Experiemental Study On The Hysteresis Effect And Coal Oxidation Characteristics In Natural Cooling Process

The progress of coal spontaneous combustion shows a obvious process of complex physics and chemistry.It is essential to make proper measures to prevent the progress of coal spontaneous combustion in time after coal self-igniting.The parameters in the cooling process for real-time monitoring of coal temperature and gas contentration etc were needed to be monitored.Therefore,it is very important to study the spontaneous combustion of coal in natural cooling process.In order to study the spontaneous combustion characteristic in natural cooling process,spontaneous combustion characteristic of different coal in different particle sizes and different cooling methods were studied with programmed temperature rise experiment,analysising the effect of particle size and cooling methods on the concentration of gaseous products during the process of cooling.According to the concentration of CO,the cooling processes were divided into different stages,and the dynamic analysis was carried out,at the same time,the heating process and cooling process were compared and analyzed.Results show that the natural cooling process of coal is an obvious nonlinear characteristic.During the cooling process,the larger the oxygen concentration,the smaller the particle size of coal sample,the higher the gas concentration,the lower the temperature of the C2H4 production;According to the concentration of CO,the different cooling processes were divided into different stages,and each stage of the cativation energy was calculated,the higher the metamorphic degree,the higher the activation energy;Under the situation of same carrier gas,it is the temperature that the heating process compared to the cooling produce the same gas concentration(CO,C2H4 and CO2 of 1/3 coking coal)indures a certain hysteresis;contrary to the CO2 concentration of lignite and anthracite;The oxygen consumption rate of cooling process of lignite and 1/3 coking coal is higher than that of heating process,the oxygen consumption rate of the heating process and the cooling process have two intersections in anthracite.Meanwhile,through the large-scale coal spontaneous combustion experiment,the law of high temperature point?gaseous concentration?spontaneous combustion characteristic and limit parameters of the heating process and the cooling process with no oxygen were analyzed and compared.Results show that the position of high temperature points of the heating process and the cooling process are not completely coincident;In order to eliminate the air leakage that could not be measured during the cooling process,the calculation methods of unit flow of oxygen consumption?CO?CO2 generation rate and maximum/minimun heat output are obtained,which are the same as the results of the programmed temperature rise experiment,the feasibility of the method is proved and comparability between the heating process and the cooling process is increased;During the heating process,when the temperature is at 50?,the lower oxygen concentration,the least coal thickness and the maximal air leak intensity reach the maximum value,it will not cause coal self-igniting when the coal thickness is less than 0.648m;During the cooling process,when the temperature is at 80?,the lower oxygen concentration,the least coal thickness and the maximal air leak intensity reach the maximum value,it will not cause coal self-igniting when the coal thickness is less than 0.384m.Therefore,the research of coal oxidation characteristics of natural cooling process in mine goaf and closed fire areas after measures,it is significance to guide the changes of coal temperature and gas concentration in the cooling process.