Removal of CO2 from indoor air by alkanolamine in a rotating packed bed

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 CO2 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 Na2SO3 (oxygen scavenger) content in solution on CO2 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 CO2. An algebraic model comprising stirred tanks connected in series and followed by a gas-liquid contactor was employed to simulate CO2 removal in the operation. The calculated results associated with the 6-tank in series model showed a satisfactory agreement with the experimental exit CO2 concentrations, with a deviation of less than 7.5% in average. (C) 2011 Elsevier B.V. All rights reserved.