| Propeller agitators are widely used in petroleum,chemical,metallurgy and other industrial production.For example,in the process of crude potassium purification,propeller agitators are often used to fully mix the crude potassium ore pulp,so as to avoid the deposition of crude potassium at the bottom of the container,so that the crude potassium ore pulp can be evenly mixed,and a small amount of sodium chloride attached to the crude potassium can be fully dissolved in the ore pulp.At present,the propeller agitators designed by domestic agitator manufacturers according to the na-tional standard manual and previous experience have poor mixing effect and can’t meet the mixing requirements.To improve the efficiency of the propeller agitator,Taking a three-blade sinistral type propeller agitator(TXL1500-85)with a blade di-ameter of 1500mm and a rotating speed of 85r/min designed by a factory as the re-search object,the structural parameters of the agitator were optimized and the crude potassium mineral solution was used as the stirring medium,using Multiple reference frame method,Eulerian model and Standard k-ε model to numerical simulation of ag-itator TXL1500-85,analyzed the TXL1500-85 agitator installation location,helical Angle and rotating speed of blade flow law of internal flow field of the tank and the influence of solid liquid mixed performance,the optimum structural parameters of the agitator were obtained,which provided a theoretical basis for the installation form of the propeller agitator and the optimization of the blade structure.The main research contents are as follows:1.The original blade installation height 1350 mm from the bottom and other four kinds of blade from the bottom of the installation height of 1150,1500,1650,1800 mm is compared,by numerical simulation methods to analyze different blade TXL1500-85 from the bottom mounting height of the agitator flow field distribution,crude potassium volume fraction distribution,crude potassium concentration standard deviation and power consumption were used to determine the mixing efficiency of crude potassium ore pulp.Study found that with the increase of blade from bottom height,tank crude potassium concentration distribution uniform gradually,but the tank bottom particle deposition is aggravating,the stirring power change is not obvi-ous,the most powerful and minimum power by only 2.8%,when the blade height is 1500 mm from the bottom,namely the 1/3 of tank diameter,minimum power,the concentration of standard deviation of σ value was 0.45,compared with the other four highly value minimum,crude potassium suspension more even,the minimum energy consumption,mixer performance improved.2.In order to further optimize the flow field structure,improve the efficiency of mixing,based on the best from the bottom of the installation height,studies the TXL1500-85 mixer in eccentricity e respectively 0,0.1,0.2,0.3,0.4,the flow field under the condition of distribution and the effects of the thick liquid potash mixed results show that the power increases with the increase of eccentricity.Eccentric stir-ring can reduce the crude potassium particles deposited on the bottom of the stirring tank,but too much eccentricity will result in uneven mixing of coarse potassium on the non-eccentric side.When the eccentricity rate is 0.2,the axial velocity of the flow field is the largest,which is about 2.67 times that of the central agitation.The depo-sition of crude potassium at the bottom of the tank is greatly reduced,and the standard deviation of the concentration of crude potassium is the smallest compared with other eccentricity rates,which is about 0.71 times that of the central agitation.The uniform suspension of crude potassium results in the best mixing effect and relatively small power consumption.3.Based on the optimal installation height and eccentricity of the blade from the bottom,the influence of the helical Angle of the TXL1500-85 agitator blade on the agitator flow field distribution and the agitator stirring performance was analyzed.Increasing helical Angle of blade can increase the concentration of crude potassium around blade.However,the power consumption of the agitator increases with the in-crease of the blade helical Angle.When the blade helical Angle were 74.77° and 77.02°,crude potassium concentration standard deviation value σ reduced 6%and 4.5%respectively compared to the original blade spiral Angle is 69.40°,power con-sumption is increased by 3.9%and 8.3%,respectively,by considering the crude po-tassium mixed effect and power consumption,the agitator performs best when helical Angle is 74.77°,the mixing effect of crude potassium ore pulp is better.4.When the helical Angle of the blade of TXL1500-85 propeller agitator is 74.77°,the numerical simulation analysis was carried out at the agitator speeds of 85r/min,90r/min,95r/min and 100r/min respectively.The results show that increasing the rotating speed can improve the distribution uniformity of the crude potassium concentration in the top area of the tank,and the power consumption also increases linearly with the increase of the rotating speed.When the rotating speed is 95r/min,the standard deviation of crude potassium concentration decreases by 20%compared with the speed of 85r/min,the distribution of crude potassium particles was nearly uniform suspension.However,when the speed of the agitator increased to 100r/min,the power consumption continued to increase,but the improvement of stirring effect was not obvious.Therefore,95r/min is the optimal speed of the agitator. |
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