1. School of Information and Electrical Engineering, China University of Mining and Technology, Xuzhou 221008, China
2. College of Physics & Electrical Engineering, Jiangsu Normal University, Xuzhou 221116, China
Abstract:Spectral distortions are common in quantitative terahertz spectra measurement of granulated coal. These spectra warping in the spectroscopy are caused by electromagnetic wave scattering due to coal particles and HDPE intergranularpore-space developed during tableting process consisted in the tablet. In this paper, an equivalent coal-HDPE mixture tablet is built according to the two substances’ structural differences. The scattering contributions of coal particles and air voids are investigated by using the theories of Foldy-Twersky EFA and iterative Waterman-Truell EFA in the frequency from 2 to 3.5 THz, establishing a quantitative analytical model of intrinsic absorption spectra of coal. The studied 6 samples are mixtures of HDPE powder and granulated coal, whose grain sizes varies from one another while the volume concentration is kept constant. Experimental data are recorded with a THz-TDS setup. The scattering loss caused by air voids is more notable when the size of coal particle is smaller than 38.5 μm. When the coal particle size is between 38.5 and 55 μm, it could be observed that the extinction caused by coal particles is more or less the same with it by the air voids. With the increase of coal particle diameter, the scattering contribution of granulated coal to the total propagation loss becomes evident. The correlation coefficient and RMSE between the original and calibrated spectra indicated that the studied quantitative analytical model could significantly reduce the effect of scattering to the measured THz spectrum of coal sample when coal particle size smaller than 105 μm. This study could provide a theoretical basis for quantitative terahertz spectra measurement of coal.
[1] ZHANG Lei,MA Wei-guang,YAN Xiao-juan,et al(张 雷,马维光,闫晓娟,等). Acta Sinica Quantum Optica(量子光学学报), 2011, 17(1): 70.
[2] ZHAO Bo,YANG Yong-zhong,LIU Li-ting,et al(赵 博,杨永忠,刘丽婷,等). Clean Coal Technology(洁净煤技术), 2015, 21(3): 79.
[3] Rafa M, Iwona J, Krystyna K. International Journal of Coal Geology, 2014, 134-135(2014): 17.
[4] Zhan H, Wu S, Bao R, et al. Fuel, 2015, 143: 189.
[5] LIU Ling-yu,YANG Chuan-fa,ZHANG Xian-sheng,et al(刘陵玉,杨传法,张献生,等). Journal of China Coal Society(煤炭学报), 2016,(2): 497.
[6] XU Chang-hong,TENG Xue-ming,ZHAO Hui,et al(许长虹,滕学明,赵 卉,等). Modern Scientific Instruments(现代科学仪器), 2013(04): 228.
[7] TENG Xue-ming,ZHAO Kun,ZHAO Hui,et al(滕学明,赵 昆,赵 卉,等). Modern Scientific Instruments(现代科学仪器), 2011,(6): 19.
[8] Tanno T, Oohashi T, Katsumata I, et al. Fuel, 2013, 105: 769.
[9] Zhan H, Zhao K, Xiao L. Energy, 2015, 93: 1140.
[10] Garet F, Hofman M, Meilhan J, et al. Applied Physics Letters, 2014, 105(3): 31106.
[11] Xu W, Xie L, Zhu J, et al. Food Chemistry, 2017, 218: 330.
[12] Herrmann M, Tani M, Watanabe M, et al. Optoelectronics, IEE Proceedings, 2002, 149(3): 116.
[13] Bandyopadhyay A, Sengupta A, Barat R B, et al. International Journal of Infrared and Millimeter Waves, 2007, 28(11): 969.
[14] Zurk L M, Orlowski B, Winebrenner D P, et al. Journal of the Optical Society of America B, 2007, 24(9): 2238.
[15] LI Zhi,LIAN Fei-yu(李 智,廉飞宇). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2016, 36(6): 1666.
[16] Kerker M, Loebl E M. The Scattering of Light and Other Electromagnetic Radiation: Academic Press, 1969. 688.
[17] Mandt C E, Kuga Y, Tsang L, et al. Waves in Random Media, 1992, 2(3): 225.
[18] Giusto A, Saija R, Iati M A, et al. Appl. Opt., 2003, 42(21): 4375.
[19] Molero M, Segura I, Aparicio S, et al. European Journal of Environmental & amp; Civil Engi., 2011.
[20] Kaushik M, Ng B W, Fischer B M, et al. Applied Physics Letters, 2012, 100(24111024).
[21] Duvillaret L, Garet F, Coutaz J L. Appl. Opt., 1999, 38(2): 409.
[22] Shen Y C, Taday P F, Pepper M. Applied Physics Letters, 2008, 92(0511035).
[23] Franz M, Fischer B M, Walther M. Applied Physics Letters, 2008, 92(2): 21107.
[24] YAN Fang,ZHANG Zhao-hui,ZHAO Xiao-yan,et al(燕 芳,张朝晖,赵小燕,等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2014, 34(6): 1473.
[25] WANG Xin,MIAO Shu-guang,DING En-jie(王 昕,苗曙光,丁恩杰). Journal of China University of Mining & Technology(中国矿业大学学报), 2016, 45(4): 739.