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88 / 2023-06-14 16:02:03
Kinetic and oxygen-transport limiting regimes of reverse propagation of smoldering coal fires
reverse propagation, kinetic limiting regimes, oxygen-transport limiting regimes, porous media, numerical simulation
2. Mine ventilation, fire, water damage prevention
Abstract Accepted
Hao Zhang / 西安科技大学
Zeyang Song / 西安科技大学
Coal fire is a global disaster that threatens coal mine safety production and pollutes the environment. Due to its concealment and difficulty in exploration, it has brought trouble to coal fire control. Coal fire combustion is mainly in the smoldering state, so the governance of coal fire is essential to block the spread of coal smoldering. As a way of smoldering, reverse smoldering is also the main factor inducing underground coal fire. Therefore, it is of great significance to explore the kinetic and oxygen-transport limiting regimes of reverse propagation for the prevention of smoldering coal fires of numerical simulation. In this work, we experimentally and numerically investigate the reverse propagation of smoldering coal fire with two different coal samples (bituminous coal CC and anthracite coal XA) and variable airflow conditions(8 L/min, 32 L/min, and 64 L/min). A numerical model integrated kinetic and oxygen-transport limiting regimes. with a five-step reaction scheme was constructed, which has great advantages compared with the traditional kinetic limiting model. In this model, in order to better restore the experimental process, the Reynolds number under each flow rate is calculated, and finally the Darcy 's law field is used to simulate the condition factors of forced convection. And it based on the oxygen component transport equation of gas-solid two-phase in porous media at particle scale, the oxygen component transport equation considering the smoldering kinetic reaction-oxygen supply control mechanism at fuel layer scale is derived. It simplifies the non-equilibrium equation of gas-solid two-phase oxygen concentration into the equilibrium equation of oxygen concentration. And the Damkohler (Da) number is introduced to quantify the restriction mechanism of reverse propagation. The model was validated by comparison of numerical simulation results with experimental observations. In addition, we also explored key factors: the characteristic length of oxygen concentration, heat transfer coefficient, convection coefficient, and gas viscosity coefficient. Through the study of the experimental part, we get that the peak temperature of the two coal samples increases with the increase of the flow rate, and the spreading rate increases with the increase of the flow rate. For this, we calculate the spreading rate under different flow rates. At flow rates of 8 L/min, 32 L/min, and 64 L/min, the spreading rates for CC and XA coal samples were 17.37 cm/h, 29.49 cm/h, and 40.45 cm/h and 13.10 cm/h, 18.39 cm/h, and 48.89 cm/h, respectively. In terms of numerical simulation, the characteristic length of oxygen concentration has a great influence on the whole spreading process. By adjusting the value, the oxygen transport can be controlled to indirectly change the speed of the spread rate. It is verified that the model can be well applied to the reverse spread process. In addition, oxygen-transport limiting regimes play a leading role in the whole smoldering process, and the effect of kinetic limiting regimes is not obvious. The problems discussed in this work and the conclusions drawn are helpful to reveal the microscopic process of smoldering coal fires and it has a certain reference value for suppressing smoldering coal fires.
Important Date

  • Conference Date

    Aug 18

    2023

    to

    Aug 20

    2023

  • Jul 07 2023

    Draft paper submission deadline

  • Aug 20 2023

    Registration deadline

Sponsored By
International Committee of Mine Safety Science and Engineering
Organized By
Heilongjiang University of Science and Technology
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