Gas-liquid Dispersion And Mass Transfer Characteristics Of Non-coalescing System In A Gas-liquid Stirred Reactor

Gas-liquid stirred reactors are widely used in petrochemical, biochemical, pharmaceutical processes, water treatment etc. Though most of multi-phase stirred reactors are operated at the elevated temperature, and there are some solutes in the liquid phase, little attention has been paid to those systems. Experimental study was carried out in the paper on the gas-liquid dispersion and mass transfer characteristics of the Gas-liquid stirred reactor at different temperatures.Experiments were conducted in a triple-impeller stirred tank of 0.476m diameter with dished base to investigate the effect of electrolytes on gas hold-up and power consumption. The impeller combination consisted of a half elliptical disk turbine (HEDT) as the bottom and two up-pumping wide-blade hydrofoils (WHU) above HEDT. Air was used as the dispersed phase and aqueous solutions of Na2SO4 with six concentrations from 0.05mol/L to 0.5mol/L were used as the continuous phase. The results show that the concentration of Na2SO4 solution has a great effect on the hydrodynamic characteristics, gas hold-up increases significantly with the increase of concentration, the gas hold-up in 0.5 mol/L Na2SO4 solution is up to 40% more than that in the deionezed water system. Relative power demand (RPD) decreases as the increase of concentration. It also shows that the influence of temperature is relatively insensitive in electrolyte solution. The gas hold-up in 0.4mol/L Na2SO4 solution at 68℃is 11% less than that at 24℃, and it will be decreased more than 40% from 24℃to 68℃in deionezed water system.Oxygen transfer coefficient (kLa) was measured with the sulfite oxidation method in the same equipment. The influence of the experiment conditions on the kLa was investigated and obtained a suitable experiment condition that using Co2+ as catalyst with a concentration at 10-6 mol/L and the concentration of Na2SO3 is between 0.45 and 0.8mol/L. Investigating the influence of temperature, stirrer speed (N) and air flow rate (VG) on kLa, the result show that kLa increases with temperature, stirrer speed and air flow. It can conclude that DAB increases rapidly with temperature and specific interfacial area (a) decreases with temperature relatively insensitive. The two effects made kLa increase with temperature finally.