Absorption and Desorption of CO_2 by Amine-Promoted Hot Potash Solution

The approximate solution for the rate equation of CO_2 absorption and desorption as stated in the title has been derived through theoretical analysis; the effect of different equilibrium concentrations of absorbed gas in parallel reactions on the mass transfer driving force having been taken into account. To verify the solution, an experiment was carried out in a stirred reactor with diethanolamine as the promotor at 353 K for absorption and 373 K for desorption under pressure of 0.104 MPa. It has been shown from the calculation that most of the free amine consumed in the shuttle mechanism of aminepromoted absorption is regenerated in the film. The depletion of free amine at the interface reduces the driving force, and hence decreases the absorption rate significantly; but this depletion is limited by the interface equilibrium concentration of CO_2. The absorption rate can be raised by accelerating the regeneration of free amine. The promotion by amine in desorption is not definitely put into effect via homogeneous catalysis. The mechanism of promotion in desorption is much the same as in absorption.