Numerical Simulation of the Dynamic Change Law of Spontaneous Combustion of Coal Gangue Mountains

Abstract

To further study the problem of spontaneous combustion of coal gangue mountains, a multifield coupled simulation model was established based on the mathematical models of temperature field, gas concentration field, and seepage velocity field. In addition, the dynamic development law of these three physical fields in the process of spontaneous combustion is numerically simulated, and the relationship between gas concentration and temperature is studied and verified by experiments. The results show that in the initial stage of the thermal storage and heating process of the coal gangue mountain, the overall heating rate is small. With the passage of stacking time, a high-temperature area will gradually form inside, and the high-temperature area is concentrated near the windward side first and then spread to the leeward side. The oxygen on the windward side keeps a high concentration all of the time and gradually attenuates after entering the interior, and the overall concentration decreases with the extension of stacking time. The distribution law of carbon monoxide concentration is opposite to that of oxygen concentration. The variation law of carbon dioxide concentration is the same as that of temperature, that is, the concentration near the windward side is the highest, and then, it shows a distribution trend of first concentration and then divergence. The vortex phenomenon formed on the leeward side of the mountain outside and the chimney effect inside will aggravate the gas convection inside the gangue mountain, which makes the reaction continue so that the temperature of the gangue mountain keeps rising until it spontaneously ignites. There is a correlation between temperature and gas concentration. Among them, the concentration of carbon monoxide and carbon dioxide can well reflect the temperature change inside the coal gangue mountain, and the effect of carbon dioxide is better in the high-temperature area. The research results provide a theoretical reference for the prevention and control measures of spontaneous combustion of coal gangue mountains and have certain guiding significance.

Study on the Temperature Field Change Characteristics of Coal Gangue Dumps under the Influence of Ambient Temperature in Heat Pipe Treatment

“…Based on increasing the heat transfer surface area, improving the structural stability of the HP and improving the space utilization, the plum-blossom-shaped layout was used in this test. The height of the HP above the ground is 2 m. Considering the high temperature on the south side of the study area and the low temperature on the north side, and the limited influence range of a single gravity heat pipe (about 2-3 m) [43], the HP experiment in the high-temperature area was arranged at a spacing of 4 m, and a short pipe was inserted into the middle of the long pipe to strengthen shallow heat transfer. The HP test in the medium-temperature zone was arranged at a spacing of 5 m, and the arrangement was consistent with that in the high-temperature zone.…”

“…There are three temperature high value points in which the location is the same. Because the south side of the coal gangue dump is a windward surface, oxygen can easily enter the coal gangue dump inside, and the coal gangue dump is near the perennial west wind and east wind, so the windward slope location in the south near the sides appears to be a high-temperature point of spontaneous combustion in the coal gangue dump [43][44][45].…”

Determination and analysis of macro-featured parameters based on kilogram-level coal spontaneous combustion experiment

“…Zhang et al (2021b) established a large coal spontaneous combustion experimental bench to test the oxidative heating properties of Huangling coal, revealing the spatial and temporal evolution characteristics of the temperature field. Li et al (2022) studied and experimentally verified the relationship between O 2 , CO and CO 2 concentrations and temperature based on a mathematical model of the temperature field. Zuo et al (2021) studied the temperature rise during the natural oxidation of coal using a selfbuilt experimental platform and analyzed the variation of oxygen consumption and exothermic intensity with coal temperature by varying different air volumes and found that the exothermic intensity increased exponentially with the increase of temperature.…”