Gas-solid two-phase turbulent flows,mass transfer,heat transfer and catalytic cracking reactions areknown to exert interrelated influences in commercial fluid catalytic cracking(FCC)riser reactors.In the presentpaper,...Gas-solid two-phase turbulent flows,mass transfer,heat transfer and catalytic cracking reactions areknown to exert interrelated influences in commercial fluid catalytic cracking(FCC)riser reactors.In the presentpaper,a three-dimensional turbulent gas-solid two-phase flow-reaction model for FCC riser reactors was devel-oped.The model took into account the gas-solid two-phase turbulent flows,inter-phase heat transfer,masstransfer,catalytic cracking reactions and their interrelated influence.The k-V-k_P two-phase turbulence modelwas employed and modified for the two-phase turbulent flow patterns with relatively high particle concentration.Boundary conditions for the flow-reaction model were given.Related numerical algorithm was formed and a nu-merical code was drawn up.Numerical modeling for commercial FCC riser reactors could be carried out with thepresented model.展开更多
Numerical simulation on the flow,heat transfer and cracking reactions in commercial fluid catalyticcracking(FCC)riser reactors were carried out employing the developed turbulent gas-solid two-phase flow-reac-tion mode...Numerical simulation on the flow,heat transfer and cracking reactions in commercial fluid catalyticcracking(FCC)riser reactors were carried out employing the developed turbulent gas-solid two-phase flow-reac-tion model for FCC riser reactors given in Part Ⅰ of the present paper.Detailed information about the turbulentflow fields in the riser reactor obtained revealed the basic characteristics of the gas-solid two-phase turbulentflows when heat transfer and catalytic cracking reactions were co-existing in the riser.Results showed that thedistributions of the flow,the turbulence kinetic energy and the catalyst particle concentration are not uniform inthe axial,radial and tangential directions.The most complicated part of the riser reactor is the feed injectingzone.The complicated configuration of the turbulent gas-solid two-phase flows would exert a great influence onthe results of interphase heat transfer and cracking reactions.展开更多
A mathematical model for heap bioleaching is developed to analyze heat transfer, oxygen flow, target ion distribution and oxidation leaching rate in the heap. The model equations are solved with Comsol Multiphysics so...A mathematical model for heap bioleaching is developed to analyze heat transfer, oxygen flow, target ion distribution and oxidation leaching rate in the heap. The model equations are solved with Comsol Multiphysics software. Numerical simulation results show the following facts： Concentration of oxygen is relatively high along the boundary of the slope, and low in the center part where leaching rate is slow. Temper- ature is relatively low along the slope and reaches the highest along the bottom region near the slope, with difference being more than 6℃. Concentration of target mental ions is the highest in the bottom region near the slope. Oxidation leaching rate is relatively large in the bottom and slope part with a fast reaction rate, and small in the other part with low oxygen concentration.展开更多
In the present paper,a two-dimensional flow-reaction mathematical model is developed by integrating a deliberate kinetic and coking model with the k-ε turbulence model and heat transfer model that contains the conduc...In the present paper,a two-dimensional flow-reaction mathematical model is developed by integrating a deliberate kinetic and coking model with the k-ε turbulence model and heat transfer model that contains the conduction within the laminar layer near the tubular wall. Numerical simulation on a naphtha cracker and an ethane cracker in Yanshan Petrochemical company utilizing the developed flow-reaction model showed that the predicted exit composition is in agreement with the production data. Reasonable distributions of some product yields and engineering parameters are also obtained in the radial and axial directions. This suggests that the established flow-reaction model can be used for performance simulation in commercial tubular reactor of steam crackers.展开更多
The AI-AIN-Si composites were prepared in the gas-in-liquid in situ synthesized flow-reaction-system, which was implemented by a powder metallurgy and reaction sin- tering route. The experimental results showed that A...The AI-AIN-Si composites were prepared in the gas-in-liquid in situ synthesized flow-reaction-system, which was implemented by a powder metallurgy and reaction sin- tering route. The experimental results showed that A1-AIN- 50SiB material （prepared by ball-milling powders） and AI- AIN-50SiM material （prepared by mixing powders） exhibited the semi-continuous Si structures and the isolated Si islands, respectively. Subsequently, the AI-AIN-50Si materials were selected as the model materials by phase identification and microstructure analysis. The dynamic microstructural evolu- tion of AI-AIN-50Si materials was investigated using the computational fluid dynamics （CFD） method. Mathematical models and simulation results showed that the in situ synthesis of AIN was strongly influenced by the structure and the flow- path （（Cg,N2/lg,N2）＋（Cs,AlN/ls,AiN））. The flow paths of AI-AIN-50Si^B material were restricted by the semi-continuous Si. These Si structures can promote the formation of the strong turbulence with gradually weakened fluctuation, so that the in situ synthesis of AIN was interconnected and surrounded by an interpenetrating Si network. In contrast, the flow paths of AI- AIN-50Si^B material can easily pass through the isolated Si due to its mild turbulence with linear relationship. As a result, AIN was separated by the isolated Si and agglomerated in the matrix. Overall, the present work provides new insights into dynamic microstructural evolution in in situ reaction sinter- ing systems.展开更多
The influences of the convective boundary condition and heat generation/absorption on magnetohydro- dynamic boundary layer flow of a Maxwell fluid over a stretching surface in the presence of nanoparticles have been n...The influences of the convective boundary condition and heat generation/absorption on magnetohydro- dynamic boundary layer flow of a Maxwell fluid over a stretching surface in the presence of nanoparticles have been numerically investigated. In the model, the physical mechanisms responsible for Brownian motion and thermophoresis with a chemical reaction are considered. Similarity equations are derived and then solved using the shooting method with the fourth-order Runge-Kutta integration scheme, The rates of heat and mass transfer are enhanced with a destructive chemical reaction and Blot number. The opposite influence is found with a generative chemical reaction in the presence of Brownian motion and the thermophoretic property.展开更多
文摘Gas-solid two-phase turbulent flows,mass transfer,heat transfer and catalytic cracking reactions areknown to exert interrelated influences in commercial fluid catalytic cracking(FCC)riser reactors.In the presentpaper,a three-dimensional turbulent gas-solid two-phase flow-reaction model for FCC riser reactors was devel-oped.The model took into account the gas-solid two-phase turbulent flows,inter-phase heat transfer,masstransfer,catalytic cracking reactions and their interrelated influence.The k-V-k_P two-phase turbulence modelwas employed and modified for the two-phase turbulent flow patterns with relatively high particle concentration.Boundary conditions for the flow-reaction model were given.Related numerical algorithm was formed and a nu-merical code was drawn up.Numerical modeling for commercial FCC riser reactors could be carried out with thepresented model.
文摘Numerical simulation on the flow,heat transfer and cracking reactions in commercial fluid catalyticcracking(FCC)riser reactors were carried out employing the developed turbulent gas-solid two-phase flow-reac-tion model for FCC riser reactors given in Part Ⅰ of the present paper.Detailed information about the turbulentflow fields in the riser reactor obtained revealed the basic characteristics of the gas-solid two-phase turbulentflows when heat transfer and catalytic cracking reactions were co-existing in the riser.Results showed that thedistributions of the flow,the turbulence kinetic energy and the catalyst particle concentration are not uniform inthe axial,radial and tangential directions.The most complicated part of the riser reactor is the feed injectingzone.The complicated configuration of the turbulent gas-solid two-phase flows would exert a great influence onthe results of interphase heat transfer and cracking reactions.
基金Project supported by the National Natural Science Foundation of China (Nos. 50934002 and 50774011)the Postdoctoral Science Foundation of China (No. 20090450014)the DoctoralNatural Science Foundation of China (No. 20070008038)
文摘A mathematical model for heap bioleaching is developed to analyze heat transfer, oxygen flow, target ion distribution and oxidation leaching rate in the heap. The model equations are solved with Comsol Multiphysics software. Numerical simulation results show the following facts： Concentration of oxygen is relatively high along the boundary of the slope, and low in the center part where leaching rate is slow. Temper- ature is relatively low along the slope and reaches the highest along the bottom region near the slope, with difference being more than 6℃. Concentration of target mental ions is the highest in the bottom region near the slope. Oxidation leaching rate is relatively large in the bottom and slope part with a fast reaction rate, and small in the other part with low oxygen concentration.
文摘In the present paper,a two-dimensional flow-reaction mathematical model is developed by integrating a deliberate kinetic and coking model with the k-ε turbulence model and heat transfer model that contains the conduction within the laminar layer near the tubular wall. Numerical simulation on a naphtha cracker and an ethane cracker in Yanshan Petrochemical company utilizing the developed flow-reaction model showed that the predicted exit composition is in agreement with the production data. Reasonable distributions of some product yields and engineering parameters are also obtained in the radial and axial directions. This suggests that the established flow-reaction model can be used for performance simulation in commercial tubular reactor of steam crackers.
基金supported by the financial support of the National Natural Science Foundation of China (51171146 and 51101177)the Program for Key Science and Technology Innovative Research Team of Shaanxi Province (2013KCT-05)
文摘The AI-AIN-Si composites were prepared in the gas-in-liquid in situ synthesized flow-reaction-system, which was implemented by a powder metallurgy and reaction sin- tering route. The experimental results showed that A1-AIN- 50SiB material （prepared by ball-milling powders） and AI- AIN-50SiM material （prepared by mixing powders） exhibited the semi-continuous Si structures and the isolated Si islands, respectively. Subsequently, the AI-AIN-50Si materials were selected as the model materials by phase identification and microstructure analysis. The dynamic microstructural evolu- tion of AI-AIN-50Si materials was investigated using the computational fluid dynamics （CFD） method. Mathematical models and simulation results showed that the in situ synthesis of AIN was strongly influenced by the structure and the flow- path （（Cg,N2/lg,N2）＋（Cs,AlN/ls,AiN））. The flow paths of AI-AIN-50Si^B material were restricted by the semi-continuous Si. These Si structures can promote the formation of the strong turbulence with gradually weakened fluctuation, so that the in situ synthesis of AIN was interconnected and surrounded by an interpenetrating Si network. In contrast, the flow paths of AI- AIN-50Si^B material can easily pass through the isolated Si due to its mild turbulence with linear relationship. As a result, AIN was separated by the isolated Si and agglomerated in the matrix. Overall, the present work provides new insights into dynamic microstructural evolution in in situ reaction sinter- ing systems.
文摘The influences of the convective boundary condition and heat generation/absorption on magnetohydro- dynamic boundary layer flow of a Maxwell fluid over a stretching surface in the presence of nanoparticles have been numerically investigated. In the model, the physical mechanisms responsible for Brownian motion and thermophoresis with a chemical reaction are considered. Similarity equations are derived and then solved using the shooting method with the fourth-order Runge-Kutta integration scheme, The rates of heat and mass transfer are enhanced with a destructive chemical reaction and Blot number. The opposite influence is found with a generative chemical reaction in the presence of Brownian motion and the thermophoretic property.
