Mineral Matter In Coal Research Articles

Iron-Catalyzed Coal−Tire Coprocessing. Influence on Conversion Products Distribution

This paper reports the hydrocoprocessing of a low-rank coal and rubber from discarded tires in the presence and absence of Red Mud as an iron catalytic precursor. A subbituminous coal from northeast Spain is processed with ground rubber from a mixture of old tires, free of steel thread and textile netting. This is the first time that the influence of the hydrogen pressure on conversion products is deeply analyzed. In addition, the influence of the coal−tire ratio on conversion and product distribution is also studied. Experiments have been conducted in small tubing bomb reactors, held by an oscillation device, and immersed in a preheated fluidized sand bath. Temperature (400 °C) and the reaction time (30 min) were kept constant. The THF-soluble and n-hexane-soluble products have been characterized by thin layer chromatography. Gas and asphaltene formations are commented, and THF insolubles are thoroughly studied following the iron evolution, both from coal mineral matter and those added as catalyst precur...

97/03380 Surface characterization of mineral matter in an Australian bituminous coal (Whybrow seam, NSW) using X-ray photoelectron spectroscopy and laser ionization mass analysis

97/03380 Surface characterization of mineral matter in an Australian bituminous coal (Whybrow seam, NSW) using X-ray photoelectron spectroscopy and laser ionization mass analysis

97/01416 Emissions of hazardous substances in production of refractories

Pilot-scale pulverized-coal combustion experiments with two western Canadian coals have shown that the combustion efficiencies of the coals were inversely related to the inert contents of the coals, i.e. semi-fusinite, fusinite and oxidized vitrinite. These macerals were found to persist through the flame in a partially reacted form. The burn-out of a coal with an inert maceral content over 50% was unaffected by normal changes in combustion conditions; the same changes were successful in improving the burn-out of a coal containing less than 40% inert macerals. Coals with high inert maceral contents produce fly-ash with high levels of unburnt carbon and will require a combination of higher temperatures and higher excess-air levels and longer residence times to achieve combustion efficiencies similar to those of coals with higher reactive-maceral contents. The association of resinitic and bituminous materials with the mineral matter in the Canadian sub-bituminous coal indicated that macerals which contribute significantly to ignition and flame stability are discarded as a washery reject.

97/00844 Contribution of mineral matter to low temperature liquefaction mechanisms

The objective of this work was to evaluate the nature and distribution of coal mineral matter in both untreated and demineralized coal, and consider the influence of these compounds by assessing their possible catalytic effects.

Beneficiation of Indian coal by chemical techniques

The high ash content of Indian coals affects the efficiency of operation (when used as fuel in boilers/furnaces) and also the quality of product (coking coals used for producing metallurgical coke). The experimental work conducted takes cognizance of the high silica content of the ash (over 50%) and aims at a selective attack on the silica portion, in order to achieve a substantial reduction in the mineral matter of coal. This was achieved by using certain fluxing agents for producing hydrofluoric acid in situ in the coal bed. The ash content of high ash Western coal fields coal was found to be reduced from 32.9 to about 10% after the treatment.

About this title

Despite the decline in the coal mining industry across Europe during the last decade, coal continues to supply a major part of the growing global energy requirements, particularly in the developing countries. During this period there has been a shift in coal extraction techniques from deep underground mines to open pit mines, reflecting cheaper production costs in a market economy. It seems probable that the European coal industry is now entering a period of stability. However, the change to opencast mining has highlighted environmental issues and the need to solve these problems. This volume presents 39 papers written by coal scientists in the forefront of European coal research. The papers cover a wide spectrum of coal geology and technology, with sections on regional coal reserves, coal basin tectonics and stratigraphy, coal petrology and palaeontology, mineral matter in coal and the environment, mining geophysics, coal technology and coalbed methane. Many of the studies describe coal deposits from Central and Eastern Europe, some of which are not well known in the west, so that the papers and included references will provide an invaluable data source. This book will be of value to all coal scientists in both the extraction and energy industries and to academics. It will also be a useful reference for students at both undergraduate and postgraduate levels.

Surface characterisation of mineral matter in an Australian bituminous coal (Whybrow seam, NSW) using X-ray photoelectron spectroscopy and laser ionisation mass analysis

X-ray photoelectron spectroscopy (XPS), laser ionisation mass analysis (LIMA) and X-ray diffraction (XRD) have been used to investigate composition, occurrence and association of mineral species on polished, fractured and powder surfaces of an Australian bituminous coal from the Whybrow seam, Saxonvale Colliery, New South Wales. XPS on raw coal samples revealed composition and the likely mineral types present which were concentrated predominantly in different bands of the coal. This was further confirmed using a new rapid and selective LIMA experimental method which is devised and optimised for in situ mineral particle identification. A series of mineral species occurring as fine, distributed inclusions were rapidly identified using LIMA, including quartz, pyrite, and a number of clays and carbonates. In addition, evidence for organic and inorganic sulfur species and some trace elements were also obtained from individual particles. Mineral identifications were confirmed by ashing the samples and analysis using XRD. This work highlights the advantages of using XPS and LIMA as complementary methods for coal mineral study.

96/06765 Mineral matter in UK power station coals. Distributions and associations

96/06765 Mineral matter in UK power station coals. Distributions and associations

Some relationships between coal rank and chemical and mineral composition

Some relationships between coal rank (C daf) and the mineral and chemical composition of coals and their high-temperature ashes worldwide were studied. Low-rank coals (C daf <75 wt%) are relatively rich in moisture, volatile matter, ash, H, N, O and S, and their ashes are abundant in MgO, CaO and SO 3. Coal ashes derived from higher-rank coals demonstrate increased contents of SiO 2, Al 2O 3, Fe 2O 3, K 2O, Na 2O and TiO 2. It was found that the occurrence, abundance and origin of mineral matter in coal depends on the coal rank to a certain extent. Coals enriched in illite, mica, chlorite, spinel, dolomite, siderite and hexahydrite, and partly in quartz, kaolinite and Fe oxyhydroxides, are of higher rank, while coals with increased contents of montmorillonite, feldspars, zeolite, Al oxyhydroxides, calcite, pyrite, gypsum and Fe, Al and Ba sulfates are of low rank. Higher-rank coals are abundant in ash-forming elements associated with probable detrital minerals, while low-rank coals show enrichment in ash-forming elements associated with probable authigenic minerals and organics. Various processes related to some changes in inorganic matter during coalification are discussed. The metamorphic progression and leaching behaviour of different minerals, phases and elements from low- to high-rank coals have resulted in essential changes in the mineral and chemical composition of coals.

STUDIES TOWARDS THE DEVELOPMENT OF EFFECTIVE TECHNIQUES for DEASHING (DEMINERALISATION) OF COALS

ABSTRACT The direct use of coal for power generation may cause pollution from the generation of fly ash and toxic mineral matter contents and due to the green house house effect, if not controlled. There is a need to further develop efficient and cost- effective techniques of coal cleaning. However,it is important to analyse the coal mineral matter directly to understand its chemical nature. The nature of bonding and association been organic matter of coal and various constituents of mineral matter may be understood. The state of aggregation of mineral matter and the studies of associative forces between mineral matter components might help in developing reagents to clean coal. Swelling behaviour of coal and its effect on dissociation of mineral matter may be studied. A real break- though in the development of efficient and cost- effective coal cleaning technologies may be expected only after studying the nature of mineral matter constituents of coal and their interaction with coal swelling reagents when ...

96/04622 Mineral matter and trace elements distribution in Late Permian coal, Collie Basin, Western Australia

96/04622 Mineral matter and trace elements distribution in Late Permian coal, Collie Basin, Western Australia

A scanning electron microscope method for automated, quantitative analysis of mineral matter in coal

Quantitative mineralogical analysis has been carried out on a series of nine coal samples from Australia, South Africa and China using a newly-developed automated image analysis system coupled to a scanning electron microscope. The image analysis system (QEM ∗ SEM) gathers X-ray spectra and backscattered electron data from a number of points on a conventional grain-mount polished section under the SEM, and interprets the data from each point in mineralogical terms. The cumulative data in each case was integrated to provide a volumetric modal analysis of the species present in the coal samples, expressed as percentages of the respective coals' mineral matter. Comparison was made of the QEM ∗ SEM results to data obtained from the same samples using other methods of quantitative mineralogical analysis, namely X-ray diffraction of the low-temperature oxygen-plasma ash and normative calculation from the (high-temperature) ash analysis and carbonate CO 2 data. Good agreement was obtained from all three methods for quartz in the coals, and also for most of the iron-bearing minerals. The correlation between results from the different methods was less strong, however, for individual clay minerals, or for minerals such as calcite, dolomite and phosphate species that made up only relatively small proportions of the mineral matter. The image analysis approach, using the electron microscope for mineralogical studies, has significant potential as a supplement to optical microscopy in quantitative coal characterisation.

The microscopic nature of coal fly ash particles investigated by means of nuclear microscopy

Individual fly ash particles collected at the outlet of a pilot electrostatic precipitator of a coalfired power plant have been analysed by a proton microprobe. Major and trace element concentrations have been obtained for about one hundred particles in the 0.5–5 μm size range. As a result of the combustion of the different components of the mineral matter in the parent coal, particles can be grouped in seven classes showing characteristic matrix compositions and different trace element concentrations. The relative abundances of these groups seem to have a size dependence. Trace elements are found to be non-uniformly distributed over all particles: a size dependence as well as some preferential association with the particle matrix have been found. Enriched concentrations of potentially toxic elements exist on smaller, most respirable particles examined in this study. Possible reasons for this are suggested.

95/03268 Influence and transformation of coal mineral matter during hydrogenation

95/03268 Influence and transformation of coal mineral matter during hydrogenation

Chemical reactivity of coal under Friedel-Crafts reaction conditions: effect of nature of solvent, alkylating agent and catalyst on extractability of coal through a complex series reaction (ATD 3 reaction)

Coal is a complex macromolecule of predominantly aromatic character. The reaction of coal under Friedel-Crafts conditions is not a simple alkylation but involves a series of complex reactions. The molecular dynamics of coal molecules under such conditions can be studied by FT-i.r. spectrometry, elemental analysis, swelling and extraction. Several alkylating agents such as alkenes, alcohols, alkyl halides, phenol and alkane were used in solvents such as CS 2, pyridine, quinoline, nitrobenzene, liquid paraffin, anthracene oil and tetralin in catalysed and uncatalysed reactions. The mineral matter in coal was found to catalyse these reactions. Extraction enhancement was used as a measure of the effectiveness of reactions such as degradation, disintegration and transalkylation of coals. The reaction of coal with alkylating agents under Friedel-Crafts conditions was found to be a series reaction:alkylation-transalkylation-dehydrogenation-degradation-dissociation (ATD 3 reaction).

Influence and transformation of coal mineral matter during hydrogenation

Mineral matter of coals of different origin was analysed by several techniques (XRD, AAS and SEM-EDX) and mineral transformations during coal hydrogenation under different experimental conditions were studied. SEM-EDX provides more detailed information on the nature and distribution of these materials and their inorganic-organic relations, mainly revealed as the association of distinct cations (Ca, Fe, Mg, K, Al) with the acid groups of the coal. Fe, Ca and Al contents were determined by AAS and related to coal reactivity. The mineral matter acts as a catalyst for coal hydrogenation, mainly owing to its pyrite content, which has two effects: one as heterogeneous catalyst, the other giving rise to H 2S which in turn can act as a homogeneous catalyst.

95/01204 Molten caustic leaching at low caustic/coal ratios

Molten caustic leaching (MCL) of coal has been studied under a variety of conditions, many of which studies have been conducted using a large excess of liquid caustic (3:1 caustic/coal or higher) so that, with stirring, coal is suspended in it. This provides a uniform temperature throughout the mixture and is preferred for chemical research. Some development studies have made use of lower ratios of caustic, such as TRW`s 20 lb/hr kiln work by Meyers, and the studies of Chriswell and Markuszewski at Ames Laboratory and by Kusakabe in Japan. In the Japanese work, Illinois No. 6 coal was impregnated with mixed KOH and NaOH (52:48 parts by weight) from an aqueous solution to give 51 wt% caustic on the dry coal which after MCL treating, 2 hr at 375{degrees}C, produced a coal having only 0.50 wt% total sulfur. Less caustic should help in reducing the cost of an MCL process. Moreover, at high ratios much more caustic is present than necessary to form salts of sulfur and mineral matter in coal. We have calculated that to form the sodium salts of the sulfur and mineral matter present in an 8% ash, 4.2% sulfur, Pittsburgh No. 8 coal would takemore » about 0.15 parts of sodium hydroxide for one part of dry coal. This does not take into account carbonate formation nor cleavage of carbon-oxygen bonds which also can occur. The objectives of this work were to examine molten caustic leaching under conditions that could be used for commercial chemical coal cleaning. This has meant using low levels of acid water and caustic.« less

Sulfur transformations during pyrolysis of a high sulfur Polish coking coal

A coking coal containing 4.9 wt%, db, of sulfur was subjected to pyrolysis at 330–1700°C in an atmosphere of evolved gases. The changes in the forms of sulfur were determined by wet chemical analysis. Scanning electron microscopy (SEM) combined with X-ray microanalysis were used to monitor the reduction of pyrite during coal pyrolysis and the retention of sulfur by the alkali constituents of the coal mineral matter. It was found that between 360 and 700°C the conversion of pyrite to ferrous sulfide occurred. This was accompanied by a high accumulation of organic sulfur in the char. Calcite and siderite present in the mineral matter of the coal were responsible for a further increase in sulfide sulfur. Spherical agglomerates composed of calcium and iron sulfides were detected. Above 1000°C sulfur re-enrichment on the surface of ferrous sulfide particles was observed. Pyrolysis conducted at 1700°C did not remove the sulfide sulfur completely. Organic sulfur was also present in a significant amount. The roles of alkali components and an environment rich in volatile sulfur compounds in sulfur retention during coal pyrolysis are discussed.

The impact of mineral matter in coal on its combustion, and a new approach to the determination of the calorific value of coal

To estimate the influence of mineral matter in coal on coal combustion, fluidized bed combustion (FBC) and pulverized coal combustion (PCC) were simulated by simple models. The theoretical calorific values of some hypothetical coals of different rank and mineral matter content were calculated. The calculated calorific values of coals tend to decrease with increasing mineral matter content. This is due to endothermic reactions of decomposition of the mineral matter as well as the heat capacities of such minerals. The resulting combustion energy loss can be very large. A new approach to the calculation of the calorific value of coals is also proposed.

The impact of mineral matter in coal on its combustion, and a new approach to the determination of the calorific value of coal

The impact of mineral matter in coal on its combustion, and a new approach to the determination of the calorific value of coal