Application of a GPR technique for the monitoring of simulated underground coal gasification in a large‐scale model

Abstract

Underground Coal Gasification (UCG) involves the recovery of energy from a coal deposit via the use of controlled combustion. A reactor equipped with apparatus enabling the analysis of temperature profiles and gas composition was constructed for the simulation of underground conditions, both with respect to the coal seam and the surrounding stratum characteristics. A three day experiment was performed in which large blocks of lignite were gasified, with an average gasification rate of 5 kg/h. The ground‐penetrating radar (GPR) reflection method was used to monitor the process and observe physical and structural changes taking place within the gasification zone; radar images of the different stages of the process were then recorded and analysed. The experiment demonstrated the potential for successful application of radar techniques in the observation and monitoring of the coal gasification process in a natural environment. Whereas the gasification of coal in shallow seams could be monitored by surface measurements, that of deep seams in operating coal mines or coal deposits could be monitored by measurements made from galleries or boreholes.

Monitoring and Control in Underground Coal Gasification: Current Research Status and Future Perspective

“…Mellors et al [48] applied electrical resistivity tomography and interferometric synthetic aperture radar techniques into UCG monitoring. Kotyrba et al [8] used ground penetrating radar to remote monitor the image of mass loss (porosity, crack) area in coal during and after UCG process. Unfortunately, such methods are in the simulation stage.…”

“…Considering high temperature humidity and closed environment, it is difficult to effectively monitor and control the UCG process to improve the quality of the syngas. Therefore, scholars in various countries have carried out a series of meaningful research on the monitoring and control in UCG, such as the GPR (Ground Penetrating Radar) technique for the monitoring [8,9], and study on controlling the combustion state in the gasification process [10][11][12][13][14]. There are few related studies, technical means remaining on paper, or at the experimental teaching level, and basic research is almost blank.…”

Sensing underground coal gasification by ground penetrating radar

“…According to Eq. (3), this also causes a change in the effective dielectric permittivity of coal within the gasification zone (Kotyrba and Stańczyk 2013).…”

“…The first trials to apply the radar method for imaging of gasification voids were conducted within the RFCS-funded project (acronym HUGE) on a large-scale model simulating underground conditions (Stańczyk et al 2010). Collected radar data were processed with 2D algorithms (Kotyrba and Stańczyk 2013). This procedure enabled two reflecting interfaces to be determined within the coal, corresponding to gasification and cavity surfaces.…”

Imaging the Underground Coal Gasification Zone with Microgravity Surveys

“…Earlier researches made with the radar method in a large-scale model simulating conditions in the deposit show that in a block of pure coal (without impurities of other minerals) which undergoes the gasification process, in the limited volume there are at least three areas of different structure and physicochemical properties (Kotyrba and StaĔczyk 2013): coal in natural form, physically and chemically transformed coal with char of various rank, cavern. Because of that, before the measurements we analysed theoretically, using a 2D modelling method, the influence of the three types of structure of a coal seam í models 1, 2, and 3 í on the local gravity field in the area where the gasification process occurs.…”