| A massive abandoned dust will be generated at the outlet lintel during the underground mining process in high sulfur iron ore mine.And it will easily lead to dust explosion once it contacts with the ignition source when the dust is suspended in the air to form a dust cloud and reach a certain concentration.Previous studies have mostly focused on the investigation of dust cloud explosion intensity parameters and explosion process mechanism regarding the explosion of high sulfur iron ore dust clouds,while neglecting the study of dust cloud explosion inhibition.In this paper,taking pyrite-pyrrhotite dust as the object,the three typical powder explosion suppressants,melamine cyanurate MCA,melamine polyphosphate MPP and the two complexes MCA-MPP,were selected to investigate the effect of powder explosion suppressants on the explosion overpressure of pyrite-pyrrhotite dust.The effect of suppressants on the thermal properties of pyrite-pyrrhotite dust during the explosion was analyzed.The effect of suppressant on the composition and apparent structure of solid products was investigated.And the inhibitory effect of suppressants on the explosion of pyrite-pyrrhotite dust clouds was discussed combining the experimental results with theoretical analysis.The research contents and conclusions are as follows:(1)The effect of suppressants on the explosion overpressure and combustion time of pyrite-pyrrhotite pyrite dust clouds was studied.The maximum explosion pressure of pyritepyrrhotite dust cloud increases and then decreases with increasing mass of MCA,MPP and MCA-MPP.And the maximum explosion pressure was 0.30 MPa,0.34 MPa and 0.32 MPa when MCA,MPP and MCA-MPP were added at 0.6 g,0.8 g and 0.6 g,respectively.Comparing the explosion overpressure suppression performance of the three suppressants,it was found that MCA > MCA-MPP > MPP.In addition,the explosion combustion time of pyrite-pyrrhotite dust cloud showed an overall increasing trend with increasing amounts of MCA,MPP,and MCAMPP additions.And the explosion combustion time was 103.5 ms,86.5 ms and 75 ms,respectively when added 2.0 g the three suppressants.(2)The effect of powder explosion suppressant on the thermal properties of pyritemagnetite pyrite dust was investigated.The pyrite-pyrrhotite dust undergoes five stages of weight loss in the temperature range of 110.3 °C to 652 °C,with a total weight loss rate of31.8 %.MCA undergoes only one stage of weight loss in the temperature range of 268 °C to406.5 °C,with a total weight loss rate of 95.2 %.And MPP undergoes three stages of weight loss in the temperature range of 320 °C to 735.3 °C,with the total weight loss rate was about70 %.The pyrite-pyrrhotite dust underwent four pyrolysis stages after the addition of MCA,while the dust underwent five pyrolysis stages after the addition of MPP and MCA-MPP.The initiation and termination temperature of dust pyrolysis increased with the increase of MCA,MPP,and MCA-MPP contents,with the most obvious increase in the termination temperature of the second weight loss stage,which increased by about 160-190 ℃.(3)The effect of powder explosion suppressant on the pyrolysis solid products of pyritepyrrhotite dust was researched.The powder explosion suppressants MCA,MPP and MCA-MPP does not react directly with pyrite-pyrrhotite dust.Both MCA and MPP retard the pyrolysis process of pyrite-pyrrhotite dust particles and hinder their oxidation.Among them,MCA has the best performance in retarding the pyrolysis of dust particles,while MCA-MPP has the worst performance.The fissures on the solid products of pyrolysis of pyrite-magnetite pyrite dust are filled by the pyrolysis residue of MCA and MPP adsorbed on the surface of dust particles.(4)The inhibitory effect of powder explosion suppressants on pyrite-pyrrhotite dust explosion was discussed.There are four inhibitory effects of MCA and MPP on the explosion of pyrite-pyrrhotite dust clouds: collision,heat absorption,dilution and pore plugging. |
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