Fractionation of a dilute acetic acid aqueous mixture in a continuous countercurrent packed column using supercritical CO2: Experiments and simulation of external extract reflux

Abstract : Fractionation of dilute acetic acid aqueous mixtures was operated using a continuous countercurrent packed column with supercritical CO2. A generic procedure was developed to assess the feasibility of such an operation. Experiments were performed using a 2 m high and 17 mm inner diameter column, in the range (10−15 MPa) and (40 °C–60 °C). Thermodynamics of the mixture was described using the Soave-Redlich-Kwong equation modified by Boston Mathias with PSRK mixing rules and UNIQUAC activity coefficient model. Experimental results were compared to simulation using a software based on the concept of equilibrium stage. Conventional liquid-liquid extraction methods indicated that thermodynamics limits the separation performances. Therefore, an external extract reflux configuration was tested by simulation. It was shown that the limitation could be overridden and influence of design (number of stages, position of the feed) and operating conditions (reflux ratio, solvent-to-feed ratio) has been assessed.