Aluminate Slag Research Articles

Effect of Synthesis Conditions on Mechanical Strength of Aluminium Slag Modified Waste Foundry Sand Geopolymers

The waste foundry sand was alkaline activated into geopolymers to reduce their environmental pollution. The waste foundry sand was blended with aluminium slag and alkali activated to produce geopolymers. Aluminium slag was used to supplement WFS with alumina because as it has low content of alumina. The main parameters tested were the effect alumina content, concentration of alkali, liquid to solid ratio, and temperature. The optimum synthesis parameters were a geopolymer prepared with 2% aluminium, 3 M NaOH solution, liquid solid ratio of 0.15 and curing temperature and time of 80°C and 5 days respectively. The optimum parameters yielded the highest UCS of 4.7 MPa. The developed aluminium slag modified waste foundry sand geopolymers met the minimum requirements for ASTM C126-99 and ASTM C216-07a.

Effect of B2O3 on the structure and properties of aluminate slag

The spectral experiment, hemispherical melting point apparatus, rotating cylinder method, and four-probe method are conducted to measure the structure, melting temperature, apparent viscosity and electrical conductivity of aluminate slag. The results show that in order to reduce the comprehensive effect of capacitance and inductance, the frequency of value 6000 Hz corresponding to the minimum impedance is most suitable for the electrical conductivity measurement. Higher B2O3 content leads to a lower degree of polymerization, symmetry, and uniformity in the complex three-dimensional structure of the slag, meanwhile the slag hemispheric temperature declines gradually, which enhances the slag superheat, hence decreases the apparent viscosity and increases the electrical conductivity comprehensively, as well as the relation between viscosity logarithm and the conductivity logarithm at 1300 °C was linear. The breaking temperature of apparent viscosity-temperature curve reduces gradually with B2O3 addition, while the conductivity-temperature curve indicate that the slag crystallized at about 1210 to 1224 °C, and with the lower B2O3 content, the crystallization trend is more obvious.

Proposing a suitable slag composition by estimating the fusion behavior, viscosity and desulphurization ability for blast furnaces running with high alumina

The present work was focused on identifying a suitable quaternary CaO-MgO-SiO2-Al2O3 high alumina slag for blast furnaces running with high alumina ores as an input raw material. These high alumina slags have inferior properties like high liquidus temperature, high viscosity and poor sulphur absorption capacity. These properties will hamper the working condition of the blast furnace as well as quality of hot metal produced. To overcome these issues, it is necessary to focus on selecting an appropriate slag composition having superior properties like, minimum difference between softening and flow temperature (ST & FT) (<100 °C), low liquidus temperature, good fluidity (i.e. viscosity <0.6 pas. at 1773 K) & high sulphur absorption capacity at 1773 K. In the current work various slag compositions having Al2O3 25–30 %, CaO/SiO2 ratio (0.8–1.6), and MgO (8–16 %) has considered for determining fusion temperature, viscosity and desulphurization ability of slag using high temperature microscope, viscometer and slag-metal Desulphurization experiments. It was found that slag with Al2O3 (30 %) and C/S ratio (1.2) coupled with MgO (12 %) is showing superior properties like low FT-ST (i.e. short slag) having viscosity 0.35 pas and Desulphurization ability of approx. 80 % at 1773 K which fulfills the necessary conditions for better working condition of the blast furnace.

Evaluation of Calcium Aluminate Slags and Pig Irons Produced from the Smelting-Reduction of Diasporic Bauxite.

This work evaluates the characteristics of calcium aluminate slag and pig iron samples obtained from the smelting of calcined and reduced diasporic bauxite ore. The study is conducted in the Pedersen process framework, which is a method to produce alumina from low-grade resources. Parameters such as the effect of crucible type, lime addition, and atmospheric conditions are studied considering the characteristics of the product pig irons and calcium aluminate slags for further uses. The behavior of the bauxite and distribution of the species between slag and metal was assessed based on the applied analytical techniques and thermodynamic calculations. Iron was reduced and separated from the slags in the presence of carbon (graphite crucible) for both the reduced and calcined bauxite. Si and Ti were mainly concentrated in the slags. Iron was separated from the slag in the absence of carbon (alumina crucible) for the H2-reduced bauxite. The results show that slags with increased lime additions are composed mainly of 5CaO.Al2O3 and CaO.Al2O3, that are considered highly leachable compounds. An optimum CaO/Al2O3 mass ratio of 1.12 was suggested. The presence of O2 and/or OH- in the furnace atmosphere will result in the formation of 12CaO.7Al2O3.

The use of aluminum slag waste in the preparation of roof tiles

AbtractAluminum slag waste generated from the smelting process of bauxite was used to prepare roof tiles samples. Clay was substituted by slag waste in percentages reaching 40% in the basic mix and the plasticity of the obtained mud was determined. This was followed by pressing the mud in steel molds and drying. The effect of waste addition on drying shrinkage was subsequently assessed. Firing of the green bodies was carried out at three temperatures (900, 1000 and 1100 °C) and hour soaking at each temperature. Fired roof tile properties improved on increasing the percentage of alumina sludge and firing temperature possibly because of the presence of high amounts of fluxing oxides in aluminum slag. This caused a drop in porosity that increased the mechanical strength of tiles. The results showed that the substitution of clay by 40% waste and firing at 1100 °C resulted in products conforming to ASTM C-1167 for clay type roof tiles. Cold water absorption dropped to 12%, below the maximum permissible limit of 15%, the value of Saturation Coefficient was 0.83, below the 0.86 limit and the obtained breaking strength of 3370N significantly exceeded the minimum requirement of 890N.

Monitoring the oxygen removal process at the final stage of melting steel

This article deals with removing oxygen at the final stage of steel smelting in arc steel-making furnaces. It is shown that the remaining oxygen during crystallization forms floccules and significantly reduces the quality of the finished metal. During the subsequent metal processing by pressure on these floccules, the metal is torn apart and makes it impossible to obtain a steel sheet. Deoxidation is performed with expensive ferroalloys, and their consumption must be minimized. To achieve economic efficiency, it has been proposed to use recycled aluminum slag as a relatively inexpensive local deoxidizer. To optimize the deoxidizer consumption, a rapid analysis method was developed using the electromotive force (EMF) determination to determine the oxygen activity in liquid steel. As a result of the study, the composition, structure, and technological parameters of deoxidized steel were determined. The use of this technology in production will make it possible to obtain high-quality steel and improve environmental protection through secondary aluminum waste.

Preparation and Properties of a Sulphoaluminate Magnesium-Potassium Phosphate Green Cementitious Composite Material from Industrial Solid Wastes.

The preparation of high-performance green cementitious material from industrial solid waste is a feasible large-scale utilization approach for industrial solid waste. This work investigates the feasibility of using industrial solid wastes in a sulphoaluminate–magnesium–potassium–phosphate cementitious composite material (SAC-MKPC) clinker preparation and the influence of the calcination temperature and clinker ingredients on the hydration behavior and mechanisms of the SAC-MKPC with a Mg/P ratio of 5. The results show that the novel SAC-MKPC that was prepared from aluminum slag, carbide slag, coal gangue, and magnesium desulfurization slag was composed mainly of mineral MgO, , and C2S and the calcination temperature of the main mineral phases was 1250–1350 °C. The solid-waste-based SAC-MKPC had better mechanical properties and excellent water resistance compared with the MKPC. The optimal compressive strength reached 35.2, 70.9, 84.1, 87.7, and 101.6 MPa at 2 h, 1 d, 3 d, 7 d, and 28 d of hydration, respectively. The X-ray diffraction spectra and scanning electron micrographs of the hydration products of the SAC-MKPC clinker showed that AFt and K-struvite crystals coexisted and adhered to form a dense structure. This work provides an innovative idea to produce green cementitious material using industrial solid wastes and may promote the sustainable development of the power and mining industries.

Recycling waste material for backfill coupled heat exchanger systems in underground stopes of mines

The continuous exploitation of mineral resources into the deep strata provides suitable conditions for the development of geothermal energy. Backfill technology can not only ensure the safety of mining operation and realize the recovery and utilization of solid waste, but also serve asartificial thermal reservoir. However, ordinary backfill materials have poor thermal properties and limit the geothermal energy extraction. In this paper, a novel backfill materialwith good thermal performance was proposed and tested to replace the traditional materials. The feasibility ofhorizontal backfill coupled heat exchanger system was evaluated by experimental method for the purpose of efficientcooperative development of mineral resources and geothermal resources. Natural flake graphite and other solid waste materials, such as copper slag, steel slag, aluminum slag and coal gasification slagwere used to replace tailings of 2.5%, 5%, 7.5% and 10% by mass fractionto make the composite backfill material. The uniaxial compressive strength, mini-slump, thermal conductivity, specific heat capacity and density of the composite backfill material were tested to explore the best proportion. An experimental set-up of a backfill-coupled heat exchanger system was then constructed and filled with the backfill material to determine the heat storage and release processes on the thermal performance of the system. The influence of the composite backfill material and surrounding rock temperatures on the energy efficiency of the backfill coupled heat exchanger system was evaluated. The results showed that, with the increase of the tailings substitution rate, the uniaxial compressive strength, specific heat capacity and density of the composite backfill material were reduced compared with the traditional backfill material, while the thermal conductivity and thermal diffusion coefficient were increased. Finally,10% natural flake graphite instead of tailings was used to make the backfill body for testing. Compared with traditional backfill coupled heat exchanger system, when the surrounding rock temperature was 55 °C, the heat discharging and the total efficiency of natural flake graphite - backfill coupled heat exchanger system increased by 579.1 kJ and 31.6 %, respectively. The research results provide a reference for the application of backfill coupled heat exchangers in engineering practice.

Evaluating the Effect of MgO/Al2O3 Ratio on Thermal Behaviors and Structures of Blast Furnace Slag with Low Carbon Consumption

In order to clarify the effect of the MgO/Al2O3 ratio on the fluidity of a low-alumina blast furnace slag system, the influence law of slag fluidity with different MgO/Al2O3 ratios was studied based on the composition of blast furnace slag through a viscosity experiment and themodynamic software. By studying the effect of the MgO/Al2O3 ratio on the activation energy of viscous flow of slag combined with FT-IR, the effect of the MgO/Al2O3 ratio on the thermal-stability of low-aluminum slag was interpreted from the microstructure level. Results indicated that the viscosity and the melting temperature of slag both showed a gradual downward trend due to the increase of the MgO/Al2O3 ratio. Besides, the temperature stability of the low aluminum slag became more stable due to the depolymerization of the complex structure of slag. Considering the actual operating conditions of blast furnace, the MgO/Al2O3 ratio of slag was suggested to be controlled to 0.60 and the basicity to be no higher than 1.20 under the conditions of this investigation. Industrial test results showed that the coke rate could be saved as 3.49 kg/t when the MgO/Al2O3 ratio decreased from 0.70 to 0.58.

The application of MFA for rural industrial symbiosis assessment

One of proposed strategies to solve current environmental challenges includes the industrial symbiosis. However, proper evaluation methods are required to measure the potential benefits of industrial symbiosis, one of those includes the material flow analysis (MFA). MFA develops a unified database and a Step-by-Step process starting from the input, process, and output process to clarify the distribution of waste and the recycling process in the aluminum industry. The aluminum industry is regarded as an energy-intensive and high-pollution industry. The development of industrial symbiosis in the aluminum industry has significantly reduced environmental pressures and facilitated green development and green industry. Home industries that process aluminum slag raw materials require high energy thereby generating high waste during the production process. The applied method includes material flow analysis (MFA). The MFA results indicated that the production elements of the aluminum slag industry consist of 11 elements ranging from raw materials, fuel, clean water, human resources, capital, production processes, production equipment, housekeeping, products produced, waste to waste utilization. Approximately 44% of the industry sold waste to other industries, 42% of the waste was reprocessed, and 14% of the aluminum industry stockpiles production was in the form of waste in open spaces. The industrial symbiosis in the aluminum industry was an open cycle, indicating that the symbiosis produces waste, which had not been fully utilized; but in fact, the waste had potential as a source of raw materials, energy, and materials in other industrial processes.

The Influence of Aluminum Slag Ash for Paving Block Production

Aluminum slag ash commonly used as road and river embankments. It had disposed in an open site and potentially increase ammonia, sodium, potassium, chloride and total dissolved solids levels in the surrounding environment. As much as 90% of Portland cement is composed of a mixture of elements of Ca, Si, Al, and Fe which are bonded into certain complex compounds. This study aims to analyze the influence of cement substitution with aluminum slag ash on the compressive strength and water absorption capacity of the paving block, and the appropriate type of paving block quality which is following SNI 03-0691-1996. The test objects used were paving blocks with a ratio of cement and sand of 1:3, where the composition of the addition of aluminum slag ash used was 5%; 10%; 15%; and 20%. The tests in this study were on compressive strength, water absorption capacity, and Toxicity Characteristic Leaching Procedure (TCLP) tests. The optimum composition is 10% aluminum slag ash in cement substitution. The type of quality is category B paving for parking equipment. The results of the TCLP on a 10% composition paving obtained that the parameter concentration is below the TCLP quality standard.

Research on the Preparation Parameters and Basic Properties of Premelted Calcium Aluminate Slag Prepared from Secondary Aluminum Dross.

Secondary aluminum dross is a byproduct of the electrolytic aluminum industry, whose main components are Al2O3, AlN and Na3AlF6. Secondary aluminum dross is a type of hazardous waste, with a tremendous yield every year. Realizing the harmless treatment or resource utilization of secondary aluminum dross has important economic and social benefits. In the present research, the process of preparing premelted calcium aluminate slag used for molten steel refining from secondary aluminum dross was studied in detail. Firstly, the chemical composition and phase component of secondary aluminum dross were analyzed systematically. Then, according to phase diagram analysis and melting point measurement, the appropriate mixing ratio of CaO and secondary aluminum dross and the appropriate calcination temperature were determined. On this basis, an experiment of premelted calcium aluminate slag preparation was carried out in a tubular resistance furnace. The phase component and micromorphology of the premelted slag were analyzed by XRD and SEM. The results show that the main component of the premelted calcium aluminate slag is 11CaO·7Al2O3·CaF2 phase with a low melting point. The original Na3AlF6 phase, which is the cause of leachable fluoride in secondary aluminum dross, disappears totally, and there is no water-soluble fluoride detected in the leaching toxicity detection. The research indicates that the process of preparing premelted calcium slag from secondary aluminum dross is feasible, which provides a helpful reference for the resource utilization of secondary aluminum dross.

Parameters Affecting the Precipitation of Al Phases from Aluminate Solutions of the Pedersen Process: The Effect of Carbonate Content

Leaching experiments were performed in calcium aluminate slag with a high-sodium carbonate adaptation of the Pedersen process. A theoretical thermodynamic study of the pregnant leaching solution was conducted to specify the thermodynamically favored species that exist within. Using the HSC 9.0 software, a carbonation process simulation (neutralization of the aluminate solution with CO2 gas) was simulated. Laboratory carbonation experiments were conducted to verify the theoretical predictions. According to the thermodynamic study, at temperatures below 50 °C gibbsite precipitates in the first stages of carbonation and then is transformed to dawsonite. Temperatures over 65 °C favor the direct precipitation of dawsonite. The same route (thermodynamic analysis, carbonation simulation, and experimental verification) was followed by a synthetic solution containing lower amount of sodium carbonate to prove that dawsonite precipitation occurred as a result of the high free carbonate content, to investigate the effect of temperature and to precipitate alumina hydrate phases.Graphical

Optimization of hydrocalumite preparation under microwave irradiation for recovering aluminium from a saline slag

Aluminium was successfully extracted by treating an aluminium slag with aqueous NaOH under reflux conditions. This solution was purified by precipitation of silicon species by addition of HCl up to pH = 1, and used for preparing hydrocalumite (Ca2Al(OH)6Cl·2H2O) by the coprecipitation method. The effect of temperature on the properties of hydrocalumite prepared under microwave (MW) irradiation was studied. Characterization of the obtained solid was carried out by powder X-ray diffraction (PXRD), thermal analysis, FT–IR spectroscopy, chemical analysis, electron microscopy and N2 adsorption–desorption at −196 °C. The results showed that the use of the extracted aluminium solution allowed to obtain hydrocalumite by the coprecipitation method and that the temperature of the MW ageing treatment had a large effect on the formation of side phases, in addition to hydrocalumite. The results here reported demonstrate that formation of hydrocalumite is an effective method for the recovering of aluminium from its waste.

Obtaining Calcium Sulfoaluminate Using Aluminate Waste

In this work, studies have been carried out to replace bauxite with aluminate slags. Compounds of raw mixtures without use of fossil aluminate materials with different gypsum content have been developed. Instability of assimilation of anhydrite into calcium sulphoaluminate has been established. X-ray phase analysis has shown a weak dependence of increase in the firing temperature and increase in the yield of the main mineral C3A3·CŜ. Results of the study allow us to conclude that it is possible to obtain high-quality calcium sulphoaluminate (SAC) based on technogenic aluminate raw material.

Effect of cerium oxide on the structure of silicate melt and aluminate melt

The effect of Ce2O3 on the structure of silicate melt and aluminate melt was investigated. Ce2O3 played an opposite role in the two different systems. With the increase of Ce2O3 mole fraction in the silicate slag, the total proportion of QSi3 and QSi2 structural units with a high degree of polymerization will increase, and the complexity of the network will increase. With the increase of the Ce2O3 mole fraction in the aluminate slag, the relative proportion of [AlO4]-tetrahedron that acts as a network former was decreased and then stabilized. The relative proportion of the network modifier [AlO6]-octahedron was increased and then gradually approached a stable distribution. The degree of polymerization of the slag decreased first and then become stable. The new CaO-Al2O3-based mold flux has good stability in its viscosity after absorbing Ce2O3, it will be in favor of solving the mismatch of mold flux for rare earth steel continuous casting.

Magnetite concentrate from coal fly ash of Kashirskaya GRES- the raw material for the production of metal products by reduction smelting

Coal fly ash is a hazardous waste of heat power engineering. The complex processing of it includes several stages, such as carbon flotation and magnetic separation of iron. This study focuses on carbon extraction by flotation method and iron by magnetic separation method from Kashirskaya GRES coal fly ash with subsequent reduction smelting of it. At optimal conditions were obtained carbon concentrate with 37% C and magnetic concentrate with 61% Fe2O3. The high-quality steelmaking pig iron with low P and S and high alumina slag were obtained at 1400 °C after reduction smelting mixture magnetic, and carbon concentrates.

Effect of temperature on the initial properties of calcium sulfoaluminate binders synthesised at 1100°C

ABSTRACT In this investigation, it was studied the effect of curing temperature on the mechanical properties of pastes made with calcium sulfoaluminate cements synthesised from industrial wastes at a relatively low temperature of 1100°C. Fluorgypsum, fly ash, aluminium slag and calcium carbonate were used as raw materials. The main phases of synthesis were calcium sulfoaluminate and gehlenite. Pastes were prepared with different water/cement ratios, 15–25 wt-% hemihydrate and cured at 20 and 40°C. It was found that with higher total amounts of sulphates and increase in temperature, compressive strength is enhanced in the first days of curing and setting times decreased. Ettringite was found to be the main reaction product forming dense structures over time. Calcium sulphates hydration changed the ettringite formation causing fluctuations in the strength development, nevertheless, in some cases the strength surpassed 40 MPa at 28 days. Microstructures and hydration products were studied by SEM and XRD.

Utilization of waste phosphate aluminum slag for cement manufacture

The objective of this study was to investigate the feasibility of application of waste phosphate aluminum slag (PAS) for cement manufacture. To recycle waste PAS and minimize adverse effects on cement hydration induced by phosphate, NH4OH was used to purify PAS. X-ray diffraction (XRD) analysis was used to determine to confirm the removal of harmful phosphate. The effect of PAS on the hydration product composition, heat release and compressive strength was also investigated. The results demonstrated that NH4OH was effective in removing harmful AlPO4 in PAS and 10% NH4OH was considered as the optimal treatment concentration. In addition, the purification of NH4OH alleviated the delay in cement hydration caused by AlPO4 and the heat release curve of purified PAS (PPAS) cement tends to that of OPC. Moreover, the compressive strength of PPAS mortar at 28 days was 49.4 ​MPa, which is 18% higher than the compressive strength of PAS mortar. PAS purified by NH4OH can be applied to cement manufacturing.

Effect of P2O5, CaF2 and Basicity on the Viscosity and Structure of La2O3-Bearing Calcium–Silicate–Aluminum Slag System

Effect of P2O5, CaF2 and Basicity on the Viscosity and Structure of La2O3-Bearing Calcium–Silicate–Aluminum Slag System