OCR Text |
Show 1990 AFRC Int'l Symposium 5 . 32 M NaCl @ 25°C 100 OCl c0 - HOCl -~ Cl ~ __ 3_ ::l 80 --t ........ 0 til \ C \ -~ \ Q) 60 c \ -~ \ I-< 0 --t I,' ..uc 40 " I --t \ ro ~ \ 0 C1 ~ 2 Il-< 20 0 * 0 0 2 4 6 8 10 12 pH Figure 17 Hydrolysis equilibrium of C12 in 5.32M NaCl Based upon the low solubility parameters of NO in aqueous systems, the small gas-liquid contact times that existed in the scrubber and the data collected during experimentation, it becomes apparent that, although knowledge of the mechanism is important for determining reaction constraints for this system, reaction kinetics are not the limiting parameter for NO reduction/removal process. Again, the liquid-phase kinetics may be regarded as instantaneous. The limiting factor is interfacial gas species mass transfer, which becomes the dominant design parameter for consideration. Gas species mass transfer If the hypothesis presented above (that being liquid-phase kinetics of the system are "instantaneous" and gas absorption is the dominant rate controlling mechanism), an analysis of the absorption processes for each gas and the corresponding reaction scheme is necessary. If the response of this system conforms to the model given by Danckwerts, it may be assumed that there exist two films in the liquid phase, separated by an infinitely thin reaction zone. At this plane, the concentration of the reacting species (that of the absorbed gas and its aqueous counter-reactant) may be considered equal to zero. Hence, if the reaction at the interfacial zone is relatively fast, the rate of "reaction" for the system becomes the rate of diffusion of the reacting species to the reaction zone. This condition for the NO/C12 system is not necessarily true (see Figure #18). Once C12 absorption equilibrium has been -14- |