In this study,the effect of channel baffles and louver baffles on the flow pattern in the large-scale industrial fluidized beds was studied by computational fluid dynamics(CFD)methods.Then,the effect of flow pattern o...In this study,the effect of channel baffles and louver baffles on the flow pattern in the large-scale industrial fluidized beds was studied by computational fluid dynamics(CFD)methods.Then,the effect of flow pattern on the chemical reaction performance was studied for the first time.Simulation results showed that the gas velocity distributed more uniformly,solid particles dispersed more homogeneously and aggregation scarcely occurred in the fluidized bed with louver baffles than that with channel baffles.The residence time distribution indicated that louver baffles remarkably suppressed gas back-mixing in comparison with channel baffles.The reasonable agreements of pressure distribution and reaction results between the simulation in the bed with channel baffles and the data on a large-scale industrial apparatus demonstrated the accuracy of the CFD model.The predicted conversion of SiCl_(4) in the bed with louver baffles(27.44%)was higher than that with channel baffles(22.69%),indicating that louver baffles markedly improved the performance of the fluidized bed.This study could provide useful information for future structural improvements of baffles in large-scale fluidized beds.展开更多
The practical application of silica aerogels is an enormous challenge due to the difficulties in improving both mechanical property and thermal insulation performance.In this work,silk fibroin was used as scaffold to ...The practical application of silica aerogels is an enormous challenge due to the difficulties in improving both mechanical property and thermal insulation performance.In this work,silk fibroin was used as scaffold to improve the mechanical property and thermal insulation performance of silica aerogels.The ungelled SiO_(2)precursor solution was impregnated into silk fibroin to prepare silk fibroin-SiO_(2)composite aerogels via sol−gel method followed by freeze-drying.By virtue of the interfacial hydrogen-bonding interactions and chemical reactions between silk fibroin and silica nanoparticles,SiO_(2)was well-dispersed in the silk fibroin aerogel and composite aerogels exhibited enhanced mechanical property.By increasing the loading of silk fibroin from 15 wt%to 21 wt%,the maximum compressive stress was enhanced from 0.266 to 0.508 MPa when the strain reached 50%.The thermal insulation performance of the composite aerogels was improved compared with pure silica aerogel,as evidenced that the thermal conductivity was decreased from 0.0668 to 0.0341 W∙m‒1∙K‒1.Moreover,the composite aerogels exhibited better hydrophobicity and fire retardancy compared to pure silica aerogel.Our work provides a novel approach to preparing silk fibroin-SiO_(2)composite aerogels with enhanced mechanical property and thermal insulation performance,which has potential application as thermal insulation material.展开更多
基金supported by the National Key Research and Development Program of China(2018YFB0604900)the National Natural Science Foundation of China(21978198)the National Key Research and Development Program of China(2016YFF0102503)。
文摘In this study,the effect of channel baffles and louver baffles on the flow pattern in the large-scale industrial fluidized beds was studied by computational fluid dynamics(CFD)methods.Then,the effect of flow pattern on the chemical reaction performance was studied for the first time.Simulation results showed that the gas velocity distributed more uniformly,solid particles dispersed more homogeneously and aggregation scarcely occurred in the fluidized bed with louver baffles than that with channel baffles.The residence time distribution indicated that louver baffles remarkably suppressed gas back-mixing in comparison with channel baffles.The reasonable agreements of pressure distribution and reaction results between the simulation in the bed with channel baffles and the data on a large-scale industrial apparatus demonstrated the accuracy of the CFD model.The predicted conversion of SiCl_(4) in the bed with louver baffles(27.44%)was higher than that with channel baffles(22.69%),indicating that louver baffles markedly improved the performance of the fluidized bed.This study could provide useful information for future structural improvements of baffles in large-scale fluidized beds.
文摘The practical application of silica aerogels is an enormous challenge due to the difficulties in improving both mechanical property and thermal insulation performance.In this work,silk fibroin was used as scaffold to improve the mechanical property and thermal insulation performance of silica aerogels.The ungelled SiO_(2)precursor solution was impregnated into silk fibroin to prepare silk fibroin-SiO_(2)composite aerogels via sol−gel method followed by freeze-drying.By virtue of the interfacial hydrogen-bonding interactions and chemical reactions between silk fibroin and silica nanoparticles,SiO_(2)was well-dispersed in the silk fibroin aerogel and composite aerogels exhibited enhanced mechanical property.By increasing the loading of silk fibroin from 15 wt%to 21 wt%,the maximum compressive stress was enhanced from 0.266 to 0.508 MPa when the strain reached 50%.The thermal insulation performance of the composite aerogels was improved compared with pure silica aerogel,as evidenced that the thermal conductivity was decreased from 0.0668 to 0.0341 W∙m‒1∙K‒1.Moreover,the composite aerogels exhibited better hydrophobicity and fire retardancy compared to pure silica aerogel.Our work provides a novel approach to preparing silk fibroin-SiO_(2)composite aerogels with enhanced mechanical property and thermal insulation performance,which has potential application as thermal insulation material.
