Direct Reduction Plants Research Articles

Direct Reduction Plant Alternator Synchronization Using DC Motor and Synchronous Generator with Complete Reduced Machines Transient

Direct Reduction Plant alternator synchronization using D.C. motor and synchronous generator with complete reduced machines transient is presented. This is very significance in the industrial world. Direct Reduction plant is an iron making process plant for the new era which utilizes natural gas to reduce iron ore to produce Direct Reduced Iron used in steel industry. An alternator is an electrical generator that converts mechanical energy into AC electrical energy. Synchronization is connection of an alternator into the grid in parallel with many other alternators that is live of constant voltage and frequency. Transient stability is one of the major factors for proper operation of the Direct Reduction plant production systems that lead to major system collapses. The stress on Direct Reduction plant machines systems is increasing day by day, due to faults, economic and environmental pressures, sudden load change, deviation of active power and frequency. This phenomenon constitutes negative threat to Direct Reduction plant stability. The study was carried out to examine the capacity and transient stability on the Direct Reduction plant machines to withstand disturbance while quality of service is maintained. The effect of improper phase condition upon the synchronizing process, phase sequence of three phase power line, direct current excitation effect upon the power deliver by alternator, power delivered by an alternator upon the torque delivered by the prime mover. The challenges were solved and analyzed using individual machine with the help of accurate step by step integration and Electrical Transient Analyzer Program MatLab software. Swing equation was solved using advanced Runge-Kutta’s method. An experiment was conducted in Electrical Engineering laboratory and machines transient stability of the plant was improved by 64 percent averagely. The results were depicted graphically for machines dynamic behavior studies and recommended for Technician and Engineers in steel and related industries

Carbon Footprint Assessment of Hydrogen and Steel

Hydrogen has the potential to decarbonize a variety of energy-intensive sectors, including steel production. Using the life cycle assessment (LCA) methodology, the state of the art is given for current hydrogen production with a focus on the hydrogen carbon footprint. Beside the state of the art, the outlook on different European scenarios up to the year 2040 is presented. A case study of the transformation of steel production from coal-based towards hydrogen- and electricity-based metallurgy is presented. Direct reduction plants with integrated electric arc furnaces enable steel production, which is almost exclusively based on hydrogen and electricity or rather on electricity alone, if hydrogen stems from electrolysis. Thus, an integrated steel site has a demand of 4.9 kWh of electric energy per kilogram of steel. The carbon footprint of steel considering a European sustainable development scenario concerning the electricity mix is 0.75 kg CO2eq/kg steel in 2040. From a novel perspective, a break-even analysis is given comparing the use of natural gas and hydrogen using different electricity mixes. The results concerning hydrogen production presented in this paper can also be transferred to application fields other than steel.

Review of Life Cycle Assessments for Steel and Environmental Analysis of Future Steel Production Scenarios

The steel industry is focused on reducing its environmental impact. Using the life cycle assessment (LCA) methodology, the impacts of the primary steel production via the blast furnace route and the scrap-based secondary steel production via the EAF route are assessed. In order to achieve environmentally friendly steel production, breakthrough technologies have to be implemented. With a shift from primary to secondary steel production, the increasing steel demand is not met due to insufficient scrap availability. In this paper, special focus is given on recycling methodologies for metals and steel. The decarbonization of the steel industry requires a shift from a coal-based metallurgy towards a hydrogen and electricity-based metallurgy. Interim scenarios like the injection of hydrogen and the use of pre-reduced iron ores in a blast furnace can already reduce the greenhouse gas (GHG) emissions up to 200 kg CO2/t hot metal. Direct reduction plants combined with electrical melting units/furnaces offer the opportunity to minimize GHG emissions. The results presented give guidance to the steel industry and policy makers on how much renewable electric energy is required for the decarbonization of the steel industry.

Carbon Footprint and Energy Transformation Analysis of Steel Produced via a Direct Reduction Plant with an Integrated Electric Melting Unit

The production of flat steel products is commonly linked to highly integrated sites, which include hot metal generation via the blast furnace, basic oxygen furnace (BOF), continuous casting, and subsequent hot-rolling. In order to reach carbon neutrality a shift away from traditional carbon-based metallurgy is required within the next decades. Direct reduction (DR) plants are capable to support this transition and allow even a stepwise reduction in CO2 emissions. Nevertheless, the implementation of these DR plants into integrated metallurgical plants includes various challenges. Besides metallurgy, product quality, and logistics, special attention is given on future energy demand. On the basis of carbon footprint methodology (ISO 14067:2019) different scenarios of a stepwise transition are evaluated and values of possible CO2equivalent (CO2eq) reduction are coupled with the demand of hydrogen, electricity, natural gas, and coal. While the traditional blast furnace—BOF route delivers a surplus of electricity in the range of 0.7 MJ/kg hot-rolled coil; this surplus turns into a deficit of about 17 MJ/kg hot-rolled coil for a hydrogen-based direct reduction with an integrated electric melting unit. On the other hand, while the product carbon footprint of the blast furnace-related production route is 2.1 kg CO2eq/kg hot-rolled coil; this footprint can be reduced to 0.76 kg CO2eq/kg hot-rolled coil for the hydrogen-related route, provided that the electricity input is from renewable energies. Thereby the direct impact of the processes of the integrated site can even be reduced to 0.15 kg CO2eq/kg hot-rolled coil. Yet, if the electricity input has a carbon footprint of the current German or European electricity grid mix, the respective carbon footprint of hot-rolled coil even increases up to 3.0 kg CO2eq/kg hot-rolled coil. This underlines the importance of the availability of renewable energies.Graphical

Economic evaluation of low-carbon steelmaking via coupling of electrolysis and direct reduction

The transition from fossil-based primary steel production to a low-emission alternative has gained increasing attention in recent years. Various schemes including Carbon Capture and Utilization (CCU) and Carbon Direct Avoidance (CDA) via hydrogen-based as well as electrochemical routes have been proposed. With multiple technical analyses being available and technical feasibility being proven by first pilot plants, pathways towards commercial market entry are of increasing interest. While multiple publications on the economic feasibility of CCU are available, data on CDA approaches is scarce. In this work an economic model for the quantification of production cost as well as CO2 emission mitigation cost is presented. The approach is characterized by a seamless integration with a flowsheet-based process model of a direct reduction-based crude steel production plant detailed in a previous work and allows for the investigation of multiple economic aspects. Firstly, the gradual transition from the natural gas-based state-of-the-art direct reduction towards a fossil-free hydrogen-based reduction is analyzed. Furthermore, a comparison between the more mature technology of low-temperature electrolysis and a potentially more efficient solid oxide electrolysis (SOEL) is given, highlighting the potential of SOEL technology. The conducted forecast to 2050 shows that SOEL-based CDA offers lower production cost when technological maturity is reached. Based on the results of the economic assessment possible legislative support mechanisms are studied, showing that legislative actions are necessary to allow for market entry as well as for sustainable and economically feasible operation of fossil-free direct reduction plants.

Carbon footprint of scenarios towards climate-neutral steel according to ISO 14067

Within this paper, new findings of the potential of four considered intermediate solutions towards a primary climate-neutral steel production are reported. (1) Injection of natural gas into a blast furnace, (2) injection of hydrogen into a blast furnace, (3) natural gas-based direct reduction with subsequent input of the hot briquetted iron (HBI) in a blast furnace, and (4) hydrogen-based direct reduction with subsequent input of the hot briquetted iron in a blast furnace.The current study is a carbon footprint assessment applied to the product hot-rolled coil (HRC) according to the ISO norm 14067:2019. A cradle to gate approach is used including the production of raw materials to the production of hot-rolled coil. To define a reference point, a carbon footprint of hot-rolled coil produced via a typical blast furnace – basic oxygen furnace (BF-BOF) route is presented. The basic data set is based on primary data from the integrated site of thyssenkrupp Steel Europe AG (tkSE), year 2018. Within a novel approach, this base line is enhanced by integrating metallurgical models from the literature. Thereby all changes of the complex material and energy supply chain of an integrated site and of the upstream chain are reported. The carbon footprint of each process unit is presented in detail so that optimization potentials are identified, which impacts are analysed within a sensitivity analysis. A holistic comparison of using hydrogen in a blast furnace to using hydrogen in a direct reduction plant is presented and delivers important findings. This can help steel producers to maximize the efficiency of hydrogen use.Since the focus of this paper lies on the comparison of steel production routes and the assessments for all considered scenarios are based on the same methodologies and databases the sensitivity of made assumptions on the deltas between these scenarios is much weakened than the sensitivity of absolute values. That's one of the reasons why, the conclusions of this paper, which are referred to the plant of tkSE, can be transferred to other production sites, as well. The presented results can help decision-makers to know the potentials of possible intermediate solutions towards a climate-neutral steel production and how the potentials can be maximized.The carbon footprint of the product hot-rolled coil is 2.1 t CO2eq/tHRC following the recycled content approach and 0.82 t CO2eq/tHRC following the end-of-life recycling approach. The reduction potential for the carbon footprint is about 4 % for injecting natural gas into a blast furnace and about 9 % for injecting hydrogen into a blast furnace. The hydrogen is produced via electrolysis driven by a renewable German energy mix, year 2018. Using hot briquetted iron (HBI) within a blast furnace leads to a reduction potential between 5 % and 12 % for natural gas based-HBI and between 10 % and 17 % for H2-based HBI. The reduction potential strongly depends on the iron feedstock, which is replaced by the hot briquetted iron. Between 4.5 and 7.0 kg CO2eq/kg H2 are avoided by injecting hydrogen into a blast furnace, and about 5.4 kg CO2eq/kg H2 are prevented if the hydrogen is injected into a direct reduction plant.

Assessing industrial symbiosis potential in Emerging Industrial Clusters: The case of Persian Gulf Mining and metal industries special economic zone

Industrial Symbiosis (IS) is a means for sustainable cluster development. The first consideration for implementing IS in a cluster is to identify technical opportunities for exchanging waste material and or energy. However, the definition and methods for assessing the technical potential of IS are not elaborated in the literature. This research proposes a method to evaluate IS potential that considers different system boundaries. The method allows for explicitly reflecting current and expected developments at plant and cluster level. The suggested method was applied to the Persian Gulf Mining and Metals Special Economic Zone (PGSEZ) in Iran. The case study shows that expanding the system boundaries to include the waste flows inside steelmaking and direct reduction plants could result in an 8% increase in available waste heat. Heat recovery possibilities outside the cluster boundaries offered 118 MW cooling plus 368 MW heating potential compared to 158 MW demand for electricity in the cluster. Furthermore, less than 20% of generated by-products could currently be reused in the cluster, while theoretically all by-products could be utilized today in other industries such as cement and ceramic. These findings support the use of IS as a way to open new perspectives for EIC development policies.

Evaluation of biomass-based production of below zero emission reducing gas for the iron and steel industry

The present paper focuses on the production of a below zero emission reducing gas for use in raw iron production. The biomass-based concept of sorption-enhanced reforming combined with oxyfuel combustion constitutes an additional opportunity for selective separation of CO2. First experimental results from the test plant at TU Wien (100 kW) have been implemented. Based on these results, it could be demonstrated that the biomass-based product gas fulfills all requirements for the use in direct reduction plants and a concept for the commercial-scale use was developed. Additionally, the profitability of the below zero emission reducing gas concept within a techno-economic assessment is investigated. The results of the techno-economic assessment show that the production of biomass-based reducing gas can compete with the conventional natural gas route, if the required oxygen is delivered by an existing air separation unit and the utilization of the separated CO2 is possible. The production costs of the biomass-based reducing gas are in the range of natural gas-based reducing gas and twice as high as the production of fossil coke in a coke oven plant. The CO2 footprint of a direct reduction plant fed with biomass-based reducing gas is more than 80% lower compared with the conventional blast furnace route and could be even more if carbon capture and utilization is applied. Therefore, the biomass-based production of reducing gas could definitely make a reasonable contribution to a reduction of fossil CO2 emissions within the iron and steel sector in Austria.

Hydrogen Steelmaking: Technology Options and R&D Projects

Reducing CO2 emissions by 80 to 95% by mid-century is the central climate goal and requires both energy suppliers and industry to prepare themselves and explore new pathways together. For the industry, transport, and energy sectors, “green”—that is CO2 free—hydrogen can make an important contribution to decarbonisation. The vision in steelmaking is to shift from carbon via bridge technologies based on natural gas, as is already the case at the direct reduction plant of voestalpine in Texas, to finally the greatest possible use of green hydrogen and renewable energy. The precondition is the provision of sufficient energy from renewable sources at competitive prices. Construction of the new PEM electrolysis pilot plant for the production of CO2 neutral hydrogen and with research on other breakthrough technologies like hydrogen plasma smelting reduction are important steps towards the long-term technology transformation in the steel industry in the coming decades.

Further Opportunities of Competitiveness Improvements for Direct Reduction Plants

Even though the Midrex Process is the most successful direct reduction process in the world, additional improvements are still possible. This paper discusses some of those additional opportunities for improvements of Direct Reduction plants in order to increase the plant competitiveness and/or flexibility. Such plant improvements have either already been implemented in the latest projects or were recently developed by Midrex and/or Primetals Technologies. Some of these plant improvements are: Adjustable Carbon Technology (ACTTM)—Increase of carbon content depending on HBI off-taker/user requirements; Process Water Degasser—Degassing of process water from CO2 to improve water quality and lower operation/maintenance cost; Slurry Treatment by Chamber Filter Presses—Efficient dewatering of slurry from clarifier with low operating and maintenance cost; DRIpaxTM Carbon and Metallization Prediction—Improvement of plant operation by stable product quality; DRIpaxTM DR Plant Expert System—Increased support of operation team. Such improvements have plenty of benefits including reduction of the OPEX costs, increase in oxide to product yield, improve the operation/maintenance, and/or increase the availability/flexibility of a Midrex plant. These improvements can be retrofitted in existing plants or implemented for new direct reduction plants.

Detailed Modeling of the Direct Reduction of Iron Ore in a Shaft Furnace.

This paper addresses the modeling of the iron ore direct reduction process, a process likely to reduce CO2 emissions from the steel industry. The shaft furnace is divided into three sections (reduction, transition, and cooling), and the model is two-dimensional (cylindrical geometry for the upper sections and conical geometry for the lower one), to correctly describe the lateral gas feed and cooling gas outlet. This model relies on a detailed description of the main physical–chemical and thermal phenomena, using a multi-scale approach. The moving bed is assumed to be comprised of pellets of grains and crystallites. We also take into account eight heterogeneous and two homogeneous chemical reactions. The local mass, energy, and momentum balances are numerically solved, using the finite volume method. This model was successfully validated by simulating the shaft furnaces of two direct reduction plants of different capacities. The calculated results reveal the detailed interior behavior of the shaft furnace operation. Eight different zones can be distinguished, according to their predominant thermal and reaction characteristics. An important finding is the presence of a central zone of lesser temperature and conversion.

Optimization of Midrex Direct Reduced Iron Use in Ore‐Based Steelmaking

Iron and steel industry contributes by more than 5% to the global anthropogenic CO2 emissions, so new ways to reduce the emissions in this industrial sector must be found. In order to facilitate a transition to more sustainable production concepts, economic factors must be considered. The potential of using direct reduced iron from the Midrex process, based on shaft furnace technology, as a partial substitute of pellets in a blast furnace was studied in the paper. Mathematical models of the different operations in a steel plant, including the shaft furnace, form the basis of the model of the system, which was optimized by non‐linear programming with respect to costs. The main objective was to analyze the prerequisites for an economically feasible operation of a steel plant integrated with a direct reduction plant under different raw material prices and varying costs of CO2 emission allowances. The results illustrate the conditions under which it would be beneficiary in a steel plant to integrate the shaft furnace in the operations. The implications of the integration on the overall CO2 emissions of the plant are also discussed.

Pilot Scale Froth Flotation Studies To Upgrade Nigerian Itakpe Sinter Grade Iron Ore To A Midrex-Grade Super-Concentrate

The sinter grade concentrate of Itakpe iron ore found in the North Central Kogi state of Nigeria with cumulative undersize of 6.34% and 2.12% passing 90μm and 63μmsieves, respectively, and that assayed 63.63% Fe, 5.90% silica and 0.72% alumina was ground in ball mill to produce a pilot plant froth flotation feed with cumulative undersize of 74.37% and 42.94% for 90μm and 63μm sieves, respectively. The ball mill discharge was then treated in three stages of roughing, cleaning and re-cleaning in a pilot plant froth flotation process line and the products obtained gave 66.66%, 66.51%, 65.44% (Fe) and total acid (silica and alumina) contents of 4.22%, 4.39%, 5.15%, respectively, for the three stages. The super-concentrate obtained also gave 81.13%, 55.19% and 30.57% cumulative undersize for 90μm, 63μm and 45μm sieves, respectively. The results obtained showed that the roughing stage of the flotation process produced a super-concentrate that fall in the range of 66% to 68% for use in midrex direct reduction plant at the Delta Steel Plant, Nigeria. The lowest total acid gangue content of 4.22% was also obtained for the roughing stage, indicating that the two subsequent processes of cleaning and re-cleaning were not needed. Although, the total acid content of 4.22% for the roughing stage product slightly exceeds the upper limit of 3.50% for the Midrex process, Itakpe sinter grade concentrates with up to 5% acid gangue has been successfully used at the Delta Steel Plant Midrex plant.

Coke formation possibility during production of reducing gas in large scale direct reduction plant

For the production of synthesis gas utilised in Midrex direct reduction plants, catalytic steam/CO2 hydrocarbon reforming in tubular reformer is the major process. Owing to the high heat input through the Midrex reformer tube wall, the endothermic nature of reforming reactions, low mass velocity of feed gas and large tube diameter, the catalyst bed is exposed to considerable axial and radial temperature gradients. These radial concentration and temperature gradients may create local areas with potential for carbon formation. To investigate this phenomenon, a rigorous two-dimensional model is developed for simulating the operation of a Midrex reformer which applies a dual catalyst loading profile. Both process side and furnace side have been included in this integrated model. Simulation results are in good agreement with available data from an actual plant. Using this model, a thermodynamic approach is applied to recognise zones in which the risk of carbon formation is high inside the reformer tubes. The results show that the first half of tubes, both in centre and near the wall, is critical from carbon forming point of view. Furthermore, the model shows that how a certain catalyst loading profile will affect the operation of the reformer.

04/01630 Modeling and simulation of syngas unit in large scale direct reduction plant: Farhadi, F. et al. Ironmaking and Steelmaking, 2003, 30, (1), 18–24

04/01630 Modeling and simulation of syngas unit in large scale direct reduction plant: Farhadi, F. et al. Ironmaking and Steelmaking, 2003, 30, (1), 18–24

Modelling and simulation of syngas unit in large scale direct reduction plant

The production of reducing gas is usually a bottleneck to capacity increase in direct reduction plants. Modelling and simulation of reducing gas production result in better design and operation of these plants. In the present work, a mathematical model is discussed that relates to a Midrex reformer, which is different from conventional steam reformers in some respects. Both process side and furnace side have been included in an integrated model. Simulation results have been tested against available data from an actual plant. The model predictions have been found to be reasonably accurate. The effects of three process variables, feed gas temperature, feed gas pressure and excess air, on reformer performance have been investigated. Simulation results confirm that an increment in feed gas temperature is the most effective method of increasing performance.

DEVELOPMENT OF A HIGH REDUCIBILITY ACID PELLET AT IMEXSA

Imexa is an integrated steel slab producer located on the west coast of Mexico, in the town of Lazaro Cardenas, Michoacan. Because of increasing slab production, demand for pellets to use in the direct reduction plants prompted Imexsa to reactivate its partially completed pelletizing plant project in 1994. Pilot tests were carried out in 1995, at Peña Colorada, Colima, one of the four then-existing Mexican pelletizing plants. Various hematite minerals from Brazil were used as feed. These were mixed with limestone, dolomite, coke, and pellet fines in order to obtain fluxed pellets which would be used to feed two direct reduction processes. At the end of 1996, Imexsa's pelletizing plant began to operate with the aim of producing 3.5 million metric tons of pellets per year. The percentage of metallization (PM) reached on reducing these oxide pellets during initial use in direct reduced iron (DRI) production was 84.9%, a low value. Further research with several mineral mixtures resulted in a binary basicity (B 2) of ∼0.35 and PM of ∼94.0%.

BRAZILIAN IRON FORMATIONS AND THEIR GEOLOGICAL SETTING

In the Quadrilatero Ferrifero banded iron formations (BIFs) are metamorphic jaspilites named itabirites that occur in the Paleoproterozoic platformal sequence of the Minas Supergroup (2.6 - 2.12 Ga). Several types of itabirites can be defined according to primary (sedimentary) and secondary features, acquired under the influence of metamorphic, deformational and weathering processes. A complex interaction of primary and secondary processes was responsible for the anomalous concentration of iron in high-grade deposits. In the Carajas Range in the central north of Para, BIF-related iron ores are weathered anchimetamorphic jaspilites with preserved primary textures and structures, making up approx. 18 billion tons of ore with 66 % Fe. The jaspilites are weakly deformed and extend over 2500 km 2 in the eastern portion of the region in the Archean Grao-Para Group (2.7-2.6 Ga) between metavolcanic rocks. The Urucum District in Mato Grosso do Sul, at the Brazilian - Bolivian border, displays the youngest Brazilian banded iron formation as flat- lying anchimetamorphic jaspilites of Proterozoic age (ca. 0.6 Ga). These are associated with fine glacial marine sediments and manganese layers that outcrop as inselbergs locally called Morrarias. Urucum jaspilites belong to the group of Rapitan-Type iron formations and can be distinguished from the Carajas jaspilites by the presence of glacial-clastic components and nodules of uncertain origin. Tropical weathering as well as primary concentration are the principal processes responsible for the high grade iron ores with more than 63% Fe and reserves of approximately only 100 million tons, that are very appreciated for direct reduction plants.

BRAZILIAN IRON FORMATIONS AND THEIR GEOLOGICAL SETTING

In the Quadrilátero Ferrífero banded iron formations (BIFs) are metamorphic jaspilites named itabirites that occur in the Paleoproterozoic platformal sequence of the Minas Supergroup (2.6 - 2.12 Ga). Several types of itabirites can be defined according to primary (sedimentary) and secondary features, acquired under the influence of metamorphic, deformational and weathering processes. A complex interaction of primary and secondary processes was responsible for the anomalous concentration of iron in high-grade deposits. In the Carajás Range in the central north of Pará, BIF–related iron ores are weathered anchimetamorphic jaspilites with preserved primary textures and structures, making up approx. 18 billion tons of ore with 66 % Fe. The jaspilites are weakly deformed and extend over 2500 km2 in the eastern portion of the region in the Archean Grão-Pará Group (2.7-2.6 Ga) between metavolcanic rocks. The Urucúm District in Mato Grosso do Sul, at the Brazilian - Bolivian border, displays the youngest Brazilian banded iron formation as flatlying anchimetamorphic jaspilites of Proterozoic age (ca. 0.6 Ga). These are associated with fine glacial marine sediments and manganese layers that outcrop as inselbergs locally called Morrarias. Urucúm jaspilites belong to the group of Rapitan-Type iron formations and can be distinguished from the Carajás jaspilites by the presence of glacial-clastic components and nodules of uncertain origin. Tropical weathering as well as primary concentration are the principal processes responsible for the high grade iron ores with more than 63% Fe and reserves of approximately only 100 million tons, that are very appreciated for direct reduction plants.

Metal Dusting of Stainless Steels

'Metal dusting' is a catastrophic disintegration of metals (Fe, Ni, Co)occurring in carburizing atmospheres typical of reformer plants, direct reduction plants, and many chemical and petrochemical processes.