Explosion Characteristics Of 7-ACA Powders And Its Explosion Resistance In The Acetone

Taking 7-ACA drug powder as the research sample,this thesis studied explosion characteristics of acetone and drug powder mixture,and assessed the risk of blasting of the mixture,which can provide reference for the selection of electrical equipment and the development of explosion protection measures.The thermodynamics of powders was studied by thermal gravimetric analysis(TGA).The minimum ignition temperature,the minimum ignition energy,the maximum explosion pressure and the rising rate of the explosion pressure of the dust layer and the dust cloud of the mixture of powder and acetone were measured.The suppression effects of nitrogen,carbon dioxide and argon gas were compared.The main results are as follows:The thermal dynamics of 7-ACA dust combustion was studied by thermal gravimetric analysis.Through the thermo gravimetric curve analysis,the minimum ignition temperature of 7-ACA dust was nearby 220℃.The activation energies of 7-ACA dust were changed from 7.347k/mol to 146.99k/mol,and the pre-exponential factor increased from1.4×107 to 9.18×1011 with the depth of the reaction.It can be known that 7-ACA dust explosion is a process of rapid increase in energy in a short time which is composed of variety types of chemical reaction.The minimum ignition temperature of 7-ACA dust cloud was 472℃.When acetone was added to the powder,the minimum ignition temperature was 411℃ when the mass of 7-ACA was 0.6g.The minimum ignition temperature of dust cloud was obviously reduced which led to the explosion risk obviously increased.The lowest ignition temperature of 12.5 mm thick 7-ACA dust layer was 230℃,the powder occurred in flameless combustion.After the addition of acetone,the time of dust combustion was increased.The minimum ignition energy of the dry 7-ACA powder can reach a minimum value of 12 mJ at the dispersion mass of 0.7g that belonged to the general fire sensitive dust according to the provisions of VDI2263.After adding acetone,the minimum ignition energy was decreased.When the dispersion quality was 0.6g,the minimum ignition energy was 4mJ.The flame burned more violently,and it belonged to special fire sensitive dust.Compared with the dry powder test results,the explosion index of dry powder is 15.17 Mpa · m/s,belonging to St1 level;The explosion index of dust in acetone environment is 39.27MPa·m/s,belonging to St3 level,and the explosive risk increased significantly according to the requirements of ISO 6184.The dust concentration to reach the maximum explosion pressure and the maximum explosion pressure rise rate is obviously decreased.The maximum value of the maximum explosion pressure rising rate increased significantly,and the explosion intensity increased.The limiting oxygen concentration of carbon dioxide as inert medium is 12.62%.The limiting oxygen concentration of nitrogen is 11.77%,and the limiting oxygen concentration of argon is 9.56%.Compared with the effect of explosion suppression of three kinds of inert gas,the explosion suppression of carbon dioxide is the best,followed by nitrogen.However,in the process of industrial production,considering the economic factors and operability,nitrogen gas is usually used as an explosion suppression gas.