Improving solid-liquid mass transfer and energy efficiency in agitated high concentration slurries

Suspension of solids plays an important role in promoting mass transfer between solids and liquid in mechanically agitated vessels employed in mineral and chemical industries. This becomes especially important when high solids concentrations are used for the purpose of process intensification. Process intensification in agitated vessels (or mixing intensification) requires that the production rate per unit volume has to be increased without major changes in the geometry of the existing infrastructure. Most of the currently employed industrial agitated vessels have baffles in them because they are considered to provide better mixing thereby leading to uniform solids suspension and higher mass transfer rate. However, one of the recent studies by Wang et. al. (2012) has shown that removal of baffles is beneficial for achieving mixing intensification in ultrahigh solid concentrations at an optimum specific power input. Although off-bottom suspension of solids at higher solids concentration (under either baffled or unbaffled conditions) is important for improving the throughput, it will be unsatisfactory if there is no corresponding improvement in mass transfer rate. There have been many studies in the literature which focus on solid-liquid mass transfer in agitated vessels for a variety of geometric and operating conditions but majority of them involve low solids concentration ( <1 0% volume). This work focuses on the influence of geometric parameters such as baffling or impeller type on solid-liquid mass transfer rate and specific impeller power draw at high solids concentrations up to 30% (v/v).