A hydrodynamic model based on continuity and conservation equations was used to predict flow behavior in a spouted-bed dryer with a draft tube. The Eulerian-Eulerian multi-fluid modeling approach was applied to predict a gas–solid flow behavior. The model was qualitatively validated and the results of simulations were compared with the experimental data published by various researchers. The model predicts flow behavior well with fluctuations, circulations of phases, and cluster formations in the loading region, as was observed in experiments. The predicted solids circulation rate and the fraction of gas bypassing were close to experimental values published for various systems. The coarse 2D axisymmetric grid, used in simulations, can handle the main process dependencies with a sufficient accuracy for engineering calculations.

Classic methods of biosurfactant separation are difficult and require large amounts of organic solvents, thus generate high amounts of waste. This work presents and discusses in detail an original procedure to separate rhamnolipid from fermentation broth using high performance membrane techniques. Due to the unique properties of surface active agents, such as capability of forming aggregates above the critical micelle concentration, it is possible to easily purify the biosurfactant with high efficacy using inexpensive and commonly used membranes. In this article, two-stage ultrafiltration is proposed as a method for separating and purifying rhamnolipid from the culture medium. The obtained purified rhamnolipid solution was capable of reducing surface tension of water down to 28.6 mN/m at critical micelle concentration of 40 mg/l. Separation of rhamnolipid was confirmed by HPLC; three types of rhamnolipids were identified (RL1, RL2, RL4), with considerable predominance of RL2.