Delineation and Prevention of the Spontaneous Combustion Dangerous Area of Coal in a Regenerated Roof: A Case Study in the Zhoujing Coal Mine, China

Abstract

Spontaneous coal combustion in a regenerated roof is difficult to find, and the awareness of prevention is relatively weak. To effectively delineate the range of the danger area, the characteristic parameters of spontaneous coal combustion were tested. The result shows that carbon monoxide (CO) was chosen as the index gas, and the relationship between the oxygen consumption rate and oxygen concentration was fitted linearly. Mathematical models of the air speed field and oxygen concentration field were derived, and a physical model of the regenerated roof was established. On the basis of COMSOL Multiphysics simulation, the test value and predicted value of air speed and oxygen concentration were compared with good similarity. The danger area of spontaneous coal combustion was determined by the two indices of oxygen concentration and air speed with ranges of 1.35–6 and 0.60–3.02 m, respectively. A polyacrylamide–particle-stabilized foam (PPSF) with an average pore size of 165 μm and pore wall thickness of 30.5 μm was prepared in batch mode using a homemade foam-generating device. Optical microstructure characterization showed that the mixed powder can be distributed evenly in the liquid film and that polyacrylamide as a vesicular liquid membrane carrier presented a network structure. The formation mechanism of the foam was presented in a schematic diagram. The PPSF was injected into the delineated danger area of 350 m3, and the temperature and concentration of CO decreased to 32 and 29 °C and 5 and 22 ppm, respectively. All of these results indicated that PPSF can effectively inhibit spontaneous coal combustion in the regenerated roof.

Research on the Inhibitory Effect of Hydrated Phase Change Materials on Spontaneous Combustion in Coal

“…The four experimental coal samples, which had varying degrees of metamorphism, were treated with a hydrated phase change material containing 57. 6 ). The weight ratio of coal samples to the resistance material was 4:1.…”

“…The spontaneous combustion of coal can lead to huge economic losses [4]. Therefore, the mechanism underlying the spontaneous combustion of coal must be investigated in order to guarantee the safety of coal mine production [5,6]. According to the most widely accepted coal oxidation hypothesis by scholars, both domestically and internationally [7], the process through which coal's reaction groups react with oxygen to produce heat is known as spontaneous combustion.…”

Laboratorial Investigation of Coal Fire Extinguishing and Re-burning Risk in Underground Coal Mines

“… 1 − 4 Although the existing fire prevention and treatment techniques are multifarious, the control of underground coal fire remains extraordinarily challenging. 5 − 8 Generally, for underground mines with complex conditions and restricted fire-extinguishing approaches, the method of closure of the fire area is often used to control spontaneous fire hazards. 9 − 12 However, when re-opening the fire area to normalize coal recovery, re-burning accidents emerge as required, resulting in further casualties and property losses.…”

“…As a significant source of fossil fuel energy, the production of coal is often accompanied by frequent spontaneous fires, which poses a great threat to the safety of underground miners. − Although the existing fire prevention and treatment techniques are multifarious, the control of underground coal fire remains extraordinarily challenging. − Generally, for underground mines with complex conditions and restricted fire-extinguishing approaches, the method of closure of the fire area is often used to control spontaneous fire hazards. − However, when re-opening the fire area to normalize coal recovery, re-burning accidents emerge as required, resulting in further casualties and property losses. − Therefore, research on re-burning of fire areas has become a major issue to be addressed. After the fire area is closed progressively, the coal within is gradually extinguished due to insufficient O 2 supply, but the heat hardly dissipates and further accumulates, resulting in the long-term maintenance of a high-temperature regime. − During the enclosed period of the fire area in an underground coal mine, it is impossible to see the development of the fire, but it is necessary to investigate the state of the combustion in the fire area. − At present, as the common practice to understand indirectly the fire condition, we rely on gas indicators, as shown in Table .…”

Colloidal Particle-Stabilized Foam To Control the Coal Spontaneous Combustion: Stability Mechanism Analysis and Extinguishing Properties

“…In the world, coal still plays an important role in the energy system. Coal spontaneous combustion is one of the main natural disasters affecting the safety of coal production. − Coal spontaneous combustion not only has caused huge casualties and economic losses but also has seriously damaged the natural environment. − Many technologies have been put forward to prevent coal spontaneous combustion, including grouting, − nitrogen injection, − inhibitor, and gels. − However, with the increase of mining depth, the control effect of these prevention technologies on the more complex coal spontaneous combustion problem was gradually reduced . On the basis of traditional technologies, due to the advantages of low density, high coverage, and good seepage performance, foam technology has been used to inhibit the coal spontaneous combustion …”