A numerical study of mixing intensification for highly viscous fluids in multistage rotor-stator mixers

How to achieve uniform mixing of highly viscous fluids with low energy consumption is a major industry demand and one of the hot spots of mixing research.A typical multistage rotor-stator mixer(MRSM)equipped with a distributor was investigated to disclose the effects on the mixing performance and power consumption for highly viscous fluids via numerical simulation,considering the influence factors associated with different geometric parameters of both MRSM and the distributor.The mixing index and power consumption are used to evaluate the performance of the mixers.The dimensionless correlations for the mixing index and the power consumption are established considering the factors including the flow rate,rotor speed,the number of mixing units.Adopting the optimized mixer with the distributor(X1-T1),the mixing index increases to 0.85(obviously higher than 0.46 for the mixer T1 without a distributor),meanwhile the corresponding power consumption is about 1/5 of that of T1 achieving the same mixing effect.It illustrates that the distributor can significantly improve the mixing of highly viscous fluids in the MRSM without the cost of large power consumption.These results would provide a guidance on the design and optimization of multistage rotor-stator mixers in industrial applications.

Gas Absorption and Mass Transfer in a Pore-Array Intensified Tube-in-Tube Microchannel

A pore-array intensified tube-in-tube microchannel(PA-TMC),which is characterized by high throughput and low pressure drop,was developed as a gas–liquid contactor.The sulfite oxidation method was used to determine the oxygen efficiency(φ)and volumetric mass transfer coefficient(k_(L)a)of PA-TMC,and the mass transfer amount per unit energy(ε)was calculated by using the pressure drop.The effects of structural and operating parameters were investigated systematically,and the twophase flow behavior was monitored by using a charge-coupled device imaging system.The results indicated that the gas absorption efficiency and mass transfer performance of the PA-TMC were improved with increasing pore number,flow rate,and number of helical coil turns and decreasing pore size,row number,annular size,annular length,and surface tension.Theφ,εand k La of PA-TMC could reach 31.3%,1.73×10^(-4) mol/J,and 7.0 s-1,respectively.The Sherwood number was correlated with the investigated parameters to guide the design of PA-TMC in gas absorption and mass transfer processes.

Effects of rotor and stator geometry on dissolution process and power consumption in jet-flow high shear mixers

The jet-flow high shear mixer(JF-HSM)is a new type of intensified equipment with special configurations of the rotor and the stator.The mass transfer property and power consumption were studied in the solid-liquid system for a series of JF-HSMs involving different configuration parameters,such as rotor diameter,rotor blade inclination,rotor blade bending direction,stator diameter,and stator bottom opening diameter.The flow characteristics were examined by computational fluid dynamic simulations.Results indicate that the turbulent power consumption of the JF-HSM is affected by the change in rotor blade inclination and stator bottom opening.With the increase in the shear head size and the change in the rotor into a backward-curved blade,the solid-liquid mass transfer rate can be remarkably increased under the same input power.Dimensionless correlations for the mass transfer coefficient and power consumption were obtained to guide the scale-up design and selection of such a new type of equipment to intensify the overall mixing efficiency.

Micromixing performance of the teethed high shear mixer under semi-batch operation

Semi-batch operated reaction processes are necessary for some competitive reaction systems to achieve a desirable process selectivity and productivity of fine chemical products.Herein the structural and operating parameters of the teethed high shear mixers were adjusted to study the micromixing performance in the semi-batch operated system,using the Villermaux/Dushman reaction system.The results indicate that the rising of the rotor speed and the number of rotor teeth,the decrease of the width of the shear gap and the radial distance between the feed position and the inner wall of stator can enhance the micromixing level and lead to the decrease of the segregation index.Additionally,computational fluid dynamics calculations were carried out to disclose the evolution of the flow pattern and turbulent energy dissipation rate of the semi-batch operated high shear mixer.Furthermore,the correlation was established with a mean relative error of 8.05%and R^(2)of 0.955 to fit the segregation index and the parameters studied in this work,which can provide valuable guidance on the design and optimization of the semi-batch operated high shear mixers in practical applications.