| Along with the continuous development of iron and steel, the reasonable burden structure are growing increasingly in the blast furnace, and acid pellet adding highly basic sinter is considered as a kind of reasonable burden structure. Now, many iron and steel enterprises all produce magnetite pellet to optimize burden structure in my country. But, in my country, all the pelletability of raw matrial-magnetite concentrate is low. So, many pellet enterprises solut the question through the addition of bentonit. It not only make high cost of pellet production, but also have an unfavorable effect of ironmaking.In this paper, the question of low pelletability is soluted by using to pretreat magnetite concentrate. The physicochemical properties of magnetite concetrate is changed by mechanical force. So, improved the strength of green pellets, and reduced the bentonit content. Appropriate technological data of damp mill: the dampmill time is six minutes, the pecentage moisture of magnetite concentrate is 6, the processing rate of lab-damp mill is 0,06t/h, the rotating speed is 0.7-0.8 times of critical rotating speed, the filling ratio of damp mill is about 17%, the high compose of small steel ball ratio of damp mill is good effection. Appropriate technological data of high pressure grinding: the roll pressure is 2.23Mpa, the rotation speed is 100 circle per minute, number of grinding is two.In this paper, SEM, The Laster Size Analyzer, Specific Area measurement, Micro thermal gravimetry and X-ray Diffraction is used to determine the mechanisms of mechanochemical(MC) about pretreat magnetite concetrate. It has been shown that: When the magnetite concentrate is pretreated, it's average size is decreased, small size content is increased, it's size log-normal distribution is more like normal distribution, The content of -45#m size is inceased about 11%. Especially, l#m~10#m size is increased from 13% to 24% and 20%. When it is pretreated by high pressure roller, all the shape of grain like needle, slice, grate, and somes have crack. In the procession of balling, This shape form mechano-combination force, and improve the strength of green pellets. When the magnetite concentrate was pretreaded by damp mill and high pressure roller, the moistening thermal is increased from 1.45X 10'5J/cm2 to 9.78 X 10-5J/cm. So, it's specific free energy is increased, resulting in the increasing of it's activity and surface-absorb force, and resulting in higher surface activity of magnetite concetrate. It's pelletability index is increased from 0.242 to 0.380 and 0.648; the green strength is increased to 2-3times/0.5m. The bentonit content reduce to 1.0%, and attain to the foreign advancedlevel. When it is pretreated by damp mill and high pressure roller, the peak of diffraction is widen, the strength of diffraction is decreased. Crystal lattice deformation,plastic deformation and crystal defect is occurred. The degree of Crystal lattice deformation is increased 0.32%, the activation is decreaed from 33.96KJ/mol to 31.68KJ/mol and 31.28KJ/mol. This promote the oxidation of magnetite pellet, the strength of induration is increased about 1000N. All that explain: it is validity path for the damp mill and the high pressure roller to solute the problem that the coarser size of magnetite concentrate and the higher addition of bentonit. |
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