Academic literature on the topic 'Direct reduction (Metallurgy)'

For quite a long time efforts have been made to develop processes for producing iron i.e. steel without employing conventional procedures - from ore, coke, blast furnace, iron, electric arc furnace, converter to steel. The insufficient availability and the high price of the coking coals have forced many countries to research and adopt the non-coke-consuming reduction and metal manufacturing processes (non-coke metallurgy, direct reduction, direct processes). This paper represents a survey of the most relevant processes from this domain by the end of 2000, which display a constant increase in the modern process metallurgy.

A new mineral processing and metallurgy technology was proposed, which was that the ferro-nickel concentrate was prepared from laterite ore by coal-based direct reduction. Under the reduction of cheap reductant and the catalysis of composite additives, the effects of coal-based direct reduction were enhanced and the ferro-nickel was extracted. The optimal conditions were followed that the alkalinity was 0.87, and the roasting temperature was 1150°C, and the roasting time is 2.5 hours. The recovery rate of nickel was 86.7% and the nickel content of ferro-nickel concentrate was 5.3%.

A significant research effort within the CSIRO Light Metal Flagship is aimed at developing new processes for the manufacture of (semi-finished) titanium products based on a powder metallurgy approach. The main driver for considering alternative processing and consolidation techniques to conventional ingot metallurgy is improved techno-economics associated with a reduction in processing steps and increased productivity via rapid consolidation of parts. In this respect, CSIRO has developed a process to manufacture sheet products utilising direct powder rolling; the process consists of cold rolling the powder feedstock to a green strip, which is then rapidly heated and hot rolled to consolidate the material completely. The work reported here was an investigation into the feasibility of fabricating Ti-6Al-4V strip by a blended elemental powder metallurgy route. The development of microstructures occurring during the processing and heat treatment steps has been studied. The generic roles of some process, material and heat treatment variables on the tensile properties and homogeneity of the final material have been assessed and are discussed in this paper.

The article is devoted to the analysis of mutual direct investments in Russia and the EU in steel industry and nonferrous metal industry after the beginning of the global financial crisis. The author notes a great importance of the EU market for Russian companies in their foreign expansion. In particular in steel industry the EU market plays a key role as the North American market does. In nonferrous metal industry the importance of the EU market is reduced due to lack of developed raw material sources within the EU and due to the diversification of foreign activity of Russian companies. The author notes that a reduction of mutual direct investments began after 2008. Russian companies have focused their activities on their own enterprises in Russia because of high debt leverage. The crisis has also resulted in an appearance of new crisis strategies of Russian metallurgical companies for European assets. These crisis strategies include sale of assets, suspension of production and strategic partner search. Traditional strategies of foreign investing were relevant during the crisis. The modernization of production was the most applied strategy. Buying up of core assets was also applied. European investments in Russia were made mainly by creating new production capacity frequently including joint ventures with Russian companies. European investors along with investments introduced new technologies and equipment into Russian metallurgy. The article notes that because of the crisis the number of capital investment projects including European companies was reduced. The author notes that the EU will remain the key area for Russian metallurgical companies if the situation in global metallurgical markets will improve and sanctions against Russia will be lifted off. Acknowledgments. The article has been supported by a grant of the Russian Science Foundation (project № 14-28-00097 “The optimization of Russian foreign investment ties in the context of deteriorating relations with the EU”).

Nowadays a significant number of alternative processes of ferrous metals production have been developed, it differs in the principles of operation, as well as the design arrangement of the aggregates. In general, "alternative" processes of ferrous metals production can be divided into 4 groups. The processes of the first group (the production of sponge iron in direct reduction units with remelting in electric arc furnaces) are based on the use of reduction gases (CO, H2 or a mixture of them) or coal for the reduction. Depending on this, they have different principles of work and design. Shaft processes of direct reduction, based on the use of reduction gases, have the dominant positions in the global production of HBI. This is due to the design simplicity of these units, the reliability of their work and the low content of harmful impurities (S, P) in the products. The principle of the processes of the second group (production of carbon semi-products in smelting reduction units with blowing in BOF) involves the reduction of iron ore with power-generating coal at temperatures of 1400-1600 °C and obtaining hot metal. The processes of this group can use as a charge partially reduced iron ore materials (Corex processes, Finex, Tecnored, etc.), as well as raw iron ore (processes Hismelt, Romelt, Ausiron). More than forty processes in various countries have been developed and tested to substitute blast furnace process. Currently, there are 7 Corex units in the world (2 - China, 4 - India, 1 - South Africa) with a total annual productivity of about 7 million tons; 3 Finex units (2 in Korea, 1 in India) with an annual productivity of about 3.5 million tons. The development of processes for the direct production of steel from iron ore (the third group) is currently focused on the processing of iron-containing waste (sludge, scale, dust iron ore) to crude steel. Examples include: the process of jet-emulsion refining, production of high carbon steel in rotary inclined furnaces or perspective direct electrolysis processes of iron ore (MOE), the development of which is at the initial stages of laboratory research. Continuous processes for the production of crude steel from hot metal (the fourth group), due to difficulties in controlling a continuous process, high consumption of refractories, low economic indexes and, most importantly, the rapid growth of ladle treatment of steel, could not compete with the LD-process and are currently hardly used. It should be said about the prospects of the considered alternative processes for the ferrous metals production. The processes of direct reduction have proven their competitiveness, the prospects of their development is determined by the need of electric steelmaking in high-quality metal charge. At the moment smelting reduction processes of ferrous metals production are not the real competitors to BF process and so far they should be considered only as an addition to it. However, if the price of metallurgical coke continues to grow, then the further spread of smelting reduction processes is possible. The processes of the third group are directed to the utilization of iron-containing metallurgical wastes and dust iron ores, but the development of majority of these processes is on its initial stages, their prospects will be determined by economic efficiency. Continuous steelmaking processes with use of hot metal as a charge could not clearly prove their superiority to the well-known steelmaking processes, at this stage their prospects are rather doubtful.

The low carbon metallurgy technology based on the high-value utilization of biomass is considered as the key development orientation of green ironmaking. In this paper, a pyrolysis coupling technology of biomass tar and iron ore powder is proposed for the reduction of iron ore. Tar is degraded efficiently due to the synergy effects respectively through oxidation of iron oxides and the catalytic action of reduced iron, and simultaneously the reduction of iron oxide to metallic iron. Representative tar components including vanillin, naphthalene, and catechol were selected as tar model compounds. The various reaction conditions on the reduction degree of iron ores was investigated, which include the type of tar component, the pyrolysis temperature, and the ratio of reactants. According to the results, the optimal relationship between tar degradation and reduction of iron ore was identified. It can be found that under the catalytic effects of iron ore fines, the degradation efficiency of the three model compounds followed the following order: naphthalene > vanillin > catechol. Naphthalene owned the better reduction ability. The highest reduction degree of the product reached to 78.5% at 800 °C for 30 min.

Hydrogen has received much attention in the development of direct reduction of iron ores because hydrogen metallurgy is one of the effective methods to reduce CO2 emission in the iron and steel industry. In this study, the kinetic mechanism of reduction of hematite particles was studied in a hydrogen atmosphere. The phases and morphological transformation of hematite during the reduction were characterized using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. It was found that porous magnetite was formed, and the particles were degraded during the reduction. Finally, sintering of the reduced iron and wüstite retarded the reductive progress. The average activation energy was extracted to be 86.1 kJ/mol and 79.1 kJ/mol according to Flynn-Wall-Ozawa (FWO) and Starink methods, respectively. The reaction fraction dependent values of activation energy were suggested to be the result of multi-stage reactions during the reduction process. Furthermore, the variation of activation energy value was smoothed after heat treatment of hematite particles.

Utilization of titanium components made by powder metallurgy methods has had limited acceptance largely due to the high cost of titanium (Ti) powder. There has been renewed interest in lower cost economical powders and several Ti reduction methods that produce a particulate product show promise. This talk summarizes work done at Oak Ridge National Laboratory to consolidate these economical powders into mill products. Press and sinter consolidation, hot isostatic pressing (HIP) and direct roll consolidation to make sheet have been explored. The characteristics of the consolidated products will be described as a function of the consolidation parameters.

AbstractLaser cladding is a well-established technique, with the majority of prior numerical modelling work focused on delivery and melt pool behaviour of powder-based processes. This research presents new investigations into optimised laser beam shaping for the unique characteristics of wire-based processes, where direct substrate heating, as well as heat transfer between the wire and substrate, is important. The value of this subject is the improved deposition rates and dense metallic structures that can be achieved by wire-based deposition processes compared to powder-based material delivery. The within-wire temperature distribution (AISI 316 stainless steel), the heat transfer and direct heating of the substrate (mild steel) are modelled via heat transfer simulations, with three laser beam irradiance distributions. This analysis identified the removal of localised high-temperature regions typically associated to standard Gaussian distributions, and the improved substrate heating that a uniform square beam profile can provide. Experiments using pre-placed wire and a 1.2 kW CO2 laser were analysed using cross-sectional optical microscopy to provide model validation and evidence of improved wire-substrate wetting, while maintaining favourable austenitic metallurgy in the clad material. A key finding of this work is a reduction, from 480 to 190 W/mm2, in the required irradiance for effective melt pool formation when changing from a Gaussian distribution to a uniform square distribution. This also provided a 50% reduction in total energy. The potential improvements to energy efficiency, cost reductions and sustainability improvements are recognised and discussed.

This project examined the reduction and formation of cementite from hematite and titanomagnetite ores and cementite stability. The aim of the project was to develop further understanding of cementite stability under conditions relevant to direct ironmaking and the mechanism of cementite decomposition. The reduction of hematite and ironsand by hydrogen-methane-argon gas mixtures was investigated from 600??C to 1100??C. Iron oxides were reduced by hydrogen to metallic iron, which was carburised by methane to form cementite. The hematite ore was reduced more quickly than the ironsand. Preoxidation of the ironsand accelerated its reduction. Hematite was converted to cementite faster than preoxidised ironsand. The decomposition of cementite formed from hematite was investigated from 500??C to 900??C. This cementite was most stable at temperatures 750-770??C. The decomposition rate increased with decreasing temperature between 750??C and 600??C and with increasing temperature above 770??C. The stability of cementite formed from pre-oxidised titanomagnetite was studied from 300??C to 1100??C. This cementite was most stable in the temperature range 700-900??C. The rate of decomposition of cementite increased with decreasing temperature between 700??C and 400??C and with increasing temperature above 900??C. Cementite formed from ironsand was more stable than cementite formed from hematite

A method of producing steel that is not used in Sweden today is direct reduction using natural gas, a method which could has enormous potential in the future of steelmaking. Historically, steelmaking prioritized productivity and profitability. However, other aspects such as safety, sustainability, and environmentally friendliness have become increasingly important to Swedish steelmakers. This study evaluates the usage of natural gas to  directly reduce iron ore into the porous form known as iron sponge, then finally processing that sponge into crude steel. The technology available today is assessed through a literature review, then two calculative data-based model: using DRI sponge in a traditional integrated steelmaking line or replacing steel scrap with it in an electric arc furnace. While this technology is used in many regions where natural gas is plentiful, it has not yet been used in Sweden. Now, when the Swedish natural gas network is expanding and the vehicular transportation of liquid natural gas is becoming more and more viable, it is a prime situation to evaluate direct reduction in Sweden. While models require assumptions and estimations, they suggest that DRI will absolutely be a viable option in the years to come. Integrated plant operators can reduce their immense carbon emissions for a reasonable price, while DRI sponge melting in an electrical arc furnace can either help steelmakers escape the volatile scrap market or be used to replace the blast furnace as a whole in the future.
En metod för att producera stål som inte används i Sverige idag är direkt reduktion med hjälp av naturgas, en metod som har en enorm potential i framtida ståltillverkning. Historiskt har ståltillverkningen prioriterat produktivitet och vinst, men säkerhet, hållbarhet, och miljövänlighet har blivit områden mer och mer viktiga för svenska ståltillverkare. Den här studien utvärderar användningen av naturgas för att direkt reducera järnmalm till den porösa formen känd som järnsvamp, och sen bearbeta den till primärt stål. Teknologin som flnns idag utvärderas genom en litteraturstudie, vars data beräknas till två scenariomodeller: användningen av järnsvamp i ett traditionellt integrerat stålverk eller genom att ersätta stålskrot med järnsvamp i ljusbågsungen. Den här teknologin används redan idag i regioner där naturgas är lättillgängligt, men har hittills inte använts i Sverige. Men nu när Sveriges naturgasnät byggs ut och fordonstransporterad flytande naturgas blir mer och mer kostnadseffektiv så är det lämpligt att utvärdera direkt reduktion i Sverige. Modellerna kräver antaganden och uppskattningar, men de pekar på att direkt reducering av järnmalm kommer att vara en genomförbar metod för ståltillverkning i en nära framtid. Integrerade masugnslinjer kan minska sina enorma koldioxidutsläpp till ett rimligt pris, och järnsvampssmältning i ljusbågsugn kan hjälpa ståltillverkare att undanfly den instabila stålskrotsmarknaden eller användas för att helt ersätta masugnsproduktion i framtiden.

M.Ing. (Mechanical)
The goal of this study was to determine whether a SLIRN direct reduction process could be modelled with a neural network. The full name of the SLIRN process is the Stelco, Lurgi, Republic Steel, and National Leadprocess. A parallel goal was to identify, and test an alternative method to reduce the dimensionality of a model. A neural network software package named Process Insights was used to model the process. Two independent data reduction methods were used along with various Process Insights functions, to build, train, and test models. The best model produced by each of the two data reduction methods was used to report on. The results showed that a SLIRN direct reduction process could be modelled successfully with a neural network. The large number of variables normally identified with such a process can be reduced without significant loss in model performance, The results also showed that the removal of the most significant variable does not affect the model accuracy significantly, which bodes well for the fault tolerance of the model in terms of individual sensor failures. The Process Insights functions important to the modelling process were highlighted.

The blast furnace process for the reduction of iron ore to pig iron faces problems such as emission of air pollutants, high investment cost and the current major problem of decreasing supplies of coke. Coke is used in large quantities to promote a combination of direct and indirect reduction within the furnace. Due to the lack of good coking coal within South Africa, and dwindling supplies worldwide, new iron-making processes, are being developed using coal and/or natural gas to replace coke as the reductant. The new processes allow efficient use of carbon, fed in the form of coal pellets (coalbased processes) or natural gas (gas-based processes), as the reducing agent. Presently, most coal-based processes Use an excess of coal, up to 500% stoichoimetric addition, and are run at temperatures up to ±1200°C, although reduction tends to proceed at ±850°C. This project developed a low temperature process using mixed pellets of fine waste iron oxide and fine domestic coal with a natural carbonaceous binder (a by-product from local pulping industry). Reduction tests performed on composite pellets in a tube furnace and thermobalance indicated, upon analysis by X-Ray Diffraction and Scanning Electron Microscope, that reduction occurred gradually at 900°C. Implementing induction heating of bulk pellets reduced heating times substantially. Induction heating also resulted in direct reduced iron [DRI] containing 75 - 80% metallic iron. Energy consumption based on coal usage amounted to 23.71 GJ/ton DRI, which compares with the calorific consumption of most coal-based processes, i.e. coal consumption range between 15 and 25 GJ/ton DRI. Energy consumed during induction heating amounted to 9.94 GJ/ton DRI, as electricity. This energy consumption value does not take into account the efficiency of the primary energy required to generate electricity.
Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

As the world population has exceeded 7 billion in 2011, the global awareness of sustainability arises more than ever since we are facing unprecedented challenges in energy, water, material and climate change, in order to sustain our current and future generations on this planet. The Guardian has named the Iron Bridge opened in 1781 across the River Severn, Shropshire, UK as the cradle of the modern world, which is the world's first cast-iron bridge and remains as the enduring symbol of the Industrial Revolution (Guardian, 2009). Ever since, in the spanning of 250 years, iron and steel have been the cornerstone of modern industries from developed countries to developing ones especially for those which are still experiencing their major urbanization process. Nevertheless, iron and steel making are among the most raw material-dependent and energy intensive industries with large gaseous pollutants, CO2 and waste generations in the world. Therefore there is a pressing need to solve these resource and environmental problems associated with the iron and steel making. This work addresses a number of challenges stated above by focusing on the improvement of the overall sustainability of this highly energy-intensive industry via (1) utilizing inexpensive iron ore tailings to enhance the material sustainability, (2) CO2 reduction by mineral carbonation using its own solid waste stream, i.e., iron and steel slags, and (3) slag valorization through the use of carbonated slags as sustainable construction materials. This work begins with the study of an ironmaking plant using the direct reduced iron (DRI) process, which is a molten iron production method utilizing fluidized bed and melter-gasifier technologies. This technology allows the direct production of the molten iron using the inexpensive iron ore tailings and the non-coking coal, during a gas-solid reaction in the fluidized bed. Practically, a higher percentage of the fine particles (i.e., iron ore tailings) is favored to mix in the feedstock because it is cheaper than the traditionally used coarse particles (i.e., bulk and fine iron ores). The challenge of this novel technology is attributed to the entrainment of the fine particles during the gas-solid fluidization. Since the electrostatic phenomenon was significant during the particulate fluidization systems which might affect the particle entrainment, the electrostatic charge generation and accumulation were investigated for binary and quaternary particulate systems. Specifically, the effect of the addition of two different iron ore tailings (i.e., hematite and magnetite) in the fluidized bed was studied in terms of particle-particle interactions, electrostatics, and entrainment rates. The behaviors of different particulate systems were found to be highly dependent on the chemical and physical properties of the particles. The results suggested that the enhanced electrostatic forces between the fine and coarse particles due to the electrostatic charging during the fluidized bed operation retained the fines to some extent and the sintering of the fine particles could happen on the surface of the coarse particles during the iron ore reduction. Therefore, for this fluidized bed based DRI process, iron ore tailings are proved to be able to replace the coarse iron ores to the extent that fine particles will sinter but not be entrained and thus the overall cost of raw materials could decrease. In iron and steel making, limestone and dolomite are also mixed in the feedstock to remove the impurities of the iron ores, mostly silica, which forms slag as a silicate-based material in the downstream of this process. Slags of different types have been reused as cement clinker, aggregate, road base and fertilizer. Recently, iron and steel slags have also been deemed as alternatives for mineral sequestration because these slags are similar to natural Ca/Mg-bearing silicate minerals. The accelerated weathering of natural minerals or industrial wastes is an environmentally benign route to thermodynamically stabilize carbon. Thus, another study of this work is fixing the CO2, especially emitted from the iron and steel plant, into the slag, a solid waste generated from the same processing stream. In particular, the stainless steel slag has been a focus since its application in construction materials has been limited due to the high content of FeO and the environmental concern of heavy metals leaching (e.g., Cr). Along with the iron and steel making, the cement industry is also among the largest industrial CO2 emitters. Mixing carbonated slags as a filler material in the cement mortar while guaranteeing the overall quality of the cementitious material could reduce the usage of limestone and the carbon emissions from limestone calcination and reduce energy input during the cement production. In this study, the production of environmentally benign cementitious material was coupled with the direct carbonation of stainless steel slag. Compressive strength, exothermic behavior and leaching behavior of the mixed cement mortar were investigated. Particularly, mixing 10 wt% of the direct carbonated stainless steel slag sample prepared at 30 °C in a Portland cement did enhance the compressive strength of the cement mortar. Also, the mixing retarded the hydration and overall setting time. Finally, the Cr leaching of the cement mortar with the addition of the direct carbonated stainless steel slag was minimized. Thus, the iron and steel industry and cement industry should collaborate, to minimize their overall material input, energy usage and carbon emission jointly. During the direct carbonation, stainless steel slag and CO2 flows are introduced into the solvent simultaneously. Whereas for the two-step process, calcium ions are extracted from the solid matrix into an aqueous phase, and then the CO2 is bubbled through and reacts with the Ca. The two-step route allows optimizing the conditions for both the dissolution and the carbonation. Moreover, the precipitated end products (e.g., precipitated calcium carbonates, PCC) from the two-step process, normally with higher quality compared to direct carbonated slags, can be adapted for various industrial and construction applications. However, the overall reaction is constrained by the kinetics of the stainless steel slag dissolution. Thus several organic and inorganic chelating agents were applied in order to accelerate the dissolution. Some of these agents were found to be desirable for the dissolution of stainless steel slag at different pH via the differential bed study. Ligand concentration and temperature affected the extent of the extraction in the batch reactor. For the carbonation step, PCC from the modeled chemical solution and the dissolved stainless steel slag solution were non-identical, which was also affected by the reaction pH and temperature. The properties of the PCC prepared in the batch reactor and the bubble column reactor were also found to be dissimilar. Thus, for an iron and steel plant that adopts the two-step carbonation of slags for CO2 reduction, the end products could be engineered by tuning the reaction conditions to meet different end-user requirements. On the other hand, there have been significant efforts to reduce the cost of the two-step carbonation, including the utilization of value-added byproducts like iron oxide. In particular, silicate minerals or industrial waste often contain 5~20 wt% of Fe and by dissolving the iron into aqueous phase, a variety of Fe-based materials can be synthesized by precipitation. In this work, Fe-based catalysts were synthesized from serpentine and stainless steel slag (SSS) and applied to the biomass-to-hydrogen conversion via an alkaline thermal treatment pathway. The synthesized Fe-based materials were compared with the purchased hematite and magnetite and the reduced Fe-based catalyst derived from SSS was found to be catalytically active. This suggests an opportunity to produce inexpensive catalysts from the solid waste of the iron and steel making. Finally, a novel iron making scheme based on a fluidized bed DRI system was proposed by this study. It combined all the studies above that inexpensive iron ore tailings were used as a feedstock for the iron production, slags were utilized for sequestering CO2 and ended as filler materials for cement mortar. Preliminary economical and life cycle assessment was investigated based on the current scale of an existing industrial plant. An economically, environmentally and ecologically favored iron, steel and cement production system could be potentially achieved with improved overall material sustainability and carbon footprint.

Systematic, well-designed experimental research and standardized documentation is a starting point for explaining the outcome of experiments and comparative analyses, whether within single experimental research or a wider frame of comparison with other research. This contribution presents a sequence of research procedures that served as a basis for the design and implementation of experiments related to bloomery iron production procedures. A proposal for the method of documentation is made with the aim of combining all general functional parameters relevant to the procedures of ore preparation and direct process of reduction in the reconstruction of a smelting furnace, based on personal experiences and the current state of experimental research related to iron production. The objective is to give a structured basic template of main parameters that should be recorded and reported when performing experiments related to the mentioned procedures. The hope is to bring forward a layout that should be upgraded and further developed based on specific research questions one could have.