Investigations Of Mass Transfer Efficiency In Confined Impinging Jets Reactor

The impinging jets method which was first proposed by Elperin is to make two or more high speed jets flow along with the same axis and collide in a narrow zone. After the colliding, the axial velocity of the jets will be transferred into the fluctuating velocity, and then a collision zone characterized by very severe turbulence is formed. In the collision zone, the turbulence of the flow field generates a very big impact, and the severe shear force makes the drops of the fluids very tiny ones which increase the contacting area and promote the driving force of the mass transfer process. For these advantages, the impinging jets can strengthen the phase heat and mass transfer, and reduce the bulk of the producing devices. There are many applications and researches of the impinging jets in various chemical producing fields, and the impinging jets extraction process is one of them. The impinging jets reactor has the advantages of huge energy of the flow field and severe turbulence effect which could promote the fluid mixing significantly, and make up for the disadvantages of small contacting area, small mass transfer coefficient and long reaction time of the traditional extraction reactor.Butyric acid (CH3CH2CH2COOH) is an important organic synthesis material which is very easy to be realized by a very low concentration for its unpleasant smell like the spoilage cream. Although the concentration of butyric acid in the industrial waste water is pretty low, it will be wasteful and pollute the environment if some treatments aren’t made. Therefore, the treatment for the butyric acid waste water is of great importance.This study investigated the mass transfer effects of TBP extracting butyric acid processes in both impinging jets reactor and the stirred tank reactor, and made a comparison of their results. The experiments were made in the following sections:1. In the impinging jets experiments, the effects of the concentration of butyric acid Caq and TBP Corg, the impinging velocity V, the upper distance of the impinging zone L, the impinging velocity ratio of two phases Vorg/Vaq and the inner nozzle diameter di for the extraction efficiency E and the overall volumetric mass transfer coefficient KLa of the extraction processes were tested. It was found that the concentration of butyric acid and TBP, the impinging velocity, the impinging velocity ratio and the inner nozzle diameter affect the extraction processes a lot; whereas the upper distance of the impinging zone has a negligible effect. Then, a correlation about these variables and the overall volumetric mass transfer coefficient KLa was proposed, which can make a relative good prediction of the data and KLa.2. The concentration of butyric acid Caqand TBP Corg, the extraction equilibrium time t, the phase ratio P, the Stirring speed S and the extraction temperature T were investigated in a traditional stirred tank. The results showed that the concentration of butyric acid and TBP, the extraction equilibrium time, the phase ratio and the Stirring speed have significant impact on the extraction process, and the effect of the extraction temperature is negligible. At last, a comparison of the two reactors were made, and found that for the fast reaction system, the impinging jets reactor, which can strengthen the extraction processes, has a better but limited mass transfer performance than the stirred tank.