Effect of coal rank on structure and dielectric properties of chars

Liu, Haiyu; Xu, Liang; Jin, Yan; Fan, Baoguo; Qiao, Xiaolei; Yang, Yong Suk

doi:10.1016/j.fuel.2015.03.008

Cited by 73 publications

(21 citation statements)

References 52 publications

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“…Xu et al studied the influence of the crystallite structure on the dielectric properties of coal chars [30]. Liu studied the effect of coal rank on the dielectric properties through structural differences in various coal chars [31]. Emslie and Lagace.…”

Section: Plos Onementioning

confidence: 99%

Propagation of ground penetrating radar waves in Chinese coals

et al. 2020

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This paper reports an experimental study on the electrical properties of five coal samples taken from various Chinese coal mines. The dielectric permittivity and specific resistivity of grinded coal samples subjected to electromagnetic (EM) fields in a wide frequency spectrum were determined. Based on the experimental data, a set of approximating equations of the change in electric properties the 100-1000 MHz frequency region was obtained. These equations, along with EM equations for EM speed and attenuation, were used for modeling and studying radar-wave propagation in a coal seam and radar-wave reflection from the body of miners trapped in collapsed tunnels. The modeling concept assumes that a radar transducer with the dominating frequency of 500 MHz is lowered through a vertical or inclined rescue borehole to the depth of the coal seam. It is assumed that only the miner is present in the part of the tunnel that did not collapse. Thus, in the path of the radar wave from the transducer to the human body, only one geological interface reflecting the radar signals is present (coal-air) and one is connected with human body. The human (acting as the reflector) can be located at various distances from the tunnel face; this factor was included in the analyzed geometrical model. Based on the modeling results of different thickness coal seams (2, 3, 4, 5, 6, 7, 8m), conclude that a radar wave reflected from a human body can be reliably measured, when the distance between the human and the transducer is not exceed 8m.

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Section: Plos Onementioning

confidence: 99%

Propagation of ground penetrating radar waves in Chinese coals

et al. 2020

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“…Microwave desulfurization is based on interaction between sulfur‐containing components in coal and microwave. Dielectric materials response to microwave field through their complex permittivity and absorb the electromagnetic energy, which is transformed into heat 13 . Hence, knowledge about the dielectric properties of inorganic sulfur and organic sulfur components in coal is the key to control the process of microwave desulfurization.…”

Section: Introductionmentioning

confidence: 99%

Influence of dielectric property of organic sulfur compounds on coal microwave desulfurization

Tao

Yang

2020

Asia-Pacific J Chem Eng

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The present study aims to reveal the influence mechanism of organic sulfur structures and microwave frequency on its dielectric property and establish the relationship between the dielectric properties of organic sulfur components in coal and the efficiency of microwave desulfurization. Results showed that the different polarization mechanisms of organic sulfur compounds lead to the real part of complex permittivity decreased initially and then increased with increasing frequency. At the same time, the real parts of the complex permittivity of mercaptan and thioether compounds were higher than that of thiophene, which were caused by their different structures. As the frequency increased, the loss tangent, microwave penetration depth, and absorption index showed decline in oscillation. The loss tangent was mainly related to the polarization mechanism; both polarization mechanism and microwave wavelength had effect on the changes of microwave penetration depth and absorption index. Mercaptan and thioether compounds were more effective at converting microwave energy into heat energy. After microwave processing, the relative content of mercaptan (thioether) in GZ, CQ, and SX coals decreased from 37.38%, 36.93%, and 40.02% to 27.34%, 29.26%, and 26.67% and of thiophene increased from 47.61%, 53.35%, and 49.54% to 58.76%, 59.09%, and 60.38%.

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“…The degree of microwave heating depends on the dielectric properties of the coal, 27 and in particular its coal rank and carbon layer stacking in combination with aromatic cabin content. 28 Although coal as a bulk material at room temperature has relatively low dielectric properties, coal constituents such as moisture, bound hydroxyl groups and pyrite have significantly higher dielectric loss than the organic component, [29][30][31] and can be selectively heated. Water trapped inside porous materials has the potential to superheat to temperatures well above 100 °C.…”

Section: Introductionmentioning

confidence: 99%

Formation of Metallurgical Coke within Minutes through Coal Densification and Microwave Energy

Williams

Ure²,

Stevens

et al. 2019

Energy Fuels

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This paper shows how feedstock densification gives rise to a step change in the time required to create a metallurgical grade coke using microwave energy. Five densified coking and noncoking coals were heated in a multi-mode microwave 2450 MHz cavity for varying treatment times (2-20 minutes) with a fixed power input (6 kW). Proximate analysis, intrinsic reactivity, coke reactivity, dielectric properties, and petrographic analysis of the coals and microwave produced lump cokes were compared to a commercial lump coke. Densifying the sample prior to microwave treatment enabled a dramatic acceleration of the coking process when combined with targeted high microwave energy densities. It was possible to form fused coke lump structures with only 2 minutes of microwave heating compared to 16-24 hours via conventional coking. Anisotropic coke morphologies (lenticular and circular) were formed from non-coking coal that are not possible with conventional coking and increasing treatment time improved overall coke reflectance. Three of the coals produced coke with equivalent coke reactivity index values of 20-30, which are in the acceptable range for blast furnaces. The study demonstrated that via this process, non-coking coals could potentially be used to produce high quality cokes, potentially expanding the raw material options for metallurgical coke production.

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Effect of coal rank on structure and dielectric properties of chars

Cited by 73 publications

References 52 publications

Propagation of ground penetrating radar waves in Chinese coals

Propagation of ground penetrating radar waves in Chinese coals

Influence of dielectric property of organic sulfur compounds on coal microwave desulfurization

Formation of Metallurgical Coke within Minutes through Coal Densification and Microwave Energy

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