A REFINED MODEL FOR OZONE MASS-TRANSFER IN A SEMIBATCH STIRRED VESSEL

The mathematical model proposed by Anselmi et al. (1984) for a semibat ch stirred gas-liquid contactor is refined to describe the mass transf er of ozone absorption and decomposition in aqueous solution with the decomposition rate expression of general reaction orders (not necessar ily integers). Three system equations are employed to describe the ozo ne concentrations in the bulk liquid (C-ALb), the hold-up gas (C-AGi), and the outlet gas in the free volume above the liquid surface (C-AGe ), respectively. The effect of ozone decomposition on the mass transfe r, which is reflected by the enhancement factor (E-r) defined as the r atio of mass absorbed per unit area in time t with chemical reaction ( r) to that without chemical reaction or of the purely physical absorpt ion, is considered in the refined model. Furthermore, the refined mode l also takes into account the variation of E-r with C-ALb, which chang es with time during the course of gas-liquid contacting. Thus this ana lysis extends the applicability of the model of Anselmi et al. (1984) and is of special importance for ozone mass transfer in the cases of b asic solutions and of low mass transfer coefficients, in which the eff ect of decomposition on absorption is significant, and in the system w ith variable liquid phase ozone concentration.