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Fine particles (PM 2.5 ) emitted from the stacks of the coal-fired power plants are of environmental concern since they can easily enter the human respiratory track. The detailed study of the fly ash particles using scanning electron microscope/electron dispersive spectrometry (SEM/EDX) show that fine solid spherical particles (microspheres) are contained by the large cenosphere particles (>50 μm) during the combustion process. The resulting macro particles are known as “plerosphere”, which are typically impregnated by the fine microspheres. The coal-fired power plants’ particle control devices such as the electrostatic precipitators (ESP) and baghouse filters tend to capture the large plerospheres, more efficiently. Therefore, the result of this study suggests that the containment of the microspheres by plerospheres during the coal combustion process can effectively reduce the amount of fine particles and associated elements released into atmosphere.

Fly ashes produced from Canadian power plants using pulverized coal and fluidized bed combustors were examined for their carbon content to determine their ability to capture mercury. The feed coal used in these power plants were lignite, subbituminous, high and medium volatile bituminous, their blends, and also blends of coal with petroleum coke (Petcoke). The carbon and mercury content of the coals and fly ashes were determined using the ASTM standard method and by the cold vapour atomic absorption spectrometry method. The carbon content of the fly ash was concentrated by strong acid digestion using HCl and HF. The quantitative and qualitative analyses of the carbon concentrate were made by using a reflected light microscope. The results show that the carbon content of fly ash appears to be partially related to depositional environment during coalification and to the rank of the coal. The Hg captured by the fly ash depends on the rank and blend of the feed coals and the type of carbon in the fly ash. The isotropic vitrinitic char is mostly responsible for the capture of most Hg in fly ash. The inadvertent increase in carbon content due to the blending of coal with petroleum coke did not increase the amount Hg captured by the fly ash. The fly ash collected by the hot side electrostatic precipitator has a low Hg content and no relation between the Hg and carbon content of the ash was observed. These results indicate that the quantity of carbon in the fly ash alone does not determine the amount Hg captured. The types of carbon present (isotropic and anisotropic vitrinitic, isotropic inertinitic and anisotropic Petcoke), the halogen content, the types of fly ash control devices, and the temperatures of the fly ash control devices all play major roles in the capture of Hg.

Feed coals and fly ashes from two coal-fired power plants burning Alberta subbituminous coal were analyzed for C, Cl, Hg, and S and calorific values (for feed coal only), every week for a period of 33 weeks. The feed coals used in this study were deposited in brackish water and are compared to the coals deposited in a freshwater environment. The Hg and char (unburnt carbon) content of the fly ash was monitored to determine the variation of Hg and its possible relationship to the char types in the fly ash. The feed coals have Hg content of 0.026–0.089 mg/kg and their fly ash contains 0.02–0.243 mg/kg of Hg. The C content of the fly ashes ranges from 0.15% to 0.51%. The carbon/char was separated from the fly ash using HF and HCl. Reactive vitrinitic (formed from woody part of plants) and less reactive inertinitic (natural char) chars were separated by density separations of various specific gravities using ZnBr 2 . The char is mostly reactive vitrinitic (67–80 vol.%). Both stations have similar range of C content for their respective fly ashes. However, station 2 shows a much wider range of Hg in fly ash compared to station 1. In general, the fly ash from coal deposited under brackish water environment (stations 1 and 2) appears to have same or higher Hg content for lower C content compared to the fly ash from coal deposited under fresh water environment. The calculated emitted Hg for the period of 33 weeks for station 1 is estimated to be 64–90% of the total input of Hg with an average of 74%. The calculated emitted Hg shows a more complex pattern for station 2 and falls into two groups; with group (a) showing higher enrichment index for both Hg and S. The calculated emitted Hg for this group is 43–74% with an average of 57%, indicative of more Hg being captured by fly ash, possibly due to interaction between Hg and S. In the second group (b) the emitted Hg is calculated to be 74–95% with an average of 85%. The relative enrichment of both Hg and S in group (b) is low compared to group (a), indicative of possible slight paleo-weathering of the feed coal. The present study indicates that geological parameters such as paleo weathering and also depositional environment of the feed coal may influence the Hg content of fly ash.

Fly ashes were collected from the electrostatic precipitator (ESPs) and/or the baghouse of seven coal-fired power plants. The fly ashes were sampled from power plants that use pulverized subbituminous and bituminous feed coals. Fly ash from bituminous coals and limestone feed coals from fluidized-bed power plant were also sampled. The fly ashes were examined for their mineralogies and elemental compositions. The fly ashes from pulverized low sulfur coals are ferrocalsialic, those from high sulfur coals are ferrosialic and the fly ashes from the fluidized bed coals are ferrocalcic. The concentrations of As, Cd, Hg, Mo, Ni, and Pb in fly ash are related to the S content of the coal. Generally, those feed coals with a high S content contain higher concentrations of these elements. The concentrations of these elements are also greater for baghouse fly ash compared to ESP fly ash for the same station. The S content of fly ash from high S coal is 0.1% for pulverized ESP fly ash and 7% for baghouse fly ash from the fluidized bed, indicating that most of the S is captured by fly ash in the fluidized bed. The baghouse fly ash from the fluidized bed has the highest content of Cd, Hg, Mo, Pb, and Se, indicating that CaO, for the most part, captures them. Arsenic is captured by calcium-bearing minerals and hematite, and forms a stable complex of calcium or a transition metal of iron hydroxy arsenate hydrate [(M 2+ ) 2 Fe 3 (AsO 4 ) 3 (OH) 4 ·10H 2 O] in the fly ash. Most elements in fly ash have enrichment indices of greater than 0.7 indicating that they are more enriched in the fly ash than in the feed coal, except for Hg in all ESP ashes. Mercury is an exception; it is more enriched in baghouse fly ash compared to ESP. Fly ash collected from a station equipped with hot side ESP has a lower concentration of Hg compared to stations equipped with cold side ESP using feed coals of similar rank and mercury content. Fly ash particles from fluidized bed coal are angular and subangular with cores of quartz and calcite. The quartz core is encased in layer(s) of calcium-rich aluminosilicates, and/or calcium/iron oxides. The calcite core is usually encased in an anhydrite shell.

Particles emitted from three coal-fired power plants burning subbituminous coals from Alberta, Canada were examined for total particulate matter (PM) and size fractions PM >10 , PM 10 , and PM 2.5 . The sampling was carried out following EPA Method 201A, which requires a 6 inch port. Three tests were performed at each station. The rates of emitted particulates from the three power plants are 9.9–53.4 mg/m 3 (dry), 30–90 kg/hr (dry), and 0.039–0.118 kg/MWh, respectively. The emission rates of the various particle sizes for these three power plants are 8.7–39.5 kg/hr of PM >10 , 10.7–40.8 kg/hr of PM 10 , and 9.65–10.7 kg/hr of PM 2.5 . The present results indicate that 29–44% of emitted particles are PM >10 . The total emissions of particulates from two power plants are below the Canadian Guideline for emission from a coal-fired power plant (0.095 kg/MWh), while the third power plant is slightly higher than the Guideline (0.118 kg/MWh). The malfunctioning of control technology may result in unrealistic and wide variation in the measured rates of emitted particles.

Particles emitted from coal-fired power plants burning subbituminous coal from Alberta, Canada were examined for total particulates (PM) and size fractions PM>10, PM10, and PM2.5. The sampling was carried out following EPA Method 201A. Three tests were performed at each station. The emitted particles were examined using SEM/EDX and gravimetric method for the determination of their sizes. The elemental composition of particles was determined using INAA and ICP-MS. The particles emitted from the stack are classified based on their morphologies and chemistries to the following: unburnt carbon, feed-coal minerals such as quartz, and by-products of the dissociation, fractionation, and contamination by minerals in coal. The emitted particles are mostly spherical and their matrices are composed of aluminosilicate minerals containing calcium. The PM>10 fraction contains small plerospheres, fragments of char, and angular quartz and feldspar particles. The PM10 fraction contains solid spheres and cenospheres, gypsum needles, and particles of char. The PM2.5 particle size fraction is mostly composed of solid spherical aluminosilicates with some surface enrichment of elements such as Ba, Ca, and Fe. The composition of emitted particles is ferrocalsialic. Most elements in the particle size fractions are Class I or II, such as Al, Ca, and Fe. Cd, Cu, Mo, and Ti were only detected in PM2.5 fraction.

Feed-coals used in some Canadian power plants were examined for their mineralogical and elemental composition. The mode of occurrence of elements (organic/minerals) in these samples were determined using sequential leaching by H 2 O, NH 4 OAc and HCl. Canadian feed-coals examined in this study are subbituminous to bituminous rank (calorific values: 19.62–29.88 MJ/kg). The sulphur content of these coals is 0.32–3.55%. Quartz and aluminosilicates (clay minerals and feldspar) dominate the mineralogy of these samples. The accessory minerals consists of pyrite, sphalerite, barite, calcite, anhydrite, chromite, zircon, biotite, and monazite, which occur as both primary and secondary cell filling types. An interesting mineral found in one of the subbituminous feed-coals is the gorceixite that is normally associated with degraded volcanic ash. The sulphur content of the feed-coals is an indication of their geological setting with feed-coal formed in a fresh water setting containing the least amount of S and those associated with evaporites having the highest S content. The concentrations of Cd, Cr, Cu, Hg, Ni, Se, V, and Zn in these Canadian feed-coals are low compared to world coals. Mercury content of these feed-coals ranges from 0.04 to 0.16 ppm. Mercury is mostly associated with the pyretic portion of coal and has direct correlation to As and S content in these coals. Arsenic in low sulphur coals is mostly associated with coal macerals and in higher sulphur coals with pyrite. About 47% of As in high sulphur coal is removed after leaching by HCl. Water soluble elements consist of Co, Ni and Mn, which are associated only with bituminous feed-coals. The removal of these elements by water is possibly due to an increased acidity of leaching solution and presence of soluble Cl and S. Beryllium and vanadium in low S coals are mostly removed after leaching by HCl, indicating a possible association with clay minerals. Limited Be and V is removed from lower clay mineral content coals; however, in high S content coals, more Be and V are removed. The speciation of As, Cr and Ni indicates that As is mostly present in the less-toxic form As +5 and Cr is present entirely as Cr 3+ , an essential human trace nutrient, found in both subbituminous and bituminous ranked coals. Nickel is present mostly as Ni 2+ in oxygen coordination in these milled coals and carcinogenic compounds of nickel are not present in these feed-coals.

This study reports on the elemental concentrations and vertical variation of coal seams from the Obed Mountain deposit, Alberta Foothills, Canada. Results from two sections of Seam 1 show that the major elements (i.e. Al, Fe, Mg, K, Na, Ti, and Si) have high concentrations in intervals having high ash content, with the only exception of Ca. Similarities are apparent, in both sections, in the vertical variations of Th, U, Se, and Zn; Rb, Cs, and K; Sb, Mo, and W; Mn and Sr; and Ba, Cr, Co, Hf, and Sc. These similarities are also evident among the REEs, notably between Ce and La; also between Dy, Eu, and Sm. Most elements, with the exception of Ba and Sr are slightly more concentrated in Section 2 of Seam 1, located approximately 1.5Fig. km away from Section 1. Compared to Seam 1, Seam 2 has lower mean concentrations of elements. Boron in the coal ranges from 27 to 100 ppmw, though most values are less than 50 ppmw. Boron concentrations suggest a freshwater depositional environment. The element is depleted in the sedimentary partings (12–29 ppmw only) and is enriched in the coal interval near the roof and immediately beneath the partings. This enrichment shows possible downward mobilization of boron. Vertical variations of elements are helpful in delineating the boundaries between coal and sedimentary partings in the succession. The Obed Mountain coals are “clean” by world standards and their elemental concentrations are comparable with those in coals of a lower rank from the same coal formation used for power generation in Alberta. All sedimentary partings have low concentrations of Ba, Hf, Sc, Sr, Ta, Th, U, and REEs; this, along with the absence of an Eu negative anomaly suggests a non-volcanic origin for the partings.

Fluorine was determined in 57 samples of coals from western Canada and the Yukon (47 bituminous, 4 subbituminous, 6 lignite) by a pyrohydrolysis method. The range of values is 31–930 ppmw F in dry coal, the lowest values being mainly for the low-rank coals. For bituminous coals most values are in the range 31–580 (mean 174) ppmw F.

The concentration of 58 elements in Byron Creek coals ( % Ro = 0.942 1 .05 ), and their 1000 °C ashes were determined using intense neutron activation and plasma emission spectrometry. The organic-inorganic affinities of elements were detected by the trend of element concentration versus ash content of the samples. Antimony, boron, bromine and selenium are the only elements that are enriched in these coals. The higher concentration of boron in one coal seam is considered to indicate that this seam was deposited in a more marine environment than the other seams. Coal seams can be identified by the concentration or depletion of certain trace elements, such as boron, sodium, thorium and uranium. Similarity indices of coal samples are also a useful tool in seam identification. Certain elements, for example gallium, thorium and uranium, are more concentrated in carbominerite from the roof or floor than within the coal. Regular variation of boron, sodium, thorium and uranium may indicate the repetition of certain units in tectonically thickened coal seams.

Isotropic to anisotropic pyrolytic carbon was observed in Canadian subbitumonous to bituminous coals (% R oil = 0.50−1.0) using reflected light microscopy. Morphologically, pyrolytic carbon consiste of large, well-developed spherulitic and laminated forms occuring in coal macerals and carbominerites as cell and crack filling. The spherulitic forms probably developed rapidly and laminated forms over a period of time. The presence of pyrolytic carbon in coal may indicate a thermal event and, in these coals it is of detrital nature and therefore should be grouped with inertodetrinite.

The occurrence of coal is related directly to the climate of a given geological age which, in turn, is determined by the extent of the seas, regional geography, the configuration of the land masses and therefore, by the ongoing process of continental drift. Of major importance also is the relative vertical movement of the coal-forming basins, resulting from tectonic movement, which affects the rate of burial and the coalification process. In this review the changes in climate and continental positions, relative to coal formation, are described from the early Carboniferous to the Tertiary. The genetic relationships between different coalfields, in terms of the flora of the period are commented upon and it is suggested that by studying the palaeogeography of the world it is possible to correlate apparently unrelated coalfields.

The effects of atmospheric oxidation at 378 K upon the carbonization of a coking and a caking vitrinite have been examined in terms of the origins and extents of development of anisotropic material. The vitrinites, oxidized from 1 to 40 days, were carbonized to temperatures between 618 and 878 K, in open boats under nitrogen at atmospheric pressure, and in sealed gold tubes at maximum pressures of 140 to 310 MPa. Optical microscopy was used to observe, qualitatively, changes in reflectance and in shape and size of the anisotropic material of the carbonized product; morphological changes were monitored by scanning electron microscopy. For both vitrinites, whereas one day of oxidation destroyed coking properties and almost all of the anisotropic development in the open-boat carbonizations, the pressure carbonizations were not significantly affected until after five days of oxidation. Anisotropy still developed by mesophase growth from the plastic phase of carbonization, to produce the shaped, botryoidal material characteristic of pressure carbonizations. Thereafter, although in the pressure carbonizations the particles of coking vitrinite only fused slightly at interfaces to form a coherent product, marked increases occurred in reflectance and in observed anisotropy, showing maxima at nine days of oxidation. Results are interpreted on the assumption that oxidation cross-links the macromolecular structure of the vitrinite substance. The effect of high pressure during carbonization after five days of oxidation is to preserve and perfect the original basic anisotropy of the vitrinites initially stabilized by the cross-linkage of oxygen atoms.

Three vitrinites (C = 80.0, 87.9 wt%, daf and 94.2 wt%, dmmf) have been heat-treated over the temperature range 1000–2400 °C in the presence of argon. The variation of morphological and optical properties of the heat-treated samples is studied systematically using reflected-light microscopy. An optically isotropic, highly reflecting material is formed on the surface of anisotropic particles of two of the vitrinites (C, 80 and 94.2 wt%) during semi-graphitization (1000–1400 °C), which decreases in extent with increasing temperature and is absent at the end of this stage. The development and subsequent disappearance of the isotropic material is probably due to the evolution of volatile matter and subsequent deposition of pyrolytic carbon during semi-graphitization. The continuous increase of bireflectance of these two vitrinite residues, with heat-treatment temperature, indicates progressive improvement in the ordering of the molecular structure. The reflectance of the heat-treated anthracitic vitrinite (C, 94.2 wt%), increases continuously whereas the reflectance of the heat-treated low-rank vitrinite (C, 80 wt% decreases slightly from a maximum during semi-graphitization. The third vitrinite (C, 87.9 wt%) does not develop an optically isotropic highly reflecting material on particle surfaces during semi-graphitization. However, this vitrinite softens during carbonization (25–1000 °C) producing a residue with a mosaictype anisotropic microstructure. The condition of polished surfaces prepared from residues of this vitrinite from the semi-graphitization to crystallization stages (1000–2300 °C) deteriorates, values of bireflectance and reflectance decrease continuously with increasing temperature. This appears to result from a reduction in the surface hardness of particles of this vitrinite residue resulting on transformation from two-dimensional ordering to three-dimensional graphitic ordering.

Vein, lens and stratiform natural sedimentary bitumen deposits were analysed by combined geochemical and micropetrographic techniques. Reflectances in oil, air and water, fluorescence spectral properties, solubility in dichloromethane, elemental analysis and bulk chemical composition of soluble fractions by chromatographic separation indicate that these materials are generally gilsonite bitumen, although some, showing evidence of significant alteration and weathering, are closer to albertite in composition. Optical properties show that the bitumens are immature and fall within the field of asphaltites on the bituminization curve. Fluorescence spectra generally show two maxima, again a feature associated with immature gilsonite bitumen. Capillary-column g.c. of saturates fractions indicates the absence of normal and acyclic isoprenoid alkanes, these fractions being dominated by a series of C27-C34 pentacyclic triterpanes of the hopane family. The saturates fraction composition is characteristic of biodegraded crude oils, and molecular biomarker stereochemistry indicates a moderately mature petroleum source. All the bitumens are shown to have a common genetic origin and are thought to be the result of in situ alteration and biodegradation of oil infillings in joints, fractures and bedding planes, resulting from fracturing and faulting of reservoir and overlying cap rocks associated with a period of Neogene tectonism.

Vitrinite-rich samples from a weakly caking and a strongly coking coal have been carbonized both fresh and after preoxidation for 14 days at 105 °C to points within the temperature range 300–800 °C. Conventional reflected-light microscopy shows that pronounced reduction in softening capacity and devolatilization of carbonized preoxidized reactive macerals are accompanied by microscopical features which contrast with those of the same reactive macerais when carbonized fresh. Most noticeable is the retention of the original petrographical structure of the coals when carbonized after preoxidation, even at temperatures of 800 °C. No mosaic is formed in the preoxidized reactive macerals, although a general anisotropy gradually develops; some vitrinitic particles attain a very high degree of anisotropy though all of this development takes place in the solid state. The level and trends of the average bulk bireflectances of both forms of carbonized vitrinite are similar, but the rapid bireflectance rise characteristic of vitrinites carbonized above ≈ 600 °C probably begins earlier in preoxidized than in fresh vitrinites. This could happen if preoxidation raises the aromaticity of the original vitrinite, so allowing reorientation of the lamellae to begin at lower temperatures. Comparisons are made with earlier observations.

The dispersion of optical properties (e.g. reflectance, refractive and absorptive indices) of graptolite epiderms in early Paleozoic sediments with low to high maturity levels (conodont alteration index = 1–5) has been determined in the visible spectrum (450–650 nm). The results were compared with those for vitrinite of different rank and asphaltic pyrobitumen. The dispersion follows similar trends to those of coal macerais such as resinite, vitrinite, and also asphalt and pyrobitumen. This indicates similar molecular structural changes, e.g. an increase in aromaticity and ordering of aromatic carbons for graptolite epiderms with increased maturity. The dispersion of optical properties of graptolites in sediments with a low maturity level falls from blue to red in the visible spectrum, indicating low aromatic carbon content. Those in more matured sediments rise from blue to red indicating high aromaticity and molecular ordering for these graptolites. Graptolite epiderms are sensitive to a rise in temperature and are a good indicator of the maturity of early Paleozoic sediments.

Liptinitic macerals in medium and low-volatile bituminous coals (C=87.9 and 90.0 wt% daf) which have undergone a plastic stage during primary carbonization (

Chemical and petrological analyses were carried out on several British Columbia coals which are known as ‘needle’ coals because of the pine needle morphology exhibited on weathering. The object was to determine the nature of the precursor and thus to identify the component maceral as resinitic or algal. Infrared spectroscopy, saturate fraction gas chromatography, pyrolysis chromatography, gas chromatography-mass spectrometry, organic elemental analysis and reflectance and fluorescence microscopy were used. While the i.r. properties are consistent with previously published results on resinite, the other chemical results suggest that the present materials are not obviously related to any given member of the liptinite group of macerals. High concentrations of extractable hopanoid hydrocarbons are interpreted as resulting from high contribution to the biomass by bacterial debris. The petrological results suggest that the main constituent of the ‘needles’ can be best described as bituminite II or III derived from non-algal lipids. This conclusion is also supported by the observed associations of the other identifiable macerals. The results indicate that the ‘needles’ have been chemically and petrologically homogenized from a liptinite-rich precursor with minimal algal input. The present morphology may have been preserved from resin rodlets which have been severely altered by catagenetic or biological mechanisms or both.

A partially combusted and coked coal seam from Aldridge Creek, British Columbia, Canada, was studied using reflected light microscopy. Three zones, namely combustion, distillation and unaltered coal were detected. Combustion had taken place in the uppermost part of the coal seam, immediately below the melted roof rock, the only evidence of combustion being the presence of coke showing oxidation rims. The distillation zone encompassed most of the coal seam; different stages of carbonization were evident in the samples from this zone, with a coke subzone occurring at the top and a precarbonization subzone at the base. Samples from the coke subzones show granular anisotropy; the reflectance and bireflectance of medium grained mosaic are higher than those measured on fine grained mosaic in the same samples from this zone. An unaltered coal zone occurred at the base of the coal seam.

This Paper describes the optical properties of chitinous material found in Canadian subbituminous coal (%/ R oil = 0.65). The chitinous material was examined using reflected, transmitted and fluorescent light microscopes. Morphologically, chitin is distinguished from other coal macerals by possession of a two-layered structure with a fibrous layer contiguous with a finely porate lamellar layer. The chitin is low reflecting, and shows fluorescence colour and spectra similar to resinite in coal.

Resinite concentrate from a subbituminous coal ( R oil = 0.45%) was oxidized in air for 1 h intervals at fixed temperatures between 50 and 400 °C. The oxidized residues were examined using reflected white and fluorescent light microscopy. Three phases of oxidation were observed. Phase I (50–125°C) was marked by an oxidation rim with lower reflectance than the main mass of resinite, perhaps indicating chemisorption and decomposition of the chemisorbed components. Phase II (150–350°C) was apparent from the development of two oxidation rims, the outer of higher and the inner of lower reflectance than the main mass of resinite, perhaps indicating an ‘oxycoal’ phase. Phase III (〉 350° C ) was marked by a sharp increase in reflectance of the outer oxidation rim and a similarity in reflectance between the inner oxidation rim and main mass of resinite, perhaps indicating a ‘combustion phase’. The fluorescence properties (colour, wavelength of maximum intensity and red-green quotient) of the oxidation rims shifted from green towards the red region of the spectrum with increasing oxidation temperature and were a good indicator of the progress of oxidation.

A study is made of the morphological and optical properties of a blend of concentrated sporinite and vitrinite macerals (equal parts) from the same coal carbonized between 400–900 °C at 5 °C/min under nitrogen. Two coals of different rank were used and the results compared with properties of unblended carbonized sporinites. Coke from a blend of low-rank vitrinite and sporinite produced a two-phase optical texture, whereas coke from the medium-rank vitrinite and sporinite mixture produced a three-phase optical texture. A ‘Transitional Zone’ of optical texture was observed at interfaces between carbonized vitrinite and sporinite, this zone being wider for the coal of higher rank. The increase of bireflectance in oil with carbonization temperature of the sporinite in the blends was lower than for the carbonized unblended sporinite, caused by a reduction in fluidity of sporinite with blending. The decrease of refractive index for sporinite carbonized > 600 °C in the blends was lower than that of the unblended sporinite.

Vitrinites ranging from sub-bituminous to anthracitic rank have been heated at 150 and 350 °C for residence times extending up to 32 weeks. Devolatilization vacuoles develop in all the vitrinites at 350 °C, apart from the anthracitic. Occasional small vacuoles formed in the vitrinites of coking rank at 150 °C are most probably related to gas evolution from liptinites. Slight rounding of the margins of vitrinite particles of coking rank at 350 °C indicates softening, while heating at the longest residence time has been sufficient to allow vitrinites of coking rank to undergo ‘active decomposition’. Mosaic structures have developed at temperatures as much as 125 °C below those normally attributed to the formation of such structures in short-term laboratory carbonization experiments on vitrinites of the same rank. Again, apart from the vitrinites of anthracitic rank, the reflectance of vitrinites shows a rise at 150 and 350 °C that would continue beyond the longest residence time used. At 350 °C a large part of the reflectance increase occurs during the first week of heating. The reflectance data and the derived refractive and absorptive indices indicate that with sufficiently long residence times, changes that are more fundamental than ‘molecular stripping’ must take place, probably involving condensation reactions that introduce increased coplanarity into the vitrinite molecules. The implication of these data to thermal metamorphism of coals and to the normal coalification process is briefly discussed.

Summarization: Major and trace element analyses were performed on coals from various locations in western Canada, and on low-temperature (150 °C) and high-temperature (1000 °C) coal ash produced from these coals. Elemental analyses were carried out by X-ray fluorescence spectroscopy and intense neutron activation analyses. Based on their trace elements, the coals in this study fall into two groups: 1. low-rank coals (lignite-subbituminous) of late Cretaceous and Tertiary age; and 2. high-rank coal (bituminous-semianthracite) of Jurassic-Cretaceous age. The elemental analyses of the coals and coal ash indicate that the local conditions had considerable influence on the concentrations of certain trace elements. Antimony and selenium in coals are the only elements which are enriched relative to concentrations in the earth's crust; arsenic is concentrated in lignite to subbituminous coal, but is depleted in bituminous-anthracite coals; as expected the ash of these coals showed many more instances of enrichment. Presented on: Fuel

Samples from a burning bituminous coal seam from Coalspur, Alberta, were studied by reflected light microscopy. Two zones — namely oxidation-combustion and distillation — were detected in the seam. Near the surface, the oxidation zone contained chars showing cracks and oxidation rims. The cracks were filled with fluorescing hydrocarbon material formed by thermal cracking of coal macerais. The chars in the deeper part of the oxidation zone had a carbonized matrix and burnt rims. The distillation zone covered most of the coal seam. Chars were mostly in the precarbonization stage, except those immediately below the combustion zone or near the base of the seam. Precarbonized chars contained pyrolytic carbon in some horizons. The distilled chars were formed by heat generated by combustion at the top of the seam and also by heat transfer from an underlying burning seam through an intermediate clastic layer. The minimum temperature of formation of residues in the oxidation and distillation zones was estimated.

Large Isotropic and anisotropic, angular and rounded fragments of inertinite were found in a Canadian subbituminous coal (%R oil = 0.50). The istropic fragments included pyrofusinite, macrinite and pseudovitrinite with pre-oxidized, heat-treated fragments showing oxidation rims. The anisotropic fragments include the heat-treated residue of liptinite, e.g. resinite showing granular anisotropy, pyrolytic carbon and fragments of vitrinite showing basic anisotropy. The morphology of inertinite fragments is described and an attempt is made to correlate these particles with heat-affected coal macerals. The occurrence of pyrolytic carbon with a reflectance of 3.11% and of liptinite showing anisotropy in a coal matrix with a reflectance of 0.50% is unusual. It indicates the detrital nature of the pyrolytic carbon. The formation of isotropic and anisotropic inertinite was possibly due to a thermal event, perhaps a wood or swamp fire. The pseudovitrinite found in these coals may have been formed by heat-treatment of fossil oxidized vitrinite fragments. The anisotropic fragments in the coals (e.g. pyrolytic carbon and anisotropic vitrinite), are detrital and are grouped with inertodetrinite.

Six vitrinites of bituminous and anthracitic rank have been carbonized in nitrogen at three heating rates (1, 10 and 60 ° C/min) to temperatures between 20 and 950 ° C. The development of anisotropy, reflecting the growth and increasing ordering of the aromatic lamellae of the chars, has been assessed by reflected-light microscopy in two ways: 1. (a) qualitatively by observing the changes taking place in the morphology of the chars in plane-polarized light and under crossed polars, particularly the form of their mosaic structures 2. (b) quantitatively by measurements of oil bireflectance of the chars at 546 nm. Rising heating rate has its most pronounced effect in rapidly increasing the anisotropy of chars formed from vitrinites of medium-volatile bituminous rank. Fast heating rates have much less effect upon the anisotropy of chars from low-rank vitrinites and still less influence upon the anisotropy of chars formed from high-rank coking and anthracitic vitrinites, where the initial rank and the final carbonization temperature are much more important factors. The relation between ‘softening’, the development of mosaic structures and bireflectance is less well defined at fast heating rates than it is at more conventional heating rates of a few degrees/min and this aspect is discussed. Although bireflectance is not a highly specific parameter, its use in combination with measurements of mosaic size to assess thermal history or even the initial properties of coke-forming components seems to be a realistic possibility. The employment of fast heating rates to produce high levels of anisotropy in carbonized products for industrial processes, and the application of the data obtained in the current investigation to evaluate thermally metamorphosed coals in natural environments, are also briefly considered.

The effect of pressure on the optical properties of cokes from a medium volatile bituminous coal (carbon = 87.9 wt% daf), some carbonized at atmospheric pressure and others under hydraulic pressure (21–310 MPa), over temperatures ranging from 350 to 600 °C at 50 °C intervals, has been studied. The cokes formed at atmospheric pressure developed fine grained mosaics, while medium-flow type mosaics formed in coke carbonized under hydraulic pressure. The thermal decomposition stage began at lower temperatures with increasing hydraulic pressure, resulting in a prolonged devolatilization phase for coke formed at a pressure of 21 MPa. Hence the fluidity of samples carbonized under pressure decreases with increasing hydraulic pressure. Pressure promotes the optical anisotropy apparent from the level of bireflectance. The reflectance of coke formed at atmospheric pressure is higher than that of cokes carbonized under hydraulic pressure, perhaps due to the inhibitory effect of entrapped volatile matter during carbonization under hydraulic pressure. The morphological features of vitirinite carbonized under pressure resemble those of coals naturally affected by heat.

The optical properties have been examined of three vitrinite-rich coals (carbon, daf: 82.5, 88.0 and 93.1%), carbonized at temperature intervals of 25 °C over the greater part of the range 20–950 °C using a heating rate of 2.45 °C/min. The small temperature interval employed has allowed a satisfactory correlation between alterations in the physical state of the carbonized products and fluctuations in the rates of change of their optical properties during carbonization. In general, as temperature rises the variation of all the optical properties reflects the growth and development of organized polycondensed aromatic systems, but in detail reflectivity does not prove as sensitive an indicator of structural changes as do other optical parameters, particularly refractive index. The behaviour of the refractive-index curves of the carbonized vitrinites is governed by changes in the heights of the crystallites forming the aromatic systems. The shape of these curves closely follows the shape of curves produced in independent X-ray diffraction studies giving the heights of crystallites. While all the refractive-index and all the absorptiveindex curves are similar in shape and trend to one another, each of these curves for carbonized coking-coal vitrinite is displaced from the equivalent curves for low-rank bituminous and anthracitic vitrinites. The displacement can be related to the formation of the highly-plastic stage during carbonization of the coking-coal vitrinite, which ultimately yields weakly cross-linked structures with good crystallite orientation, in contrast to the strongly cross-linked structures with lower ordering developed in carbonization of vitrinites of both lower and higher rank.

The optical properties at 546 nm of three vitrinites (daf carbon contents 82.5, 88.0 and 93.1%) have been examined after pre-oxidation for 14 days at 105 °C and carbonization at intervals of 50 °C within the temperature range 300–800 °C. In general, pre-oxidation prior to carbonization produces only relatively small changes in the trends of optical parameters with temperature that were observed for the same vitrinites when carbonized fresh; the properties of the anthracitic vitrinite displayed little modification. Reflectivities of carbonized pre-oxidized vitrinites of bituminous rank are higher than those for the equivalent fresh vitrinites up to 500 °C, supporting the suggestion that oxidation raises aromaticity and consequently the reflectivity. The most noticeable optical difference occurs with the bituminous-rank vitrinites, in the variation with carbonization temperature of their refractive-index curves, which parallel the behaviour of the L c curves of X-ray diffraction studies. In particular, the refractive-index track for the carbonized pre-oxidized vitrinite of coking-coal rank no longer shows the same marked contrast to the refractive-index tracks of vitrinites of higher and lower rank, as it does at temperatures above 600 °C when carbonized fresh. The absorptive indices follow similar trends to the reflectivities for all the chars.

Polished surfaces of anthracitic vitrinites, when viewed by reflected light using oil immersion lenses and crossed polars, frequently display remnant botanical structure. Such stucture may be retained, often with enhanced contrast between cell walls and cell fillings, even when the vitrinite is carbonized at temperatures as high as 2400 °C. Although increases in aromatic-layer diameters and stack heights have occurred, albeit in the solid state, there is no apparent distortion of the cell structures. Reference is made to similar phenomena in vitrinites from other environments, viz. low-grade metamorphism and carbonization after laboratory or natural oxidation processes.

A description is given below of the optical properties of organic components of the Grinnell oil shales from Arctic Canada. The oil shales were examined by using reflected- and fluorescent-light microscopy. The organic components of these oil shales consist of alginite, bituminite and exsudatinite with a small quantity of other liptinite and vitrinite macerals. Evidence is presented to suggest that exsudatinite in these oil shales is mainly formed from bituminite that migrated into available free space. It is accepted that the bituminite formed by the alteration of alginite. The fluorescence properties of the major liptinitic components of these oil shales shift gradually from shorter to longer wavelengths from alginite to exsudatinite.

The microstructure of coke formed on carbonization of a low-volatile bituminous rank vitrinite (NCB Classification 204), at a heating rate of 60 °C min −1 , was found to consist largely of coarse-grained mozaic and domain type optical texture. The domain optical texture possessed a variety of optical structures, e.g. ‘X’ and ‘Y’- type crosses and nodes, characteristic of it having passed through a nematic liquid crystal stage (mesophase) during carbonization. These structures are compared with, and found equivalent to, disclination structures found in the domains of a petroleum needle-coke, the surface of which had been gasified to reveal the underlying graphitic structure. The formation of disclination structures in the domains of the coal-coke is strong evidence for the formation and coalescence of mesophase during its carbonization as a result of the very high heating rate used.

In fuel science there is a need to present the relationships between the elements of a group of variables or a group of samples as tables of data. The dendrograph, a derivative of the dendogram, is a method used for general cluster analysis. It offers an improvement by providing an irregular spacing of the objects classified on the x axis. The mathematical basis of this method is described as unweighted pair group method of clustering.

The behaviour of the dispersion curves of refractive and absorptive index of a vitrinite of high-volatile rank oxidized for different periods of time up to 128 days at 105 °C supports the suggestion that the aromaticity and/or condensation of the vitrinite rise when it is oxidized. Equivocal optical data previously obtained for oxidized vitrinites can probably be explained by the extensive use in earlier microscopical studies of wavelengths in the green region of the visible spectrum. Reflectivity-dispersion data indicate that there is greater possibility of distinguishing oxidized and weathered coals from fresh samples with the microscope by comparing their optical properties in the blue region of the visible spectrum or in the ultra-violet.