Abstract
Coal fires, including both underground and coal waste pile fires, result in large losses of coal resources and emit considerable amounts of greenhouse gases. To estimate the annual intensity of greenhouse gas emissions and the loss of coal resources, estimating the annual loss from fire-influenced coal seams is a feasible approach. This study assumes that the primary cause of coal volume loss is subsurface coal seam fires. The main calculation process is divided into three modules: (1) Coal fire quantity calculations, which use change detection to determine the areas of the different coal fire stages (increase/growth, maintenance/stability and decrease/shrinkage). During every change detections, the amount of coal influenced by fires for these three stages was calculated by multiplying the coal mining residual rate, combustion efficiency, average thickness and average coal intensity. (2) The life cycle estimate is based on remote sensing long-term coal fires monitoring. The life cycles for the three coal fire stages and the corresponding life cycle proportions were calculated; (3) The diurnal burnt rates for different coal fire stages were calculated using the CO2 emission rates from spontaneous combustion experiments, the coal fire life cycle, life cycle proportions. Then, using the fire-influenced quantity aggregated across the different stages, the diurnal burn rates for the different stages and the time spans between the multi-temporal image pairs used for change detection, we estimated the annual coal loss to be 44.3 × 103 tons. After correction using a CH4 emission factor, the CO2 equivalent emissions resulting from these fires was on the order of 92.7 × 103 tons. We also discovered that the centers of these coal fires migrated from deeper to shallower parts of the coal seams or traveled in the direction of the coal seam strike. This trend also agrees with the cause of the majority coal fires: spontaneous combustion of coalmine goafs.
Highlights
Underground coal fires are the cause of remarkable losses of coal resources and serious environmental problems, such as the emission of CO2 and other noxious gasses, land subsidence and heavy metal contamination [1,2,3,4]
Estimating the volume lost from coal seams is a preliminary step for the evaluation of both the coal resource loss and the greenhouses gas (GHG) emissions
As suggested by Van Dijk et al [5], the methods for the quantification of coal-fire-related GHG emissions can be grouped into three types: direct measurements of gas emission fluxes extrapolated to estimate the total gas emissions; calculation of the burnt volume of coal based on mining knowledge and 3D modeling of the coal seam and strata, and conversion of that volume to an estimate of gas emissions; and calculation of the amount of subsurface burning coal based on the energy release
Summary
Underground coal fires are the cause of remarkable losses of coal resources and serious environmental problems, such as the emission of CO2 and other noxious gasses, land subsidence and heavy metal contamination [1,2,3,4]. As suggested by Van Dijk et al [5], the methods for the quantification of coal-fire-related GHG emissions can be grouped into three types: direct measurements of gas emission fluxes extrapolated to estimate the total gas emissions; calculation of the burnt volume of coal based on mining knowledge and 3D modeling of the coal seam and strata, and conversion of that volume to an estimate of gas emissions; and calculation of the amount of subsurface burning coal based on the energy release.
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