Ene rg y C o m e rs. Mgmr Vol. 36, No. 6-9. pp. 405-410, 1995 C o p yrig ht 0 1995 Else vie r Sc ie nc e Ltd zyxwvutsrqp 0196-8904(95)00031-3 Printe d in G re a t Brita in. A ll rig hts re se rve d O196-8904/ 95 $9.50 + 0.00 SEPARATION OF CO2 AND SO2 FROM FLUE GAS STREAMS BY LIQUID MEMBRANES A. Chakma Dept. of Chemical and Petroleum Engineering University of Calgary, Calgary, Alberta, CANADA T2N IN4 Abstract - Laboratory studies on the separation of CO2 and SO2 from gas mixtures by liquid membranes are reported. The membrane set-up consisted of an immobilized Polyethyleneglycol (PEG 400) membrane in series with another immobilized Diethanolamine (DEA)/PEG 400 membrane. SO;! was preferentially separated in the PEG 400 membrane while the DEA/PEG400 membrane separated CO2. Highest separation factors obtained for CO2 and SO2 were, 220 and 140, respectively. 1. INTRODUCTION Separation of CO2 from flue gas streams generated by existing power plants using present day technology is considered to be prohibitively expensive. Research is underway to find energy efficient means for CO2 removal from flue gas streams at laboratory and pilot scales. While the ongoing research efforts are likely to result in considerable energy savings over the existing processes, it is unlikely that the impact on the reduction of the overall cost for power generation will be significant. For example, a 20% improvement in the energy efficiency of chemical solvent based CO2 removal process may reduce the cost of CO2 removal by only lo- 12%. Therefore, despite the projected improvements in CO2 removal technology, the option of CO2 removal from power plant flue gas streams will remain an expensive proposition. Among the conventional CO2 removal processes, absorption by aqueous ethanolamine solutions is the most appropriate and cost effective option. However, this is an expensive option since the cost of CO2 separation may range from US$40-70 per ton of CO2 removed. There are many processes available for SO2 removal from power plant flue gases. Among them, the lime/limestone process is the predominant one. Nearly, all the conventional SO2 removal processes generate sludge that requires disposal. One radically different option is to separate both CO2 and SO2 in a single step process. If such a process can be found, it should then be possible to separate both these gases with minimum incremental cost. The presently available technologies for CO2 and SO2 removal are not compatible and can not be combined into a in a single process. Membrane senaration A novel approach that may provide considerable energy savings as compared to the conventional processes, is separation by membranes. Membrane separation alone or in combination with other processes may provide such an alternative process which is more energy efficient than the MEA process. Membranes are attractive because they do not require heat for their regeneration. However, gas separation membranes, in general, are pressure driven. Therefore, energy in the form of pressure drop must be expended for their operation. zyxwvutsrqponmlk 405