| Highly gassy and spontaneous combustion goaf is the key associated area under the condition of compound disaster,the oxygen field,gas field and air leakage flow field meet each other in the goaf,and goaf residual coal is in a heterogeneous and differential oxidation environment.Although many researchers have been carried out in the field of high gas spontaneous combustion,the systematic research was not developed on the oxidation characteristics of residual coal in goaf gas atmosphere.In this paper,macro and micro study,theoretical analysis and laboratory experiments are used to design experiment scheme and reappear residual coal oxidation characteristics under gas containing oxidation atmosphere,through flow field characteristics of goaf are obtained by similar simulation experiments.The research results can provide theoretical basis for the prevention and control of compound disasters.In order to obtain distribution rules of goaf with high gas and spontaneous combustion,and master the environmental characteristics of residual coal oxidation in Goaf,combining with highly gassy and spontaneous combustion prototype goaf,3D heterogeneous simulation experimental platform of fully mechanized mining goaf was constructed,and the multi field characteristics are obtained by simulation experiment.Result shows that the air leakage boundary of goaf moves upwards,and the distribution of gas field and pressure field is asymmetrical with the increase of ventilation negative pressure.The gas enrichment area moves to working face and air return side with the ventilation negative pressure increasing.Combining the theory of fuzzy function and the characteristics of goaf three zones of spontaneous combustion,the hazard zone of compound hazard is studied,and show that it's border is controlled by gas enrichment area.Based on the actual oxidation atmosphere of the coal in the goaf,the residual oxidation characterization experimental scheme of macro and micro in the gas atmosphere was designed,so as to reduce the oxidation characteristics of the residual coal in the goaf as much as possible.The heat flow and the enthalpy of the stages are analyzed by studying the kinetic characteristics of the oxidation of coal in the gas atmosphere.In the non spontaneous combustion zone,sufficient oxygen is supplied to the residual coal,and the main factor affecting the oxidation process is the gas in the oxidation atmosphere,and it is in the low gas concentration section.In the possible spontaneous combustion zone,due to gas dilution effect and oxidation oxygen consumption of residual coal,the oxidation of residual coal is controlled by moderate oxygen and gas at the same time.The gas concentration in the spontaneous combustion zone increases along the side of the inlet air side.In the suffocation zone,residual coal oxidation causes absolute oxygen consumption in low oxygen concentration,coal is not fully oxidized,the dominant factor is the oxygen poor influenced by residual coal oxidation,due to asphyxia belt in the air leakage flow field,high gas concentration.The experimental results show that the dominant factors influencing the oxidation of the residual coal are mainly at the oxidation section after 130?,The heat flow rate and the heat flux increase rapidly in the high oxygen nitrogen ratio and low gas concentration oxidation atmosphere.The oxygen consumption and gas production law of coal samples under low temperature oxidation in gas atmosphere were analyzed.The results show that the oxygen consumption rate and CO concentration increase continuously with the increase of oxidation temperature,and increase slowly before 190?.The inhibition effect of gas and lean oxygen on the oxidation process of residual coal was revealed,and with the increase of gas concentration,the initial detection temperature of CO increases,and the initial detection concentration decreases under the condition of high oxygen nitrogen ratio.Under the condition of low oxygen nitrogen ratio,it is mainly affected by poor oxygen,and it also appears that the initial detection temperature of CO increases and the initial detection concentration decreases.From the point of view of the critical temperature change,the critical temperature of oxygen and nitrogen increases with the increase of gas concentration under the 0.27 oxygen-nitrogen ratio,which indicates that the gas is the dominant factor in the oxidation atmosphere,which inhibits the oxidation process of coal sample.When the oxygen-nitrogen ratio is 0.17,the critical temperature increases slowly with the increase of gas concentration.When the gas concentration reaches 17%,the critical temperature is no longer rising,indicating that the oxidation of coal samples is inhibited under the combined action of moderate oxygen and gas.When the oxygen-nitrogen ratio is 0.07%,the critical temperature is almost constant with the increase of gas concentration,which shows that the oxygen deficiency is the dominant factor to inhibit the oxidation of coal under the condition of low oxygen-nitrogen ratio,and the inhibition of gas in the oxidation atmosphere is weakened.Analysis of surface microstructure characteristics of coal samples by infrared spectroscopy showed that surface structure of coal was changed under different oxidation conditions,which focused on the main node temperature consistent with the macro characterization.At the initial oxidation temperature of 70?,the macroscopic differentiation point 130?,and the initial temperature of rapid oxidation of 190?,Characteristic peak transmittance decrease and microstructure development are observed.At low temperature,the gas atmosphere has a weak influence on the surface structure due to the low degree of oxidation of coal samples.After 70 ?,with the increase of gas concentration,the light transmittance of the oxygen-containing functional group shows an upward trend as a whole,and the inhibiting effect is compatible with the output characteristics of CO.After 130 ?,the oxidation rate gradually accelerated,the macroscopic characterization began to differentiate,and the influence of gas atmosphere on the micro chemical structure of coal samples showed segmentation characteristics,showing inhibition and induction effects respectively.At different oxidation temperatures,the influence of the specific oxidation atmosphere on the oxidation of coal samples shows a piece wise difference,which correspond coal sample oxidation process main node.At 40 ?,with the increase of gas concentration,the transmittance of characteristic peaks of all functional groups showed a decreasing trend,and the gas concentration at the turning point was 17%,indicating that all the functional groups had an inductive effect under high gas concentration.At 70?,with the increase of gas concentration,the hydroxyl group showed an inductive effect between 0%-17% and 17%-23%,which showed inhibitory effect,and had obvious inhibitory effect on oxygen-containing functional groups and aromatic hydrocarbons.When the gas concentration is from 0% to 5%,at 130?,the gas has an inductive effect on all functional groups except oxygen-containing functional group.The effect on the oxygen-containing functional groups is suppressed before the gas concentration is 17%,and then the induction effect is characterized.At 190?,the gas concentration increases,and the inhibitory effect on the oxygen-containing functional groups has an inductive effect on aromatic hydrocarbons.At 220 ?,the hydroxyl group has a significant inhibitory effect before 11% gas concentration,and then is a weak inductive effect.The oxygen functional group and aromatic hydrocarbon are induced before the gas concentration is 11%,and then the inhibition effect is followed. |
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