Solubility Of MgO Research Articles

Effect of CaO/Al2O3 Ratio in Fluorine‐Free Refining Slag with Low Basicity on the Cleanliness of SWRS82B Steel

A fluorine‐free quaternary CaO–Al2O3–SiO2–MgO refining slag for SWRS82B coil steel is studied by considering the requirements of the steel wire. Laboratory experiments are conducted to study the equilibrium and kinetics of steel–slag reactions. The physical and chemical properties of refining slags, including the melting temperature, viscosity, and MgO solubility, are estimated by FactSage7.2 calculation. The cleanliness of SWRS82B steel refined by slags with a basicity of 1 and C/A ratio in the range of 1.36–7.13 is studied systematically. The plasticity of inclusions is studied by phase diagram and Young modulus calculation. Deoxidizing capacity and desulfurization capacity of refining slags are discussed by kinetic calculation of steel–slag reactions based on FactSage7.2 macro‐editing and the kungliga tekniska högskolan model. Slag with a composition of 42%CaO–47%SiO2–4%Al2O3–7%MgO has the best refining effect, in which impurity elements are lowest and plastic inclusions with the smallest size and least quantity are obtained. The impurity elements oxygen and sulfur in steel can be controlled for 29 and 75 ppm, respectively. The average size of inclusions is 1.54 μm. The majority of inclusions are in a liquid state at 1600 °C and Young modulus of the inclusions ranges from 99.78 to 152.87 GPa.

Corrosion of MgO–C Refractory with Ladle Slags

Herein, MgO–C refractory brick is immersed into the molten ladle slags with various CaO/Al2O3 ratios (located in the range of 0.56–0.78 and 1.99–1.36) and SiO2 addition from 1 to 20 wt%, at two temperatures of 1550 and 1650 °C. After the interaction with the slag with a CaO/Al2O3 ratio range of 0.56–0.78, the MgAl2O4 phase with various sizes is found to form in the solidified slag layer adhering to the MgO–C sample surface, and a layer consisting of MgAl2O4 on the interface of MgO–C brick is observed. For the slag with the CaO/Al2O3 ratio range of 1.99–1.36, a small amount of minor size of MgAl2O4 particle is detected only with 20 wt% of SiO2 addition. Instead of a formation of the MgAl2O4 layer, the Fe phase containing Mn, metallic Ti, and Si is scattered on the side of the solidified slag layer. The corrosion is more pronounced in the slag with a high CaO/Al2O3 ratio and is enhanced via the addition of SiO2 along with the increased solubility of MgO. The increased solubility of MgO in the slag with increasing SiO2 has also been predicted via FactSage.

Influence of Ultrahigh Dilution Treatment of the Charge on the Growth and Spectroscopic Properties of Nd:MgMoO4 Potential Laser Crystal

The influence of the charge treatment by ultrahigh dilution (UHD) technology on oxide single crystals grown by the Czochralski technique was studied for monoclinic MgMoO4 crystals doped by 1 at. % of Nd3+ ions. The series of 10 Nd:MgMoO4 crystals was grown from the charges that were subjected to UHD treatment, as well as from the charges treated with two types of control or with no special treatment at all. The grown crystals were studied by X-ray powder diffraction analysis, inductively coupled plasma atomic emission spectroscopy, mass-spectrometry, optical absorption, emission spectroscopy and luminescence kinetic analysis. We found that: (i) wetting of MgO + MoO3 mixture by a water-ethanol solution before calcining leads to some enrichment of the mixture with MoO3, whereas the wetting of the charge after the calcining leads to some enrichment of it with MgO; (ii) congruent melting composition of MgMoO4 crystal is in the field of some MoO3 excess; (iii) the solid-phase solubility of the excess MoO3 in MgMoO4 probably does not depend on temperature, whereas the solid-phase solubility of the excess MgO in MgMoO4 crystal depends on temperature. We suggest that the corresponding solidus line passes through the range of retrograde solubility; (iv) the crystals grown within this range are characterized by the enhanced Nd3+ segregation coefficient between the crystal and the melt (approximately 0.006 versus 0.004); (v) unit cell parameters of MgMoO4 crystal with the excess of MoO3 are larger than those of the crystal of the stoichiometric composition and of the crystal with the excess of MgO; (vi) the shapes of the optical absorption and luminescence spectra of Nd:MgMoO4 crystal do not depend on the charge treatment; (vii) luminescence decay kinetics are single-exponential for all the studied crystals, the luminescence decay time being different for the crystals grown from the charges that underwent different types of treatment; (viii) the luminescence intensity of Nd:MgMoO4 crystal grown from the charge that underwent UHD treatment before calcining (solid-phase synthesis) is reduced by an order of magnitude in comparison with the other studied crystals.

Effects of MgO doping concentration on densification and microstructure of flash sintered α-Al2O3 ceramics

The effects of MgO doping concentration on the sintering behavior of Al2O3 ceramics in flash sintering were studied. The relative density, grain size and oxygen vacancies of the flash sintered samples doped with different amounts of MgO were characterized. The results showed that the relative density and grain size increased with MgO concentration up to 0.25 wt%, and then decreased with further increasing MgO content. These were coincident with the changes in oxygen vacancies in the flash-sintered samples. Flash sintering behaviors of 0.25 wt% MgO doped Al2O3 disc were different from those in conventional sintering, where the grain growth was inhibited when the MgO content is 0.25 wt%. The results can be explained by the fact that the higher oxygen vacancies in the flash sintered sample than that in the conventional sintered one, due to the applied electric field/current in flash sintering enhancing the solubility of MgO in Al2O3.

Effect of MgO on phase equilibria of copper matte and SiO2-saturated iron silicate slag in smelting complicated copper resources

The effect of MgO on the phase equilibria between matte and tridymite-saturated FeOx−SiO2−MgO slag was investigatedusing high-temperature equilibration and microanalysis technique. The results showed that at 1300 °C and p(SO2) of 10 kPa, the presence of MgO reduced the FeO activity of the slag, leading to the decrease in the oxygen partial pressure (p(O2)) over the slag and the Cu solubility in the slag. Due to the lower FeO activity, FeS was oxidized from matte into slag, increasing the Cu concentration of the matte. In high-SiO2 concentrationslags, excessive MgO in the liquid slag recrystallized as solid olivine (Mg2SiO4−Fe2SiO4), increasing the slag viscosity and copper losses in the slag. The maximum MgO solubility in the FeOx−SiO2−MgO slag increased from 3 wt.% to 8 wt.% when the temperature raised from 1200 to 1300 °C under p(O2) of 10−6 kPa. At higher MgO content, the slag composition could be optimized by increasing temperature and adding SiO2 flux to maintain a fully molten slag or avoid high proportions of solids.

An Eco-Friendly Process to Extract Hydroxyapatite from Sheep Bones for Regenerative Medicine: Structural, Morphologic and Electrical Studies

Hydroxyapatite (HA) promotes excellent bone regeneration in bone-tissue engineering, due to its similarity to bone mineral and its ability to connect to living tissues. These factors promote the osteointegration process. This process can be enhanced by the presence of electrical charges, stored in the HA. Furthermore, several ions can be added to the HA structure to promote specific biological responses, such as magnesium ions. The main objective of this work was to extract hydroxyapatite from sheep femur bones and to study their structural and electrical properties by adding different amounts of magnesium oxide. The thermal and structural characterizations were performed using DTA, XRD, density, Raman spectroscopy and FTIR analysis. The morphology was studied using SEM, and the electrical measurements were registered as a function of frequency and temperature. Results show that: (i) an increase of MgO amount indicates that the solubility of MgO is below 5%wt for heat treatments at 600 °C; (ii) the rise of MgO content increases the capacity for electrical charge storage; (iii) sheep hydroxyapatite presents itself as a natural source of hydroxyapatite, environmentally sustainable and low cost, and promising for applications in regenerative medicine.

(Digital Presentation) Effects of Oxide Ion and Sulfate Ion on Mg Metal Deposition in Molten Salt Electrolysis

With the growing demand for Mg, it is desirable to establish domestic Mg production in Japan. The author focuses on Mg production by molten salt electrolysis using MgCl2 extracted from concentrated seawater. The control of the contamination to the MgCl2 product should be a key issue, and also the influence of the contamination on the Mg production must be clarified. In this study, the effects of oxide ions and sulfate ions on Mg metal electrodeposition in molten salt have been investigated.Molten MgCl2-NaCl-CaCl2 with trace CaF2, for the new IG method was used as the bath, and MgO (0~1.0mass%) or Na2SO4 (0.025~0.5mass%) was added to the bath. A Mo wire with BN cover was used as the working electrode, and a carbon rod was used as thecounter electrode. The reference electrode was a Ag/AgCl couple in the same bath in a mullite tube, and its potential was calibrated against the Mg deposition potential. Experiments were done at 700°C in an Ar atmosphere. The cathodic behavior investigated by cyclic voltammetry, and then potentio-static electrolysis was performed. Visual observation was carried out during the cyclic voltammetry and potentio-static electrolysis. The electrodeposits after rinsing was evaluated by XRD, XRF, SEM-EDX and ICP, and the cathodic current efficiency was calculated from the weight of the deposit and the quantity of electricity.It was showed that the cathode reaction did not depend on MgO addition. Electrodeposits were obtained by potentio-static electrolysis regardless of MgO addition, and current efficiency was not significantly affected by MgO addition. The purity of Mg metal deposit was not influenced by the MgO addition in the bath, too; Mg metal above 99.9 mass% was obtained regardless of MgO addition, and the Na, K and Ca contents did not change evidently. It was suggested that the contamination of MgO to MgCl2 extracted from condensed seawater did not affect the Mg metal deposition directly. However, our previous work showed that the solubility of MgO in the bath was limited, so the MgO content in MgCl2 must be controlled.The result of cyclic voltammetry showed that cathodic current peaks appeared around 1V (vs. Mg deposition potential, the same hereinafter) and 0.5V by the addition of Na2SO4, and these peak currents were increased as increasing the added amount. Since MgO and MoS2 were detected after the potentio-static electrolysis at 1.2V and 0.5V, respectively, the cathodic current around this potential region seemed not to correspond to Mg metal deposition. Magnesium metal was obtained by the potentio-static electrolysis below 0.0V even in the bath containing sulfate ion, but the current efficiency got worse rapidly as the added amount of Na2SO4 increased. The surface of Mg metal deposit became rough with Na2SO4 addition, which caused the deterioration in its purity. It was shown that the contamination of even a small amount of sulfate to MgCl2 gave a negative influence to Mg metal deposition, so the control of its contamination should be important in the Mg metal production from concentrated seawater.This work was performed under the support of the commissioned work (JPNP14004) of the New Energy and Industrial Technology Development Organization (NEDO).

Source and Transformation of MgO-Based Inclusions in Si-Mn-Killed Steel with Lime-Silicate Slag

The origin, evolution, and formation mechanism of MgO-based inclusions in Si-Mn-killed steel were studied in industrial trials with systematical samplings of the refining ladle, casting tundish, and as-cast bloom. In the present study, there were large numbers of MgO-based non-metallic inclusions, which started to form in the LF final process, and the MgO content in the lime-silicate slag increases from LF to VD process. The reason for the formation of MgO-based inclusions in refining process was analyzed using FactSage8.1 software. It was found that MgO-based inclusions were caused by the violent reaction between the slag and steel and the serious erosion of MgO-C refractory. The MgO solubility decreased in the lime-silicate slag and precipitated the periclase phase with basicity increasing. The solubility of MgO increased with an increase in the temperature. Measures were taken to optimize the refining process based on the above result. By increasing the slag basicity and increasing the content of MgO in the slag, erosion of the MgO-C refractory was reduced and the number of MgO-based non-metallic inclusions decreased from 0.2 to 0.04 per square millimeter.

Integrated experimental and thermodynamic modeling study of phase equilibria in the ‘CuO0.5’-MgO-SiO2 system in equilibrium with liquid Cu metal for characterizing refractory-slag interactions

An integrated experimental and thermodynamic modeling study of the phase equilibria in the ‘CuO0.5’-MgO-SiO2 system in equilibrium with liquid Cu metal has been undertaken to better understand the reactions between MgO-based refractories and liquid slag in copper converting and refining processes. New experimental phase equilibria data at 1250–1680 °C were obtained for this system using a high-temperature equilibration of synthetic mixtures with predetermined compositions in silica ampoules or magnesia crucibles, a rapid quenching technique, and electron probe X-ray microanalysis of the equilibrated phase compositions. The system has been shown to contain primary phase fields of cristobalite (SiO2), tridymite (SiO2), pyroxene/protoenstatite (MgSiO3), olivine/forsterite (Mg2SiO4), periclase (MgO), and cuprite (Cu2O). Three regions of 2-liquid immiscibility were found—two in the high-silica range of compositions above the cristobalite primary phase field (close to ‘CuO0.5’-SiO2 and MgO–SiO2 binaries) and one in the low-SiO2, high-‘CuO0.5’ compositional region above the periclase and olivine phase fields. The results obtained in this study indicate that silica in high-copper refining slags likely led to olivine and pyroxene phase formation, increased solubility of MgO in liquid slag, and decline in the performance of MgO-based refractories. New experimental data were used in the development of a thermodynamic database describing this pseudo-ternary system.

Effect of temperature on the slag/refractory interfacial reaction with directed reduced iron (DRI) addition in an electric arc furnace (EAF) process: Diffusional growth of magnesiowüstite layer by Boltzmann-Matano analysis

This study investigated the effect of temperature (1550–1650 °C) on the electric arc furnace (EAF) slag and magnesia refractory interfacial reaction with 20% direct reduced iron (DRI) addition as an alternative iron source in an Ar atmosphere. Variations in MgO content from initial to final stage were proportional to the temperature, indicating that MgO degradation by molten EAF slag was affected by the concentration gradient between initial and saturation conditions depending on temperature. In addition, the temperature affected MgO content more dominantly than DRI did. In other words, temperature control in an EAF process using DRI is relatively more important than the control of DRI itself for preventing MgO refractory degradation. The magnesiowüstite (MW) intermediate layer thickness and MgO refractory dissolution depth increased as the temperature increased because MgO solubility in molten EAF slag is proportional to temperature. Finally, the inter-diffusivity (D˜Fe−Mg, m2/s), which was estimated by Boltzmann-Matano analysis, ranged D˜Fe−Mg=10−12.0−10−12.5 and logD˜Fe−Mg generally decreased with decreasing temperature. The activation energy was found to be approximately 240 kJ/mol. Therefore, it can be concluded that suitable control of temperature in an EAF process using DRI is important to minimize refractory degradation.

Interfacial reactions between magnesia refractory and electric arc furnace (EAF) slag with use of direct reduced iron (DRI) as raw material

Interfacial reactions between the electric arc furnace (EAF) slag, i.e., CaO–SiO 2 –FeO–MgO–Al 2 O 3 –MnO system, and the magnesia refractory as a function of direct reduced iron (DRI) addition (0, 10, 20, 30 wt%) were investigated at 1550 °C under an Ar atmosphere. MgO solubility increases with increasing DRI content by decreasing basicity (i.e., CaO/SiO 2 ratio), which is due to an increase in SiO 2 supplied from DRI. The measured MgO content was always lower than the theoretical MgO saturation level irrespective of DRI content because the magnesiowüstite (MW) intermediate layer, which formed at the slag/refractory interface, retarded the direct dissolution of the refractory by acting as a self-protective layer. The thickness of the MW intermediate layer and dissolution depth were proportional to DRI content. However, the penetrativity decreased with increasing DRI content by decreasing the fluidity of the slag. Several kinetic parameters were estimated, including the dissolution rate constant of the MW intermediate layer, the dissolution rate of the MgO refractory, and the rate constant of MW growth. Dissolution of MgO refractory is controlled by the dissolution of the MW intermediate layer. Increasing the growth rate is very important for protecting refractory after the formation of a MW intermediate layer. In addition, we provided a schematic diagram of the slag/refractory interfacial reaction phenomena that compares situations of low and high DRI content. The results of the present study show that it is necessary to control DRI content to minimize refractory degradation during the EAF process. If a large amount of DRI must be used in the EAF process, then MgO content in the slag should be at the saturation limit at first, which accelerates growth of the MW intermediate layer.

Development of Magnesium Fertilizer Replacing Kieserite from Bio-Physico-Chemical Activated Dolomite

All plants, especially cocoa and oil palm, require magnesium (Mg) along with other macro- and micro-nutrients. Kieserite as the most common Mg-supplying fertilizer for crops is still imported for Indonesia due to lack of natural deposits in the country. On the other hand, dolomites (CaMgCO3) are found abundantly and mostly used as liming material due to low MgO content and solubility as well. Many efforts have been carried out since a century ago to convert dolomite into Mg fertilizer substituting kieserite. However, there are no efficient processes available yet and therefore it is the objective of this study to develop a potentially efficient process by employing bio-physico-chemical activation approach in converting dolomite into kieserite-like product. A series of experiments were conducted by using a calcinated dolomite from Sidayu, Gresik, East Java, reacting with H2SO4, and inoculating with Mg-solubilizing microbes. An 80-mesh calcined dolomite powder was reacted with water at 1:3 ratio (% w/v) and after one hour stirring added with technical grade H2SO4 improving 27.7% MgO content from 18% to 23%. The formula was then tested its effectiveness for cocoa and oil palm seedlings in the greenhouse for three and six months, respectively. By combining NPK fertilizer at standard dosage with the formula of Mg-fertilizer at 75% of kieserite rate yielded the highest performances by six-month-old oil palm seedlings in a greenhouse experiment. To obtain conclusive results under field conditions, the formula was tested at field experiments using immature and mature oil palm trees. At 0.9 kg/tree/year dosage, the Mg-fertilizer formula was superior to conventional kieserite at 1.6 kg/tree/year rate in supporting vegetative growth of immature oil palm. From the mature oil palm trial, it can be concluded that the use of the new formulated Mg-fertilizer at 50% rate of conventional kieserite (2 kg/tree/year) resulted in an insignificant different yield of fresh fruit bunches (FFB) compared to standard kieserite dosage.

Study on the protective effect of the dense slag layer on converter lining

AbstractIn this paper, the protective effect of the dense slag layer on the furnace lining is investigated through comparative sampling of residual bricks. The physical and chemical properties of the residual brick samples were tested, and the result showed that sample NO.1 had 7.9% higher bulk density, 37.6% lower apparent porosity, 41% higher flexural strength, and 14.3% higher compressive strength than sample NO.2. The residual carbon of sample NO.1 was normal, while the residual carbon oxidation loss rate of sample NO.2 was 36%. X‐ray diffractomer (XRD), optical microscope (OM), and EDS: scanning electron microscope‐Energy Dispersive Spectrometer (SEM+EDS) were adopted to study the physical phase composition, microscopic morphology, and mineral phase composition and distribution of the dense slag layer. The slag layer was found to be highly alkaline and oxidizing, with 58–73% RO phase, 17–26% phosphorus‐rich phase, and 6–16% base phase in the mineral phases. The FactSage 8.1 thermodynamic software was used to simulate and calculate the melting temperature of each mineral phase. The presence of the high melting point phase and RO phase in the dense slag layer is an important reason for its ability against high temperature and high oxidation. The formation of the dense slag layer was related to the saturated solubility of MgO. The results indicated that the extremely unstable saturated solubility of magnesia had a greater effect on the dissolution rate of magnesia particles. External temperature and oxidation changes are important factors affecting the saturated solubility of MgO in the slag layer, and reducing the internal‐external heat and mass transfer rate could effectively improve the service life of the furnace lining.

Thermodynamic study on the formation of Mg(Al1-x,Fex)2O4 between single-crystal MgAl2O4 and FetO-containing slag at 1550°C

Herein, the effects of FetO content and basicity (CaO/Al2O3) on MgO solubility in calcium aluminate slag were evaluated. The experimental results revealed that the dependence of MgO solubility on basicity reversed across the equilibrium region as the phase changed from MgO to spinel. Meanwhile, a dense layer of Mg(Al1-x,Fex)2O4 solid solution formed at the interface between the single-crystal MgAl2O4 and FetO-containing MgO-saturated slag. Thermodynamic evaluation of the spinel solid solution formation indicated that the solid solubility of ferric ions (Fe3+) in the reaction layer was dominated by the redox equilibria of ferrous (Fe2+) and ferric ions in the slag. The standard Gibbs free energy change (ΔG°) of the formation of Mg(Al1-x,Fex)2O4 solid solution was derived considering both the energy change in mixing (ΔG°Mix) from the configurational change and the cation distribution owing to the inversion in the spinel, as well as a chemical reaction (ΔG°Rxn) with the FetO-containing slag. The dissolution mechanism via the substitution of cations, as inferred from these calculations, is discussed in detail.

Influence of Slag Composition on the Distribution Behavior of Cu between Liquid Sulfide and Cu-Containing Multicomponent Slag via Thermodynamic and Kinetic Assessment

At present, copper smelting slag is not effectively recycled and is wasted. Copper smelting slag contains FexO at more than 40 mass%. For the utilization of copper slag as a Fe resource, it is necessary to separate the Cu in the slag. For copper recycling from slag, FeS-based matte can be introduced to use sulfurization to concentrate Cu from the slag into the sulfide and finally recover the copper. In a previous paper, a kinetic model was developed to simulate the coupled reactions between the multicomponent slag and FeS-based matte by using previously reported thermodynamic data. Building on this work, we carried out equilibrium experiments to supplement the thermodynamic data used in the previously developed model. An empirical formula for the Cu2O activity coefficient of Cu2O-FeOX-CaO-MgO-SiO2-Al2O3 system slag was obtained. In addition, the effect of alumina content in the slag on the Cu2O activity coefficient in the slag was investigated. The model was also supplemented to account for MgO solubility. By the developed model and the industrial conditions, we investigated the effect of slag composition on the behavior of Cu between matte and Cu2O-FeOX-CaO-MgO-SiO2-Al2O3 system slag for the copper loss.

Prediction of adequate pH and Mg2+dosage using an empirical MgO solubility model for struvite crystallization

The struvite crystallization process can recover struvite crystals as valuable slow-release fertilizers from raw water, including high phosphate and ammonium ions. MgO can be used as a magnesium source and an alkaline chemical simultaneously; however, it is difficult to control the dissolved Mg 2 + concentration because of its insufficient and unpredictable solubility. The purpose of this study was to estimate MgO solubility and determine the optimal operating conditions of pH and Mg 2 + dosage during struvite crystallization. An empirical MgO solubility prediction model was devised to dose an adequate amount of MgO slurry in accordance with the properties of raw water. MgO solubility was determined by H + ions donated by NH 4 + , HCO 3 − , and H 2 PO 4 - as the pH increased in the solution. It was found that the molar ratio of donated H + to dissolved Mg 2 + converged to 2:1. This model was verified by performing jar-tests using digested sludge filtrate. When adjusting to a pH of 8.0–9.3 using only MgO, the predicted Mg 2 + concentrations using the model were compared to the measured Mg 2 + concentrations, and they coincided well within the maximum error of 5.7%. This model was applied to determining the operating conditions of pH and Mg 2 + dosage. As a result, considering phosphate removal efficiency higher than 90%, it was feasible to simultaneously achieve an Mg/P molar ratio of 1.3–1.5 and a pH of 8.2–8.5 by only using MgO. Therefore, MgO is recommendable as an appropriate magnesium source and alkali supplier in the struvite process based on experimental jar-tests and the empirical MgO solubility model. • An empirical MgO solubility prediction model was devised and applied to struvite crystallization process. • MgO solubility was predicted using pH, and concentrations of acidic ions. • The optimal conditions of pH and Mg 2 + dosage were determined by this model.

Study on Saturated Solubility of MgO in Converter Vanadium Slag

This article investigated the saturated solubility of MgO in converter vanadium slag and its influencing factors. The experimental results of MgO dissolution equilibrium are consistent with the theoretical calculation results. The results show that in MgO saturated vanadium slag, MgO mainly exists in MgV2O4 and MgSiO3. The increase of V2O3 content or the decrease of the FeO/SiO2 ratio is beneficial to increasing the saturated solubility of MgO in the FeO-SiO2-V2O3 slag system. The saturated solubility of MgO in vanadium slag increases from 7.5 to 8.0 wt.% when the temperature increases from 1633 to 1753 K. In addition, the solubility of MgO also increases with the increase of TiO2 and Al2O3 content and decreases with the increase of MnO content.

Applicability of the Electrochemical Oxygen Sensor for In-Situ Evaluation of MgO Solubility in the MgF2–LiF Molten Salt Electrolysis System

The measurement and evaluation of MgO solubility in the molten fluoride system is of significant importance in the recently proposed magnesium electrolysis reduction process. In the present study, an in-situ quantitative method of evaluating the concentration of dissolved MgO in molten fluoride is proposed. The MgO solubility in the 32.8MgF2–67.2LiF system was measured at 1083 and 1123 K using a combustion analyzer. MgO saturation was achieved in under 2 h, and higher solubilities were observed as the temperature increased. Thermodynamic assessment was carried out in order to ascertain the applicability of the electrochemical oxygen sensor, which indicated that the logarithm of oxygen concentration in molten fluoride has a linear relationship with the measured electromotive force (EMF) potential. The EMF potential of the controlled MgO concentration was measured, and a straight calibration line was obtained, describing the relationship between the measured EMF and the logarithm of MgO concentration. From the obtained calibration line, MgO concentration in the 0.4 wt% MgO was calculated. The calculated value was 0.44 wt% that was in excellent accordance with the controlled MgO concentration of 0.4 wt%, verifying the practical applicability of electrochemical oxygen for the in-situ monitoring and evaluation of MgO solubility in the electrolysis magnesium reduction process.

Effects of SiO2 and B2O3 on MgO solubility and ionic structure in MgO-and-spinel doubly saturated aluminate slag

The effects of SiO2 and B2O3 on the ionic structure of CaO–Al2O3 binary slag under the MgO-and-spinel doubly saturated (MSDS) condition were evaluated by measuring the MgO solubility of the slag. The activity coefficient of AlO45− in the slag was deduced by evaluating the equilibrium constant of the ionic reaction. In addition, the proportion of each bridging oxygen (BO) linkage species and the enthalpy of solution with the 4-coordinate Al ion (4Al) were derived by combining the Al avoidance model with the 11B and 27Al magic angle spinning nuclear magnetic resonance spectra results. The enthalpies, activity coefficient of AlO45−, and enthalpy of the solution with 4Al had good agreement in BO-dominant regions. From these results, the effects of the structural properties of slag on the stability of AlO45− and MgO solubility in the MgO-and-spinel doubly saturated slag were investigated in detail.

Corrosion mechanism of magnesia-chromite refractories by ZnO-containing fayalite slags: Effect of funnel glass addition

An efficient approach for lead extraction from waste funnel glass through the lead smelting process has been proposed. To clarify the effect of funnel glass addition on the degradation of magnesia-chromite refractories by ZnO-containing fayalite slag, the corrosion behavior of magnesia-chromite refractories in lead smelting slags with different funnel glass additions from 0wt% to 40wt% was tested. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) was used to acquire the microstructural information of the worn refractory samples. Experimental results showed that the corrosion of magnesia-chromite refractory consisted predominantly of the dissolution of MgO into slag. ZnO and FeO reacted with periclase and chromite to form (Zn,Fe,Mg)O solid solution and (Zn,Fe,Mg)(Fe,Al,Cr)2O4 spinel, respectively. With the addition of funnel glass, the solubility of MgO increased whereas ZnO levels remained stable, thereby resulting in a reduced Mg content and an elevated Zn and Fe content in the (Zn,Fe,Mg)O solid solution and the (Zn,Fe,Mg)(Fe,Al,Cr)2O4 spinel. Considering the stability of the (Zn,Fe,Mg)O solid solution layer and the penetration depth of the slag, the optimal funnel glass addition for lead smelting was found to be 20wt%.