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Show 1990 AFRC Int'l Symposium scrubber fluid make-up. It has been noted that small quantities of surfactants may cause a sizable decrease in gas absorption rate from bubbles, due to the formation of a film around the bubble which limits the amount of internal gas circulation [Bird, Stewart, Lightfoot (1960)]. The powerful effect of surface agents on the mass transfer process may be witnessed by comparisons between data from experiments using 0.5M and 1M solutions. The inadvertent effect of surface agents was found to be somewhat beneficial in a scrubbing system using a 0.5M solution of NaCl. The amount of surfactant available sufficiently lowered the solution surface tension such that smaller bubbles were formed, as would be predicted by theory. This resulted in a larger area for mass transfer and countered the effects of film-induced internal bubble gas circulation stagnation, as observed in the 1M solution trial. The result was a NO removal efficiency slightly better than that seen in water. CONCLUSIONS The results of experimentation on the NO scrubbing system involving Cl2 injection into a gas stream followed by rigorous aqueous scrubbing have been presented. Dow's patented NOx scrubbing process is capable of +90% (vol.) of NO from gaseous streams. The system parameters as defined by this work are as follows : 1. This process, a direct injection of chlorine into the gas stream followed by thorough scrubbing with an aqueous solution, is a masstransfer limited gas-liquid reaction and highly dependent upon scrubber pH, chloride ion content and temperature. Particular care must be given to the design of the scrubbing equipment to insure adequate area available for gas absorption. Operation of packed towers will need to insure redistribution of the liquid throughout the column is sufficient to guarantee proper gas-liquid interfacial contact area. The prudent use of small amounts of surface active compounds in a bubble column-type environment may be used to meet the surface area needs of the system. 2. The liquid-phase reaction kinetics showed no sign of temperature dependence in the range investigated (10°-90°C) and, based upon measured removal efficiencies and gas-liquid residence times may be considered "instantaneous". Operation of the system in an acidic medium is necessary to insure proper chlorine hydrolysis products are available in the scrubbing medium for reaction with NO upon absorption. BIBLIOGRAPHY Adams, F.W.;Edmonds, R.G. Ind.Eng.Chem. 29(1937) :447-451. Aieta, E.M.; Roberts, P.V. Environ. Sci. Technol. 20(1988) :44-50 Armor, J.N. J.Chem.Eng.Data. 19(1974) :82-84. Bailey, J.E.;Ollis, D.F. Biochemical Engineering Fundamentals 2nd ed. New York: McGraw-Hill, 1986. Bamford, C.H.; Tipper, C.F.H. (editors) Chemical Kinetics Arnsterdam:Elsevier, 1972 Beckham, L.J.; Fessler, W.A.; Kise, M.A. Chemical Reviews 48(1951) :319-396 Bird, R.B.;Stewart, W.E.; Lightfoot, E.N. Transport Phenomena New York: Wiley, 1960. Brian, P.L.T.; Vivian, J.E.; Piazza, C. Chem.Eng.Sci. 21(1966) :551-556 Charpentier, J.C. Trans. IChemE. 60(1982) :140-144. Connick, R.E.;Chia, Y. J.Amer. Chem. Soc. 81(1959) :1280-1284. Counce, R.M.; Perona, J.J. Ind.Eng.Chem.Fundam. 18(1979) :400-405. -16- |
