| Acetylene(C2H2)is a highly flammable gaseous fuel whose combustion temperature is much higher than that of other hydrocarbon fuels,and it can be used in high-temperature welding and cutting industries.Calcium carbide(CaC2)is the main raw material for the preparation of C2H2 in industry.Due to its low price and simple production process,it has become a widely used solid acetylene source.Explosion accidents related to CaC2 occurred frequently during production and transportation,but there were few studies on dust explosion related to CaC2.Therefore,in-depth understanding of the essence,characteristics and influence factors of CaC2 dust explosion is helpful to prevent the occurrence of CaC2 dust explosion,reduce the harm,and provide scientific basis for the investigation of the cause of the accident.Based on this,this paper sets explosion properties of CaC2 dust as the main line.Using the standard 20 L spherical explosion test device and homemade visual isobaric dust explosion test device,the explosion characteristics of CaC2 dust and C2H2 gas multiphase system were carried out,and the explosion parameters and influence factors of CaC2 dust were systematically studied.The participation of CaC2 dust in the reaction process under C2H2 gas atmosphere was also studied.The effects of three typical powder suppressant(SiO2,Al(OH)3 and NaHCO3)on the inhibition of C2H2 gas explosion were analyzed.The main conclusions are as follows:(1)The explosion characteristics of CaC2 dust single phase medium were studied.When the relative humidity of air was 30%,CaC2 dust did not show any explosibility,which was independent of CaC2 dust concentration(100-700 g/m3).Moisture had a great influence on the explosibility of CaC2 dust.When the relative humidity of air was higher than 70%,CaC2 dust would explode weakly.When CaC2 dust was mixed with dry water powder,and as the CaC2 dust concentration was fixed(500 g/m3),the explosion pressure Pex value and the rise rate of explosion pressure(dP/dt)ex value showed a "parabolic" trend with the increasing content of dry water powder.When the mixed dust was prepared according to the stoicometric ratio of R=1,the Pex value first increased and then became stable.The inflection point of the(dP/dt)ex curve was 1400 g/m3.The average particle size of CaC2 dust sample had little influence on Pex value,but could affect(dP/dt)ex value greatly.(2)The explosion characteristics of C2H2/CaC2 dust multiphase media under different gas atmosphere were studied.When the stoichiometric ratio ? of C2H2 gas and air was 1.78,the C2H2-air explosion was the most violent,and the explosion risk was also very high.Under the same conditions,the Pex and(dP/dt)ex values of C2H2-air,C2H2/Ca(OH)2 dust and CaC2-dry water powder of the three groups were in the following orders:CaC2-dry water powder<C2H2/Ca(OH)2 dust<C2H2-air.CaC2 dust could enhance the explosion power and increase the explosion risk of C2H2 gas to some extent.In the study of C2H2/CaC2 dust hybrid explosion,the Pex and(dP/dt)ex values of C2H2/CaC2 dust mixture both increased at first and then decreased by increasing the CaC2 dust concentration.In the pure oxygen atmosphere,when the CaC2 dust concentration was high,the C2H2/CaC2 dust hybrid explosion showed two pressure rising stages.The Pex value of the first stage was less than that of the second stage,but the(dP/dt)ex value exhibited a totally different trend.(3)The explosion residues of C2H2/CaC2 dust hybrid explosion were analyzed systematically and the explosion reaction process was given via the XRD and SEM test and analysis methods.The explosion residues were Ca(OH)2 and CaO in the air atmosphere while only CaO in the oxygen atmosphere.In the process of C2H2/CaC2 dust hybrid explosion,the combustion of C2H2 gas would produce water which provided condition for the hydrolysis reaction of CaC2 dust.The hydrolysis reaction could produce C2H2 gas,and the secondary generation of C2H2 gas promoted the continuous explosion reaction of the mixture with positive feedback effect.Three kinds of powder suppressants(SiO2,Al(OH)3 and NaHCO3)were selected to inhibit C2H2 gas explosion.The explosion inhibition degree of SiO2,Al(OH)3 and NaHCO3 powder suppressants materials was given as follows:NaHCO3>Al(OH)3>SiO2.The inhibition mechanism of these three kinds of powder suppressants was analyzed.Figure[44]table[8]reference[112]... |
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