| Methane is widely used as a conventional fuel in production and life,but explosion accidents about methane frequently occur during the transportation and storage.It is an important research direction for traditional inorganic mineral explosion inhibitors due to its economic and environmental protection characteristics,but its poor performance is difficult to apply in industrial production.However,previous studies have shown that mineral powders with phosphorus-containing functional groups can play important chemical flame retardant properties.In order to explore hydroxyl,mercapto and urea functional groups how to affect the methane explosion,this paper used the methods gluconic acid impregnation and silane coupling agent grafting to prepare montmorillonite modified powders with these three kinds of groups.Firstly,the particle size,thermal properties and surface fuctional groups of the pure montmorillonite（Mt）,modified powders with hydroxyl（O-Mt）,mercapto（S-Mt）and urea（N-Mt）functional groups,respectively,were characterized by Malvern laser particle size analyzer,synchronous thermal analyzer and fourier transform infrared spectrometer.The results showed that characteristic peaks of hydroxyl,mercapto and urea groups were observed at 3400 cm-1-3700 cm-1,2557 cm-1,and 3390 cm-1 of the three kinds of modified powders,respectively.What’s more,the four kinds of powders have similar particle size and distribute uniformly after passing through a 300-mesh sieve.Secondly,using a 5 L duct experimental device,the suppression effects on the CH4 explosion of the four kinds of powders were tested respectively.The results showed that compared with Mt,O-Mt and N-Mt showed a significantly enhanced explosion suppression effect.When the concentration was 0.3 g/L,the maximum explosive pressures of methane for Mt,O-Mt,S-Mt and N-Mt was 50.98 mbar,26.59mbar,38.94 mbar and 30.23 mbar,respectively.And compared with no powder,the maximum explosion pressure decreased by 49.41%,73.61%,61.36%and 70%,respectively.The methane explosion flame propagation time of Mt,O-Mt,S-Mt and N-Mt was 37 ms,50.62 ms,37.5 ms and 51.5 ms.Compared with the absence of powder,the flame propagation time was extended by 236.36%,360.18%,259.1%and 363.63%,respectively.Comprehensive analysis showed that the suppression effect of the four kinds of powders is:O-Mt>N-Mt>S-Mt>Mt.Finally,in order to reflect the chemical reactivity of the four kinds of powders,the molecular electrostatic potential（MEP）,bond Mulliken population and bond lengths of surface functional groups were calculated by the DMol3 module of Material Studio molecular simulation software.The results showed that negatively electrophilic potential regions are mainly localized over the hydroxyl and urea groups of the O-Mt and N-Mt surface.What’s more,the areas of negatively electrophilic potential regions of O-Mt was more than that of N-Mt at the same MEP isosurface.And the hydroxyl and urea functional groups on the surface of O-Mt and N-Mt were easily broken to form?OH and NH4?,NCO?which are combined with flame radicals at high temperature conditions,respectively.The above calculation results are coincided with the results of the explosion suppression performance test,and which can reveal the methane suppression reaction mechanism of the modified powder. |
