Search Results (9)

Phosphorus is an essential resource for numerous industrial applications. However, its uneven global distribution makes Europe heavily dependent on imports. Recovering phosphorus from waste streams is therefore crucial for improving resource security. The FlashPhos project addresses this challenge by developing a process to recover phosphorus from sewage sludge, in which phosphorus-rich slag is produced in a flash reactor and subsequently reduced in a Submerged Arc Furnace (SAF). In this process, approximately 250 kg/h of sewage sludge is converted into slag, which is further processed in the SAF to recover about 8 kg/h of white phosphorus. This work focuses on the development of a computational model of the SAF, with particular emphasis on slag behaviour. Due to the extreme operating conditions, which severely limit experimental access, a numerically efficient three-dimensional CFD model was developed to investigate the internal flow of the three-phase, AC-powered SAF. The model accounts for multiphase interactions, dynamic bubble generation and energy sinks associated with the reduction reaction, and Joule heating. A temperature control loop adjusts electrode currents to reach and maintain a prescribed target temperature. To further reduce computational cost, a novel simulation approach is introduced, achieving a reduction in simulation time of up to 300%. This approach replaces the solution of the electric potential equation with time-averaged Joule-heating values obtained from a preceding simulation. The system requires transient simulation and reaches a pseudo-steady state after approximately 337 s. The results demonstrate effective slag mixing, with gas bubbles significantly enhancing flow velocities compared to natural convection alone, leading to maximum slag velocities of 0.9–1.0 m/s. The temperature field is largely uniform and closely matches the target temperature within ±2 K, indicating efficient mixing and control. A parameter study reveals a strong sensitivity of the flow behaviour to the slag viscosity, while electrode spacing shows no clear influence. Overall, the model provides a robust basis for further development and future coupling with the gas phase. Full article

The effect of ore pre-heating on the operation of a 300 kVA Submerged Arc Furnace (SAF) for high carbon ferromanganese (HCFeMn) alloy was investigated. The two types of Mn ores from the Kalahari Manganese Field (KMF) were used in the investigation (Ore #1 and Ore #2). Quartz and coke sourced from South Africa were used as a fluxing agent and a reductant, respectively. The Mn ores, reductant and fluxing agent were delivered to Mintek with a size range of +6–20 mm and were sent to our in-house laboratories to determine the chemical and physical properties. The samples were taken for Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), combustion method (LECO), proximate analysis and quantitative X-ray diffraction (QXRD). A newly designed and constructed pilot facility at Mintek was used in the investigation. The facility included a 1 t/h rotary kiln coupled to an electric arc furnace supplied with an alternating current (AC) with a 300 kVA tap-changer transformer. The main aim of the investigation was to demonstrate the effect of ore pre-heating to 600 °C on the furnace energy consumption and CO/CO₂ emissions. The experimental approach adopted involved feeding Mn ore to establish baseline operating conditions, followed by feeding of Mn ore pre-heated with a rotary kiln to compare operational parameters. The pilot campaign experienced several operational challenges but there were periods of stable operation that enabled data collection for furnace energy consumption and CO/CO₂ emissions. The effect of pre-heating the ore to 600 °C on the SAF energy consumption and CO/CO₂ emissions was demonstrated successfully and revealed that energy savings and reduction in furnace CO₂ emissions is achievable. Pre-heating Mn ore to 600 °C lowered the furnace energy consumption by an average of 22.5% and CO₂ emissions by an average of 37%. The campaign also achieved an overall manganese recovery of 86%. Operating the furnace with hot feed increased the heat losses through the roof by 300% compared to heat losses observed during cold feed. There were also no significant changes in the furnace electrical parameters observed between the two feed modes. Full article

This article describes elements of the know-how of using carbon electrodes produced using the technology of molding around a rod when smelting silicon metal. Application of our know-how will dramatically increase the competitiveness of silicon metal production. Experts’ concerns regarding the use of such electrodes were that such electrodes have a through axial hole. This significantly reduces the mechanical strength of such electrodes, which can presumably lead to problems associated with the breakage of the working side of the electrode, which is immersed in the smelting space of the furnace under the charge layer. Industrial testing of such electrodes was carried out in a 30 MVA furnace of “Tau-Ken Temir” LLP. During testing, we used an approach previously developed by our team for working with a furnace in the process of smelting silicon metal. In particular, we used an interval between top treatments of about 30 min and adhered to the principles of balanced smelting, i.e., provided a balance between the intensity of the uniform supply of the charge into the furnace and the current active electrical power. Industrial testing carried out over four weeks confirmed the stability of the operation of cheaper carbon electrodes with a through axial hole. The recovery of silicon into finished products was also improved to 88–89% and the specific energy consumption was reduced to 11.2–12.1 MWh/t of silicon metal from the initial value 14,752 MWh/t. Thus, we received additional evidence for the effectiveness of our approach in furnace operating compared to an approach based on the ultimate provision of gas and permeability of the furnace top due to excessively intense processing of the top and an uncontrolled, uneven supply of charge to the furnace. Full article

This review aims to show the significance of the use of secondary carbon bio-carriers for iron and steel production. The term ‘secondary carbon bio-carriers’ in this review paper refers to biomass, torrefied biomass, biochar, charcoal, or biocoke. The main focus is on torrefied biomass, which can act as a carbon source for partial or complete replacement of fossil fuel in various metallurgical processes. The material requirements for the use of secondary carbon bio-carriers in different metallurgical processes are systematized, and pathways for the use of secondary carbon bio-carriers in four main routes of steel production are described; namely, blast furnace/basic oxygen furnace (BF/BOF), melting of scrap in electric arc furnace (scrap/EAF), direct reduced iron/electric arc furnace (DRI/EAF), and smelting reduction/basic oxygen furnace (SR/BOF). In addition, there is also a focus on the use of secondary carbon bio-carriers in a submerged arc furnace (SAF) for ferroalloy production. The issue of using secondary carbon bio-carriers is specific and individual, depending on the chosen process. However, the most promising ways to use secondary carbon bio-carriers are determined in scrap/EAF, DRI/EAF, SR/BOF, and SAF. Finally, the main priority of future research is the establishment of optimal parameters, material quantities, and qualities for using secondary carbon bio-carriers in metallurgical processes. Full article

Self-reducing briquettes made with waste (silica fume, iron ore and charcoal fines) from the FeSi75 industry were studied. The objective was to determine if these briquettes could be used as a complementary load in submerged arc furnaces (SAF). Characterization of this waste was performed and the briquettes were produced without and with binders (Portland cement, hydrated lime, and sodium silicate), in accordance with the proportion of binder (2.50%; 5.00%; 7.50% and 10.00%). These self-reducing briquettes were tested for apparent density, porosity, shatter strength and resistance to hot degradation. To select the best briquettes, pre-established set points were used based on the scientific literature. Within this framework, only two treatments—out of a total of 52—met all the requirements of eligibility. In the two types of briquettes, the binder of solid silicate (5.00 and 7.50%) was produced with 15.00% of water. The briquettes have the following characteristics: apparent density: 1165 kg/m³ and 1247 kg/m³ respectively, porosity: 46.2% and 46.0%; shatter strength (1.50 m): 99.3% and 98.8%; and resistance to thermal degradation: 81.2% and 82.5%. Reduction tests to investigate the self-reducing character, under different heating temperatures (1750, 1800, 1850 and 2000 °C) were performed on these two treatments. The metallic phases that were identified by SEM/EDS analyses were Si, FeSi, FeSi₂, thus obtaining the production of FeSi50 and FeSi75, in addition to the formation of the SiC and slag. It was found that the values for SiO gas formation are in the same range as in the industrial FeSi furnace. From the results, it is possible to verify the potential for carbothermal reduction of these residues, but it is punctuated by the need for more research aimed at optimizing the mass percentage in the formulation. Full article

Since the European Union defined ambitious CO₂ emission targets, low-carbon-emission alternatives to the widespread integrated blast furnace (BF)—basic oxygen furnace (BOF) steelmaking strategy—are demanded. Direct reduction (DR) with natural gas as the reducing agent, already an industrially applied technology, is such an alternative. Consequently, the melting behavior of its intermediate product, i.e., direct reduced iron (DRI), in either an electric arc furnace (EAF) or a submerged arc furnace (SAF), is of great interest. Based on the conditions in these aggregates, a test series to experimentally simulate the first few seconds after charging DRI was defined. DRI samples with different carbon contents and hot briquetted iron (HBI) were immersed in high- and low-carbon melts as well as high- and low-iron oxide slags. The reacted samples were quenched in liquid nitrogen. The specimens were qualitatively evaluated by investigating their surfaces and cross sections. The dissolution of carbon-free DRI progressed relatively slowly and was driven by heat transfer. However, carbon, present either in the DRI sample or in the melt, not only accelerated the dissolution process, but also reacted with residual iron oxide in the pellet or the slag. Full article

The submerged arc furnace (SAF) has become the equipment of choice to produce manganese ferro-alloy. Furnace operators aim to reduce the cost of production by better understanding the role played by the various raw materials involved in the process. Coke is one of the key raw materials fed into the SAF; it plays three key roles in electric furnaces: as a reducing agent, as a source of carbon found in the alloy, and as a resistive element facilitating heat generation in the furnace. The heat generated plays two key functions in the furnace: ensuring both the metal and the slag have a sufficient low viscosity, and providing the heat required to support endothermic reactions. This study investigated the ambient-temperature and high-temperature resistivity characteristics of coke made from single-source coals. The measurement of coke resistivity was performed using the Kelvin (four-point) technique. The results showed a statistically significant difference in mean resistivity between cokes made from different coals. It was observed that coke resistivity generally decreased with increasing temperatures. Raman spectroscopy showed that the structural order of coke changes with increasing temperature. Full article

Biocoke has the potential to reduce the fossil-based materials in metallurgical processes, along with mitigating anthropogenic CO₂- and greenhouse gas (GHG) emissions. Reducing those emissions is possible by using bio-based carbon, which is CO₂-neutral, as a partial replacement of fossil carbon. In this paper, the effect of adding 5, 10, 15, 30, and 45 wt.% biomass pellets on the reactivity, the physicomechanical, and electrical properties of biocoke was established to assess the possibility of using it as a fuel and reducing agent for a blast furnace (BF) or as a carbon source in a submerged arc furnace (SAF). Biocoke was obtained under laboratory conditions at final coking temperatures of 950 or 1100 °C. Research results indicate that for BF purposes, 5 wt.% biomass additives are the maximum as the reactivity increases and the strength after reaction with CO₂ decreases. On the other hand, biocoke’s physicomechanical and electrical properties, obtained at a carbonization temperature of 950 °C, can be considered a promising option for the SAF. Full article

Very little research on Søderberg electrodes has been published in the journal peer reviewed public domain. The main aim of this work is to characterise a Søderberg electrode that was cut off approximately 0.5 m below the contacts shoes of a submerged arc furnace. Additionally, the characterisation data can be used to verify if Søderberg electrode models accurately predict important electrode characteristics. The operational history (slipping, current, and paste levels) proved that the case study electrode was a representative specimen. The characterisation results indicated no significant electrical resistivity, degree of graphitisation (DOG), and bulk density changes from 0.7 to 2.7 m on the non-delta side (outward facing), while these characteristics changed relatively significantly on the delta side (inward facing) of the electrode. The area where the submerged arc would mostly like jump off the electrode had the lowest resistivity, as well as highest DOG and bulk density. No significant difference in porosity as a function of length below the contact shoes were observed; however, slight increases occurred near the perimeters. It was postulated that oxidation of carbon resulted in increased pore volumes near the electrode perimeter. No significant difference in compressive breaking strength was observed over the electrode area investigated. Full article