Research On Mixed Mechanism Based On DEM In Vertical Turbulence Mixer

Mixing equipment is widely used in metallurgy,glass,building materials,environmental protection and ceramics industries.At present although our country manufacturing enterprises are numerous in this field,but the overall technical level is slightly low.Import equipment from abroad is expensive,and difficult to maintain,which always can't meet the enterprise satisfaction.Therefore,it is of great significance to explore the mixing mechanism of mixing equipment,to realize the practical value of mixing equipment,to improve production efficiency and to save production cost.It is of great significance to the development of production of building materials and metallurgy as well as environmental protection in China.The Discrete Element Method(DEM)resolves particle flow behaviors at an individual particle level,and it can provide a wealth of information of the particle's force and motion,which provides a feasible method for dealing with the visualization of the mixing motion of the material in the mixer.In this study,the mixing process of fly ash and sludge material in the vertical turbulence mixer was studied based on DEM(discrete element method),and the parameters(such as structural parameters,operating parameters and material properties of the mixer)influences were explored on the mixing characteristics of the mixer.It provided theoretical support and technical guidance for the structural and operation improvement.The main research contents and achievements can be summarized as follows:(1)The mixing characteristics of the granular materials were analyzed,and the basic methods of mixing the granular materials were summarized.Appropriate mixing performance evaluation methods were discussed and selected.(2)The structure and working principle of the vertical turbulence mixer were analyzed,and the physical model of the mixer was established,the key simulation parameters were determined.The Hertz-Mindlin with JKR model was selected as the contact model for the particles and verified by experiments.The results show this model can be used to simulate viscous wet granules systems such as fly ash and sludge.(3)The factors such as the initial loading of the vertical turbulence mixer,the inclination angle of the stirring cylinder,the angle of the stirring blade,the speed of the stirring shaft and the fill level in the mixer were analyzed,the mixing of the particulate materials under different conditions was analyzed,and the influence of each factor was taken into account.Finally optimized parameters were obtained.(4)The effect of the viscosity of the wet granules and the particle size on the mixing performance effect were analyzed by changing the viscosity between the wet particles and the particle size.The results showed that the cohesive force between particles has an effect on the mixing performance of particles in the part area,but has a relatively small effect on overall mixing performance,and the particle size within a certain range has little effect on the mixing performance.(5)The simulation results were compared to the clay sample stirring experiment carried out by the R08 W type Eirich equipment in Germany.The comparison of the clay particle stirring experiment is carried out by comparing the flow characteristics of the clay material in the stirring cylinder.Stirring shaft and the stirring cylinder's useful power were obtained according to the change of the resistance torque,the results show that the correctness of the numerical simulation results can provide the theoretical support and technical guidance for the structural design and operation of the vertical turbulence mixer.