Removal of CO 2 from indoor air by alkanolamine in a rotating packed bed

Abstract

An aqueous solution containing 30 wt.% of either monoethanolamine (MEA) or diethylenetriamine (DETA) mixed with piperazine (PZ) was proved to be an effective absorbent in a rotating packed bed (RPB) reducing CO 2 concentration from 1000 ppm to a level much less than 100 ppm over a long period of time. The effects of temperature, rotating speed, gas flow rate, liquid flow rate, PZ content in solution, and the Na 2SO 3 (oxygen scavenger) content in solution on CO 2 removal efficiency and dissolved oxygen (DO) content in solution were studied, using a factorial design technique. Gas flow rate was found to be the most dominant factor affecting overall mass transfer coefficient ( K G a), height transfer unit (HTU), and DO value. In addition, K G a and HTU corresponding to the most appropriate operating conditions were found to be higher than 5.8 s −1 and smaller than 1.0 cm, respectively, demonstrating the performance superiority of a RPB as compared with a conventional packed bed. The measured value of DO in solution showed the need for an O 2 scavenger and the impediment of oxygen dissolution by CO 2. An algebraic model comprising stirred tanks connected in series and followed by a gas–liquid contactor was employed to simulate CO 2 removal in the operation. The calculated results associated with the 6-tank in series model showed a satisfactory agreement with the experimental exit CO 2 concentrations, with a deviation of less than 7.5% in average.