Gas-Liquid Dispersion Characteristics In A Stirred Tank With High Viscosity Fluid

More and more non-Newtonian fluid products are produced with the development of biochemical industry, in which xanthan gum is one of the most important. With the expanding of production, large-scale gas-liquid stirred tank reactor for xanthan gum fermentation occupies a pivotal position. In order to investigate the power consumption and gas-liquid dispersion effect in stirred tank, the aqueous xanthan gum is used as the media and equipments of mixing and gas distribution are optimized designed.The research is based on power consumption and gas holdup. In the experiment four impellers are used (WHU WHD HEDT InterMig) and the impellers are optimized designed from configuration and its diameter. The gas spargers are also optimized designed and we also have the research on agitator impellers of InterMig which is applied in industry.The research results show that for gased power consumption, when the radial flow impeller is used bottom impeller and axial flow impeller is used as upper impeller, a higher relative power demand (RPD) is obtained. Studies showed that the RPD increases with the increase of impellers diameter for double WHU impellers. When the opening-hole-diameter of different gas spargers are same, RPD increases with the increase of gas sparger diameter. When gas sparger diameters are same, RPD increase with the decrease of opening-hole-diameter with different gas spargers.In the investigations of gas holdup with different impeller combinations, when the stirred system accesses the carrier gas state, the highest gas holdup is obtained with the bottom impeller HEDT and upper impeller WHU. When superficial gas velocity is low (0.0078m/s), the gas holdup increases with the increase of impeller diameter at the same specific power consumption. However, this increasing trend gradually gets slower with the increasing superficial gas velocity. When the superficial gas velocity is0.0459m/s, the gas holdup is almost invariant. When the specific power consumption is less than1W/kg, the gas holdup is nearly no difference for the same opening-hole-diameter with different diameter of gas sparger. When specific power consumption is more than1W/kg, the gas holdup increases with the diameter of gas distribution increasing. For the same diameter of different gas distributor the gas holdup gradually increases with the decrease of the diameter of the opening hole. The gas holdup of impeller agitator with different main and vice impeller and the impeller agitator with the same main and vice impeller is much less than that of double impeller WHU-When specific power consumption is less than1W/kg, the gas holdup of double impeller WHU is less than the impeller agitator which bottom layer impeller is PDT and the other impeller is InterMig with the same main and vice impeller. When specific power consumption is more than1W/kg, the gas holdup of double impeller WHU is more than the impeller agitator above-mentioned.