Ren Shuai-Jing, Zhang Yan-Ni, Song Ze-Yang, Xiao Yang, Deng Jun, Shu Chi-Min
School of Safety Science and Engineering, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China; School of Energy Engineering, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China.
School of Safety Science and Engineering, Xi'an University of Science and Technology, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China; Shaanxi Key Laboratory of Prevention and Control of Coal Fire, No. 58, Yanta Mid. Rd., Xi'an, Shaanxi 710054, PR China.
Sci Total Environ. 2023 Nov 1;897:165475. doi: 10.1016/j.scitotenv.2023.165475. Epub 2023 Jul 12.
Coal spontaneous combustion often wastes resources and causes environmental pollution. Rapid and accurate identification of high temperature areas in coal is essential to reducing such combustion and environmental pollution. The acoustic thermometry method has the benefits of large temperature measurement space, non-contact, and high interference resistance. Determining the attenuation characteristics of acoustic waves in loose coal is the basis and premise for realizing acoustic temperature measurement. Four types of bituminous coal were scanned by computer tomography equipment. A self-designed acoustic attenuation test device was used to test coal samples under different temperatures and particle sizes. The study result demonstrates that the distribution characteristics of loose coal voids are mainly related to the particle size. The smaller the particle size range, the more uniform the void distribution. As the size of the coal particles increases, the voids become larger. The acoustic attenuation coefficients of four coal samples showed an increasing trend as frequency increased. The influence of coal particle size distribution on the acoustic attenuation coefficient was greater than that of temperature and metamorphic degree. The peak values of coal sound attenuation for different particle sizes were around 400, 700, 1100, and 1600 Hz. This indicated that the distribution of voids was the main factor affecting the propagation of acoustic waves. By analysing the attenuation mechanism of the acoustic wave in loose coal, the attenuation of acoustic temperature measurement signal was caused by the combined effect of loose coal on acoustic wave absorption and scattering. The study results provide theoretical support for the realization of acoustic wave detection of high temperature point in loose coal spontaneous combustion.
