High pressure flow gravimetric apparatus for supercritical fluid extraction studies

An experimental apparatus has been developed for real time measurements of fluid-solid adsorption (or desorption) rates and equilibria at elevated pressures. In addition to controlling pressure and flow rates simultaneously, this setup is able to operate at higher flow rates than previously possible in supercritical fluid experiments. The system consists of a high pressure microbalance, two high pressure syringe pumps, and an absorbance detector. The microbalance enables the collection of data at a greater time resolution, resulting in a more accurate measurement of rate data. Because of the dual syringe pump design, there is no pressure drop in the system, making it possible to operate at a wide range of flow rates (at experimental conditions). The buoyancy force was measured with helium experiments, while the hydrodynamic forces were measured using a clean solid sample and supercritical carbon dioxide at different flow rates. It was found that the hydrodynamic force increased with flow rate as expected. The apparatus was tested by conducting two desorption experiments of phenol from activated carbon at 141+/-0.07 bar, 36.0+/-0.02 degrees C, and 0.47 ml/min (at experimental conditions). The amount of phenol removed was 16.4% and 18%, respectively! in the two runs which is consistent with previously published results and indicates the difficulty of regenerating activated carbon loaded with phenol. (C) 1997 American Institute of Physics.