Experimental Study On Characteristics Of The B Powder Explosion And Explosion Suppression

As an important reaction intermediate,pulverized B is widely used in dyestuffs,pesticides,pharmaceuticals,building materials,oils and fuels,etc.In the process of production and application,B dust also exists in the production space of various processes.In this paper,the particle size distribution,minimum ignition energy,lower explosion limit,limit oxygen concentration,maximum explosion pressure and explosion index of B dust are measured by standard instruments,and the explosion limit and explosion intensity are obtained.Taking this as the landing point,through a self-designed experimental device for dust combustion and explosion suppression in a circular pipe,the author further studied the flame movement law after B dust combustion,analyzed the variation law of upper flow field,studied the factors affecting B dust explosion,and studied the effect of different factors on B dust explosion when nitrogen and sodium bicarbonate were used as inhibitors.The median longitude of the B dust used in this test is 26.22 um.The minimum ignition energy of the dust is between 4.3-6.3 mJ,the lower explosion limit is between 40 g/m~3-50g/m~3,the limit oxygen concentration is 6%,the maximum explosion pressure is 0.72 MPa,and the explosion index is 22.77 MPa.m/s.It belongs to dust with an explosion danger and its blast intensity level is high.By studying B dust combustion,we can draw a conclusion.The flame of B dust combustion is random at first.Then the flow direction gradually moves towards the center,showing a spiral upward process.Finally,the flame develops into a constantly updated multi-layer mushroom cloud spreading state.The process of B dust explosion can be divided into a pyrolysis period,a violent explosion period and an extinguishing period.Under the same other conditions,the greater the pressure of powder injection,the shorter the pyrolysis period,the longer the violent explosion period and the extinguishing period,the higher the maximum flame height and extinguishing point height.Under the same other conditions,the larger the amount of dust is,the longer the pyrolysis period is,the longer the violent explosion period and the extinguishing period are,the higher the maximum flame height and extinguishing point height are.In the aspect of flame suppression of B dust explosion,this paper mainly proceeds from the factors of delay time,powder mass,pressure,jet time and suppression mode,and takes the explosion extinguishing time,the highest flame height and the final extinguishing point height as the indexes of flame suppression.The research concludes that,in the vertical pipe,With the increase of suppression pressure,the suppression of explosion flame of B dust by sodium-bicarbonate and nitrogen first increases and then decreases.The effect of sodium bicarbonate and nitrogen on explosion suppression decreases with the prolongation of delay time of explosion suppression action,and the better the flame suppression effect of B explosion with the increase of jet time.When the amount of suppressed powder is less than 1g,it has little effect on the explosive flame of isophthalonitrile.When the amount of suppressed powder exceeds 1 g,the rate of suppressing explosive flame of isophthalonitrile increases first and then decreases.Under the same other conditions,the inhibition effect of nitrogen and sodium bicarbonate is better than using nitrogen alone.