Study On The Effect Of Water Leaching Of Lingquan Lignite On Spontaneous Combustion Characteristics

The Lingquan mine is a century-old mine in China,and the coal seams are very close together and belong to thick seam mines.When mining,the fissures are affected by the mining movement,which will develop into water seepage channels and make the coal soaked for a long time.This changes the physical and chemical properties of the waterlogged air-dried coal samples,and increases the amount of air leakage during the process of water exploration and water release,making it easier for the phenomenon of"water-gas replacement"to occur,thus increasing the risk of spontaneous coal combustion.If we can’t accurately know the theoretical knowledge of spontaneous combustion of waterlogged relict coal and reduce the natural danger of waterlogged air-dried relict coal in the mining area,it will seriously endanger the mineral resources.In this thesis,the effect of water immersion on the oxidative spontaneous combustion characteristics of lignite is explained in terms of the physicochemical structure of coal using theoretical analysis,laboratory experiments and numerical simulations,and the combustion effect of water-immersion coal fraction under the action of fine water mist is simulated according to the findings of the study,taking Lingquan mine lignite as the research object.Using scanning electron microscopy experiment,pore adsorption experiment,Fourier infrared spectroscopy experiment,simultaneous thermal analysis experiment and programmed warming experiment to study,the results show that:water immersion will make the minerals attached on the surface or in the pores of coal easily soluble in water,which will expose more fissures and primary pores,making the surface structure uneven and prompting the interconnection between pores.When water immersion is less than 30 days,the pore size distribution of coal does not change much and the content of functional groups does not change significantly;when water immersion is 30-60 days,water immersion reduces the number of micropores and a small amount of water-soluble minerals are precipitated,which enhances the connectivity between pores and increases the content and proportion of oxygen-containing functional groups of coal;when water immersion is 60 days,water immersion continues to reduce the number of micropores and not only increases the number of mesopores and macropores above 40 nm It also increases the percentage of phenolic hydroxyl ether bonds and the content of self-conjugated hydroxyl groups formed by water molecules and the benzene ring macromolecular structure of coal,but decreases the content of oxygen-containing functional groups.Water immersion will reduce the initial exothermic temperature and ignition point temperature of coal,and will also accelerate the reaction process of exothermic and oxidative heating stages of coal under constant pressure conditions,while the exothermic heat of water-immersed coal in the low-temperature oxidation stage was measured to be higher than that of raw coal,but the activation energy of ignition was lower than that of raw coal.It was found by the programmed temperature rise experiment that C₂H₄gas appeared in both the raw coal and the water-immersed coal at 90°C.In the range of 0～100°C,the oxygen consumption and the oxygen consumption rate of both 30-day and 60-day immersed coal were higher than those of the raw coal and other immersed time coal samples.In the range of 125～135℃,C₃H₈gas is generated from the raw coal,and the gas generation temperature of the raw and dipping coal is advanced with the increase of the immersion time.The CO,CO₂and all kinds of alkane gas generation of the three water-immersed lignites are higher than that of the raw coal,but the crossover point temperature is lower than that of the raw coal,resulting in a tendency of higher spontaneous combustion with the increase of the immersion time.Through the numerical simulation of water-soaked 30 days of L105 pulverized coal combustion,the study shows that:in the initial moment,the flame in the role of fine water mist from the ignition position to the surrounding slow development of the flame front shape is non-spherical,with the development of the explosion to the disappearance of the flame surface of the whole process takes a total of 0.405 seconds,the explosion at the coal powder to get fully burned,the more volatile coal layer,with the promotion of the fire covering,the front of the water mist get congregated,so that the more water-soaked destroy coal remnants,not fully burned.There are 42 figures,6 tables and 82 references in the thesis.