12.6. A packed tower is used for absorbing sulphur dioxide from air by means of a 0.5 N caustic soda solution. At an air flow of 2 kg/m2s, corresponding to a Reynolds number of 5160, the friction factor R/u2 is found to be 0.020.

Calculate the mass transfer coefficient in kg SO2/s m2 (kN/m2) under these conditions if the tower is at atmospheric pressure. At the temperature of absorption the diffusion coefficient of SO2 is 0.116 104 m2/s, the viscosity of the gas is 0.018 mN s/m2 and the density of the gas stream is 1.154 kg/m3.