Solid suspension in stirred tank equipped with multi-side-entering agitators

The flow field and solid distribution in a stirred tank equipped with four side-entering agitators were investigated using both experimental measurements and CFD simulations. Experiments were carried out to determine the regularity of the solid sediment distribution on the tank bottom and the critical impeller speed for off-bottom suspension. The CFD simulation was performed using the Eulerian-Eulerian two-phase approach, the standard k-ε turbulence model and the multiple reference frame (MRF) approach. The predicted critical impeller speeds were compared with the experimental data to validate the CFD model. The effects of the solid loading and some installation parameters including inclined angles of the impeller, plunging length and mounting height of the shaft on the critical impeller speed were investigated. The predicted results showed reasonably good agreement with the experimental data for both the distribution of solid accumulation and critical impeller speeds. The solid loading has a greater influence on the critical impeller speed in the side-entering stirred tank than that in the top-entering tank. On the basis of the CFD simulation determined critical impeller speeds under different conditions, the above installation parameters of the agitator were optimized. The results and discussion here will have useful implications for design and optimization of the solid-liquid suspension in side-entering stirred tanks.