Mesoscale drag model is of crucial significance for the reliability and accuracy in coarse-grid EulerianEulerian two-fluid model(TFM)simulations of gas-solid flow hydrodynamics in fluidized bed reactors.Although numer...Mesoscale drag model is of crucial significance for the reliability and accuracy in coarse-grid EulerianEulerian two-fluid model(TFM)simulations of gas-solid flow hydrodynamics in fluidized bed reactors.Although numerous mesoscale drag models have been reported in the literature,a systematic comparison of their prediction capability from the perspective of heterogeneity analysis is still lacking.In this study,in order to investigate the effect of several typical drag models on the hydrodynamic behaviors,the nonuniformity analysis and the sensitivity to material properties,extensive coarse-grid TFM simulations of a bubbling pilot-scale fluidized bed reactor are carried out.The results demonstrate that the mesoscale drag models outperform the empirical drag model in terms of nonuniformity due to the consideration of the influence of the mesoscale structures on the drag force in the bubbling region.Furthermore,the results reveal that our previously developed three-marker gradient-based drag model considering the solid concentration gradient exhibits satisfactory performance in predicting the bubbling flow hydrodynamics.Besides,the material-property-dependent drag model considering the explicit effect of material properties on drag corrections is most sensitive to the particle diameter.This work provides guideline for possible future improvements of mesoscale models to simulate gas-solid flow more accurately and universally.展开更多
The chemical looping concept provided a novel way to achieve carbon separation during the production of energy or substances. In this work, hydrogen generation with inherent CO2 capture in single packed bed reactor vi...The chemical looping concept provided a novel way to achieve carbon separation during the production of energy or substances. In this work, hydrogen generation with inherent CO2 capture in single packed bed reactor via this concept was discussed. Two oxygen carriers, Fe203 60 wt.% and Fe2O3 55 wt.%/CuO 5 wt.% supported by Al2O3, were made by ball milling method. First, according to the characteristics of the reduction breakthrough curve, a strict fuel supply strategy was selected to achieve simultaneous CO2 capture and HE production. Then, in the long term tests using CO as fuel, it was proved that CuO addition improved hydrogen generation with the maximum intensity of 3700 μmol H2·g^-1 Fe2O3 compared with Fe-Al of 2300 μmol HE.g^-1 Fe2O3. The overall CO2 capture efficiency remained 98%- 98.8% over 100 cycles. Moreover, the reactivity of deactivated materials was recovered nearly like that of fresh ones by sintering treatment. Finally, two kinds of complex gases consist of CO, HE, CH4 and CO2 were utilized as fuels to test the feasibility. The results showed all components could be completely converted by Fe-Cu- Al in the reduction stage. The intensity of hydrogen production and the overall CO2 capture efficiency were in the range of 2000-2400 μnol H2^g^-1 Fe2O3 and 89%, 95%, respectively.展开更多
This work describes the environmentally friendly technology for oxidation of ammonia （NH3） to form nitrogen at temperatures range from 423K to 673K by selective catalytic oxidation （SCO） over a nanosized Pt- Rh/γ...This work describes the environmentally friendly technology for oxidation of ammonia （NH3） to form nitrogen at temperatures range from 423K to 673K by selective catalytic oxidation （SCO） over a nanosized Pt- Rh/γ-A12O3 catalyst prepared by the incipient wetness impregnation method of hexachloroplatinic acid （H2PtC16） and rhodium （Ⅲ） nitrate （Rh（NO3）3） with γ-A12O3 in a tubular fixed-bed flow quartz reactor （TFBR）. The characterization of catalysts were thoroughly measured using transmission electron microscopy （TEM）, three- dimensional excitation-emission fluorescent matrix （EEFM） spectroscopy, UV-Vis absorption, dynamic light- scattering （DLS）, zeta potential meter, and cyclic voltam- metry （CV）. The results demonstrated that at a temperature of 673K and an oxygen content of4%, approximately 99% of the NH3 was removed by catalytic oxidation over the nanosized Pt-Rh/γ-A12O3 catalyst. N2 was the main product in NH3-SCO process. Further, it reveals that the oxidation of NH3 was proceeds by the over-oxidation of NH3 into NO, which was conversely reacted with the NH3 to yield N2. Therefore, the application ofnanosized Pt-Rh/γ-A12O3 catalyst can significantly enhance the catalytic activity toward NH3 oxidation. One fluorescent peak for fresh catalyst was different with that of exhausted catalyst. It indicates that EEFM spectroscopy was proven to be an appropriate and effective method to characterize the Pt clusters in intrinsic emission from nanosized Pt-Rh/γ-A12O3 catalyst. Results obtained from the CV may explain the significant catalytic activity of the catalysts.展开更多
文摘Mesoscale drag model is of crucial significance for the reliability and accuracy in coarse-grid EulerianEulerian two-fluid model(TFM)simulations of gas-solid flow hydrodynamics in fluidized bed reactors.Although numerous mesoscale drag models have been reported in the literature,a systematic comparison of their prediction capability from the perspective of heterogeneity analysis is still lacking.In this study,in order to investigate the effect of several typical drag models on the hydrodynamic behaviors,the nonuniformity analysis and the sensitivity to material properties,extensive coarse-grid TFM simulations of a bubbling pilot-scale fluidized bed reactor are carried out.The results demonstrate that the mesoscale drag models outperform the empirical drag model in terms of nonuniformity due to the consideration of the influence of the mesoscale structures on the drag force in the bubbling region.Furthermore,the results reveal that our previously developed three-marker gradient-based drag model considering the solid concentration gradient exhibits satisfactory performance in predicting the bubbling flow hydrodynamics.Besides,the material-property-dependent drag model considering the explicit effect of material properties on drag corrections is most sensitive to the particle diameter.This work provides guideline for possible future improvements of mesoscale models to simulate gas-solid flow more accurately and universally.
文摘The chemical looping concept provided a novel way to achieve carbon separation during the production of energy or substances. In this work, hydrogen generation with inherent CO2 capture in single packed bed reactor via this concept was discussed. Two oxygen carriers, Fe203 60 wt.% and Fe2O3 55 wt.%/CuO 5 wt.% supported by Al2O3, were made by ball milling method. First, according to the characteristics of the reduction breakthrough curve, a strict fuel supply strategy was selected to achieve simultaneous CO2 capture and HE production. Then, in the long term tests using CO as fuel, it was proved that CuO addition improved hydrogen generation with the maximum intensity of 3700 μmol H2·g^-1 Fe2O3 compared with Fe-Al of 2300 μmol HE.g^-1 Fe2O3. The overall CO2 capture efficiency remained 98%- 98.8% over 100 cycles. Moreover, the reactivity of deactivated materials was recovered nearly like that of fresh ones by sintering treatment. Finally, two kinds of complex gases consist of CO, HE, CH4 and CO2 were utilized as fuels to test the feasibility. The results showed all components could be completely converted by Fe-Cu- Al in the reduction stage. The intensity of hydrogen production and the overall CO2 capture efficiency were in the range of 2000-2400 μnol H2^g^-1 Fe2O3 and 89%, 95%, respectively.
文摘This work describes the environmentally friendly technology for oxidation of ammonia （NH3） to form nitrogen at temperatures range from 423K to 673K by selective catalytic oxidation （SCO） over a nanosized Pt- Rh/γ-A12O3 catalyst prepared by the incipient wetness impregnation method of hexachloroplatinic acid （H2PtC16） and rhodium （Ⅲ） nitrate （Rh（NO3）3） with γ-A12O3 in a tubular fixed-bed flow quartz reactor （TFBR）. The characterization of catalysts were thoroughly measured using transmission electron microscopy （TEM）, three- dimensional excitation-emission fluorescent matrix （EEFM） spectroscopy, UV-Vis absorption, dynamic light- scattering （DLS）, zeta potential meter, and cyclic voltam- metry （CV）. The results demonstrated that at a temperature of 673K and an oxygen content of4%, approximately 99% of the NH3 was removed by catalytic oxidation over the nanosized Pt-Rh/γ-A12O3 catalyst. N2 was the main product in NH3-SCO process. Further, it reveals that the oxidation of NH3 was proceeds by the over-oxidation of NH3 into NO, which was conversely reacted with the NH3 to yield N2. Therefore, the application ofnanosized Pt-Rh/γ-A12O3 catalyst can significantly enhance the catalytic activity toward NH3 oxidation. One fluorescent peak for fresh catalyst was different with that of exhausted catalyst. It indicates that EEFM spectroscopy was proven to be an appropriate and effective method to characterize the Pt clusters in intrinsic emission from nanosized Pt-Rh/γ-A12O3 catalyst. Results obtained from the CV may explain the significant catalytic activity of the catalysts.
