| In recent years,with the wide application of coal storage silos,the problem of insufficient inerting protection of cylindrical coal storage silos has become increasingly prominent.Due to the nature of coal itself,low-temperature oxidation reaction will occur in the process of coal storage,and the temperature will rise continuously.In addition,the structure of coal storage silo is closed,and the heat is not easy to lose,which is more likely to lead to spontaneous combustion of coal in the process of storage,which brings huge potential safety hazard to coal-fired power plants.The key to solve the problem is to study the internal temperature distribution of coal storage silos,timely and accurate temperature monitoring and inerting protection of coal storage silos.At present,the study on the temperature distribution of coal body in coal storage silo has not fully considered the influence of gas convection,nor fully considered the influence of jet air diffusion on the inerting protection effect in the process of inerting protection.Therefore,this paper adopts the method of combining experimental research and numerical simulation,The gas diffusion law,temperature distribution law and inerting protection method in coal storage silo are studied.A gas diffusion test-bed is built to study the gas diffusion law in coal.Through the gas diffusion test,it is found that under the influence of the jet,the gas preferentially diffuses to the coal seam above the jet.In the area not affected by the jet,the gas concentration reaches the equilibrium value and then slowly deposits to the coal seam below.The temperature field of coal storage silo is modeled and simulated.According to the simulation results,the influence of different factors such as gas convection,heat source temperature and heat source location on the distribution of temperature field is analyzed,and the distribution law of temperature field of coal storage silo is obtained.The results of numerical simulation of temperature field show that under the influence of convection effect in silo,the high temperature area is distributed above or above the heat source point,which leads to the temperature measurement point of the wall surface of the silo nearest to the heat source point can not accurately monitor the temperature change of the heat source point in time;In order to test the accuracy of the simulation results,the temperature data obtained from the simulation are compared with the temperature sensor data on the side wall of the coal storage silo in the test,and the accuracy of the temperature monitoring scheme is tested,and the causes of the errors are analyzed,which provides the basis for further optimization of the temperature monitoring scheme.The comparison between numerical simulation and experiment shows that the error is within the acceptable range,and the pore distribution of coal,environmental temperature,volatile gas precipitation and water phase transformation will affect the accuracy of temperature measurement points.Combined with the gas diffusion law and temperature field distribution law in coal storage silo,the layout of inerting nozzle is optimized,and a set of low pressure carbon dioxide inerting protection device is designed.The inerting protection effect of the device is tested by numerical simulation.The numerical simulation results of inerting protection show that the system can cool down the coal storage silo quickly within the required time.If it is necessary to further inhibit the low-temperature oxidation reaction of coal,it is necessary to extend the inerting time or increase the flow rate of inert gas,so that the inert gas can reach the required concentration before the coal can be stored in the silo. |
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