Ton Of Liquid Steel Research Articles

Comparing the decarbonization benefit provided by waste-based hydrogen routes to green steel production process: an analytical model

In the present context of global decarbonization, the steelmaking sector plays a key role. It is indeed one of the so-called hard-to-abate sectors. The high emissions from steelmaking depend on the use of the Blast Furnace-Basic Oxygen Furnace (BF-BOF) route, which generates 1.8 tCO2eq per ton of Liquid Steel (LS). The production of direct reduced iron (DRI) to power an electric arc furnace is currently the most adopted solution to achieve the decarbonization goals. This alternative, based on the use of natural gas, offers a decarbonization potential of about 34% compared to the BF-BOF route. The most promising alternative, however, consists of using electrolysis-based hydrogen (H2) to produce DRI. This solution would drastically reduce direct and indirect process emissions but requires a radical energy transition. In the current transition phase, waste-based H2 production routes could be attractive, but their potential need to be evaluated with respect to the steelmaking process. To this concern, the objective of the present work is to assess the decarbonization potential of three waste-based H2 production routes (i.e., gasification, incineration and anaerobic digestion-based) with respect to the electrolysis-based steelmaking route. An environmental analytical model was therefore developed to evaluate the total (i.e., direct, indirect, and avoided) greenhouse gases emissions associated with the production of 1 ton of LS by employing the different routes. A sensitivity analysis was also carried out to understand the benefit provided by each waste-based H2 alternative in the current energy transition phase. The results obtained confirmed the need for radical emission reductions from electricity generation to make electrolysis-based H2 production environmentally favorable and revealed a high decarbonization potential for waste-based routes in the current energy transition phase.

Calcium looping in the steel industry: GHG emissions and energy demand

The development of innovative solutions to decarbonize hard-to-abate sectors is a priority challenge in the quest to mitigate climate change. The GHG emission mitigation potential of the carbon capture Calcium Looping process (CaL) is investigated in this work. Two steelmaking routes are modeled: a blast furnace and a basic oxygen furnace (BF-BOF), and a direct reduction process and an electric arc furnace (DR-EAF), both of which are coupled with CaL technology. The carbon footprints of the two systems were evaluated, through an eco-design approach, with the aim of quantifying the GHG emissions and identifying the hotspots of the emissions. DR-EAF was found to be characterized by lower GHG emissions than BF-BOF (0.9 t vs 2.1 t CO2eq per tonne of liquid steel produced), as it is intrinsically more efficient and less carbon intensive. For this reason, the adoption of the CaL technology resulted to be more effective when applied to the BF-BOF, as it led to a reduction in GHG emissions of up to 66%, with respect to baseline plant configuration without the CaL system. The primary energy demand increased considerably by the integration of CaL in BF-BOF and this would be amplified in a future scenario dominated by renewable energy resources. We also remarked the importance of the CaL technology being circular to reduce and reuse the spent material deployed for CO2 sequestration. This work ends with a parametric analysis that points out the importance of the timescale of climate change metrics on the evaluation of the carbon footprint.

Can methane pyrolysis based hydrogen production lead to the decarbonisation of iron and steel industry?

Decarbonisation of the iron and steel industry would require the use of innovative low-carbon production technologies. Use of 100% hydrogen in a shaft furnace (SF) to reduce iron ore has the potential to reduce emissions from iron and steel production significantly. In this work, results from the techno-economic assessment of a H2-SF connected to an electric arc furnace(EAF) for steel production are presented under two scenarios. In the first scenario H2 is produced from molten metal methane pyrolysis in an electrically heated liquid metal bubble column reactor. Grid connected low-temperature alkaline electrolyser was considered for H2 production in the second scenario. In both cases, 59.25 kgH2 was required for the production of one ton of liquid steel (tls). The specific energy consumption (SEC) for the methane pyrolysis based system was found to be 5.16 MWh/tls. The system used 1.51 MWh/tls of electricity, and required 263 kg/tls of methane, corresponding to an energy consumption of 3.65 MWh/tls. The water electrolysis based system consumed 3.96 MWh/tls of electricity, at an electrolyser efficiency of 50 KWh/kgH2. Both systems have direct emissions of 129.4 kgCO2/tls. The indirect emissions are dependent on the source of natural gas, pellet making process and the grid-emission factor. Indirect emissions for the electrolysis based system could be negligible, if the electricity is generated from renewable energy sources. The levellized cost of production(LCOP) was found to be $631, and $669 respectively at a discount rate of 8%, for a plant-life of 20 years. The LCOP of a natural gas reforming based direct reduction steelmaking plant of operating under similar conditions was found to be $414. Uncertainty analysis was conducted for the NPV and IRR values.

Decarbonization of the Iron and Steel Industry with Direct Reduction of Iron Ore with Green Hydrogen

Production of iron and steel releases seven percent of the global greenhouse gas (GHG) emissions. Incremental changes in present primary steel production technologies would not be sufficient to meet the emission reduction targets. Replacing coke, used in the blast furnaces as a reducing agent, with hydrogen produced from water electrolysis has the potential to reduce emissions from iron and steel production substantially. Mass and energy flow model based on an open-source software (Python) has been developed in this work to explore the feasibility of using hydrogen direct reduction of iron ore (HDRI) coupled with electric arc furnace (EAF) for carbon-free steel production. Modeling results show that HDRI-EAF technology could reduce specific emissions from steel production in the EU by more than 35 % , at present grid emission levels (295 kgCO2/MWh). The energy consumption for 1 ton of liquid steel (tls) production through the HDRI-EAF route was found to be 3.72 MWh, which is slightly more than the 3.48 MWh required for steel production through the blast furnace (BF) basic oxygen furnace route (BOF). Pellet making and steel finishing processes have not been considered. Sensitivity analysis revealed that electrolyzer efficiency is the most important factor affecting the system energy consumption, while the grid emission factor is strongly correlated with the overall system emissions.

Increasing in effi ciency of steel refi ning process by using production waste

The results of the possibility for using of spent ANF-6-1 fl ux for electroslag remelting and breakage of spent silicon carbide abrasive wheels in the smelting of 20GFL steel are presented. Noticeable advantage of the experimental smelting technology is shown. Saving of expensive materials, reduction of harmful impurities in the metal and increase in the desulfurization rate from 0.0004 to 0.0007 %/min are noted. The use of spent ANF6-1 fl ux for electroslag remelting made it possible to reduce the duration of melting, the consumption of slagforming materials and reducing agents. There is also decrease in electricity consumption by 11 kW/h per ton of liquid steel. Increase in the plastic characteristics and impact toughness of 20GFL steel is shown when using the experimental melting technology in comparison with the current one. At the same time, the strength characteristics of steel remained at the same level. The economic effect at using of secondary materials in the smelting of 20GFL cold-resistant steel is 430...450 rubles per ton of liquid steel.

The impact of hot metal temperature on CO2 emissions from basic oxygen converter.

Recycled steel is a key material for sustainable development. However, not all steel demand can be met by recycling, and therefore, new metallic iron must be introduced in the global cycle. The transformation of iron oxides into steel requires carbon which is oxidized into CO2. This paper focuses on the basic oxygen furnace (BOF) where molten iron is converted into liquid steel. In order to assess the effect of molten iron temperature on CO2 emissions, the process has been modelled using mass and energy balances. Model results show that, for a typical converter charge, a slight increase of 10 °C can lead to a direct reduction of 0.006 t of CO2 per ton of liquid steel. A total variation of 0.17 t of CO2 per ton of liquid steel is found depending on plant strategy and process constraints. Finally, different actuation levers for carbon mitigation are assessed. It can be concluded that operation and modelling improvements should be jointly addressed to exploit their full potential for carbon footprint reduction.

Assessment of hydrogen direct reduction for fossil-free steelmaking

Climate policy objectives require zero emissions across all sectors including steelmaking. The fundamental process changes needed for reaching this target are yet relatively unexplored. In this paper, we propose and assess a potential design for a fossil-free steelmaking process based on direct reduction of iron ore with hydrogen. We show that hydrogen direct reduction steelmaking needs 3.48 MWh of electricity per tonne of liquid steel, mainly for the electrolyser hydrogen production. If renewable electricity is used the process will have essentially zero emissions. Total production costs are in the range of 361–640 EUR per tonne of steel, and are highly sensitive to the electricity price and the amount of scrap used. Hydrogen direct reduction becomes cost competitive with an integrated steel plant at a carbon price of 34–68 EUR per tonne CO2 and electricity costs of 40 EUR/MWh. A key feature of the process is flexibility in production and electricity demand, which allows for grid balancing through storage of hydrogen and hot-briquetted iron, or variations in the share of scrap used.

Refining fluxes for metallurgical melts based on waste materials of the aluminium industry

ABSTRACTWaste slag is a major source of environmental pollution within the metallurgical industry. In the steel industry, about 100–150 kg of waste slag is produced in making one tonne of liquid steel in addition to that produced during ironmaking. In the aluminium industry, about 2–4 tonnes of waste materials are generated during the production of one tonne of aluminium. The waste products from these two industrial sectors are of particular concern because of the sheer volume and causticity of the materials. Extensive studies have been carried out at the University of Toronto to investigate potential applications for these metallurgical waste products. Studies have included: (1) desulphurization of hot metal and liquid steel using calcium aluminate fluxes made from the dross of aluminium electrolysis and remelting; (2) ferronickel desulphurization as well as simultaneous desulphurization and dephosphorization using red mud and white mud generated during alumina extraction from bauxite; and (3) recovery of nickel from spent catalysts generated by the petroleum industry. The results confirm that the application of waste byproducts from the aluminium industry, as a basis for refining fluxes in the steel industry, could be beneficial from technical, economical and environmental perspectives, thus generating social benefits for both industrial sectors.

Theoretical Estimation of Peak Arc Power to Increase Energy Efficiency in Electric Arc Furnaces

This research work introduces the concept of “useful arc power” and the thermal model, first introduced by Dittmer and Krüger, to establish the arc length at any stage of the heat in Alternate Current Electric Arc Furnaces (AC-EAF), based on the estimation of the fraction of the energy transferred to the metallic load by radiation. Radiation is the most effective way to transfer heat in an arc furnace in presence of metallic scrap (bore-in and early meltdown). On the other hand, if the arc is not adequately covered with slag, radiation is extremely dangerous to the furnace integrity. When the furnace is fully loaded, scrap protects the walls and cooling panels and then arc radiation must be maximized. To increase energy efficiency, and at the same time reduce circuit power losses, the arc length should be controlled. However, arc instability prevents to increase radiation, as desired, and a compromise must be reached between arc length and arc stability. In this work AC-EAF electric circuit is modeled and analyzed under different heat stages. Electrodes, anode and cathode, fall regions can be considered as energy losses and their associated power may be deducted for the estimation of the “useful arc power” and for the definition of the operational currents in the heat process, particularly during flat bath conditions (late meltdown and refining). As a result of the present study it is proved that current setpoints play an important role for energy saving at any stage of the heat. Finally, experimental results obtained from an industrial steel factory validate this approach to optimize the electrical energy consumption per ton of liquid steel in AC-EAF.

Modeling Study of the Influence of Subflux Controller of Turbulence on the Molten Steel Flow in Tundish

The objective of the study is to diagnose the current condition of the two-strand tundish. The investigated object is a “T”-type tundish. The nominal capacity of the tundish is 7.5 tonne of liquid steel. By the mathematical simulation, fluid flow and heat transfer of molten-steel in a tundish of a billet caster under different conditions (bare tundish and tundish with flow control device) are analyzed. Three variants of subflux controller of turbulence configurations in the tundish are tested. Numerical simulations of are carried out with the finite-volume commercial code FLUENT using the realizable k- turbulence model. Liquid steel velocity, temperature, turbulent kinetic energy and Residence Time Distribution (RTD) characteristic have been obtained as a result of mathematical calculations. The RTD curve is used to estimate the different volumes such as plug volume, dead volume and mixed volume inside the tundish. The ratio of mixed to dead volume, which indicates the mixing capability of a tundish, is estimated.

Iron and steel manufacturing technologies in India: estimation of CO2 emission

Iron and steel manufacturing is heavily energy intensive and polluting. CO2 emissions per tonne of liquid steel have been estimated for six steel manufacturing technologies which are commercially available in India. © 1997 John Wiley & Sons, Ltd.

Effects of Sponge Iron on the Electric Arc Furnace Operation.

Data obtained on a 70-ton UHP electric arc furnace have been used for studying the effects of the sponge iron proportion in the metallic charge on important technological parameters of the steelmaking operation. The results obtained show that an increase in the sponge iron proportion leads to an increase in the consumptions of electric power, graphite electrodes, furnace refractories, lime and deoxidizers. The metallic yield decreases, whereas the slag weight per ton of liquid steel, the total ferrous oxide in the slag and the oxygen content of the bath increase with increasing sponge iron in the charge. The effects of metallization of the direct reduced pellets on power consumption and metallic yield are the reverse of the effects of the sponge iron proportion. The levels of the residual metals Cu, Ni and Cr, and the concentrations of the impurities P and S decrease with increasing sponge iron in the furnace feed. The use of sponge iron also improves the segregation of C, S and N in the steel. The yield point and tensile strength of hot-rolled plain steel bars decrease slightly, whereas elongation increases with increasing sponge iron in the charge. The actual steelmaking time decreases when the sponge iron proportion grows.

The feasibility of using waste heat boilers to recover energy from the exhaust gases of electric arc furnaces

Energy can be rejected in the waste gases of an UHP electric arc furnace at rates of up to about 15 MW, accounting for 200 kWh per tonne of liquid steel. The possibility of recovering a significant proportion of this energy as steam using a wast heat boiler has been investigated. The options of using the steam to satify the in-works demand and generating electricity are being considered. Extensive measurements of the conditions existing in the waste gas stream have been made throughout the steelmaking cycle for furnace practices involving oxygen blowing, continuous charging and supplementary firing with oxy-fuel burners. Various practical implications of the use of a waste heat boiler have been studied. These include the location of the boiler, the accretion of solid matter on tubes, the effect of the presence of the boiler on gas cleaning and the control of furnace extraction to achieve optimum performance. A case study involving a 180 tonne furnace used to produce special steels has shown that the payback of the capital involved in installing a boiler to generate sufficient steam to satisfy the works' base load would be less than two years, under the conditions prevailing during the project. The economic appraisal of electricity generation is being evaluated, but the initial indications are that the return of capital is not attractive if generation facilities do not already exist.

An integrated steelworks energy model

This model enables the quantity of each form of energy used or produced within the steelworks to be calculated. A simple model of each of the main operating areas of the works has been devised enabling the quantities of each of the fuels used or produced in that area to be calculated for any given operating conditions. The total quantity of any form of energy utilised within the works can be found, for any given sequence of operating conditions, by summing the quantities produced or consumed in each unit operation and relating all quantities to the production of one tonne of liquid steel. The main emphasis in this study has been concentrated on the processes up to and including steel production.