Study On Spontaneous Combustion Characteristics Of Typical Accumulated Combustible Dust

European standard EN 1127 regards combustible dust spontaneous combustion as one of the important ignition sources of accidents.With the rapid development of economy,more and more industries are involved in the accumulation of combustible dust,and fire and explosion accidents caused by the accumulation of combustible dust are on the rise.The high temperature of spontaneous combustion can cause explosive environments to ignite and can also cause stuffiness or combustion which can lead to serious consequences.The study and effective control of dust spontaneous combustion in the stacking state is the key to prevent dust spontaneous combustion from causing fire and explosion.The research on accumulation combustible dust hazard classification,ignition characteristics and spontaneous combustion temperature measurement can provide relevant technical support and data reference for the establishment of accumulation dust safety risk identification and classification standard and prevention and control measures of spontaneous combustion fire and explosion.Firstly,the cases of accumulated dust spontaneous combustion at home and abroad are analyzed statistically.The results of this study show that the powder-related industries include agriculture and forestry industry,mining and metallurgy industry,textile industry,light industry and chemical industry.Oxidation reaction,decomposition reaction,adsorption reaction,polymerization reaction and reaction fermentation reaction can produce heat inside the accumulated dust.At the same time,we got the dust accumulation caused by spontaneous combustion smoldering,fire,explosion accident types and conditions.Secondly,the ignition and explosion characteristics and spontaneous combustion mechanism of accumulated combustible dust were analyzed.It is found that the triggering conditions of spontaneous ignition include the heat release rate of the spontaneous combustion material and the heat accumulation conditions of the system.The ignition mechanism of spontaneous combustion of accumulated dust is analyzed from the Angle of the nature,composition and form of combustible material,and the critical condition of spontaneous combustion of accumulated combustible dust is analyzed with the theory of thermal spontaneous combustion.Based on the measurement standard of spontaneous combustion temperature,typical combustible dusts such as lignite,wood powder,edible starch and aluminum powder were selected to carry out experimental research on spontaneous combustion characteristics in different stacking states.The apparatus simulates the natural ventilation condition and realizes the measurement of the spontaneous combustion temperature of accumulated dust with a given volume.The spontaneous combustion temperature of several typical combustible dust in different volume volume under cubic shape accumulation and three temperature characteristic curves of combustible dust occurring ignition,spontaneous heating and incombustible are obtained.The Arrhenius curve of the same kind of accumulated dust is drawn based on the F-K spontaneous combustion theory model.The results show that the larger the volume of accumulated dust,the lower the spontaneous combustion temperature.The larger the volume of accumulated dust at the same constant ambient temperature,the more unstable it is.The relation between the critical ambient temperature and the critical mass of accumulated dust,and the relation between the induction time and the accumulated volume were obtained.The relation between the induction time and the accumulated volume was extrapolated by interpolation method to calculate the time required for the spontaneous combustion of the stored sample under the temperature of the critical mass and the accumulated dust at non-measured points.Finally,comprehensive prevention and control measures are proposed from the aspects of bulk volume,ambient temperature,storage time,etc.This study can provide decision-making basis for the prediction and warning of spontaneous combustion in typical combustible dust accumulation state and emergency treatment,and provide identification basis for the investigation and determination of fire cause of dust spontaneous combustion accident,which can be used to guide the investigation of accident hidden danger and fire risk prevention and control of enterprises involved in powder explosion.