Synergistic Effects Of Mechanical Activation And Environmental Factors On Spontaneous Combustion Of Sulfide Ores

Spontaneous combustion of sulfide ores will trigger a series of environmental and safety issues,and cause huge economic losses.The ore body crushed by varieties of mechanical forces simultaneously is a complex process of physical and chemical effects.It can make ores crushed,smaller particle size and larger specific surface area.Besides,it also affects the sulfide ores' microscopic crystalline structure and generated lattice defects internally,resulting in enhancing the chemical reactivity of the sulfide ores.After crushing,the whole process of oxidation spontaneous combustion of sulfide ores will be influenced by many kinds of environmental factors.Therefore,it is necessary to explore the general law of the spontaneous combustion of sulfide ore induced by mechanical force and environmental factors.The main research contents of this thesis are as follows:(1)By means of scanning electron microscopy and X-ray photoelectron spectroscopy,the micro morphology and phase analysis of sulfide ores after mechanical activation were studied.The results show that with the enhancing of mechanical activation,it can be seen clearly that the sample surface after mechanical activation is much more compact and rougher than that before mechanical activation,indicating an intense erosion due to the oxidation process.The elements(Fe,S)valence of sulfide ores after mechanical activation changes,its oxidation behaviors enhanced.(2)The relationship of oxidation weight gain-sample to ball ratio and oxidation weight gain—mill speed was studied.The results show that,the order of weight gain rate under different sample to ball ratios is:raw ore<a(1:3)<b(1:6)<c(1:10);and that of samples under different mill speeds is:raw ore<d(300r/min)<e(400r/min)<f(500r/min).In addition,By using the orthogonal experiment method,temperature,humidity,rate of water content,pH value are selected as indexes,the order of four environmental factors influencing the oxidation degree of sulfide ores is as follow:rate of water content>humidity>temperature>pH value.What's more,the increase of water content,temperature,humidity and the decrease of pH value play a role in promoting the oxidation of ores within limits.(3)Low-temperature nitrogen gas adsorption were performed to show that gas adsorption of sulfide ores under mechanical activation mainly occurs in the mesopores varying from 2 to 30 nm.The order of specific surface area for samples under different sample to ball ratios is:a(1:3)<b(1:6)<c(1:10);and that of samples under different mill speeds is:d(300r/min)<e(400r/min)<f(500r/min).The order of samples' fractal dimension is consistent with that of specific surface area,but average pore diameter is the exact opposite of that.Mechanical activation increases the fractal dimension of sulfide ore and improves the ability of oxygen adsorption,thus contributing to oxidation and spontaneous combustion.(4)By using simultaneous thermal analyzer,the effects of heating rate and air flow rate on the kinetic parameters of sulfide ore after mechanical activation were studied.With the heating rate increase,activation energy decreased.What's more,when the heating rate is low,the activation energy is decreased greatly.When air flow is increasing,activation energy of samples decreased first and then increased substantially.The turning point is roughly 30ml/min.Comparing the results of different thermal analysis methods,it is found that although the results of different thermal analysis can reflect process of oxidative decomposition of sulfide ores,the specific methods and the results are quite different.The kinetic parameters of the oxidation and decomposition process of sulfide ores can be well reflected by using the Doyle and FWO.