Abstract
The paper describes the results of research on the applicability of the ground penetrating radar (GPR) method for remote sensing and monitoring of the underground coal gasification (UCG) processes. The gasification of coal in a bed entails various technological problems and poses risks to the environment. Therefore, in parallel with research on coal gasification technologies, it is necessary to develop techniques for remote sensing of the process environment. One such technique may be the radar method, which allows imaging of regions of mass loss (voids, fissures) in coal during and after carrying out a gasification process in the bed. The paper describes two research experiments. The first one was carried out on a large-scale model constructed on the surface. It simulated a coal seam in natural geological conditions. A second experiment was performed in a shallow coal deposit maintained in a disused mine and kept accessible for research purposes. Tests performed in the laboratory and in situ conditions showed that the method provides valuable data for assessing and monitoring gasification surfaces in the UCG processes. The advantage of the GPR method is its high resolution and the possibility of determining the spatial shape of various zones and forms created in the coal by the gasification process.
Highlights
In recent times, the traditional combustion of fossil fuels, and coal, has acquired a bad reputation due to air pollution and its impact on climate (Gaffney and Marley 2009; Shindell and Faluvegi 2010)
The advantage of the ground penetrating radar (GPR) method is its high resolution and the possibility of determining the spatial shape of various zones and forms created in the coal by the gasification process
This paper describes the results of two GPR surveys conducted on a model and during inseam underground coal gasification with the application of 3D methods for data visualization
Summary
The traditional combustion of fossil fuels, and coal, has acquired a bad reputation due to air pollution and its impact on climate (Gaffney and Marley 2009; Shindell and Faluvegi 2010). According to Eq (4), the amplitude of electromagnetic wave reflection depends on the difference of complex impedances on the interfaces created in the coal by the gasification process (coal–char, coal–gas, char– gas) or only from values of dielectric permittivity, if we use Eq (5). The energy of reflections depends mainly on the spatial distribution of the variously transformed (carbonized or burnt out) parts of the coal mass (zones characterized by different permittivity and conductivity values), when we compare images recorded before and after the gasification process. (6) and (7), it can be estimated that when the coal has a temperature of several hundred degrees Celsius, the attenuation of waves in the seam rapidly drops This can significantly increase the penetration range of electromagnetic pulses in real geologic conditions and the overall penetration performance of radar systems. Coal (hard) Coke (char) Carbon black Coal tar Coal powder (fine) Fly ash Hydrogen
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