Abstract Spontaneous combustion of coal seams is a complicated process that involves complex physical and chemical interactions between the seam and its surrounding environment; the ultimate results are a function of the interplay of internal and external conditions. Based on geologic field investigations and comprehensive analyses, four models of spontaneous combustion for coal were established: (1) a genesis-type model that is based on the coal characteristics that lead to spontaneous combustion; (2) a coal-fires propagation model, namely how spontaneous combustion propagates through a coal seam; (3) a model for the progressive stages and products of a coal fire; and (4) a cross-sectional model of zones that are conducive to spontaneous combustion in a mined-out area. These models provide a scientific and theoretic basis for monitoring and extinguishing the spontaneous combustion of coal.

Abstract A wide variety of techniques have been applied to gain insight into the processes that govern the self-heating of coal. These include oxidation mechanisms, ranking the propensity of different coals to self-heat, and the detection and suppression of self-heating. A frequent weakness in the literature about the kinetic data of self-heating systems is the absence of error estimates from regression analysis and the associated constraints on the reliability of the data for modeling. In addition, experimental and numerical work is needed to evaluate the methods used to acquire the kinetic data. Moist coal in coal mines and stockpiles has very different combustion characteristics than those predicted on the basis of dry testing. Consequently, methods for ranking the propensity of coal to spontaneously combust in actual mining conditions need to be developed.

Abstract Spontaneous combustion commonly occurs in storage and waste dumps from coal mining. It has been suggested that this can be prevented by the use of a protective layer (possibly compacted) of a reactive material. As the coal ages (becomes oxidized), the coal reactivity toward oxygen decreases and the oxygen profile changes. Analyses of the oxygen concentration profiles in a 3-m-long, 20 cm inside diameter plastic column filled with coal were performed for a period of up to 8 mo. The results were modeled, and they can be adequately fitted to a simple diffusion/reaction model.

Abstract Pyrometamorphism of coal measures that overlie underground burnt-coal seams in the southern area of the Rotowaro coalfield, New Zealand, has produced porcellanites that enclose lenses of iron-rich magnetite and hematite-bearing slag-like rocks, which show various degrees of oxidation. Paralavas that are associated with the iron-rich lenses form stalactites around fissures and gas-escape vents and intrude the porcellanites. The slags are unusually rich in iron and contain magnetite, hematite, hercynite, titaniferous magnetite, and minor fayalite and silicate glass. Iron oxides in these rocks exhibit a variety of textures and morphologies, including dendritic, quench, exsolution, and oxidation. The paralavas contain abundant glass, which encloses feathery crystals of fayalite and orthoferrosilite, plagioclase, tridymite, cristobalite, and minor magnetite. Phase-equilibria data indicate that the paralavas and slags were formed at temperatures in the range of 1000–1600 °C. Composition plots of local coal measure sediments, a siderite nodule, and various porcellanites, slags, and paralavas with respect indicate that the porcellanites are iron-rich when compared to SiO 2 , Fe 2 O 3 , and Al 2 O 3 with the unmetamorphosed coal measures. The slags, irrespective of their oxidation state, plot on the iron-enrichment trend shown by the porcellanites. Although the siderite nodule lies within the iron-enrichment trend, most of the slags are more iron-rich than the siderite nodule. The paralavas diverge from the iron-enrichment trend, suggesting that they formed by partial melting of the porcellanites. The Rotowaro samples represent some of the most iron-rich natural slags collected from a combustion-metamorphic environment to date.

Abstract Coal fires are one of the most common geohazards in most coal-producing countries, such as india and China. Combustion can occur spontaneously or due to anthropogenic causes, either within underground coal seams or in exposed layers of coal on Earth’s surface. Once started, coal fires are difficult to extinguish and sometimes cannot be controlled. In addition to burning millions of tons of coal, the fires have an enormous negative impact on the local and global environments. Coal fires produce large quantities of greenhouse gases, such as CO, CO 2 , CH 4 , SO x , and NO x , which have a direct impact on the local and global atmospheric composition. Since the preindustrial era, the concentration of CO 2 , a major greenhouse gas that contributes to global warming, has increased from 280 ppm to 375 ppm. Land subsidence is an associated problem in areas that are affected by coal fires. Coal fires also create operational difficulties in existing mines and endanger human safety. After the first use of remote sensing to study a coal fire in the early 1960s, this technology became a useful and convenient tool for the detection and monitoring of additional coal fires. Several air- and spaceborne thermal remote sensors are available for studying coal fires. Coal-fire–related emissions have not been studied extensively; ground-based methods mainly use CO 2 detection instruments or other indirect calculations (e.g., amount of coal burnt). Few attempts are being made to estimate coal-fire emission using remote sensing.