Temperature characteristic of crushed coal under liquid coolant injection: a comparative investigation between CO 2 and
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Temperature characteristic of crushed coal under liquid coolant injection: a comparative investigation between CO2 and N2 Zhijin Yu1,2 · Yu Gu1 · Song Yang1 · Jun Deng1 Received: 20 May 2020 / Accepted: 31 July 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract For large-scale underground coal fires (LUCF), how to achieve significant cooling was a key to prevent and extinguish spontaneous combustion of coal in mining-out area. The liquid CO2 or liquid N2 injection, which has stronger cooling, wider coverage, and inerting effect, was a reliable technology that can improve the efficiency of LUCF control in the coal industry. However, before application, it is of fundamental importance for understanding of the heat transfer mechanisms and temperature variations of crushed coal during and after liquid CO2/N2 injection. In this paper, a series of laboratory experiments was designed and used to research the process about the phase change and convective diffusion of liquid CO2 and liquid N 2 in coal under controlled conditions. Liquid C O2/N2 was separately injected into a cylindrical container which is filled with crushed coal, and the transient variation of coal temperature was measured on specified sites in the system by using temperature sensors. A comparative analysis between the liquid C O2 and liquid N 2 injection for temperature characteristic of coal was conducted. In addition, the temporal-spatial characteristics of the cooling energy caused by latent heat of phase transformation of liquid CO2 and liquid N 2 were revealed, and its correlation with the transient coal temperature field was identified. Keywords Coal fires · Heat transfer · Temperature variations · Phase transition · Cooling capability
Introduction Thermodynamic disaster is considered as the most hazardous issue particularly for coal mine, which resulted in immense financial loss and casualties [1–3]. In general, the occurrence of thermodynamic disaster is associated with temperature and gas concentration, for instance coal fires caused by self-heating; both oxygen content and heat accumulated conditions play critical roles [2, 4, 5]. In addition, the oxidation of coal process and heat released will significantly accelerate once the temperature increases, which lead to a higher risk of spontaneous combustion of coal [6, 7]. Hence, it has practical significance to reduce the ambient * Zhijin Yu [email protected] 1
College of Safety Science and Engineering, Xi’an University of Science and Technology, No. 58, Yanta Rd., Xi’an 710054, Shaanxi, China
Mineral Engineering Postdoctoral Station, Xi’an University of Science and Technology, No. 58, Yanta Rd., Xi’an 710054, Shaanxi, China
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temperature for inhibiting self-ignition of coal. However, as the lack of the reliable detected and predicted methods, effective cooling is always difficult, resulting in the accidents caused by self-ignition of coal to become increasingly severe [8, 9]. Consequently, to mitigate the risk of coal fires and guarantee the mining safety, the
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