Chapter 4 - Coal

Transformation of inherent and extraneous minerals in feed coals of commercial power stations and their density-separated fractions

Computer-controlled scanning electron microscopy of minerals in coal—Implications for ash deposition

Elements other than organically derived and bound C, H, N, O, and S constitute mineral matter in coal. Mineral matter may consist of discrete minerals such as calcite, quartz, clays, and pyrite, and/or organic compounds that contain organically bonded elements such as Ca and CI. Processes that may affect the association and content of mineral matter are operable from the initial peat-forming stage to the time of utilization of the coal. However, the objective of this paper is to discuss some of the various geologic processes that may influence content and associations in unmined coal.

Chemical and mineralogical composition of Kathara Coal, East Bokaro Coalfield, India

Effect of coal minerals on the thermal treatment of aromatic ethers and carbonyl compounds

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of mineral matter particle size on ash particle size distribution during pilot-scale combustion of pulverized coal and coal-water slurry fuelsSharon Falcone Miller and Harold H. SchobertCite this: Energy Fuels 1993, 7, 4, 532–541Publication Date (Print):July 1, 1993Publication History Published online1 May 2002Published inissue 1 July 1993https://pubs.acs.org/doi/10.1021/ef00040a014https://doi.org/10.1021/ef00040a014research-articleACS PublicationsRequest reuse permissionsArticle Views301Altmetric-Citations16LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

The general aims of this research are to provide a fundamental scientific basis for the physical understanding and reliable calculation of radiative heat transfer in coal combustion systems, particularly as its influenced by the presence of inorganic constitutents deriving from the mineral matter in coal.

During combustion of coal a significant amount of sulfur may be retained in ash due to the reactions between mineral matter in coal and sulfur oxides. This process is known as sulfur self-retention and its significance lies in the fact that a part of sulfur oxides, one of the main pollutants during combustion of coal, is not released in the atmosphere. Sulfur self-retention is influenced by parameters that depend on coal characteristics and combustion conditions. The interest for this process was enhanced with the introduction of fluidized bed combustion (FBC) technology since the temperatures and other conditions are favorable for sulfur self-retention. Investigation of this process, primarily modeling, is the subject of this work. The presented model is based on the previously developed model for the combustion of porous char particles under FBC conditions, along with a changing grain size model of sulfation of the CaO grains dispersed throughout the char particle volume. Incorporating the phenomena of sintering, reduction of the produced CaSO4 with CO, thermal decomposition of the produced CaSO4, as well as allowing for the different reactivity of various forms of calcium make major improvements of the model. A temperature dependent relation for the CaO grain radius takes sintering into account. Reductive and thermal decomposition were taken into account by the corresponding reaction rate constants of the Arrhenius type. The reactivity of the calcium forms in coal was considered by different initial radius of the CaO grains. The model was verified by the experimental results of sulfur self-retention of three Serbian coals during combustion in a fluidized bed combustion reactor. The comparison with the experimentally obtained results showed that the model can adequately predict the levels of the obtained values of sulfur self-retention efficiencies, as well as the influence of temperature, coal type and coal particle size.

The kinetics of the coal to hydrogen conversion can be significantly enhanced by introducing catalysts. The catalysts are, however, commonly deactivated by irreversible interaction with mineral matters in coal. This work addresses hydrogen production via steam gasification of ash free coals. Following the production of ash free coals (AFCs) derived from various raw coals (brown, bituminous, and coking coal), fixed-bed steam gasification of the AFCs was performed as a function of temperature and which was compared with one another and also with that of the matching raw coals. In the absence of a catalyst, AFCs produced from different parent coals exhibited similarly low gasification reactivity, comparable to a high rank coal (coking coal) at 700 °C. As expected, the reaction became faster with increasing temperature in the range, 700–900 °C. The steam gasification of AFCs was highly activated by K2CO3 above 700 °C. It was very likely that water–gas shift reaction associated with the gasification of AFCs was also catalyzed.

Erratum to “A provenance study of mineral matter in coal from Appalachian Basin coal mining regions and implications regarding the respirable health of underground coal workers: A geochemical and Nd isotope investigation” [Int. J. Coal Geol. 94 (2012) 123–136

The computer controlled SEM has been used extensively to study mineral matter in coals and residues from solvent refined coals (SRC). Both dispersed powders and polished sections have been studied. The dispersions have been made on beryllium substrates using the camphor-napthalene (1) and also frozen distilled water sublimination techniques. The polished sections have been prepared by vacuum impregnating the samples with a thermo-setting resin. To achieve some contrast in the electron back-scattered (EBS) signal, a cobalt-rich hardener has been used with the resin. With an inverted EBS signal the coal grains appear brighter than the background.The automated SEM recognizes a grain of coal or other feature of interest by using the fact that a signal (EBS, SEI, etc.) from the feature is brighter than the same signal from the background material. The SEM determines the average diameter of the particle by summing the lengths of eight diameters taken every 22.5° and dividing by eight.

The influence of intense preliminary mechanical processing in a disintegrator on the conversion of the mineral matter of Kuznetsk black coal was determined. With the use of X-ray spectral fluorescence analysis and a method of coal sample separation based on density, a significant redistribution of the mineral components with the use of an energy-intensive mill (disintegrator) was found in comparison with standard mills utilized in heat-power engineering in terms of both particle-size fractions and density. Crushing in the disintegrator leads to a more uniform distribution of mineral substances over the fractions. A small fraction becomes enriched in mineral elements such as calcium- and iron-containing minerals bound to the organic matter. The separation based on density showed that crushing in the disintegrator leads to a significant decrease in the concentration of iron-containing minerals and a decrease in the portion of organic components in the heavy fraction, as compared with crushing in a ball–tube mill.

The effects of the constituents of mineral matter in brown coals from different deposits of Kansk-Achinsk, Lenaand from Yallourn Basins on the structural parameters and steam gasification reactivities of respective coal chars at moderate temperature and at low and high pressure were studied in this paper. The data on how the preliminary decationization with diluted hydrochloric, acetic and sulphuric acids affect char gasification reactivities are presented. The importance of surface area and crystallinity of chars and the presence of naturally occurring metals on gasification reactivity is considered. Quantitative correlations between the calcium contents and the extents of gasification are revealed. The gasification results obtained in a flow reactor with steam stream and in an autoclave reactor at high pressure of gaseous products are compared. The catalytic effect of dispersed calcium oxide-carbonate particles produced from the naturally occurring calcium containing carboxylates was shown to be a key factor for char gasification reactivity, the effect in the flow reactor being much larger as compared to that in the autoclave reactor. This was mainly related to different forms of catalytically active calcium species and to the composition of the gaseous reaction mixture.

The average concentrations of trace elements in coals from the South Fergana, North Sos’va, Kizelovsk, South Yakutian, Transbaikalia, Pechora, and Zyryansk deposits and some deposits of the Kuznetsk and Primor’e Basins are compared. The degrees of trace element concentration were calculated both on a total coal weight basis (Q i ) for individual basins and on a mineral matter basis (Q ) with reference to Clarke numbers in clay rocks. Ratios between the concentrations of typomorphic trace elements on a coal mineral matter basis were calculated for the deposits of basins with different geologic-geochemical formation conditions (X ); the concentration ratios between the pairs of typomorphic trace elements in the considered coal basins (Z i ) were also calculated. Typomorphic elements are the trace elements with Q i > 1.4 or Q > 2. Coal basins of different origin have different numbers of typomorphic trace elements calculated in terms of the parameter Q i and, to a lesser degree, the parameter Q . Coal basins differ considerably from each other in both the ratios between the average concentrations of the same trace element in the mineral matter of coal (parameter X ) and the ratios between the concentrations of two different trace elements (parameter Z i ). In the basins under discussion, the mineral matter of coals from formations created in areal rift genesis regions, in particular, Triassic-Jurassic coals and, to a lesser degree, Carboniferous coals, are enriched in trace elements to the greatest extent. Coals from subgeosynclinal formations have a maximum number of typomorphic trace elements (in terms of the average concentrations in the mineral matter), practically the majority of the test elements with the exception of Nb, Sn, Ni, and Sc. Coals from young mobile platforms are characterized by a similar number of typomorphic trace elements with the exception of Nb, Zn, Y, and Yb. Coals from geosynclinal formations have a somewhat smaller set of typomorphic trace elements, whereas a minimum number of typomorphic elements is characteristic of coals from platform basins.

The genesis of coal from the viewpoint of coal petrology