Research Of New High Efficient Clarification And Extraction Tank With Double Stirring Mode

The mixer-settler is a core device of solvent extraction for separating rare earth elements.The volume ratio between single-stage settler and mixer in China's rare earth industry is generally above 2.5:1.The mismatching of two-phase separation rate and mixing extraction rate leads to rare earth accumulation and poor production efficiency,which has become a bottleneck inthe rare earth industry.Current researches usually focus on changing the structure of the mixer-settler without making a breakthrough towards gravity clarification.Therefore,this paper puts forward a new concept "mechanical stirring demulsification" and a new type of high efficient clarification and extraction tank with double stirring mode is designed and manufactured,involving the insertion of a stirring device in the settler after reducing it's a half volume at least.Shearing action will accelerate the droplet movement and deformation,increase the droplet collision probability and extend droplet trajectory to the aggregated into larger droplets,so as to achieve the purpose of demulsification and improve oil-water two-phase separation rate.First of all,the effect of stirring speed on the water content and droplet size distribution of oil-water system was studied in this paper under different sampling position and stirring time in the mixer of high efficient clarification and extraction tank with double stirring mode.Experimental results show that when the stirring speed is 100-400r/min,the water content is different at different locations,and the phenomenon is not improved with time.When the stirring speed is 500-800r/min,the water content at different position is slightly different and the mixing is uniform after stirring 5min.When the stirring speed is 100-200r/min,the droplet diameters are between 10?m and 240?m,and the Sauter mean diameters are very different.When the stirring speed is 300-500r/min,droplet diameters distribution are gradually decreased from 115?m to 70?m below,and the Sauter mean diameters are gradually decreased.When the stirring speed is greater than 600r/min,the droplet diameters are mainly distributed below 45?m,and the Sauter mean diameters are below 33?m when the stirring time is 5min.The second,the innovation of this research involved adopting the Karl-Fischer method and ultraviolet-visible spectrophotometry to investigate the influence of the stirring speed on enhanced separation effect under different conditions in the settler of high efficient clarification and extraction tank with double stirring mode.Experimental results show that stirring has the effect of accelerating separation.When the distance from paddle to overflow port is 10cm,the height from the bottom is 7cm or 15cm,the minimum of oil phase entrainment is 1.25%.When the distance from paddle to overflow port is 12.5cm,the height from the bottom is 7cm,the minimum of aqueous phase entrainment is 0.07%.When oil phase entrainment is reduced to 1%,the time of stirring separation is less than static separation by 0.5min.The concentration of aqueous phase has little effect on the final clarification effect,and the increase of the experimental temperature is beneficial to the oil-water.separation.In three-stage high efficient clarification and extraction tank with double stirring mode,the minimum of oil phase entrainment is 0.49%,and the minimum of aqueous phase entrainment is 0.09%.The average value of oil phase entrainment is 0.62%and the average value of aqueous phase entrainment is 0.06%in three-stage magnified high efficient clarification and extraction tank with double stirring mode,which are reduced by 30%and 88%compared to the average value of oil phase entrainment by 0.85%and the average value of aqueous phase entrainment by 0.5%in the traditional mixer-settler.And then,the criterion equation of Sauter mean diameter d32 under the experimental conditions was established by dimensional method,d32=0.008197nm-0.79693t:m-0.184h-0.09755,the calculated values agree well with the experimental values.The criterion equation of the oil phase entrainment under the experimental conditions was established:The calculated values agree well with the experimental values.Finally,the flow characteristics of single and three-stage magnified high efficient clarification and extraction tank with double stirring mode was simulated.Experimental results show that stirring has the effect of accelerating separation.The entrainment of the aqueous phase at the outlet is reduced to about 0.15%.and the equilibrium is maintained.In the settler without stirring,the corresponding aqueous phase entrainment is about 5%,which is much higher than the value in the settler with stirring.It further confirms that the stirring can strengthen the two-phase separation.The suitable operating conditions of the stirring separation are the stirring speed by10r/min,the height from the bottom by 10cm,aqueous phase inlet flow by 40L/h and oil phase inlet flow by 80L/h.The analysis of the impurity content at the outlet of three-stage magnified high efficient clarification and extraction tank with double stirring mode shows that adding the stirring device in the settler can effectively improve the separation efficiency.From the results of the flow field analysis,it can be known that two phases mix fully in the mixer when the stirring speed is 250r/min.The droplet is broken up,the reflux is effectively restrained at the outlet,and two-phase separation is accelerated by adding the stirring device in the settler.From the analysis of the power simulation results,it can be known that the power consumption of the settler is negligible when compared with the mixer,which is beneficial to promote the new type of mixer-settler with double stirring mode in the industry.In summary,the research and development of new high efficient clarification and extraction tank with double stirring mode based on the principle of mechanical stirring demulsification is an important exploration for the traditional extraction tank,clarify the extraction tank in the traditional hybrid clarifying tank is an important exploration.It has important theoretical and practical significance for the improvement and amplification of industrial equipment.