Study On The Explosion Characteristics And Protection Of Thermosetting Electrostatic Spraying Powder

In the field of dust explosion protection,explosion isolation flap valves and flameless relief are widely used in dust explosion-related enterprises,while the current research on both is still lacking data support and experimental verification in large size,making it difficult to effectively guide their practical application.Based on this,this paper takes thermosetting electrostatic spraying powder as the object of research,dust explosion characteristics and protection research,focused on the study of dust explosion pressure characteristics in combination with pressure relief and explosion isolation under straight pipe condition and on flame and pressure characteristics under flameless venting condition,the specific content is as follows:（1）Selected polyester,polyester/epoxy three types of spray powder,and add pure polyester resin and pure epoxy resin powder samples as a control,the five samples of differential scanning calorimetric analysis,explosion fierceness and explosion sensitivity of the experimental study,the results found that:three electrostatic spray powder exothermic heat is significantly smaller than pure resin powder;three spray powder maximum explosion pressure in the 0.77～0.81MPa range,K_St in the range of 11.5～14.5 MPa·m·s^-1,all belong to the St1level;explosion sensitivity is basically the same,the minimum ignition energy of 10～100m J,the lowest ignition temperature of 460～480℃,the lowest explosion limit of 30～60g/m³.（2）The explosion isolation flap valve was used as a means of protection for the explosion isolation of the 2m³ pressure vessel,and the dust explosion pressure characteristics of the combination of pressure relief and explosion isolation were studied by changing the installation distance of the explosion isolation valve and pressure relief area.The results show that the reflective effect of the flap valve results in a secondary pressure peak in the vessel that is slightly less than the first peak.As the installation distance of the flap valve increases from3m to 7m,the pressure peak at the front of the valve plate rises from 0.067MPa to 0.101MPa,and the pressure peak inside the vessel also rises significantly;by reducing the installation distance,the interval between the two pressure peaks is shortened and the pressure fluctuation is more violent;however,the increase of the relief area may increase the closing time of valve plate,resulting in the failure of the explosion isolation.（3）Conventional and flameless venting devices were used as explosion relief methods for the 8.4m³ pressure vessel respectively,when the dust concentration from 125g/m³ increased to 250g/m³,flameless venting than conventional venting explosion pressure increased by14.3%,27.8%,while the dust concentration of 500g/m³,flameless venting flame arrest failure;when the venting area from 0.528m² to 0.168m²,the explosion pressure increased by 41.3%.At the same time the direct comparison method of EN-14797 has been improved to avoid the errors of the original method of pure calculation,and can be used as a method of obtaining quantitative indicators to assess the effectiveness of flameless venting of St1 dust explosions.（4）A high-speed camera and an infrared thermal imaging camera were used to record the flame pattern of conventional venting and the temperature change of the flameless venting process.The results showed that the maximum temperature of the flame during conventional venting and the maximum temperature of the surface of the flameless venting device both increased with the increase of dust concentration.At low dust concentrations during conventional venting,the venting flame is a turbulent combustion flame;at high dust concentrations,under-expansion jet flames,turbulent jet flames and turbulent combustion flames appear at the venting port in this order.