| Flammable dust explosion is a common safety accident in many industries.Once the explosion occurs,it is easy to cause major casualties and property losses.metallic dust explosion is the most frequent type of combustible dust explosion,causing the most casualties.With the development of modern industry,the number of automobile parts manufacturing workshops is gradually increasing,and the safety production of the workshop has entered our vision.The dust composition produced by the high-pressure smelting process in an industrial workshop is complex,and its explosiveness is very different from that of a single powder.The previous prevention and control measures for single powder explosion are no longer applicable to the workshop.Therefore,to explore the explosion risk of mixed metallic dust in the workshop and the difference between the explosion characteristics of mixed metallic dust and single powder,and formulate appropriate prevention and control measures for the production workshop to ensure safe production,20 L explosion characteristic test system,dust cloud ignition energy test system and dust cloud ignition temperature test system are used to study and test the variation law of explosion characteristic parameters of mixed metallic dust and aluminum powder under the influence of different concentrations and particle sizes.The main work and conclusions are as follows:(1)Experimental study on explosion characteristics of mixed metallic dust.It was found that the maximum explosion pressure of mixed metallic dust is 0.693 MPa,the maximum pressure rise rate is 28.36 MPa/s,the lower explosion limit is 95 g/m~3,the minimum ignition energy of dust cloud is 56 MJ,and the minimum ignition temperature of the dust cloud is 573°C.These parameters can provide a theoretical basis for the explosion prevention and control of mixed metallic dust workshops.(2)The explosion characteristics of mixed metallic dust and aluminum powder were compared and analyzed.It is found that the sensitivity of mixed metallic dust to electrical spark is lower than that of aluminum powder,and its ignition energy is more affected by concentration and particle size.When the particle size is greater than 75μm,the required ignition energy is greater than 1000m J,which indicates that the sensitivity to electrical spark will gradually lose with the increase of particle size.The sensitivity of mixed metallic dust to temperature is higher than that of aluminum powder,and the minimum ignition temperature is lower but less affected by concentration and particle size.The lower explosion limit of mixed metallic dust is higher than that of general industrial dust.Compared with aluminum powder,the lower explosion limit is greatly affected by particle size.The maximum explosion pressure of mixed metallic dust is higher than that of aluminum powder,which can cause greater damage.However,it takes a long time to reach the maximum explosion pressure,and the mixed metallic dust can be protected against explosion at this point.(3)Explosion risk assessment of mixed metallic dust and aluminum powder.The results show that the explosion intensity and ignition sensitivity of mixed metallic dust are weaker than those of aluminum powder,but the explosion risk will gradually increase with the decrease of particle size.Therefore,controlling particle size is the most important factor for the prevention and control of mixed metallic dust.(4)According to the explosion characteristics of mixed metallic dust,the explosion prevention and control of dust removal system in mixed metallic dust workshop is divided into two parts:preventive measures before the explosion and restrictive measures when an explosion occurs.Explosion prevention can be carried out by eliminating ignition sources and combustibles.By analyzing the explosion relief and explosion suppression design of the dust removal system,the scope of explosion can be effectively limited and the loss caused by accidents can be reduced. |
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