New process for treating boron-bearing iron ore by flash reduction coupled with magnetic separation

Boron is an important industrial raw material often sourced from minerals containing different compounds that cocrystallize,which makes it difficult to separate the mineral phases through conventional beneficiation.This study proposed a new treatment called flash reduction-melting separation(FRMS)for boron-bearing iron concentrates.In this method,the concentrates were first flash-reduced at the temperature under which the particles melt,and the slag and the reduced iron phases disengaged at the particle scale.Good reduc-tion and melting effects were achieved above 1550℃.The B_(2)O_(3) content in the separated slag was over 18wt%,and the B content in the iron was less than 0.03wt%.The proposed FRMS method was tested to investigate the effects of factors such as ore particle size and tem-perature on the reduction and melting steps with and without pre-reducing the raw concentrate.The mineral phase transformation and morphology evolution in the ore particles during FRMS were also comprehensively analyzed.

Basic characteristics of Australian iron ore concentrate and its effects on sinter properties during the high-limonite sintering process

The basic characteristics of Australian iron ore concentrate (Ore-A) and its effects on sinter properties during a high-limonite sintering process were studied using micro-sinter and sinter pot methods. The results show that the Ore-A exhibits good granulation properties, strong liquid flow capability, high bonding phase strength and crystal strength, but poor assimilability. With increasing Ore-A ratio, the tumbler index and the reduction index (RI) of the sinter first increase and then decrease, whereas the softening interval (Delta T) and the softening start temperature (T (10%)) of the sinter exhibit the opposite behavior; the reduction degradation index (RDI+3.15) of the sinter increases linearly, but the sinter yield exhibits no obvious effects. With increasing Ore-A ratio, the distribution and crystallization of the minerals are improved, the main bonding phase first changes from silico-ferrite of calcium and aluminum (SFCA) to kirschsteinite, silicate, and SFCA and then transforms to 2CaO center dot SiO2 and SFCA. Given the utilization of Ore-A and the improvement of the sinter properties, the Ore-A ratio in the high-limonite sintering process is suggested to be controlled at approximately 6wt%.

Development of carbon composite iron ore micropellets by using the microfines of iron ore and carbon-bearing materials in iron making

Iron ore microfines and concentrate have very limited uses in sintering processes. They are used in pelletization; however, this process is cost intensive. Furthermore, the microfines of non-coking coal and other carbon-bearing materials, e.g., blast-furnace flue dust （BFD） and coke frees, are not used extensively in the metallurgical industry because of operational difficu]ties and handling problems. In the present work, to utilize these microfines, coal composite iron oxide micropellets （2-6 mm in size） were produced through an innovative technique in which lime and molasses were used as binding materials in the micropellets. The micropellets were subsequently treated with CO2 or the industrial waste gas to induce the chemical bond formation. The results show that, at a very high carbon level of 22wt% （38wt% coal）, the cold crushing strength and abrasion index of the micropellets are 2.5-3 kg/cm2 and 5wt%-9wt%, respectively; these values indicate that the pellets are suitable for cold handling. The developed micropellets have strong potential as a heat source in smelting reduction in iron making and sintering to reduce coke breeze. The micropellets produced with BFD and coke fines （8wt%-12wt%） were used in iron ore sin- tering and were observed to reduce the coke breeze consumption by 3%-4%. The quality of the produced sinter was at par with that of the conventional blast-furnace sinter.

Reduction–melting behaviors of boron-bearing iron concentrate/carbon composite pellets with addition of CaO

Although the total amount of boron resources in China is high, the grades of these resources are low. The authors have already proposed a new comprehensive utilization process of boron-bearing iron concentrate based on the iron nugget process. The present work describes a further optimization of the conditions used in the previous study. The effects of CaO on the reduction-melting behavior and properties of the boron-rich slag are presented. CaO improved the reduction of boron-bearing iron concentrate/carbon composite pellets when its content was less than lwt%. Melting separation of the composite pellets became difficult with the CaO content increased. The sulfur content of the iron nugget gradually decreased from 0.16wt% to 0.046wt% as the CaO content of the pellets increased from 1wt% to 5wt%. CaO negatively affected the iron yield and boron extraction efficiency of the boron-rich slag. The mineral phase evolution of the boron-rich slag during the reduction-melting separation of the composite pellets with added CaO was also deduced.

Development and Testing of a Method to Estimate the Mineral Composition of Ore from Chemical Assays with a View toward Geometallurgy: Application to an Iron Ore Concentrator

For complex orebodies in which the valuable metal is carried by several minerals that respond differently to the concentration process, an ore block model should not be characterized solely with elemental assays, as this information is not sufficient to anticipate the mill performances. Data from an iron ore concentrator is used to demonstrate the idea. A method is then proposed to estimate the mineral contents of ore samples from elemental assays. The method can readily be extended to combine the estimation of the mineral contents in the feed of the mill with an estimation of the recovery of these minerals into the products of the concentrator. These mineral recoveries can subsequently be incorporated into a block model to predict the concentrator response to the processing of an ore block.

An inhibition of ceruloplasmin expression induced by cerebral ischemia in the cortex and hippocampus of rats

Objective To explore effects of cerebral ischemia on the ceruloplasmin （Cp） expression in the cortex and hippoc-ampus of rats. Methods Male Wistar rats were randomly divided into cerebral ischemia group and control group. Cerebral ischemia was induced by ligating bilateral common carotid arteries and the ischemic rats were further subgrouped according to ischemia time. The control rats received a sham operation. The expression of Cp mRNA in the cortex and hippocampus was measured by reverse transcription polymerase chain reaction （RT-PCR）. The Cp expression was shown by immunohistochemistrical （streptavidin peroxidase, SP） method. Results In ischemia group, the expression of Cp mRNA in the cortex and hippocampus decreased compared with that in control group （P 〈 0.01）; and the longer rats experienced cerebral ischemia, the lower Cp mRNA expressed. By immunohistochemistry, Cp was shown expressed in the neural cells including epithelial cells of choroid plexus, ependymal cells, astrocytes of cortex and hippocampus, and vascular endothelial cells, but not in pyramidal cells and granulosa cells of cortex and hippocampus. Cp levels in the cortex and hippocampus decreased in rats suffering from cerebral ischemia for 3 d, 7 d and 28 d but not in rats exposed to ischemia for 1 d compared with that in control group （P 〈 0.05）. Iron concentration correlated negatively with Cp expression in the cortex and hippocampus of rats exposure to ischemia （the cortex, r=-0.831, P〈0.01; the hippocampus, r=-0.809, P〈0.01）. Conclusion Cerebral ischemia inhibited Cp expression in the cortex and hippocampus of rats. The decrease of Cp might be involved in iron deposition in neurons.

Carbothermic reduction behaviors of Ti–Nb-bearing Fe concentrate from Bayan Obo ore in China

To support the development of technology to utilize low-grade Ti-Nb-bearing Fe concentrate, the reduction of the concentrate by coal was systematically investigated in the present paper. A liquid phase formed when the Ti Nb-bearing Fe concentrate/coal composite pel- let was reduced at temperatures greater than 1100℃. The addition of CaCO3 improved the reduction rate when the slag basicity was less than 1.0 and inhibited the formation of the liquid phase. Mechanical milling obviously increased the metallization degree compared with that of the standard pellet when reduced under the same conditions. Evolution of the mineral phase composition and microstructure of the reduced Ti-Nb-bearing Fe concentrate/coal composite pellet at 1100~C were analyzed by X-ray diffraction and scanning electron microsco- py-energy-dispersive spectroscopy. The volume shrinkage value of the reduced Ti-Nb-bearing Fe concentrate/coal composite pellet with a basicity of 1.0 was approximately 35.2% when the pellet was reduced at 1100℃ for 20 min, which enhanced the external heat transfer to the lower layers when reduced in a practical rotary hearth furnace. The present work provides key parameters and mechanism understanding for the development of carbothermic reduction technology of a Ti-Nb-bearing Fe concentrate incorporated in a pyrometallurgical utilization flow sheet.

Research on Microwave Heating-Direct Steelmaking in Electric Furnace

Self-fluxing iron ore concentrates containing coal have good microwave Absorbability. With the voluminal heating property of microwave, the concentrates can be reduced uniformly and swiftly. The metallized semi-product can be directly charged into electric furnace for making clean steel. The total consumed energy of overall route is about 20 98 GJ.

Bulk Raw Materials Handling and Blending Techniques of Sinter Plant:A Case Study of Ajaokuta Steel Company Limited,Kogi State,Nigeria

Bulk raw materials handling plant and sintering plant preparatory plants are established to receive,blend,stockpile,prepare and supply specified grades of raw materials for smooth operations of iron making plant(Blast furnace),steel making plant(Basic oxygen converter)and lime Plant(calcinations plant).The study discusses bulk raw materials handling and some general problem of scientific analysis and documentation of basic equipment details,stockyard facilities,bulk materials transport systems and sinter processes,for the general knowledge and operational procedures of these plant for effective and efficient operational processes for optical results.Iron ore concentrate supplied from the mines to some extent fluctuate in their chemical composition as a result of the nature of the deposit with various factors controlling beneficiation processes and addition of metal-bearing materials collected as a waste product from the Rolling Mills,Blast Furnace and Sinter Plant which must be recycled through Iron ore concentrate stockyard.The part of the sinter mixture is melted at a temperature about 1300-1480°C and a sequence of reactions shaping the sinter cake to be loaded into the blast furnace to produce iron from a pig.

Comprehensive Utilization of Paigeite Ore Using Iron Nugget Making Process

The feasibility of paigeite ore treatment with iron nugget making process is proved. The isothermal reduc- tion experiments at laboratory scale were carried out, using carbon bearing pellets which were made of boron contai- ning iron concentrate and pulverized coal mainly, from 1 623 to 1 723 K with different heating time. The results indi- cated that iron nugget making process depends mainly on heating time and temperature. And the iron nugget and slag can separate in a clean manner at 1 673 K for 15 min. For the iron nugget, the C content is 3.57% （mass percent） and B is 0. 065~ （mass percent）. The B203 content of slag is 20.01~/00, and the boron was concentrated into one phase which is identified as suanite （Mg2BaOs） during the solidification. With an extraction ratio of 80~ under the atmospheric conditions, the activity of boron in slag is good. The boron-rich slag can be used to extract boric or boric acid and alleviate the shortage of boron resource. Through series of calculation and analysis related, it can be conclu- ded that the recovery ratio of Fe and boron are about 98% and 97% respectively. The results show that this method is feasible and effective on the utilization of paigeite ore.

Roasting Properties of Pellets With Iron Concentrate of Complex Mineral Composition

Investigation was conducted on roasting properties of pellets with an iron concentrate of complex mineral composition. The results indicated that the pellets of complex mineral composition concentrate required higher pre- heating temperature and longer preheating time than that of single magnetite concentrate. Therefore, it is difficult for preheated pellets to withstand the mechanical collision in the roasting process in rotary kiln. It was found that after the iron concentrate being subjected to high pressure roll grinding, the specific surface area reached 2 029. i cm2/g. Consequently, the preheating and roasting temperature of pellets were decreased by 70 and 50 ℃ and preheating and roasting time were decreased by 2 and 4 min, respectively. Meanwhile, the compression strength of preheated and roasted pellets were increased by 200 N for a pellet and 220 N for a pellet, respectively. The mechanism lied in that the increase of specific surface area activated thermal reaction and promoted formation of inter-grain bridge.

Improvement of Sinter Properties With Ultra Fine-Sized Iron Concentrate by HPRG

The experiments were conducted on the changes of sintering performance of one kind of ultra fine-sized iron concentrate with or without being processed by high pressure roll grinding （HPRG）. The experimental results indi eate that the specific surface area increases from 1723.0 to 2 201.6 cm^2/g when the iron concentrate is processed by HPRG. The permeability of sintering mix increases and the iron concentrate becomes easy to react with CaO reagent at high temperature. The effect gets intensified when iron concentrate and lime are processed together By HPRG. The further studies indicate that compared with the base case, the sinter quality also gets improved, in which the yield of sinter increases from 67.24% to 69.52% and further to 71.68%, the tumble index （TI） increases from 60.38% to 62.13% and further to 64.45%, and the productivity increases from 1.42 to 1.57 t/（m^2 · h） and further to 1.62 t/（m^2 · h） when the iron concentrate is processed by HPRG or is processed with lime together. The metallurgical properties of sinter also get improved when the iron concentrate is pretreated by high pressure roll. The results indicate that it is conducive to the increase of sinter quality and productivity when the iron concentrates are processed by HPRG.

Mechanism of Strength Improvement of Magnetite Pellet by Adding Boron-bearing Iron Concentrate

The mechanism of improving compressive strength of magnetite pellet by adding boron-bearing iron concentrate was studied. Boron-bearing iron concentrate and magnetite were mixed, pelletized and roasted under differ ent roasting conditions. Then, compressive strength of pellets was tested, and polished sections of the roasted pellets were analyzed from the perspective of mineralogy. Finally, the effects of different proportions, roasting temperatures and roasting time of boron-bearing iron concentrate on the compressive strength of magnetite pellets were investigated and explained.

Thermodynamic Analysis of Formation of Fluoride from Gangue in Bayan Obo Iron Concentrate Containing Fluorite

In order to fill up the deficiency of the theoretical basis about fluoride formation during Bayan Obo iron concentrate roasting process, the thermodynamic conditions of the interactivity between the components of the gangue and calcium fluorite were studied by means of thermodynamic calculation, DTA-TG thermal analysis and XRD characterization. The results revealed that KF, NaF and SiF4 （gaseous） could he,formed during the roasting process, and the tendency of the generation of KF is greater than that of NaF or SiF4 in standard state. Besides, the results of roasting experiments showed that the products of KCaCO3 F and KCaF3 formed in the temperature range of 800-1250 ℃and KF appears when the roasting temperature was higher than 1250 ℃ in K2O-CaF2 system. For the Na2O-CaF2 system, the product of NaF appears at temperature higher than 1050 ℃. The formation reaction of gaseous SiF4 with solid phase CaO · SiO2 in SiO2-CaF2 system took place＂only＇at temperature higher than 1 150 ℃. In the natural potash feldspar-CaF2-CaO system, the fluorination reaction products involved KF at temperature higher than 1 270 ℃ , while in the natural aegirine-CaF2-CaO system, NaF formed at terhperature higher than 980 ℃ during roasting process.

Reduction and melting separation mechanism of boron-bearing iron concentrate/coal composite pellet

Realizing the boron and iron separation through selective reduction and melting separation of boron-bearing iron con- centrate is of great significance for the utilization of crude ludwigite. The reduction and melting separation mechanism of boron-bearing iron concentrate/coal composite pellet was systematically investigated. The reduction and melting separation test of small size pellet was performed to reveal the evolution of slag and iron in the melting separation process. The isothermal reduction experiment showed the relationship between reduction stage and melting separation stage, and the step reduction and melting separation was perfectly achieved. Coal particles existed through the reduction and melting separation process and finally formed brown residue around the separated product. The pellet could not realize melting separation when the B2O3 content in the concentrate was lower than 6.00 wt%.

Ore-blending optimization for Canadian iron concentrate during iron ore sintering based on high-temperature characteristics of fines and nuclei

Canadian iron concentrate(CIC)can elevate the ferrous grade and lower the contents of gangue components and harmful elements in the sinter.To understand high-temperature characteristics of CIC and typical iron ore,the formation of the melt was calculated mainly through FactSage 7.2,and melt fluidity(MF)test for iron ore fines and penetration characteristic test of CIC melt into iron ore nuclei were carried out via micro-sintering method.The results show that hematite,calcium ferrites,dicalcium silicate,and magnetite take part in the formation of the melt in N2.The formation temperature of the liquid for CIC is higher than that for hematite/limonite ore.The MF of CIC is lower than that of hematite/limonite ore fines.The MF of hematite/limonite ore fines is dominated by the liquid amount and melt viscosity.The penetration depth(PD)of CIC melt into limonite ore nuclei is smaller than that into hematite ore nuclei.The PD is related to the reaction ability of the nuclei with the melt.Based on above results,sinter pot tests were conducted.The result shows that in the base ore blends including two hematite ores and two limonite ores,adding CIC deteriorates the sintering indexes.Increasing the proportion of high-MF and small-PD hematite ore can significantly improve the sintering indexes.10 mass%is a suit-able proportion for adding CIC in ore blends.

Central composite design for optimization and formulation of desulphurization of iron ore concentrate using atmospheric leaching process

Owing to the negative effects of sulphur in iron ore on steelmaking process and environment, a tank leaching process was performed in atmospheric conditions to remove the sulphur from the iron ore concentrate and simultaneously to transform sulphide minerals into useful by-products. To achieve desirable sulphur removal rate and efficiency, central composite design was adopted as a response surface methodology for the optimization and evaluation of the process. A full-quadratic polynomial equation between the sulphur removal and the studied parameters was established to assess the behaviour of sulphur removal as a function of the factors and to predict the results in various conditions. The optimum conditions were obtained based on the variance tests and response surface plots, from which the optimized ranges for each factor resulting in the best response （corresponding to the highest percentage of desulphurization） could be then achieved. The results show that most desirable conditions are atmospheric leaching in 1.39 mol/dm3 nitric acid and 0.88 mol/dm3 sulphuric acid for 47 h. The designed process under the optimized desulphurization conditions was applied to a real iron ore concentrate. More than 75% of the total sulphur was removed via the leaching process. In addition to the desulphurization, the conversion of sulphide-bearing minerals into useful by-products, extraction of valuable metals, and executing the process under atmospheric conditions are the other advantages of the proposed method.

Effects of embedding direct reduction followed by magnetic separation on recovering titanium and iron of beach titanomagnetite concentrate

Embedding direct reduction followed by magnetic separation was conducted to fully recover iron and titanium separately from beach titanomagnetite （TTM）. The influences of reduction conditions, such as molar ratio of C to Fe, reduction time, and reduction temperature, were studied. The results showed that the TTM concentrate was reduced to iron and iron-titanium oxides, depending on the reduction time, and the reduction sequence at 1 200℃ was suggested as follows ： Fe2.75 Ti0.25O4→Fe2TiO4→FeTiO3→FeTi2O5. The reduction temperature played a considerable role in the reduction of TTM concentrates. Increasing temperature from 1 100 to 1 200℃ was beneficial to recovering titanium and iron, whereas the results deteriorated as temperature increased further. The results of X-ray diffraction and scanning electron microscopy analyses showed that low temperature （≤1100℃） was unfavorable for the gasification of reductant, resulting in insufficient reducing atmosphere in the reduction process. The molten phase was formed at high temperatures of 1250-1 300℃, which accelerated the migration rate of metallic particles and suppressed the diffusion of reduction gas, resulting in poor reduction. The optimum conditions for reducing TTM concentrate are as follows： molar ratio of C to Fe of 1.68, reduction time of 150 min, and reduction temperature of 1 200℃. Under these conditions, direct reduction iron powder, assaying 90.28 mass% TFe and 1.73 mass% TiO2 with iron recovery of 90.85%, and titanium concentrate, assaying 46.24 mass% TiO2 with TiO2 recovery of 91.15%, were obtained.

Influence of Mechanical Activation on Acid Leaching Dephosphorization of High-phosphorus Iron Ore Concentrates

High pressure roll grinding（HPRG）and ball milling were compared to investigate the influence of mechanical activation on the acid leaching dephosphorization of a high-phosphorus iron ore concentrate,which was manufactured through magnetizing roasting-magnetic separation of high-phosphorus oolitic iron ores.The results indicated that when high-phosphorus iron ore concentrates containing 54.92 mass% iron and 0.76 mass% phosphorus were directly processed through acid leaching,iron ore concentrates containing 55.74mass%iron and 0.33mass%phosphorus with an iron recovery of 84.64%and dephosphorization of 63.79% were obtained.When high-phosphorus iron ore concentrates activated by ball milling were processed by acid leaching,iron ore concentrates containing56.03mass%iron and 0.21mass% phosphorus with an iron recovery of 85.65% and dephosphorization of 77.49%were obtained.Meanwhile,when high-phosphorus iron ore concentrates activated by HPRG were processed by acid leaching,iron ore concentrates containing 58.02mass%iron and 0.10mass% phosphorus were obtained,with the iron recovery reaching 88.42% and the dephosphorization rate reaching 88.99%.Mechanistic studies demonstrated that ball milling can reduce the particle size,demonstrating aprominent reunion phenomenon.In contrast,HPRG pretreatment contributes to the formation of more cracks within the particles and selective dissociation of iron and P bearing minerals,which can provide the favorable kinetic conditions to accelerate the solid-liquid reaction rate.As such,the crystal structure is destroyed and the surface energy of mineral particles is strengthened by mechanical activation,further strengthening the dephosphorization.

Effect of Basicity and Alumina-Silica Ratio on Formation of Silico-Ferrite of Calcium and Aluminum

Baivumebo iron ore is special magnetite containing fluorine,kalium and sodium elements,and the main raw material for ironmaking of Baotou Iron and Steel（Group） Co.The effects of basicity and ratio of Al2O3 to SiO2（A/S） on the formation of silico-ferrite of calcium and aluminium（SFCA） in Baivumebo low silica sinters were studied by means of mini-sintering,XPF-500 optical mineralogical microscope and CSS-88000 electronic universal testing machine.The results show that it is beneficial to the formation of complex calcium ferrite to enhance the basicity of Baivumebo low silica sinters.The acicular SFCA-I was increased with the enhancing basicity and reached the peak at basicity 2.8,then the columnar or platy SFCA formed and the bonding strength decreased.Alumina is beneficial to the formation of acicular complex calcium ferrite in Baivumebo low silica sinters.But the residual unfused Al2O3 reagent came into being when A/S was 0.35,while complex calcium ferrite still remained to be acicular.There is a common rule about mineralogy components affected by basicity and ratio of A/S,that is,SFCA is increasing accompanied with hematite and porosity reduced,but the content of glass phase is stable