Evaluation Of Key Influencing Factors Of Combustion And Explosion Characteristics Of Wheat Dust

With the development of China’s modern industry,industries involved in dust applications have frequent dust explosion accidents in the industrial process,and the frequent occurrence of dust explosion accidents also restricts the development of industrialization.Among these accidents,food dust explosion is a large dust type in the accident that causes dust explosion,and even more so wheat flour explosion.Therefore,in order to have a deeper understanding of the principle of dust explosion,reduce the severity of the consequences of explosion accidents,and clarify the key factors leading to the violent explosion of wheat flour,it is of great significance to control the explosion of wheat flour.In this paper,the combustion process of wheat flour was studied by using conical calorimeter and DW-02 ignition temperature measuring instrument,and different particle size dispersion degrees were determined for the graded wheat flour.At the same time,the lower explosive limit concentration of wheat flour was tested by 1.2L Hartmann,and the change law of explosion characteristic parameters was studied by20L spherical explosion tester.Finally,according to the improved grey correlation analysis method,the influence of particle size distribution on the minimum ignition temperature of wheat flour and the influence of different dust explosion factor variables on the maximum explosion pressure of wheat flour were evaluated.The main findings of this paper are as follows:（1）The combustion performance and mechanism of wheat flour were experimentally studied.Obtained from the heat release rate curve of wheat flour,the combustion of wheat flour can be divided into three processes:heating stage,combustion stage and extinguishing stage.Under the condition of fixed heat radiation flux,the smaller the particle size of wheat flour,the longer the ignition time,and the smaller the average heat release rate.However,when its particles are reduced to a certain extent,the ignition time of wheat flour will begin to increase,and the peak average heat release rate will increase accordingly.At the same time,according to the results of the test of the minimum ignition temperature of wheat flour of different particle sizes,the minimum ignition temperature of wheat flour showed a trend of first decreasing and then increasing with the decrease of particle size,and the lowest ignition temperature was 380°C when the median diameter was 22.38μm.（2）The explosive properties and mechanism of wheat flour were experimentally studied.The maximum explosion pressure of wheat flour increases first and then decreases with the increase of mass concentration and ignition delay time.When the dust mass concentration is set to 500g/s,the maximum explosion pressure reaches the maximum when the optimal ignition delay time is 60ms,which is 0.606MPa;in the test range,the smaller the particle size of wheat flour,the greater the maximum explosion pressure and pressure rise rate,when the particle size of wheat flour is less than a certain limit,its maximum explosion pressure is reduced,and when the particle size of wheat flour is within the range of 22.38μm,its explosion risk is the highest.（3）The combustion and explosion parameters of wheat flour were quantitatively evaluated.Based on the gray correlation analysis method,the combined weighting method was applied to calculate the weights,and the results showed that the comprehensive correlation between the grain size distribution of wheat flour and the minimum ignition temperature was as follows:(₉₀-₁₀)?₅₀>₉₀?₁₀>₁₀>₅₀>₉₀.The comprehensive correlation degree of different dust explosion factor variables on the maximum explosion pressure of wheat flour was as follows:dust particle size>dust mass concentration>ignition delay time.