Novel evaluation method for the continuous mixing process of bimodal particles
The continuous mixing process of powder is used in many industries. Careful evaluation of the degree of the mixing is essential to enhance equipment performance. However, no single evaluation method has been universally adopted for the continuous mixing process of bimodal particles due the methods’ poor applicability across multiple process concepts. Presented here are two indices to evaluate mixing in the transverse and axial directions. In this study, the indices are estimated at steady state based on Variance among Bimodal Bin Counts (VBBC), which was introduced as an evaluation method of a bimodal particle mixing system in our previous study. The VBBC mixing index for a continuous mixer is introduced to evaluate the transverse mixing of particles, while an axial stability factor is introduced to evaluate the mixing in the axial direction, which is indicative of the consistency of the process. The importance of each index depends on the characteristics of the process. Therefore, several strategies are suggested for applying the methods to practical cases. In addition, a hypothetical example is presented to illustrate their application: five continuous mixers having differently angled blades are assumed because the blade angle is the most easily modifiable design factor. The bimodal particle mixing processes are simulated using the Discrete Element Method (DEM). Based on the application example, both indices are calculated and the optimal design of a screw is suggested.
Keywords: Continuous mixing process, Bimodal particles, Evaluation method, Mixing index, Discrete Element Method, Variance among, Bimodal Bin Counts,