Mass transfer analysis in ozone bubble columns

An impinging-jet bubble column has been tested for the ozone mass transfer applications in water treatment. Two venturi injectors were utilized to create turbulent gas-liquid jets in the ambient fluid by placing them at an intersecting angle of 125degrees. The intersecting of the jets caused an increase in the turbulence produced in the ambient fluid and therefore, increased the gas-liquid mass transfer rate. The steady-state one-phase axial dispersion model (1P-ADM) was applied to analyze the dissolved ozone concentration profiles measured in the bubble column by fitting these profiles to the predicted profiles, using the 1P-ADM, to determine the column-average overall mass transfer coefficient (k(L)a) and liquid-phase axial dispersion coefficient (D-L). Two minimization approaches were applied to solve the differential equation representing the 1P-ADM: two-parameter (k(L)a and D-L) and one-parameter (k(L)a) minimization techniques. To examine the sensitivity of the predicted kLa to changes in D-L, D-L was estimated first from the tracer experiments. Then, the one-parameter minimization technique was applied to determine k(L)a. As a result, k(L)a varied only slightly (<11%) between the two types of minimization techniques. Using the two-parameter minimization technique, k(L)a and D-L values were correlated to the superficial gas and liquid velocities (u(G) and u(L), respectively) by power-law relationships. The following correlations were obtained: k(L)a = 20.54 u(G)(1.13)u(L)(0.07) and D-L = 2.94 x 10(-2)u(G)(0.03)u(L)(0.18). The 1P-ADM has proven to be an accurate and easy-to use tool for describing the ozonation process in the impinging-jet bubble column as an excellent conformity between the measured and the predicted dissolved ozone concentration profiles was observed.