Study On The Characteristics And Prevention Of Spontaneous Oxidative Combustion Of Coal Gangue

Coal gangue is a kind of waste rock that accompanies coal in the process of coal formation,and becomes a kind of industrial solid waste in the process of coal mining and coal washing.The output of coal gangue accounts for about 10%to 15%of the total coal output.My country is the country with the largest coal mining volume in the world.The current total accumulation of coal gangue has reached 6 billion tons,and it is increasing year by year,becoming the industrial solid with the largest emissions one of the waste.Shanxi is a province with large carbon production,and it is also a province with large coal gangue piles.The piled coal gangue not only occupies a lot of arable land,but also causes serious environmental pollution.Especially in some areas of Jincheng City,due to the high sulfur content in coal gangue,the spontaneous combustion phenomenon of coal gangue hills stacked for a long time is common,and a large amount of toxic and harmful gases such as CO,SO₂ and NO_x are generated.Disasters such as mountain collapse and landslide have begun to restrict the development of the coal industry.How to effectively prevent spontaneous combustion of coal gangue and comprehensively utilize coal gangue has become a research focus and focus.This paper selects four different coal gangue samples from Jincheng City,namely XKXXG,GPMGS,XKXG and JSMGS,as the research objects.First,industrial analysis and ash composition analysis are carried out to study their oxidation spontaneous combustion characteristics;secondly,for the XKXXG samples with the highest sulfur content,the inhibiting effect of Ca(OH)₂ and DBHA compound inhibitor on the spontaneous combustion characteristics of coal gangue was studied;finally,from the perspective of comprehensive utilization of coal gangue,select JSMGS coal gangue samples,fly ash,cement,etc.,through orthogonal Experiments,particle gradation of coal gangue aggregates and activation of cementitious materials are used to study their effects on the performance of oxygen barrier materials.During the research process,combined XRD,FTIR,SEM,ICP-OES,TG-DTG-DSC,in-situ DRIFTS,industrial analysis and particle size analysis,the structure and properties of the gangue samples were tested and analyzed,and the following conclusions were drawn:(1)The physical and chemical properties of XKXXG,GPMGS,XKXG and JSMGS were analyzed to determine the sulfur content,mineral composition and oxidation active functional group content of coal gangue;and thermogravimetric analysis was used to determine the thermogravimetric parameters and oxidation active substance content of coal gangue.The relationship between,that is,as the pyrite content and(FC_ad+V_ad)/A_ad increase,the smaller the characteristic temperature point of the coal gangue,the easier the oxidation reaction occurs,and the greater the heat release.The kinetic functions of different coal gangues at different stages in the oxidation process are optimized,and the activation energy of each stage of the gangue oxidation process is calculated based on the oxidation kinetics characteristics of the coal gangue.The results show that the larger pyrite content in the coal gangue and(FC_ad+V_ad)/A_ad,the smaller the activation energy of coal gangue in each stage.Through the systematic analysis of different coal gangue,it is revealed that the spontaneous combustion of coal gangue is the result of the dual mechanism of pyrite oxidation and free radical chain reaction.Comprehensive analysis suggests that the spontaneous combustion tendency of the four types of coal gangue is:XKXXG>GPMGS>XKXG>JSMGS.(2)Taking XKXXG with the strongest spontaneous combustion tendency as the research object,starting from the dual oxidation exothermic mechanism of coal gangue spontaneous combustion,a Ca(OH)₂-DBHA composite inhibitor with dual physical and chemical inhibitory effects was designed.The study found that the characteristic temperature point of coal gangue after Ca(OH)₂ inhibition increased,and with the increase of the amount of DBHA,the characteristic temperature point further increased,and the maximum weight loss rate gradually decreased.Microscopic studies have shown that Ca(OH)₂ can convert Fe S₂ with oxidative activity into inactive sulfate and inhibit the cyclic oxidation of pyrite.At the same time,the addition of Ca(OH)₂ and DBHA reduces the content of active functional groups and inhibits the oxidation of active functional groups.The kinetic study shows that the activation energy of the hindered coal gangue increases in each stage of the oxidation process.When the air flow is 50m L·min^-1 and the heating rate is 1?·min^-1,the O₂ consumption rate of XKXXG hindered by Ca(OH)₂ and DBHA decreases,and the generation concentration of CO and CO₂ follows reduce.(3)The oxidative and spontaneous combustion of coal gangue requires sufficient oxygen supply.From the perspective of oxygen isolation,oxygen barrier materials are prepared with coal gangue as aggregate,fly ash and cement as cementitious materials.Orthogonal design experiments are used to determine that the ratio of coal gangue:fly ash:cement in the oxygen barrier material is 3:1:2.Using the Fuller-Tabol theory,it is determined that when n=0.4(n is the AN.Tabol formula coefficient),the aggregate has a reasonable particle gradation.At this time,the aggregate density of different particle sizes is the largest,the void ratio is the smallest,and the compressive strength of the corresponding oxygen barrier material at 7 d and 28 d was the highest,5.99 MPa and 12.83 MPa,respectively.Using Na₂SO₄,Na₂Si O₃,Na₂CO₃,Na OH to activate the fly ash-cement cementitious material,it is found that Na₂SO₄ has the best activation effect.When the content of Na₂SO₄ is 5%,the fly ash-cement cementitious material7 d and 28 d The compressive strength is 30.13 MPa and 44.88 MPa.Through the investigation of the working performance of the oxygen barrier material prepared by the optimized aggregate gradation and stimulant under acidic conditions,alkaline conditions,standard conditions and air environment,it is found that the strength of the prepared oxygen barrier material can be meet the requirements of covering coal gangue hills in different environments.