Liquid-liquid dispersion is often performed in stirred tanks,which are valued for their ease of operation,high droplet generation rate and effective droplet dispersion.Many relevant simulations use the Eulerian-Euleri...Liquid-liquid dispersion is often performed in stirred tanks,which are valued for their ease of operation,high droplet generation rate and effective droplet dispersion.Many relevant simulations use the Eulerian-Eulerian method,combining population balance equations with statistical models to forecast droplet breakage.Conversely,the Eulerian-Lagrangian(E-L)method provides precise tracking of individual droplets,which is crucial for simulating dispersion processes.However,E-L simulation faces challenges in integrating droplet breakage effectively.To address this issue,our research introduces a probabilistic approach for droplet breakages.It assumes that a longer time increases the likelihood of breakup;a droplet breaks if the calculated probability exceeds a random value from 0 to 1.Consequently,the simulated breakage frequency becomes independent of the Lagrangian time step.The Sauter mean diameter and droplet size distribution can be accurately predicted by this probabilistic approach.By closely monitoring droplet motion,we reveal the complexity of droplet trajectories and the detailed patterns of circulation in stirred tanks.These insights contribute to a deeper understanding of liquidliquid dispersion dynamics.展开更多
Fractal theory provides a new strategy for equipment design.In this work,we propose a novel H-like fractal(HLF)impeller to improve the uniformity of the distribution of hydrodynamics in stirred tanks.The impellers are...Fractal theory provides a new strategy for equipment design.In this work,we propose a novel H-like fractal(HLF)impeller to improve the uniformity of the distribution of hydrodynamics in stirred tanks.The impellers are constructed by replacing two vertical blades or four legs with two or four H-like subblades by fractal iterations,respectively.Flow characteristics including velocity and turbulent kinetic energy(TKE)distributions,vortices,power number,are predicted by large eddy simulation.Compared with Rushton turbine(RT)impeller when H/T=1(or dual RTs when H/T=1.5,triple RTs when H/T=2),the HLF impeller can produce a flow field with more uniform distributions of larger velocities and TKE level.The impeller with more fractal iteration times can further improve the distribution uniformity of hydrodynamics in the case of high H/T.Power analysis shows that this is mainly due to the improved energy utilization efficiency by the fractal structure design.展开更多
Leveraging big data signal processing offers a pathway to the development of artificial intelligencedriven equipment.The analysis of fluid flow signals and the characterization of fluid flow behavior are of critical i...Leveraging big data signal processing offers a pathway to the development of artificial intelligencedriven equipment.The analysis of fluid flow signals and the characterization of fluid flow behavior are of critical in two-phase flow studies.Significant research efforts have focused on discerning flow regimes using various signal analysis methods.In this review,recent advances in time series signals analysis algorithms for stirred tank reactors have been summarized,and the detailed methodologies are categorized into the frequency domain methods,time-frequency domain methods,and state space methods.The strengths,limitations,and notable findings of each algorithm are highlighted.Additionally,the interrelationships between these methodologies have also been discussed,as well as the present progress achieved in various applications.Future research directions and challenges are also predicted to provide an overview of current research trends in data mining of time series for analyzing flow regimes and chaotic signals.This review offers a comprehensive summary for extracting and characterizing fluid flow behavior and serves as a theoretical reference for optimizing the characterization of chaotic signals in future research endeavors.展开更多
The structural and operational optimization of gas-liquid stirred bioreactors presents both complexity and critical importance for enhancing mass transfer performance. This study proposes a machine learning (ML)-drive...The structural and operational optimization of gas-liquid stirred bioreactors presents both complexity and critical importance for enhancing mass transfer performance. This study proposes a machine learning (ML)-driven approach to identify key features and predict the volumetric mass transfer coefficient (kLa). Four ML models were adopted and compared for kLa prediction in Newtonian and non-Newtonian fluids by evaluative indices, with CatBoost and XGBoost emerging as the optimal models, respectively. Specifically, it is demonstrated that Catboost has higher prediction accuracy (AARD = 18.84%) than empirical equations by effectively incorporating multidimensional features (structural, impeller, and operational), while simultaneously extending applicability to diverse Newtonian fluids. For non-Newtonian fluids, XGBoost outperforms empirical equations by effectively incorporating fluid rheological parameters (consistency coefficient, power-law index), thereby better capturing shear-thinning behavior. Feature importance analysis further identified rotational speed (for Newtonian fluids) and liquid height (for non-Newtonian fluids) as the key features, while 2D partial dependence analysis establishes quantitative optimization ranges. This ML approach provides an efficient predictive tool for gas-liquid stirred bioreactor design and optimization.展开更多
The improved Intermig impeller has been used in the seed precipitation tank in China, which could enhance the mixing and suspension of Al(OH)3 particles and the power consumption declined largely. The flow field, soli...The improved Intermig impeller has been used in the seed precipitation tank in China, which could enhance the mixing and suspension of Al(OH)3 particles and the power consumption declined largely. The flow field, solids hold-up, cloud height, just off-bottom speed and power consumptions were investigated in solid-liquid mixing system with this new type of impeller by CFD and water experiment methods. Compared with the standard Intermig impeller, the improved one coupled with specially sloped baffles could promote the fluid circulation, create better solids suspension and consume less power. Besides lower impeller off-bottom clearance is good for solid suspension and distribution. The just-off-bottom speed was also determined by a power number criterion. Meanwhile, the predicted results were in good agreement with the experimental data.展开更多
[Objective] In this study, the aim was to study the optimal formula and technique of honey stirred yoghurt. [Method] The optimum formula and production technique of the honey stirred yoghurt were confirmed by studying...[Objective] In this study, the aim was to study the optimal formula and technique of honey stirred yoghurt. [Method] The optimum formula and production technique of the honey stirred yoghurt were confirmed by studying the effects of the additive amount of honey, the adding time of honey, thermal death point, the ho- mogenization pressure and stability test on the sensory quality of stirred yoghurt. [Result] The experiment showed that the fermentation temperature of the honey stirred yoghurt should not be too high, and it should be close to that of common yoghurt. In addition, the fermentation time should not be too long, because along with the extension of fermentation time, there would be abnormal smell in the yo- gurt. The optimum formula and production technique were as follows： the additive amount of honey, sugarcane and fermentation agent was respectively 3%; two-sec- tion homogeneous pressures of the fresh milk were I ： 70 MPa, I1：30 MPa; the thermal death point was 85 ℃ and the time was 10 min; the fermentation occurred at 42℃, and the fermentation of the products was stopped when the ultimate acidity was among 0.70%-0.75%. [Conclusion] The study could provide some refer- ences for the production and processing of honey stirred yoghurt.展开更多
Research shows that producing fermented camel milk is hard because of the milk’s inability to form a firm coagulum, attributed to low levels of κ-casein and ꞵ-lactoglobulin and the large casein micelle size, leading...Research shows that producing fermented camel milk is hard because of the milk’s inability to form a firm coagulum, attributed to low levels of κ-casein and ꞵ-lactoglobulin and the large casein micelle size, leading to a weak network of casein formation. In an effort to address this issue, researchers turned to corn starch as a thickening agent, discovering that a concentration of 2.0% effectively improved the viscosity and significantly reduced syneresis in stirred camel milk yoghurt and cultured camel milk. This study explores alternatives to corn starch, focusing on butternut squash seeds as a promising substitute due to their hydrocolloid composition. By incorporating butternut squash (Cucurbita moschata) seed powder (BSSP) as a thickening agent, this study aimed at enhancing the chemical and rheological properties of stirred camel milk yoghurt and cultured camel milk. Fermented camel milk was prepared using 4 litres of camel milk, 2% starter cultures (thermophilic culture for yoghurt and mesophilic aromatic culture for stirred cultured camel milk) and BSSP 0.0% (negative control), 0.4%, 0.8%, 1.2%, 1.6%, 2.0% mixed with 0.4% gelatin. 2.0% corn starch mixed with 0.4% gelatin was used as a standard for comparison. Results showed that increasing the BSSP level significantly (p < 0.05) decreased the moisture content while increasing the total solid content of stirred fermented camel milk products. There was an increase in ash content with an increase in BSSP levels. There was a significant (p < 0.05) reduction in the pH, with an increase in BSSP levels in stirred fermented camel milk samples. Increasing the concentration of BSSP from 0.4% to 2.0% resulted in a significant (p < 0.05) increase in viscosity and a reduction in syneresis of stirred camel milk yoghurt and stirred cultured camel milk samples. This study demonstrated that BSSP effectively enhances the viscosity, reduces syneresis and increases acidity in stirred fermented camel milk products during storage.展开更多
Physical upgrading of graphite is typically achieved with many stages of grinding and flotation to produce a concentrate with approximately 95% carbon grade.An innovative grinding and column flotation process has been...Physical upgrading of graphite is typically achieved with many stages of grinding and flotation to produce a concentrate with approximately 95% carbon grade.An innovative grinding and column flotation process has been developed for efficient graphite upgrading to substantially simplify the process flowsheet and reduce operating costs.In this process,a high-pressure grinding roller(HPGR) and a stirred mill were employed as primary comminution techniques and a nanobubble flotation column as a key separation process.The results obtained with a crystalline flake graphite sample with a carbon grade of 11.15% show that the novel process can produce a concentrate with 94.82% carbon grade and 97.89% recovery from an open circuit of one rougher and two cleaner flotation stages.Scanning electron microscope(SEM)microphotographs indicate that HPGR offers the advantage of more effective protection of graphite flakes during crushing.Grinding test results show that stirred mill could not only protect graphite flakes but also promote the efficient liberation of graphite.Compared with the traditional flotation process,nanobubble flotation can effectively recover ultrafine graphite.The new process possesses a number of important advantages over the traditional method,including substantially higher graphite recovery,greatly simplified process flowsheet,better protection of flake size,reduced reagent consumption and process costs,etc.展开更多
The gas-liquid flow field in a stirred tank with a Rushton diskturbine, including the impeller region, was numerically simulatedusing the improved inner-outer iterative procedure. Thecharacteristic features of the sti...The gas-liquid flow field in a stirred tank with a Rushton diskturbine, including the impeller region, was numerically simulatedusing the improved inner-outer iterative procedure. Thecharacteristic features of the stirred tank, such as gas cavity andaccumulation of gas at the two sides of wall baffles, can be capturedby the simulation. The simulated results agree well with availableexperimental data. Since the improved inner-outer iterative algorithmdemands on empirical formula and experimental data for the impellerregion, and the approach seems generally applicable for simulatinggas-liquid stirred tanks.展开更多
The effect of mixing on the precipitation of barium sulfate in a continuous stirred tank is simulated numerically with different feeding location, feed concentration, impeller speed and residence time through solving ...The effect of mixing on the precipitation of barium sulfate in a continuous stirred tank is simulated numerically with different feeding location, feed concentration, impeller speed and residence time through solving the standard momentum and mass transport equations in combination with the moment equations for crystal population balance. The numerical method was validated with the literature data. The simulation results including the distribution of the local supersaturation ratio distribution in the precipitator, mean crystal size and coefficient of variation under different operating conditions compared well with experimental data in the literature. The effect of the presence of a draft tube on precipitation were also investigated, and it is suggested that the installation of a draft tube increased the mean crystal size, in general agreement with experimental work in the literature.展开更多
To improve the efficiency of the desulfurization process, the drawdown mechanism of light particles in stirred tank is studied in this paper. For both up and down pumping modes, the just drawdown speeds(Njd) of floati...To improve the efficiency of the desulfurization process, the drawdown mechanism of light particles in stirred tank is studied in this paper. For both up and down pumping modes, the just drawdown speeds(Njd) of floating particles in transformative Kanbara Reactor(KR) are measured in one and four baffled stirred tanks experimentally. Then numerical simulations with standard k-ε model coupled with volume of fluid model(VOF) and discrete phase model(DPM) are conducted to analyze the flow field at the just drawdown speed Njd. The torques on the impeller obtained from experiments and simulations agree well with each other, which indicates the validity of our numerical simulations. Based on the simulations, three main drawdown mechanisms for floating particles, the axial circulation, turbulent fluctuation and largescale eddies, are analyzed. It's found that the axial circulation dominates the drawdown process at small submergence(S = 1/4 T and 1/3 T) and the large-scale eddies play a major role at large submergence(S = 2/3 T and 3/4 T). Besides, the turbulent fluctuation affects the drawdown process significantly for up pumping mode at small submergence(S = 1/4 T and 1/3 T) and for down pumping mode at large submergence(S = 2/3 T and 3/4 T). This paper helps to provide a more comprehensive understanding of the KR desulphurizer drawdown process in the baffled stirred tank.展开更多
Computational fluid dynamics-discrete element method(CFD-DEM) coupled approach was employed to simulate the solid suspension behavior in a Rushton stirred tank with consideration of transitional and rotational motions...Computational fluid dynamics-discrete element method(CFD-DEM) coupled approach was employed to simulate the solid suspension behavior in a Rushton stirred tank with consideration of transitional and rotational motions of millions of particles with complex interactions with liquid and the rotating impeller. The simulations were satisfactorily validated with experimental data in literature in terms of measured particle velocities in the tank.Influences of operating conditions and physical properties of particles(i.e., particle diameter and density) on the two-phase flow field in the stirred tank involving particle distribution, particle velocity and vortex were studied.The wide distribution of particle angular velocity ranging from 0 to 105r·min 1is revealed. The Magnus force is comparable to the drag force during the particle movement in the tank. The strong particle rotation will generate extra shear force on the particles so that the particle morphology may be affected, especially in the bio-/polymer-product related processes. It can be concluded that the CFD-DEM coupled approach provides a theoretical way to understand the physics of particle movement in micro- to macro-scales in the solid suspension of a stirred tank.展开更多
To reduce the power consumption and improve the mixing performance in stirred tanks,two improved disc turbines namely swept-back parabolic disc turbine(SPDT)and staggered fan-shaped parabolic disc turbine(SFPDT)are de...To reduce the power consumption and improve the mixing performance in stirred tanks,two improved disc turbines namely swept-back parabolic disc turbine(SPDT)and staggered fan-shaped parabolic disc turbine(SFPDT)are developed.After validation of computational fluid dynamics(CFD)model with experimental results,CFD simulations are carried out to study the flow pattern,mean velocity,power consumption,pumping capacity and mixing efficiency of the improved and traditional impellers in a dished-bottom tank under turbulent flow conditions,The results indicate that compared with the commonly used parabolic disc turbine(PDT),the power number of proposed SPDT and SFPDT impellers is reduced by 43%and 12%,and the pumping efficiency is increased by 68%and 13%,respectively.Furthermore,under the same power consumption(0-700 W·m^(-3)),the mixing performance of both SPDT and SFPDT is also superior to that of Rushton turbine and PDT.展开更多
In this study, the large eddy simulation technique was applied on the flow in a baffled stirred tank driven by a Rushton turbine at Re=29000. The interaction between the rotating impeller and the static baffles was ac...In this study, the large eddy simulation technique was applied on the flow in a baffled stirred tank driven by a Rushton turbine at Re=29000. The interaction between the rotating impeller and the static baffles was accounted for by means of the improved inner-outer iterative algorithm. The sub-grid scale model was a conventional Smagorinsky model. The numerical solution of the governing equations was conducted in a cylindrical staggered grid. The momentum and the continuity equations were discretized using the finite difference method, with a third-order QUICK scheme used for convective terms. The phase-resolved predictions were compared with the experimental data of Wu and Patterson and good agreement was observed for both the mean and the turbulence quantities. They were much better than the Reynolds-averaged Navier-Stokes model including the Reynolds Stress Model for simulating the turbulence. The study also suggests the feasibility of LES in combination with the improved inner-outer iterative algorithm for the simulation of turbulent flow in stirred tanks.展开更多
Ultra fine grinding of the plant tailings of a refractory silver ore was studied using a laboratory type vertical stirred media mill. Preliminary tests confirmed that ultra fine grinding substantially improves the ext...Ultra fine grinding of the plant tailings of a refractory silver ore was studied using a laboratory type vertical stirred media mill. Preliminary tests confirmed that ultra fine grinding substantially improves the extraction of silver from the tailings in cyanide leaching （i.e. 36% Ag extraction rate from the as-received tailings with d80 of 100 μm, c.f. 84% extraction rate after ultra fine grinding of the tailings with ds0 of 1.2 pro）. In the ultra fine grinding tests, the effects of ball diameter （2-4.5 mm）, stirring speed （200-800 r/m/n） and ball charge ratio （50%-80%） on the fineness of grind （ds0, ~tm） were investigated through a Box-Behnken design. Increasing stirrer speed and ball charge ratio decreased fineness of grind while larger balls resulted in the coarser products. The tests demonstrated that a fineness of grind less than 5 μm can be achieved under suitable conditions. Analysis of stress intensity indicated an optimum range of stress intensity of （0.8-2）× 10^- 3 μm for all power inputs.展开更多
Gas holdups in ambient gassed and hot sparged systems with multiple modern impellers and the effect of temperature on gas holdup are reported. The operating temperature has a great impact on gas holdup though the gas ...Gas holdups in ambient gassed and hot sparged systems with multiple modern impellers and the effect of temperature on gas holdup are reported. The operating temperature has a great impact on gas holdup though the gas dispersion regime in the hot sparged system is similar to the ambient gassed condition. The gas holdup under the elevated temperature and the ambient gassed operation is successfully correlated. With the same total gas flow rate and power input, the gas holdup in the hot sparged system (say near the boiling point) is only about half of that in the ambient system. The results imply that almost all existing hot sparged reactors have been designed on the basis of incorrect estimates of the gas holdup during operation.展开更多
In this paper, particle image velocimetry (PIV) was used to measure the mean and root meansquare(RMS) velocity in the stirred tank with six-flat blade Rushton turbine and with no baffles. Two typesof motion patterns w...In this paper, particle image velocimetry (PIV) was used to measure the mean and root meansquare(RMS) velocity in the stirred tank with six-flat blade Rushton turbine and with no baffles. Two typesof motion patterns were studied. One was that the impeller runs at constant speed, the other was that the impellerruns at time-dependent speed and in a periodic way. The emphasis of the paper was on the comparison of meanand RMS velocity vector maps and profiles between these two types of motion patterns, and especial attention waspaid to the comparison of the mean velocity, time-averaged RMS velocity, phase averaged RMS velocity betweenthe constant 3 RPS (revolution per second) and time-dependent operation. The Reynolds number was between 763and 1527. The study explained the mechanism that time-dependent RPS is more efficient for mixing than that ofconstant RPS.展开更多
The spatial structure of the velocity field in a stirred vessel with water has been measured and analyzed using the laser Doppler velocimeter technique, with the immersing depth and agitation speed of the impeller re-...The spatial structure of the velocity field in a stirred vessel with water has been measured and analyzed using the laser Doppler velocimeter technique, with the immersing depth and agitation speed of the impeller re-maining approximately constant. The experimental results were provided such as the mean velocity field, fluctuat-ing velocities, turbulent kinetic energy, Reynolds shear stress and time series of the velocity in the stirred tank. These results probably provided the valuable basis to further optimize and enlarge the stirred tank in the industrial process.展开更多
Based on Fluent software,the gas−liquid two-phase flow in the horizontal stirred tank was simulated with SST k−ωturbulence model,Eulerian−Eulerian two-fluid model,and multi-reference flame method.The mixing process i...Based on Fluent software,the gas−liquid two-phase flow in the horizontal stirred tank was simulated with SST k−ωturbulence model,Eulerian−Eulerian two-fluid model,and multi-reference flame method.The mixing process in the tank was calculated by tracer method.The results show that increasing the rotating speed or gas flow is conducive to a more uniform distribution of the gas phase and accelerates the mixing of the liquid phase.When the rotating speed exceeds 93 r/min,the relative power demand remains basically constant.The change in the inclination angle of the upper impeller has minimal effect on the gas phase distribution.When the inclination angle is 50°,the relative power demand reaches the maximum.An appropriate increase in the impeller distance from the bottom improves the gas holdup and gas phase distribution but increases the liquid phase mixing time.展开更多
The discrete particle method was used to simulate the distribution of gas holdup in a gas-liquid standard Rushton stirred tank. The gas phase was treated as a large number of bubbles and their trajectories were tracke...The discrete particle method was used to simulate the distribution of gas holdup in a gas-liquid standard Rushton stirred tank. The gas phase was treated as a large number of bubbles and their trajectories were tracked with the results of motion equations. The two-way approach was performed to couple the interphase momentum exchange. The turbulent dispersion of bubbles with a size distribution was modeled using a stochastic tracking model, and the added mass force was involved to account for the effect of bubble acceleration on the surrounding fluid. The predicted gas holdup distribution showed that this method could give reasonable prediction comparable to the reported experimental data when the effect of turbulence was took into account in modification for drag coefficient.展开更多
基金support from the National Key Research and Development Program of China,China(2023YFE0106600)the National Natural Science Foundation of China,China(22421003,22178354,21925805)funding from FFG(Austria)under project“ABATE”(903872).
文摘Liquid-liquid dispersion is often performed in stirred tanks,which are valued for their ease of operation,high droplet generation rate and effective droplet dispersion.Many relevant simulations use the Eulerian-Eulerian method,combining population balance equations with statistical models to forecast droplet breakage.Conversely,the Eulerian-Lagrangian(E-L)method provides precise tracking of individual droplets,which is crucial for simulating dispersion processes.However,E-L simulation faces challenges in integrating droplet breakage effectively.To address this issue,our research introduces a probabilistic approach for droplet breakages.It assumes that a longer time increases the likelihood of breakup;a droplet breaks if the calculated probability exceeds a random value from 0 to 1.Consequently,the simulated breakage frequency becomes independent of the Lagrangian time step.The Sauter mean diameter and droplet size distribution can be accurately predicted by this probabilistic approach.By closely monitoring droplet motion,we reveal the complexity of droplet trajectories and the detailed patterns of circulation in stirred tanks.These insights contribute to a deeper understanding of liquidliquid dispersion dynamics.
基金the financial support from the National Natural Science Foundation of China(22078058)。
文摘Fractal theory provides a new strategy for equipment design.In this work,we propose a novel H-like fractal(HLF)impeller to improve the uniformity of the distribution of hydrodynamics in stirred tanks.The impellers are constructed by replacing two vertical blades or four legs with two or four H-like subblades by fractal iterations,respectively.Flow characteristics including velocity and turbulent kinetic energy(TKE)distributions,vortices,power number,are predicted by large eddy simulation.Compared with Rushton turbine(RT)impeller when H/T=1(or dual RTs when H/T=1.5,triple RTs when H/T=2),the HLF impeller can produce a flow field with more uniform distributions of larger velocities and TKE level.The impeller with more fractal iteration times can further improve the distribution uniformity of hydrodynamics in the case of high H/T.Power analysis shows that this is mainly due to the improved energy utilization efficiency by the fractal structure design.
基金the National Natural Science Foundation of China(22078030)the National Key Research and Development Project(2019YFC1905802,2022YFB3504305)+1 种基金the Joint Funds of the National Natural Science Foundation of China(U1802255,CSTB2022NSCQ-LZX0014)the Key Project of Independent Research Project of State Key Laboratory of Coal Mine Disaster Dynamics and Control(2011DA105287-zd201902).
文摘Leveraging big data signal processing offers a pathway to the development of artificial intelligencedriven equipment.The analysis of fluid flow signals and the characterization of fluid flow behavior are of critical in two-phase flow studies.Significant research efforts have focused on discerning flow regimes using various signal analysis methods.In this review,recent advances in time series signals analysis algorithms for stirred tank reactors have been summarized,and the detailed methodologies are categorized into the frequency domain methods,time-frequency domain methods,and state space methods.The strengths,limitations,and notable findings of each algorithm are highlighted.Additionally,the interrelationships between these methodologies have also been discussed,as well as the present progress achieved in various applications.Future research directions and challenges are also predicted to provide an overview of current research trends in data mining of time series for analyzing flow regimes and chaotic signals.This review offers a comprehensive summary for extracting and characterizing fluid flow behavior and serves as a theoretical reference for optimizing the characterization of chaotic signals in future research endeavors.
基金supported by the National Natural Science Foundation of China(22494713,22178160,22327809 and 22208141)Natural Science Foundation of Jiangsu Province,China(BK20220349).
文摘The structural and operational optimization of gas-liquid stirred bioreactors presents both complexity and critical importance for enhancing mass transfer performance. This study proposes a machine learning (ML)-driven approach to identify key features and predict the volumetric mass transfer coefficient (kLa). Four ML models were adopted and compared for kLa prediction in Newtonian and non-Newtonian fluids by evaluative indices, with CatBoost and XGBoost emerging as the optimal models, respectively. Specifically, it is demonstrated that Catboost has higher prediction accuracy (AARD = 18.84%) than empirical equations by effectively incorporating multidimensional features (structural, impeller, and operational), while simultaneously extending applicability to diverse Newtonian fluids. For non-Newtonian fluids, XGBoost outperforms empirical equations by effectively incorporating fluid rheological parameters (consistency coefficient, power-law index), thereby better capturing shear-thinning behavior. Feature importance analysis further identified rotational speed (for Newtonian fluids) and liquid height (for non-Newtonian fluids) as the key features, while 2D partial dependence analysis establishes quantitative optimization ranges. This ML approach provides an efficient predictive tool for gas-liquid stirred bioreactor design and optimization.
基金Projects(50974035,51074047)supported by the National Natural Science Foundation of ChinaProject(2010AA03A405)supported by the High-tech Research and Development Program of China
文摘The improved Intermig impeller has been used in the seed precipitation tank in China, which could enhance the mixing and suspension of Al(OH)3 particles and the power consumption declined largely. The flow field, solids hold-up, cloud height, just off-bottom speed and power consumptions were investigated in solid-liquid mixing system with this new type of impeller by CFD and water experiment methods. Compared with the standard Intermig impeller, the improved one coupled with specially sloped baffles could promote the fluid circulation, create better solids suspension and consume less power. Besides lower impeller off-bottom clearance is good for solid suspension and distribution. The just-off-bottom speed was also determined by a power number criterion. Meanwhile, the predicted results were in good agreement with the experimental data.
文摘[Objective] In this study, the aim was to study the optimal formula and technique of honey stirred yoghurt. [Method] The optimum formula and production technique of the honey stirred yoghurt were confirmed by studying the effects of the additive amount of honey, the adding time of honey, thermal death point, the ho- mogenization pressure and stability test on the sensory quality of stirred yoghurt. [Result] The experiment showed that the fermentation temperature of the honey stirred yoghurt should not be too high, and it should be close to that of common yoghurt. In addition, the fermentation time should not be too long, because along with the extension of fermentation time, there would be abnormal smell in the yo- gurt. The optimum formula and production technique were as follows： the additive amount of honey, sugarcane and fermentation agent was respectively 3%; two-sec- tion homogeneous pressures of the fresh milk were I ： 70 MPa, I1：30 MPa; the thermal death point was 85 ℃ and the time was 10 min; the fermentation occurred at 42℃, and the fermentation of the products was stopped when the ultimate acidity was among 0.70%-0.75%. [Conclusion] The study could provide some refer- ences for the production and processing of honey stirred yoghurt.
文摘Research shows that producing fermented camel milk is hard because of the milk’s inability to form a firm coagulum, attributed to low levels of κ-casein and ꞵ-lactoglobulin and the large casein micelle size, leading to a weak network of casein formation. In an effort to address this issue, researchers turned to corn starch as a thickening agent, discovering that a concentration of 2.0% effectively improved the viscosity and significantly reduced syneresis in stirred camel milk yoghurt and cultured camel milk. This study explores alternatives to corn starch, focusing on butternut squash seeds as a promising substitute due to their hydrocolloid composition. By incorporating butternut squash (Cucurbita moschata) seed powder (BSSP) as a thickening agent, this study aimed at enhancing the chemical and rheological properties of stirred camel milk yoghurt and cultured camel milk. Fermented camel milk was prepared using 4 litres of camel milk, 2% starter cultures (thermophilic culture for yoghurt and mesophilic aromatic culture for stirred cultured camel milk) and BSSP 0.0% (negative control), 0.4%, 0.8%, 1.2%, 1.6%, 2.0% mixed with 0.4% gelatin. 2.0% corn starch mixed with 0.4% gelatin was used as a standard for comparison. Results showed that increasing the BSSP level significantly (p < 0.05) decreased the moisture content while increasing the total solid content of stirred fermented camel milk products. There was an increase in ash content with an increase in BSSP levels. There was a significant (p < 0.05) reduction in the pH, with an increase in BSSP levels in stirred fermented camel milk samples. Increasing the concentration of BSSP from 0.4% to 2.0% resulted in a significant (p < 0.05) increase in viscosity and a reduction in syneresis of stirred camel milk yoghurt and stirred cultured camel milk samples. This study demonstrated that BSSP effectively enhances the viscosity, reduces syneresis and increases acidity in stirred fermented camel milk products during storage.
基金supported by the Fundamental Research Funds for the Central Universities (No. 2019XKQYMS45)。
文摘Physical upgrading of graphite is typically achieved with many stages of grinding and flotation to produce a concentrate with approximately 95% carbon grade.An innovative grinding and column flotation process has been developed for efficient graphite upgrading to substantially simplify the process flowsheet and reduce operating costs.In this process,a high-pressure grinding roller(HPGR) and a stirred mill were employed as primary comminution techniques and a nanobubble flotation column as a key separation process.The results obtained with a crystalline flake graphite sample with a carbon grade of 11.15% show that the novel process can produce a concentrate with 94.82% carbon grade and 97.89% recovery from an open circuit of one rougher and two cleaner flotation stages.Scanning electron microscope(SEM)microphotographs indicate that HPGR offers the advantage of more effective protection of graphite flakes during crushing.Grinding test results show that stirred mill could not only protect graphite flakes but also promote the efficient liberation of graphite.Compared with the traditional flotation process,nanobubble flotation can effectively recover ultrafine graphite.The new process possesses a number of important advantages over the traditional method,including substantially higher graphite recovery,greatly simplified process flowsheet,better protection of flake size,reduced reagent consumption and process costs,etc.
基金the National Natural Science Foundation of China (No. 29792074) and SINOPEC.
文摘The gas-liquid flow field in a stirred tank with a Rushton diskturbine, including the impeller region, was numerically simulatedusing the improved inner-outer iterative procedure. Thecharacteristic features of the stirred tank, such as gas cavity andaccumulation of gas at the two sides of wall baffles, can be capturedby the simulation. The simulated results agree well with availableexperimental data. Since the improved inner-outer iterative algorithmdemands on empirical formula and experimental data for the impellerregion, and the approach seems generally applicable for simulatinggas-liquid stirred tanks.
基金Supported by the National Natural Science Foundation of China (Nos.20236050, 50134020) and the Special Funds for Major State Basic Research Program of China (973 Program, 2004CB217604).
文摘The effect of mixing on the precipitation of barium sulfate in a continuous stirred tank is simulated numerically with different feeding location, feed concentration, impeller speed and residence time through solving the standard momentum and mass transport equations in combination with the moment equations for crystal population balance. The numerical method was validated with the literature data. The simulation results including the distribution of the local supersaturation ratio distribution in the precipitator, mean crystal size and coefficient of variation under different operating conditions compared well with experimental data in the literature. The effect of the presence of a draft tube on precipitation were also investigated, and it is suggested that the installation of a draft tube increased the mean crystal size, in general agreement with experimental work in the literature.
基金Supported by the National Natural Science Foundation of China(51474109,51609090,51679097)the Science Research Project of Huazhong University of Science and Technology(0118140077,2006140115)
文摘To improve the efficiency of the desulfurization process, the drawdown mechanism of light particles in stirred tank is studied in this paper. For both up and down pumping modes, the just drawdown speeds(Njd) of floating particles in transformative Kanbara Reactor(KR) are measured in one and four baffled stirred tanks experimentally. Then numerical simulations with standard k-ε model coupled with volume of fluid model(VOF) and discrete phase model(DPM) are conducted to analyze the flow field at the just drawdown speed Njd. The torques on the impeller obtained from experiments and simulations agree well with each other, which indicates the validity of our numerical simulations. Based on the simulations, three main drawdown mechanisms for floating particles, the axial circulation, turbulent fluctuation and largescale eddies, are analyzed. It's found that the axial circulation dominates the drawdown process at small submergence(S = 1/4 T and 1/3 T) and the large-scale eddies play a major role at large submergence(S = 2/3 T and 3/4 T). Besides, the turbulent fluctuation affects the drawdown process significantly for up pumping mode at small submergence(S = 1/4 T and 1/3 T) and for down pumping mode at large submergence(S = 2/3 T and 3/4 T). This paper helps to provide a more comprehensive understanding of the KR desulphurizer drawdown process in the baffled stirred tank.
基金Supported by the State Key Development Program for Basic Research of China （2013CB733600）, the National Natural Science Foundation of China （21036003, 20776074） and the Specialized Research Fund for the Doctoral Program of Higher Education of China （20090002110069）.
文摘Computational fluid dynamics-discrete element method(CFD-DEM) coupled approach was employed to simulate the solid suspension behavior in a Rushton stirred tank with consideration of transitional and rotational motions of millions of particles with complex interactions with liquid and the rotating impeller. The simulations were satisfactorily validated with experimental data in literature in terms of measured particle velocities in the tank.Influences of operating conditions and physical properties of particles(i.e., particle diameter and density) on the two-phase flow field in the stirred tank involving particle distribution, particle velocity and vortex were studied.The wide distribution of particle angular velocity ranging from 0 to 105r·min 1is revealed. The Magnus force is comparable to the drag force during the particle movement in the tank. The strong particle rotation will generate extra shear force on the particles so that the particle morphology may be affected, especially in the bio-/polymer-product related processes. It can be concluded that the CFD-DEM coupled approach provides a theoretical way to understand the physics of particle movement in micro- to macro-scales in the solid suspension of a stirred tank.
基金supported by the National Key Research and Development Program(2020YFA0906800)the National Natural Science Foundation of China(22078325,21938009)+3 种基金the NSFC-EU project(31961133018)the Special Project of Strategic Leading Science and Technology CAS(XDC06010302)Chemistry and Chemical Engineering Guangdong Laboratory,Shantou(No.1922006)the Li Foundation Fellow Program。
文摘To reduce the power consumption and improve the mixing performance in stirred tanks,two improved disc turbines namely swept-back parabolic disc turbine(SPDT)and staggered fan-shaped parabolic disc turbine(SFPDT)are developed.After validation of computational fluid dynamics(CFD)model with experimental results,CFD simulations are carried out to study the flow pattern,mean velocity,power consumption,pumping capacity and mixing efficiency of the improved and traditional impellers in a dished-bottom tank under turbulent flow conditions,The results indicate that compared with the commonly used parabolic disc turbine(PDT),the power number of proposed SPDT and SFPDT impellers is reduced by 43%and 12%,and the pumping efficiency is increased by 68%and 13%,respectively.Furthermore,under the same power consumption(0-700 W·m^(-3)),the mixing performance of both SPDT and SFPDT is also superior to that of Rushton turbine and PDT.
基金Supported by the National Natural Science Foundation of China （No.20236050） and the State Key Development Program for Basic Research of China （No.2004CB217604）.
文摘In this study, the large eddy simulation technique was applied on the flow in a baffled stirred tank driven by a Rushton turbine at Re=29000. The interaction between the rotating impeller and the static baffles was accounted for by means of the improved inner-outer iterative algorithm. The sub-grid scale model was a conventional Smagorinsky model. The numerical solution of the governing equations was conducted in a cylindrical staggered grid. The momentum and the continuity equations were discretized using the finite difference method, with a third-order QUICK scheme used for convective terms. The phase-resolved predictions were compared with the experimental data of Wu and Patterson and good agreement was observed for both the mean and the turbulence quantities. They were much better than the Reynolds-averaged Navier-Stokes model including the Reynolds Stress Model for simulating the turbulence. The study also suggests the feasibility of LES in combination with the improved inner-outer iterative algorithm for the simulation of turbulent flow in stirred tanks.
文摘Ultra fine grinding of the plant tailings of a refractory silver ore was studied using a laboratory type vertical stirred media mill. Preliminary tests confirmed that ultra fine grinding substantially improves the extraction of silver from the tailings in cyanide leaching （i.e. 36% Ag extraction rate from the as-received tailings with d80 of 100 μm, c.f. 84% extraction rate after ultra fine grinding of the tailings with ds0 of 1.2 pro）. In the ultra fine grinding tests, the effects of ball diameter （2-4.5 mm）, stirring speed （200-800 r/m/n） and ball charge ratio （50%-80%） on the fineness of grind （ds0, ~tm） were investigated through a Box-Behnken design. Increasing stirrer speed and ball charge ratio decreased fineness of grind while larger balls resulted in the coarser products. The tests demonstrated that a fineness of grind less than 5 μm can be achieved under suitable conditions. Analysis of stress intensity indicated an optimum range of stress intensity of （0.8-2）× 10^- 3 μm for all power inputs.
文摘Gas holdups in ambient gassed and hot sparged systems with multiple modern impellers and the effect of temperature on gas holdup are reported. The operating temperature has a great impact on gas holdup though the gas dispersion regime in the hot sparged system is similar to the ambient gassed condition. The gas holdup under the elevated temperature and the ambient gassed operation is successfully correlated. With the same total gas flow rate and power input, the gas holdup in the hot sparged system (say near the boiling point) is only about half of that in the ambient system. The results imply that almost all existing hot sparged reactors have been designed on the basis of incorrect estimates of the gas holdup during operation.
文摘In this paper, particle image velocimetry (PIV) was used to measure the mean and root meansquare(RMS) velocity in the stirred tank with six-flat blade Rushton turbine and with no baffles. Two typesof motion patterns were studied. One was that the impeller runs at constant speed, the other was that the impellerruns at time-dependent speed and in a periodic way. The emphasis of the paper was on the comparison of meanand RMS velocity vector maps and profiles between these two types of motion patterns, and especial attention waspaid to the comparison of the mean velocity, time-averaged RMS velocity, phase averaged RMS velocity betweenthe constant 3 RPS (revolution per second) and time-dependent operation. The Reynolds number was between 763and 1527. The study explained the mechanism that time-dependent RPS is more efficient for mixing than that ofconstant RPS.
基金Supported by the Natural Science Foundation of Inner Mongolia (No.200408020715).
文摘The spatial structure of the velocity field in a stirred vessel with water has been measured and analyzed using the laser Doppler velocimeter technique, with the immersing depth and agitation speed of the impeller re-maining approximately constant. The experimental results were provided such as the mean velocity field, fluctuat-ing velocities, turbulent kinetic energy, Reynolds shear stress and time series of the velocity in the stirred tank. These results probably provided the valuable basis to further optimize and enlarge the stirred tank in the industrial process.
基金financially supported by the Fundamental Research Funds for the Central Universities of Central South University,China(No.2020zzts515)。
文摘Based on Fluent software,the gas−liquid two-phase flow in the horizontal stirred tank was simulated with SST k−ωturbulence model,Eulerian−Eulerian two-fluid model,and multi-reference flame method.The mixing process in the tank was calculated by tracer method.The results show that increasing the rotating speed or gas flow is conducive to a more uniform distribution of the gas phase and accelerates the mixing of the liquid phase.When the rotating speed exceeds 93 r/min,the relative power demand remains basically constant.The change in the inclination angle of the upper impeller has minimal effect on the gas phase distribution.When the inclination angle is 50°,the relative power demand reaches the maximum.An appropriate increase in the impeller distance from the bottom improves the gas holdup and gas phase distribution but increases the liquid phase mixing time.
基金Supported by the National Natural Science Foundation of China （No.20776121） and the Specialized Research Fund for the Doctoral Program of Higher Education （No.20050530001）, and the Scientific Research Fund of Hunan Provincial Education Department （No.07C765）.
文摘The discrete particle method was used to simulate the distribution of gas holdup in a gas-liquid standard Rushton stirred tank. The gas phase was treated as a large number of bubbles and their trajectories were tracked with the results of motion equations. The two-way approach was performed to couple the interphase momentum exchange. The turbulent dispersion of bubbles with a size distribution was modeled using a stochastic tracking model, and the added mass force was involved to account for the effect of bubble acceleration on the surrounding fluid. The predicted gas holdup distribution showed that this method could give reasonable prediction comparable to the reported experimental data when the effect of turbulence was took into account in modification for drag coefficient.
