| Coal is important in Chinese energy sector,but coal production and storage accidents it is often seen.The coal self-ignition problem is an important reason cause that accidents occur,especially for low rank coal represented by lignite.Lignite occupies a high proportion in the coal resources of our country,and has the characteristics of low ignition point,high spontaneous combustion tendency,difficult to excavation and utilization.Therefore,it is greatly significantly to study coal spontaneous combustion.Based on the model of F-K spontaneous combustion,and drawn on the principle of "basket method" cross temperature experiment,experiments of coal spontaneous combustion were tested Experimental coal samples were lignite selected from the Baiyinhua coal mine,Inner Mongolia of China,and the fresh coal was crushed into six different sizes.Oxidation and self-ignition of coal sample for different particle size and different pile size were studied.The temperature field,the seepage field and the gas concentration field were simulated by the finite volume method.The self-developed data process software was used to generate the related graphics,and the relation among characteristic indexes,time and particle size for coal spontaneous combustion process is analyzed.Coal combustion spontaneous experiments were repeating tests that coal samples with different particle size in three different size of cube baskets.The interior heating processes of different piling states were detected,and the heating process of interior coal can be divided to four stages,the initial heating stage,transitional heating stage,the temperature recovery stage,and the temperature abrupt(rapid rising occurs spontaneous combustion or gradual decline of temperature)stage.The phasic variation is independent of particle size.Discussed the influence of particle size on critical ignition temperature,cross point heating rate,apparent activation energy.The experimental system was upgraded,and the gas composition measure of coal oxidation in the open-ended constant-temperature experiment was realized.Variation regulation of CO,CO2 and CO/CO2 with the temperature in the heating process of coal pile makes the oxidation degree of coal in different stages clearly.Based on experimental and numerical simulation.The temporal and spatial coupling relationship of each influencing factor during the spontaneous combustion process for coal pile was expanding researched,which can provide an effective theoretical reference for engineering practice. |
