Experimental Study On Ignition And Explosion Characteristics Of Wood Dust In Dust Removal Pipeline

In recent years,the dust removal system has become more and more widely used,but due to insufficient understanding of the dust explosion of flammable dust removal systems,dust explosion accidents caused by dust removal pipes in wood processing,food storage and other industries have occurred frequently,resulting in a lot of human resources.loss.The fluid movement in the dust removal pipeline is complicated,and it is difficult to study the mechanism of explosion occurrence.Therefore,the analysis of the dust explosion process of the dust removal pipeline is especially important for the explosion-proof design guidance of the dust removal system.Based on the above problems,this article uses thermogravimeter,dust ignition test device,cone calorimeter,1.2L Hartman tube explosion test device and self-built ventilation dust removal pipe dust explosion test device,taking cedar powder as an example to study The pyrolysis,ignition and explosion characteristics of the dust are as follows:?1?Analyze the pyrolysis process of cedar wood powder with thermogravimetric analyzer and cone calorimeter.The results show that the combustion process of cypress wood powder includes wood dust drying stage,transition stage,pyrolysis stage,and burnout stage.According to the thermogravimetric curve,the pyrolysis rate of cypress wood powder is directly proportional to the heating rate.When conducting experiments with a cone calorimeter,the higher the heat radiation flux,the lower the ignition time,and the higher the average heat release rate and peak heat release rate.Under the same radiation intensity,the smaller the particle size of cedar powder is,the easier it is to ignite,which is in line with the Arrhenius reaction process.?2?Analyze the igniting law of cypress wood powder using dust ignition temperature test equipment.The results show that the minimum ignition temperature range of the dust layer is 248??328?,and the minimum ignition temperature range of the dust cloud is 442??465?.The thicker the dust is,the easier it is to accumulate energy and be ignited.If there are two kinds of cedar wood powder in the pipeline,the smaller particle size of the cypress wood dust layer will be more in contact with oxygen and more likely to catch fire.?3?The 1.2L Hartman tube was used to study the explosion characteristics of cedar powder in the pipeline.The results show that:the lower limit of cypress dust explosion concentration is positively correlated with the particle size of the dust,the relationship with the ignition energy is not obvious,and the relationship between the spray pressure and the pressure decreases first and then increases.The maximum value of the pressure of cedar powder when the Hartman tube explodes shows a relationship of first rise and then decrease with the decrease of the particle size,a positive correlation with the ignition energy,and a trend of first increasing and then decreasing with the mass concentration of cedar powder;The order of influence on the maximum value of explosion pressure is:particle size,ignition delay time,mass concentration.?4?The self-made ventilation and dust removal pipe dust explosion characteristic test device was used to simulate the negative pressure environment of the ventilation and dust removal pipe in actual production,and the explosion characteristics of the cypress powder in the negative pressure pipe were studied.The results show that the propagation process of the pressure wave in the pipeline can be divided into free propagation,tube wall reflection and one-dimensional propagation.The relationship between the distance of each pressure measuring point from the center of the heating wire and the maximum explosion pressure of each point conforms to the empirical formula P_max=0.00293e^0.0031x.The lower limit of wood powder explosion concentration decreases with decreasing particle size,and generally decreases with increasing ignition delay time.The maximum pressure peak of cypress powder in the ventilation and dust removal pipe is negatively correlated with the particle size and positively correlated with the ignition delay time;the maximum pressure peak increases with the increase of the mass concentration and becomes the law of first increase and then decrease;The influence of the peak value is in order of mass concentration,ignition delay time,and particle size.?5?The test results of the lower limit concentration of wood powder explosion in Hartmann pipes and ventilation and dust removal pipes are 30-40g/m³ and 60-70g/m³,respectively.Due to the volume of the test pipeline,the powder spraying pressure,and the different direction of the pipeline,the test range data of the wood dust explosion pressure of the ventilation and dust removal pipeline is lower than that of the Hartmann tube,but the impact of the ignition delay when the two pipelines explode is ranked second,and the treatment Wood powder should avoid excessive mechanical collision,friction or static electricity.