Elsevier

Powder Technology

Volume 366, 15 April 2020, Pages 294-304
Powder Technology

Short Communication
Transient temperature evolution of pulverized coal cloud deflagration in a methane–oxygen atmosphere

https://doi.org/10.1016/j.powtec.2020.02.042Get rights and content

Highlights

  • The 3D temperature of coal particle cloud explosion in a CH4/O2 atmosphere was simulated.

  • The temperature evolution was quantitatively and qualitatively analyzed.

  • CFD simulations explained particle aggregation in previous experiments.

  • Coupling and heat-mass transfer between coal particles and gas was revealed.

Introduction

Despite the rapid growth in coal yield owing to advancement of mining technology in recent decades, coal mine gas/dust explosions are still a major hazard in coal production [1,2]. According to reports [[3], [4], [5]], death in China caused by gas/dust explosions occurred in more than 50% of the coal mine accidents from 2001 to 2016. Worse still, the high temperature, high pressure, and toxic substances such as methane released in these explosions result in secondary disasters, severe pollution, and mass mortality [5]. Therefore, much research has been done on the mechanism and causes of explosion of gas/dust mixtures to improve safety.

Current studies mainly focus on explosion parameters [[6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16]], flammability limits [[17], [18], [19]], ignition properties [20,21], combustion behaviors [[22], [23], [24]], burning velocity [[25], [26], [27]], and experimental flame behaviors [[28], [29], [30], [31], [32], [33], [34], [35]] of methane/coal mixtures on the basis of imposed restrictions and budget expenditures. Quantitative studies have also been done on external and internal conditions of methane/coal explosions, such as initial pressure [36], solid additives [[37], [38], [39]], ignition source [16,40], obstacle/water mist [[41], [42], [43], [44], [45], [46]], equivalence ratio [13], oxygen level [47], and initial turbulence [40,48] Their findings indicate that both external and internal conditions strongly affect the explosive properties of a gas/dust mixture.

However, none of the above studies has involved the temperature evolution of particles during deflagration. In fact, the coal dust cloud experiences intricate heat-mass transfer accompanied by transient chemical reactions throughout the hybrid explosion. Meanwhile, some research has concluded that the particle morphology is directly affected by thermal accumulation among particles [[49], [50], [51], [52], [53]]. Coal is a kind of brittle organic matter whose particle morphology is easily affected by flame temperature and thermal shock. Studying the formation mechanism of various types of solid residues in homogeneous–heterogeneous combustion of coal would provide valuable information on dust-involved explosions [54,55]. Thus, insights into the temperature development of a coal dust cloud would help in understanding its explosion [[56], [57], [58]].

Only a few recent attempts have been made to reveal the temperature effects on an exploding particle cloud. Different techniques have been proposed [[59], [60], [61]] and various measurements conducted [[62], [63], [64], [65], [66]] to capture the temperature development and distribution of particles during heat-mass transfer [[67], [68], [69], [70]]. For instance, Choi et al. [71] investigated the effect of microgravity on formation and motion of soot particles using a diffusion flame at three different temperatures. Their results showed a nonlinear relationship between the volume fraction and wall temperature. Majid et al. established a model for the particle–wall interaction and used the Euler-Lagrangian approach to analyze the effect of the wall on the particle trajectory and particle surface [72]. Golovin et al. used the Shvab-Zel'dovich method, which considers particle heat diffusion, to conclude that both particle forces and viscosity affect heat and mass transfer insignificantly [73]. Bu et al. studied the ignition behavior of a single coal particle under O2/N2 and O2/CO2 atmospheres using a volatile flame. They found that the ignition delay under an O2/CO2 atmosphere was longer than that in an O2/N2 atmosphere [74]. Si et al. [75] experimented with the combustion behaviors of individual coal particles. Their results showed that three single coal particles undergo particle heating, volatile release and combustion, and volatile and char oxidation during combustion. Wu et al. [76] characterized the holographic fringes of burning coal particles using concentric rings. They reported some typical modes of a volatile flame and found that the burning of one coal particle was affected by another particle.

Owing to the limits of experimental tests, numerical modeling provides a convenient, efficient, and swift method for predicting the temperature variation of an exploding particle cloud. Moissette and Boulet used a commercial computational fluid dynamics (CFD) code and advanced numerical methods to establish a dispersion model to predict particle behavior and temperature via the Lagrangian approach [77]. Manovic et al. analyzed the temperatures of a coal char particle in a hot bubbling fluidized bed considering heat and mass transfer, heterogeneous reaction, and homogeneous reaction [78]. Fattahi et al. studied gas–particle heat transfer for fluidized and spouting regimes using an Eulerian-Eulerian two-fluid model, finding that specularity coefficients greatly affect particle behavior [79]. Gerhardter et al. calculated the convective in-flight heating of non-spherical particles using the Euler-Lagrangian approach [80]. Luo et al. found that high temperature thickens the boundary layer and strengthens turbulence in the motion of charged particles [81]. Chen et al. revealed the relationship between flame velocity and particle behavior, concluding that the overall dust cloud expansion velocity falls behind the flame velocity [82]. Moreover, the CFD discrete element method (CFD-DEM) was used to calculate the configurational temperature [83], particle heat conduction [[83], [84], [85]], flow behavior [86,87], mass-heat transfer [88], and particle temperature distribution [89,90] during particle ignition.

Heat-mass transfer among particles is not well understood owing to the scarcity of studies on temperature variation of a particle cloud during a gas/dust hybrid explosion. This makes it difficult to determine particle cloud temperature accurately. Numerical methods and CFD software on particle flow reactions make it possible to accurately calculate temperature variations during deflagration [37,56,57,82].

Therefore, we implemented a three-dimensional numerical model using the commercial code FLUENT to study the temperature evolution and other particle cloud phenomena to obtain information on heat-mass transfer and coupling interactions in gas/dust hybrid explosions.

Section snippets

Mathematical models

Hybrid explosions can be modeled on the basis of mass and energy conservation and chemical reaction balance [56,57].

Temperature development and combustion behaviors of coal dust cloud

Fig. 5 presents the temperature development for discrete particles during the hybrid explosion at different moments. The maximal temperature of the coal dust cloud fluctuates peculiarly throughout the explosion process owing to gas–particle interaction, heat absorption by gaseous products, and heat conduction by the gaseous flame. The particle cloud dispersion is irregular and the particle temperature distribution uneven owing to turbulent flow, particle collision, gas–particle interaction,

Conclusions

We used a three-dimensional model to investigate the transient evolution of particle temperature for an explosion of a methane/coal dust mixture with a certain concentration. The maximal temperature of the coal dust cloud fluctuated throughout the explosion owing to the gas–particle interaction, heat absorption by gaseous products, and heat conduction by the gaseous flame. The dispersion of the particle cloud was irregular and its particle temperature distribution uneven owing to turbulent

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This work was supported by the National Key R&D Program of China (Grant no. 2018-YFC-0807-900, 2016-YFC-0800-100), the General Program of National Natural Science Foundation (Grant no. 5167-4191, 5197-4236), the Cultivation Fund for Excellent Doctoral Dissertation of the XUST, the Program of CSC (Grant no. 2018-0861-0249) funded by the China Scholarship Council, and the Key R&D Program of Shaanxi Province (Grant no. 2017-DCXL-GY-010203). Besides, the first author thanks a lot to Zhiqian Xue,

First page preview

First page preview
Click to open first page preview

References (97)

  • S.X. Song et al.

    Hybrid CH4/coal dust explosions in a 20-L spherical vessel

    Process. Saf. Environ. Prot.

    (2019)
  • D. Torrado et al.

    Influence of carbon black nanoparticles on the front flame velocity of methane/air explosions

    J. Loss Prev. Process Ind.

    (2017)
  • B. Janovsky et al.

    Coal dust, Lycopodium and niacin used in hybrid mixtures with methane and hydrogen in 1 m3 and 20 L chambers

    J. Loss Prev. Process Ind.

    (2019)
  • P. Zhao et al.

    Minimum explosion concentration of coal dusts in air with small amount of CH4/H2/CO under 10-kJ ignition energy conditions

    Fuel

    (2020)
  • C.T. Cloney et al.

    Laminar combustion regimes for hybrid mixtures of coal dust with methane gas below the gas lower flammability limit

    Combust. Flame

    (2018)
  • C.T. Cloney et al.

    Role of particle diameter in the lower flammability limits of hybrid mixtures containing coal dust and methane gas

    J. Loss Prev. Process Ind.

    (2019)
  • Z. Abbas et al.

    Theoretical evaluation of lower explosion limit of hybrid mixtures

    J. Loss Prev. Process Ind.

    (2019)
  • E.K. Addai et al.

    Models to estimate the minimum ignition temperature of dusts and hybrid mixtures

    J. Hazard. Mater.

    (2016)
  • E.K. Addai et al.

    Experimental investigation on the minimum ignition temperature of hybrid mixtures of dusts and gases or solvents

    J. Hazard. Mater.

    (2016)
  • K. Onda et al.

    Spectral emission from MHD combustion gas mixed with pulverized coal

    J. Quant. Spectrosc. Radiat. Transf.

    (1985)
  • R. Sanchirico et al.

    On the explosion and flammability behavior of mixtures of combustible dusts

    Process. Saf. Environ. Prot.

    (2015)
  • D. Bradley et al.

    Lean flammability limits and laminar burning velocities of CH4-air-graphite mixtures and fine coal dusts

    Combust. Flame

    (1989)
  • N. Cuervo et al.

    Determination of the burning velocity of gas/dust hybrid mixtures

    Process. Saf. Environ. Prot.

    (2017)
  • S. Ranganathan et al.

    Turbulent burning velocity of methane-air-dust premixed flames

    Combust. Flame

    (2018)
  • C.H. Bai et al.

    The explosion overpressure field and flame propagation of methane/air and methane/coal dust/air mixtures

    Saf. Sci.

    (2011)
  • S.R. Rockwell et al.

    Influence of coal dust on premixed turbulent methane–air flames

    Combust. Flame

    (2013)
  • Y.X. Xie et al.

    Study of interaction of entrained coal dust particles in lean methane–air premixed flames

    Combust. Flame

    (2012)
  • Y. Liu et al.

    Flame propagation in hybrid mixture of coal dust and methane

    J. Loss Prev. Process Ind.

    (2007)
  • M.J. Ajrash et al.

    The flame deflagration of hybrid methane coal dusts in a large-scale detonation tube

    Fuel

    (2017)
  • Y. Li et al.

    Experimental study on the influence of initial pressure on explosion of methane-coal dust mixtures

    Procedia Eng.

    (2013)
  • Y.F. Song et al.

    Explosion energy of methane/deposited coal dust and inert effects of rock dust

    Fuel

    (2018)
  • Q.M. Liu et al.

    Methane/coal dust/air explosions and their suppression by solid particle suppressing agents in a large-scale experimental tube

    J. Loss Prev. Process Ind.

    (2013)
  • J.R. Taveau et al.

    Igniter-induced hybrids in the 20-l sphere

    J. Loss Prev. Process Ind.

    (2017)
  • C.J. Dong et al.

    Effects of obstacles and deposited coal dust on characteristics of premixed methane-air explosions in a long closed pipe

    Saf. Sci.

    (2012)
  • H.L. Xu et al.

    Experimental study on the mitigation via an ultra-fine water mist of methane/coal dust mixture explosions in the presence of obstacles

    J. Loss Prev. Process Ind.

    (2013)
  • Y.H. Zhou et al.

    Experimental research into effects of obstacle on methane-coal dust hybrid explosion

    J. Loss Prev. Process Ind.

    (2012)
  • H.L. Xu et al.

    Experimental investigation of methane/coal dust explosion under influence of obstacles and ultrafine water mist

    J. Loss Prev. Process Ind.

    (2017)
  • H. You et al.

    Study on suppression of the coal dust/methane/air mixture explosion in experimental tube by water mist

    Procedia Eng.

    (2011)
  • E.K. Addai et al.

    Experimental investigation of limiting oxygen concentration of hybrid mixtures

    J. Loss Prev. Process Ind.

    (2019)
  • M. Scheid et al.

    Experiments on the influence of pre-ignition turbulence on vented gas and dust explosions

    J. Loss Prev. Process Ind.

    (2006)
  • T. Kobayashi et al.

    Effects of heat-treatment temperature and starting composition on morphology of boron carbide particles synthesized by carbothermal reduction

    Ceram. Int.

    (2013)
  • T. Yousefi et al.

    Synthesis and characterization of cerium oxide nano-particles in chloride bath: effect of the H2O2 concentration and bath temperature onmorphology

    Mater. Sci. Semicond. Process.

    (2013)
  • J.G. Yu et al.

    Effects of PAA additive and temperature on morphology of calcium carbonate particles

    J. Solid State Chem.

    (2004)
  • S.G. Maas et al.

    The impact of spray drying outlet temperature on the particle morphology of mannitol

    Powder Technol.

    (2011)
  • J.F. Hochepied et al.

    Influence of precipitation conditions (pH and temperature) on the morphology and porosity of boehmite particles

    Powder Technol.

    (2002)
  • S. Lin et al.

    Comparison on the explosivity of coal dust and of its explosion solid residues to assess the severity of re-explosion

    Fuel

    (2019)
  • W.G. Cao et al.

    Experimental and numerical studies on the explosion severities of coal dust/air mixtures in a 20-L spherical vessel

    Powder Technol.

    (2017)
  • W.G. Cao et al.

    Experimental and numerical study on flame propagation behaviors in coal dust explosions

    Powder Technol.

    (2014)
  • Cited by (20)

    • Macromorphological features and formation mechanism of particulate residues from methane/air/coal dust gas–solid two-phase hybrid explosions: An approach for material evidence analysis in accident investigation

      2022, Fuel
      Citation Excerpt :

      In recent years, frequent occurrences of methane-coal dust hybrid mixture explosions have aroused substantial attention, wide public concern, and special interest from domestic and foreign scholars. Numerous investigations into methane/coal dust explosions have focused on the ignition properties [10,14–18], explosion mechanisms [19–22], explosion behaviors [5,23–27], flame propagation [24,28–31], influence factors [11,23,25,32,33–36], explosion suppression [25,37–42], explosion assessment [43], and explosion monitoring [44,45]. The aforementioned studies can not only greatly promote the precaution and prevention of gas and coal dust explosion accidents, but could also guide the assessment and diagnosis of coal-dust-involved explosions.

    View all citing articles on Scopus
    View full text