Study On Structure Optimization And Solid-liquid Dispersion Mixing Performance Of Paddle Stirred Tank

Phosphoric acid is widely used in agriculture,food and chemical industry and is the main raw material of a variety of chemical products.Wet process phosphoric acid production process is the main method used in phosphoric acid production at present,phosphoric acid stirred kettle is one of the key equipment in the production process.Phosphoric acid agitator is a typical paddle agitator,which is driven by a motor to rotate the stirring shaft and the agitator in the fluid of the kettle,so as to achieve the purpose of even mixing of phosphoric acid and phosphogypsum.When the solid-liquid mixing effect in the stirred tank of phosphoric acid is not ideal,the phosphogypsum particles will deposit and scale in the bottom of the stirred tank,which will affect the production efficiency.Therefore,it is necessary to optimize the structure of stirred tank.(1)In this paper,the original stirred tank was modeled,the computational fluid domain was extracted and meshed.Then the grid file is imported into the solver for parameter setting,and the appropriate turbulence model and multiphase flow model are selected for numerical simulation.In order to reduce the influence of the number of grids on the simulation results,different numbers of grids are used to analyze the grid independence of the stirred tank model.(2)Through the numerical simulation of the fluid in the stirred tank,the effects of different blade angle,diameter,number,structure,installation height from the bottom and rotating speed on the fluid velocity field and solid holdup were explored,and the appropriate parameters were selected to optimize the original stirred tank.The results show that: the blade angle mainly affects the range of circulating fluid around the blade;the blade diameter mainly affects the maximum fluid velocity at both ends of the blade,and when the diameter is too large,there will be a "cavity" area under the blade;the number of blades mainly changes the flow pattern above the impeller;the double-layer impeller structure can effectively improve the "funnel" area with poor mixing effect;the installation height from the bottom is the main factor Changing the center position of circulating fluid at both ends of the blade;stirring speed mainly affects the fluid velocity in the kettle.(3)The structure of the stirred tank was optimized.When the blade angle is 30°,the diameter is 90 cm,the number is 4,the installation height from the bottom is80 cm,and the rotation speed is 75 rpm,the solid-liquid two-phase mixing effect can be effectively improved under the condition of reasonable energy consumption.The results of this paper have a certain reference value for the structure optimization of phosphoric acid agitator.