High-chromium vanadium-titanium magnetite all-pellet integrated burden optimization and softening-melting behavior based on flux pellets

High-chromium vanadium-titanium magnetite(HVTM)is a crucial polymetallic-associated resource to be developed.The allpellet operation is a blast furnace trend that aims to reduce carbon dioxide emissions in the future.By referencing the production data of vanadium-titanium magnetite blast furnaces,this study explored the softening-melting behavior of high-chromium vanadium-titanium magnetite and obtained the optimal integrated burden based on flux pellets.The results show that the burden with a composition of 70wt%flux pellets and 30wt%acid pellets exhibits the best softening-melting properties.In comparison to that of the single burden,the softening-melting characteristic temperature of this burden composition was higher.The melting interval first increased from 307 to 362℃and then decreased to 282℃.The maximum pressure drop(ΔPmax)decreased from 26.76 to 19.01 kPa.The permeability index(S)dropped from 4643.5 to 2446.8 kPa·℃.The softening-melting properties of the integrated burden were apparently improved.The acid pellets played a role in withstanding load during the softening process.The flux pellets in the integrated burden exhibited a higher slag melting point,which increased the melting temperature during the melting process.The slag homogeneity and the TiC produced by over-reduction led to the gas permeability deterioration of the single burden.The segregation of the flux and acid pellets in the HVTM proportion and basicity mainly led to the better softening-melting properties of the integrated burden.

The research on the decomposition and softening-meltingproperties of iron ore by TG-DSC

13 kinds of iron ores （6 from Australia and 7 from Brazil） were studied on their properties concerning CW （Combined Water） decomposition, FezO3 decomposition and softening-melting in air atmosphere through the characterization method of TG-DSC （Thermogravimetry-Differential Scanning Caloremetry ）. The experimental results of the Australian ores and Brazilian ores differ in terms of the initial temperature, temperature range and endothermic amount of CW decomposition,and besides, the content of CW. It is estimated that for every percent increase of CW content in sintering raw material, the extra thermal amount absorbed in the process is about 1.83 x 104 kJ, which equals to the thermal capacity of 0.625 kg of standard coal burning up completely. As to the decomposition of Fe203 ,the initial temperatures, terminal temperatures and temperature ranges of the Australian and Brazilian ores are quite close. However, the endothermic amount of Fe2O3 decomposition of the two turns out rather different： the endothermic capacity of Fe2O3 decomposition of the Australian ores is greater than that of the Brazilian ores. Furthermore, the liquid amount generated in the softening-melting process is closely related to the SiO2 content in iron ore. The higher SiO2 content the ore contains, the more liquid volume it will generate in the softening-melting process of iron ore.

Effect of atmosphere and basicity on softening-melting behavior of primary slag formation in cohesive zone

The softening-melting characteristics of ferrous burden play a crucial role in the thickness and position of the cohesive zone.The influence of the basicity and experimental atmosphere on the softening-melting behavior of primary slag under slag-coke interaction was investigated using in situ visualization method.The mechanism was analyzed using the FactSage software,X-ray diffraction,and electron probe microanalysis.The softening and melting temperatures of the samples increased with increasing basicity under different atmospheres.The difference between softening and melting temperatures is smaller in a H_(2) atmosphere than in a CO atmosphere;in H_(2) atmosphere,the range of softening zone in the cohesive zone was significantly thinner.The formed low-melting-point FeO-bearing phases decrease when H_(2) was used as the reducing agent.In addition,according to FactSage calculations,the high content of metallic iron reduced in the H_(2) atmosphere raised the softening temperature of the primary slag.It also narrowed and moved downward the cohesive zone due to an increase in softening and melting temperatures.Meanwhile,the increase in basicity promoted the decrease in liquid ratio and improved the permeability of cohesive zone.

Effect of quaternary basicity on softening-melting behavior of primary slag based on magnesium flux pellet

It is generally accepted that the softening-melting properties of ferrous burden play a vital role in optimizing the shape and position of cohesive zone.The effect of quaternary basicity and atmosphere on softening,melting and permeation temperatures of primary slag based on magnesium flux pellet was investigated by visualization method.The mechanisms were analyzed utilizing thermodynamic calculation,X-ray diffraction analysis and electron probe microanalysis.The results indicated that the softening and melting temperatures of oxide samples increased by approximately 120℃with increasing quaternary basicity from 0.3 to 1.2 owing to the formation of slag phases with high melting point and solid Fe.Meanwhile,the difference between softening and melting temperatures decreased from 21 to 11℃.The permeation temperature was not affected by the quaternary basicity and fluctuated around a level of 1250 C,given that the permeation temperature depends on the wettability between slag and coke bed.On the other hand,as the ratios of CO/CO_(2) varied from 3/7 to 7/3,there were no significant differences in either the softening or melting temperatures,whereas the permeation temperature was increased from 1239 to 1271℃ since the reduction of FeO-bearing phases to solid Fe could decrease the wettability between slag and coke bed.

Effect of lump ore ratio on the metallurgical properties of blast furnace charge

We conducted a series of experimental studies on the metallurgical properties of N-lump and F-lump ores used in Baosteel’s blast furnace, including thermal cracking, low-temperature reduction pulverization, reducibility, and droplet properties.The results show that the thermal burst properties of N-lump ore are better than those of F-lump ore.The low-temperature reduction degradation index(RDI) pulverization of the charge is the best when the ratios of N-lump ore and F-lump ore account for 35% each.The reduction performance of the charge is improved when F-lump and N-lump ores are mixed with sinter.In the softening-melting performance experiment, when the proportion of N-lump ore is 40%,the characteristic area value(S) as the charge permeability index is the smallest.When F-lump ore is mixed with sinter, its droplet performance improves compared with that of single F-lump ore.The proportion of F-lump ore should not exceed 15%.

Effect of organic binders on the activation and properties of indurated magnetite pellets

In the ironmaking process,the addition of an organic binder to replace a portion of bentonite has the potential to improve the per-formance of pellets.The interaction between original bentonite(OB)and organic binder was investigated.Results indicated that the micromor-phology of organic composite bentonite(OCB)became porous and the infrared difference spectrum exhibited a curved shape.In addition,the residual burning rates of OB and organic binder were determined to be 82.72%and 2.30%,respectively.Finally,the influence of OCB on the properties of pellets was investigated.The compressive strength of OCB-added green pellets(14.7 N per pellet)was better than that of OB-ad-ded pellets(10.3 N per pellet).Moreover,the range of melting temperature of OCB-added green pellets(173℃)was narrower than that of OB-added pellets(198℃).The compressive strength of OCB-added green pellets increased from 2156 to 3156 N per pellet with the increase in roasting temperature from 1200 to 1250℃.