Influence of suspended solid particles on gas-liquid mass transfer coefficient in a system stirred by double impellers

The aim of the research work was to investigate the effect of the presence and concentration of solid particles on the gas-liquid volumetric mass transfer coefficient in a mechanically stirred gas-solid-liquid system. Experimental studies were conducted in a tall vessel of the diameter of 0.288 m, equipped with two designs of double stirrers. Three high-speed stirrers were used: A 315, Smith turbine, and Rushton turbine. The following operating parameters were changed: gas flow rate, stirrer speed, and solid concentration. The volumetric mass transfer coefficient was determined using the dynamic gassing-out method. In the range of the measurements conducted, this coefficient was strongly affected by both the presence and the concentration of particles in the system. Generally, a low concentration of particles in the system, equal to 0.5 mass %, caused an increase of the volumetric mass transfer coefficient values for both stirrer configurations compared to a system without solids whilst more particles (2.5 mass %) caused a decrease of this coefficient. It could be supposed that an increase of slurry viscosity affected the decrease of the volumetric mass transfer coefficient at higher solid concentration. An empirical correlation was proposed for volumetric mass transfer coefficient prediction. Its parameters were fitted using experimental data. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.