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 di...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.展开更多
Gas-solid fluidized bed separation is a highly efficient and clean technique for coal separation,and can effectively remove ash and sulfur contained gangue minerals from coal.However,the fine coal plugging distributor...Gas-solid fluidized bed separation is a highly efficient and clean technique for coal separation,and can effectively remove ash and sulfur contained gangue minerals from coal.However,the fine coal plugging distributor often leads to uneven fluidization and affects the separation effect.In this paper,different plugging ways were designed to study their effects on the fluidization characteristics and particle mixing.It was found that when the plugging phenomenon occurs,the minimum fluidization velocity of the fluidized bed gradually decreases as the plugging area enlarges.The difference between the top and the bottom of the bed minimum fluidization velocity increases accordingly,and a“stagnation phenomenon”occurs in the bed.The standard deviation of pressure fluctuations at the top of the bed is smaller than that at the bottom of the bed,which is the opposite of normal conditions.As the area of the plugging increases,the dead zone on the side wall of the fluidized bed significantly increases.The size of the dead zone is rapid reducing at the initial stage.It was noticed that the stratification of the low-density products is particularly affected by plugging,whereas the stratification of high-density products is not obviously influenced by certain conditions.展开更多
Experimental fluidization results were compared for three gas distributors with the same opening ratio but different orifice in clinations (30,45 , and 90 ). Hydrodynamic studies were con ducted with glass beads (diam...Experimental fluidization results were compared for three gas distributors with the same opening ratio but different orifice in clinations (30,45 , and 90 ). Hydrodynamic studies were con ducted with glass beads (diameter 154p.m) to evaluate the impacts of orifice inclination and static bed depth on pressure drop, pressure drop fluctuations, bed expansion, and minimum fluidization velocity. Solids residence time distributions were determined using phosphoresce nt tracer particles (mea n diameter 76 pm), activated by ultraviolet light. The bed pressure drop was higher with the inclined-hole distributors and increased with static bed height. In a shallow bed, the inclined-hole distributors gave less expansion;however, in deep beds, the orifice angle had negligible influence on bed expansion. The minimum fluidization velocity varied with static bed height for the inclined-hole distributors and was higher for steeper angles. The turnover time estimated using bubbling-bed equations matched the experimental results well for vertical mixing. Probes and ports at the walls of the fluidization column reduced the dense-phase downward velocity by up to 40%. The tangential particle velocity was highest for the 30 -hole distributor and decreased with increasing orifice angle. Tangential mixing was described by a dispersion model;the dispersion coefficient for the inclined-hole distributors was approximately twice that for the 90 -hole distributor in a shallow bed.展开更多
The mechanism of liquid phase back-mixing in the liquid-solid fluidized bed has been studied.The radial parabolic distribution of liquid velocity is found to be the main motivation of particles’circulating movement w...The mechanism of liquid phase back-mixing in the liquid-solid fluidized bed has been studied.The radial parabolic distribution of liquid velocity is found to be the main motivation of particles’circulating movement which in trun causes the liquid back-mixing.The liquid back-mixing can be reduced by evening the radial distribution of liquid velocity.This is achieved by a hetero-pores distributor which has a resistant coefficient distribution analogous to that of liquid velocity.The experimental result shows that the hetero-pores distributor reduces the liquid back- mixing effectively.展开更多
基金financially supported by the National Natural Science Foundation of China (22090034, 21776179)the Major Science and Technology Project of Xinjiang Bingtuan(2020AA004)the Major Project of Shihezi City(2020ZD002)
文摘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.
基金the National Natural Science Foundation of China-Xinjiang Joint Foundation(No.U1903132)National Natural Science Foundation of China(No.51904298).
文摘Gas-solid fluidized bed separation is a highly efficient and clean technique for coal separation,and can effectively remove ash and sulfur contained gangue minerals from coal.However,the fine coal plugging distributor often leads to uneven fluidization and affects the separation effect.In this paper,different plugging ways were designed to study their effects on the fluidization characteristics and particle mixing.It was found that when the plugging phenomenon occurs,the minimum fluidization velocity of the fluidized bed gradually decreases as the plugging area enlarges.The difference between the top and the bottom of the bed minimum fluidization velocity increases accordingly,and a“stagnation phenomenon”occurs in the bed.The standard deviation of pressure fluctuations at the top of the bed is smaller than that at the bottom of the bed,which is the opposite of normal conditions.As the area of the plugging increases,the dead zone on the side wall of the fluidized bed significantly increases.The size of the dead zone is rapid reducing at the initial stage.It was noticed that the stratification of the low-density products is particularly affected by plugging,whereas the stratification of high-density products is not obviously influenced by certain conditions.
文摘Experimental fluidization results were compared for three gas distributors with the same opening ratio but different orifice in clinations (30,45 , and 90 ). Hydrodynamic studies were con ducted with glass beads (diameter 154p.m) to evaluate the impacts of orifice inclination and static bed depth on pressure drop, pressure drop fluctuations, bed expansion, and minimum fluidization velocity. Solids residence time distributions were determined using phosphoresce nt tracer particles (mea n diameter 76 pm), activated by ultraviolet light. The bed pressure drop was higher with the inclined-hole distributors and increased with static bed height. In a shallow bed, the inclined-hole distributors gave less expansion;however, in deep beds, the orifice angle had negligible influence on bed expansion. The minimum fluidization velocity varied with static bed height for the inclined-hole distributors and was higher for steeper angles. The turnover time estimated using bubbling-bed equations matched the experimental results well for vertical mixing. Probes and ports at the walls of the fluidization column reduced the dense-phase downward velocity by up to 40%. The tangential particle velocity was highest for the 30 -hole distributor and decreased with increasing orifice angle. Tangential mixing was described by a dispersion model;the dispersion coefficient for the inclined-hole distributors was approximately twice that for the 90 -hole distributor in a shallow bed.
文摘The mechanism of liquid phase back-mixing in the liquid-solid fluidized bed has been studied.The radial parabolic distribution of liquid velocity is found to be the main motivation of particles’circulating movement which in trun causes the liquid back-mixing.The liquid back-mixing can be reduced by evening the radial distribution of liquid velocity.This is achieved by a hetero-pores distributor which has a resistant coefficient distribution analogous to that of liquid velocity.The experimental result shows that the hetero-pores distributor reduces the liquid back- mixing effectively.
