Experimental Study On The Explosion And Suppresion Characteristics Of High Dispersion Micro-aluminum Dust In The Confined Space

Aluminum powder is a kind of important metal industrial raw material,and its preparation is at high risk of smelting industry,which produces a large number of micron dust not only pollutes operating environment,but also has severe explosion hazard.Scholars at home and abroad have obtained certain achievements for the research on laws of aluminum powder explosion and suppression,but there are still some shortcomings in microscopic experiment research and quantitative analysis.In this paper,frequent aluminum powder explosion accidents in China and their serious casualties and huge property losses are the research background,based on SDT Q600 simultaneous thermal analyzer,20 L spherical explosive device and a self-designed powder dispersion device,micro-aluminum powder explosion and suppression characteristics regulars influenced by particle size,concentration,suppressant kinds and additive amount with experiments and theoretical analysis,obtained following main research results:?1?Reaction kinetics characteristics of micron-aluminum powder,suppressant and their mixtures heated in the air were studied.Combustion process of micro-aluminum in the air can be divided into five phases: stable phase,initial oxidation phase,crystal transition phase,severe burning phase and postoxidation phase.And the smaller the particle size,the stronger the combustion performance,the smaller the activation energy in the initial oxidation stage and of intense combustion stage.Explosion suppression mechanism of five suppressants are different which are potassium dihydrogen phosphate,calcium dihydrogen phosphate,ammonium dihydrogen phosphate,silicon dioxide and sodium chloride,can change the combustion reaction kinetics characteristics of micro-aluminum powder in different degrees.Inhibition effect is related to micro-aluminum powder particle size,suppressant additives and suppressant species.The larger the micro-aluminum powder particle size,the greater the suppressant additives,the higher the oxidation induced temperature and intense combustion temperature of micro-aluminum,the greater the activation energy in initial oxidation phase and intense combustion phase,and calcium dihydrogen phosphate is the preferred suppressant for micro-aluminum.?2?Regulars of explosion characteristic parameters and combustion time effected by micro-aluminum powder concentration and particle size were revealed.With micro-aluminum powder concentrations increase,P_m??dP/dt?_m and k_st show parabola change which is first increase and then decrease.P_max and?dP/dt?_max present as exponentially decay with particle sizes increase.A new parameter was defined—combustion time t of micro-aluminum powder in explosion process,combustion time decreases with micro-aluminum concentration powder increasing,and then gradually flatten out,which is exponential attenuation.Combustion time decreases with micro-aluminum powder particle size decreasing,which is linear variation.Explosion product of micro-aluminum powder is flocculent,micro-aluminum powder and its oxide Al₂O₃ exist together,which illustrate that micro-aluminum powder did not fully react in the explosion process,some did not participate in the explosion.?3?Dispersion process of micro-aluminum powder in the limited space was simulated,and the high dispersion and dynamic characteristics of micro-aluminum dust cloud was obtained.It demonstrated that the formation of explosive dust cloud only need a small trigger pressure in the instantaneous,which has certain guiding significance for the studies of aluminum dust explosion and suppression.?4?The factors of micron-aluminum powder explosion suppression effect were expounded,which were closely related to micron-aluminum powder particle size,the type of suppressant and suppressant additive amount.The smaller micro-aluminum powder particle size is,the more difficult to achieve explosion suppression effect.In this paper,explosion suppression effect of suppressant is best for 34-40 ?m aluminum powder,and the worst explosion suppression effect is for 1-2 ?m.Five suppressants can decrease the maximum explosion pressure,the maximum explosion pressure rise rate and the index in different degrees,lengthen the combustion time.The best suppressant is calcium dihydrogen phosphate for micro-aluminum,and ammonium dihydrogen phosphate cannot be used for micro-aluminum suppressant.The explosion suppression effect can be enhanced when suppressant additive amount is increasing.However,“SEEP” phenomenon will occur while suppressant additive amount is small,which means the insufficient suppressant additives may promote explosion.