Experimental investigation on spontaneous combustion of coal affected by exothermic reaction of polyurethane in undergro
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Experimental investigation on spontaneous combustion of coal affected by exothermic reaction of polyurethane in underground coal mines Yibo Tang1 · Pengwei Guo1 Received: 25 February 2020 / Accepted: 25 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Organic elastomers such as polyurethane are widely used as a filling material in underground coal mines. However, the risk of fire hazard in coal seams is increased due to the flammability of polyurethane. Laboratory tests illustrate that in a thermostatic reactor with initial temperature of 25 °C, the temperature during the production of polyurethane increases up to > 140 °C. Adiabatic oxidation experiments and TG–DTG analysis showed that the heating rate of the mixed samples of polyurethane and coal was higher than that of any single component in the initial oxidation stage. From the initial temperature to 100 °C, increasing the proportion of polyurethane was conducive to the acceleration of temperature rise. From 0.180 to 0.850 mm, the self-heating rate was inversely proportional to the particle size. At the initial stage, the low ventilation rate promoted the spontaneous combustion of mixed samples, but when the temperature is > 70 °C, an opposite trend was seen. Kinetic parameters suggested that the activation energy decreases with the introduction of polyurethane. According to the mathematical model, the variation of the spontaneous combustion period of coal and polyurethane was predicted. Keywords Spontaneous combustion of coal · Polyurethane · Adiabatic oxidation · Fire risk List of symbols A Pre-exponential factor (s−1) E Activation energy (kJ mol−1) R Universal gas constant (J mol−1 K−1) CS Constant in Starink formula G(a) Integral mechanism function Q Energy (J) R(T) Heat flow rate (J s−1 g−1) m(T) Sample mass (g) 𝜔(T) Sample moisture content (%) cs (T) The specific heat capacity of the sample (J g −1 K−1) cw The specific heat of water (J g−1 K−1) h The latent heat of evaporation of water (J g−1) m0 The initial mass of the sample (g) 𝜔0 The percentage of water that evaporates (%) Ae The heat dissipation surface area (m2) Te Environment temperature (K) Ai The heated surface area (m2)
* Yibo Tang [email protected] 1
College of Safety and Emergency Management Engineering, Taiyuan University of Technology, Taiyuan 030024, China
Ti Instrument temperature (K) a Conversion degree (%) Greek letters 𝛼 Coefficient of heat dispersion (W m−2 K−1) 𝛽 Heating rate (K min−1) 𝜆 Coefficient of heat transfer (W m−2 K−1)
Introduction Mine fire hazards are one of the serious disasters in underground colliery. Based on origin, the hazards can be classified into either exogenous fire or spontaneous fire [1]. Spontaneous fires have attracted extensive attention because of their widespread occurrence in global coal-producing areas [2, 3]. However, exogenous fires usually occur in confined underground spaces and develop more rapidly and intensely, often resulting in huge casualties and property losses [4, 5]. In general, e
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