Study on gas–liquid flow in stirred tank with two combinations of dual-impeller(six-bent-bladed turbine(6BT)+six-inclined-blade down-pumping turbine(6 ITD),the six-bent-bladed turbine(6BT)+six-inclinedblade up-pumpin...Study on gas–liquid flow in stirred tank with two combinations of dual-impeller(six-bent-bladed turbine(6BT)+six-inclined-blade down-pumping turbine(6 ITD),the six-bent-bladed turbine(6BT)+six-inclinedblade up-pumping turbine(6ITU))was conducted using computational fluid dynamics(CFD)and population balance model(PBM)(CFD-PBM)coupled model.The local bubble size was captured by particle image velocimetry(PIV)measurement.The gas holdup,bubble size distribution and gas–liquid interfacial area were explored at different conditions through numerical simulation.The results showed that the 4 mm bubbles accounted for the largest proportion of 33%at the gas flow rates Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1) for combined impeller of 6BT+6ITU,while the bubbles of 4.7 mm and 5.5 mm were the largest proportion for 6BT+6ITD combination,i.e.25%at Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1),respectively,which indicated that 6BT+6ITU could reduce bubble size effectively and promote gas dispersion.In addition,the gas holdup around impellers was increased obviously with the speed compared with gas flow rate.So it was concluded that 6ITU impeller could be more conductive to the bubble dispersion with more uniform bubble size,which embodied the advantages of 6BT+6ITU combination in gas–liquid mixing.展开更多
Gas–liquid flow and bubble coalescence and breakup behavior were studied in a top blown-rotary agitated reactor for steelmaking.Several important models of bubble coalescence and breakup mechanisms were considered an...Gas–liquid flow and bubble coalescence and breakup behavior were studied in a top blown-rotary agitated reactor for steelmaking.Several important models of bubble coalescence and breakup mechanisms were considered and compared,and water model experiment was carried out to verify and optimize the mathematical models.The influence of different operating parameters including paddle arrangement,stirring speed and top blowing flow rate on the bubble size and distribution was revealed.The results show that the predicted bubble size and distribution present a good agreement with the experimental results using the improved Luo–Laakkonen combination model.As the position of the stirring paddle moves from the center to the side wall,the bubble distribution in the reactor becomes more uniform,and the bubble size gradually decreases.With the increase in the paddle rotation speed,the bubble size decreases.However,this effect begins to weaken when the paddle rotation speed exceeds 150 r/min.Increasing the top blowing flow rate will increase the bubble size in the reactor,but it has a weak effect on bubble dispersion.When the top blowing rate exceeds 2.0 m^(3)/h,the bubble size in the bath is basically not less than 5 mm.展开更多
建立了描述FCC提升管中气-固流动行为的CFD-PBM耦合模型,模型同时考虑了颗粒动力学和颗粒聚并破碎内核。讨论了求解耦合模型中众体平衡方程(PBE)的3种典型矩方法[即:正交矩方法(quadrature method of moments,QMOM),直接正交矩方法(dire...建立了描述FCC提升管中气-固流动行为的CFD-PBM耦合模型,模型同时考虑了颗粒动力学和颗粒聚并破碎内核。讨论了求解耦合模型中众体平衡方程(PBE)的3种典型矩方法[即:正交矩方法(quadrature method of moments,QMOM),直接正交矩方法(direct quadrature method of moments,DQMOM)和固定轴点正交矩方法(fixed pivot quadrature method of moments,FPQMOM)]对模拟结果的影响。研究结果表明3种矩方法均能合理预测提升管内径向和轴向颗粒体积分数和颗粒速度分布。通过将模拟结果与实验结果进行比较,表明QMOM在反应器结构简单情况下,计算结果更接近于实际情况。展开更多
Frame blades were used to replace traditional propeller blades to enhance the leaching step efficiency of Becher process.A combined approach of leaching,electrochemical experiments,and numerical simulations was employ...Frame blades were used to replace traditional propeller blades to enhance the leaching step efficiency of Becher process.A combined approach of leaching,electrochemical experiments,and numerical simulations was employed.Results demonstrate a significant improvement in leaching efficiency using frame blades compared to propellers,reducing reaction time from 15 to 10 h.Even at a stirring speed of 300 r/min,frame blades perform better than propellers at 500 r/min.Kinetics analysis indicates that the leaching process is controlled by surface chemical reactions.CFD-PBM simulations reveal that frame blades at 300 r/min generate larger bubbles and higher turbulent kinetic energy than propeller blades at 500 r/min.Frame blades enhance leaching efficiency by refining bubble size to improve oxygen mass transfer and by increasing turbulent kinetic energy for better mixing.展开更多
基金supported by the National Natural Science Foundation of China(52176040)Shandong Provincial Natural Science Foundation of China(ZR2018LE015)。
文摘Study on gas–liquid flow in stirred tank with two combinations of dual-impeller(six-bent-bladed turbine(6BT)+six-inclined-blade down-pumping turbine(6 ITD),the six-bent-bladed turbine(6BT)+six-inclinedblade up-pumping turbine(6ITU))was conducted using computational fluid dynamics(CFD)and population balance model(PBM)(CFD-PBM)coupled model.The local bubble size was captured by particle image velocimetry(PIV)measurement.The gas holdup,bubble size distribution and gas–liquid interfacial area were explored at different conditions through numerical simulation.The results showed that the 4 mm bubbles accounted for the largest proportion of 33%at the gas flow rates Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1) for combined impeller of 6BT+6ITU,while the bubbles of 4.7 mm and 5.5 mm were the largest proportion for 6BT+6ITD combination,i.e.25%at Q=0.76 m^(3)·h^(-1) and 22%at Q=1.52 m^(3)·h^(-1),respectively,which indicated that 6BT+6ITU could reduce bubble size effectively and promote gas dispersion.In addition,the gas holdup around impellers was increased obviously with the speed compared with gas flow rate.So it was concluded that 6ITU impeller could be more conductive to the bubble dispersion with more uniform bubble size,which embodied the advantages of 6BT+6ITU combination in gas–liquid mixing.
基金The authors wish to express thanks to the National Natural Science Foundation of China(51604147 and 51774178)for supporting this work.
文摘Gas–liquid flow and bubble coalescence and breakup behavior were studied in a top blown-rotary agitated reactor for steelmaking.Several important models of bubble coalescence and breakup mechanisms were considered and compared,and water model experiment was carried out to verify and optimize the mathematical models.The influence of different operating parameters including paddle arrangement,stirring speed and top blowing flow rate on the bubble size and distribution was revealed.The results show that the predicted bubble size and distribution present a good agreement with the experimental results using the improved Luo–Laakkonen combination model.As the position of the stirring paddle moves from the center to the side wall,the bubble distribution in the reactor becomes more uniform,and the bubble size gradually decreases.With the increase in the paddle rotation speed,the bubble size decreases.However,this effect begins to weaken when the paddle rotation speed exceeds 150 r/min.Increasing the top blowing flow rate will increase the bubble size in the reactor,but it has a weak effect on bubble dispersion.When the top blowing rate exceeds 2.0 m^(3)/h,the bubble size in the bath is basically not less than 5 mm.
文摘建立了描述FCC提升管中气-固流动行为的CFD-PBM耦合模型,模型同时考虑了颗粒动力学和颗粒聚并破碎内核。讨论了求解耦合模型中众体平衡方程(PBE)的3种典型矩方法[即:正交矩方法(quadrature method of moments,QMOM),直接正交矩方法(direct quadrature method of moments,DQMOM)和固定轴点正交矩方法(fixed pivot quadrature method of moments,FPQMOM)]对模拟结果的影响。研究结果表明3种矩方法均能合理预测提升管内径向和轴向颗粒体积分数和颗粒速度分布。通过将模拟结果与实验结果进行比较,表明QMOM在反应器结构简单情况下,计算结果更接近于实际情况。
基金supported by the National Natural Science Foundation of China(No.U1908225)the Cross-Integration and Collaborative Development Project of Northeastern University,China(No.N2225013).
文摘Frame blades were used to replace traditional propeller blades to enhance the leaching step efficiency of Becher process.A combined approach of leaching,electrochemical experiments,and numerical simulations was employed.Results demonstrate a significant improvement in leaching efficiency using frame blades compared to propellers,reducing reaction time from 15 to 10 h.Even at a stirring speed of 300 r/min,frame blades perform better than propellers at 500 r/min.Kinetics analysis indicates that the leaching process is controlled by surface chemical reactions.CFD-PBM simulations reveal that frame blades at 300 r/min generate larger bubbles and higher turbulent kinetic energy than propeller blades at 500 r/min.Frame blades enhance leaching efficiency by refining bubble size to improve oxygen mass transfer and by increasing turbulent kinetic energy for better mixing.
