Effect of high temperature pretreatment on metallurgical properties of limonite lump ore
Natural lump ore has the characteristics of high grade,suitable particle size,loose structure and high po-rosity.It has certain advantages in the performance when used in the blast furnace.However,the problems of high humidity,high crystal water content and fine particles attached to the surface of natural lump ore have become the key to hinder the large-scale entry of lump ore into the furnace.High temperature pretreatment can effectively reduce the internal crystal water content of natural lump ore and improve the porosity.Based on this,the metallurgical properties of limonite before and after high temperature pretreatment was explored,and the feasibility of natural limonite into the furnace after high temperature pretreatment was judged.It is proved that the internal structure of limonite is changed by high temperature pretreatment,from compact dense structure to through-like plate structure,the content of crystal water is reduced,the porosity is increased,and the compressive strength is reduced.Low tem-perature reduction disintegration index(IRD)and reduction degree(Rt)are important indicators for evaluating the standard of ore raw materials into the furnace,and are the basis for judging whether the lump ore can be smoothly fed into the furnace,ensuring the permeability of the blast furnace and the smooth running of the blast furnace.High temperature pretreatment of natural limonite has a beneficial effect on its metallurgical properties.The proportion of small particle limonite falling is mainly reduced during the low temperature reduction disintegration process.After high temperature pretreatment,IRD＞6.30 of limonite increases from 66.12％to 73.21％,IRD＞3.15 increases from 82.08％to 86.48％,and IRD＜0.50 decreases from 7.97％to 6.47％.High temperature pretreatment mainly affects the contact area between reducing gas and limonite in the process of medium temperature reduction of limonite,that is,porosity is one of the factors affecting the reduction degree.After high temperature pretreatment,the average po-rosity of limonite increases by 4.77 percentage points,the reduction degree of limonite before high temperature pre-treatment increases from 79.58％to 84.23％.The research results can provide a theoretical basis for adding limo-nite into the furnace after high temperature pretreatment.
limonitepretreatmentcrystal waterreducibilitylow temperature reduction disintegration
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