Effects and mechanisms of fluorite on the co-reduction of blast furnace dust and seaside titanomagnetite

The co-reduction roasting and grinding-magnetic separation of seaside titanomagnetite and blast furnace dust was investigated with and without fluorite addition at a reduction roasting temperature of 1250°C for 60 min, a grinding fineness of-43 μm accounting for 69.02 wt% of the total, and a low-intensity magnetic field strength of 151 kA/m. The mineral composition, microstructure, and state of the roasted products were analyzed, and the concentrations of CO and CO_2 were analyzed in the co-reduction roasting. Better results were achieved with a small fluorite dosage(≤4 wt%) in the process of co-reduction. In addition, F^- was found to reduce the melting point and viscosity of the slag phase because of the high content of aluminate and silicate minerals in the blast furnace dust. The low moisture content of the blast furnace dust and calcic minerals inhibited the hydrolysis of CaF_2 and the loss of F^-. Compared with the blast furnace dust from Chengdeng, the blast furnace dusts from Jiugang and Jinxin inhibited the diffusion of F-when used as reducing agents, leading to weaker effects of fluorite.

INFLUENCE OF MnO ON REDUCTION OF TiO_2 IN BLAST FURNACE TYPE SLAG

A study was carried out on the formation of Ti(C,N) during smelting vanadium-bearing titanomagnetite in blast furnace and the influence of MnO content on reduction of TiO_2 in the slag containing high titania. The reduction of TiO_2 is restricted by MnOpredominantly at the slag-metal interface and no more at the slag-coke one. The formation of Ti(C,N) is remarkably restricted by MnO in the slag when the MnO content is about 4% and the basicity from 0.6 to 1.2 in the slag. MnO may also retards the reduction of SiO_2 and accelerates the desulphidation under certain condition.

Reduction and Reoxidation of Silicon in Blast Furnace Hearth

This paper introduces both laboratory experi- ment and equilibrium calculations concerned with the Si reduction and reoxidation.The results give evidence that the Si transport in different directions just exists in the furnace hearth synchronistically, by which the desulphurization is also affected.The problems noticed for smelting tow Si pig iron are given.

Reduction Mechanism of Chromite Ore in Blast Furnace

The structural changes and reduction degree of chromite ore in blast furnace were studied by optical micrograph analysis,scanning electron microscope(SEM)and energy dispersive X-ray analysis(EDXA).The smelting reduction mechanism of chromite in blast furnace was primarily discussed.

Effect of nut coke on the reduction behavior in iron-making blast furnace

Ore-coke mixed charging is a potential technique for optimizing the charging pattern. Recently, the charging of small-sized coke（ nut coke） with the ferrous burden layer has been applied to reduce raw material usage and decrease costs. Various studies indicate that mixing nut coke with ferrous burden can enhance the reduction kinetics,improve the softening and melting properties, and have a positive effect on the permeability. Although mixed charging, especially the addition of nut coke to the burden layer, has been used in the industry for various reasons ,the mechanisms and side effects for using nut coke are not well understood, and the mixing ratio remains limited in actual blast furnace operation. High-temperature experimental studies were conducted to increase the understanding of the complex process of reduction, softening and melting properties, and permeability in a blast furnace when mixing nut coke with an ore layer. The effect of the nut coke mixing ratio and nut coke size was investigated under various reducing conditions. To describe the reduction processes of burden materials, numerous experiments were interrupted at different stages of the reduction, and the collected materials were examined by using image analysis. The reduction degree of mixed charging（iron ore mixing with nut coke） was improved when using nut coke at the temperatures of 800 ℃ and above. The reaction rate of ore-nut coke mixed charging was higher than that of standard charging without the use of nut coke.

Reduction Characteristics of High Phosphorus Iron Ore in Reducing Parameters Similar to Blast Furnace Conditions

The strong global demand for iron and steel has necessitated the utilization of various low grade iron ores, which are not suitable for direct utilization in ironmaking processes. The low grade iron ores cannot be dressed effectively using the traditional mineral processing methods because of complicated min-eral compositions. The main problem associated with exploiting these deposits is the dissemination of fine silicate minerals and the high level of phosphorus content due to the poor liberation of iron minerals from the gangues. The pre-sent manuscript is aimed to investigate reduction properties of iron ores rich in phosphorous in order to study the suitability of using these ores in iron blast furnace. Representative technological samples of iron ore are collected from Eastern South Aswan iron ore mine in Egypt. The principal gangue contents are SiO2 7.76%, and P2O5 1.13%. Iron and phosphorus exist in the form of hematite 78% and apatite respectively. The ore was fired at 1000°C for 3 hours. The green and fired samples were isothermally reduced at conditions which closely represent the theoretical reduction conditions in different zones of blast furnace. The influence of reduction conditions on the reduction behaviour and the morphology of the reduced samples were investigated. After reduction apatite is changed to Calcium phosphate beside fayalite and quartz. The reduction rate of fired samples is greater than that for the green ones and that was confirmed by morphological examination. At cohesive zone condition, the effect of firing on reduction characteristics cannot be distinguished.

Preparation,characterization and photocatalytic activity of sulfuric acid-modified titanium-bearing blast furnace slag

The feasibility of reducing Cr(VI)from the aqueous solution by sulfuric acid-modified titanium-bearing blast furnace slag(SATBBFS)as a photocatalyst was investigated.The photocatalysts were examined by X-ray diffraction(XRD),UV-vis diffuse reflectance spectra,thermogravimetric analysis(TG)and Fourier transform infrared spectroscopy(FTIR).The photocatalytic activities of the different catalysts were evaluated by the photocatalytic reduction of Cr(VI)under UV-vis light irradiation.The results show that the photocatalytic activities of SATBBFS catalysts are strongly dependent on CaTiO3-to-TiO2 mass ratio,adsorption capacity and surface acidity,and SATBBFS calcined at 400°C shows a higher photocatalytic activity compared with other catalysts.

Gas-solid reduction kinetic model of MgO-fluxed pellets

The reduction process of MgO-fluxed pellets was investigated and compared with traditional acidic pellets in this paper. Based on the piston flow concept and experimental data, a kinetic model fitting for the gas-solid phase reduction of pellets in tubular reactors （blast furnace, BF） was built up, and the equations of reduction reaction rate were given for pellets. A series of reduction experiments of pellets were carried out to verify the model. As a result, the experimental data and calculated result were fitted well. Therefore, this model can well describe the gas-solid phase reduction process and calculate the reduction reaction rate of pellets. Besides, it can give a better explanation that the reduction reaction rate （reducibility） of MgO-fluxed pellets is better than that of traditional acidic pellets in BF.

Influence of hydrogen-enriched atmosphere under coke oven gas injection on reduction swelling behaviors of oxidized pellet

It is of great importance to elucidate reduction swelling behaviors and reaction mechanism of oxidized pellet in hydrogen-enriched atmosphere under coke oven gas injection. In this work, the effects of hydrogen concentration in N_2-CO-H_2 atmosphere with unchanged CO content on reduction swelling behaviors of oxidized pellet at 1173 K were studied, to clarify the mechanism of hydrogen-enriched reduction and exclude the influences of CO. Then, the reduction swelling behaviors of oxidized pellet at 1173 K in actual atmosphere under coke oven gas(COG) injection, got from the simulation results of multi-fluid blast furnace model, were investigated. The results show that with the concentration of hydrogen increasing in N_2-CO-H_2 gas from 2% to 18%, the reduction swelling index of pellet decreases from 10.12% to 5.57% while the reduction ratio of pellet increases obviously from 39.85% to 69.58%. In addition, with COG injection rate increasing from 0 to 152.34 m^3/t, the reduction swelling index of pellet decreases slightly from 10.71% to 9.54% while the reduction ratio of pellet is increased from 31.57% to 36.39%. The microstructures of pellet are transformed from the platy structure to the flocculent structure.

CLEAN PRODUCTION AND SMELTING REDUCTION TECHNOLOGY

Clean Production is the best method for iron-steel making industry to eliminate pollution thoroughly. In order to achieve this object, smelting reduction technology should play the key role. Furthermore, process integration method can be used to solve the problem of residual gas utilization by integrating smelting reduction process with direct reduced iron unit, gasoline, methanol or dimethyl ether synthesis unit, etc. A new smelting reduction process has been proposed which can be constructed on the present plant site. Since this process can directly treat the lump coal and iron ore fines, it reduces st6ps necessary in traditional blast furnace process and Corex smelting reduction process.

Reduction of Panzhihua titanium-bearing oxidized pellets by CO-N_2-H_2 gas

The effect of H_2 gas content on the reduction of Panzhihua titanomagnetite concentrate pellets by carbon monoxide was investigated by isothermal reduction experiment using CO-N_2-H_2 gas mixtures in a vertical electric resistance furnace.The morphology and phase transformation of reduced samples obtained were detected by scanning electron microscopy,energy disperse spectroscopy analysis and X-ray diffractometry respectively.The results show that increasing H_2 content will enhance the initial stage of reduction rate apparently.There are two reasons responsible for this effect,one is that H_2 accelerates the chemical reaction,and the other is that the addition of H_2 gas can improve the porosity of pellet intensively.It is noteworthy that this effect is more obvious when the reduction temperature reaches 1473 K with sticking phenomenon happening.There are no crystalline phases which can be found such as ulvospinle,ilmenite,ferrous-pseudobrookite and any titanium oxide except titanomagnetite(TTM).The reduction progress is suggested as follows:1) Fe_2O_3→Fe_3O_4→FeO→Fe;2) Fe_2TiO_5→Fe_2TiO_4+Fe_3O_4→TTM.Element Al migrates and gets enriched in high titanium content iron ores,and eventually Al to Ti molar ratio is 1:3.Al is likely to dissolve in titanium iron oxides to form a kind of composite iron compound,which results in the restrain of reduction.

Reduction Behavior of Sinter Based on Top Gas Recycling-Oxygen Blast Furnace

In order to explore the behavior laws of sinter reduction in TGR-OBF ( top gas recycling-oxygen blast furnace ), reduction experiments of sinter have been conducted by thermal balance mass loss method with different atmospheres , temperatures and volume flows.The changes of RI ( reduction degree of Fe 2 O 3 ), RI′ ( reduction rate of Fe 2 O 3 ) and r ( reduction degree of FeO ) have been examined.The results show that the reduction of sinter was significantly improved under TGR-OBF atmosphere , and the RIand r were measured up to 98.2%and 97.8%at 900℃ respectively.With increasing of the reduction temperature , the reduction of sinter speeded up greatly , and the reduction time-duration shortened from 117min at 900 ℃ to 63min at 1 100 ℃.Moreover , the reduction of sinter enhanced with increasing of the reductive gas flow.When the flow increased from 10to 15L / min , the initial reduction rate of sinter increased from 2.47% / min to 3.73% / min.While increasing H2and CO contents in the reductive atmosphere , the reduction of sinter was promoted.Besides , H 2 influenced more evidently than CO to the reduction of sinter , especially in the later stage of the reduction process , for instance , the reduction of wustite will be improved enormously when increasing the H2content in the reductive atmosphere.

Reduction Behavior of Pellet under Simulated Oxygen Blast Furnace Condition

The reduction behavior of pellet was researched through the programming apparatus under simulated con- ditions of oxygen blast furnace （OBF） and traditional blast furnace （T-BF）. The results indicated that compared with traditional blast furnace, the reduction starting temperature of pellet decreased by 60 ℃ under oxygen blast furnace condition. The reduction degree of pellet could almost reach 100% under oxygen blast furnace condition when the temperature reached 1100 ℃, whereas it was only 82.49% in traditional blast furnace. The content of carbon in pel- let of oxygen blast furnace was about 5 times more than that of traditional blast furnace. In addition, the microstruc- ture at the periphery and core of pellets after reaction was characterized by means of SEM and EDS.

Non-isothermal reduction process analysis of iron-bearing burden with charging iron coke hot briquette under simulated blast furnace conditions

Highly reactive iron coke hot briquette(ICHB)prepared by carbonizing the agglomerate of iron-bearing substance and blended coals is regarded as an alternative fuel to mitigate carbon emission and energy consumption of blast furnace.Simultaneously,the reduction process of iron-bearing burden is extremely crucial for blast furnace smelting.The effects of ICHB on the non-isothermal reduction process of iron-bearing burden with different reduction properties were thus experimentally studied under the conditions of simulated blast furnace lump zone(below 1100°C),and the related mechanism was discussed and analyzed.The results showed that the non-isothermal reduction process of iron-bearing burden is promoted by adding ICHB.As the charging ratio of ICHB is increased from 0%to 30%,the reduction degree of pellet is increased from 22.91%to 36.62%,but the increased amplitude is leveled off.Furthermore,the reduction degree of sinter is raised from 35.10%to 93.33%.It is also indicated that the promotion effect of ICHB on the non-isothermal reduction of iron-bearing burden depends on the reduction property of burden.Compared with the burden with poor reduction performance(such as pellet 1),the promotion is more significant for the burden with good reduction property(such as sinter 1)since the reduction reaction of iron oxide in iron-bearing burden and the gasification of carbon in ICHB are remarkably reinforced each other.The practical application of ICHB in blast furnace should be utilized with highly reductive iron-bearing burden.

Thermodynamic and experimental study of high-temperature roasting of blast furnace gas ash for recovery of metallic zinc and iron

A high-temperature reduction roasting method was used to achieve metallic iron and zinc recovery from blast furnace gas ash(BFA).The reduction processes for Zn-containing and Fe-containing oxides were analyzed in detail by using ther-modynamic equilibrium calculation and the principle of minimum free energy.The results showed that the main reaction in the system is the reduction of ZnFe_(2)_(4)and iron oxides.Over the full temperature range,iron oxides were more easily reduced than zinc oxides.Regardless of the amount of CO contained in the system,the reduction of ZnO to Zn was difficult to proceed below the boiling point(906℃)of Zn.When the reduction temperature is below 906℃,the reduction process of zinc ferrate was ZnFe_(2)_(4)→ZnO;when the reduction temperature is above 906℃,its reduction process becomed ZnFe_(2)_(4)→ZnO→Zn(g).The metallization and dezincification rates of the BFA gradually increased with increasing reaction temperature.As the C/O ratio increased,the metallization and dezincification rates first increased and then decreased.The effect of reduction time on BFA reduction was similar to that of reaction temperature.

Physicochemical principles of hydrogen metallurgy in blast furnace

Based on the stoichiometric method and the free energy minimization method,an ideal model for the reduction of iron oxides by carbon and hydrogen under blast furnace conditions was established,and the reduction efficiency and theoretical energy consumption of the all-carbon blast furnace and the hydrogen-rich blast furnace were compared.The results show that after the reduction reaction is completed at the bottom of the blast furnace,the gas produced by reduction at 1600℃still has a certain excessive reduction capacity,which is due to the hydrogen brought in by the hydrogen-rich blast as well as the excess carbon monoxide generated by the reaction of the coke and the oxygen brought in by the blast.During the process of the gas with excessive reduction capacity rising from the bottom of the blast furnace and gas reduction process,the excessive reduction capacity of the gas gradually decreases with the increase in the dydrogen content in the blast.In the all-carbon blast furnace,the excess gas reduction capacity is the strongest,and the total energy consumption per ton of iron reduction is the lowest.This shows that,for the current operation mode of the blast furnace,adding hydrogen in the blast furnace cannot reduce the consumption of carbon required for reduction per ton of iron,but rather increases the consumption of carbon.

Bio-PCI a renewable reductant for iron production—where can it flourish?

Presently the iron and steel makers are compelled to incorporate rational initiatives to reduce its processing CO_2 total emissions.In the medium and long term,the injection of small particles of biochar through the tuyerees in blast furnaces,here called Bio-PCI,offers attractive features from the environmental and metallurgical point of view,as it is a renewable carbon neutral reductant and presents lesser impurities than coke.However,its utilization in iron plants is been hindered by the traditional large availability of relatively economical coal and coke.As the cost of the principal processing inputs increases(coal,coke and iron ore) the gap between fossil and renewable reductants decreases.In this sense,our contribution aims to complement the metallurgical inquiry of technical feasibility with a strategic identification of the areas with best prospects to benefits from the incorporation of Bio-PCI:where can it flourish?.Our analysis leads to indicate that emerging countries in specific,China,Brazil and India,are in a prime position to incorporate the Bio-PCI as they simultaneously comply with a growing iron industry based on blast furnaces,and possess an important potential for energy generation from forestry residues.

碳中和背景下我国低碳炼铁技术发展现状与前景

我国钢铁生产工艺长期以“高炉—转炉”长流程为主,能源结构高碳化特征明显。作为钢铁流程中的碳排放大户,炼铁系统深度减碳成为我国钢铁行业实现碳中和目标的关键。本文分别从高炉炼铁和非高炉炼铁两个角度出发,梳理总结了各主要低碳炼铁工艺技术的研究进展和主要问题,并对其应用前景进行了展望。我国钢铁工业应把技术创新作为降碳的核心要素,结合行业发展趋势和自身特点,加大力度开发适合我国国情的低碳炼铁新技术;综合考虑资产保值、技术成熟程度和降碳潜力,短期内应以基于现有高炉工艺的深度脱碳技术创新为主要方向,从而为远期零碳钢铁的发展提供过渡方案和缓冲空间;中长期以富氢气基竖炉直接还原技术为发展重点,不断提升其技术成熟度和经济适用性,逐步提高氢气比例直至全氢冶炼;氢基熔融还原技术和电解还原铁技术的发展任重道远,未来有望成为实现我国钢铁行业碳中和目标的解决方案之一。

铁矿氧化球团低温还原粉化性能的影响因素评述

在高炉和气基竖炉工艺中,为使炉况良好,应保证上升还原气能快速且均匀地穿过料柱,而含铁炉料的低温还原粉化和还原膨胀是恶化料柱透气性的两大主要原因.本文主要综述了影响铁矿氧化球团低温还原粉化性能的因素,并在此基础上讨论了改善球团矿低温还原粉化性能的主要措施.影响球团矿低温还原粉化性能的主要因素包括:球团矿的化学成分(碱度、SiO_(2)、MgO、Al_(2)O_(3)含量等)、物相组成、微观结构和碳沉积等.在实际生产中,可以通过优化球团矿成分(适当提高碱度或MgO含量等)和固结形式(发展部分液相固结)、调控球团矿孔隙结构(喷洒或涂层降低球团孔隙率)等来降低还原速率,减少还原过程产生的内应力,从而改善球团矿的低温还原粉化性能.

喷吹富氢燃料对高炉冶炼过程的影响初探

喷吹富氢燃料是高炉实现绿色低碳转型、践行双碳战略的重要举措。探讨了高炉喷吹富氢燃料的气体来源及其对冶炼关键参数的影响,同时分析了富氢燃料对含铁炉料还原行为的影响。认为:①受限于当前的制氢技术和成本,更多的是将焦炉煤气和天然气等氢含量较高的燃料喷入高炉;②高炉喷吹富氢燃料打破了炉内热平衡,改变炉料的冶炼进程;③现阶段富氢燃料喷吹过程中,氢气在还原剂中的占比仍旧较低,需通过调整高炉相关操作制度,以适应高氢碳置换比带来的挑战。