Ozone mass transfer and reaction in in situ and stirred tank reactors

Ozone mass transfer and reaction efficiency were studied in an in situ ozonator and a stirred tank reactor (STR) to examine enhancements in mass transfer and reaction efficiency in the in situ ozonator over conventional ozonators. The effect of ozone isotopes on dye decolorization rates was also investigated. Mass transfer models were developed considering reactors-in-series for both fluid phases in the in situ reactor, whereas the liquid phase is described as a well mixed, and the gas phase is described as a plug-flow system in STR. The models are used to estimate mass transfer coefficient values in both the reactor systems. The mass transfer coefficient (KLa) was found to increase with increasing superficial velocity of gas in both the reactor systems, and with increasing superficial velocity of water in the in situ reactor. The KLa values estimated in the in situ ozonator on average are more than 110% higher than that reported in the literature for bubble columns and about 28% higher than for packed towers. The specific power requirement calculated for the in situ reactor is lower than that reported in literature for the bubble columns and the stirred tank reactors.; Oxidation models based on film theory were developed to study ozonation of Reactive Blue 19 dye in both types of reactors. The model takes into account the effect of simultaneous reaction of ozone on gas absorption rate, and considers reactions in the film and the bulk liquid separately. Close values of rate constants for the dye decolorization reaction obtained in both the reactor systems show that there is very little effect of any short-lived species formed near corona region in the in situ reactor on the dye decolorization kinetics. The rate constant for reaction of ozone with the byproducts based on COD was about 62% higher than that in the STR. This indicates the presence of other reactive species in the reaction with byproducts in the in situ reactor. In the in situ reactor, about 15% more mineralization of organics was observed than in the STR. No significant effect on dye decolorization rate was observed when ozone generated from a gas mixture containing isotopes up to 20 (v/v) of 18O 2, and up to 4% (v/v) of 17O2 was used in oxidation studies.