The global nickel sulphide resources are becoming more difficult to mine and, as a result, there is increasing interest in the current and future development of the oxidic nickel laterite deposits. In comparison to th...The global nickel sulphide resources are becoming more difficult to mine and, as a result, there is increasing interest in the current and future development of the oxidic nickel laterite deposits. In comparison to the sulphide ores, the nickel laterites cannot be readily upgraded by conventional means and growing attention is being focused on the development of new methods for processing these ores. In this paper, firstly, brief overviews of laterite ore mineralogy and the conventional techniques used to extract the nickel from both the limonitic and the saprolitic nickeliferous laterites are provided. Secondly, previous research on the thermodynamic modelling of the reduction of the laterites is discussed. Thirdly, an improved thermodynamic model is used to predict the equilibrium products arising from the solid state reduction of both the limonitic and the saprolitic ores. Based on these thermodynamic predictions, the reduction behaviors of the two ore types are compared in terms of nickel recovery and grade in the ferronickel product. The effects of reduction temperature, ore composition and carbon additions were studied. Finally, the results from the simulations are compared to the experimental data available in the literature.展开更多
Numerous examples of long term landscape are presented relating soil and regolith tolandforms going back to Cenozoic or Mesozoic times. Many conventional approaches to soil areinappropriate for such materials. It is i...Numerous examples of long term landscape are presented relating soil and regolith tolandforms going back to Cenozoic or Mesozoic times. Many conventional approaches to soil areinappropriate for such materials. It is important to study the entire regolith, and realise it seldomreveals all the changes of climate ithas experienced.展开更多
Landscape distribution, macroscopic, microscopic, mineral and geochemical characterizations were conducted on the Doumbouo-Fokoué bauxite ore deposit in order to estimate bauxites potential and its implication to...Landscape distribution, macroscopic, microscopic, mineral and geochemical characterizations were conducted on the Doumbouo-Fokoué bauxite ore deposit in order to estimate bauxites potential and its implication to general lowering of the relief. Fourteen bauxitic plateaus covering a surface area of 5.7 km2 were identified. Bauxitic pedons show deep weathered profiles (10.0 - 12.0 m) with thick bauxitic mantle (4.0 - 8.0 m). Saprolite and pisolith bauxitic facies own high aluminium (47.5% - 49.5% Al2O3), relatively low iron (20.0% - 22.0% Fe2O3) and low silica contents (1.8% - 7.6% SiO2). Gibbsite is the dominant mineral (49% - 68% of minerals detected by X-ray);meanwhile hematite, goethite and kaolinite occur in small amounts. Bauxitization corresponds to intense allitization with abundant accumulation of gibbsite and development of lateritic iron bearing ortho-bauxites. Bauxite ores yielded bauxite reserves of 9.2 million tons. They occur as old and residual bauxitic mantles representing remnants of the Miocene residual lateritic deposits in West Cameroon referring to the African surface of Valeton [1]. Its mean altitude (1532 - 1590 m als) below the African surface reveals general lowering of the relief.展开更多
In order to explain the formation process of slope hazards, and to identify the key factors leading to instability of a slope, Emeishan basalt saprolite in vadose zones of the Touzhai landslide in Zhaotong, Yunnan, wa...In order to explain the formation process of slope hazards, and to identify the key factors leading to instability of a slope, Emeishan basalt saprolite in vadose zones of the Touzhai landslide in Zhaotong, Yunnan, was studied. The formation and evolution of Emeishan basalt saprolite was examined using, amongst other techniques, field investigations,thin section analysis, scanning electron microscopy(SEM) observations, chemical analysis, physical and water-physical property tests of rock masses. Field observations revealed that the majority of the weathered rock blocks were presented as a concentric layer structure in which an internal corestone was enveloped with several layers of external saprolized crust. Chemical and mineralogical analysis identified that iron was the most sensitive element and that the weathering progress usually started with the oxidation of Fe2+ to Fe3+ in rock blocks. Alkaline elements such as Si, Ca, Mg, Na and K were also dissolved and Fe and Al were concentrated in saprolized crusts. Results indicated that loss on ignition(LOI) also increased significantly. SEM results showed that the weathering intensity of thebasalt blocks decreased gradually from the outside to the inside, and the mineral morphology significantly differed on both sides of the weathering front. The saprolized crusts presented cellular microstructure features due to the generation of micropore and clay minerals. Thin section analysis showed that plagioclase was relatively more stable than pyroxene and chlorite during weathering. With a centripetal propagation of the weathering front, saprolized crusts became thicker and corestones became smaller; fresh Emeishan basalt blocks gradually turned into saprolized blocks. Due to the loose structure and low strength of saprolite, the quality of the Emeishan basalt mass significantly deteriorated, this being a potentially important factor which caused the Touzhai landslide to occur.展开更多
对一砂质泥岩风化土在300,400,500 k Pa及600 k Pa固结围压下,分别进行了原状土样与重塑土样的动三轴试验,得到了该砂质泥岩风化土的阻尼比曲线。试验结果表明,原状土与重塑土在各固结围压试验下,阻尼比随归一化剪应变γ取值的增大而增...对一砂质泥岩风化土在300,400,500 k Pa及600 k Pa固结围压下,分别进行了原状土样与重塑土样的动三轴试验,得到了该砂质泥岩风化土的阻尼比曲线。试验结果表明,原状土与重塑土在各固结围压试验下,阻尼比随归一化剪应变γ取值的增大而增大,且在γ取值相同时,原状土阻尼比值大于相应重塑土;原状土与重塑土试样的λd~γ关系曲线均随固结围压的升高而逐渐降低,且降低幅度随着γ值的增大而减小,并在γ值接近于1时各关系曲线基本交叉重合;在同等试验条件下,通过经验公式与绘图两种方式求得的最大阻尼比值相差很小,但随着固结围压的增大,两种方式求得的最大阻尼比值相差变大。展开更多
文摘The global nickel sulphide resources are becoming more difficult to mine and, as a result, there is increasing interest in the current and future development of the oxidic nickel laterite deposits. In comparison to the sulphide ores, the nickel laterites cannot be readily upgraded by conventional means and growing attention is being focused on the development of new methods for processing these ores. In this paper, firstly, brief overviews of laterite ore mineralogy and the conventional techniques used to extract the nickel from both the limonitic and the saprolitic nickeliferous laterites are provided. Secondly, previous research on the thermodynamic modelling of the reduction of the laterites is discussed. Thirdly, an improved thermodynamic model is used to predict the equilibrium products arising from the solid state reduction of both the limonitic and the saprolitic ores. Based on these thermodynamic predictions, the reduction behaviors of the two ore types are compared in terms of nickel recovery and grade in the ferronickel product. The effects of reduction temperature, ore composition and carbon additions were studied. Finally, the results from the simulations are compared to the experimental data available in the literature.
文摘Numerous examples of long term landscape are presented relating soil and regolith tolandforms going back to Cenozoic or Mesozoic times. Many conventional approaches to soil areinappropriate for such materials. It is important to study the entire regolith, and realise it seldomreveals all the changes of climate ithas experienced.
文摘Landscape distribution, macroscopic, microscopic, mineral and geochemical characterizations were conducted on the Doumbouo-Fokoué bauxite ore deposit in order to estimate bauxites potential and its implication to general lowering of the relief. Fourteen bauxitic plateaus covering a surface area of 5.7 km2 were identified. Bauxitic pedons show deep weathered profiles (10.0 - 12.0 m) with thick bauxitic mantle (4.0 - 8.0 m). Saprolite and pisolith bauxitic facies own high aluminium (47.5% - 49.5% Al2O3), relatively low iron (20.0% - 22.0% Fe2O3) and low silica contents (1.8% - 7.6% SiO2). Gibbsite is the dominant mineral (49% - 68% of minerals detected by X-ray);meanwhile hematite, goethite and kaolinite occur in small amounts. Bauxitization corresponds to intense allitization with abundant accumulation of gibbsite and development of lateritic iron bearing ortho-bauxites. Bauxite ores yielded bauxite reserves of 9.2 million tons. They occur as old and residual bauxitic mantles representing remnants of the Miocene residual lateritic deposits in West Cameroon referring to the African surface of Valeton [1]. Its mean altitude (1532 - 1590 m als) below the African surface reveals general lowering of the relief.
基金funded by the Joint Funds of the Natural Science Foundation of China with the Natural Science Foundation of Yunnan (Grant No. U1502232,U1033601)the Research Fund for the Doctoral Program of Higher Education of China(Grant No. 20135314110005)
文摘In order to explain the formation process of slope hazards, and to identify the key factors leading to instability of a slope, Emeishan basalt saprolite in vadose zones of the Touzhai landslide in Zhaotong, Yunnan, was studied. The formation and evolution of Emeishan basalt saprolite was examined using, amongst other techniques, field investigations,thin section analysis, scanning electron microscopy(SEM) observations, chemical analysis, physical and water-physical property tests of rock masses. Field observations revealed that the majority of the weathered rock blocks were presented as a concentric layer structure in which an internal corestone was enveloped with several layers of external saprolized crust. Chemical and mineralogical analysis identified that iron was the most sensitive element and that the weathering progress usually started with the oxidation of Fe2+ to Fe3+ in rock blocks. Alkaline elements such as Si, Ca, Mg, Na and K were also dissolved and Fe and Al were concentrated in saprolized crusts. Results indicated that loss on ignition(LOI) also increased significantly. SEM results showed that the weathering intensity of thebasalt blocks decreased gradually from the outside to the inside, and the mineral morphology significantly differed on both sides of the weathering front. The saprolized crusts presented cellular microstructure features due to the generation of micropore and clay minerals. Thin section analysis showed that plagioclase was relatively more stable than pyroxene and chlorite during weathering. With a centripetal propagation of the weathering front, saprolized crusts became thicker and corestones became smaller; fresh Emeishan basalt blocks gradually turned into saprolized blocks. Due to the loose structure and low strength of saprolite, the quality of the Emeishan basalt mass significantly deteriorated, this being a potentially important factor which caused the Touzhai landslide to occur.
文摘对一砂质泥岩风化土在300,400,500 k Pa及600 k Pa固结围压下,分别进行了原状土样与重塑土样的动三轴试验,得到了该砂质泥岩风化土的阻尼比曲线。试验结果表明,原状土与重塑土在各固结围压试验下,阻尼比随归一化剪应变γ取值的增大而增大,且在γ取值相同时,原状土阻尼比值大于相应重塑土;原状土与重塑土试样的λd~γ关系曲线均随固结围压的升高而逐渐降低,且降低幅度随着γ值的增大而减小,并在γ值接近于1时各关系曲线基本交叉重合;在同等试验条件下,通过经验公式与绘图两种方式求得的最大阻尼比值相差很小,但随着固结围压的增大,两种方式求得的最大阻尼比值相差变大。
