Experimental Research On Explosive Characteristics Of Grain Dust In Beer Enterprises

Dust explosion is an explosion reaction about combustible dust dispersed in combustion air with a kind of mass concentration,and the effect of certain ignition energy.It widely exists in mechanical processing,energy,mining and food processing and other industries.Grain refining is the necessary daily production process that produces tiny grain dust.The grain dust mainly produce in the process of feeding inlet port about malt and rice,material bolting,and grinding production in beer enterprises.The normal conditions of dust explosion are floating or depositing of grain dust in the working space.Grain dust explosion incidents are frequently happened with serious accidents,which can easily cause casualties,property damage and environmental pollution.In order to let grain processing and production enterprises have more scientific guidance in safe management,and reduce or prevent the occurrence of grain dust explosions effectively,study on the conditions and influence factors of ignition and grain dust explosion are efficient ways to prevent these accidents.They also have certain theoretical significance and practical values.Learning grain dust explosion characteristics of beer enterprises in dust removal system,the experiment research has began with both of the ignition of pyrolysis characteristics and explosion characteristics.(1)Heating and ignition of grain dustAdopting the equipment of minimum ignition temperature,research in dust layer and dust cloud minimum ignition temperature of grains dust.Using the experiment of TGA-DSC type analyzer and CONE,study on pyrolysis characteristics of grains dust.The result shows that average of grain dust minimum ignition temperature(MIT)is140?;MITL is significantly cooler than MITC.With the decrease of dust particle size,the MITC showed same tendency.Grain dust thermo-gravimetric temperature began at202 ?,its maximal weightlessness rate is 0.41,the residual carbon amount is about30%.It is known with CONE method that tig is increased with increasing of the surface density of grain dust when was heated.As the dust particle decreases,tig is increased,and flame burn duration decreases in turn,and the heat release rate(HRR)is generally enhanced.At the same dust particle size,the time of the HRR peak increases while increasing the surface density of dust.At the same time,basic principle of grain dust pyrolysis was analyzed combining with the results.(2)The characteristics of grain dust explosionUsing 1.2 L Hartmann equipment,have experiment research on grain dust of beer enterprise.Mainly work from the dust particle size,mass concentration,moisture content,the ignition delay time factors,explore the relationship between these factors and dust explosion pressure(P)and the rate of pressure rise(dP/dt).Results show that the grain dust explosion limit concentration LEL is 125~166.67g/m3,the maximal dust explosion pressure Pmax is 1.81 MPa,corresponding to the maximum explosion pressure rise rate(dP/dt Max)to 10MPa·s-1.Finding out the rate of explosion pressure and explosive pressure have similar trend.LEL of the explosion was decreased from 141.67~150 g/m3 to 50~58.33g/m3 with the particle size increasing.Explosion pressure was reduced from0.90 MPa to 0.72 MPa.Because of the low specific surface area,grain dust was easier occur dust explosion.When the moisture content was reduced from 6.39% to 0%(absolute drying),explosion pressure increased from 1.3MPa to 2.1MPa.When the ignition delay are 8s and 12 s,the grain dust explosion is the most stressful.(3)Grading of grain dust and specific measuresCombined the theory of chain reaction analysis of dust fire and explosion reaction process,carries on the grain dust explosion hazard classification,and puts forward some specific suggestions for explosion prevention with the test results of the dust removal system in beer enterprise.