Determination of mass transfer and hydrodynamic characteristics of different liquid medium in cocurrent downflow contacting reactor (CDCR)

In this study, the transfer of oxygen from gas phase to the liquid phase of physical characteristic different was investigated by using A Co-current Downflow Contacting Reactor (CDCR) and also production of a-amylase by Bacillus amyloliquefaciens NRRL B-645 was determined by using CDCR. In addition, to obtain of gas holdup and mass transfer coefficient related to the variables such as liquid kinetic power per liquid volume in the column, superficial gas velocity and relative surface tension, some correlations were proposed.In the first stage of the work, hydrodinamic conditions and mass transfer characteristics of the co-current downflow contacting reactor were studied for different liquids and varied concentrations of glycerol for 2, 3 and 4 mm orifice diameter. Volumetric mass transfer coefficient (kLa) and gas holdup values were increased with increasing liquid and gas flow rates for each orifice diameter. The values of kLa values determined for air-water system were higher than kLa values of other liquids However gas holdup and dispersion height values determined for air-water system were lower than values of other liquids due to decrease in the liquid surface tension.To determine the avarage bubble diameter for each condition, photographic techniques were used, and the diameters of bubbles were measured as 3.840 mm, 2.467 mm, 2.055 mm, 1.543 mm, 1.322 mm and 1.284 mm for air-water, air-butanol, air-anionic surfactant, air-cationic surfactant, air-non ionic surfactant and air-fermentation broth, respectively. In addition, the effects of hydrodynamic conditions and liquid properties on bubble diameters and formation were determined.In the second stage of the work, bacterium cell, Bacillus amyloliquefaciens NRRL B-645, was grown in a concentration of 10 g/lt glucose by using 2, 3 and 4 mm orifice and for each orifice maximum dry cell concentration were determined to be 4.142, 5.000 and 4.873 g dry cell/lt, respectively. In a medium of 10 g/lt glucose by using 3 mm orifice, specific growth rate of bacterium and the substrate utilization rate were determined to be 0.310 saat-1, 0.500 g dry cell/g glucose, respectively. The values of kLa and ro , increased at the active growth phase and than decreased with decreasing active cells.The production ?-amylase by using starch as substrate in the CDCR with Bacillus amyloliquefaciens were used starch in different concentrations (7.5, 10, 15 ve 17.5 g/lt). Maximum enzyme activity which made in experiments (500 IU) was obtained in the medium containing 15 g/lt nişasta, 2.5 g/lt pepton, 1 g/lt yeast ekstrakt, 1 g/lt KH2PO4, 0.5 g/lt MgSO4.7H2O and 0.114 g/lt CaCl2.2H2OIn the third stage of the work correlations proposed for gas holdup and volumetric mass transfer coefficient were obtained by analyzing experimental data. It was found that the gas holdup and kLa were dependent on power per volume of liquid in the column.