Aluminate Slag Research Articles

Use of Secondary Aluminum Slag Powder on the Strength of Non-Load-Bearing Lightweight Concrete Blocks

Use of Secondary Aluminum Slag Powder on the Strength of Non-Load-Bearing Lightweight Concrete Blocks

Study on the wetting characteristics of liquid-Al/ SiO2 interface with Si content in liquid-Al

Aiming to address the issue of aluminum slag adhering to the interior walls of vacuum lifting ladles in the aluminum electrolysis industry, Molecular dynamics simulations are employed to investigate the wetting behavior and adhesion characteristics of aluminum droplets on silica surfaces. Our findings indicate that with an increase in silicon content within the droplets, wetting diminishes and complete wetting of the silica substrate by aluminum droplets is not achieved. The presence of silicon reduces both the melting point temperature and surface tension of aluminum droplets, leading to a significant increase in contact angle and a corresponding decrease in wettability. Moreover, an elevated silicon content within molten aluminum droplets substantially decreases their interaction energy with the substrate surface. The virtual wall method is applied to examine average separation force and work of separation for detaching aluminum droplets from the substrate, revealing that adhesion characteristics are predominantly governed by mutual adhesive forces. This paper presents an atomic-level analysis elucidating how silicon as an alloying element influences adhesion between liquid aluminum and solid surfaces.

Preparation of polymeric aluminum chloride from secondary aluminum dross and its water purification effect

ABSTRACT Aluminum dross is solid waste generated by the aluminum industry. Currently, a large amount of aluminum dross is produced annually year. Aluminum dross, a hazardous waste, contains harmful substances such as aluminum metal, aluminum nitride, fluoride and chlorine salts, which pose a serious threat to human health and also cause damage to the ecological environment. Thus, it is important to recycle secondary aluminum dross and realise its high-value utilisation. Polymeric aluminum chloride (PAC) is a polymer flocculant, at present, China's annual use of PAC in the field of water treatment is about 5 × 105 t, and with the continuous improvement of water purification requirements, the annual use of PAC increased year by year. Here secondary aluminum dross was used as a raw material to prepare PAC by hydrochloric acid (HCl) leaching, followed by the addition of sodium carbonate. The optimal conditions for the acid leaching of secondary aluminum dross for the preparation of PAC were as follows: HCl concentration, 18%; liquid-to-solid ratio, 4.5:1; stirring rate, 200 r/min; reaction temperature, 90 °C; and 60 min. An aluminum leaching rate of 85.5% was obtained under these conditions. The results showed that the acid leachate after adding sodium carbonate, under the conditions of polymerisation temperature of 70 °C, polymerisation time of 6 h, and polymerisation pH value of 3.0, the PAC prepared had an alumina content of 10.19%, salinity of 32.37%, density of 1.32 g/cm3, 1% aqueous solution pH 4.3. The water purification effect of the prepared PAC surpassed that of the commercially available PAC. The utilisation of secondary aluminum dross can reduce the environmental pollution caused by aluminum slag.

Preparation of lightweight foam glass-ceramics from copper slag tailings: Secondary aluminum slag as pore-forming agent

To address metallurgical waste residue pollution, this study utilized copper slag tailings (CST) and waste glass (WG) as primary raw materials, with secondary aluminum dross (SAD) as a pore-forming agent, to produce lightweight spontaneous foam glass-ceramics. The effects of raw material ratios, sintering temperature (1120–1160 °C), and sintering time (0–40 min) on foam glass-ceramics properties were investigated, elucidating the correlations between various properties. Under optimal preparation conditions (CST: WG: SAD = 7:11:2, sintered at 1150 °C for 20 min), the foam glass-ceramics exhibited a bulk density of 0.41 g/m³, compressive strength of 2.32 MPa, open porosity of 61.02 %, 2-h water absorption of 83.76 %, and mean pore size of 3.12 mm. The sintering process transformed raw materials into substances like diopside subsilic ferrian, which enhanced the strength of lightweight foam glass-ceramics. Harmful substances in the raw materials can be immobilized within the internal structure of foam glass-ceramics, ensuring excellent environmental safety. Additionally, comprehensive characterization was conducted on the foam glass-ceramics, elucidating their composition, structure, and pore-forming mechanisms.

Effect of B2O3 on the viscosity, structure and crystalline phase of CaO–MgO–Al2O3–SiO2–MnO-based high alumina slags

The effects of B2O3 on viscosities, structures and phase transitions of CaO–MgO–Al2O3–SiO2–MnO-(0-8.0 wt%)B2O3 slags were investigated in this work. From the viscosity experimental results, the slag viscosities declined and the Eη decreased from 205.19 to 175.95 kJ/mol with the addition of B2O3 in slags from 0 to 8.0 wt%. From the structure analysis by using FTIR and XPS, B2O3 entered into the silicate network to increase the slag polymerization degree, while the formation of simple two-dimensional BO3 trihedral units could significantly decline the symmetry and stability of the structure. The effects of decreasing the network stability and forming low-melting eutectics were more dominated than the effects of increasing the structure polymerization degree, which could reduce the slag viscosity. Furthermore, adding B2O3 could decrease the slag initial precipitation temperature and change the primary crystal phase of the slag from melilite to spinel. The comprehensive effects of reducing the slag structure stability and decreasing the influence of solid phase on viscosity eventually resulted in the improvement of the slag fluidity.

STUDY OF THE EFFECT OF FLUXING MATERIALS ON THE DEPOSITION OF METAL BEADS FROM HIGH CARBON FERROCHROME SLAG

The study of the effect of the properties of high-carbon ferrochrome slags on the creation of favorable conditions for the deposition of metal beads with the introduction of the following fluxing additives in an amount of 3-10%: slag produced by refined ferrochrome (stale and stabilized), cryolite, fluorite, feldspar, colemanite, fused borate ore, aluminum slag of aluminum production. The influence of the type and quantity of fluxing materials on the viscosity and crystallization temperature of high-carbon ferrochrome slags has been studied. It is noted that the use of all types of fluxing materials under study leads to a decrease in the crystallization temperatures of the processed slag. It can be seen from the results of metallographic and phase analyses that the best values for the degree of coagulation and deposition of metal crowns were achieved with the introduction of aluminum slag, colemanite and borate ore.

Inter-property Correlation of Al2O3-CaO-MgO-SiO2 Quaternary Slag System in Blast Furnace Ironmaking

Exploring the correlation between the density and the thermo-physical properties of the Al2O3-CaO-MgO-SiO2 quaternary slag system is a subject of great interest in the domain of high alumina slag systems. This work attempts to establish correlations between (a) molar volume/density with enthalpy of mixing and (b) molar volume/density with slag viscosity, for the quaternary slag systems. The former is targeted based on existing models to determine the slag density and enthalpy of mixing first and then to develop machine-learning models which can suitably extrapolate the enthalpy of mixing as a function of slag composition, temperature and density. The volume shrinkage and the exothermic enthalpy of mixing between the slag constituent components are correlated in the current work. The later part would involve the conjunction of two hybrid machine-learning models, one for predicting slag viscosity as a function of slag compositions and temperature, and the other which predicts slag viscosity with the incorporation of slag density. The work will facilitate the establishment of two novel quantitative relationships that could provide better insights into the blast furnace quaternary slag systems.

GGBFS and Red-Mud based Alkali-Activated Concrete Beams: Flexural, Shear and Pull-Out Test Behavior

Geopolymers and antacid-enacted fasteners have accumulated critical interest as promising development and fixing materials because of their exceptional properties. Also, they bring about less contamination contrasted with regular concrete cements. Geopolymers address a clever class of suggested restricting materials blended through the basic enactment of bountiful aluminosilicate materials. The usage of geopolymer materials from side effects offers a critical decrease in carbon impression and yields positive natural effects. Geopolymer is progressively recognized as a plausible substitute for OPC concrete. In this review, sodium-based antacid activators, especially sodium metasilicate (Na2SiO3), were used for different blend extents. The boundaries researched included NaOH arrangements with a grouping of 8 M, alongside a Na2SiO3/NaOH proportion of 1. This paper evaluates the fundamental characteristics of geopolymer cement beams, employing red mud and GGBFS in powdered form as complete replacements for traditional concrete. Six bar specimens are tested under a two-point static loading condition, all cured at room temperature under ambient conditions. Of the six beams, three were exposed to flexural conduct testing with a molarity of 8 M, while the excess three beams were tried for shear conduct. The outcomes of testing geopolymer beams subjected to shear and bending loads indicated that the beams incorporating aluminum slag performed better than those incorporating blast furnace slag. Both types also demonstrated promising results compared to beams incorporating OPC, highlighting their potential environmental benefits compared to cement use. Doi: 10.28991/CEJ-2024-010-05-09 Full Text: PDF

Clean and sustainable elimination of arsenic–aluminum slag from smelted crude tin via vacuum volatilization – Fractional condensation

In high–tech industries, Sn is an indispensable strategic metal. However, the pyrometallurgical refining process of crude Sn is marred by the production of a substantial amount of hazardous solid waste, primarily As–Al slag, which poses a direct threat to the ecological safety of production areas. To address this problem, this study developed a novel process for that eliminates As–Al slag from a source of crude Sn by employing a vacuum volatilization – fractional condensation process, which was validated by theoretical calculations and laboratory experiments. Theoretically, at system pressures in the 1–10 Pa, the initial volatilization temperatures of Sn, Sb, and As vary significantly. However, the formation of intermetallic compounds can induce the volatilization of Sn. Experimentally, the condensation temperature for Sb was predominantly between 603 K and 810 K, and that for As was between 331.7 K and 484.7 K, which are significantly different ranges. Under optimal experimental conditions, the separation rate of Sb in the Sn–Sb alloy was 93.92%, and the resultant Sn product contained 0.0143% Sb. During the volatilization of the Sn–As alloy, the presence of Sn4As3 compounds impeded the volatilization of As; hoewver, the As content in the Sn product was 0.0053%. In the directional condensation of the As–Sb alloy, the condensation temperatures for As and Sb were similar to those of the pure metals, yielding As and Sb products with purities of 99.99% and 99.95%, respectively. Industrial production trials treating HACT via a continuous vacuum separation – intermittent vacuum separation process achieved direct recovery rates of 72.99% for Sn and 71.15% for Sb, with a total energy consumption as low as 1086 kWh/t. Similarly, the treatment of LACT via a multi–stage continuous vacuum separation process yielded residues that satisfied production standards at a treatment cost of 1187 RMB/t. This entire process requiresno additives, and substantially mitigates the generation of As–Al slag at the source.

Surface ionic coordination of Al2O3–CaO–based molten slag induced by structural relaxation

AbstractThe surface tensions of molten oxides depend strongly on the structural relaxation of the surface region. The mechanism of surface structural relaxation for molten oxide slags is complex. The surface tension of calcium aluminate slag is minimal at an intermediate composition, although the critical reason has not been identified. Here, two novel approaches were used to evaluate the features of surface ionic structures in the molten state for the range of 25–50 mol% Al2O3: (1) X‐ray absorption analysis of oxygen and cationic elements in glass samples after surface relaxation treatment, and (2) molecular dynamics simulations, based on a polarizable‐ion model, of the ionic distribution in a molten slag with vacuum/melt interfaces. The results indicate that bridging oxygen (BO) ions are preferred to non‐BOs in the surface region. In calcium aluminate slag, BOs are formed by connecting two AlO4 tetrahedrons with charge compensation of two Al3+ ions with one Ca2+ ion. Additionally, the above approaches were used to qualify the effect on the surface ionic structure of adding 1–20 mol% SiO2 to the calcium aluminate slag. The results indicated that the SiO4 tetrahedrons incorporate the vertex connection with AlO4 tetrahedrons to form BOs in the surface region.

Wetting Behavior of High Alumina Slags on the Fused Magnesia under Different Atmospheres and Low Static Magnetic Field

With the growing demand for high‐aluminum steel, there is an urgent need to enhance the slag resistance of magnesia‐based refractories. The wettability of high‐alumina slag on magnesia‐based refractories serves as a crucial indicator of the refractory's slag resistance. In this study, the influence of atmosphere and magnetic flux density on the wetting behavior between the slags with different basicity (CaO wt%/SiO2 wt%) and fused magnesia is explored using a high‐temperature visualization device with a controllable static magnetic field. Compared to air and argon atmospheres, the apparent contact angle of the slag on the fused magnesia decreases significantly in a vacuum environment as the violent interfacial radical reaction. The static magnetic field of 0.5 mT can regulate the spin state of a single electron in the free radical pair, resulting in an increase of the apparent contact angle by 21.1% in a vacuum atmosphere. It provides new thoughts on the development of external field protection technology for the corrosion resistance of magnesia‐based refractories.

Efficient lithium recovery from electrolytic aluminum slag via an environmentally friendly process: Leaching behavior and mechanism

The electrolytic aluminum industry generates a large amount lithium (Li)-containing electrolytic aluminum slag (EAS) annually, and this can result in severe environmental pollution and wasting of Li resources. This paper proposes a method for recovering Li from the slag using AlCl3 as the leaching agent. The effects of the leaching temperature, AlCl3 concentration, pH, and solid-to-liquid ratio (S/L) on the leaching efficiency of Li+ were systematically examined. The structural transformation during the Li leaching process was revealed by SEM, XRD, 27Al NMR, and XPS analyses. The results indicate that up to 88.3% of Li + can be leached out using 0.85 M of AlCl3 with an S/L of 1:3 at a leaching temperature of 95 °C and pH of 0.5. The addition of AlCl3 played an essential role in the decomposition of cryolite/cryolithionite, ultimately resulting in Al–F fracture and Li+ release in the leaching solution. Moreover, Al3+ enters the interior of the slag to participate in the reconstruction of the chiolite with a low NaF/AlF3 ratio, and reacts with OH− ionized from H2O to form hydroxyl aluminum fluoride species. Fluorine ions were solidified in the leaching residues for subsequent cryolite regeneration. This study not only provides an environmentally friendly process for resource utilization from EAS but also reduces the environmental threat caused by the storage of the hazardous waste.

Composites derived from co-pyrolysis of residual biomass with aluminium slag as effective materials for volatile organic compounds removal

Co-pyrolysis is an important method to transform hazardous waste into new materials, and composites based on biochar and metal oxides could constitute new types of adsorbents for volatile organic compounds (VOCs). In this study, residual biomass (corn cob, rapeseed and walnut shell) was co-pyrolyzed at 650OC with aluminum slag (AlS), and different composites were synthesized. Biocomposites have been used as adsorbents for the removal of VOCs (such as acetone and toluene). The results showed that the biocomposite obtained from corn cob and AlS has a higher adsorption capacity for acetone, while the composite obtained from walnut shell and AlS showed a higher adsorption capacity for toluene. All prepared composites showed a higher adsorption rate than the corresponding pure biochars. After eighth cycles of adsorption/desorption, the results obtained showed the sample AlS650-Na/BCCC presented a good adsorption performance for acetone ( 318 mg/ g) in the first three cycles, and then the adsorption capacity decreased slowly, with the increase in the number of adsorption cycles. However,the adsorption capacity of 254.41 mg/g was still high after the eighth cycles.A similar behavior was presented by the AlS325-Na/BCWS composite for toluene adsorption.Therefore,AlS/BC composites could be used as a potential adsorbents in VOCs removal.

Synthesis and characterisation of mesoporous MgAl2O4 hollow spheres as a high-value product in a waste recovery strategy

Micrometre-scale hollow sphere-shaped MgAl2O4 powders were synthesised using a spray-drying method, followed by calcination. An aqueous solution of mixed Mg2+ and Al3+ salts, derived from aluminium slag and serpentine tailings, served as a source of magnesium and aluminium. The secondary raw materials were subjected to acid leaching, and the refined leachates were used to prepare a spray-dried MgAl2O4 precursor, which was heat-treated at temperatures ranging from 550 °C to 1100 °C for 1 h. Characterisation of the resulting MgAl2O4 spinel powders was performed using various physicochemical techniques, including thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and physical adsorption using N2 (BET). The prepared MgAl2O4 spinel demonstrated several unique properties, including ultrafine particles with a uniform distribution (1–5 μm) and minimal particle agglomeration, high sintering activity (beginning at 550 °C), high purity, high specific surface area (110 m2 g-1/750 °C), and open porosity with a narrow pore size distribution (3–7 nm). These properties make the prepared MgAl2O4 spinel a highly valuable product for waste recovery strategies. The simplicity, efficiency, and cost-effectiveness of this process also predispose it to large-scale production of functional mixed metal oxides of various compositions for use in industries such as energy storage, sensing, and 3D printing fillers.

Екологічні аспекти переробки ливарного алюмінієвого шлаку

Data on the influence of the aluminum slag processing process on the state of the atmospheric environment are presented. Calculations of the dispersion of pollutants (PO) in the surface layer of atmospheric air were carried out, which showed the absence of exceeding the maximum permissible concentrations (MPC) for carbon monoxide, nitrogen dioxin, sulfur dioxide, hydrogen chloride and dust. Analysis of emissions was carried out for extreme conditions of equipment operation. It was established that under such technological conditions, the maximum concentration of pollutants is: NO2 ≤ values of 0.2 MPC, and the rest of the pollutants do not exceed - 0.05 MPC. To identify the actual concentrations of hazardous substances at the border of the sanitary protection zone (SZZ), laboratory tests were performed at a distance of 300 m from the emission source. It was established that emissions of pollutants into the atmosphere from the industrial site on the territory of the enterprise and on the border of the calculated sanitary protection zone are less than the MPC of the atmospheric air of populated areas and will not have a significant harmful effect on the environment, provided that the sanitary and technological requirements for operation are met. The level of the content of harmful impurities in the air does not exceed the hygienic standards outside the sanitary protection zone, which are established for the atmospheric air of populated areas. Keywords: ecology, pollutants, maximum permissible concentration, aluminum slag.

Upgrading the corn cob pyrolysis vapors by processing over catalysts based on aluminium slag and the assessment of the produced bio-oil

In this paper the processing of corn cob pyrolysis vapors (CCPV) over catalysts based on aluminium slag (AS) was studied as a new route to produce bio-oil with improved quality. The processing of the CCPV was performed in a lab-scale fixed bed reactor applying raw and modified aluminium slag as catalysts and also without catalyst and the resulted bio-oils were compared.The proportion of the oxygenated compounds in bio-oil phase obtained without catalyst was increased compared with bio-oil phase obtained with catalysts, in which the concentrations of the compounds free of oxygen or with low oxygen content was predominant.The degree of deoxygenation (DOD) for bio-oils produced catalytically after five consecutive processing/regeneration cycles was in the range of 59.38–64.02 %,depending on the catalyst used, the highest DOD of 64.02 % was obtained for the bio-oil produced with NaAS as catalyst. During the CCPV processing on the catalyst was deposited coke leading to a possible its deactivation.The deposited coke amount was determined, the catalyst was regenerated by coke combustion and then reused in the five cycles. It could be observed that after five cycles of processing the amount of deposited coke remained almost the same(in the range 0.051–0.085 g) which indicated a good regeneration and a stable behavior of the catalyst. As such, the CCPV processing with catalysts based on AS represents an economically attractive alternative to more expensive catalysts such as zeolites for production of bio-oil with good quality, which may be further processed in conventional refineries or directly applied as a renewable fuel.

Effect of alkaline oxides on aluminate slag structure by first principles calculation

To guide the research and development of CaO-Al2O3-based mold fluxes, the influence mechanism of 8 mol% alkaline oxides (Na2O, Li2O, BaO, MgO) on the multi-scale structure characteristics of aluminate slag (CaO/Al2O3 = 1.3) at 1873 K was analyzed by first-principles calculation. With the addition of alkaline oxides, the stability of Al-O and Ca-O bonds in slag system was Na2O-Al2O3-CaO (NAC) ≈ BaO-Al2O3-CaO (BAC) > Li2O-Al2O3-CaO (LAC) ≈ Al2O3-CaO (AC) > MgO-Al2O3-CaO (MAC), and the proportion of average coordination number for Al were AC > MAC > LAC > BAC > NAC. The alkaline cations played two roles of structure depolymerization and charge compensation, as the ability was ranked as NAC > BAC > MAC > LAC, and Na+ > Li+ > Ba2+ > Mg2+, respectively. At the electronic level, a small number of electrons were localized between O atoms, which surrounded Al to form a closed structure. Adding appropriate amount of Na2O/BaO was necessary to effectively regulate the low/non-reactive mold flux.

Aluminium extraction from a calcium aluminate slag using sodium carbonate based on the critical examination of the patented industrial Pedersen process

The extraction of aluminium from calcium aluminate phases by leaching with Na2CO3 solutions has been researched intermittently for more than a hundred years. In the 21st century, this process has gained a renewed interest for the design of novel metallurgical methods. The Pedersen Process has been the only known successful industrial scale application of calcium aluminate leaching to date. The engineering principles that ensured plant operations remained, until recently, unknown. These principles are critically assessed for the first time, based on recently retrieved patents submitted at the time the Pedersen process was in operation. The findings of the previous analysis were used for an experimental study with the two goals: (i) to validate the principles applied in the industrial Pedersen process and (ii) to apply these principles in designing an optimized leaching process for calcium aluminate slags originating from alternative Al sources. The calcium aluminate slag used in this study is the by-product of an aluminothermic reduction process for Si production along with an 8% (w/w) Na2CO3 aqueous solution. Results confirmed the majority of the assumed principles. All the tested leaching conditions produced Al extraction in the range of 75% - 95% (w/w).

Effect of BaO and MgO on structure and properties of aluminate slag with various CaO/Al2O3 ratios

Effect of BaO and MgO on structure and properties of aluminate slag with various CaO/Al2O3 ratios

Thermal and Energy Efficiency of Roof Tiles Fabricated from Crushed Aluminum Slag and Kaolin Clay for Social Residential Buildings in Egypt

Thermal and Energy Efficiency of Roof Tiles Fabricated from Crushed Aluminum Slag and Kaolin Clay for Social Residential Buildings in Egypt