Model-based control of the dynamics during fine grinding in wet-operated stirred media mills

基于模型的湿式搅拌介质磨细磨过程中的动力学控制

• 批准号: 504930816
• 负责人: Professor Dr. Christian Kirches
• 金额: --
• 依托单位: Institut für Mathematische Optimierung
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/504930816?language=en
• 关键词: Model; based; control; dynamics; during

Stirred media mills are used in various ultra-fine comminution processes. The selected operating parameters in combination with the suspension properties determine the kinetic energy of the grinding media and, in the case of continuous operation, also the transport of the particles as well as the non-uniform axial distribution of the grinding media within the mill. This determines comminution behavior and power consumption. For ultra-fine comminution of the product particles down to the nanoscale, mills are often circuit-operated with an agitated vessel. Hereby, the particle size distributions in the agitated vessel and mill change dynamically. Due to a constant in-crease in specific surface area with decreasing particle size, particle interactions and their influence on suspension stability and viscosity play a fundamental role in ultra-fine comminution. The increase in suspension viscosity has a direct influence on the relative grinding media velocity and thus on the energy transferred to the product particles. In addition, the suspension viscosity influences the axial distribution and thus the movement behavior of the grinding media. Hence, electrostatically or sterically stabilizing additives must be considered in the process control in addition to the control of, e.g., stirrer tip speed or flow rate. Moreover, with changing particle size, the stress energy required for ideal particle breakage, i.e. the optimal operating point of the mill, shifts towards lower stress energies. When controlling a fine grinding process in a wet-operated mill, the interplay between damping of the grinding media through the increase in viscosity, in-crease in particle strength with decreasing particle size and shift in the optimum operating point due to the increase in stress intensity must be considered. Finally, spontaneous reagglomeration or recrystallization processes place high demands on online measurement technology and process control. Although short-cut models and modelling approaches for stirred media mills exist, there currently is no model that allows for dynamic control of changing fine comminution processes with regard to particle size distribution, optimum energy utilization, or maximum production rate. One possibility of control also pursued in this project is the description via population balance models (PBM) in combination with a Nonlinear Model Predictive Control (NMPC) strategy. Thereby the PBM will be described via a mechanistic comminution modell.

搅拌介质米尔斯用于各种超细粉碎工艺。所选的操作参数与悬浮特性相结合决定了研磨介质的动能，并且在连续操作的情况下，还决定了颗粒的输送以及研磨介质在磨机内的不均匀轴向分布。这决定了粉碎行为和功耗。为了将产品颗粒超细粉碎至纳米级，米尔斯通常是带有搅拌容器的循环操作的。因此，搅拌容器和磨机中的粒度分布动态变化。由于比表面积随着粒径的减小而不断增加，颗粒之间的相互作用及其对悬浮液稳定性和粘度的影响在超细粉碎中发挥着基础作用。悬浮液粘度的增加直接影响研磨介质的相对速度，从而影响传递给产品颗粒的能量。此外，悬浮液粘度影响研磨介质的轴向分布，从而影响研磨介质的运动行为。因此，在工艺控制中，除了控制例如，搅拌器尖端速度或流速。此外，随着颗粒尺寸的变化，理想颗粒破碎所需的应力能，即磨机的最佳操作点，向较低的应力能移动。当控制湿式磨机中的细磨过程时，必须考虑研磨介质通过粘度增加而产生的阻尼、颗粒强度随着粒度减小而增加以及由于应力强度增加而导致的最佳操作点的偏移之间的相互作用。最后，自发再团聚或再结晶过程对在线测量技术和过程控制提出了很高的要求。虽然存在用于搅拌介质米尔斯的捷径模型和建模方法，但是目前没有允许动态控制关于粒度分布、最佳能量利用或最大生产率的改变的细粉碎过程的模型。在这个项目中还追求的控制的一种可能性是通过人口平衡模型（PBM）与非线性模型预测控制（NMPC）策略相结合的描述。因此，PBM将通过机械粉碎模型来描述。