Bubble Column Reactors for Wastewater Treatment. 1. Theory and Modeling of Continuous Countercurrent Solvent Sublation

摘要

Solvent sublation is a nonfoaming wastewater treatment process that combines the benefits of bubble fractionation and liquid-liquid extraction in a way that does not require mixers, settlers, or subsequent downstream treatment. A review of past work on small lab-scale batch columns revealed that removal efficiencies of nonvolatile and volatile organic compounds are generally higher than those observed in bubble fractionation, air stripping, and conventional liquid-liquid extraction. In this work, the first of a three-part series, the transport mechanisms in a three-phase continuous, countercurrent sublation process are presented. Two mathematical models, namely, the series CSTR model (SCM) and the two-phase axial dispersion model (ADM2), are developed. It is shown that these two models are equivalent and can be used interchangeably with the aid of a simple expression. Nondimensional correlations, based upon simulated data obtained from the SCM, are generated to predict the steady-state fractional removal, FR, and the separation factor, Σ (ratio of effluent solvent concentration to effluent water concentration), for strongly hydrophobic compounds. The effects of operational, hydrodynamic, thermodynamic, and design variables on sublation performance are discussed.