Some basic properties of granules from ore blends consisting of ultrafine magnetite and hematite ores

Some basic properties of granules,including the granule size distribution,packed-bed permeability,and chemical composition of the adhering layer,were investigated in this study for four iron ore blends consisting of 5wt%,25wt%,and 45wt%ultrafine magnetite and 25wt%ultrafine hematite concentrates.The effects of varying the sinter basicity(CaO/SiO2 mass ratio=1.4 to 2.2)and adding ultrafine concentrates on the variation of the adhering-layer composition and granule microstructure were studied.Moreover,the effect of adhering-layer compositional changes on sintering reactions was discussed in combination with pot sintering results of ore blends.Increasing sinter basicity led to an increase in the basicities of both the adhering layer and the fine part of the sinter mix,which were higher than the overall sinter basicity.When the sinter chemistry was fixed and fine Si-bearing materials(e.g.,quartz sand)were used,increasing the amount of ultrafine ores in the ore blends tended to reduce the adhering-layer basicity and increase the SiO2 content in both the adhering layer and the fine part of the sinter mix,which will induce the formation of low-strength bonding phases and the deterioration of sinter strength.The adhering-layer composition in granules can be estimated in advance from the compositions of the-1 mm fractions of the raw materials.

Upgrading and dephosphorization of Western Australian iron ore using reduction roasting by adding sodium carbonate

The technology of direct reduction by adding sodium carbonate （Na2CO3） and magnetic separation was developed to treat Western Australian high phosphorus iron ore. The iron ore and reduced product were investigated by optical microscopy and scanning electron microscopy. It is found that phosphorus exists within limonite in the form of solid solution, which cannot be removed through traditional ways. During reduction roasting, Na2CO3 reacts with gangue minerals （SiO2 and A1203）, forming aluminum silicate-containing phosphorus and damaging the ore structure, which promotes the separation between iron and phosphorus during magnetic separation. Meanwhile, Na2CO3 also improves the growth of iron grains, increasing the iron grade and iron recovery. The iron concentrate, assaying 94.12wt% Fe and 0.07wt% P at the iron recovery of 96.83% and the dephosphorization rate of 74.08%, is obtained under the optimum conditions. The final product （metal iron powder） after briquetting can be used as the burden for steelmaking by an alactrie a.re furnace to rer）la,ce scrar） steel.

Improving the sintering performance of blends containing Canadian specularite concentrate by modifying the binding medium

Canadian specularite concentrate（CSC） possesses high total iron grade and low impurity content. However, due to the poor granulating performance and weak reactivity of CSC at high temperature, the proportion of CSC used in sintering blends is restricted. In this research, the effects of fine limonite, slake lime, and bentonite particles on the granulation performance of blends containing a high ratio of CSC were studied through granulation test. Based on the test results, the effects of modification of the binding medium on the sintering performance of blends containing a high ratio of CSC were revealed by the sintering pot test. Both the granulation property and sintering performance of blends with a high proportion of CSC were improved by modifying the binding medium.

A novel process for Fe recovery and Zn, Pb removal from a low-grade pyrite cinder with high Zn and Pb contents

Comprehensive utilization of pyrite cinders is increasingly important because of their huge annual outputs and potential valuable metals recovery to cope with the gradual depletion of high-grade mineral resources. In this work, a new process, i.e., a high-temperature chlorination–magnetizing roasting–magnetic separation process, was proposed for recovering Fe and removing Zn, Pb from a low-grade pyrite cinder containing 49.90 wt% Fe, 1.23 wt% Zn, and 0.29 wt% Pb. Various parameters, including the chlorinating conditions(dosage of Ca Cl2, temperature, and time) and the magnetization roasting conditions(amount of coal, temperature, and time) were investigated. The results indicate that the proposed process is effective for Fe recovery and Zn, Pb removal from the pyrite cinder. Through this process, 97.06% Zn, 96.82% Pb, and approximately 90% S can be removed, and 89.74% Fe is recovered as magnetite into the final product under optimal conditions. A purified magnetite concentrate containing 63.07 wt% Fe, 0.16 wt% P, 0.26 wt% S, and trace amounts of nonferrous metals(0.005 wt% Cu, 0.013 wt% Pb, and 0.051 wt% Zn) was obtained. The concentrate can be potentially used as a high-quality feed material for producing oxidized pellets by blending with other high-grade iron ore concentrates.

Grate-kiln pelletization of Indian hematite fines and its industrial practice

Indian hematite fines normally have a high iron grade and minor impurities; they are usually used as sinter fines for feeding into a blast furnace. In this work, the grindability properties of two kinds of Indian hematite fines and the roasting behaviors and induration characteristics of pellets made from these fines were revealed through experiments involving dry ball milling and small-scale and pilot-scale tests. In addition, the microstructures of the particles of ground India hematite fines and fired pellets were investigated using optical microscopy. On the basis of the results, a grate-kiln production line with an annual output of 1.2 Mt of oxidized pellets was established in India. This pellet plant operates stably and reliably, further confirming that preparing high-quality pellets with Indian hematite fines pretreated by dry ball milling is an industrially feasible process. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Effect of alumina occurrence form on metallurgical properties of hematite and magnetite pellets

The effect of alumina occurrence form on the metallurgical properties of both hematite and magnetite pellets was investigated at the same Al_(2)O level of 2 wt.%,including reduction index(RI),low-temperature reduction disintegration index(RDI),reduction swelling index(RSI),and high-temperature softening-dripping performance.The mineralogy of fired pellets was also studied to reveal the influence of alumina occurrence form on the phase composition and microstructure.From the results,the alumina occurrence form presents tremendous impacts on the metallurgical perfor-mance of both magnetite and hematite pellets.Addition of all alumina occurrence forms contributes to inferior reducibility of pellets,especially in the case of gibbsite for magnetite pellets with a RI of 58.4%and kaolinite for hematite pellets with a RI of 56.8%.However,addition of all alumina occurrence forms improves the RDI of magnetite pellets,while there is no significant difference among various alumina occurrence forms.In contrast,alumina occurrence forms have little influence on the RDI of hematite pellets.The presence of free alumina,gibbsite,and kaolinite tends to improve the RSI of hematite and magnetite pellets,whereas hercynite gives the opposite trend with a RSI of 25.6%.For softening-dripping performance of magnetite pellets,all alumina occurrence forms contribute to narrower softening-melting interval.Meanwhile,alumina,gibbsite,and kaolinite give narrower softening-dripping interval,at 229,217,and 88℃,respectively,whereas addition of hercynite results in the largest melting range at 276℃ due to its high melting point.Regarding hematite pellets,free alumina,gibbsite,and hercynite tend to enlarge melting range,whereas kaolinite contributes to lower dripping temperature of 1148℃ and narrow softening-dripping interval of 88℃ due to the formation of a greater amount of slag phase at high temperatures.

Effective utilization of dolomitic lead-zinc waste rock by replacing dolomite as flux in iron ore sintering process

With increasingly stringent environmental protection policies,cost-effective and value-added treatment of massive lead-zinc waste rock(LZWR)generated from the preconcentration process has attracted substantial attention.A type of dolomitic LZWR with 18 wt.%MgO,27 wt.%CaO,0.29 wt.%Zn and 1.43 wt.%S was used as a replacement flux in the iron ore sintering process.Traditional sinter pot tests were carried out based on an industrial ore blend.The results show that replacing 0%-60%of dolomite with LZWR does not adversely affect the sintering productivity,fuel consumption rate,and the quality of the sinter products,while the Zn and S elements contained in LZWR can be effectively removed with the residual Zn and S contents of the resultant sinter products being less than 0.02 and 0.055 wt.%,respectively.However,substituting LZWR for dolomite as a flux inevitably increases the SO_(2) concentration in the sintering flue gas due to its high sulfur content.Considering the processing capacity of the sintering flue gas desulfurization system,the replacement ratio of dolomite can reach 40%,equal to LZWR consumption of 24.3 kg per ton of sinter.The SO_(2) in sintering flue gas can be recovered to produce(NH_(4))_(2)SO_(4) or HSO_(4),while the volatilized Zn collected into the zinc-containing dust can be subsequently recycled by the rotary hearth furnace process.Therefore,it is technologically and economically feasible to use the LZWR as a replacement flux in the iron ore sintering process,providing a new way for the safe,large-scale and low-cost treatment of LZWR.

Preparation of sinter with low reduction degradation index for COREX reduction in a high proportion

The sinter with low reduction degradation index(RDI)for COREX reduction was prepared by separated granulation sintering process.The results illustrate that the productivity and tumble index are attained to be 1.64 t m^(-2)h^(-1)and 59.25%,respectively,in pot tests under the optimal conditions.Under the reducing condition simulating COREX shaft furnace,RDI_(+6.3 mm),RDI_(+3.15 mm),and reducibility index of the sinter reach 63.05%,81.52%,and 83.65%,respectively.Compared with traditional sintering process,the productivity rose by 14.69%,and RDI_(+6.3) mm and RDI_(+3.15) mm were increased by 157.54%and 32.70%,respectively.In addition,as the proportion of sinter reached 60%,RDI_(+6.3 mm)and RDI_(+3.15 mm)of comprehensive burden were achieved to be 73.39%and 84.28%,respectively,which could completely meet the requirement of COREX shaft furnace for RDI.The mechanism was demonstrated that the more silicoferrites of calcium and aluminum and silicate phase occurred as well as magnetite,and the amount of Fe_(2)O_(3)decreased substantially in the sinter by separated granulation sintering process.Hence,the low-temperature reducing stress is restrained,with the increase in sinter strength.

Difference of sintering performance of different types of limonitic nickel laterite

To achieve the more extensive utilization of limonitic nickel laterite,the difference of sintering performance of different types of limonitic nickel laterite including high-gangue and low-gangue nickel ores was investigated by sinter pot tests and relevant mechanism analyses such as thermodynamic analysis and the chemistry and mineralogy of product sinter.With the type of limonitic nickel laterite transformed from high-gangue to low-gangue nickel ore,tumble index and productivity are improved from 45.87%and 0.97 t m^(-2) h^(-1) to 50.16%and 1.05 t m^(-2) h^(-1),respectively,and solid fuel rate is reduced from 140.52 to 131.13 kg/t,indicating that the low-gangue nickel ore possesses relatively better sintering performance.This is mainly due to the fact that the much lower contents of MgO and Al2O3 improve the formation ability and fluidity of liquid phase,which eventually contributes to the formation of relatively tighter sinter microstructure with the lower sinter porosity,more silico-ferrite of calcium and alumina amount and better bonding of hercynite by liquid phases.In addition,the metallurgical performance and nickel content of product sinter would not be reduced as different types of limonitic nickel laterite are blended for sintering.On this basis,it is entirely feasible to more widely utilize limonitic nickel laterite and simultaneously obtain much better-quality Ni-containing product sinter via effective sintering strengthening technologies.

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.

Pyrometallurgical recycling of stainless steel pickling sludge: a review

Stainless steel pickling sludge (SSPS), generated from the lime neutralization process of spent pickling liquor, is classified as a hazardous waste consisting of abundant metals like Fe, Cr and Ni, and other elements like F, S and Na, etc. Rather than a common disposal in landfill, recovering these metals and other valuable components from SSPS can not only create economic benefits, but also eliminate its adverse impacts on human health and the environment. A review of the formation mechanism and basic properties of SSPS was made, and the technical features, advantages and limitations of a series of pyrometallurgical treatment processes were summarized. Based on these, the main challenges for recycling of SSPS through the existing techniques are demonstrated. The traditional pelletizing/sintering-blast furnace process can only be used as a partial solution. Direct use of SSPS as flux in an argon-oxygen decarburization converter or electric arc furnace is a promising way, but low S sludges are preferred. The STAR process shows excellent recovery for metals, but it also has a low tolerance to the S and F contents in SSPS. And theINMETCO process is highly flexible in treatment of various wastes, whereas it exhibits relatively low Cr recovery and produces poor-quality pig iron. In addition, the feasibility of the rotary kiln-electric furnace, solid -state reduction of chromite and reduction-magnetic separation processes requires further studies. An urgent task at present is to develop a system for scientific classification and separate collection of SSPS in terms of chemical composition, notably S and F contents.

Improving roasting performance and consolidation of pellets made of ultrafine and super high grade magnetite concentrates by modifying basicity

For improving the strength of pellets made of ultrafine and super-high-grade magnetite concentrates,the influence of basicity(CaO/SiO2 ratio)on the roasting and consolidation of pellets was investigated.The results showed that with the basicity of pellets increasing from 0.09 to 0.60,the compressive strength of both preheated and roasted pellets achieved an evident improvement from 502 and 2519 to 549 and 3096 N/pellet,respectively;meanwhile,the roasting time decreased from 15 to 9.min.The low-viscosity liquid phases were easily generated in fired pellets at the basicity range of 0.40-0.60 under the roasting temperature of 1240℃,filled the voids between hematite particles and tightened the bonding among particles,effectively restraining the generation of concentric cracks and decreasing the porosity of fired pellets;low-viscosity liquid phases facilitated the solid diffusion of hematite,leading to the formation of coarse hematite crystals and thicker connecting necks.

Comparison of sintering performance of typical specular hematite ores with distinct size distributions

The sintering performance of three typical specular hematite ores（coarse SO-A,intermediate SO-B and ultrafine SO-C）was compared in an industrial ore blend through pilot-scale sinter pot tests.The effect of particle size of specular hematite ores on their granulation and sintering performance was revealed.Compared with the coarse SO-A fine and ultrafine SO-C concentrate,the intermediate SO-B showed inferior granulation and sintering performance characterized with poorer bed permeability and productivity,lower sinter strength and higher fuel rates.A new material preparation method was hence proposed and verified at both pilot and industrial scales.The proposed method by mixing SO-B with a high amount of goethitetype iron ore fines was found to be an effective way in improving the granulation and assimilative characteristics of ore blend comprising 31%intermediate SO-B,leading to improved sinter productivity and lowered fuel rates.The metallurgical properties and microstructure of sinters were also investigated.The sinters obtained through the proposed preparation method were generally stronger and more reducible on account of better sinter structure with more relict hematite ultimately connected with needle-like silico-ferrite of calcium and aluminum and lower porosity.

Synthesis,characterization and properties of organically compounded bentonite by molecular intercalation process

A new process for manufacturing organically compounded bentonite was devcloped successfully based on the organic intercalation andlayered structure of bentonitc.The main steps in the proposed process included wet sodium activation of bentonite ore,organic com-pounding and high-pressure roll grinding.The optimum procedure is recommended as follows:5 mass%of sodium carbonate powderand 30 wt.%water are added to activate the bentonite ore for 24 h to prepare activated bentonice;0.5 wt.%of organic molecules are adiedinto the activated bentonite for organic compounding for 12 h:then,the high-pressure rollgrinding is followed to treat the organicallycompounded bentonice;:and finally,drying and fine prinding are performed for prenaring the final organically compounded bentoniteprodiuct with 10 wt.%moisture and 98% passing 0.074 mm.The obtained organically compounded bentonite was characterized usingan X-ray diffractometer,a scanning electron microscope and anX-ray photoelectron spectrometer.To confirm the effect of organicallycompounded bentonite on green balls,the pelletizing tests were carried out.The rexsults showed that high-pressure roll grinding can notonly enhance the ability of the crystal layer to hold the combined water.but also strengthen the intercalation compounding of the organicadditive,which is beneficial for the formation of a fiber-interlaced structure of the organically compounded bentonite and improvesthe quality index of the bentonite itself.Also,the organically compounded bentonite is helpiul to improve the indexes of green balls.

Upgrade of nickel and iron from low-grade nickel laterite by improving direct reduction-magnetic separation process

Low-grade saprolite nickel laterite,characterized by complicated minerals composition and fine-grained and complex dissemination,was commonly treated with a low recovery efficiency of Ni and Fe by conventional methods.Hence,an improved direct reduction and magnetic separation process was proposed.Meanwhile,the mechanisms on the enhanced growth of the Ni-Fe particles and the phase transformation in the nickel laterite pellets were explored.The low-nickel concentrates as a nucleating agent can obviously decrease the activation energy for growth of Ni-Fe alloy particles during the improved direct reduction process from 197.10 to 154.81 kJ/mol when the low-nickel concentrates were added from 0 to 20%.Hence,it is able to decrease nucleation barrier,induce the growth of Fe-Ni alloy particles and increase their average size.As a result,the size of Ni-Fe particles in the pellets from less than 10 lm grew to more than 20 lm,which is beneficial for the full liberation and recovery of Ni and Fe in subsequent magnetic separation process.Therefore,the preferable Ni-Fe alloy concentrates with 6.44%Ni and 82.48%Fe can be prepared with corresponding recovery rates of 96.90%and 95.92%,respectively,when adding 20%low-nickel concentrates.

Influence of basicity on metallurgical performances of fired super high-grade magnetite pellets in hydrogen-rich gases

The influence of basicity on the metallurgical performances and reduction characteristics of fired super high-grade magnetite pellets under the simulated shaft furnace gas conditions was investigated.The fired pellets in the basicity range of 0.09(natural basicity)to 1.00 show superior reducibility and low-temperature disintegration performance.However,in the basicity range of 0.20–0.80,the abnormal swelling of the fired pellets occurs.Improving basicity from 0.09 to 0.40 promotes the generation of low melting point slag phases and lower porosity of fired pellets,and accelerates the growth and densification of hematite crystals,impeding the reduction of hematite particles and the formation of metallic iron shell.In addition,the slags that distribute between the hematite particles absorb the reduction stresses by increased distances between the particles during the reduction process,which leads to the large reduction swelling of pellets.

Achieving efficient utilization of limonitic nickel laterite and CO_(2) emission reduction through multi-force field sintering process

Strengthening limonitic nickel laterite sintering and reducing CO_(2) emission were performed by the application of multiforce fields including external thermodynamic and pressure fields.Sinter pot tests of limonitic nickel laterite were carried out,and the relevant industrial production was briefed.The chemistry and mineralogy of product sinter and the thermodynamic and kinetic conditions during sintering were analyzed to reveal the relevant mechanism.The results indicate that sintering performance of limonitic nickel laterite in the new sintering process with multi-force fields is significantly improved with tumble index and productivity increased by 24.11%and 18.56%,respectively,and solid fuel rate reduced by 23.21%,compared with those in traditional sintering process.In this case,greenhouse and pollutant gas emissions are greatly reduced,and metallurgical performances of product sinter are excellent.The industrial production has been successfully conducted,indicating a bright application prospect.Mechanism analysis shows that the great improvement of thermodynamic and kinetic conditions during sintering and the densification of loose sinter can be achieved via the application of multi-force fields.Sinter microstructure is transformed from large thin-wall pores to small thin-wall pores or medium thick-wall pores with the dramatic reduction of sinter porosity and more formation of silico-ferrite of calcium and alumina(SFCA).Meanwhile,the homogenization of mineral compositions is achieved,and much denser interlocking texture between hercynite and SFCA is formed.The application of multi-force fields contributes to the substantial improvement of sintering performance of limonitic nickel laterite and CO_(2) emission reduction.

Neoadjuvant Chemoradiotherapy Improving Survival Outcomes for Esophageal Carcinoma： An Updated Meta-analysis

Background： The effectiveness of neoadjuvant chemoradiotherapy （NCRT） treatment for patients with esophageal carcinoma （EC） remains controversial. The aim of this study was to compare the effect of NCRT followed by surgery （NCRTS） with surgery alone （SA） for EC. Methods： The PubMed, EMBASE, and the Cochrane Library databases were electronically searched up to August 2015 for all the published studies that investigated EC patients receiving either NCRTS or SA, and the reference lists were also manually examined for the eligible studies. The risk ratio （RR） with 95% confidence intervals （CI s） as effective size was determined to assess the 1-, 3-, 5-year survival rates （SRs）, postoperative morbidity, and postoperative mortality. Heterogeneity was determined using the Q-test. The Begg＇s test and Egger＇s test were used for assessing any potential publication bias. Results： Of 1120 identified studies, 16 eligible studies were included in this analysis （involving 2549 patients）. Overall, the pooled results suggested that NCRTS was associated with significantly improved 1-year （RR： 1.07, 95% CI： 1.02–1.13）, 3-year （RR： 1.26, 95% CI： 1.14–1.39）, and 5-year （RR： 1.36, 95% CI： 1.18–1.56） SRs. However, the results also indicated that NCRTS had no or little effect on postoperative morbidity （RR： 0.93, 95% CI： 0.82–1.05） and postoperative mortality （RR： 1.17, 95% CI： 0.56–2.44）. Conclusions： Compared with SA, NCRTS can increase 1-, 3-, and 5-year SRs in patients with EC.

Insights on pretreatment of Indian hematite fines in grate-kiln pelletizing process： the choice of grinding processes

Indian hematite fines are normally characterized by high iron grade and minor impurities, which are usually used for sinter fines. With macroscale operations technology of blast furnace in Indian, pellets, as a kind of high-quality materials, attract more and more attention. However, the hematite fines possess the coarse size. Hence, they inevitably need to be further finely ground for pelletizing before balling. The grinding behavior of Indian hematite fines was revealed by conducting the ball milling tests and determining the Bond ball mill work index （Wi）. The results show that Indian hematite fines have an excellent grindability with Wi of only 7.40-7.73 kWh/t, indicating that ball milling is an economically viable way to pretreat Indian hematite fines. Nonetheless, due to poor sedimentation and filtering properties of wet ground products, the dry ball milling is more appropriate to process Indian hematite fines. In addition, the superior quality green balls can be manufactured with dry ground products under the conditions of 0.5% bentonite dosage, 7.5% moisture and balling for 12 min, which further confirmed that the recommended pellet feed preparation technique is reasonable.