Study On The Synergistic Inhibition Law And Mechanism Of Gas-Solid Inhibitors On Aluminum Dust Explosion

The vigorous development of the machinery manufacturing industry has led to the prosperity of the surface processing industry of aluminum products.Suspended aluminum dust,as the main by-product of surface processing industry,has high reactivity and high energy density.When the aluminum dust concentration is within the explosion limit range,it is easily to trigger explosion accidents,which poses a serious threat to safety production of aluminum products.Therefore,how to mitigate the consequence of aluminum dust explosion has become a bottleneck restricting the industrial safety production.Explosion inhibition technology is widely used in chemical equipment as an efficient and economical means of explosion protection.The technology uses high pressure gas as the driving force to drive solid inhibitors.However,previous studies mostly focused on the inhibition performance of single-phase inhibitors,and the understanding of the synergistic inhibition law of gas-solid inhibitors in inhibiting aluminum dust explosion was insufficient,especially the research on the inhibition mechanism of gas-solid inhibitors was relatively scarce.To this end,the synergistic inhibition effect of the ABC-CO2 and MCA-CO2 inhibitors on 5 μm and 30 μm aluminum dust explosion was studied,a kinetic model of chemical reaction of gas-phase combustion and heterogeneous combustion of aluminum dust inhibited by gas-solid inhibitors was established based on the explosion product analysis,and the inhibition mechanism of gas-solid inhibitors was further revealed.It will provide theoretical support for the synthesis of new inhibitors and the design of explosion inhibition system,and build a safety barrier to prevent and mitigate aluminum dust explosion in essence.The main contents and conclusions are listed below:(1)The inhibition capacity of gas inhibitor on aluminum dust explosion was systematically studied.The type and concentration of gaseous inertant both had influence on the flame propagation and explosion overpressure of aluminum dust explosion.When the concentration of gaseous inertant was increased,the flame diameter of gas-phase aluminum particle became smaller,the continuity of flame front of aluminum dust decreased,the combustion reaction zone became smaller and darker,the maximum flame propagation velocity reduced,and the maximum explosion pressure and the maximum rate of pressure rise of aluminum dust explosion decreased successively.CO2 showed superior inhibition capacity to N2 in inhibiting the micron aluminum dust explosion.When the dust concentration of aluminum particles was at its optimal concentration,the critical inhibition concentration of CO2 and N2 for 5 μm Al dust explosion was 95.0%and 96.4%,respectively.While the critical inhibition concentration of CO2 and N2 for 30 μm Al dust explosion was 93.0%and 95.2%,respectively.However,they all came at the high cost concentration of CO2.Therefore,CO2 should be used as the driving gas to drive solid inhibitor.(2)The synergistic inhibition effect of aluminum dust explosion by gas-solid inhibitors and the optimal inhibition condition were systematically studied.When the concentration of inhibitors was increased,the time of dust was ignited prolonged,the scatter degree of the flame combustion zone increased,the maximum flame propagation velocity decreased,the maximum explosion pressure and the maximum rate of pressure rise of aluminum dust explosion decreased successively.When the dust concentration of aluminum particles was at its optimal concentration,applying 800 g/m3 ABC and 45.0%CO2 can completely inhibit the 5 μm aluminum dust explosion.The required concentration was reduced 42.9%comparing with when only ABC was applied,and the required concentration was reduced 52.6%comparing with when only CO2 was applied.Moreover,applying 160 g/m3 MCA and 32.5%CO2 can completely inhibit the 30 μm aluminum dust explosion.The required concentration was reduced 36.0%comparing with when only MCA was applied,and the required concentration was reduced 65.1%comparing with when only CO2 was applied.(3)A kinetic model of chemical reaction of gas-phase combustion and heterogeneous combustion of aluminum dust inhibited by gas-solid inhibitors was established.Compared with single-phase inhibitors,the addition of ABC-CO2 and MCA-CO2 inhibitors had synergistic inhibition effects on the flame temperature,the mole fraction and the maximum rate of production of key free radicals of aluminum dust in gas-phase combustion.ABC-CO2 inhibitors also had a synergistic inhibition effect on the maximum rate of production of key surface species of heterogeneous combustion of aluminum dust.The occupied open site of aluminum particles became larger and the heterogeneous combustion was further inhibited.(4)The inhibition mechanism of aluminum dust explosion by ABC-CO2 and MCA-CO2 inhibitors was revealed.The inhibition mechanism of ABC-CO2 and MCA-CO2 inhibitors was mainly composed of physical and chemical effects.Physical effect included collision,cooling and dilution exerted by CO2,heat absorption and covering of solid inhibitors,and inhibition of pyrolysis gases.As for the chemical effect,it was that the small molecule substances produced by the thermal decomposition of the solid inhibitors played a chemical inhibition effect through free radical capture reactions,such as HPO3+O<=>HOPO+O2,HNCO+O<=>CO2+NH,etc.Free radicals combined into more stable components and chain combustion reaction was further inhibited.