Particulate flow modelling in a spiral separator by using the Eulerian multi-fluid VOF approach

The Euler-Euler model is less effective in capturing the free surface of flow film in the spiral separator,and thus a Eulerian multi-fluid volume of fluid(VOF)model was first proposed to describe the particulate flow in spiral separators.In order to improve the applicability of the model in the high solid concentration system,the Bagnold effect was incorporated into the modelling framework.The capability of the proposed model in terms of predicting the flow film shape in a LD9 spiral separator was evaluated via comparison with measured flow film thicknesses reported in literature.Results showed that sharp air–water and air-pulp interfaces can be obtained using the proposed model,and the shapes of the predicted flow films before and after particle addition were reasonably consistent with the observations reported in literature.Furthermore,the experimental and numerical simulation of the separation of quartz and hematite were performed in a laboratory-scale spiral separator.When the Bagnold lift force model was considered,predictions of the grade of iron and solid concentration by mass for different trough lengths were more consistent with experimental data.In the initial development stage,the quartz particles at the bottom of the flow layer were more possible to be lifted due to the Bagnold force.Thus,a better predicted vertical stratification between quartz and hematite particles was obtained,which provided favorable conditions for subsequent radial segregation.

Novel polyhydroxy cationic collector N-(2,3-propanediol)-Ndodecylamine: Synthesis and flotation performance to hematite and quartz

To enhance the performance of traditional cationic collector,a novel polyhydroxy amine collector N-(2,3-Propanediol)-N-dodecylamine(PDDA)was designed by introducing one propylene glycol group into dodecylamine(DDA).It was prepared by a nucleophilic substitution reaction,which showed better solubility and hydrophobicity than DDA and was firstly employed as the collector for the separation of hematite and quartz.Flotation tests showed that PDDA had an excellent flotation performance and significantly better selectivity than DDA.In addition,the flotation performance and adsorption mechanism of PDDA on hematite and quartz surfaces were studied using Fourier transform infrared spectroscopy(FTIR),zeta potential and X-ray photoelectron spectroscopy(XPS)tests.These results demonstrated that the interaction between PDDA and the minerals’surfaces was mainly electrostatic adsorption and hydrogen bond,while PDDA tended to adsorb on the surfaces of quartz more than that of hematite.Performance optimization of amine collectors by introducing hydroxyl was also verified,which was of great meaning to the design,development,and application of the polyhydroxy cationic collector.In conclusion,PDDA could be used as a potential collector in the flotation separation of quartz and hematite.

Enhanced detection of ppb-level NO_(2)by uniform Pt-doped ZnSnO_(3)nanocubes

ZnSnO_(3) nanocubes(ZSNCs)with various Pt concentrations(i.e.,1 at%,2 at%,and 5 at%)were synthesized by a simple one-pot hydrothermal method.The microstructures of pure and Pt-doped ZSNCs were characterized by X-ray diffractometry,scanning electron microscopy,transmission electron microscopy,energy-dispersive X-ray spectroscopy,and X-ray photoelectron spectroscopy.Results showed that the pure ZSNCs have a perovskite structure with a side length of approximately 600 nm;this length was reduced to 400 nm after Pt doping.Following doping,PtO_(x)(PtO and PtO_(2)) nanoparticles with a diameter of approximately 5 nm were uniformly coated on the surface of the ZSNCs.Systematic investigation of the gas-sensing abilities of the nanocubes showed that the Pt-doped ZSNCs have excellent sensing properties toward nitrogen dioxide(NO_(2)) gas in the operating temperature range of 75-175℃.Among the sensors prepared,that based on 1 at%Pt-doped ZSNCs exhibited the best response of 16.0 toward 500 ppb NO_(2) at 125℃;this response is over 11 times higher compared with that of pure ZSNCs.The enhanced NO_(2) sensing mechanism of the Pt-doped ZSNCs may be attributed to the synergistic effects of catalytic activity and chemical sensitization by Pt doping.

Synthesis and in-situ noble metal modification of WO3·0.33H2O nanorods from a tungsten-containing mineral for enhancing NH3 sensing performance

Ag-and Pt-doped WO3-0.33 H2O nanorods with high response and selectivity to NH3 were synthesized from a tungsten-containing mine ral of scheelite concentrate by a simple combined process,namely by a high pressure leaching method to obtain tungstate ions-containing leaching solution and followed by a hydrothermal method to prepare corresponding nanorods.The microstructure and NH3 sensing perfo rmance of the final products were investigated systematically.The microstructure characte rization showed that the as-prepared WO3-0.33 H2 O nanorods had a hexagonal crystal structure,and Ag and Pt nanoparticles were uniformly distributed in the WO3-0.33 H2O nano rods.Gas sensing measurements indicated that Ag and Pt nanopa rticles not only could obviously enhance NH3 sensing properties in terms of response,selectivity as well as response/recovery time,but also could reduce the optimal operating temperature at which the highest response was achieved.The highest responses of 22.4 and 47.6 for Agand Pt-doped WO3-0.33 H2O nanorods to 1000 ppm NH3 were obtained at 225 and 175℃,respectively,which were about four and eight folds higher than that of pure one at 250℃.The superior NH3 sensing properties are mainly ascribed to the catalytic activities of noble metals and the different work functions between noble metals and WO3-0.33 H2 O.

In-situ growth of V2O5 flower-like structures on ceramic tubes and their trimethylamine sensing properties

V2O5 flower-like structures assembled by thin nanosheets were in-situ growth on ceramic tubes by hydrothermal process.The structural characterization indicates that V2O5 flower-like structures is orthogonal diamond phase,which entirely covered on the surface of ceramic tubes.TMA sensing measured results revealed that the sensor based on V2O5 flower-like structures exhibited fast reversible and response,good selectivity to TMA and good stability at 200℃.The good sensing performance may be ascribed to flower-like structure s and directly growth sensing film on the ceramic tube without structure damage.Our works give a simple in-situ growth flower-like structures route on sensing device,which exhibits potential application for detecting trace amounts of TMA gas.