The Recovery of Metallic Tin from an Industrial Tin-Bearing By-Product Containing Na2SO4 by Reduction Smelting Process

Tin was recovered in metal from an industrial tin-bearing byproduct containing Na2SO4 by carbothermic reduction smelting, and the effects of basicity (Na2O/SiO2), temperature, and reaction time on the recovery of tin were studied. Na2SO4 was reduced by carbon and formed into sodium silicate slag (Na2O–SiO2) in the presence of SiO2. Tin content in slag decreased with the increase of Na2O/SiO2 ratio in slag, temperature, and reaction time, but the recovery of tin was affected by volatilization of tin in high temperature and high silica region of basicity. In this study, the maximum recovery rate of tin was 94.8% at the experimental condition of 1200 °C, 2 h, and 0.55 of Na2O/SiO2 ratio. The major impurities in produced metal were Bi, Pb, Cu, Fe, and most of Bi, Pb, Cu were distributed to the metal phase, but the distribution of Fe was closely related to basicity.

Effect of Basicity and Al2O3 on Viscosity of Blast Furnace Slag and Thermodynamic Analysis

With the increased use of laterite nickel ore, the impact of high Al2O3 slag on blast furnace smelting has gradually increased. In this paper, the effects of slag basicity and Al2O3 content on slag viscosity and enthalpy change under constant temperature conditions was investigated. The changes in slag structure were analyzed by activation energy and Fourier Transform Infrared (FT-IR) spectroscopy. The relationship between slag components and slag temperature and viscosity when slag heat is reduced was investigated. The results showed that the viscosity first slightly decreased and then significantly increased with increasing basicity at constant temperature. With the addition of Al2O3 content, the viscosity of the slag increases. The activation energy increases with increasing slag basicity and Al2O3. With increasing basicity, the [SiO4]4- tetrahedral unit trough depth becomes shallow, the [AlO4]5- asymmetric stretching band migrates to lower wave numbers, and the slag structure depolymerizes. With the increase of Al2O3 content, the trough of [SiO4]4- tetrahedra deepens and the center of the symmetric stretching band moves to a higher wave number. The [AlO4]5- asymmetric stretching band becomes obvious, indicating the complexity of the slag structure. When the heat decreases, the slag temperature increases as the basicity increases, and the slag thermal stability is better at the basicity of 0.95-1.05. As the Al2O3 content increases, the thermal stability of the slag becomes worse.

Thermodynamic Properties, Viscosity, and Structure of CaO–SiO2–MgO–Al2O3–TiO2–Based Slag

The effect of TiO2 and the MgO/Al2O3 ratio on the viscosity, heat capacity, and enthalpy change of CaO–SiO2–Al2O3–MgO–TiO2 slag at constant heat input was studied. The variation of slag structure was analyzed by the calculation of activation energy and FTIR spectrum measurements. The results showed that the heat capacity and enthalpy change of the slag decreased with the increase of TiO2 content. Under constant heat supply, the fluctuations in slag temperature were relatively apparent, and the temperature of slag increased as the TiO2 content increased. The viscosity of slag decreased due to the increase in slag temperature. Increasing the MgO/Al2O3 ratio could decrease the temperature and viscosity of slag. The effect of increasing the MgO/Al2O3 ratio on the viscosity was more pronounced than the decreasing temperature caused by increasing the MgO/Al2O3 ratio. The apparent activation energy decreased with increasing TiO2 content and MgO/Al2O3 ratio. The Ti–O bonds formed with TiO2 addition, and the Ti–O bonds were weaker than Si–O bonds, which resulted in the decrease in heat capacity and viscosity of slag.

Influence of Basicity and MgO on Fluidity and Desulfurization Ability of High Aluminum Slag

The viscosity of experimental slag, which was mixed based on the composition of a practical blast furnace slag, was measured in this paper. The influence of Al2O3 and MgO content, basicity R2 = w(CaO)/w(SiO2) on the fluidity of slag was studied. The stepwise regression analysis in SPSS was used to reveal the relationship between sulfur distribution coefficient LS and slag composition as well as furnace temperature. The results show that increasing of MgO up to 12% can decrease the slag viscosity. The w(MgO) should be controlled below 8% when there is 20% Al2O3 in the slag. Temperature of hot metal and content of CaO in slag are the two dominant factors on the desulfurization capacity of slag.

Study on Extraction of Mesophase from Steel Slag by Potassium Hydroxide-Sucrose (KOSH) Solution Method

The mesophase (iron aluminate, etc.) in steel slag was extracted by potassium hydroxide-sucrose (KOSH) solution method. The effects of partical size of steel slag, temperature and time of extraction on dissolution of mesophase phase were studied. The composition and morphology of the residue were analyzed by XRD and SEM. The results show the mesophase in steel slag powders (the weight was and the fineness was) could be fully dissolved when 4.00 g sample with a fineness about 600m2/kg is used and extraction temperature is kept at 90oC, however, other minerals in the steel slag could be hardly dissolved. The reason might be for that, in alkaline environment which provided by potassium hydroxide, the replacement of ions were took place between the mesophase in steel slag and the organic ligands formed by sugar and potassium hydroxide, and through the adsorption and polarization between ligand and steel slag surface, it will result in the decrease of activation energy of iron aluminate.

Numerical Simulation of Molten-Slag Flow in Coal Gasifier

In this paper, numerical simulations of the heat transfer in molten-slag flow with free surface and phase change (solidification) is carried out, and we propose a new evaluation method for discharging performance of the molten-slag from coal gasifier. A stable operation of the coal gasifier requires that the molten-slag should be discharged from the slag-hole continuously. In the maintenance of discharging a molten slag, it is necessary to keep the molten-slag temperature higher than an ash fluid temperature, and to hold the fluidity of the molten-slag. From the viewpoint of gasification performance, if the air ratio is set low in order to raise the cold gas efficiency, the molten-slag is not able to get enough heat for its discharge, because of the lowering of gas temperature in the coal gasifier. To strike a balance between the maintenance of continuity on the molten-slag discharge and the improvement in gasification performance, it is important to develop a prediction and evaluation method for discharge performance of the molten-slag from coal gasifier.