Numerical modelling of the self-heating process of a wet porous medium

Ejlali, Arash; Mee, D. J.; Hooman, Kamel; Beamish, B. B.

doi:10.1016/j.ijheatmasstransfer.2011.08.025

Cited by 55 publications

(16 citation statements)

References 26 publications

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“…Several studies demonstrated that the interaction of coal with water like wetting can also generate heat and it reaches to a general consensus that moisture exhibits either promoting or inhibiting effects on coal oxidation rate but fundamental mechanism especially to a kinetic sense is scarce [1, [43][44][45][46]. As chemical effects of moisture were not understood completely, a few numerical models were developed to investigate only physical effect of moisture on self-heating of coal stockpile and it was indicated interaction of coal with moisture is an efficient heat transfer mechanism in which the vaporisation and diffusion of water from a hot region, followed by condensation in a cooler region, is accompanied by a considerably higher effective rate of heat transfer than that which can occur by conduction alone [21,26,37,47]. The efficient heat transfer mechanism was also termed as "heat pipe" effect in some literatures and the "heat pipe" effect usually manifested itself by leading to a levelling of temperature (80~90 o C) in a coal stockpile [21,26].…”

Section: Brief Mechanism Of Spontaneous Heating Of Coal Stockpilementioning

confidence: 99%

“…To date with the advance of Computational Fluid Dynamics (CFD) modelling techniques, predictable interpretation of self-heating of piled carbonaceous material within reasonable engineering accuracy becomes more approachable [9,14,[34][35][36][37][38][39][40][41]. Among these works, Moghtaderi et al [34]studied the effects of wind on self-heating behaviour of coal stockpile and found forced convection plays a critical role in dynamics of flow field inside the stockpile and thereby affects the self-heating process.…”

Section: Introductionmentioning

confidence: 99%

“…Yuan and Smith studied effects of coal properties on self-heating problem in underground coal mine goaf areas by a CFD model and later on developed a 3D equilibrium thermal model to simulate spontaneous heating in a large-scale coal chamber with a forced ventilation system [35,36]. Ejlali et al [37] improved preceding models by employing a non-equilibrium thermal approach and found the maximum temperature is a function of porosity of porous pile, moisture content and Darcy number. Taraba and Michalec [38] numerically investigated the effects of longwall advance rate on spontaneous heating in goaf areas by a CFD model.…”

Section: Introductionmentioning

confidence: 99%

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Transient CFD modelling of low-temperature spontaneous heating behaviour in multiple coal stockpiles with wind forced convection

Zhang

Liang

Ren

et al. 2016

Fuel Processing Technology

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G. (2016). Transient CFD modelling of low-temperature spontaneous heating behaviour in multiple coal stockpiles with wind forced convection. Fuel Processing Technology, 149 55-74.Transient CFD modelling of low-temperature spontaneous heating behaviour in multiple coal stockpiles with wind forced convection AbstractSpontaneous heating of coal stockpile has long been a thermal dynamic hazard during coal storage, processing, and transport. A transient non-equilibrium thermal CFD model has been developed to study the low-temperature self-heating behaviour of coal in multiple stockpiles under different prevailing wind conditions. Modelling results from the initial steady wind flow simulation indicate that a wake region can be induced on the leeward side of each coal stockpile. Pressure coefficient drops when the wind stream encounters or leaves a stockpile and the pressure coefficient profiles of multiple stockpiles tend to have more resemblance with a wider spacing. The first stockpile acts like a wind barrier to the adjacent stockpiles and the maximum temperature of it tends to be the first approaching the critical temperature. A 'hot spot' will develop and then migrate towards deep regions in each of these stockpiles that are loosely compacted under higher wind velocity conditions. Wind velocity and porosity of stockpile have significant influences on self-heating behaviour of the stockpiles and transport pattern of gaseous products liberated by coal oxidation. Compacting stockpiles from loosely packed scenario to slightly packed scenario might not be able to slow down the temperature rising rate at low-temperature range but could considerably minimize the volume of deteriorated coal. The highest temperature rising profiles of the stockpiles located in downwind side can approach to that of the first stockpile, particularly when they are more widely stacked. Stacking coal stockpiles as close as practically possible is recommended to maximise the "protection" of adjacent stockpiles but would cause undesirable accumulation of carbonic gases. Stockpiles in low height and gentle slope will have a prolonged safe storage period, especially for the first stockpile directly facing the wind direction. However, it may not slow down the self-oxidation process of the adjacent stockpile at very initial stage due to "weakened protection" of the first stockpile. This study has practical reference to coal industry especially where multiple coal stockpiles require to be constructed. 13The first stockpile acts like a wind barrier to the adjacent stockpiles and the maximum temperature of it tends to 14 be the first approaching the critical temperature. A 'hot spot' will develop and then migrate towards deep 15 regions in each of these stockpiles that are loosely compacted under higher wind velocity conditions. Wind 23Stockpiles in low height and gentle slope will have a prolonged safe storage period, especially for the first 24 stockpile directly facing the wind direction. However, it may not slow down the self-oxidation process o...

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Section: Brief Mechanism Of Spontaneous Heating Of Coal Stockpilementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Transient CFD modelling of low-temperature spontaneous heating behaviour in multiple coal stockpiles with wind forced convection

Zhang

Liang

Ren

et al. 2016

Fuel Processing Technology

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“…en, the risk of spontaneous combustion of coal in the gob under a different advance rate of working face and air leakage intensity was predicted [26]. In the model established by Ejlali et al [27] and Lohrer et al [28], the effect of moisture on the heat transfer process was considered. Yang et al [29] theoretically analyzed the influence of changes in air volume and pressure on the spontaneous combustion status of coal in the gob and divided the range of the oxidation zone in the gob by numerical simulation under different conditions.…”

Section: Introductionmentioning

confidence: 99%

Multifield Coupled Dynamic Simulation of Coal Oxidation and Self-Heating in Longwall Coal Mine Gob

Song

Wang

Jiang

et al. 2020

Mathematical Problems in Engineering

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The spontaneous combustion of residual coal in coal mine gob has long been a problem and poses a threat to the safe production of coal. Therefore, it is of great significance to conduct an in-depth study of the oxidation and self-heating progress of residual coal in the gob. Considering that the geometric dimensions and physical characteristics of the gob will change during the advance of the working face, the purpose of the present paper is to determine how the coal self-heating develops during and after coal mining. A fully coupled transient model including gas flow, gas species transport, and heat transfer in the gob and the butt entries, as well as heat transfer in the surrounding strata, is developed to quantify the evolution of coal self-heating in gob during and after mining. The model was solved by COMSOL Multiphysics package and then verified by comparing the field data with the simulated data. On this basis, parametric studies including the influences of the surrounding strata temperature, airflow temperature, coal-rock particle size, and advance rate of the working face on coal oxidation and self-heating in the gob were conducted. The results show that a tailing phenomenon of the high-temperature area is formed on the air inlet side of the gob during mining, and the temperature in the high-temperature zone decreases gradually due to the accumulation and compaction of the gob and heat dissipation to the surrounding strata. Also, although the temperature in gob increases gradually after the stopping of mining, the high-temperature area migrates towards the working face. Moreover, when the temperature of the surrounding strata is consistent, different ventilation temperatures have no obvious effect on the maximum temperature of the gob at the initial mining stage, whereas the higher ventilation temperature results in the higher self-heating temperature after several days of mining. Finally, the smaller average particle size or faster advance rate results in a lower maximum temperature of gob.

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“…Since low rank coals have larger internal surface which is proportional to the heat of wetting (Das and Hucka, 1986). The effects of moisture content and humidity on porous medium or stockpiled coal have been simulated using numerical modeling techniques (Gong, 2000;Gray et al, 2002, Zarrouk, 2004Ejlali et al, 2011). An improved analytical model is developed based on mobile core theory, different from the Arrhenius kinetics on moisture condensation used in the numerical modeling.…”

Section: Model Developed For Quantifying the Effects Of Coal Quality mentioning

confidence: 99%

Experimental and Theoretical Studies of Kinetics and Quality Parameters to Determine Spontaneous Combustion Propensity of U.S. Coals

Wang

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Numerical modelling of the self-heating process of a wet porous medium

Cited by 55 publications

References 26 publications

Transient CFD modelling of low-temperature spontaneous heating behaviour in multiple coal stockpiles with wind forced convection

Transient CFD modelling of low-temperature spontaneous heating behaviour in multiple coal stockpiles with wind forced convection

Multifield Coupled Dynamic Simulation of Coal Oxidation and Self-Heating in Longwall Coal Mine Gob

Experimental and Theoretical Studies of Kinetics and Quality Parameters to Determine Spontaneous Combustion Propensity of U.S. Coals

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