Study On The Microscopic Mechanism Of Spontaneous Combustion Of Sulfide Ores Induced By Mechanical Activation

Spontaneous combustion of sulfide ores is a complex and unstable physical and chemical reaction process.The whole process can be divided into ore crushing,low temperature oxidation,heating up and ignition,and so on.The mechanical forces can’t be simply regarded as a mechanical and physical behavior in different forms of sulfide ore deposit.It should be considered as a complicated physical and chemical process,which involves many kinds of mechanical forces acting on the ore body.It not only makes the ore crushing,smaller and the surface area larger,but also may destroy the lattice integrity,resulting in a large number of defects,which can cause the sulfide ore in a high energy state.Therefore,it is necessary to explore the general rule of spontaneous combustion of sulfide ores induced by mechanical forces.The main research contents of this thesis are as follows:(1)By means of X-ray diffraction,infrared spectroscopy,synchronous thermal analyzer,field emission scanner and other modern characterization techniques,the effects of mechanical stress on chalcopyrite and pyrite crystal structure,radical changes is studied systematic.Activation conditions about different mechanical strength(100r/min,200r/min,300r/min,350r/min,400r/min),ball milling time(20min,40min,60min,80min,120min)and material ball ratio(1:3,1:5,1:8,1:10,1:12)are analyzed from microscopic morphology,lattice defects,crystal block size,chemical composition and reaction kinetics of sulfide ores.Natural chalcopyrite in the activation of 80 minutes is 0.049%after the distortion of lattice,and the same ball milling conditions activated 20 minute samples of the lattice distortion is only 0.028%;Different mechanical activation intensity of crystal block size change order is greater than 1000nm(unactivated)>596mn/min>321nm(400r/min)>224nm(450r/min),and different material ball ratio under the condition of the lattice distortion,sulfide ore lattice distortion sequence is less than 0.1516%(unactivated)<0.02254%(1:3)<0.02254%(1:5)<0.03172%(1:10)<0.03543%(1:12).(2)The relationship of the oxidation weight gain and the ball milling time,the ratio of material and the mechanical strength of the sulfide ore was studied.The results show that,under the mechanical action of chalcopyrite oxidation rate and milling time,ball material ratio,mechanical strength.The weight of ore sample increased to 0.3992g in 450r/min.The rate of weight range from large to small sample respectively by oxidation of different mechanical strength is 450r/min>400r/min>350r/min>300r/min>200r/min>100r/min,which mechanical force condition and ore oxidation weight gain rate reached 4.98 percent in 450r/min,and when the speed is 100r/min,the mine like weight gain rate is the lowest,only 1.18%;In the material ratio of 1:3 ball milling conditions,ore samples in the thermostat to 15 days when the oxidation weight gain of 0.3992g,meanwhile the ball feed ratio of 1:12 is 0.8112g and the ore oxidation weight gain more effectively.At the same time,in different milling time,ball milling time is as long as the oxidation weight gain effect is more obvious.(3)With the help of infrared analysis technology,the different mechanical strength,ball to powder ratio,activation time of chalcopyrite and pyrite group changes is analyzed.The results show that:after the activation of the type and content of ore group changed significantly.Chalcopyrite activation in the 424.2cm-1,new peaks are found and in the multiple peaks are disappeared such as 400.1cm-1,527.5cm-1,669.4cm-1.If the time,ratio and force increased,ore appears new peaks again in 797.4cm-1 and 1383.5cm-1.After the activation of the internal composition of chalcopyrite group rupture generated new groups,The main reason is the[S2]2-and[SO3]2-are destroyed and generating derivatives of sulfur and sulfur.(4)Thermal analysis technique was used to characterize the samples with different mechanical forces(100-450r/min),different material-ball ratio(1:3-1:12)and different time(20-120min)after activation.Meanwhile,the X-ray diffraction spectrum of activated samples’ linear analysis was used to obtain the mechanical activation samples’ lattice distortion rate and block size.The results show that the kinetics reaction process of the sample complies with the diffusion one-way transport mechanism under the temperature between 530 to 640 ℃.By the increasing of mechanical strength and material ball,the apparent activation energy of samples reduces with good consistency.The samples in 200,350r/min under the condition of the apparent activation energy are 258.93,181.34,150.97 kJ/mol,corresponding to the pre exponential factor were 2.35× 1018,1.45× 1013 and 1.60× 1011.The sample material ball ratio of 1:3,1:5 under the condition of the activation energy was 240.57,150.97 kJ/mol,and the pre exponential factor are 1.58×1017,1.60×1011.The ore sample in milling 40min and 120min under the conditions of activation energy are 150.97,140.79kJ/mol,pre exponential factor are 1.58×1017,1.42 × 1O10.The reduction of apparent activation of the sulfide ores and lattice distortion rate increases and the crystallite size decreases have certain correlation,which easily lead to spontaneous combustion disaster.