Diffusion and reaction mechanism of limestone and quartz in fluxed iron ore pellet roasting process

The increase to the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking process.In this study,the interaction between calcium carbonate and iron ore powder and the mineralization mechanism of fluxed iron ore pellet in the roasting process were investigated through diffusion couple experiments.Scanning electron microscopy with energy dispersive spectroscopy was used to study the elements’diffusion and phase transformation during the roasting process.The results indicated that limestone decomposed into calcium oxide,and magnetite was oxidized to hematite at the early stage of preheating.With the increase in roasting temperature,the diffusion rate of Fe and Ca was obviously accelerated,while the diffusion rate of Si was relatively slow.The order of magnitude of interdiffusion coefficient of Fe_(2)O_(3)-CaO diffusion couple was 10^(−10) m^(2)·s^(−1) at a roasting temperature of 1200℃for 9 h.Ca_(2)Fe_(2)O_(5) was the initial product in the Fe_(2)O_(3)-CaO-SiO_(2) diffusion interface,and then Ca_(2)Fe_(2)O_(5) continued to react with Fe_(2)O_(3) to form CaFe_(2)O_(4).With the expansion of the diffusion region,the sillico-ferrite of calcium liquid phase was produced due to the melting of SiO_(2) into CaFe_(2)O_(4),which can strengthen the consolidation of fluxed pellets.Furthermore,andradite would be formed around a small part of quartz particles,which is also conducive to the consolidation of fluxed pellets.In addition,the principle diagram of limestone and quartz diffusion reaction in the process of fluxed pellet roasting was discussed.

Oxidation and Induration Characteristics of Pellets Made from Western Australian Ultrafine Magnetite Concentrates and Its Utilization Strategy

Western Australian magnetite concentrates normally have ultrafine granularity and much higher specific surface areas than Chinese magnetite concentrates owing to the significant pre-grinding and beneficiation for saleable iron grade. Such characteristics will inevitably affect the subsequent pelletization process. However, very few investi- gations have been done before. Thus, the oxidation and induration characteristics of pellet made from a Western Aus- tralian ultrafine magnetite concentrate were revealed by conducting routine preheating-roasting tests in an electric tube furnace and investigating the microstructure of fired pellets under an optical microscope in comparison with that of pellets made from typical Chinese magnetite concentrate. The liquidus regions of CaO-SiO2-Fe2O3 and CaO-SiO2- Al2O3 ternary systems in air at various temperatures were calculated by FactSage software to explain the importance of liquid phase in the consolidation of fired pellets. The results show that pellet made from ultrafine magnetite con- centrate possesses better oxidability and preheating performance than that made from Chinese magnetite concentrate. However, it has inferior roasting performance, usually requiring conditions of roasting at 1280℃ for at least 30 rain to acquire sufficiently high compressive strength, which are attributed to higher temperature sensitivity caused by its smaller particle size and less formation of liquid phase because of low impurities like CaO and Al2O3 in raw materials. Correspondingly, its roasting performanee can be significantly improved by blending with Chinese magnetite concen- trates or increasing the pellet basicity （WCaO/WSiO2）. By comprehensive evaluation, blending with Chinese iron ore concentrates is an appropriate way to utilize Western Australia ultrafine magnetite concentrates.

Utilization of High Sulfur Raw Materials in Iron Ore Pellets

Pyrite cinder and high sulfur magnetite were used as raw materials to produce iron ore pellets. Good quali ties of green balls and fired pellets were obtained from the feed comprising 50G pyrite cinder and 50% high sulfur magnetite concentrate at a small scale. Small scale tests were proven by pilot-scale tests. The high grade fired pel lets, assaying 63. 22% Fe, were analyzed, and the compressive strength of fired pellets was over 2 500 N/pellet. The fired pellets possessed excellent metallurgical performances, such as reducibility index higher than 67%, reduction swelling index lower than 15% and low temperature reduction degradation index （＋ 3.15 mm） higher than 1%, which can be used as the hurden for blast furnace.

Mechanism of improved magnetizing roasting of siderite–hematite iron ore using a synergistic CO–H2 mixture

A fluidized-bed magnetizing roasting-magnetic separation process was selected to treat this type of material.Phase transformations and microstructural changes in the product resulting from magnetizing roasting under different reducing gases(CO,H2,CO+H2)were clarified by vibrating sample magnetometry,X-ray diffraction,scanning electron microscopy,and energy-dispersive X-ray spectroscopy.The results indicated that the conversion ratio and saturation magnetization of samples roasted in a mixed gas of CO and H2 were higher than those of samples produced under CO or H2 alone.This indicated that synergy of the combined CO and H2 gas had a positive effect on the fluidized-bed magnetizing roasting process.The mechanism and kinetics of the improved magnetizing roasting of a siderite-hematite iron ore mixture under this synergistic CO-H2 system were investigated under isothermal conditions.The results indicated that the apparent activation energies of the reactions of the iron oxides decreased from 37.7 and 17.9 to 15.9 kJ/moI when the roasting atmosphere was changed from pure H2 or CO to a gas mixture of CO and H2,respectively.The mixed CO-H2 gas promoted the conversion ratio of hematite and siderite to magnetite,thereby improving the conversion ratio in the fluidized-bed magnetizing roasting process.

A quantitative investigation on consolidation of titanium-containing pellets during roasting process

The measurement method and quantitative indexes of iron ore consolidation characteristic temperature(CCT)during roasting,including consolidation starting temperature,highest consolidation rate temperature,and consolidation termination temperature,were improved based on previous research.The mineral properties of V-Ti magnetite(Panzhihua)were analyzed,and the CCT of V-Ti magnetite was calculated.To investigate the effect of mineral types on CCT,a series of trials were carried out by using various ores,including high-grade magnetite ore,high silicon iron ore,and V-Ti magnetite ore.The greatest shrinkage of V-Ti magnetite was 6.7%,the consolidation starting temperature was 991℃,and the termination temperature was 1384℃.The results of X-ray diffraction analysis indicated that the V-Ti magnetite ore was composed of titanomagnetite,peridotite,and other minerals,which is more complicated than conventional magnetite.As a result,the temperature at the maximum rate of consolidation and the temperature at the termination of consolidation are the greatest.FeTiO_(3) and MgFe_(2)O_(4) in V-Ti magnetite may inhibit the creation of sinter necks between hematite particles.Liquid phase occurs inside the pellet when the temperature surpasses 1250℃,which may accelerate particle growth and the formation of a sintering neck within the pellets.

Raman Spectroscopic Core Scanning for Iron Ore Characterisation

Automated core scanning technologies for mineralogical characterisation of diamond core, drill chips pulps is now an established technique, particularly in the Australian iron ore industry, for mineral analysis in exploration and mining. Application of reflectance spectroscopy over the 400–2500 nm, visible to near-infrared wavelength range, has been used to characterise the iron ore oxide mineralogy of bedded iron deposit (BID) derived iron ores in India (Thangavelu et al., 2011) and Brazil (da Costa et al., 2009), and used to define the ore and gangue (e.g., clay) mineralogy in ironstone or channel iron deposits (CID) in the Pilbara region of Western Australia (e.g., Haest et al., 2012).

配加粉尘对铁精矿生球爆裂温度的影响规律

针对弓长岭球团厂配加粉尘的生球爆裂温度低的问题,分析了粉尘的物化性能,研究了配加粉尘对铁精矿生球爆裂温度的影响。结果表明:配加质量分数4%的粉尘可提高生球的落下强度和抗压强度,但生球的爆裂温度下降;当磁铁矿和赤铁矿水分超过9.50%时,所造生球爆裂温度<500℃。分析粉尘对影响生球爆裂温度的机理可知:粉尘具有的较细粒度、较强亲水性、较高比表面积和不合理粒度组成等特点,是导致生球爆裂温度<500℃的主要原因。结合现场实际,建议通过将磁铁矿和赤铁矿水分调整为9%后再参与配料,是保证生球爆裂温度超过500℃的有效措施之一。

以巴西赤铁矿为主配加磁铁矿、硼铁矿的球团试验

本文研究了配加磁铁矿和硼铁矿对巴西赤铁矿球团质量及热工制度的影响。结果表明,配加20%磁铁矿或10%硼铁矿均能降低焙烧温度,缩短焙烧时间,且预热球和焙烧球抗压强度得到明显提高,而以配加硼铁矿的效果最为显著,但球团矿的冶金性能并未得到改善。

Geological Specimens, Minerals, and Actions Affecting Polar Shift and Earth’s Magnetic Field

This study will touch upon Earth’s magnetic field, the four spheres, and their relationship with polar shift influenced by the magnetization of the interior and surface areas. It will outline how certain aspects within the spheres are influenced by magnetization of minerals and localized rock, how such can be contained deep within Earth’s mantle areas, as well as how mining deposits of iron ore can affect other spheres and systems. It will also entail a brief explanation of geological research concerning the Pacific Ocean floor, as well as a discussion on the magnetization of minerals retaining their properties at extremely high temperatures within Earth’s interior. There will be explanations of how various spheres interact with each other, but it should be noted that while some findings here might seem unsubstantiated, any analysis of Earth’s interior and exterior, the magnetic field, polar shift, and its contagion effect upon living organisms, is still, somewhat, in its initial research stages, and is, at times, left to hypotheses concerning anomalous indications. This study is not conclusive. It has, at best, pieced together areas of relevance. Concluded here is that each event affects polar shift. How this has been affected by magnetization is not completely, at this time, understood. Furthermore, this report in no way promotes the “doomsday scenario”, prolific, fairly recently, within some of the scientific literature on this subject, particularly in Europe. This paper closely adheres to the most modern theories, and will try, at best, to leave speculation to science fiction writers.