Direct Smelting Process Research Articles

Characteristics and applications of iron oxide reduction processes

Abstract The present review handles the main characteristics of iron oxide reduction and its industrial applications. The reduction of iron oxide is the basis of all ironmaking processes, whether in a blast furnace or by direct reduction and/or direct smelting processes. The reduction characteristics of iron ores control the efficiency of any ironmaking process and the quality of the produced iron as well. Many controlling parameters should be considered when discussing the reducibility of iron ores such as equilibrium phase diagrams, reduction temperature, pressure, gas composition, and the nature of both iron ores and reducing agent. The different factors affecting the main routes of ironmaking will be highlighted in the present review to give a clear picture of each technology. Moreover, further innovations regarding the reduction of iron oxides such as the reduction by green hydrogen will be discussed.

Direct smelting process of copper carbonate ore using SiO2 as fluxing agent in electric arc furnace

ABSTRACT The demand for copper, especially from the transportation sector, continues to increase. However, the supply of copper still depends on the primary process production, namely processing or extracting copper from its ore. In addition to copper sulfide ores, copper oxide and carbonate ores are alternative raw materials for copper production, especially in countries with abundant copper reserves, such as Indonesia. This study aims to analyse the effect of SiO2 flux addition in the direct smelting process of mixed oxide and carbonate-type copper ore. This study used an electric arc furnace to carry out the smelting process. The addition of SiO2 varied between 0 and 8 wt% with an interval of 2 wt%. As a result, a direct smelting product was successfully made with a Cu content of 87.01 wt% and Cu recovery of 92.6% when using 4 wt% SiO2. The slag’s main compounds were SiO2, Fe2SiO4, FeSiO3, and Fe3O4.

Investigation of Na2CO3–CaO–NaCl (or Na3AlF6) additives for the remanufacturing of silicon from diamond wire saw silicon powder waste

The demand for high-quality silicon for solar cell preparation will continue to grow due to shortages of silicon feedstock driven by the photovoltaic industry. Consequently, the silicon lost in diamond wire saw silicon powder waste during silicon wafer production must be recovered for silicon production. Depending on the current yield of silicon and level of residual impurities, an optimization treatment for the increase of the recovery rate and purity of silicon collected from diamond wire saw silicon powder should be further developed. In this study, NaCl and Na3AlF6 are designed as additives to optimize Na2CO3–CaO to increase the silicon recovery rate and purity. The action mechanisms of NaCl and Na3AlF6 for silicon recovery and the removal of metal during the direct smelting process are investigated. It is found that NaCl and Na3AlF6 improve the silicon migration channels and stabilize the impurities in slag by reducing the slag viscosity and tuning the slag composition. After induction smelting at 1823 K for 2 h with the furnace feed mass ratios of Na2CO3:CaO:NaCl = 12.8:1.7:8.6 and Na2CO3:CaO:Na3AlF6 = 12.8:1.7:8.6, the obtained silicon recovery rates were respectively 76.39% and 79.25%, and the silicon purities were respectively 99.985% and 99.986%. Therefore, NaCl and Na3AlF6 could be used as potential additives to promote the efficient remanufacturing of silicon collected from diamond wire saw silicon powder waste, and are technically and economically feasible for large-scale application.

Neutron imaging for metallurgical characteristics of iron products manufactured with ancient Korean iron making techniques

This paper demonstrates the possible nondestructive analysis of iron artifacts’ metallurgical characteristics using neutron imaging. Ancient kingdoms of the Korean Peninsula used a direct smelting process for ore smelting and iron bloom production; however, the use of iron blooms was difficult because of their low strength and purity. For reinforcement, iron ingots were produced through refining and forge welding, which then underwent various processes to create different iron goods. To demonstrate the potential analysis using neutron imaging, while ensuring artifacts’ safety, a sand iron ingot (SI–I) produced using ancient traditional iron making techniques and a sand iron knife (SI–K) made of SI–I were selected. SI–I was cut into 9 cm2, whereas the entirety of SI–K was preserved for analysis. SI–I was found to have an average grain size of 3 μm, with observed α-Fe (ferrite) and pearlite with a body-centered cubic (BCC) lattice structure. SI–K had a grain size of 1–3 μm, α-Ferrite on its backside, and martensite with a body-centered tetragonal (BCT) structure on its blade. Results show that the sample’s metallurgical characteristics can be identified through neutron imaging only, without losing any part of the valuable artifacts, indicating applicability to cultural artifacts requiring complete preservation.

The manufacturing technology of iron swords from the capital of the Han Empire in China

Xi’an City was the capital of China during the Western Han (202 BC–8 AD) and Xinmang (8–23 AD) periods. Metallographic studies of iron swords from this region are very rare. This study analyzed six iron swords from different tombs in Xi’an by metallographic examination, scanning electron microscopy, and energy-dispersive spectrometry. These results indicate that one sample was produced using a direct smelting process, while the other samples were made from Chaogang (炒钢) decarburization of indirect process. Two swords were identified as very early Bailiangang (百炼钢) objects, which were highly valued at that time. This study supplements current analytical data on the center of the Han Empire.

The Investigation on Enrichment of TiO2 from Ti-Bearing Slag

Titanium-bearing slag in this study was produced by subjecting titanium-bearing sea sand iron mineral to direct reduction smelting process. The enrichment and growth of titanium-rich phase in the titanium slag were investigated. The phases in slag were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. The results showed that Ti-rich phase had a pseudobrookite structure, and it was close to diffractogram of anosovite phase (M3O5 (M = Mg, Al, Ti)), in which the theoretical content of TiO2 is 73.2%. Line-scanning analysis was used to clarify the elements distribution trend in titanium slag. The results showed that Ti element was enriched in the anosovite phase, and Si and Ca assembled in the matrix phase. Mg and Fe elements were distributed in larger proportion in the anosovite phase, while the Al element was more enriched in the matrix phase. The experimental results showed that low cooling rate was in favor of titanium precipitate in anosovite phase. Moreover, the growth of anosovite crystal was characterized by kinetic model. These results provided further insights into the separation of anosovite from gangue by mineral processing.

Archaeometallurgical analysis of the bow drill from the fifth century BC Ma‘agan Mikhael shipwreck

Three bow drills were discovered in the 400 BC Ma‘agan Mikhael ship. Radiography revealed a square cross-section recess for the bit in the wooden stock of one of the drills. Metal particles, remains of a bit, survived in the recess. The metal composition, microstructure and manufacturing technology of the bit were studied using non-destructive and minimally destructive testing methods. These comprised digital radiography, light microscopy, X-ray fluorescence analysis, scanning electronic microscopy–energy-dispersive X-ray spectroscopy analysis, and micro-hardness indentation tests. The results demonstrated that the bit was made of wrought iron manufactured by the direct smelting process. A martensitic microstructure was observed after etching the external part of the bit. Examination of the iron oxide areas revealed a layered microstructure. Therefore, it is suggested that the bit was probably manufactured by forge-welding thin alternating layers of carburized wrought iron, which was heat-treated and quenched without tempering. This microstructure improved the hardness and strength of the metal. This is the first time that a metal bit found on a shipwreck of the period has been metallurgically investigated. It shows that the ancient blacksmiths produced the drill bit using the most suitable materials and advanced manufacturing processes. This information enlarges our limited knowledge about the use of carpenter’s tools in the East Greek/Phocaean fifth century BC shipbuilding tradition.

Enhanced Recycling of Waste Copper Smelter Dust from Existing and Proposed Smelter Plant at the Palabora Copper (pty) ltd, impopo, South Africa

The whole facilities at the Palabora Copper (PTY) Ltd (PC), Limpopo, South Africa (i.e. both existing and new) are under obligation to comply with the new plant MES by the 1st of April, 2020. At the moment all processes on the PC mine conform to the MES for existing plant with the exception of the copper smelter and the associated sulphuric acid plant. Despite considerable investment by PC over the last few years in equipment and maintenance, due to the short comings of the copper smelting technology employed on site, certain relevant MES have proven to currently be unachievable. The generation of the waste CSD is considered a global issue and at PC the direct smelting process option is the recycling method currently being used to manage the generated waste CSD at the copper smelting plant. This recycling method is neither cost effective nor energy efficient and it leads to the production of worthless residues. As a result, an enhanced hydrometallurgical based recycling process option is recommended as an appropriate recycling process option. Hence, it was concluded that an industrial scale centrifugal separator like the Knelson or Falcon concentrators be stationed in the existing and proposed plants as a separate but integral part of the ore processing system, so as to reduced/removed the reactive materials it often contains before subjecting it to a hydrometallurgical and Nano technological processing, in order to recover the copper value in it as precipitates of nanoparticles.

Direct smelting process for stainless steel crude alloy recovery from mixed low-grade chromite, nickel laterite and manganese ores

Stainless steel crude alloy recovery from direct smelting of low-grade chromite, nickel laterite and manganese ores was investigated. The mixed low-grade ores were directly smelted in an elevator furnace at smelting temperatures ranging from 1550 to 1600 °C. Smelting experiments were conducted in a laboratory elevator furnace equipped with 8 U-shaped high-quality molybdenum disilicide heating elements. A low-grade coal was used as the reductant. Experimental results showed that the recovery of Fe, Cr, Ni, Mn and Si within the alloy increased from 34.22, 60.27, 57.14, 25.42 and 13.02% to 69.91, 99.26, 86.02, 60.8 and 34.21%, respectively, when the temperature was increased from 1550 to 1600 °C. There was a general increase in the total recoveries of Fe, Cr, and Ni in the alloy with CaO addition increasing from 0.4 g up to 1.2 g. However, the recoveries of Mn and Si vividly decreased as the CaO contents were increased. In general, the recoveries of the metal contents of the crude alloy increase with the increase in the amount of manganese ore. Compared to the recoveries of Fe, Cr, and Ni when CaO was added, the recoveries of Fe, Cr and Ni were lower when manganese ore was used as an additive.

Manipulation of slag separation properties from pig iron nuggets with flux additions to dried greenball mixture

ABSTRACTPig iron nugget process is one of the direct smelting processes developed as an alternative to the traditional blast furnace process. Throughout the process, slag-free pig iron nuggets, which have similar properties to the blast furnace pig iron and white cast iron, are produced by single-stage heat treatment of dried greenballs. During the process, slag separation from the metallized areas can be enhanced by adjustment of the slag’s chemical and physical properties. The objective of this research was to investigate the effects of flux addition rates (basic to acid ratio) to the dried greenball mixture on pig iron nugget production and slag separation. Thus, this study involved the heat treatment of six different greenball mixtures, which contained various amounts of limestone addition (basic to acid ratios, 0, 0.63, 1.02, 1.42, 1.85, and 2.29) utilizing a laboratory-scale resistance box furnace or simultaneous differential scanning calorimetry and thermalgravimetric analyzer. The samples produced by heating in the box furnace were analyzed for their morphological and chemical properties utilizing optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), macroscopic observations, iron titrations, and atomic absorption spectroscopy. It was determined that the highest percentage of iron yield in the nugget for the process and the highest distribution of iron in magnetic slag were obtained when utilizing the greenball mixture, which contained 7.5 wt% limestone as flux (basic to acid ratio of 1.42).

Reducing Pyrometallurgical Selection of Particularly Refractory Ledge Gold Ore

The article is devoted to development of a brand new approach to solution of the issue related to development of efficient technologies aimed at processing of especially refractory and hard to concentrate ledge gold ore types. A new technology of such gold ore Reducing Pyrometallurgical Selection (RPS Process) utilising the direct smelting process avoiding its concentration has been developed for the purpose. Utilisation of high temperatures and liquid phase melting processes allows actually complete processing of refractory gold ores irrespective of the mostly complex resistance to processing types and with simultaneous and efficient performance of the following four process operations: a complete removal of any waste rock in the form of melted slag containing gold not exceeding 0.1‒0.3 g/t; a complete transfer into the gas phase and removal of arsenic and other harmful admixtures with off gases; complete combustion of all the ore carbon containing matter types obtaining additional heat for smelting and reducing gas phase; an actually complete transfer of any precious metals into a sulphide melt, collector matte, with gold recovery of 95‒99%, which yield will amount about 10% of the ledge gold ore weight. Thus, the developed technology ensures a ten-fold decrease of processed ore amounts in the process head. The RPS Process has been developed and tested in laboratories and under workshop conditions on the basis of direct electric smelting of hard to concentrate and refractory ledge gold ore from a number of deposits of Southern, Central and Eastern Kazakhstan. Such tests of the RPS Process revealed the possibility to increase throughout gold recovery by 10‒15% as compared with currently achieved in dices in case of especially refractory ledge ore processing.

Developing Nanomaterials for Ironmaking Processes: Theory and Practice

Ironmaking processes take three main forms namely; blast furnace, direct reduction and direct smelting processes. Ironmaking is energy intensive sector as it requires huge amount of natural resources. It is also very important for the worldwide economy where it provides the backbone for construction, transportation and manufacturing. Many factors are strongly affecting the developing of ironmaking processes such as energy consumption, materials costs, and environment problems. These factors should be considered when discussing any new trend for developing ironmaking processes. The present work handles the current status and future of ironmaking processes. The technical and economic environment that motivates the development of these processes will be also clarified. The manuscript is designated to investigate theoretically and practically the possibility of using nanomaterials in ironmaking processes. Nano-sized iron oxides can be considered a promising source for deceasing energy consumption in iron and steel industry. The reduction of iron oxide is the most important processes in ironmaking and usually operated at relatively high temperatures. The nanopowder of iron oxide could be charged to a blast furnace together with the blast, much like the current pulverized coal injection technology. In that case, the reducibility of blast furnace burdens will be improved and consequently the energy consumption for reduction will be declined. Accordingly, minimizing the energy consumption will greatly influence the gross energy consumption of iron and steel production.

Mineral phase reconstruction behavior of direct reduction and smelting titanium slag at high temperature and slow cooling

Titanium slag in this study was produced by subjecting titanomagnetite concentrate to direct reduction-electric furnace smelting. Processing mineralogy and mineral phase reconstruction behavior at high temperature and slow cooling treatment were examined by chemical analysis, X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). Anosovite solid solution is the main titanium product by the direct reduction and smelting process. Results of slow-cooling experiments show that crystal volume and size increase as cooling rate decreases. Anosovite and gangue mineral crystals develop fully with large crystal volume and size at a cooling rate of 2 K·min−1. Moreover, the growth of anosovite crystal was characterized by crystal nucleation and growth theory. These results provide further insights into the separation of anosovite from gangue by mineral processing.

Kinetic model for direct smelting reduction process of Huimin iron ore

A series of experiments have been carried out to investigate the direct melting reduction process of high phosphorus iron in a nitrogen atmosphere with non-isothermal heating. The weight loss factor of the iron ore can be considered as a function of the temperature in the reduction progress. The kinetic parameters of the model can be determined by the data in a single test with a non-isothermal heating rate. With the temperature increasing, the reduction process can be divided into decrystal water phase of limonite, the pre-reduced phase of hematite, and finally reduced phase. The final reduction can be divided into three sections. On this basis, functions of the reaction mechanism and apparent activation energy in each stage are expected to be investigated. Then, the compensation effect of the whole reaction process is presented. Finally, the relationship of apparent activation energy and pre-exponential factor are also analysed.

Paradigm for pig iron nugget production

Economic, environmental and operational disadvantages of the traditional blast furnace process has led to the development of direct smelting reduction processes, including those that utilize self reducing/fluxing dried green-balls as iron oxide feed materials. This is mainly due to improved carbothermic reduction, carburization and reaction kinetics. In this paper, the morphological changes of the greenballs as they transform to pig iron nuggets are examined over time at a constant temperature of 1,400° C. The products produced after each treatment were characterized using optical microscopy, scanning electron microscopy/energy dispersive spectroscopy and point counting/image analysis. The changes in the percent metallized area, wustite dendrite and slag matrix content of the structures were calculated. It was determined that the transformations were initially controlled by dissolving and containment of iron oxides in the molten slag and their consequent reduction to iron, followed by coalescence of the metallized areas. The final transformations were controlled by the carburization of the metallized areas.

Mathematical modelling tools for the optimisation of direct smelting processes

Direct smelting operations involve the strong interaction of a wide range of complex physico-chemical processes. Moreover, for such processes to be efficient, these interactions have to be optimised to yield the desired set of chemical reactions and exchanges of heat and mass amongst the variety of gaseous, liquid and solid phases. This paper focuses upon a consideration of Computational Fluid Dynamics (CFD) based models developed to represent the HIsmelt ® direct smelting process. The models are extremely sophisticated and at every stage have challenged the limits of CFD technology, as well as the adequacy of constitutive sub-models to represent the chemical reaction/combustion phenomena. From an unprecedented synergy amongst process metallurgists, experimental scientists and CFD modellers, sophisticated, comprehensive and well-validated models of the process have evolved. The paper highlights some of the key state-of-the-art CFD techniques developed for the models and the role of specially designed experiments in parameter estimation and validation against plant measurements.

97/02244 Pilot plant study of direct iron ore smelting (DIOS) process

97/02244 Pilot plant study of direct iron ore smelting (DIOS) process

Direct smelting and alternative processes for the production of iron and steel

Processes for the direct smelting of iron and steel are presented together with a discussion of alternatives based on plasmas and the direct production of iron carbide. The advantages and disadvantages of each technology are presented and their energy efficiencies are discussed.

Prediction of an iron oxide concentration in the induction smelting process

Induction smelting process, ISP, is a direct smelting process in which self‐fluxed composite pellets (made of iron ore, brown coal and lime) are melted in a single phase induction furnace in conjunction with top blown oxygen. A mass transfer model to predict the concentration of iron oxide, has been developed for this process. Transient mass balance equation with complex boundary conditions has been worked out by adopting a relatively new approach known as the cell model approach. These equations have been solved numerically using finite difference technique to obtain the iron oxide concentration profile in the induction smelting process. Numerical and experimental results obtained for the iron oxide concentration show a reasonable agreement with each other.

A review of progress of the development of new ironmaking technologies

There is a revolution on the horizon in the iron and steel industry with the development of new direct smelting technology for the high intensity production of liquid iron from iron ore fines and agglomerates. These processes have the potential to completely replace the conventional blast furnace production of hot metal as they offer processing advantages such as: • ∗ use of coal rather than metallurgical coke • ∗ use of iron ore fines rather than lump ores or sinter • ∗ economic operation at small scale (250,000–500,000 T/A) • ∗ lower capital costs • ∗ increased flexibility in operation and materials use • ∗ greater environmental control The paper will discuss the technical and economic environment which is prompting the development of the new processes. This will include a review of direct smelting process fundamentals and the range of processing options offered by the new technology. Past developments will be briefly discussed as an introduction to a review of the current group of processes with potential for commercialization over the next 5–10 years. There is a high level of activity in Europe, Japan, Australia, South Africa and the USA devoted to the development of these new generation processes. Groups include British Steel, CRA/Midrex, Voest-Alpine AG, the American Iron and Steel Institute and most of the major Japanese iron and steel companies (Kawasaki, Sumitomo, Nippon Steel, Kobe, NKK) who are developing their own processes and contributing to a National Project on smelting reduction. The processes arising from these groups will be compared and contrasted to provide an analysis of their chances of technical and economic success.