| In recent years, the spontaneous combustion phenomenon occurs at the upper goaf of close distance coal seams is increasingly prominent,especially in the Shendong mining the close distance coal seams with the better geological condition, the thicker coal seam coal and the mineabler coal seam. A longer large mined-out area was formed after the upper coal seam mining face towards. In addtion, the sealing of the reserved coal pillar between adjacent working surface is not good, it’s easy to make goaf together as one.The effect of stress and periodic weighting caused by lower coal seam roof, under the influence of crack caused by goaf unicom, up and down from the lower airflow into the upper goaf when mining the lower coal seam. After mining the upper coal, through the influence of bending subsidence zone form a larger cracks, the ground’s surface and the surface of the goaf air leakage through cracks upwards. On the upper goaf water drainage, coal after water immersion, the porosity of coal, make coal oxygen contact area increases, the goaf ShuFang water process, broke the goaf water vapour pressure in the balance, cause water displacement, goaf air leakage increase. By surface air leakage, fluctuation of coal goaf unicom, water after soaking gap rates become larger, the water displacement, the influence of such factors as the upper coal spontaneous combustion in goaf provides a good condition, make the risk of coal spontaneous combustion is greatly increased When mining the lower coal seam, The lower coal seam cracks occurs by stress and periodic weighting. Affected by crack causing fluctuation of goaf unicom, resulting in lower air flow into the upper goaf. After the upper coal seam mining, the influence of bending subsidence zone makes the surface form a larger cracks. At the same time, air leakage occurs through cracks up goaf at the surface. On the upper goaf water drainage, coal after water immersion, the porosity of coal, make coal oxygen contact area increases, the goaf ShuFang water process, broke the goaf water vapour pressure in the balance, cause water displacement, goaf air leakage increase. By surface air leakage, fluctuation of coal goaf unicom, water after soaking gap rates become larger, the water displacement, the influence of such factors as the upper coal spontaneous combustion in goaf provides a good condition, make the risk of coal spontaneous combustion is greatly increased. On the upper goaf water drainage, coal after water immersion, the porosity of coal, make coal oxygen contact area increases. During the water drainage at the goaf, it broke the goaf water vapour pressure in the balance, causing water displacement and goaf air leakage increasing. By the influence factors, such as surface air leakage, mined-out area up and down connected, coal soaking by water, water displacement, and a good condition for spontaneous combustion in goaf, make the risk of coal spontaneous combustion is greatly increased.The spontaneous combustion fire point at upper goaf have some characteristics:concealment, wider range of fire area, easy to secondary oxidation by the thermal storage heat and air leakage, which brought great difficulties for the upper goaf fire management. The research on the the comprehensive measures of governance on the upper goaf cose the upper goaf of coal seamt has the extremely significant significance.Close the upper goaf spontaneous combustion of coal seam, This paper is focused on coal spontaneous combustion characteristics the reasons and characteristics of close the upper goaf of coal seam and the combination of the ignition conditions of2-2coal mine goaf in Shendong, comprehensive test of coal samples were carried out. Through four kinds of influence factors of coal spontaneous combustion of he different particle size, heating, air flow rate, O2concentration, the correlation characteristics of coal spontaneous combustion in the low temperature oxidation were studied. The results shows tha tthe effect of four kinds of influence factors of coal spontaneous combustion is relatively obvious. The premise of using CO, C2H4and H2as a comprehensive judgment index was established. At different stages of coal spontaneous combustion and its development trend were forecasted.Fire extinguishing the technological characteristics of liquid nitrogen and fire extinguishing effect are analyzed, combined with the situation of air leakage in Bulianta mine12306goaf, a FLUENT soft ware was introduced. The concentrations of oxygen, before and after nitrogen injection were measured. By comparing ground hole of measured data, it shows that the oxygen concentration has higher consistency with simulated data. After nitrogen injection, the diffusion radius of nitrogen in goaf of nitrogen is90m. Single span range of nitrogen injection is absent, and the method of combined nitrogen injection for the upper goaf governance fire is a reasonable choice. The nitrogen injection parameters is optimized. First by isotopic radon detection method for fire damage, the landfill fissure vertical fire fighting measures is established by drilling liquid nitrogen injection, grouting on the ground, underground to lower goaf nitrogen injection, leak air leakage points, and local sealing face. A good effect has obtained by by comprehensive extinguishing technology governance at close the upper goaf of coal seam. |
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