SOLID-LIQUID MASS-TRANSFER COEFFICIENTS IN GAS-SOLID-LIQUID AGITATED VESSELS

The research on mass transfer coefficients in solid-liquid agitated sy stems has received substantial attention in the past, due both to the interest in fundamental aspects of mass transfer between particles and turbulent fluids and to the importance of practical applications. In contrast, little information is available on solid-liquid mass transfe r when a third gaseous phase is also dispersed into the system, in spi te of the importance of the applications of gas-solid-liquid agitated systems. In this work a suitable dissolution technique was used to mea sure the solid-liquid mass transfer coefficient in gas-solid-liquid ve ssels stirred by either radial or axial impellers. The mechanical powe r dissipated by the stirrers at various agitation speeds and gas flow rates was also measured by means of a new technique. The mass transfer data obtained were found to be well correlated to the 0.25 power of t he specific power dissipation, indicating that the Kolmogorov's theory of mass transfer applies to these systems, while no clear influence o f the gas hold-up was ascertained.