Browsing by Author "Xia, Longgong"
Now showing 1 - 4 of 4
- Results Per Page
- Sort Options
- Experimental Determination of Phase Equilibria in the REM2O3-SiO2 (REM = Y/Yb/La) Systems at Elevated Temperature
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2021-01) Xia, Longgong; Sukhomlinov, Dmitry; Ye, Fengchun; Liu, Zhihong; Taskinen, PekkaPhase relations in the REM2O3-SiO2 (REM = Y/Yb/La) systems have been studied using the equilibration/quenching/scanning electron microscopy (SEM)-electron probe microanalysis (EPMA) technique. The solvus and liquidus between 1400°C and 1650°C have been determined. The results obtained in this study show that a maximum of 0.57 wt.% Yb2O3 can dissolve in SiO2 phase, while the maximum solubility of La2O3 and Y2O3 in SiO2 phase was 0.22 wt.% and 0.07 wt.%, respectively. Correspondingly, SiO2 shows low solubility in La2Si2O7, and nearly does not dissolve in Y2Si2O7 or Yb2Si2O7. No liquid phase was detected in the Y2O3-SiO2 or Yb2O3-SiO2 system in the temperature range of interest. One oxide liquid phase comprising 39.27 wt.% SiO2 and 59.07 wt.% La2O3 was found in the La2O3-SiO2 system sample equilibrated at 1653°C, revealing that the eutectic point temperature between La2Si2O7 and SiO2 is located between 1600°C and 1653°C. Results of this study were compared with previous observations, revealing significant differences. - Experimental Determination of the Phase Equilibrium in the Cu-O-ZnO-SiO2-CaO-MgO System
School of Chemical Technology | Doctoral dissertation (article-based)(2016) Xia, LonggongDue to the intensive consumption of high quality concentrates, copper smelters are increasing portions of multi-mineral ores and secondary scraps in their feeding materials. The smelting of complex materials is always accompanied by the formation of large amount of slag. Impurities in the feeding materials will be oxidized during the smelting process, and those oxides will form the slag phase together with fluxes. Certain amount of refractory materials will be eroded by molten phases, and then merge into the slag phase. The monitoring of slag compositions and properties has significant importance. Zinc is one of the major impurity elements in copper making, and it will be oxidized to zinc oxide (ZnO) in the smelting process. Zinc content in copper scraps, for example WEEE materials and waste brass, is also quite high, and it will also be oxidized and merge into the slag phase. Currently, ZnO content in copper smelting slags is increasing. However, the thermodynamic information about high ZnO content slag is still incomplete. The thermodynamic properties of the slag can be achieved by software calculation. But there are a lot of uncertainties in applying those extrapolated information into practice. Accurate experimental data are needed in the thermodynamic assessment of those less known systems.With the guidance of calculated phase diagrams by MTDATA 5.10 and its Mtox 8.1 database, the equilibration/quenching/SEM/EDS+EPMA technique has been successfully applied in investigating the phase relationship in the Cu-O-ZnO-SiO2-CaO-MgO system and its subsystems. Phase relationships in a wide temperature range (1000 °C – 1700 °C), and at various oxygen partial pressures (pO2 = 0.21 atm, pO2 = 0.01 atm, and in pure argon) have been systematically studied. Liquidus compositions and eutectic points in the ZnO-SiO2, ZnO-CaO, Cu-O-ZnO, Cu-O-SiO2, Cu-O-ZnO-SiO2, Cu-O-ZnO-CaO, and Cu-O-ZnO-MgO systems have been investigated. Sub-solidus lines in the ZnO-CaO, ZnO-MgO binaries have also been determined. The solubility behavior of copper oxide in the other terminal phases have been carefully checked as well. The best fitted phase diagrams have been compared with the resultsfrom the literature, and with the calculated phase diagrams from MTDATA 5.10 software and Mtox 8.1 database, and the differences are significant. The thermodynamic descriptions of those systems in the database should be updated, and the Cu-O-ZnO-SiO2-CaO-MgO system and its sub-systems need re-assessments. This study provides novel data for both scientific research and industrial practices. - Reaction Behavior of Na2SO4-Containing Copper Matte Powders in a Simulated Flash Converting Process
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2021-10) Yu, Feng; Xia, Longgong; Zhu, Yinbin; Jokilaakso, Ari; Liu, ZhihongSodium sulfate accumulation in the water system is a common problem in the production of primary metals from sulfide minerals. In flash smelting-flash converting copper smelters, when molten copper matte quenched in industrial water to produce matte granules, Na2SO4 precipitated and entered the system, which had negative influence on the matte converting process. The reaction behaviors of copper matte powder containing Na2SO4 have been studied through thermodynamic calculation and single-particle experiments. Calculated results showed that a liquid sulfate phase, Na2S containing copper matte, and Cu-Na alloy may form in the processing conditions of the converting process. The influence of the Na2SO4 dosage, fluxing conditions, and processing temperature has been systematically studied, and the results obtained showed that: (1); Na2SO4 physically precipitated on matte particles, and the Cu-Na alloy phase was found within copper phase in reacted particles; (2); Na2SO4 contamination hindered oxygen transfer by forming a low melting sulfate phase, and the de-sulfuration rate of matte powder changed dramatically along with the variation in Na2SO4 amount; (3); CaO flux was able to promote the converting reactions and Na2SO4 transformation; (4); Na2SO4 melt and formed a sulphate layer on matte particles at 1000 degrees C, Cu-Na alloy phase was found in samples collected at 1200 degrees C, and Cu-Na-O phase was detected in blister copper at 1600 degrees C. - A Study of Selenium and Tellurium Distribution Behavior, Taking the Copper Matte Flash Converting Process as the Background
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2021-02) Yu, Feng; Liu, Zhihong; Ye, Fengchun; Xia, Longgong; Jokilaakso, AriSingle particle experiments were carried out in the present study. An industrial copper matte powder, containing 68.04 wt.% Cu, 0.50 wt.% Se and 0.08 wt.% Te was taken as the starting material. Se and Te phase assemblies and distribution behaviors were systematically investigated in the air atmosphere. It was found that Se reported to blister copper, matte, and oxide phase, whilst Te will enrich in oxide phases, including phases in the Fe-Si-Te-O, Ca-Fe-Te-O, and Ca-Te-O-(S) systems. As the temperature increases, the selenium and tellurium content in the copper and matte phases decreases. The introduction of CaO flux, and typical impurities of Pb and Si, had significant influence on Se and Te distribution. The results revealed that CaO addition and Si impurity accelerated the removal of Se and Te from the copper and matte phases, but Pb impurity increased Se and Te in Cu-rich phases.