Study Of Flow Characteristics Of Multiphase Fluids In Continuous Ball Mills

Under the national strategy of green development with "carbon neutrality" and the policy of "dual control" of energy consumption,the traditional ceramic industry,which is characterized by high energy consumption,high pollution,and high costs,must undergo an upgrade and transform towards high-end,intelligent,and green development.The ball milling stage,which is the most energy-consuming stage in the process of ceramic raw material preparation,has become a bottleneck problem that restricts the development of the industry.In this study,we conducted a systematic investigation of the five-body continuous ball milling system using a research method that combines theoretical studies and numerical calculations.We proposed a real-time slurry property control strategy to achieve continuous and stable production of slurries,thereby solving the common quality control problem of granulated powder in wet powder preparation.In terms of theoretical research on wet ball milling,based on particle motion equations,we found that the main factors affecting particle motion are the interaction forces and moments between solid phases,as well as the forces exerted by the fluid on the solid.The interaction forces between solid phases include the contact forces between particles and the contact forces between particles and lining plates.Particle-particle interactions primarily involve normal and tangential contact forces,which were calculated using the Hertz-Mindlin contact model.The forces exerted by the lining plate on the particles were obtained by calculating the collision force and friction force under three different rotational speeds.The moment experienced by particles due to translation and rotation during collisions was calculated using the linear elastic spring rolling resistance model.The interaction forces between the fluid and the solid mainly include the drag force and pressure gradient force of the fluid phase,with the Huilin&Gidaspow drag model selected to calculate the drag force of the fluid phase on the solid.Regarding numerical simulation of multiphase flow in continuous ball milling machines,we used the CFD-DEM bidirectional coupling simulation method to analyze the gas-liquid-solid three-phase flow problem in ball milling machines.The DEM method was used to calculate the particle phase,while the Eulerian model was used to calculate the fluid phase.Data exchange between the two phases was achieved through CFD-DEM bidirectional coupling,and the phase interface was captured using the volume fraction of the particle phase.The simulation results showed that when the ball milling machine was rotated at 13 rpm,the average drag force experienced by particles was maximal at 0.076 N,and the maximum average pressure gradient force was 0.309 N.The lining plate experienced an average collision intensity of 2743.606 W/m²,while the average impact power on particles was 0.053 W.The consumed power of the ball milling machine was 11715.774 W.When the rotational speed of the ball milling machine increased,the slope of the impact curve between the grinding medium and the sandstone material changed gradually,first increasing and then decreasing,indicating that the optimal milling efficiency was achieved when the ball milling machine was rotated at 13 rpm.A Kriging-based method was used to develop a surrogate model for predicting the performance indicators of ceramic slurries based on process parameters.Variance-based sensitivity analysis was used to quantify the influence of each process parameter on the performance indicators.The results showed that the two input parameters with the greatest impact on the specific gravity of ceramic slurries were water flow rate（Q_w）and slurry flow rate（Q_s）.The two input parameters with the greatest impact on the flow velocity of ceramic slurries were slurry flow rate（Q_s）and additive flow rate（Q_a）.The two input parameters with the greatest impact on the screen residue of ceramic slurries were the motor current（I₄）of the fourth ball mill,which is related to the loading capacity of the fourth ball mill and slurry flow rate（Q_s）.A software package for predicting the performance indicators of slurries was developed,enabling rapid and accurate prediction of the performance indicators of ballmilled slurries.