Interfacial area and volumetric mass transfer coefficient in a bubble reactor at elevated pressures

Abstract The present study deals with the pressure effects on mass transfer parameters within a bubble reactor operating at pressures up to 5 MPa . The gas–liquid systems are N2/CO2-aqueous solution of Na2CO3–NaHCO3 and N2/CO2-aqueous solution of NaOH. A sintered powder plate is used as a gas distributor. Three parameters characterizing the mass transfer are identified and investigated with respect to pressure: the gas–liquid interfacial area a, the volumetric liquid side mass transfer coefficient kLa and the volumetric gas side mass transfer coefficient kGa. The gas–liquid absorption with chemical reaction is used and the mass transfer parameters are determined by using the model reaction between CO2 and the aqueous solutions of Na2CO3–NaHCO3 and NaOH. For a given gas mass flow rate, the interfacial area as well as the volumetric liquid mass transfer coefficient decrease with increasing operating pressure. However, for a given pressure, a and kLa increase with increasing gas mass flow rates. The mass transfer coefficient kL is independent of pressure. Furthermore, the pressure increase results in a decrease of kG and kGa for a given gas mass flow rate. The values of the interfacial area, which are obtained from both chemical systems are found to be different. These discrepancies are attributed to the choice of the liquid system in the absorption reaction model.

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