Waste heat recovery from hot steel slag was determined in a granular bed through the combination of numerical simulation and an industrial test method.First,the effective thermal conductivity of the granular bed was c...Waste heat recovery from hot steel slag was determined in a granular bed through the combination of numerical simulation and an industrial test method.First,the effective thermal conductivity of the granular bed was calculated.Then,the unsteady-state model was used to simulate the heat recovery under three different flow fields(O-type,S-type,and nonshielding type(Nontype)).Second,the simulation results were validated by in-situ industrial experiments.The two methods confirmed that the heat recovery efficiencies of the flow fields from high to low followed the order of Nontype,S-type,and O-type.Finally,heat recovery was carried out under the Nontype flow field in an industrial test.The heat recovery efficiency increased from~76%and~78%to~81%when the steel slag thickness decreased from 400 and 300 to 200 mm,corresponding to reductions in the steel slag mass from 3.96 and 2.97 to 1.98 t with a blower air volume of 14687 m^(3)/h.Therefore,the research results showed that numerical simulation can not only guide experiments on waste heat recovery but also optimize the flow field.Most importantly,the method proposed in this paper has achieved higher waste heat recovery from hot steel slag in industrial scale.展开更多
Ammonia(NH3)is mainly produced via the Haber-Bosch process.It was discovered that the performance of a wide variety of catalysts in NH3 synthesis could be considerably enhanced by the addition of rare earth elements(R...Ammonia(NH3)is mainly produced via the Haber-Bosch process.It was discovered that the performance of a wide variety of catalysts in NH3 synthesis could be considerably enhanced by the addition of rare earth elements(REEs).As a result,catalysts promoted by REEs,especially the Ru-based ones have been extensively investigated.In this review,we summarize the progress of utilizing REEs for ammonia synthesis and outline the prospects of using them in the design and development of highly efficient and stable catalysts for ammonia synthesis.展开更多
Spread-F is an important ionosphere pheonome-non and it has much effect on radio wave propogation. Taking magnetic inclination and declination into consideration, a theoretical model is deduced for the linear growth-r...Spread-F is an important ionosphere pheonome-non and it has much effect on radio wave propogation. Taking magnetic inclination and declination into consideration, a theoretical model is deduced for the linear growth-rate of spread-F. It is a generalization of the earlier equatorial model and a relatively complete description o f the spread-F pheonomenon. This theory shows that the magnetic configuration, i.e. the magnetic strength, inclination and declination, affects the occurrence rate greatly, which forms some regional distribution characteristics of the spread-F.展开更多
Ammonia(NH_(3))synthesis at mild conditions is of great significance,while the significant bottleneck of this process is the activation of N_(2) to realize the desired NH_(3) synthesis performance,which requires deep ...Ammonia(NH_(3))synthesis at mild conditions is of great significance,while the significant bottleneck of this process is the activation of N_(2) to realize the desired NH_(3) synthesis performance,which requires deep insight and rational design of active sites at the atomic level.Here,were synthesized atomically dispersed Co-based catalysts with different Co-N coordination numbers(CNs)to explore the coordination-sensitive NH_(3) synthesis reaction for the first time.Our studies showed that Co-based catalysts increased the NH_(3) synthesis rate gradually with a decrease in CN.The Co-N_(2) catalyst exhibited the highest NH_(3) synthesis rate of 85.3 mmol gCo^(−1) h^(−1) at 300℃ and 1 MPa,which outperformed most of the previously reported Co-based catalysts.Various characterizations and theoretical calculations demonstrated that atomically dispersed Co catalyst with low CN could generate more unoccupied Co 3d charges and tetrahedral cobalt(Ⅱ)sites.The unoccupied Co 3d charge,in turn,promoted the electron donation from the Co active center to the antibonding π-orbital(π*)of N_(2) and expedites N_(2) hydrogenation.Furthermore,the Co-N_(2) catalyst with more tetrahedral cobalt(II)sites could effectively facilitate the desorption of N-containing intermediate species(such as*NH_(3) and*N_(2)H_(4))to obtain a high NH_(3) synthesis rate.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51972019)the National Key Research and Development Program of China(No.2019YFC1905702)。
文摘Waste heat recovery from hot steel slag was determined in a granular bed through the combination of numerical simulation and an industrial test method.First,the effective thermal conductivity of the granular bed was calculated.Then,the unsteady-state model was used to simulate the heat recovery under three different flow fields(O-type,S-type,and nonshielding type(Nontype)).Second,the simulation results were validated by in-situ industrial experiments.The two methods confirmed that the heat recovery efficiencies of the flow fields from high to low followed the order of Nontype,S-type,and O-type.Finally,heat recovery was carried out under the Nontype flow field in an industrial test.The heat recovery efficiency increased from~76%and~78%to~81%when the steel slag thickness decreased from 400 and 300 to 200 mm,corresponding to reductions in the steel slag mass from 3.96 and 2.97 to 1.98 t with a blower air volume of 14687 m^(3)/h.Therefore,the research results showed that numerical simulation can not only guide experiments on waste heat recovery but also optimize the flow field.Most importantly,the method proposed in this paper has achieved higher waste heat recovery from hot steel slag in industrial scale.
基金Project supported by the National Natural Science Foundation of China(22038002,21972019)。
文摘Ammonia(NH3)is mainly produced via the Haber-Bosch process.It was discovered that the performance of a wide variety of catalysts in NH3 synthesis could be considerably enhanced by the addition of rare earth elements(REEs).As a result,catalysts promoted by REEs,especially the Ru-based ones have been extensively investigated.In this review,we summarize the progress of utilizing REEs for ammonia synthesis and outline the prospects of using them in the design and development of highly efficient and stable catalysts for ammonia synthesis.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 49874041 and 49990454).
文摘Spread-F is an important ionosphere pheonome-non and it has much effect on radio wave propogation. Taking magnetic inclination and declination into consideration, a theoretical model is deduced for the linear growth-rate of spread-F. It is a generalization of the earlier equatorial model and a relatively complete description o f the spread-F pheonomenon. This theory shows that the magnetic configuration, i.e. the magnetic strength, inclination and declination, affects the occurrence rate greatly, which forms some regional distribution characteristics of the spread-F.
基金supported by the National Key Natural Science Foundation of China(grant no.22038002)the National Natural Science Foundation of China(grant no.21972019).
文摘Ammonia(NH_(3))synthesis at mild conditions is of great significance,while the significant bottleneck of this process is the activation of N_(2) to realize the desired NH_(3) synthesis performance,which requires deep insight and rational design of active sites at the atomic level.Here,were synthesized atomically dispersed Co-based catalysts with different Co-N coordination numbers(CNs)to explore the coordination-sensitive NH_(3) synthesis reaction for the first time.Our studies showed that Co-based catalysts increased the NH_(3) synthesis rate gradually with a decrease in CN.The Co-N_(2) catalyst exhibited the highest NH_(3) synthesis rate of 85.3 mmol gCo^(−1) h^(−1) at 300℃ and 1 MPa,which outperformed most of the previously reported Co-based catalysts.Various characterizations and theoretical calculations demonstrated that atomically dispersed Co catalyst with low CN could generate more unoccupied Co 3d charges and tetrahedral cobalt(Ⅱ)sites.The unoccupied Co 3d charge,in turn,promoted the electron donation from the Co active center to the antibonding π-orbital(π*)of N_(2) and expedites N_(2) hydrogenation.Furthermore,the Co-N_(2) catalyst with more tetrahedral cobalt(II)sites could effectively facilitate the desorption of N-containing intermediate species(such as*NH_(3) and*N_(2)H_(4))to obtain a high NH_(3) synthesis rate.
