The Indian coal industry is currently facing a number of constraints (i .e. socio-economic, geotechnical and environmental issues) due to high demand of coal for industrial growth. In addition to the many potential geotechnical issues, the existence of extensive uncontrolled and concealed fires present a significant problem to the coal industry, the national economic growth and environment. The cause of many of these fires is the spontaneous heating of the coal seams (Zutshi et al., 2001) that create a significant problem to the productivity, safety and environmental impact of mining operations. The thesis presents the results of a systematic experimental study to determine the susceptibility of a number of Indian coal seams to spontaneous heating. A literature review revealed that the existing crossing point temperature method (CPT) assessment method is not reliable enough to be used to solely predict spontaneous heating. Therefore, there is a need to identify an additional robust and reliable technique to determine the susceptibility of coals to spontaneous heating, to assist in the classification of the coal seams with respect to their proneness to spontaneous heating. A comprehensive experimental study was conducted to analyse eleven coal samples collected from a variety of fiery and non-fiery coal seams within the Jharia coalfield (JCF) India. In the first part of the investigation, the basic coal characteristics, including a proximate, elemental, petrographic and mineral matter analysis were determined . The spontaneous heating susceptibility of all of the coal samples was studied using a number of methods, including: a morphology study of oxidised coal under microscopy, the use of the crossing point temperature method (Indian method), the use of the sponcomb rig at the University of Nottingham and the use of thermogravimetric analyses (TGA) of the coal samples. An analysis of the thermogravimetric results obtained for these coal samples at different heating rates resulted in the development of a spontaneous heating susceptibility index (SHSI). In addition, the activation energies were calculated from a kinetic study of the coal samples by employing the three different techniques attributed to Coats & Redfern (1963), Friedman (1964), and Chang (1994). Subsequently, a statistical correlation analysis was carried out to identify any links between the intrinsic properties of coal and the indices determined from the application of the different spontaneous heating susceptibility methods. It was observed that the proximate, elemental and petrographic analysis results correlated well with the spontaneous heating susceptibility results obtained from the sponcomb rig and TGA experiments. It was further concluded that the results of the mineral matter analyses do not exhibit a good correlation with any of the spontaneous heating susceptibility indices. The hierarchical clustering method was used to examine any links between the intrinsic coal properties and the result obtained from the application of each of the four susceptibility indices investigated. Each susceptibility index was subdivided into three levels, namely highly susceptible, moderately susceptible and poorly susceptible. A critical review of the literature reporting the classification of coal seams based on field observations, spontaneous heating susceptibility studies and hierarchical clustering theory concluded that any coal seam may be assigned to one of these three sub level classes by knowledge of the results obtained from the sponcomb rig and TGA experiments. An initial attempt was carried out to measure the greenhouse gas (GHG) emission fluxes in laboratory condition as well as from spontaneous heating of coal at one fire affected mine for the first time in India. Both initial laboratory and field study results concluded that there is no obvious relationship between the gas emissions experienced under both conditions.

Self-oxidation and spontaneous combustion of coals is a problem of global concern. There are social, economic and environmental costs associated with this phenomenon and major incidents can, in extreme cases, lead to human casualties. More often however, damage is made to commercial facilities, the calorific value of the fuel is reduced and substantial release of noxious gases, particulate matter and CO2 may contribute to local and international pollution levels. This problem is not only restricted to coals, it also affects other carbonaceous materials such as biomass and potentially coal-biomass blends. A considerable amount of literature has been published, and whilst the causes are relatively well understood, the existing methods for predicting spontaneous combustion are not reliable enough for scientists or the coal industry. This research focuses on understanding the oxidation characteristics of coal, biomass and coal-biomass blends at low temperatures, with the aim of defining a set of experimental test procedures to identify coal and biomass propensity to spontaneously combust. Based on a comprehensive literature survey, two main research areas were identified as feasible sources of information to detect prone coals: microscopy and thermal analysis. Considering these, an extensive experimental program was carried out using 42 coals (including at least three well known samples prone to spontaneous combustion), 10 different biomass types, and a number of coal-biomass blends, including diverse particle and sample sizes, at different stages of the oxidation process. Initially, pulverized coal samples (size <106µm) were subjected to thermogravimetric and calorimetric tests (small sample size), and differential thermal analysis (large sample size) using a large scale reactor. From these tests, the link between the weight loss/gain of the samples and the reactivity at low temperature was confirmed, developing successfully two thermogravimetric tests to identify high risk samples. Afterwards, textural features of thermally altered coal samples (light reflectance and particle morphology) were studied by means of combined petrographic and image analysis techniques. Results showed that particle reflectance and textural changes depend on oxidation temperature, which are linked to the spontaneous combustion potential. Based on these results, two tests were proposed by comparing light reflectance before and after a slow oxidation, quantifying the formation of morphotypes associated with highly reactive samples. A similar approach was used to study biomass and coal-biomass blends, focusing on the quantification of intrinsic reactivity and particle morphology by TGA and optical microscopy. For raw and char biomass particles, results showed a significant correlation between the optical and reactivity properties. Additionally, several new morphotypes were identified from biomass char samples. These characteristics were associated with the thermal behaviour of large samples, although these results did not suggest any distinctive indicator to identify samples prone to self-heat, concluding that the low temperature oxidation of biomass is a completely different phenomenon to that experienced by coals. In the case of coal-biomass blends, the most relevant finding was a synergetic effect observed for the ignition temperature, which was always lower than the ignition temperature of the individual components. This finding has not been described in literature before, and further work is necessary in order to investigate this interaction in greater depth. Finally, a set of standardised procedures to assess the reactive properties of these materials has also been proposed.

Volume 2 contains [51] coloured plates and [13] folded charts. / Bibliography : leaves 258-281. / 2 v. (xvi, 281 leaves, [51] leaves of plates) : col. ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1993