Study On The Mechanism Of Coal Spontaneous Combustion Induced By Associated Pyrite Minerals In Yangquan Mining Area

The general rule is that anthracite is not easy to spontaneous combustion.However,in the mining process of high metamorphic anthracite seams in Yangquan mining area,the associated pyrite minerals in the coal are often encountered heterogeneously,which leads to spontaneous combustion and seriously threatens coal mine safety.The dissertation takes 4 typical coal from working faces in Yangquan mining area as the research object,and uses the research method of the combination of theoretical analysis and physical simulation experiment to study the effect of the inherent pyrite in the coal,the associated pyrite minerals and their oxidation products on the coal spontaneous combustion.The influence law reveals the mechanism of the spontaneous combustion of anthracite induced by associated pyrite minerals.The main research results are as follows:Experimental studies have concluded that the sulfur in coal and associated pyrite minerals are mainly iron sulfide sulfur,so the sulfur-bearing minerals in coal are pyrite with euhedral,banded,infested and agglomerated.There is a one-to-one correspondence between the Fe and S elements in the coal.The associated pyrite minerals are composed of pyrite,troilite and coquimbite.From the perspective of thermal decomposition of pyrite,the conversion temperature of pyrite in coal is lower than that of associated pyrite minerals.The physical flotation method is used to prepare coal samples with different contents of inner pyrite.According to the synchronous thermal analysis experiment,the risk of spontaneous combustion of coal increases with the increase of inner pyrite content.The associated pyrite minerals and their oxidation products(Fe₂(SO₄)₃,FeS,FeSO₄,and Fe(OH)₃)were added to coal,and it was found that the characteristic temperature of coal decreased,mass gain increased,heat release increased,and activation energy decreased.Among the oxidation products,Fe₂(SO₄)₃ and FeSO₄ reduce the ignition point of coal the most,which is 4.7?11.7?.FeSO₄ and FeS have the greatest impact on the initial release temperature of SO₂,about 100?.Fe(OH)₃ has the greatest impact on the activation energy of coal,which is reduced by 29.5%at most.Using a self-built temperature-programmed experimental system with a humidity generating device,it simulates the influence of inner pyrite content,associated pyrite minerals and their oxidation products on gas production and oxygen consumption in a high-humidity environment.It is found that the spontaneous combustion risk of coal in dry and humid environments increases with the increase of inner pyrite content.Compared with the dry environment,the oxygen consumption in the humid environment,the production of CO,CO₂,C₂H₄ and C₂H₆ increase,the initial temperature of CO decreases,and the activation energy decreases.The combined effect of water and associated pyrite minerals is stronger than the single effect of water or associated pyrite minerals.Combining the index gas generation law and activation energy,it is obtained that Fe₂(SO₄)₃ and FeS have the strongest promoting effects on coal spontaneous combustion in dry and humid environments,respectively.Through in-situ infrared experiments,the effects of inner pyrite,associated pyrite minerals and their oxidation products on the functional groups in coal are obtained.Combined with the chemical reaction theory,the mechanism of the spontaneous combustion of anthracite induced by the associated pyrite minerals is revealed:Fe is used as the free radical initiator,and the continuous cycle generation/consumption of free radicals and the Fe₃₊-Fe₂₊ redox is used as the key paths to promote the reaction to proceed continuously.The study on the mechanism of spontaneous combustion of high metamorphic anthracite induced by associated pyrite minerals is of great significance for the prediction of spontaneous combustion in other anthracite coal mines and the construction of a prevention and control technology system.The dissertation has 96 pictures,40 tables and 212 references.