Alkali leaching was employed to investigate the separation of alumina and silica in roasted kaolin obtained by roasting kaolin alone in air at 1273 K for 60 min and in clinker prepared by roasting the mixed raw meal o...Alkali leaching was employed to investigate the separation of alumina and silica in roasted kaolin obtained by roasting kaolin alone in air at 1273 K for 60 min and in clinker prepared by roasting the mixed raw meal of kaolin,ferric oxide and coal powder with Fe2O3/Al2O3/C molar ratio of 1.2:2.0:1.2 in reducing atmosphere at 1373 K for 60 min.The thermodynamic analyses and alkali leaching results show that the composition of the Al-Si spinel in roasted kaolin is close to that of 3Al2O3·2SiO2 and the spinel is dissolved with increasing leaching time,resulting in difficulty in deeply separating alumina and silica in kaolin by the traditional roasting-leaching process.On the contrary,the efficient separation of alumina and silica in kaolin can be reached by fully converting kaolinite into insoluble hercynite and soluble free silica,namely quartz solid solution and cristobalite solid solution,during reduction roasting,followed by alkali leaching of the obtained clinker.Furthermore,experimental results from treating high-silica diasporic bauxite indicate that the reduction roasting-alkali leaching process is potential to separate silica and alumina in aluminosilicates.展开更多
The removal of iron from an Indian diaspore sample was studied using magnetic separation and leaching techniques aided by an in-depth mineralogical characterization study involving quantitative mineralogical evaluatio...The removal of iron from an Indian diaspore sample was studied using magnetic separation and leaching techniques aided by an in-depth mineralogical characterization study involving quantitative mineralogical evaluation by scanning electron microscope（QEMSCAN）, electron probe micro-analyzer（EPMA） and X-ray diffraction（XRD）. The characterization studies indicate that extremely fine-sized hematite grains are associated with several other mineral phases in a complex manner with around 60% of the hematite not liberated even below the size of 38 μm limiting the scope of physical separation processes to remove the iron. Wet high intensity magnetic separation（WHIMS） studies reveal that only 49% of iron can be removed. Further, leaching studies using oxalic acid suggest that around 76% of the iron can be removed under conditions such as a solid to liquid ratio of 0.05：1, a temperature of 90 ℃ a time period of 120 min and an acid concentration of 1 mol/L. The dissolution of iron in oxalic acid is found to be controlled by chemical reaction and the activation energy is calculated as 35.15 k J/mol.展开更多
Selective flocculation is a new method to solve the problem of China's bauxite de-silication besides flotation and reverse flotation. The method of selective flocculation of bauxite using hydrolyzed polyacrylamide...Selective flocculation is a new method to solve the problem of China's bauxite de-silication besides flotation and reverse flotation. The method of selective flocculation of bauxite using hydrolyzed polyacrylamide as flocculant was experimented and evaluated. The results of diaspore and kaolinite single mineral settling tests show that the difference between settlement yield of kaolinite(settling 15 min) and diaspore(settling 3 min) increases from 16% to 60% by adding flocculant at pH=7. Results of selective flocculation experiment of bauxite show that the higher concentrate grade(65.75) and Al-Si ratio(7.34) could be obtained with sodium carbonate as dispersant compared with sodium hexametaphosphate; under the action of flocculating agent, the concentrate grade and Al-Si ratio increase to 67.99 and 9.01. These results could meet the requirements of Bayer production, and the simpler process was expected to cost far less than traditional flotation method and a promising de-silication method of bauxite.展开更多
Laboratory tests were carried out to study the breakage kinetics of diasporic bauxite and determine its breakage distribution function. Non-first order breakage with different deceleration rates for different size int...Laboratory tests were carried out to study the breakage kinetics of diasporic bauxite and determine its breakage distribution function. Non-first order breakage with different deceleration rates for different size intervals is found, which is most probably caused by the heterogeneity of the ore. Piecewise linearization method is proposed to describe the non-first order breakage according to its characteristics. In the method, grinding time is divided into several intervals and breakage is assumed to be first order in each interval. So, the breakage rates are calculated by taking the product of the last interval as feed and then established as a function of particle size and grinding time. Based on the predetermined breakage rate function, the breakage distribution of the ore is back-calculated from the experimental data using the population balance model (PBM). Finally, the obtained breakage parameters are validated and the simulated data are in good agreement with the experimental data. The obtained breakage distribution and the method for breakage rate description are both significant for modeling the full scale ball milling process of bauxite.展开更多
基金Project(51604309) supported by the National Natural Science Foundation of China
文摘Alkali leaching was employed to investigate the separation of alumina and silica in roasted kaolin obtained by roasting kaolin alone in air at 1273 K for 60 min and in clinker prepared by roasting the mixed raw meal of kaolin,ferric oxide and coal powder with Fe2O3/Al2O3/C molar ratio of 1.2:2.0:1.2 in reducing atmosphere at 1373 K for 60 min.The thermodynamic analyses and alkali leaching results show that the composition of the Al-Si spinel in roasted kaolin is close to that of 3Al2O3·2SiO2 and the spinel is dissolved with increasing leaching time,resulting in difficulty in deeply separating alumina and silica in kaolin by the traditional roasting-leaching process.On the contrary,the efficient separation of alumina and silica in kaolin can be reached by fully converting kaolinite into insoluble hercynite and soluble free silica,namely quartz solid solution and cristobalite solid solution,during reduction roasting,followed by alkali leaching of the obtained clinker.Furthermore,experimental results from treating high-silica diasporic bauxite indicate that the reduction roasting-alkali leaching process is potential to separate silica and alumina in aluminosilicates.
文摘The removal of iron from an Indian diaspore sample was studied using magnetic separation and leaching techniques aided by an in-depth mineralogical characterization study involving quantitative mineralogical evaluation by scanning electron microscope（QEMSCAN）, electron probe micro-analyzer（EPMA） and X-ray diffraction（XRD）. The characterization studies indicate that extremely fine-sized hematite grains are associated with several other mineral phases in a complex manner with around 60% of the hematite not liberated even below the size of 38 μm limiting the scope of physical separation processes to remove the iron. Wet high intensity magnetic separation（WHIMS） studies reveal that only 49% of iron can be removed. Further, leaching studies using oxalic acid suggest that around 76% of the iron can be removed under conditions such as a solid to liquid ratio of 0.05：1, a temperature of 90 ℃ a time period of 120 min and an acid concentration of 1 mol/L. The dissolution of iron in oxalic acid is found to be controlled by chemical reaction and the activation energy is calculated as 35.15 k J/mol.
基金Project(2005CB623701)supported by the National Key Basic Research Program(973)of China
文摘Selective flocculation is a new method to solve the problem of China's bauxite de-silication besides flotation and reverse flotation. The method of selective flocculation of bauxite using hydrolyzed polyacrylamide as flocculant was experimented and evaluated. The results of diaspore and kaolinite single mineral settling tests show that the difference between settlement yield of kaolinite(settling 15 min) and diaspore(settling 3 min) increases from 16% to 60% by adding flocculant at pH=7. Results of selective flocculation experiment of bauxite show that the higher concentrate grade(65.75) and Al-Si ratio(7.34) could be obtained with sodium carbonate as dispersant compared with sodium hexametaphosphate; under the action of flocculating agent, the concentrate grade and Al-Si ratio increase to 67.99 and 9.01. These results could meet the requirements of Bayer production, and the simpler process was expected to cost far less than traditional flotation method and a promising de-silication method of bauxite.
基金Supported by the Fundamental Research Funds for the Central Universities (2012QNZT069)the Postdoctoral Science Foundation of China (2012M521413)+1 种基金the National Science Fund for Distinguished Young Scholars of China (61025015)the National Natural Science Foundation of China (61273187, 61273159)
文摘Laboratory tests were carried out to study the breakage kinetics of diasporic bauxite and determine its breakage distribution function. Non-first order breakage with different deceleration rates for different size intervals is found, which is most probably caused by the heterogeneity of the ore. Piecewise linearization method is proposed to describe the non-first order breakage according to its characteristics. In the method, grinding time is divided into several intervals and breakage is assumed to be first order in each interval. So, the breakage rates are calculated by taking the product of the last interval as feed and then established as a function of particle size and grinding time. Based on the predetermined breakage rate function, the breakage distribution of the ore is back-calculated from the experimental data using the population balance model (PBM). Finally, the obtained breakage parameters are validated and the simulated data are in good agreement with the experimental data. The obtained breakage distribution and the method for breakage rate description are both significant for modeling the full scale ball milling process of bauxite.
