| Stirring and mixing is one of the most widely used process operations.In the operation of the stirring equipment,the controllable range of its operating conditions is relatively wide,the controllability is relatively good,and it can be applied in many industrial productions.Gas-liquid reaction is required in many process industries.The premise of gas-liquid reaction is that the gas and liquid are in a dispersed state.The gas dispersion is a crucial factor in gas-liquid mixing.In the mixing industry,especially in the gas-liquid stirring,the type of the domestic stirrer is relatively limited,and the selection is not reasonable enough.The difference between the usual structure and operating parameters and its optimum working condition is large,resulting in low production efficiency.In this paper,based on the traditional gas-liquid two-phase stirrer and the cavitation theory,the use of curved structure paddles to reduce the vortex on the back of the stirrer to suppress the formation of big cavitation,improve the performance of the stirrer,while adding long paddle structure and turbine disc to increase the residence time of the gas to invent a new stirrer for gas-liquid dispersion.The Fluent,the Euler-Euler model,the PBM model,and the standard k-?turbulence model are used.Numerical simulation was conducted to calculate the application of a new type stirrer in gas-liquid two-phase stirring process.In the process of comparative study between the new stirrer and the CD-6 impeller of the traditional stirrer,based on its working characteristics,three operating conditions and physical parameters of the material are given,from the flow field characteristics,stirring power characteristics,and the gas hold-up of these aspects of a comparative study.It was found that the new stirrer has enhanced radial flow during operation,the axial flow in the upper paddle region is enhanced,and the degree of turbulence in the entire kettle is high.After aeration,the stirring power decreases slightly,indicating that the new type stirrer has a stronger ability to transport gas.At the same time,the gas distribution of the new type agitator is more extensive and uniform,and the gas content is relatively high.On the whlie,the new stirrer is more conducive to gas dispersion and mass transfer between gas and liquid.In order to study the stirring characteristics of the new stirrer,the stirring characteristics of the new gas-liquid stirrer were studied from the four influencing factors in the operating parameters and structural characteristics,which were respectively five sets of speed of agitator of 6?7?8?9?10 rps.The four groups of ventilation were 61.0?101.7?142.4?183.1L·min-1.The five groups of installation heights were 90?110?130?150?170 mm.The four groups of long paddles were 50?100?150?200 mm in length.The results show that when the speed of agitator is 9 rps,the relative power consumption rises with the increase of the speed,the amplitude of the increase obviously decreases,tends to be stable and maintains at a higher value,guarantees the agitator's ability to transport gas,and the gas distribution range is wider and the gas hold-up rate is higher.When the ventilation is 101.7 L·min-1,the gas hold-up is ideally distributed.At the same time,the peak value is within a reasonable range.It does not form a large cavitation,which is beneficial to the dispersion of gas and liquid and the mass transfer between gas and liquid.When the installation height is 130mm and the length of the long paddle is 150mm,the overall turbulence level in the kettle is high,which further enhances the relative gas carrying capacity of the liquid,and the relative power consumption is maintained at a relatively high value.It shows that the gas has a stronger transport capacity and the gas distribution in the kettle is more extensive and uniform.Compared with other groups,the gas hold-up rate at the corresponding position is maintained within an ideal and relatively high range.The results of this study provide a new type of stirrer for the gas-liquid two-phase stirring process,which is of great significance. |
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