The goal of this experiment was to determine the gas-side and liquid-side mass transfer coefficients for a stirred tank system, and then compare the values obtained to the theoretical mass transfer values. This was done using a stirred tank apparatus that measured the carbon dioxide dissolution rate in water. Theory: The two-resistance theory models the transfer of material between two contacting phases.
In the situation where a component is being transferred room a liquid film to a gas film the rates of diffusion in the z direction can be described by the equations: Equation 1 Equation 2 where keg is the convective mass transfer in the gas phase and kill is the convective mass transfer in the liquid phase. In steady state conditions Equation 1 and Equation 2 can be set equal to each other such that, Equation 3 This equation shows the dependence of the diffusion rates on concentration gradients.
This is visually represented in Figure 1. Figure 1 The ratio of the two convective mass transfer coefficients may be obtained room equation 3 by rearranging is to give: Equation 4 In this experiment the concentration of CA will be found by taking the pH, this is possible due to the reaction between CA and water. Equation 5 Equation 6 Equation 7 Equation 8 Equation 9 The equilibrium concentration can be found using Henrys Law, seen below: Equation 10 where H is Henrys constant and APPC is the partial pressure of carbon dioxide.
Using this and the reactions we get, Equation 11 Equation 12 Then there will be enough information to solve for the mass transfer coefficient using, Apparatus: Procedure: To perform the lab first flush the System with air by opening the air valve and release valve and closing the CA valve. Then flush it with water by closing the release valve and turning the water on. Once the system is totally flushed close the air valve and open the CA valve.