This paper demonstrates the advantages of using the computational fluid dynamics for plant operations or strategic investment decisions.To estimate an optimized geometric design of a tundish with increased steel volume, computational fluid dynamics can help reduce numerous and cost-intensive operational trials. The results concerning the separation of alumina-particles based on a mode of operation with one strand were numerically comprehended and qualitatively confirmed. For this purpose, the particle trajectories of the 50 IJm Al20 3-particles were calculated by means of the Euler-Lagrange model. Based on this model an optimized tundish design and tundish inserts were developed.