRY

Vol. 56

No. 9

2013