Research On The Mixing Performance For The Double Horizontal Ribbon Mixer On The Discrete Element Method

With the development of the society and the economy in China,the demand of the granular homogeneity is increasing in industry recently.The double horizontal ribbon mixer is one of the most important mixers with the excellent mixing performance and simple operation.This type of mixer has a relatively complex structure,and there is little literature on its mixing performance.In this paper,the effect of the operational and geometrical parameters on the mixing performance of the double horizontal ribbon mixer is studied by using the discrete element method(DEM).The thesis is organized as follows;Firstly,the mixing process of non-cohesive solid particles is simulated in the double horizontal ribbon mixer by DEM.The Lacey index is employed to evaluate the mixing efficiency of the particles in the mixer.The cell sizes for calculating the Lacey index is determined.The effects of the operational and geometrical parameters including initial loading(top-bottom,side-side,front-back),particle size,rotational speed of impeller and inner blades on the mixing performance of the mixer are investigated.The results suggest that the initial loading and rotational speed of impeller have significant effects on the mixing efficiency of particles,while the other two parameters have relatively small effects on the mixing efficiency of particles.Moreover,it is found that the relative velocities between the centroids of the particles after collision could be employed to explain the results of the particle mixing.Secondly,the simulation of the mixing process of non-cohesive solid particles in the single horizontal ribbon mixer is conducted,and then the mixing performance between the single horizontal ribbon mixer and the double horizontal ribbon mixer is compared.The results show that the double horizontal ribbon mixer generate better mixing performance with the top-bottom and front-back initial loadings,while the single horizontal ribbon mixer generate better mixing performance with the side-side initial loadings.Following that,the discrete element model of non-spherical particle is established.The mixing process of non-spherical particle is simulated in the double horizontal ribbon mixer and the single horizontal ribbon mixer.And the effects of the particle shape on the mixing performance of these two mixers have been investigated.Finally,a discrete element model is used for fresh concrete,and its micro-parameter for is calibrated through the slump test and the L-box test.The mixing process of the fresh concrete in the double horizontal ribbon mixer are simulated by the discrete element model.The effects of the operational and geometrical parameters including initial loading(top-bottom,side-side,front-back),rotational speed of impeller and inner blades on the mixing performance of the double horizontal ribbon mixer are analyzed.The study of the regional particle mixing in the mixer is conducted and the dead region of mixing is found.