Steelmaking Slag Research Articles

Phosphorus removal from steelmaking slag by selective leaching in the steel pickling waste liquor

Steelmaking slag and steel pickling waste liquor (SPWL) are two kinds of by-products in steel plants. The existence of phosphorus (P) in steelmaking slag is the main factor affecting its reuse within the steelmaking process. To remove P from steelmaking slag with a low-cost method, selective leaching was proposed by using SPWL as a leaching agent. SPWL generally contains a small amount of Fe3+ ions, and thus the effect of Fe3+ content in SPWL on the dissolution behavior (especially P element) of steelmaking slag was investigated, as well as the pH value and steelmaking slag type. The dissolution ratios of P from various slags in the SPWL containing 500 ppm Fe3+ exceeded 95 % at pH 1.5 while those of Fe, Mn, and Al were very low, exhibiting satisfied selective leaching of P. Increasing pH value and Fe3+ content (in SPWL) resulted in a decreasing P dissolution ratio while exerting an insignificant effect on the dissolution of other elements. The FeHPO4+ was predicted as the predominant species during leaching and the transformation of FeHPO4+ to FePO4 could be present. When the SPWL containing 800 ppm Fe3+ was used, FePO4 was observed in the residues after leaching at pH 2.0, resulting in a worse removal of P from slag. However, the residues including massive valuable components had an extremely low P content after leaching in the SPWL containing 500 ppm Fe3+ at pH 1.5, which can be used as a flux in the metallurgical process. To ensure a high P removal rate from steelmaking slag and to prevent FePO4 precipitation during leaching, a relatively low pH and Fe3+ content in the SPWL are necessary.

Performance assessment of sustainable asphalt concrete using steel slag, with an artificial neural network prediction of asphalt concrete behavior

This research evaluated the possibility of using Moroccan steelworks slag as a substitute for natural aggregates in asphalt mixtures, using chemical and mechanical analyses to demonstrate its compatibility with this application. Two granular mixtures, M1 and M2, were developed, incorporating respectively 15% and 25% natural sand (0/1.25) with slag aggregates to obtain granular mixtures complying with local standards. These mixtures were then tested with three different asphalt contents (4.7%, 5.2%, and 5.7%). Mechanical tests, including a gyratory compactor, Marshall stability, and Duriez strength, were carried out. In particular, the M1:5.2 and M2:5.2 mixtures met compaction criteria and showed remarkable Marshall Stability values, reaching 23.49 kN and 21.81 kN respectively. In comparison, the control mixtures only achieved a maximum stability of 11 kN. Thermal properties were also assessed, showing that the maximum thermal conductivity was achieved at an asphalt content of 5.2%. The slag-based mixtures, M1 and M2, showed higher thermal conductivity than the control mix M0, with maximum values of 0.74W/mK for M1 and 0.86W/mK for M2, compared with 0.56W/mK for M0. The overall results show that the M1 and M2 mixtures had improved thermal and mechanical properties compared with the M0 control mix. Artificial neural network (ANN) modelling was carried out using Marshall Test data. It showed excellent performance in predicting the stability and flow properties of asphalt mixtures. These results suggest that incorporating steelmaking slag into asphalt concrete mixtures was an effective strategy for simultaneously improving their thermal and mechanical properties.

The influence of acid treatment on the adsorption‑structural characteristics of filtering materials created based on steelmaking slag

Many industrial enterprises use electroplating processes that lead to the formation of water containing heavy metal ions such as chromium, copper, zinc, nickel, and others. Such water is a dangerous source of environmental pollution. Most heavy metal ions belong to hazard classes I–II, they have carcinogenic and mutagenic properties, and have a cumulative effect.The literature analysis showed that there is positive experience in the use of steelmaking slags in the processes of cleaning contaminated water of various origins from heavy metals.The study examines the effect of acid activation on the adsorption‑structural characteristics of filtering materials created based on steelmaking slag. It is shown that during the interaction of some acids with slag, new crystallographic phases are formedon its surface, and contact with other acids leads to the leaching of ions and their transition to the aqueous phase. It has been established that during acid activation, the specific surface area increases by 57–132 times compared to the original material.

Enhancing the Dissolution of Spent MgO-C Refractory in Steelmaking Slag: Towards Utilization as a Steelmaking Flux

Enhancing the Dissolution of Spent MgO-C Refractory in Steelmaking Slag: Towards Utilization as a Steelmaking Flux

Scientific, technological, organizational and technical aspects of the production of building materials based on steelmaking slags

Scientific, technological, organizational and technical aspects of the production of building materials based on steelmaking slags

Engineering properties optimization of dispersive soil by calcium silicate waste—The role of steel-making slag

Steel slag (SS) is a byproduct that comes from the production of crude steel in alkaline oxidation furnaces. Resource utilization of steel slag, a calcium-silicon solid waste, is an urgent problem. This paper investigates a solid waste disposal method that applies different steel slag contents to modify dispersive soil. The engineering properties and modification mechanisms of dispersive soil specimens are studied and revealed by performing microstructure, mineral evolution, unconfined compressive strength (UCS), and tensile strength analysis. The pinhole test, mud ball crumb test (BCT), and mud cube crumb test (CCT) were carried out to determine the dispersivity of the soil specimens. Results show that when the steel slag content increases from 1% to 10%, the unconfined compressive strength and tensile strength increase by 176.05% and 75.40%, respectively. For soil specimens without curing time under 50 mm water head, the weight loss of the specimen with 10% steel slag content decreases by 72.03% compared to specimens with 1% steel slag content. Microstructural and mineralogical analyses indicate that the hydration reaction of steel slag changes the ionic composition of the soil and generates reaction products with effects such as filling and connection. To sum up, steel slag effectively improves water stability and mechanical properties of dispersive soil.

Utilization of steelmaking slag in cement clinker production: A review

The cement industry significantly contributes to global CO2 emissions, with a notable portion attributed to limestone calcination during cement clinker production. To promote carbon-neutral building practices, alternative approaches are being explored to replace raw materials in cement manufacturing and mitigate CO2 emissions. Steelmaking slag, enriched with noncarbonated CaO from limestone decarbonization during steel production, shows potential as a promising raw material for cement manufacture to reduce CO2. Despite their environmental benefits, most steelmaking slags are underutilized, with limited recognition of their CO2 mitigation potential. Moreover, challenges to using steelmaking slag as a raw material to manufacture cement clinker exist due to the mineral and chemical compositions of each slag type. This study explored potential pretreatment methods to enhance slag's performance as a cement raw material and the research on utilizing steelmaking slag, including blast furnace slag (BFS), Kanbara reactor (KR) slag, basic oxygen furnace (BOF) slag, electric arc furnace (EAF) slag, ladle furnace (LF) slag, and stainless slag, in cement clinker manufacture. Consequently, steelmaking slag could be used as a raw material to manufacture cement clinker to reduce CO2 emissions. However, additional research is needed, including slag pretreatment methods and cement clinker manufacturing process optimization.

Effect of MgO on Phase Structure and Evolution of Steelmaking Slag During Cooling

Effect of MgO on Phase Structure and Evolution of Steelmaking Slag During Cooling

Fundamental Aspects of Dissolution of Lime into Steelmaking Slags

Fundamental Aspects of Dissolution of Lime into Steelmaking Slags

Cooling Curves of Concentrated Alloys, Steelmaking Slag, and Lithium Iron Phosphate

AbstractOver the past few years, a variety of melting casting projects have been performed, in collaboration with industries and universities. Concentrated alloys and nonmetallic compounds were studied including high-Si cast iron, high-Mn steel, Al-added stainless steel, high-entropy alloy, Permalloy 80 Ni alloy, Stellite Co alloy, steelmaking slag, and lithium iron phosphate (LFP). A melt synthesis of LFP was developed. Cooling curves were measured using the thermal analysis cup method and differential thermal analysis. In addition, the phase diagrams of alloys were calculated using Thermo-Calc. This paper draws on some examples of the measured cooling curves to illustrate the thermal behaviors of melts, along with a quick review of each project.

Characteristics of flight trajectory and heat transfer of liquid steelmaking slag droplet during air quenching granulation process

Air quenching granulation of liquid steel slag is one of the most promising slag treatment technologies, as it effectively utilises the thermal properties of liquid slag while produces value-added slag products. To gain a deeper understanding of this process and explore the flying behaviour and heat transfer solidification characteristics of slag droplets, simulation and experiment on air quenching granulation of liquid steel slag were implemented separately. During this process, the slag droplets fly in parabola along various directions. The greater the slag flow rate is, the greater the resistance to the blowing air and the greater the airflow velocity loss rate are. With the increase of airflow velocity, the loss rate of airflow velocity decreases and the distance of the initial landing point of slag droplets increases. With the increase of nozzle height, the distribution space of air velocity field becomes wider. For the process of heat transfer and solidification of slag droplet, a zone of wake formed on the leeward side. The constant disturbance of the air in the zone of wake formed a vortex and accelerated the cooling of the slag droplet. The cooling rates of five points of the slag droplet are as follows: windward side > upper boundary ≈ lower boundary > leeward side > liquid core. When the particle size of slag droplets decreases from 2 to 0.5 mm, the cooling rate increases from 43 to 320°C/s. The granulation experiment reveals that the cooling process of the liquid slag involves three typical stages: the natural cooling stage before air quenching, the rapid flight cooling stage after air quenching and the cooling stage after slag bead's landing.

Valorization of steelmaking slag and coal fly ash as amendments in combination with Betula pubescens for the remediation of a highly As- and Hg-polluted mining soil

Soil pollution by As and Hg is a pressing environmental issue given their persistence. The intricate removal processes and subsequent accumulation of these elements in soil adversely impact plant growth and pose risks to other organisms in the food chain and to underground aquifers. Here we assessed the effectiveness of non-toxic industrial byproducts, namely coal fly ash and steelmaking slag, as soil amendments, both independently and in conjunction with an organic fertilizer. This approach was coupled with a phytoremediation technique involving Betula pubescens to tackle soil highly contaminated. Greenhouse experiments were conducted to evaluate amendments' impact on the growth, physiology, and biochemistry of the plant. Additionally, a permeable barrier made of byproducts was placed beneath the soil to treat leachates. The application of the byproducts reduced pollutant availability, the production of contaminated leachates, and pollutant accumulation in plants, thereby promoting plant development and survival. Conversely, the addition of the fertilizer alone led to an increase in As accumulation in plants and induced the production of antioxidant compounds such as carotenoids and free proline. Notably, all amendments led to increased thiolic compound production without affecting chlorophyll synthesis. While fertilizer application significantly decreased parameters associated with oxidative stress, such as hydrogen peroxide and malondialdehyde, no substantial reduction was observed after byproduct application. Thermal desorption analysis of the byproducts revealed Hg immobilization mechanisms, thereby indicating retention of this metalloid in the form of Hg chloride. In summary, the revalorization of industrial byproducts in the context of the circular economy holds promise for effectively immobilizing metal(loid)s in heavily polluted soils. Additionally, this approach can be enhanced through synergies with phytoremediation.

Crushing characteristics and particle size distribution of steelmaking slag according to repetitive compaction loads

Steelmaking slag, which is used as a construction material, can be crushed during compaction or repetitive loading in construction work. This crushing has a considerable influence on its physical and mechanical properties. Therefore, this study aims to evaluate/estimate the crushing properties and particle size distribution of steelmaking slag under various compaction loads. Accordingly, compaction tests were conducted by subjecting steelmaking slag with 10 different particle sizes to an increasing number of compaction cycles (1–15 times) to simulate repetitive compaction loading. The compaction test results were analyzed by considering the particle size distribution, particle size distribution curve, breakage factors, and fractal dimension. The results revealed that these factors could be influenced by changing the voids in steelmaking slag by altering the repetitive compaction load and particle size. An equation for predicting the particle size distribution from the compaction energy and particle size based on the sequence limit with the rational and the recurrence formulas was proposed. The proposed equation demonstrated excellent accuracy, and it can be utilized in efficiently predicting the particle size distribution curve.

Separation of Phosphorus from Phosphorus-concentrated Steelmaking Slag

Separation of Phosphorus from Phosphorus-concentrated Steelmaking Slag

Properties of Fluorine-Free Steelmaking Flux Prepared Using Red Mud

The basic oxygen steelmaking process is based on the CaO-FeO-SiO2 ternary slag system, characterized by a high melting point and low lime dissolution rate, often becoming one of the key factors limiting the efficiency of the converter. The bulk solid waste red mud, produced by the Bayer alumina process and rich in Fe2O3/Al2O3/Na2O, significantly reduces the melting point of the steelmaking slag system and enhances the efficiency of lime dissolution. This study utilized red mud as the main raw material to prepare a fluoride-free flux. An in situ online observation system was used to measure the melting point of the flux and the dissolution rate of lime in the flux. The results indicate that the melting point of the red mud-based flux is below 1200 °C, and under the same conditions, the lime dissolution rate is 10 to 15 times higher than when this flux is not used. Experiments in a 10 kg induction furnace show that using this flux, the dephosphorization rate under conditions without oxygen blowing is close to 40%, far higher than the rate achieved using CaF2. Under oxygen-blowing conditions, the dephosphorization rate using the red mud-based flux is comparable to that of CaF2, and significantly higher than without any flux, especially under high [C] content conditions. The data show that the red mud-based flux has the potential to be widely used as a fluoride-free flux in the steelmaking process.

Two-stage leaching of calcium and vanadium from high-calcium steelmaking slag

ABSTRACT Vanadium (V) is a critically important element in many industries. A widely used recovery process is a combination of roasting and leaching. However, roasting is an energy-intensive stage. Generally, basic oxygen furnace (BOF) slag is high in calcium (Ca) but low in V. Ca content and its chemical nature can prevent V leaching. This study presents a potential two-stage leaching process for Ca and V from BOF slag. The method is environmentally friendly using low temperatures and enabling leachate recycling. Furthermore, the utilisation rate of the slag can be higher due to Ca recovery. Ca is first leached using ammonium nitrate and nitric acid solution. The V-containing residue is directed to the second stage, where V is leached using ammonium carbonate ((NH4)2CO3). Ca leaching efficiency was 71% achieved with a low temperature (40°C) and in 20 min. > 99% of the dissolved element was Ca. Increasing the total nitrate concentration increased the leaching efficiency. Reducing the L/S ratio improved selectivity. The solid material was analysed after the leaching stages and a clear change was observed after the Ca-stage. The V leaching efficiency was 50%. > 88% of dissolved element was V (L/S 8, [(NH4)2CO3] 200 g/L, 60°C, and 60 min). Increasing [(NH4)2CO3] and L/S ratio slightly improved the leaching efficiency but decreased selectivity. The studied process implements circular economy principles and has been developed for side streams with low V concentrations. However, further optimisation and developments are required regarding the effectiveness of the process.

Integration of Modified Solvay Process for Sodium Bicarbonate Synthesis from Saline Brines with Steelmaking for Utilization of Electric Arc Furnace Slag in CO2 Sequestration and Reagent Regeneration

In the pursuit of sustainable solutions for carbon dioxide CO2 sequestration and emission reduction in the steel industry, this study presents an innovative integration of steelmaking slag with the modified Solvay process for sodium bicarbonate (NaHCO3) synthesis from saline brines. Utilizing diverse minerals, including electric arc furnace (EAF) slag, olivine, and kimberlite, the study explored their reactivity under varied pH conditions and examined their potential in ammonium regeneration. SEM and WDXRF analyses were utilized to acquire morphological and chemical compositions of the minerals. Advanced techniques such as XRD and ICP-OES were employed to meticulously analyze mineralogical transformations and elemental concentrations. The findings demonstrate that steelmaking slag, owing to its superior reactivity and pH buffering capabilities, outperforms natural minerals. The integration of finer slag particles significantly elevated pH levels, facilitating efficient ammonium regeneration. Geochemical modeling provided valuable insights into mineral stability and reactivity, which aligned with the ICP-OES results. This synergistic approach not only aids in CO2 capture through mineral carbonation but also minimizes waste, showcasing its potential as a sustainable and environmentally responsible solution for CO2 mitigation in the steel industry.

Elemental Concentrations of Natural Graphite and Steelmaking Slag: Development of Microwave-Assisted Acid Digestion

To develop more sustainable purification and recovery processes, it is critical to accurately determine inorganic impurities of natural graphite (NG) and valuable elements present in low concentrations in steelmaking slag. This study applied three microwave-assisted acid digestion methods for basic oxygen furnace (BOF) slag, NG, and NG ash. Nitric acid (HNO3), hydrochloric acid (HCl), and hydrogen fluoride (HF) were used in method 1. In method 2, method 1 was followed by microwave-assisted boric acid (H3BO3) digestion. In method 3, acids (HNO3, HCl, HF, and H3BO3) were added simultaneously. Concentrations were measured using inductively coupled plasma–optical emission spectrometry. Analytical performance was evaluated using spiking recovery tests (NG) and certified reference (slag) material (CRM). Spiking recoveries for Al, Ca, Fe, K, Mg, Na, and Si were between 5% and 116% (method 1) and 94%–116% (methods 2 and 3). CRM recoveries for Al, Ca, Fe, Mg, Mn, P, Si, Ti, and V were between 2% and 102% (method 1) and 92%–103% (methods 2 and 3). The unsuitability of method 1 was evident due to the low recoveries. Methods 2 and 3 digested Ca- and Si-containing BOF slag completely without visible residue. The sufficient recoveries verified the adequacy of the methods. The suitability of method 3 probably depended on the phases of samples, as quartz was not completely digested from the NG. Method 2 completely digested the inorganic material of NG, and the spiking test showed no loss of volatile silicon compounds. These methods have not been published for NG or NG ash and validated for slag before.

FePO4 preparation and residue recycling by co-processing of steelmaking slag and steel pickling waste liquor: Comprehensive utilization of metallurgical wastes

To prepare FePO4 and to achieve resource utilization of metallurgical wastes, a collaborative treatment of P-bearing steelmaking slag and steel pickling waste liquor (SPWL) was proposed. The utilization of SPWL as a leachant for P separation from steelmaking slag facilitates P-removal residue recycling within steel plants, while also serving as a Fe source for the FePO4 preparation. In this study, the effects of synthetic SPWL with various Fe2+ (or Fe3+) contents and leaching parameters on the dissolution behavior of steelmaking slag were investigated. Moreover, the impacts of H2O2 oxidation and pH on the precipitation behavior of FePO4 from leachate were studied. It was found that increasing Fe2+ concentration in SPWL resulted in a marginal reduction in the P dissolution ratio; however, it was significantly influenced by the pH and solid/liquid ratio. Furthermore, the change in Fe3+ concentration within SPWL exhibited a conspicuous impact on the P dissolution ratio. After leaching, the residue containing massive Fe2O3, MgO, and MnO could be reused as a flux within the steelmaking process. The FePO4 precipitated predominantly at pH 2.0 ∼ 3.0, and the crude FePO4 product containing 42.6 % Fe2O3 and 35.8 % P2O5 was obtained, providing a new solution for the utilization of metallurgical wastes.

Metallurgical Waste as a Raw Material Reserve for Achieving Carbon Neutrality of the Construction Industry. Part 1. Ability of Metallurgical Waste to Bind CO2

The solution to global environmental problems is to reduce the anthropogenic impact on the environment through the utilization of carbon dioxide emissions and the use of industrial waste to produce new materials and products. Technogenic wastes of the metallurgical industry are considered as raw materials for the production of building materials and products with the ability to bind gaseous CO2. The analysis and selection of waste from metallurgical enterprises located in the Central and North-Western Federal Districts of the Russian Federation is carried out. The results of studies of environmental friendliness, chemical, material and phase-mineralogical compositions of technogenic metallurgy waste, their hydration activity and ability to bind carbon dioxide are presented. It is shown that the most promising raw materials for the production of building materials and products are steelmaking slags and nepheline sludge from the processing of alumina raw materials. The greatest ability to absorb and bind CO2 is distinguished by nepheline sludge (up to 12% CO2 by weight of sludge), steelmaking (converter and electric steelmaking) slags (up to 8.8 and 9.2% CO2 by weight of slag, respectively). The compressive strength of the prototypes on these types of slags depends on the degree of their carbonation and reaches values of 100 MPa or more after 6 hours of forced carbonation. It is concluded that the material obtained from man-made metallurgical waste by carbonation hardening technology can be used as a matrix substance for various building materials and products.