THE GAS-LIQUID MASS-TRANSFER COEFFICIENT (K(L)A) IN THE GAS-LIQUID MULTISTAGE AGITATED CONTACTOR (MAC)

Data on the volumetric liquid-side gas-liquid mass transfer coefficien t, k(L)a, in a Multi-stage Agitated Contractor (MAC) are reported for three gas-liquid systems (air-water, helium-n-octane, and air-Monoethy lene Glycol (MEG)). k(L)a (s(-1)) was determined using a dynamic metho d with moderately soluble gaseous tracers (acetylene for water and MEG and methane for n-octane). The observed response curves could be desc ribed accurately by coupling the single phase residence time distribut ion models for gas and liquid phase (Breman et al., (1,2)), via interf acial gas-liquid mass transfer. All k,a data could be correlated with an average relative deviation of 11.3% by a combination of Calderbanks ' relation(3) for k(L) (m s(-1)) and a modified type of Calderbanks' r elation(3) for the interfacial area, a (m(-1)), which takes a combined effect of the superficial gas velocity (u(G)) and the liquid viscosit y (eta(L)) on a into account: a = 51.1(P/V)(0.286) sigma(-0.19)(u(G)/v (b))((0.127+21.1 eta L)) with g = acceleration of gravity (= 9.81 m(2) s(-1)), P/V = volumetric power input (W/m(-3)), v(b) = bubble rise ve locity (m s(-1)) and the experimental conditions ranging from: superfi cial gas velocity u(G) = 0.01-0.09 m s(-1), stirring speed (N) = 10-36 .7 rev s(-1), eta(L) = 0.00041-0.021 N m(-2) s, surface tension (sigma ) = 0.02-0.073 N m(-1), liquid density (rho(L)) = 684-1113 kg m(-3), g as density (rho(G)) = 0.16-1.205 kg m(-3) and liquid diffusion coeffic ient (L-L) = 1.3 x 10(-10)-3.5 x 10(-9) m(2) s(-1). The overall influe nce of u(G) on k(L)a in this relation is such that k(L)a is hardly aff ected by u(G) both for water and n-octane, whereas, in contrast, k(L)a is predicted to increase significantly with increasing u(G) for the m ore viscous monoethylene glycol, The general applicability of the prop osed relation for a has to be confirmed by measurements for other liqu ids and by measurements on a larger scale.