Characterization of some Indian coals to assess their liability to spontaneous combustion
印度煤自燃倾向性评定方法
Fuel, Volume 163, 1 January 2016, Pages 139-147
Abstract: Mine fires are a major problem in global coal mining industry and most of them are caused by spontaneous combustion that needs proper attention in strategic planning. The operational management must pay attention to an inbuilt system management for timely detection at the initial stage prior to devastating effect. To assess the spontaneous combustion liability of coal, intrinsic properties and susceptibility indices play a vital role. Forty-nine in-situ coal samples were collected from different coalfields of India. Experimentation of the samples was carried out for proximate, ultimate, and petrographic analysis; crossing point temperature; flammability temperature; Olpinski index; wet oxidation potential analysis; and differential thermal analysis to ascertain the proneness of coal to spontaneous combustion. From the statistical analysis of the samples, it was established that the parameters of the ultimate analysis show significant correlation with Olpinski index as compared to other susceptibility indices and, hence, it can be used as a reliable index to assess the susceptibility of Indian coals to spontaneous combustion.
Petrographic characterization of coals as a tool to detect spontaneous combustion potential
借助煤岩相学特征研究煤自燃倾向性
Fuel, Volume 125, 1 June 2014, Pages 173-182
Abstrac: Textural features of 25 worldwide coals were studied after slow oxidation processing (0.5 °C min−1 from 20 to 250 °C in air) using oil immersion microscopy and image analysis techniques. The characterization of samples, before and after oxidation, showed important changes in vitrinite reflectance with high reactive coals, which also related to their intrinsic self-oxidation potential. The morphology of the coal particles was also altered after the oxidation, to produce at least six different morphotypes. Particles with ‘homogeneous change of reflectance’ and particles with ‘oxidation rims’ were predominant in the samples studied, which related to boundary reactive conditions (kinetic and diffusion control of the reaction respectively). These textural characteristics indicate how particles interacted with oxygen at low temperatures, which could be used to predict the most probable pathway during the early stages of oxidation which could then lead to a spontaneous combustion event. The magnitude of the reflectance change and the morphological characteristics of samples studied were also related to the reactivity properties, providing an additional source of information to identify coals prone to spontaneous combustion.
Thermal mapping of self-heating zones on coal waste dumps in Upper Silesia (Poland) — A case study
波兰Upper Silesia煤渣堆放场自发热区域的热测量 – 实例研究
International Journal of Coal Geology, Volumes 128–129, 1 August 2014, Pages 47-54
Abstract: The evolution of self-heating areas on five chosen coal-waste dumps in Upper Silesia (Poland) was quantitatively investigated with the aim of finding a cheap and fast method of detecting and localising coal-waste fires on the dumps. The results show that Landsat 4–5 TM and ETM+ images from snow-covered terrain enable the burning areas of the dumps to be seen and that, in addition, they can be used to observe the evolution of these thermal anomalies. Furthermore, the analysis showed that the external temperature had an impact on surfaces of self-heating areas; when the air-temperature was low, the surface temperatures of these hot areas were lowered. In the study, it managed to observe the evolution of self-heating areas, i.e., the appearance of hot spots, their migration and their disappearance were observed. The method used is relatively rapid, low-cost and field temperature measurements are not essential.
CFD simulations of the effect of wind on the spontaneous heating of coal stockpiles
风对煤堆自发热影响的CFD模拟
Fuel, Volume 118, 15 February 2014, Pages 107-112
Abstract: A commercial CFD software program, fluent, was used to study the effect of wind on the spontaneous heating process of a coal stockpile. A two-domain model was developed to simultaneously solve the governing equations of an open porous medium (coal stockpile domain) situated in a homogeneous atmosphere (wind flow domain). Simulations with air blowing from a fixed direction as well as real fluctuations of the airflow both in velocity and direction were performed.
Numerical calculations confirmed the promoting role of wind on the dynamics of the development of spontaneous heating. Under the conditions of the simulations, three possible shifts of the hot spot in the stockpile were distinguished when coal undergoes the self-heating process:
(1)Shift of the hot spot to the pile surface when spontaneous heating of coal is in progress.
(2)Movement of the hot spot inwards the stockpile as the wind speed increases.
(3)Transfer of the hot spot from the upper part of the stockpile to the lower part when the self-heating process progresses. Such movement was found for wind speeds ⩽3 m s−1 and clearly is mainly connected with the effect of buoyancy.
Investigation of the spontaneous combustion susceptibility of coal using the pulse flow calorimetric method: 25 years of experience
用脉流热量法研究煤自燃倾向性：25年之经验
Fuel, Volume 125, 1 June 2014, Pages 101-105
Abstract: The paper summarises 25 years of experience with pulse flow calorimetry (PFC) as a method to assess the potential of coals to spontaneously heat up using the values of oxidation heat q30 (W kg−1). During the period, about 300 coals of various rank and with natural moisture content were investigated, the maximum propensity to oxidation being found in subbituminous coals with moisture content of about 20%. The highest value of oxidation heat q30 was found to be 10.5 W kg−1. Oxidatively altered bituminous coals are presented as coals of evidently increased ability to oxidize, and the reasons for the increased oxyreactivity are reported. Limiting values of q30 heat are then given to rank the coals according to the categories of self-heating risk. Finally, a comparison between oxidation heat q30 and the values of the initial rate of heating (IRH) of adiabatic oxidation tests is presented.
