Pilot-Scale Experimental Study on the CO2 Capture Process with Existing of SO2: Degradation, Reaction Rate, and Mass Transfer

A lab amine-based chemical absorption pilot plant for CO2 capture from coal-fired power plants was built. The character of CO2 capture of the new blended amine absorbent was studied in the pilot plant, under the condition of prolonged operation. Three campaigns were conducted. One campaign was the baseline experiment to evaluate the cyclic absorption and desorption character of the absorbent during 500 h with 12 vol % CO2 and 18 vol % O-2. Other two campaigns were performed to evaluate the influence of SO2 on the absorption character of the absorbent, with 214 and 317 ppm SO2, respectively. The CO2 reaction rate and mass transfer behavior were analyzed for the three campaigns. The results show that the CO2 removal efficiency is in inverse proportion to reaction time, and the results of amine degradation and heat stable salts formation are in accordance with it. The SO2 removal efficiency is almost 100%. After the addition of SO2 to the simulated flue gas, there is more serious amine degradation and more heat stable salts formation. Four kinds of organic acid salts, such as formate, acetate, oxalate, and glycolate, were detected with and without SO2. The analysis on mass transfer and CO2 reaction rate indicates that the free amine concentration reduction is the main reason for the CO2 removal efficiency decreases. The combination of SO2 with amine results in the decrease in free amines.