CFD Simulation of a New Dynamic-Static Stirred Model and Its Application in the Leaching Process of Chromite

In the liquid phase oxidation leaching process of chromite salt, a new dynamic-static combined stirred mode is proposed. That is, a static cylindrical baffle is fixedly installed at a certain radius from the stirred blade to control the vicinity of the blade. The CFD numerical simulation method is mainly used to investigate the effect of dynamic-static combined mode on the flow field distribution. Meanwhile, the velocity distribution and trailing vortex near the blade are analyzed. Finally, the differences between traditional stirred blade and dynamic-static combined stirred blade in the oxidation leaching process of chromite are compared. The results show the new dynamic-static combined stirring mode can effectively improve the flow field distribution, reduce the occurrence of “dead zones” in the flow, and increase the chromite leaching efficiency. The leaching time can be reduced from 300 to 240 min, and the chromium-leaching rate has reached up to 99%.

Formation mechanism and chaotic reinforcement elimination of the mechanical stirring isolated mixed region

The isolated mixed region (IMR) is gradually formed during stirring and reduces the mixing efficiency. The unsteady-state formation process of the IMR was modeled and its formation mechanism was analyzed. The rotating frequency of the impeller was optimized using the chaos mathematical theory to improve the stirring efficiency without increasing the power consumption. The calculated results demonstrate that the IMR is a coherent structure, and its formation process is based on the free shear effect of the mixed layer. The chaotic stirring method can accelerate the momentum dissipation process by 37% by eliminating the IMR, and increase the speed by up to 31%. Therefore, chaotic mixing can eliminate the IMR in a shorter time and lower the power consumption.