Smelting Reduction Process Research Articles

Thermochemical analysis for the reduction behavior of FeO in EAF slag via Aluminothermic Smelting Reduction (ASR) process: Part Ι. Effect of aluminum on Fe & Mn recovery

We investigated Fe recovery from EAF slag by means of Aluminothermic Smelting Reduction (ASR) at 1773K, especially the quantitative effect of initial Al/FeO molar ratio upon the Fe recovery. Both calculated and experimentally measured system temperatures continuously increased with increasing initial Al/FeO molar ratio. Furthermore, to predict the reduction behavior we calculated variations in the slag composition by using FactSage™ 7.0 software. FeO and Al2O3 contents in molten slag varied sharply within the first 5min of the reaction and stabilized soon thereafter. The aluminothermic reduction of FeO appeared to proceed rapidly and in good stoichiometric balance, based upon the mass balance between the consumption of FeO and MnO (ΔFeO and ΔMnO) and the production of Al2O3 (∆Al2O3). Adding an optimal amount of Al (Al/FeO molar ratio ~ 0.8) yielded a Fe recovery of about 90%. Furthermore, the Mn could also be reduced from the EAF slag in the case of excess Al addition (Al/FeO≥0.8). The solid compound spinel (MgO·Al2O3) was precipitated from the slag during the FeO reduction, as confirmed by means of XRD analysis and thermochemical computations. Herein, the mechanism of ASR reaction between FeO in molten slag and Al is explained in several steps.

Recovery of valuable metals from spent lithium ion batteries by smelting reduction process based on FeO–SiO2–Al2O3 slag system

A novel smelting reduction process based on FeO–SiO2–Al2O3 slag system for spent lithium ion batteries with Al cans was developed, while using copper slag as the only slag former. The feasibility of the process and the mechanism of copper loss in slag were investigated. 98.83% Co, 98.39% Ni and 93.57% Cu were recovered under the optimum conditions of slag former/battery mass ratio of 4.0:1, smelting temperature of 1723 K, and smelting mass ratio of time of 30 min. The FeO–SiO2–Al2O3 slag system for the smelting process is appropriate under the conditions of m(FeO):m(SiO2)=0.58:1–1.03:1, and 17.19%–21.52% Al2O3 content. The obtained alloy was mainly composed of Fe–Co–Cu–Ni solid solution including small amounts of matte. The obtained slag mainly consisted of fayalite and hercynite. Meanwhile, the mechanism of copper loss is the mechanical entrainment from strip-like fayalite particles in the main form of copper sulfide and metallic copper.

Discrete particle simulation of solid flow in a melter-gasifier in smelting reduction process

Smelting reduction process is one of the promising technologies that produce liquid iron with advantages in the reduction of costs and adverse effect on environment. In this process, the main reactor of Melter-Gasifier (MG) involves complicated multiphase flow, heat and mass transfer phenomena, in which solid flow plays a dominant role. In this work, the solid flow behavior in an MG is investigated by discrete particle simulation under different conditions. The results show a good agreement with the observations in experiments. It reveals that three stagnant zones are formed: one is at the MG central bottom, and the other two are located on the side walls. The analysis indicates that charging method, MG geometry, and particle-wall frictional force are factors affecting the size of the stagnant zones on the side walls. Rolling friction does not affect solid flow much. Particle scale analysis of solid flow and force structures is also conducted, showing that strong forces exist in the regions with low porosity. The analysis of particle mass fraction shows that at the MG upper part, HCI (hot compacted iron) particles dominate the MG center, and coal particles tend to distribute to the side walls.

Complex Processing of a Titanium Magnetite Concentrate with Receiving the Products Containing Iron, The Titan and Vanadium

Present study determines conditions for titanium magnetite concentrate processing with fairly complete titanium conversion to the slag and iron and vanadium separation in the hot metal. It is quite difficult to process titanium magnetite concentrate in the blast furnaces due to low fusibility of charge and direct electrical melting which cause process instability. Present work is devoted to development of concentrate double stage smelting process with little soda additions, including solid-phase recovery at the first stage using specific coke as a reductant, avoiding concentrate oxidation and including its preliminary thermooxidation. Mix charge made of concentrate, soda and specific coke was granulated in water, dried at 130°C, pellets were placed in graphite crucible, and later on it was set up in the centre of the furnace in alundum crucible. Temperature regimen was fixed under following parameters: temperature at the first stage was 1250°C; soaking time was 50 min; temperature at the second stage was 1500 - 1650°C; soaking time was 35 min. It is established that little soda additive (estimated 3-4% Na2O) to the charge of titanium magnetite concentrate recovery smelting behaves as a coagulant during briquetting, as a catalyst in course of solid-phase recovery, as an inhibitor of DRI briquettes secondary oxidation as slag thinner during smelting. In course of titanium magnetite concentrate reduction smelting process, soda interacts to SiO2, AhO3, TiO2 oxides forming sodium silicates and titanates. Double-stage technology of titanium magnetite concentrate reduction smelting was used, both with soda addition, and without oxidation and preliminary iron oxidation of titanium magnetite concentrates till hematite was developed. Optimal process parameters were determined. Following parameters were obtained: hot metal yield was ∼⃒55% of concentrate weight, slag yield - 23.3-25.8%, carbon-free slag content, wt.%: Fe=1.0-1.6; TiO2=62.7-61.9. TiO2 yield in the slag was 89.6-94.1%. Hot metal contains, %: 5,51 C; 0.36 Ti; 0.35 Mn; 0.04 Si; 0,23 V. Vanadium yield in iron was 53.0%.

Three-dimensional discrete element method simulation of the effect of bottom structure on solid flow in COREX shaft furnace

COREX is an industrially and commercially proven smelting reduction process. The shaft furnace (SF) for the pre-reduction of iron ore is one of the two major reactors of COREX. As one of the industrial systems using screw feeders, the burden descending behaviour in SF can be directly affected by the bottom structure such as the design of screw and associated charging container. In this work, a three-dimensional actual size model of COREX-3000 SF is established by means of the discrete element method. The effect of bottom structure, for example, the guiding cone and the design of screw, on solid flow is investigated. The results show that burdens are mainly drawn down from the first flight of the screw in the reference case, while the slow-moving particles located above the end of the screw. Placing a guiding cone and reducing the flight diameter of screw have a benefit for restraining the descending velocities in the central area of the SF and help to obtain a uniform flow pattern. An optimised case is also proposed. In the optimised case, a relatively uniform solid flow profile can be obtained and the uniformity of descending velocity along the radius is improved greatly. The findings of this work should be useful for the design, control and optimisation of the SF operation.

Вещественный состав и особенности обогащения и подготовки бедных и труднообогатимых железных руд с целью их использования в бездоменных технологиях получения чугуна «Ромелт»

Вещественный состав и особенности обогащения и подготовки бедных и труднообогатимых железных руд с целью их использования в бездоменных технологиях получения чугуна «Ромелт»

Operating line for COREX smelting reduction ironmaking process

Based on the principle of Rist operating line, the problem in the smelting process of smelting reduction process of COREX oxygen transfer and energy consumption had been studied. The principles and methods of COREX operation line establishment were proposed. The actual production condition in the field was given in the form of tables, including its main raw material and fuel consumption and the main product in the smelting process. In these conditions, the actual operation of COREX production line was established. The actual operation effect could be directly get by the analysis of the operation of the line. These works provided a study direction for improving the energy utilisation in the production process of COREX. And the effect of the feed conditions and operating parameters on the energy utilisation was analysed. That could provide a theoretical basis for on-site staff operating.

Smelting of Bauxite Residue (Red Mud) in View of Iron and Selective Rare Earths Recovery

During acid leaching of bauxite residue (red mud), the increase in dissolution of rare-earth elements (REEs) is associated with an increase in iron dissolution, which poses problems in the downstream processing. Therefore, it would be beneficial to remove iron from bauxite residue by smelting reduction. The slag generated in the smelting reduction process could then be further processed for recovery of REEs. Smelting experiments were carried out at temperatures between 1500 and 1600 °C. Wollastonite (CaSiO3) was used as a flux and graphite as a reducing agent. The addition of wollastonite decreases the slag melting temperature and the viscosity, facilitating slag-metal separation, whereas a graphite content higher than the optimum level alters the slag chemistry and hinders the slag-metal separation. The optimum conditions were found to be for heating at 1500 °C: 20 wt% of wollastonite and 5 wt% of graphite. More than 85 wt% of the iron was separated from the slag in the form of a nugget. A further 10 wt% of the iron could be extracted from the slag by subsequent grinding and magnetic separation. The slag obtained after iron removal was treated with HCl, HNO3, and H2SO4 acids to extract REEs. Room-temperature leaching was found to be not beneficial for REEs extraction. High-temperature leaching enhanced the recovery of REEs. More than 95 % of scandium, >70 % of REEs, and about 70 % of titanium could be leached at 90 °C. The selectivity of REEs over iron during slag leaching was clearly improved.

Static Model of Iron Bath Smelting Reduction Process with Thick Slag Layer

Static Model of Iron Bath Smelting Reduction Process with Thick Slag Layer

Analyses of solid flow in COREX shaft furnace with AGD by discrete element method

COREX is an industrially and commercially proven smelting reduction process. The shaft furnace (SF) for the direct reduction of iron ore is one of the two major reactors of COREX. In the new design of COREX-3000 SF in Baosteel, China, a new technique called areal gas distribution (AGD) has been adopted. With the installation of two AGD beams, the cross-sectional area varies in a complicated manner, which will affect the burden descending behaviour. This work uses a slot model to investigate the solid flow behaviour in the SF by discrete element method. The applicability of the discrete element method model is validated. The results confirm that the flow profile in SF with AGD evolves from a flat to wave and finally to W profile as the solids descend. A triangle shaped free area is observed under the AGD beam, which is the main channel for gas flow into the shaft centre. Increasing the discharging rate has an effect of decreasing the quasi-stagnant zone size, but does not affect the macroscopic motion of particles and flow pattern above the bustle. The cross-section of AGD channel increase with the increase in the discharging rate. Under the asymmetric condition, the solid flow pattern is asymmetric. The influence of AGD on macro- and microscope properties of solid flow in SF is also evaluated. This investigation reveals that AGD beams affect the particle uniform descending in bustle zone and increase the complexity of normal force distribution.

Leaching Kinetics of Praseodymium in Sulfuric Acid of Rare Earth Elements (REE) Slag Concentrated by Pyrometallurgy from Magnetite Ore

A leaching kinetics was conducted for the purpose of recovery of praseodymium in sulfuric acid (<TEX>$H_2SO_4$</TEX>) from REE slag concentrated by the smelting reduction process in an arc furnace as a reactant. The concentration of <TEX>$H_2SO_4$</TEX> was fixed at an excess ratio under the condition of slurry density of 1.500 g slag/L, 0.3 mol <TEX>$H_2SO_4$</TEX>, and the effect of temperatures was investigated under the condition of 30 to <TEX>$80^{\circ}C$</TEX>. As a result, praseodymium oxide (<TEX>$Pr_6O_{11}$</TEX>) existing in the slag was completely converted into praseodymium sulfate (<TEX>$Pr_2(SO_4)_3{\cdot}8H_2O$</TEX>) after the leaching of 5 h. On the basis of the shrinking core model with a shape of sphere, the first leaching reaction was determined by chemical reaction mechanism. Generally, the solubility of pure REEs decreases with the increase of leaching temperatures in sulfuric acid, but REE slag was oppositely increased with increasing temperatures. It occurs because the ash layer included in the slag is affected as a resistance against the leaching. By using the Arrhenius expression, the apparent activation energy of the first chemical reaction was determined to be <TEX>$9.195kJmol^{-1}$</TEX>. In the second stage, the leaching rate is determined by the ash layer diffusion mechanism. The apparent activation energy of the second ash layer diffusion was determined to be <TEX>$19.106kJmol^{-1}$</TEX>. These relative low activation energy values were obtained by the existence of unreacted ash layer in the REE slag.

Experimental Study on Burden Descending Behavior in COREX Shaft Furnace with AGD Beams

COREX is an industrially and commercially proven smelting reduction process. It consists of two reactors, the shaft furnace (SF) and the melter gasifier and the SF is placed above the melter gasifier. In the new design of COREX‐3000 in Baosteel, China, a new technique called Areal Gas Distribution (AGD) has been adopted. With the installation of two AGD beams, the cross‐sectional area varies in a complicated manner which will affect the burden descending behaviour. This work uses a cold model to investigate solid particle behaviour in the SF of COREX‐3000. The effect of gas flow, discharging rate and abnormal conditions are characterised in terms of solid flow pattern. The results show that gas flow has a minor effect on burden descending behaviour. Increasing the discharging rate has an effect of reducing the quasi‐stagnant zone. A gas channel is observed downstream of AGD beam and the triangle shaped free area increase with the increase of burden discharging rate. For asymmetric flow, particles descend from the top and move to the discharging outlet and a very big stagnant zone is formed on the opposite side of the discharging outlet. The effect of AGD beams on solid flow is evaluated under normal and abnormal conditions. The investigation reveals that the AGD beams affect the solid flow significantly and lead to poor adaptability of furnace to abnormal operations.

A Comprehensive Static Model of an Iron Bath Smelting Reduction Process with Thick Slag for Alumina-Rich Iron Ore

In order to make comprehensive utilization of alumina-rich iron ore, a two-step three-vessel smelting reduction process is proposed, including the Rotary Hearth Furnace (RHF) for the pre-reduction of alumina-rich iron oxide pellet, the Smelting Reduction Vessel (SRV) with a thick slag bath for the final reduction and melting of pellet, and the Gas Reforming Furnace (GRF) for reforming the exhaust gas from SRV. A three-level lances arrangement is designed to improve the energy utilization and production condition of the SRV. An overall process model is established for the whole process to calculate the mass and heat consumptions of all sections of the process, and to investigate the effect of operation conditions on the process performance. With 80% heat transfer efficiency of post combustion, the recommended post combustion ratio (PCR) of the SRV gas is 55% and the pellet metallization rate (PMR) is 80%. A zoned model of the SRV is developed to calculate the mass and heat balances of each reaction zones and especially to optimize the operation conditions. The recommended PCRs in the upper slag and lower slag are 15% and 0% respectively. The coal-only injection method is recommended in the lower slag.

Effect of Ilmenite Component and AIR on Element Distribution of Titanium Slag Smelted by DC Arc Furnace

Abstract Based on chemical equilibrium calculation method in multi-phase, multi-component system, the effects of ilmenite component (TiO 2 , Fe 2 O 3 , FeO) and AIR (anthracite to ilmenite ratio) on element distribution of titanium slag smelted by DC arc furnace were studied. The calculated results agree well with the experimental results. With increasing amount of TiO 2 and FeO in ilmenite, the amount of C as trace element and for TiO 2 and FeO reduction increases, the total mass fraction of TiO 2 and Ti 2 O 3 in slag increases, while the mass fraction of FeO in slag decreases. However, the effect of Fe 2 O 3 content in ilmenite on the slag composition is opposite. With increasing of TiO 2 in ilmenite from 42% to 50%, the mass fraction of TiO 2 in slag increases by 7.9%. However, with increasing of Fe 2 O 3 in ilmenite from 12% to 20%, the mass fraction of FeO in slag increases by 8.94%. Moreover, with increasing of AIR from 120 to 134 kg·t −1 , the mass fraction of TiO 2 in slag increases from 83.8 % to 91.77%, FeO mass fraction decreases from 14.7% to 6.25%. The order of effect of other components on the total TiO 2 in slag is displayed as: SiO 2 >MgO>Al 2 O 3 >CaO. Ilmenite component and AIR can be controlled to achieve selective reduction of oxides in the melt. Study on allocation behavior of elements during titanium slag smelting reduction process can help to control the process, improve the slag grade.

Cr and Ni Recovery and Oxidational Dephosphorization of Stainless Steel Dust during the Iron-Bath Smelting Reduction Process

According to the comprehensive utilization of 300 series and 400 series stainless steel dust (SSD), and the dephosphorization of the reclaimed Cr-Ni contained hot metal, an experimental method of smelting reduction in iron-bath and oxidational dephosphorization was studied. The result shows: The yield rate of Cr in 300SSDand 400SSDis 98.13% and 98.39% respectively, the yield rate of Ni is almost 100%; During the dephosphorization, through the BaO and CaO-BaO based dephosphorizer has a higher Dephosphorization rate, it can bring pollution problems and the cost is too high, however, under some circumstance when the requirement of phosphorus content is not critical, the CaO based dephosphorizer can also achieved the dephosphorization goal.

High temperature pyrolysis behaviour and kinetics of lump coal in COREX melter gasifier

The COREX process is an industrially and commercially proven smelting reduction process producing hot metal of the same quality as blast furnace ironmaking. The high temperature pyrolysis behaviour of lump coal is crucial important in the COREX melter gasifier, which determines energy utilisation and gas composition, as well as metallurgical property and particle size of semicoke produced. In the present study, an experimental study was carried out to simultaneously investigate the pyrolysis behaviour of two Chinese lump coals used in the COREX process at different temperatures, and the effect of pyrolysis temperature on microstructure of semicoke produced was analysed by X-ray diffraction technology. In addition, the pyrolysis mechanics and the kinetics parameters of two lump coals were obtained. The results show the pyrolysis rate of lump coals is very rapid, the required time to completion of pyrolysis decreases with increasing temperature, and the contents of moisture and volatile have a remarkable effect on the maximum weight loss rate. The pyrolysis process of lump coals includes three stages: the first is water release accompanying a small quantity of devolatilisation, the second is devolatilisation, and the third is stabilisation. It is found the stacking height of graphite-like crystallite layer along the c-axis for the produced semicokes gradually increases with increasing temperature, the micro graphite spacing decreases and the crystallite size increases while raising the pyrolysis activation temperature. Three-dimensional diffusion is the primary restrictive link in the whole pyrolysis process of lump coals, the expression 3/2(1−α)2/3[1−(1−α)1/3]−1 is the optimal kinetic mechanical function. The apparent activation energy decreases with volatile increasing.

Numerical Modelling of the Moving Bed Inside the COREX® Melter-Gasifier

The COREX®-process is the first commercially operating smelting reduction process for the production of pig iron. For this reason, it can be seen as an alternative to the common industrial iron-making route via the blast furnace. For both, the COREX® melter-gasifier (MG) and the blast furnace, good gas-solid contact is essential for the stable and efficient operation of the process. Due to the very harsh conditions inside the MG, the possibilities for measurement of process conditions are very limited. Thus, detailed numerical models are required to gain additional understanding of the physical and chemical processes occurring within the MG.

Research on the Thermodynamics and Kinetics of Chromium Ore Smelting Reduction Process for Producing Stainless Steel

For describing and resolving the process of chromium ore smelting reduction preferably, the research status on the thermodynamics and kinetics of chromium ore smelting reduction process was summarized, based on the introduction of the process for smelting stainless steel with hot metal in a converter. The existing problems for smelting stainless steel by chromium ore smelting reduction in a converter were also discussed and some suggestions were made for the future work. A lot of investigations about the thermodynamics and the reduction mechanisms of chromium ore have been done. However, the consistent view about the thermodynamic feasibility and the mechanism of smelting reduction has not been achieved, so the application of research results is limited. Little work about the reaction kinetic model for the production of stainless steel by chromium ore smelting reduction and direct alloying has been done. So the synthetic kinetic model including a dissolution model and a reduction model of chromium ore should be built to predict and control accurately the process.

The ammonia leaching of alloy produced from waste printed circuit boards smelting process

The ammonia leaching tests were carried out to recover valuable metals from alloy obtained from smelting reduction process of mobile phone printed circuit boards. Leaching factors such as kinds of salt, ammonia concentration, and the interaction of metals, which are components of PCB, were investigated to improve the leaching efficiency. In the leaching tests using metal powders such as Zn, Sn, Ni, and Pb to investigate the interaction of metals, zinc was easily dissolved in ammonia solution, whereas Sn and Ni were not detected or the Pb concentration decreased rapidly. The metal concentrations increased with an increase in NH3 concentration from 1 to 5 kmol m− 3. The content of Cu could increase to 98% under the leaching conditions: 2 kmol m− 3 NH4Cl and 5 kmol m− 3 NH3 solution with 0.1 kmol m− 3 CuCl2 at 200 rpm and 30°C with 1% pulp density.

Mn Ore Smelting Reduction Based on Double Slag Operation in BOF

This paper aims at finding a way to increase the rate of Mn yield in Mn ore smelting reduction process based on double slag operation in BOF. The thermodynamics of the process was analyzed and the experiments including slag-steel reaction in lab and steelmaking simulation in pilot plant were carried out. The results above were proved to be valid in industrial scale experiment in general steelmaking factory of WISCO. The industrial scale experimental results showed that 35%~50% of Mn yield could be obtained with conditions of higher temperature and high carbon content at the end point in conventional BOF process based on double slag operation, which can benefit to the efficiency of BOF process as well as less carbon emissions.