Gas-Side Mass Transfer Coefficients in Packed Tower

Abstract

The overall gas-side capacity coefficients (KGa) in the towers packed with 1''-, 1/2''-, 3/8''-Raschig rings and 1''-, 1/2''-Berl saddles, respectively, were measured by means of the absorption of ammonia by water. The gas-side capacity coefficient (kGa) was calculated by subtracting the resistance of liquid phase from KGa, using the equations the authors reported previously. KGa and kGa were correlated with liquid and gas rates by the exponents figured in Table 2, which were in agreement with the values obtained from the previous experiments.Assuming that the effective surface area (a) was proportional to the wetted surface area (aω) as described in the authors' previous reports, kG was derived by dividing kGa by aω. It was clarified that kG derived in this way was completely independent of the liquid rates. From the nature of kG, this independence of kG of L appeared to be most reasonable.The relation of kG with other operational variables, especially with G, was expressed by Eqs. (8) and (9) for Raschig ring and Berl saddle, respectively.Allowing some discrepancies between them, these relations were summarized into the following single equation for both Raschig rings and Berl saddles:(kGRT/atDG)=0.014(G/atμG)0.8(ρG2g/μG2at3)0.2(μG/ρGDG)1/3By the similar procedure, another single equation was obtained as follows, representing the liquid-side mass transfer coefficient:kL(ρL/μLg)1/3=0.02(L/atμL)1/2(μL/ρLDL)-1/2