Prevention and Control of Spontaneous Combustion of Residual Coals in Acid‐Soaked Goaf in Gas Drainage Condition

Abstract

With the increase of mine mining intensity, the scope of goaf continues to expand, a large amount of coal remains in goaf, and the spontaneous combustion fire of coal is particularly serious. In addition, the spontaneous combustion of coal under the condition of gas mining is not clear. At once, spontaneous combustion can induce gas explosion, resulting in the waste of manpower and material resources, bringing hidden dangers to the mine safety production. In order to prevent and control the fire caused by spontaneous combustion of left coal under the condition of gas mining, in this paper by means of laboratory test, field measurement, and numerical simulation, the law of spontaneous combustion of residual coal under gas mining is studied. The index gas of coal spontaneous combustion was determined by temperature-programmed experimental device. Secondly, the distribution of the stope working face, goaf, and O2 is discussed. It is of great significance to study the spontaneous combustion rule of three belts in goaf under acid leaching condition and then to discuss the best position of injection idling opening and put forward targeted precontrol measures, which is of great significance to guarantee the safety of mine production. The results show that CO begins to appear when the temperature rises to 40 °C, and its concentration increases exponentially with the increase of coal temperature, which can reflect the degree of coal oxidation in goaf. Therefore, CO should be selected as the indicator gas in the working face. Under the influence of negative drainage pressure, the dangerous area will be enlarged. The optimal drainage volume of high drainage roadway is 90 m3/min, and the optimal air intake volume of working face is 1400 m3/min. The area 0–34 m away from the working face is scattered zone, 34–135 m away is spontaneous combustion zone, and 135 m away is asphyxiation zone. When the position of the idler is 50 m behind the working face, the reduction of the oxidation zone is the largest.

Study on Nitrogen Injection Fire Prevention and Extinguishing Technology in Spontaneous Combustion Gob Based on Gob-Side Entry Retaining

“…GERRC is regarded as the third technological revolution in longwall mining in China. − By breaking the pressure transmission of the roof through directional pre-splitting and roof cutting, automatic roadway formation and coal pillar-free mining are achieved, aided by the mine pressure. − This phenomenon changes gas migration, causing fresh air to leak continuously into the gob from the working face. − The increased likelihood of spontaneous combustion in residual coal − not only decreases the economic viability of coal mining but also poses significant threats to the safety of underground workers. − Many scholars have conducted extensive research in this area. Wang et al analyzed and calculated the expansion coefficient of collapsed gangue over time and space, and they examined the effect of roof movement on the flow field in a mining scenario where the gangue is retained in the entryway via a cutting method.…”

Disaster-Causing Mechanism of Hidden Disaster-Causing Factors of Major and Extraordinarily Serious Gas Explosion Accidents in Coal Mine Goafs

“…This structure not only provides air leakage channels but also provides a suitable space for gas accumulation [4][5][6][7]. Under the action of air flow in these air leakage channels, notable spontaneous combustion of residual coal in the goaf can occur [8][9][10]. Additionally, the gas desorbed from residual coal can migrate and become enriched in the goaf, forming "gas storage reservoirs" [11][12][13][14].…”

Study of the Air Leakage Mechanism and the Suitable Gas Drainage Volume with the Upper Tunnel

“…As the overlying strata are caving, the location of the effective drainage section of the upper tunnel also changes. By affecting the flow direction of the gob gas, the effective drainage section creates low-pressure sinks and impacts the gob flow field [19,20]. In consideration of air leakages, the location of the effective drainage section of the upper tunnel caused by the roof collapsing is also worthy of discussion.…”