Pig Iron Nuggets Research Articles

The production of high value pig iron nuggets from steelmaking by-products – A thermodynamic evaluation

Zinc contaminated steelmaking by-products such as blast furnace (BF) dust and basic oxygen steelmaking (BOS) dust present a significant recycling challenge at integrated steelmaking plants. Rotary Hearth Furnaces (RHFs) provide an attractive route for recovery of Fe and Zn from these materials through carbothermal reduction of the oxides in the material to yield Direct Reduced Iron (DRI) and crude zinc oxide. The next generation of RHF processes such as ITmk3 and e-nugget produce pig iron nuggets from iron ore concentrates and coal, as iron and gangue separate in-situ without an additional melting unit. A computational study of the metal-slag system using FACTSAGE 7.3 suggests that production of pig iron nuggets of good quality (93.75 wt.% Fe, 4.3 wt.% C, 0.116 wt.% S, 0.66 wt.% Mn) can be produced from BF dust and BOS dust in a ratio of 37:63 with addition of 5.4 wt.% SiO2 and 1.51 wt% MgO at 1450 °C. These computational results are in good agreement with experimental studies on similar material and, as such, suggest a practically feasible process.

Production of pig iron nugget from low-grade iron ore and pyrolyzed oil-palm-empty-fruit-bunch composites

Utilization of low-grade iron ore and pyrolyzed oil palm empty fruit bunch (EFB) is an effective way as the solution to deal with the depletion of iron reserves and administer of empty fruit bunch waste. This study was aimed to analyze the pig iron that is produced by carbothermic reduction of low-grade iron ore with pyrolyzed palm oil EFB as a reductant. The ore from Lampung was reduced at temperature 1400°C and 1450°C for holding time 40 minutes with inert condition (N2 atmosphere). The structures of pig iron were studied by using X-Ray diffraction (XRD), and the microstructures and chemical composition were analyzed by using Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS). It was found that iron nugget that was reduced at 1450°C for 40 minutes that was wholly separated from its slag, with reduction degree 98.5%, metallization degree 99.2%. The microstructure has metallic iron as a base with some pores. On the other hand, the other iron nuggets that are not separated from its slag consist of two prominent phases, metallic iron and lamellar fayalite (Fe2SiO4).

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).

Dephosphorisation of high phosphorus oolitic hematite by carbon composite pre-reduction and fast melting separation

High phosphorus oolitic hematite deposit is a kind of refractory iron ore resource of huge amount. At present, it is difficult to be utilised by traditional physical and chemical technology efficiently and economically. A novel process for utilisation of the high phosphorus oolitic hematite based on carbon composite pre-reduction and fast melting separation has been put forward in the paper. High grade pig iron nugget of low phosphorus could be obtained in the present research. The influence of experimental conditions, such as pre-reduction temperature, C/O (molar ratio) and basicity, on the dephosphorisation behaviours was studied in detail. The thermodynamic basis and reduction and melting separation process were also analysed. The phosphorus content in the iron nugget decreased with the increasing of basicity and increased with the increasing of C/O. The optimum parameters were pre-reduction temperature of 1200°C for 30 min, C/O of 0.95 and basicity of 1.7. After melting separation of molten iron and slag at 1400°C for 10 min, the iron nugget containing 0.02 wt-% [P] would be obtained. The dephosphorisation degree and iron yield in the form of iron nugget were 97.5% and 96.9% respectively. The iron nugget may be directly used as the raw materials of steelmaking from the view point of its high grade.

Characterization and Reduction Behavior of Cold-Bonded Composite Pellets for Direct Reduction Using an Organic Binder

The purpose of this study was to investigate the reduction behavior of cold-bonded composite pellets produced from low-grade hematite iron ore using molasses solution at various concentrations, as well as their physical and chemical properties. Direct-Reduction Iron (DRI) technology makes it possible to assess low-grade iron ores and convert them into scrap at facilities that have electric arc furnaces. The reductant used was coke with fixed carbon of 86.04%. The alkalinity rate was adjusted to 0.7 by adding calcium carbonate. In the composite pellets produced, the 300 N/pellet compression strength recommended in the literature was achieved with a Fetot/Cfix ratio of 2.5 and 3 using a 50% concentrated molasses solution. Composite pellets prepared with a Fetot/Cfix ratio of 3.5 using a 40% concentrated molasses solution reached a compression strength of 496 N/pellet. The porosity is inversely proportional to the increase in compression strength and binder concentration. Reduction experiments were conducted by applying different temperatures and durations to samples possessing optimum conditions for each Fetot/Cfix ratio: the best result was achieved with a 88% reduction rate in composite pellets with a Fetot/Cfix ratio of 3.5 at the end of 1 h. Pig iron nuggets were characterized using an optical microscopy (LOM) and a scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS).

Production of pig iron by utilizing biomass as a reducing agent

Large carbon dioxide (CO2) emissions in iron and steel industry are caused by the use of non-renewable and fossil fuel derived reducing agents. Currently coal, metallurgical coke, and natural gas are major reducing agents used in different ironmaking processes. In order to reduce iron oxide into metallic iron, carbon is required which is also stored in many types of biomass in the form of carbohydrates. In this study self-reducing iron oxide and biomass composite pellets were made. Pellets were then fired at different temperatures for different residence times. Results show that high quality pig iron nuggets not only can be produced at various temperatures, they can also be produced at a very short residence times.

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.

Shrinking-core model for pig iron nugget production

Considerable effort has been directed towards understanding the carbothermic reduction mechanisms of self-reducing, fluxing dried green balls to produce pig iron nuggets. Given the geometry of the situation, some investigators believed that the shrinking core model was applicable. Hence, this study involved investigation of the applicability of the shrinking core model to pig iron nugget production. The experiments involved heat treatment of dried green balls utilizing either a laboratory-scale resistance box furnace or a gas-fired muffle furnace at various furnace temperatures and residence times. The products were analyzed for the following: (i) preferred reaction pattern, (ii) distribution of the metallized areas, (iii) % iron content variation in the pig iron nuggets from surface to center, (iv) carburization pattern and (v) physical and chemical properties of the pig iron nuggets. It was determined that the reduction of iron oxide occurred simultaneously throughout the sample and not beginning at the surface and propagating inward; thus the shrinking-core model was not applicable. Heat transfer and gas diffusion from surface to center were not the rate-limiting steps for reduction and carburization reactions.

Conditions for making direct reduced iron, transition direct reduced iron and pig iron nuggets in a laboratory furnace — Temperature-time transformations

The pig iron nugget process is gaining in importance as an alternative to the traditional blast furnace. Throughout the process, self-reducing-fluxing dried greenballs composed of iron ore concentrate, reducing-carburizing agent (coal), flux (limestone) and binder (bentonite) are heat-treated. During the heat treatment, dried greenballs are first transformed into direct reduced iron (DRI), then to transition direct reduced iron (TDRI) and finally to pig iron nuggets. The furnace temperature and/or residence time and the corresponding levels of carburization, reduction and metallization dictate these transformations. This study involved the determination of threshold furnace temperatures and residence times for completion of all of the transformation reactions and pig iron nugget production. The experiments involved the heat treatment of self-reducing-fluxing dried greenballs at various furnace temperatures and residence times. The products of these heat treatments were identified by utilizing optical microscopy, apparent density and microhardness measurements.

The Microstructure of the Pig Iron Nuggets

The pig iron nugget process (referred to as the Iron Technology Mark 3, or ITmk3, process by Kobe Steel) was developed as an alternative to the traditional blast furnace process. Throughout this process self reducing–fluxing dried greenballs are reduced and smelted in to nuggets of metal. The objective of this research was to produce pig iron nuggets at laboratory scale, then characterize and compare them with the blast furnace pig iron. Pig iron nuggets were characterized utilizing apparent density measurements, optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, and bulk chemical analysis. It was determined that pig iron nuggets had high apparent density (6.7–7 g/cm3); had a high iron content (95–97%); and exhibited microstructures similar to white cast iron, which is essentially the same as pig iron from a blast furnace.

Carburization effects on pig iron nugget making

The iron nugget process is an economical, environmentally friendly, cokeless, single-step pig iron making process. Residence-time dependent process requirements for the production of pig iron nuggets at a fixed furnace temperature (1,425°C) were investigated. Depending on the residence time in the furnace, three chemically and physically different products were produced. These products were direct reduced iron (DRI), transition direct reduced iron (TDRI) and pig iron nuggets (PIN). The increase in the carbon content of the structure as a function of residence time was detected by optical microscopy and microhardness measurements. Sufficient carbon dissolution for the production of pig iron nuggets was obtained after a residence time of 40 minutes. The pig iron nuggets produced had chemical and physical properties similar to blast furnace pig iron. They were liquid-state products, and the slag was completely separated from the metal.

Laboratory study related to the production and properties of pig iron nuggets

Pig iron nuggets were produced in a laboratory-scale furnace at Michigan Technological University. The process was intended to replicate Kobe Steel's ITmk3 direct ironmaking process. These nuggets were produced from pellets that were made from a mixture of iron oxide, coal, flux and a binder and heated in a furnace with a chamber temperature of 1450{sup o}C. The pellets then self-reduced to produce a solid, high-density, highly metallized (96.5% Fe) pig iron. During the nugget production process, a separate liquid slag phase formed that cleanly separated from the molten metal. The physical and chemical properties of the pig iron nuggets were similar to pig iron produced by blast furnaces, which is distinct from direct reduced iron (DRI).

Concept Ship Design for the Iron Nugget Trade

The projected growth in production of pig iron nuggets on the Iron Range of northeastern Minnesota provides new opportunities for marine transportation on the Great Lakes. The shipping of this higher-value commodity necessitates low freight rates and minimum inventory costs. This paper examines viable ship design concepts to provide competitive transportation solutions.