Experimental Study On Dust Explosion Characteristics In Wood Products Processing

Dust explosion is a kind of explosion phenomenon which occurs when combustible dust and combustion-supporting gas meet the energy provided by a fire source in a relatively closed environment.It will not only cause a large number of casualties,property losses,but also cause environmental pollution.According to the global statistics,the combustion and explosion accident caused by wood dust is only less than the grain explosion.Therefore,it is very important to study the explosion characteristics of wood dust,which is of great significance to control,prevent or reduce occurrence of wood dust explosion accidents.Based on consulting a large number of documents,the main line is research on the characteristics of wood dust explosion.The research status of wood dust combustion and explosion characteristics at home and abroad are reviewed,meanwhile the existing problems are analyzed.On the basis,the cone calorimeter,1.2L Hartmann tube and dust ignition temperature test device are used to study combustion and explosion characteristics of wood dust.The main conclusions are as follows:?1?The combustion characteristics of wood dust have been studied.The combustion process of wood dust can be divided into 5 stages:heating,ignition,transition,acceleration and extinction.The ignition time and heat release rate of different particle size of wood dust are different.The smaller dust particle size is,the longer ignition time is.Meanwhile,the average heat release rate will decrease with the decrease of wood dust particle size.If mass ratio of mixed particle size is different,the combustion performance parameters of wood dust are also different.With the increase of mixing proportion of different particle sizes,the ignition time of wood dust is earlier,and the time required to reach the peak heat release rate is shorter.The combustion performance index and combustion growth index were introduced to evaluate the combustion risk of 3 single particle sizes and 3 different particle sizes mixed by 1:1 and1:2 of mass ratio respectively.The combustion risk of wood dust is the lowest when the mass ratio of d₅₀=235.90 and d₅₀=166.42?m is 1:1,and the combustion risk of wood dust with d₅₀=235.90?m is the highest.?2?The explosion sensitivity of wood dust is studied.By studying the minimum ignition temperature of wood dust layer,the minimum ignition temperature of wood dust cloud and the lower limit of wood dust explosion can obtain the effect law of particle size,mass concentration,spray pressure and bulking thickness on the sensitivity of wood dust explosion.The minimum ignition temperature and the lower limit of the wood dust decrease with the decrease of the particle size.With the increase of dust cloud mass concentration,the minimum ignition temperature of the dust cloud first decreases and then increases.The minimum ignition temperature of dust clouds and lower limit decreases and then increases with the increase of spray pressure.The minimum ignition temperature of wood dust cloud is higher 120?than of wood dust layer.?3?The explosion strength of wood dust is studied.By studying the effect of particle size,mass concentration and ignition delay time on the maximum explosion pressure,it is concluded that the maximum explosion pressure of wood dust decreases with the increase of wood particle size,increases with the increase of ignition delay time,first increases and then decreases with the increase of mass concentration.By using the Box-Behnken in Design-Expert software,the response surface analysis of the designed scheme is carried out,and the order of the factors affecting the size of maximum explosion pressure is:ignition delay time>mass concentration>particle size.