Study On Ignition Temperature Of Coal/Coal Char Based On Semenov Theory

Thermal power accounts for more than 83% of China's electricity production,of which nearly 90% of coal-fired power generation,and will continue in the future for a long time..The study of coal ignition is of great significance to prevent the spontaneous combustion of coal and improve the combustion characteristics of pulverized coal.In this paper,the research status of coal ignition is summarized,the ignition mechanism of coal is expounded,and the ignition criterion of coal is analyzed.The ignition temperature of coal and coal char is studied based on Semenov ignition theory.First of all,three kinds of coal samples were tested by TG-DSC,and the heating rate of each coal sample was increased from 2K/min to 50K/min.Based on the Semenov ignition theory,the DSC curves of pulverized coal combustion are analyzed,and the two critical ignition temperatures on the DSC curves of pulverized coal combustion are defined,the minimum critical ignition temperature and the maximum critical ignition temperature respectively.It is considered that the ignition temperature of pulverized coal begins to ignite at the minimum critical ignition temperature,the ignition is complete at the maximum critical ignition temperature.The ignition temperature of pulverized coal was solved by DSC critical ignition temperature method and TG-DTG method respectively,The results show that the ignition temperature of TG-DTG is between the minimum critical ignition temperature and the maximum critical ignition temperature;The higher the coal rank,the higher the ignition temperature;The higher heating rate,the ignition of the pulverized coal with higher temperature,and with the increasing of heating rate,the influence of heating rate on the ignition temperature is more and more small,and that after a certain heating rate,the ignition temperature of pulverized coal will be a fixed value,that heating rate of pulverized coal is ignition critical heating rate.Secondly,the heating of coal char particles was studied,and through the Semenov theory to establish coal heating ignition model,the ignition temperature and ignition delay time of two kinds of coal char particles in different environmental temperature were simulated and predicted.In this model,the self oxidation heat of coal char and the convective heat transfer on the surface of char particles is considered.The specific heat of coal char particles and the specific heat of air required for combustion are taken into account.The predicted ignition temperature is compared with the TG-DTG method,and the error is less than 3%.The simulation results show that the ignition temperature of coal char particles is not related to the ambient temperature in the simulated ambient temperature range,but the ignition time is related to the ambient temperature of the furnace,the higher the ambient temperature,the shorter the time.