Mineral matter and elemental concentrations in selected western canadian coals

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.     

Genesis of micrinite in some Australian coals

Seven Australian coals have been examined petrographically and two types of micrinite, disseminated micrinite and cavity-filling micrinite, are described. The disseminated micrinite appears to be very fine fragments of fusinite, semifusinite and other low reflectance inertinite. Cavity-filling micrinite occurs only in inertinite-rich coal seams and was formed under aerobic conditions. It is considered that porigelinite and other granular material in peat are the major progenitors of the cavity-filling micrinite. Such progenitors would have entered cell cavities and other voids, possibly as a water slurry, before or after they had been partially oxidized.     

Correlation between the content of volatile matter and mineral matter in hard coals

If coal is heated to 900 °C, in the absence of air the organic coal substance and the associated mineral matter are decomposed. The analytically determined volatile-matter yield includes the volatile decomposition products of both the coal substance and the minerals. The correlation between mineral matter and ash and the volatile-matter yield is derived, and its accuracy shown by evaluation of test results. Methods are proposed for calculating a value for the volatile matter dmmf for coals of a particular mine. Various formulae for calculating the volatile matter of coals to dmmf basis are critically considered. Finally, a generally applicable equation for calculating dmmf volatile matter is derived which can be used for classification.     

Occurrence of some hazardous metals in Indian coals

Studies on hazardous metals pollution through various processes of utilization of the Assam (India) coals suffer from the lack of reliable information on the level of trace and heavy metals in them. Four representative coal samples with high sulphur from Ledo, Tikak, Tipong and Baragolai collieries of Makum coalfield, Assam, India were studied for the occurrence of Al, Bi Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Se, V, and Zn by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) methods. Six of the metals (Cd, Cr, Co, Mn, Ni, and Pb) found to be present in low to moderate concentrations were identified as Hazardous Air Pollutants (HAPs) in the 1990 Clean Air Act Amendments (CAAA) USA. The concentration of Fe, Mg and Al was observed to be higher than the rest of the metals. Significant variation of these metal contents in the four coals samples was observed with no noteworthy statistical relationship with the ash and carbon contents of the coals. The concentrations of metals in the samples are within the average world coal range. It was also observed that there is no definite trend of metal concentration with reference to different collieries of Assam. The association of some metals in the coal matrix was also discussed. XRD and FT-IR patterns of the coals also supported the presence of these metals. Published in Russian in Koks i Khimiya, 2009, no. 2, pp. 12–17. The article is published in the original.     

Fluidized-bed gasification of some Western Canadian coals

Three Western Canadian coals were gasified with air and steam in a fluidized bed of 0.73 mm sand and coal, at atmospheric pressure and temperatures of 1023–1175K to produce a low-calorific-value gas. One non-caking and two caking coals were tested. The effects of temperature, coal feed rate, $\text{air}\text{coal}$ ratio, $\text{steam}\text{coal}$ ratio, coal quality, coal particle size and bed depth on gas composition, gas calorific value and operating stability of the gasifier were established. Results are compared with those previously obtained for the same three coals when gasified in essentially the same equipment, but operated as a spouted bed.     

Effect of carbonate minerals on volatile matter of coals

Coals high in carbonate minerals show abnormally high VM on dmmf basis. This abnormality has been shown to be due to the presence of iron carbonate. Effects of the presence of different carbonate minerals on VM have been estimated, and a formula is advanced for estimating VM on dmmf basis of a coal having a particular distribution of carbonate minerals: $\text{VM}\text{on dmmf basis}\text{=}\text{As analysed}\text{VM ? 0.1 Ash ? 1.3 CO}{}_2\text{100 ? (MM + Moisture)}\text{× 100}$     

Oxidation of some bulgarian coals. Influence of low-temperature oxidation on the microhardness and reflectivity of some brown coals

Experiments carried out with two clarain and three vitrain samples from the Bobovdol basin and two clarain samples from the Pirin basin have shown that changes in microhardness and random reflectance are useful indications of changes which occur in the coal substance during oxidation processes at 150 and 200 °C and subsequent extraction.     

Behaviour of inorganic matter during heating of Bulgarian coals: 2. Subbituminous and bituminous coals

Bulgarian subbituminous (Pernik, Bobov Dol) and bituminous (Balkan) coals were gradually heated under air from 100 °C to their fluid ash-fusion temperatures (1400–1600 °C) via 100 °C intervals and the behaviour of their inorganic matter (IM) was studied. The original minerals and newly formed inorganic phases in the oxidation and combustion products (OCPs) of these coals were identified and the behaviour of 33 minerals and phases was described. The coals studied reveal high detrital abundance and low authigenic mineralization with sulphide–sulphate, carbonate or mixed sulphide–sulphate and carbonate tendencies. The IM of coals is composed mainly of quartz, kaolinite, illite + muscovite, feldspars, pyrite, and calcite, while the other minerals identified have subordinate occurrence. The IM of OCPs includes various pre-existing minerals and newly formed phases. The latter phases are glass, quartz–cristobalite–tridymite, mullite, amorphous clay material, hematite–magnetite, anhydrite, and others originating from the heating of these coals or storage of their OCPs. The physico-chemical processes and temperatures that result in the formation of new phases in OCPs are described. The relationships between the ash-fusion behaviour and chemical and mineral composition of the coals are also discussed. A systematization of the physico-chemical transformations and some comparative characterizations, as well as prediction of certain technological and environmental problems related to the behaviour of IM during heating of Bulgarian lignites, subbituminous and bituminous coals are also described and summarized.     

Investigation of the flash pyrolysis of some coals

Five bituminous coals, an anthracite and a lignite have been flash-pyrolysed by the electrically-heated grid technique or by means of an electrically-heated fluidized-bed. In the experiments using a heated grid, data were obtained on rates of rapid devolatilization and on the composition of the gases and tars evolved with heating rates up to 3000 Ks^?1 and peak temperatures up to 1400 K. Similar, but more limited data were obtained using the fluidized-bed system. Mathematical models based on overall single- or two-reaction pathways were compared with the experimental results. Good agreement could be achieved by the latter with activation energies of 16 and 35 kJ mol^?1.     

Electron spin resonance studies of some Canadian coals

Nine Canadian coals of different rank and composition were studied by electron spin resonance. For percentage of fixed carbon in the range of 43 to 78 wt%, the free radical g values were found to increase with decreasing carbon content, and did not level off for the low rank coals. The free radical linewidths are attributed to atomic species such as oxygen and not to protons of hydrogen.     

Solubilisation of some bituminous coals in quinoline by ultrasonic irradiation

The solubilisation of 4 hvab and 1 hvbb coals by ultrasonic irradiation of coal-quinoline systems at ambient temperature was investigated. The amount of coal solvated was found to be a function of time and particle size. The use of a char prepared at the temperature of maximum coal fluidity increased the amount of material solubilised. There was little difference in the amounts of coal solubilised at 36° and 80°. There was a decrease in the sulphur and ash content of the solubilised coal compared with the starting coal. Quinoline can be re-used as a solvent with no decrease in solubilisation efficiency. Based on high-resolution mass spectrometric and infra-red spectroscopic investigations and particle size measurements of the solubilised material, it appears that the increased solubilisation of coal in quinoline results from a grinding action and not a chemical action.     

Composition and properties of coals from some deposits in Mongolia

Nine coal samples from different deposits in Mongolia were studied with the use of a set of chemical and physicochemical methods of analysis (proximate and ultimate analyses, low-temperature extraction, the chemical analysis of ashes, thermogravimetric analysis, IR spectroscopy, and thermal dissolution) for evaluating their composition and chemical-engineering properties.     

Qualitative characteristics of power-generating coals from some deposits in Mongolia

The results of a study of the chemical composition and technological properties of coals from the Khar Tarvagatai, Nuurst Khotgor, and Khushuut deposits are presented in this article.     

Removal of mineral matter from some Australian coals by Ca(OH)2/HCl leaching

Four Australian coals, Blair Athol, Ebenezer, Newlands and Warkworth coals, were demineralized by Ca(OH)₂ digestion at 300°C, followed by washing with dilute HCl. Ash contents decreased from 8.8–15.4% to 1% for Blair Athol, Newlands and Warkworth coals, and from 14.9% to 2.8% for Ebenezer coal. The CaO/ash ratio is an important factor affecting coal demineralization; the maximum ash removals were achieved at CaO/ash ratios in the range 0.6–1 g/g for all the coals. The major minerals in the original coals were kaolinite and quartz, with some montmorillonite and carbonates. Kaolinite and quartz hydrothermally reacted with Ca(OH)₂ to form calcium-bearing hydrated silicates and aluminosilicates, such as tobermorite and hibschites, that could be dissolved in acid. With increasing CaO/ash ratio in excess of the optimum value, the removal of quartz significantly decreased; there also remains some calcium in treated coal, depending on digestion conditions and coal type. A lower ash removal from Ebenezer is due to a lower quartz removal and more remaining calcium.     

Comparative chemical and mineral characterization of some Bulgarian coals

The mineralogy and chemical composition of lignitic, subbituminous and bituminous coal and coal-ash samples from six Bulgarian deposits, namely Maritza West (MW), Sofia (S), Maritza East (ME), Bobov Dol (BD), Pernik (P) and Balkan (B), were studied and a model for comparative characterization of their composition was done. Major minerals identified in the crystalline matter of Bulgarian coals are commonly quartz, kaolinite, illite, calcite, pyrite, plagioclase, K-feldspar and gypsum and occasionally dolomite, siderite, Fe oxyhydroxides and Fe sulphates. Some genetic features of the inorganic matter in coal and coal ash are described and compared. The coals studied show high detrital (P, B, BD, ME) or high authigenic (S, MW) mineral abundance with sulphide–sulphate (P, BD, ME, MW) or mixed carbonate and sulphide–sulphate (B, S) authigenic mineral tendencies. The high-temperature ashes of these coals belong to sialic (P), sialoferricalcic (B, BD), sialoferric (ME) or ferricalsialic (MW, S) chemical types. They have high (B, P, BD) or low (ME, MW, S) silicate mineral abundance with sulphate (B, P, ME, MW, S) or oxyhydroxide (BD) mineral tendencies.     

矿物质对焦炭强度的影响

选取9种金属氧化物按干煤量0.5%、1%、3%、5%添加到马钢配煤、芦岭煤、古交煤中炼成坩埚焦后,测定焦炭的显微强度、结构强度、焦炭反应性。结果表明:PbO、B2O3、V2O5使焦炭强度显著下降;SiO2、TiO2使焦炭强度略微下降;MnO2、Al2O3、CuO、ZnO对焦炭强度无明显影响。过渡金属对焦炭反应性起正催化作用,硼族元素对焦炭反应性起负催化作用。     

Modification of the organic matter of brown coals with nitrous oxide

The results of the treatment of brown coals from the Kansk-Achinsk Basin in an atmosphere of nitrous oxide are given. It was established that the main products of nitrous oxide interaction with the organic matter of brown coal are soluble low-molecular-weight products (ketones and aromatic acids) and oxodiazoline structures in a coal matrix. The thermal-oxidative degradation of terminal oxygen-containing groups, which accompanied this process, facilitated the formation of strong crosslinks and the strengthening of a supramolecular structure.     

Removal of mineral matter from bituminous coals by aqueous chemical leaching

Most of the ash-forming minerals in bituminous coals are insoluble in water or acids, but a high proportion (more than 90%) can be extracted with aqueous sodium hydroxide solutions at 200–300°C under pressure. The major minerals extracted —silica and kaolin — are converted into sodium alumino-silicates (sodalites) which form a separate insoluble phase in contact with water or alkali, but which are readily soluble in aqueous acids. Minor mineral components are also partly removed. The spent leachants can be regenerated for recycling; the extracted minerals form a solid by-product. The chemical extraction steps may be coordinated with conventional coal-cleaning procedures which use physical separation techniques. Experiments with three Australian coals from the Liddell and Lithgow seams (NSW) and the Theodore seam (Queensland), and a vitrinite concentrate from Liddell, gave beneficiated products with ash yields of 0.25–0.75%. Demineralized coal may have applications as a low-ash fuel or carbonaceous raw material.