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Show 1990 AFRC Int'l Symposium Q\.<) 0.1400 ~ III :I Q) 0.1200 \.< ~ ..-i ~ 0 . 1000 \.< Q) 0. 0.0800 "0 Q) N ..-i ~ 0.0600 ..-i .0 :J ~0 0 . 0400 1/1 N ~ u 0.0200 1/1 Q) ~0 0 . 0000 E 0 solubility of chlorine in HCl solutions as a function of HCl concentration 2 6 10 HCl concentration, mol es HC1/litre water Figure 13 The hydrolysis chemistry of Cl~ The chemistry of C12 hydrolysis may be outlined as follows C12,g C12, aq C1 2, aq + H2O HOCl + H+ + Cl- HOCl H+ + OC1- C1 2, aq + Cl- C13- (3) (4 ) (5) (6) The equilibria achieved in the above reactions are strong functions of the system's operating pH. Figures #14, #15, #16, and #17 illustrate the equilibrium concentrations of the various active species as functions of pH and electrolytic aqueous media. Figure #14 displays the equilibrium shifts for chlorine hydrolysis in primarily a water scrubbing media. Corrections for shifts in HCl concentrations were taken into account for the calculation. As may be seen, the primary chlorine species available in the pH range as observed during experimentation (pH 1-3.5) are C12, aq and HOC1. Both substances are strong oxidizing species. Figures #15-17 display the equilibria shifts in various concentrations of NaCl brine. The effect of excess Cl- is apparent. Review of the experimental data shows NO removal begins after the scrubber pH equilibrium achieves a level of approx. 3-4. For the experimental trials with water, at this pH level, C12, aq and HOCl concentrations are essentially equal and account for the total aqueous chlorine content. Hence both species are available for reaction with NO. As the ratio of the partial pressure (n) increased using a water system, the removal efficiency of NO is higher. However, in scrubbers with 1M HCl solutions (pH 0-1), the NO removal is consistently very high (+90%). Yet even in the HCl system, the effect of increased C12 partial pressure is still evident. Scrubbing in a 1M NaCl brine produced results below removal efficiencies predicted by comparison examination of the data set for water. Earlier trials at brine concentrations of 0.5M showed a better removal efficiency than that achieved by the 1M NaCl scrubber. Analysis of the experimental data with knowledge of the above C12 hydrolysis data and associated thermodynamics help pinpoint the probable reaction path. The kinetic -11- |
