Simultaneous extraction and sorption under supercritical conditions

Supercritical Exsorption (SCEXS), simultaneous supercritical extraction and sorption (adsorption and/or desorption), is a novel process which may have potential for applications in chemical, biochemical and environmental engineering. The system of interest consists of a fixed-bed packed with an adsorbent (e.g., activated carbon or catalyst) through which a solvent stream (e.g., supercritical carbon dioxide) and a feed stream (e.g., an aqueous stream with low concentration of solute such as phenol) flow countercurrently.; In this work, the theoretical foundations of SCEXS have been established through distributed-parameter modeling which enables phenomenal description of several probable three-phase mass transfer dynamics taking place in the bed. The equilibrium theory of exsorption, which reveals very important and interesting aspects of the wave propagation dynamics, and which enables the derivation of functional analytical solutions to some limiting cases, has also been established.; An equation of state based sorption isotherm has been developed to correlate the supercritical phase sorption equilibrium data, which also successfully predicts the temperature, pressure, and density effects in supercritical desorbers, and explains the solubility-sorption relationships under supercritical conditions.; The required thermophysical properties and mass transfer coefficients for the modeled system (phenol-water-supercritical carbon dioxide-activated carbon) are evaluated at the supercritical region. Through numerical solution of the proposed model the conditions under which the contributions due to extraction, adsorption, and desorption mechanisms of the three-phase mass transfer become predominant are identified. The best operational temperatures and pressures with regard to prolonged bed activity and solute-removal capacity under possible different phase aggregations are selected by capitalizing on the parametric sensitivities of both the supercritical fluid solvency power and of the sorption equilibrium. The operation of a multi-column SCEXS with side-stream solvent regenerators is also studied, and the conditions which necessitate and/or favor this type of operation scheme are identified.