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Coal mineral matter is the leading cause of inevitable ash problems (fouling and slagging) during the combustion of coal. Low-temperature ash (LTA) samples of feed coals and the density separated fractions were subjected to high-temperature X-ray diffraction (HT-XRD) to identify the mineral reactions occurred at elevated temperatures under oxidizing conditions. Excluded minerals were mainly contained in the sink fractions, while included minerals were mainly present in the float fractions. QEMSCAN results indicate that the mineral associations in carbominerites and included minerals in Feeds A, B and C and sinks B and C are responsible for the melt formation during HT-XRD experiments. HT-XRD results indicate the presence of mullite, anorthite, and amorphous aluminosilicate materials formed in the thermally treated LTA samples. The formation of these slagging crystalline and glassy phases could be attributed to either crystallization during the cooling of the molten solution, or via solid-state reactions at elevated temperatures. A comprehensive knowledge of the included and excluded minerals can be used to prepare a blended feedstock for combustion processes. The operational ash-related problems in the combustion and gasification processes could be minimized by implementing this comprehensive knowledge of the transformation of coal minerals at elevated temperatures

Pilot-scale combustion tests were carried out on coals with low (13.5%) and high (39.6%) ash percentages from the Highveld Coalfield of South Africa, using the ALS-ACIRL 100–200 kW Combustion Test Facility. The mineral matter in the feed coals and also the chemistry and mineralogy of the ash deposits from different parts of the test furnace were analyzed using quantitative X-ray diffraction and X-ray fluorescence techniques, and the results were used to develop an understanding of the mineralogical processes taking place in the different parts of the pulverized-fuel combustion system. Low-temperature oxygen-plasma ashing and quantitative X-ray diffractometry showed that the mineral matter of both coals contained abundant kaolinite, lesser but still very significant proportions of quartz and carbonates (ankerite and calcite), and minor proportions of pyrite and other minerals. A small but significant proportion of nonmineral Ca also occurs in the organic matter, especially of the low-ash coal. The chemical composition of the combustion products taken from the different sampling points in the test facility (slagging panels, furnace ash, and fouling probes, etc.) was overall very similar for each coal sample. However, the percentages of the different crystalline minerals in the combustion products showed a wide range of variation at the different sampling points. Anorthite, derived from interaction between Ca and the aluminosilicate components, was formed from both coals at temperatures above 1300 °C, mostly as part of sintered aggregates that built up and became detached from the slagging panel in the highest temperature part of the combustion system. Anhydrite was formed by interaction of Ca with SO2; lime and periclase were also formed from the low-ash coal, where insufficient sulfur was available for complete sulfate development

The extraction of sulphur produces a hematite-rich waste, known as roasted pyrite ash, which contains significant amounts of environmentally sensitive elements in variable concentrations and modes of occurrence. Whilst the mineralogy of roasted pyrite ash associated with iron or copper mining has been studied, as this is the main source of sulphur worldwide, the mineralogy, and more importantly, the characterization of submicron, ultrafine and nanoparticles, in coal-derived roasted pyrite ash remain to be resolved. In this work we provide essential data on the chemical composition and nanomineralogical assemblage of roasted pyrite ash. XRD, HR-TEM and FE-SEM were used to identify a large variety of minerals of anthropogenic origin. These phases result from highly complex chemical reactions occurring during the processing of coal pyrite of southern Brazil for sulphur extraction and further manufacture of sulphuric acid. Iron-rich submicron, ultrafine and nanoparticles within the ash may contain high proportions of toxic elements such as As, Se, U, among others. A number of elements, such as As, Cr, Cu, Co, La, Mn, Ni, Pb, Sb, Se, Sr, Ti, Zn, and Zr, were found to be present in individual nanoparticles and submicron, ultrafine and nanominerals (e.g. oxides, sulphates, clays) in concentrations of up to 5%. The study of nanominerals in roasted pyrite ash from coal rejects is important to develop an understanding on the nature of this by-product, and to assess the interaction between emitted nanominerals, ultra-fine particles, and atmospheric gases, rain or body fluids, and thus to evaluate the environmental and health impacts of pyrite ash materials.

The Permian coals of the South Walker Creek area, with a vitrinite reflectance (Rvmax)of 1.7 to 1.95% (low-volatile bituminous to semi-anthracite), are one of the highest rank coals currently mined in the Bowen Basin. Studies of the mineralogy of this coal seam have identified unusual mineralogical assemblages in the vertical sequence, with illite-chlorite assemblages resembling a metamorphic association in some parts of theseam and kaolinite rich assemblages of more normal sedimentary origin in others.A range of analytical techniques, namely XRD, XRF, coal geochemistry, polishedsection petrology, SEM-EDS, and 3D X-ray tomography, have been used toinvestigate the nature of this mineralogical variation, including the effects ofgeological process on several aspects of coal petrology and geochemistry, andespecially the impact of rank advance and other post depositional process on themineralogical variation within the main coal seam of the South Walker Creek area.The South Walker Creek coal occurs in a single seam 10.5 to 14 m in thickness, splitin places, and is dominated by dull and bright (40-60% bright), and dull withnumerous bright bands (10-40% bright) lithotypes, along with minor dull (< 1%bright) coal. The duller lithotypes are mostly associated with a high proportion ofinertinite as seen from organic petrology studies. Overall, the coal seam is dominatedby inertinite (mainly semifusinite) with minor vitrinite, together with a smallproportion of liptinite (exudatinite and bituminite) macerals.X-ray diffraction analysis shows that the mineral matter of the coal is dominated bykaolinite and interstratified illite/smectite in the top and bottom of the seam, alongwith typically a small proportion of quartz. In the middle of the seam, however, this isreplaced by an NH4 illite-chlorite assemblage, with no quartz. Diaspore also occurs insome parts of the mid-seam interval. Some carbonate minerals (calcite and ankerite)and other minerals, namely rutile, anatase and apat

The Ombilin Basin, which lies in Sumatra Island, is one of the Tertiary basins in Indonesia. This basin contains a wide variety of rock units, from pre-Tertiary to Quaternary in age. Significant oil shale deposits occur in the Sangkarewang Formation which was deposited during Paleocene-Eocene time.Several analyses have been carried out namely, XRD, XRF, carbon and sulphur determination, thin section petrology, polished section petrology as well as Fischer assay. These were intended to determine the inorganic and organic constituents of the Sangkarewang oil shale.Inorganic constituents of the Sangkarewang oil shale consist mainly of quartz, feldspar, carbonates and a range of clay minerals, together in some cases with minor proportions of sulphides, evaporites and zeolites.The organic matter in the oil shales of the sequence is dominated by liptinite macerals, particularly alginite (mainly lamalginite) and sporinite. Cutinite also occurs in some samples, along with resinite and traces of bituminite. The dominance of lamalginite in the liptinite components suggests that the material can be described as a lamosite. Samples from the Sangkarewang Formation have vitrinite reflectance values ranging between 0.37% and 0.55%. These are markedly lower than the vitrinite reflectance for coal from the overlying Sawahlunto Formation (0.68%), possibly due to suppression associated with the abundant liptinite in the oil shales.Fischer assay data on outcrop samples indicate that the oil yield is related to the organic carbon content. Correlations with XRD data show that, with one exception, the oil yield and organic carbon can also be correlated directly to the abundance of carbonate (calcite) and inversely to the abundance of quartz plus feldspar. This suggests that the abundance of algal material in the lake sediments was preferentially associated with carbonate deposition. High yields of oil are noted in some samples, as a percentage of the organic carbon content. This may indic