MnO In Slag Research Articles

Effect of Mg treatment on inclusion behaviors in 430 ferritic stainless steel during solidification

To understand the effect of Mg treatment on the precipitation, growth, and transformation of inclusions in 430 ferritic stainless steel during solidification, slag refining and Mg treatment experiments with different cooling methods were conducted at 1873 K (1600 °C). Experimental results showed that the oxide inclusions in 430 stainless steel without Mg treatment were mainly Al2O3–SiO2–MnO (slag phase), Al2O3–Cr2O3–MnO (spinel phase), high-Al2O3 (corundum phase) and CaO–SiO2–Al2O3–MnO (slag phase), while all of the oxides except CaO–SiO2–Al2O3–MnO inclusions transformed to MgO–Al2O3–Cr2O3–MnO (spinel phase) after Mg treatment. With water quenching, the average inclusion diameters were about 1.4 μm in both of the Mg-free and Mg-bearing steels, while they increased to approximate 3.1 and 1.9 μm after furnace cooling, separately. With the decrease of cooling rate from 26.2 to 1.24 K s−1, in the Mg-free steel, the average Al2O3 and Cr2O3 contents in the inclusion increased from 19.6 to 42.6 mass% and from 12.22 to 19.44 mass%, respectively, and the average SiO2 content decreased from 43.5 to 17.1 mass%. However, the average composition of inclusions in Mg-bearing steel was relatively stable and independent of cooling rate. A kinetic model was established with the solute micro-segregation model to predict oxide inclusion growth during cooling and solidification. Without and with Mg treatment, under a cooling rate of 1 K s−1, the calculated final sizes of the most stable oxide inclusions were 3.27 and 1.88 μm, respectively. The predicted average compositions and diameters of oxide inclusions were generally consistent with the experimental results.

Study of Manganese Recovery in the CaO-SiO<sub>2</sub>-MgO-Al<sub>2</sub>O<sub>3</sub>-MnO-Fe<sub>2</sub>O<sub>3</sub> System by Thermodynamic Simulation

The results of thermodynamic simulation of the manganese recovery in the CaO-SiO2-MgO-Al2O3-MnO-Fe2O3 system by carbon are presented. Parameters of the initial system are temperature range 1400-at a step of , a total pressure of 0.1 MPa, and N2. The composition of the oxide system is corresponded by the manganese ore (wt %) 1.1 MnO2, 44.3 MnO, 28.4 CaO, 9.3 SiO2, 5.4 MgO, 0.3 Al2O3, 11.2 Fe2O3 and silicomanganese slag. It contains (wt %) 16.3 MnO, 18.4 CaO, 52 SiO2, 7.8 MgO, 5.26 Al2O3, and 0.24 FeO. The amount of silicomanganese slag in the system was 0, 5, 12, and 25%. Carbon is used as a reducing agent. Its consumption is increased by 5% from the stoichiometry for the recovery of Fe and Mn and by 8% of the metal mass for the formation of iron, manganese, and silicon carbides. The simulation is carried out using HSC Chemistry 6.12 () software package. The thermodynamic characteristics of the Fe3C, Fe2O3, FeO, MnO2, Mn, Mn3C, Mn5C2, Mn7C3, Mn23C6, and SiC compounds existing in the database are refined. It was determined that an increase in the melt temperature from 1400 to increases the degree of manganese recovery (ηMn) for all compositions of the systems. An increase of the silicomanganese slag content in the mixture from 0 to 25% decreases ηMn from 89.3 to 85% at and from 95.8 to 91.5% at . The chemical composition of the high-carbon ferromanganese alloy is (wt %): 71.9-72.8 Mn, 16.6-17.9 Fe, 0.015-1.64 Si, and 9-. The simulation results can be used to develop a technology for producing a high-carbon ferromanganese when silicomanganese slag is involved in metallurgical processing.

Dissolution behavior of silica in molten CaO–SiO2–Fe2O3–MgO–MnO slag

AbstractThe modification of basic oxygen furnace (BOF) slag by adding silica can improve the properties of BOF slag for applications in the cement industry. The rapid dissolution of silica is essential to hot slag modification. In this work, the dissolution behavior of silica in the molten CaO–SiO2–Fe2O3–MgO–MnO system as synthetic BOF slag was investigated by using the traditional rotating cylinder technique. Effects of rotation speed, temperature, immersion time, and slag basicity on the silica dissolution were studied. Scanning electron microscopy equipped with energy dispersive spectrometer (SEM‐EDS) and FactSage simulations were employed to reveal the dissolution mechanism. It was found that the dissolution of the silica rod was affected by both the thermodynamic driving force and the slag viscosity. The silica dissolution rate in molten CaO–SiO2–Fe2O3–MgO–MnO slag increased with increasing the rotation speed and temperature, but first increased and then decreased when decreasing the slag basicity from 2.5 to 1.5. A linear correlation between the logarithm of the dissolution rate and the logarithm of cylinder periphery velocity with a slope of 0.44 was observed, indicating the mass transfer within the boundary layer as the dissolution rate determining step. A direct dissolution way was found during the dissolution of silica in molten CaO–SiO2–Fe2O3–MgO–MnO slag.

Viscous behavior of high-FetO-bearing slag systems in relation to their polymeric structural units

The effect of basicity (CaO/SiO2 mass ratio) and FetO on the viscous behavior of CaO–SiO2–FeO–Al2O3–MgO–MnO slag was investigated via stepped-temperature viscometry (1873–1473 K) to predict the thermophysical properties of high-FetO-bearing molten slag. The basicity and FetO contents were varied to determine the constitutional effect of the slags on the physical properties and ionic structure. At low FetO contents (below 15 wt%), the viscosity of high-FetO-bearing slags exhibited a strong dependence on basicity. However, at high FetO contents (above 15 wt%), the viscosity decreased as the FetO content increased, indicating a strong FetO dependency. This behavior was attributed to the change in activation energy as the dominant polymeric structural unit (T–O–T; T = Si, Al, and Fe) varied depending on the equilibrated primary phase. In addition, to understand the change in the dominant polymeric structural unit depending on the FetO content, the relationship between the polymeric structural units and thermophysical properties of high-FetO-bearing slags was studied by analyzing the Fe3+/Fe2+ and nonbridging oxygen fractions of the slag melts.

Effect of Mn Content on the Reaction between Fe-xMn (x = 5, 10, 15, and 20 Mass pct) Steel and CaO-SiO2-Al2O3-MgO Slag

Medium- and high-Mn steels have excellent properties but are very difficult to be commercially produced because of the high content of some alloy elements. To enhance the understanding of the reaction between medium/high-Mn steel and refining slag which is significantly different from the conventional steels, steel and slag composition and the inclusions were investigated by equilibrium reaction between Fe-xMn (x = 5, 10, 15, and 20 mass pct) and CaO-SiO2-Al2O3-MgO top slag at 1873 K in the laboratory. Furthermore, the effect of Mn content on inclusion transformation and steel cleanliness was also explored. After slag–steel reaction, both contents of MnO in slag and Si in steel increased. Most MnO inclusions in master steel transformed to MnO-SiO2 and MnO-Al2O3-MgO. With the increase in Mn content, the amount share of MnO type inclusions decreased and that of MnO-Al2O3-MgO type increased. In addition, both the number density of observed inclusions and the calculated oxygen content in inclusions increased. Thermodynamic analysis indicates that the composition change of steel and slag and the transformation of inclusions are mainly the consequence of the reaction between Mn in molten steel and SiO2 and MgO in top slag. The dissolved Mn in medium/high-Mn steel presents a strong reactivity.

Elements distribution and interfacial structure of CaO-SiO2-10mass% MnO under CO-CO2-SO2-Ar gas

In this work, the interfacial element distribution and structure of CaO-SiO2-10%mass MnO slag was explored using the gas-slag equilibrium experimental method and XPS detection method at the temperature of 1873 K. Based on the full spectrum, the relative content of sulfur gradually decreases, the manganese has the same trend, while the calcium content keeps increasing. According to the analysis of the Mn2p and S2p spectra, it indicated that Mn and S exist as positive divalent (Mn2+) and negative divalent (S2-), respectively. The O1s fitting result indicates that the proportion of non-bridged oxygen (O-) increased, while that of bridged oxygen (O0) decreased with the etching time increased. The structural units obtained by Raman spectroscopy are closer to the evaluation data of the CaO-SiO2 system, while the interfacial structure information tends to the MnO-SiO2 system. Although CaS is thermodynamically more stable than MnS, the reason for the sulfur accumulation in the gas-slag interface is due to the d electron supplement from Mn. Thus, the concept of interface sulfide capacity is proposed. As the etching depth increases, the interface sulfide capacity decreases continuously. Comparing XPS and Raman, the structure has a gradient change trend at the gas-slag interface, which confirms the presence of the boundary layer at the gas-slag interface.

Kinetics of Slag Reduction in Silicomanganese Production

In this study, the reduction of three silicomanganese charges prepared from industrial raw materials was investigated under isothermal conditions between 1783 K and 1933 K (1510 °C and 1660 °C). The main reactions examined are MnO and SiO2 slag reduction following the chemical equations MnO(l) + C = Mn(l) + CO(g) and SiO2(l) + 2C = Si(l) + 2CO(g). The charges containing a combination of Assmang ore, Comilog ore, high-carbon FeMn slag with quartz were pre-reduced, melted to a MnO-SiO2-Al2O3-MgO-CaO quinary slag and reduced in presence of coke using a thermogravimetric set-up. The reduced slags were further analyzed using electro-probe micro-analysis to evaluate their MnO and SiO2 contents. It is observed that the reduction pathway occurred in two stages: a first slow and stable stage was followed by a rapid rate increase during the second stage. The rate change shift between the two stages was found to depend on the initial charge’s composition and the extent of reduction, but not on the temperature. Using an established rate equation, the kinetics of MnO and SiO2 reduction were modeled over the first stage. A good fit was obtained between simulated and experimental data.

Generation Mechanism of MgO and Al2O3 Inclusions in 51CrV4 Spring Steel Based on the Ion–Molecule Coexistence Theory

The presence of MgO·Al2O3 inclusions in 51CrV4 spring steel is detrimental to the alloy’s castability and fatigue properties. To effectively suppress these inclusions during production, accretions were collected from the immersion nozzle, and the MgO·Al2O3 inclusions in the steel billet were investigated. The generation mechanism of the inclusions was evaluated based on the ion–molecule coexistence theory, and the mass action–concentration model of CaO–SiO2–Al2O3–MgO–FeO–MnO slag was developed. Industrial experiments showed that nozzle clogging was primarily caused by MgAl2O4 spinel inclusions, and the MgO·Al2O3 spinel inclusions in the steel billet were investigated by non-aqueous electrolysis. The model calculation results indicate that the Mg content increased with an increasing basicity, CaO/Al2O3 ratio, and Al content during the ladle furnace (LF) process. In contrast, the Mg content decreased with increasing CO pressure under Ruhstahl-Hausen vacuum degassing process (RH) conditions.

Reaction of Al‐Killed Manganese Steel with Ladle Slag

Some laboratory experiments are carried out to investigate the reaction between manganese steel and ladle slag. It is found that as expected when the slag basicity [R = w(CaO)/w(SiO2)] is sufficiently low, for example, R < 4, the dissolved Al in conventional Al‐killed steel could reduce the SiO2 component of the slag. In the case of manganese steel grades [w(Mn): 6–20%, w(Al): 0.025%], the reduction of SiO2 by dissolved Mn becomes much more profound compared with that by dissolved Al, resulting in the increase of MnO in slag. When the Mn content is high enough, for example, w(Mn) = 20%, the reaction between the MgO in slag and the dissolved Mn in steel is also very evident. High slag basicity can restrain the reduction of SiO2 by dissolved Mn, but the reaction between MgO and Mn can still take place to generate MnO in slag. High‐basicity refining slag (R > 4) is recommended for manganese steel grades.

Effect of TiO<sub>2</sub> and MnO on Viscosity of Blast Furnace Slag and Thermodynamic Analysis

The effect of TiO and MnO on the viscous behavior and structure of CaO–SiO–MgO–AlO–TiO–MnO slags were studied using rotating cylinder method and FTIR spectroscopic analysis. Furthermore, the heat capacity and enthalpy change of the slag were calculated to clarify the influence of TiO and MnO on the heat quantity of the slag at elevated temperatures, and then the equilibrium temperatures and corresponding viscosities of the slag under various fixed heat quantities were also analyzed. The higher TiO and MnO contents resulted in lower viscosity. The FTIR results revealed that TiO and MnO depolymerized the slag by modifying the silicate network structure and breaking the linkage between the silicate and aluminate structure, while have little effect on aluminate structure of the slag. In the temperature range of interest, the enthalpy change of the slag increased with increasing TiO content, but remained basically unchanged with MnO additions. The fluctuations of the slag heat quantity had a significant influence on the slag temperature and viscosity. With the increase of TiO content, the equilibrium temperature of the slag at fixed heat quantity decreased and the corresponding viscosity increased. However, as the MnO content increased, the equilibrium temperature of the slag at fixed heat quantity was almost constant and the corresponding viscosity decreased.

Corrosion-erosion behavior of MgAl2O4 spinel refractory in contact with high MnO slag

Abstract The corrosion and erosion behavior of spinel refractory of different compressive strength has been investigated for refractories in contact with a high MnO slag for producing manganese ferroalloys. The finger rotating test (FRT) was adopted to evaluate the degradation behavior at 1550 °C under a rotating condition of 150 rpm. The sample with higher compressive strength (Sample C1) showed higher corrosion resistance than Sample C2. In Sample C1, the refractory progressively corroded from the surface to the inner region by chemical corrosion, while mechanical erosion of the refractory suddenly occurred in Sample C2 as a result of the penetration of the slag within the refractory and the rotating energy.

Effects of basicity, MgO and MnO on mineralogical phases of CaO–FeOx–SiO2–P2O5 slag

The selective separation phosphorous rich phase from steel slag could be an effective way to utilise the steel slag. The mineralogical phase after cooling of steel slag is essential to selective separation of steel slag. In the present work, the mineralogical phases of CaO–FeOx–SiO2–P2O5 slag after controlled cooling were investigated by X-ray diffraction and scanning electronic microscopy and energy dispersed spectroscopy technique. It was found that the heat treatment at 1573 K would lead to the precipitation of Ca2SiO4–Ca3P2O8 (C2S-C3P) solid solution for all samples. The heat treatment at 1273 K would lead to the precipitation of C2S-C3P, CaSiO3 and Fe2O3. The increase of basicity would promote the crystallisation of CaO–FeOx–SiO2–P2O5 slag. The Effects of additions of MgO and MnO on phase formations of CaO–FeOx–SiO2–P2O5 slag were also studied. Fe2O3 gradually transformed into MgFe2O4 and MnFe2O4 in slag after crystallisation with addition of MgO and MnO, respectively. The sizes of MgFe2O4 and MnFe2O4 crystals increased with increases of MgO and MnO content. The increase of MgO and MnO content would promote the precipitation of MgFe2O4 phase and MnFe2O4, respectively. The precipitation of crystals from slag during cooling was interpreted by the kinetic and thermodynamic factors. It was proposed that addition of MgO and MnO in slag would be beneficial to magnetic separation of steel slag.

Experimental investigation and thermodynamic modeling of vanadium, chromium and phosphorus distributions between FeO-SiO2-CaO-V2O3-Cr2O3-P2O5-MnO slag and semi-steel

The oxidation behavior of hot metal and the distribution ratios of V, Cr and P between FeO-SiO2 -CaO-V2 O3 -Cr2 O3 -P2 O5 -MnO slags and semi-steel have been studied by a combination of experimental measurements and thermodynamic modeling. The results indicate that the distribution ratio of P shows an obvious increasing tendency with the increase of slag basicity. In contrast to the P distribution, the effect of basicity on distribution ratios of V and Cr are negligible. The oxidation ratios of both V and Cr are higher than 84% and the oxidation ratio of P can achieve 40–60%. A thermodynamic model for calculating the mass action concentration of structural units and distribution ratios of V, Cr and P was developed based on the ion and molecule coexistence theory (IMCT). The calculated V and P distributions show good agreement with the experimentally measured data. The reliable agreement indicates that the IMCT model can be applied to predicting the element distributions for basic vanadium slag.

Effect of CaF2 Addition on the Silicothermic Reduction of MnO in Ferromanganese Slag

The effect of temperature and CaF2 (fluorspar) addition on the silicothermic reduction behavior of MnO in the CaO-40 pct MnO-SiO2 (C/S = 1.0) system, which is used to simulate high carbon ferromanganese (HCFeMn) slag, was investigated at 1773 K (1500 °C). The production of SiO2 was stoichiometrically balanced with the consumption of MnO in the slag phase in the CaF2-containing systems based on the reaction “[Si] + 2(MnO) = (SiO2) + 2[Mn],” whereas the SiO2 production was lower than the MnO consumption in the CaO-MnO-SiO2 ternary system, which may have originated from the production of SiO gas in the latter. From the temperature dependence of the mass transfer coefficient of SiO2, the activation energy of the silicothermic reduction process was determined to be about 217.9 kJ/mol, which was very close to the activation energy reported in the literature for mass transfer in the slag phase. The mass transfer coefficient of SiO2 exhibited a maximum value at 5 mass pct CaF2, which originated from an increase in the apparent viscosity of the slag due to the precipitation of solid cuspidine at CaF2 content greater than 5 pct. Consequently, the addition of fluxing additive CaF2 should be carefully determined, because an excess of CaF2 results in the formation of cuspidine during silicothermic reactions.

Effects of MnO and CaO/SiO2Mass Ratio on Phase Formations of CaOAl2O3MgOSiO2CrOxSlag at 1673 K and PO2=10−10 atm

The knowledge on distribution of mineralogical phase in slag is of vital importance to disposal and utilization of slag. Despite of certain amount (up to 5%) of MnO found in stainless steel slag, MnO distribution in phases of slag was not thoroughly investigated. In this work, phases of synthetic CaO–Al2O3–MgO–SiO2–CrOx–MnO slag with varied CaO/SiO2 and MnO content, which was soaked at 1673 K for 12 h, were determined by combining SEM-EDS and XRD technique. Phases for samples with CaO/SiO2 ratio of 1.5 and 1.3 were composed of Ca2SiO4, merwinite, spinel, and liquid phase, while phases for samples with CaO/SiO2 ratio of 1.1 are composed of spinel and liquid phase. The calculated phases by FactSage were in good agreements with observed ones by SEM-EDS and XRD. Manganese was found to be enriched in spinel and liquid, and chromium is enriched in spinel, and only negligible Cr could be found in merwinite and Ca2SiO4. The spinel increases in size with increasing of MnO and decreasing of CaO/SiO2 ratio. Disintegration was found in samples with increased MnO content and CaO/SiO2 ratio. The size of Ca2SiO4 crystal increases in size with increase of MnO content and CaO/SiO2 ratio, which could interpret the disintegration of slag. The present investigation indicates that MnO content has important effects on disintegration and spinel precipitation in stainless steel slag.

Thermodynamic Stability of Spinel Phase at the Interface Between Alumina Refractory and CaO–CaF2–SiO2–Al2O3–MgO–MnO Slags

The interfacial reaction between alumina refractory and CaO–CaF2–SiO2–Al2O3–MgO–MnO slag was observed at 1873 K to estimate the stability of the spinel phase using computational thermodynamics under refining conditions of Mn‐containing steels. The concentration of MnO formed by the slag–steel reaction in the CaO–CaF2–SiO2–Al2O3–MgO melts generally increased by decreasing the CaO/SiO2 ratio of the initial melts. No intermediate compounds were formed at the refractory–slag interface when the initial CaO/SiO2 ratio was 0.5, whereas CaAl12O19 (CA6) and Mg(Mn)Al2O4 (spinel), identified from TEM analysis using EDS mapping and SAED patterns, were observed at the refractory–slag interface when the CaO/SiO2 ratio was 1.0 or greater. The (at.%Mg)/(at.%Mn) ratio in the spinel solution increased by increasing the CaO/SiO2 ratio, which originated from the fact that MgO activity continuously increased as the CaO/SiO2 ratio increased. From thermodynamic analysis considering the equilibrium constant (KSP) and activity quotient (QSP) of the spinel formation reaction at the slag–refractory interface and the bulk slag phase, the precipitation–dissolution behavior of the spinel phase was predicted, which exhibited good consistency with the experimental results. Hence, the dissolutive corrosion mechanism of alumina refractory into the CaO–CaF2–SiO2–Al2O3–MgO–MnO slag was proposed.

Influence of CaF2 on the Viscosity and Structure of Manganese Ferroalloys Smelting Slags

Addition of CaF2 to the CaO-SiO2-MnO (CaO/SiO2 = 0.5) system, which corresponds qualitatively to a silicomanganese ferroalloy smelting slag, affected not only the critical (crystallization) temperature (TCR) but also the viscosity at high temperatures, and its influence on slag properties was strongly dependent on the content of MnO in the slag. The viscosity of CaF2-free 10 mass pct MnO slag was relatively high, i.e., about 10 dPa s at 1773 K (1500 °C), but decreased continuously upon addition of CaF2 to the system. In contrast, the viscosity of the 40 pct MnO system was very low, i.e., 1 dPa s at 1773 K (1500 °C), and CaF2 did not have a large effect. This indicates that Mn2+ is a strong network modifier in manganese ferroalloy smelting slags. Nevertheless, CaF2 addition was very effective at decreasing the viscosity of low MnO slags at low temperatures. The activation energy for the viscous flow of silicate melts decreased linearly in response to CaF2 addition, but this tendency was less pronounced in the more basic composition of the slag. The effect of CaF2 on the viscosity and activation energy for viscous flow of melts was analyzed quantitatively using micro-Raman spectra of quenched glass samples and the silicate polymerization index, i.e., Q3/Q2 ratio. The polymerization index decreased continuously with increasing CaF2 content in less basic (10 pct MnO or C/S = 0.5) slags, whereas it was not affected by CaF2 content in highly basic (40 pct MnO and C/S = 1.0) slags. Bulk thermophysical properties of the CaO-SiO2-MnO-CaF2 slags were quantitatively correlated with the structural information of the slags.

Microscopic Study of Carbon Surfaces Interacting with High Carbon Ferromanganese Slag

The interaction of carbon materials with molten slags occurs in many pyro-metallurgical processes. In the production of high carbon ferromanganese in submerged arc furnace, the carbothermic reduction of MnO-containing silicate slags yields the metal product. In order to study the interaction of carbon with MnO-containing slags, sessile drop wettability technique is employed in this study to reduce MnO from a molten slag drop by carbon substrates. The interfacial area on the carbon substrate before and after reaction with slag is studied by scanning electron microscope. It is indicated that no Mn metal particles are found at the interface through the reduction of the MnO slag. Moreover, the reduction of MnO occurs through the contribution of Boudouard reaction and it causes carbon consumption in particular active sites at the interface, which generate carbon degradation and open pore growth at the interface. It is shown that the slag is fragmented to many micro-droplets at the reaction interface, potentially due to the effect on the interfacial energies of a provisional liquid Mn thin film. The rapid reduction of these slag micro-droplets affects the carbon surface with making deep micro-pores. A mechanism for the formation of slag micro-droplets is proposed, which is based on the formation of provisional micro thin films of liquid Mn at the interface.

P2O5 Solubility Behavior and Resource Utilization of P-Bearing Slag

In order to recycle the phosphorus in P-bearing steelmaking slag and make it used as slag phosphate fertilizer, the citric acid solubility of P-bearing steelmaking slag was researched. The research results show that the citric acid solubility of P-bearing steelmaking slag is decreased with the increasing of P2O5 and Fe2O3 content for the CaO–SiO2–Fe2O3–P2O5 slag system. Added CaF2 into slag can easily form the fluorapatite (Ca5(PO4)2F) that can’t be dissolved in 2% citric acid solution, which makes citric acid solubility of the slag decreased obviously. And added MgO, MnO or Na2O into slag can prevent the precipitation of β-Ca3(PO4)2 phase with low citric acid solubility, which makes the citric acid solubility of slag increased. While for the CaO–SiO2–Fe2O3–P2O5–X (MgO, MnO or Na2O) slag system, MgO and MnO in slag mainly enters into RO phase, which has no effect on the phosphorus existence form in slag and has little influence on citric acid solubility of the slag. The Na2O in slag changes the phosphorus existence form in slag, but the generated Na2Ca4(PO4)2SiO4 and Na3PO4 also have good citric acid solubility, which also has little effect on citric acid solubility. Al2O3 and TiO2 modification only increases the phosphorus content in phosphorus-rich phase, does not change the phosphorus existence form in slag, which makes the citric acid solubility increased slightly. While SiO2 modification prevents the precipitation of β-Ca3(PO4)2 phase with low citric acid solubility, which makes citric acid solubility of the slag increased significantly. The modified slag without fluoride makes the citric acid solubility increased to 95% and meets the requirement of producing slag phosphate fertilizer.

Effect of water vapour content in H2–H2O–CO–CO2 mixtures on MgO solubility in slag under conditions of novel flash ironmaking technology

The effects of different gas atmospheres on the solubility of MgO in CaO–FeO–Al2O3–SiO2–P2O5–MnO slags were studied in the temperature range of 1550–1650°C with wt-%CaO/wt-%SiO2 of 0·8–1·4 and under pO2 = 10−10 to 10−9 atm. The investigated gas atmospheres were H2/H2O (H2 reductant), CO/CO2H2/H2O (natural/coal gas) and CO/CO2. MgO solubility was found to decrease with basicity and FeO content, and increased with temperature. The following correlation was developed for MgO solubility as a function of slag composition and temperature This correlation adequately predicts MgO solubility in slags with FeO contents of 1–50 wt-%, CaO/SiO2 ratios of 0·4–1·6 and temperatures of 1550–1650°C. In addition, MgO solubility was correlated with temperature and basicity defined as: B = (wt-%CaO+0·7 wt-%FetO+0·59 wt-%MnO)–(0·5 wt-%SiO2+0·6 wt-%Al2O3), as follows The MgO solubility at 1550°C and pO2 of 1·6×10−5 atm, which represent typical ironmaking conditions, was 17, 20 and 26 wt-% respectively for slags under CO/CO2H2/H2O, H2/H2O and CO/CO2. Therefore, water vapour would decrease lining wear, as MgO solubility in slag under H2O containing atmospheres is substantially smaller than that under CO/CO2 in typical ironmaking conditions. It was found also that MgO solubility in slag shows a small increase with increasing pH2O beyond ironmaking conditions.For the first time, the effects of water vapour on MgO solubility in slag have been determined.