Abstract
This article presents the results of laboratory tests regarding the influence of high temperatures on changes in the strength and structural parameters of rocks that are present in the immediate vicinity of a gasification channel. Sandstone and claystone samples were heated at 300 °C, 600 °C, 900 °C and 1200 °C. Additionally, the heated samples were placed in water for 24 h. The results of the laboratory tests were used in the numerical simulation using RS2 software. The main goal of modeling was to determine the extent of the rock destruction zone around the gasification channel for dry and wet rock masses. In the numerical simulations, three widths of the gasification channel and three ranges of high-temperature impact were modeled. On the basis of the obtained results, it was found that the extent of rock destruction, both in the roof and in the floor, is greater by several percent for a wet rock mass. For the first time, this research presents the effect of water on heated rock samples in terms of the underground coal gasification process. The results of laboratory tests and numerical simulations clearly indicate a reduction in strength, deformation and structural parameters for the temperature of 1200 °C.
Highlights
Underground coal gasification is a prospective method for obtaining useful minerals, in particular from deposits that are considered sub-balance
Significant amounts of heavy metals may be released from coal and the ashes generated during gasification in volatilization processes, which are favored by the high temperature of the process and the presence of numerous chemical factors [7]
The oxidizing agent may be supplied to the coal seam by means of: roadway inside the body of coal; through holes made in the body of coal between roadways; and blind holes to which the oxidizing agent is led through heat-resistant pipes [32]
Summary
Underground coal gasification is a prospective method for obtaining useful minerals, in particular from deposits that are considered sub-balance. First of all, it is an environmentally friendly method due to the lack of waste generation on the surface [1] and a much smaller number of preparatory excavations [2]. Significant amounts of heavy metals may be released from coal and the ashes generated during gasification in volatilization processes, which are favored by the high temperature of the process and the presence of numerous chemical factors [7]. Heat conduction through the minerals is partially absorbed as energy. Feng et al [13] and Deming et al [14] stated that the gasification reaction occurs on the surface of micropores
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