Study On The Interfacial Reactions And Mass Transfer Between Phases Of Multiphase Flow In Bubble Column

For optimum energy utilization purpose, the investigation of muti-phase interfacial mass transfer behavior should be taken into consideration in many industry fields, such as in wastewater treatment plant, chemical engineering process, et al. Currently, the possible factors on which mass transfer behavior may greatly depends have been investigated and the clarification of the possible mechanism is yet needed.In this work where the experiment was carried out in bubble column reactor with 0.15m in diameter and lm in height, the aeration conditions (temperature, aeration, water depth) and additives in multiphase flow (surfactants, electrolytes, solid Fillers, etc.) that may have significant effect on the mass transfer were systematically investigated, since there may exist different interfacial mass transfer behaviors in the presence of solutes with different physicochemical properties. Experimental results were shown below.1. The enhancement of oxygen mass transfer is not in a simple linear relationship with superficial gas velocity]. For the perspective of energy saving, proper enhancement of the superficial gas velocity is favorable for oxygen mass transfer. Increase in temperature can accelerate the gas flow rate as well as the bubble breakup, though the solubility of oxygen may be reduced to some extent at higher temperatures. Consequently, the mass transfer intensity can be enhanced. The relationship between water depth and oxygen transfer fits well with KLa1/KLa2=βg(h2/h1)1/3 wnereβis 0.9 empirically.2. Electrolytes have certain inhibition to oxygen mass transfer in water, the higher salinity of the electrolyte solution, or the higher ionic strength led to the stronger inhibition of oxygen transfer. In SDBS solution, for the interfacial accumulation of SDBS molecular, the hydrophilic and hydrophobic groups arranged closely, resulting in an obvious mass transfer inhibition, where lower surface tension leads to a stronger effect. In CTAB solution where CTAB concentration lower than the CMC, lower surface tension plays a major role since it can strength mass transfer. However, the micelles gathered on surface layer as CTAB concentrations higher than the CMC causing a hindered oxygen transfer. In n-butanol system with a constant surface tension, oxygen transfer should be attributed to interfacial circulation effect, i.e. the so-called Marangoni effect, which intensified the interfacial turbulence and surface renewal rate of the "liquid flim" 3. The effects conter-ions presented in surfactants solution on oxygen transfer were significant also. NaCl should be taken into consideration, for its salting-out effect on SDBS molecules and "stratification" effect on the micells. The presence of NH4Br can inhibit the mass transfer by promoting the molecular migration into the interface and their accumulation into micelles simultaneously. In addition, the surfactants solution physicochemical properties (surface tension, zeta potential, viscosity, et al.) were significantly affected in the presence of conter-ions.4. By Comparison, the effects on oxygen mass transfer were experimented in the presence of sponge filler, BioMTM and carbon filler, respectively. It can be conclused that, sponge filler and BioMTM is porous, which can be streamed easily and cut bobbles effectively, i.e. they can promote oxygen mass transfer eventually. Though carbon filler is porous, it is not easy to be fluidized. Besides, higher superficial gas velocity favors the oxygen mass transfer efficiency.The result of our experiment may provide relatively valuable experimental data as well as theoretical references for the scaling-up of multiphase reactors, and also can contribute to the study of mass transfer and reaction mechanisms, reaction rate control et al. for its application in the practical engineering conditions.