Adsorptive Separation Of Carbon Dioxide

With the development of economy, enrichment of atmospheric greenhouse gases,mainly carbon dioxide, resulted from human activities has increased global meantemperature. Because most of the carbon dioxide is emitted from coal-fired power plantsand about80%of global energy supply will still rely on fossil fuels in the future, the studieson CO₂capture from the flue gas are very important.The main components in the flue gas are CO₂and N₂, so the separation between CO₂and N₂is the key. The methods so far presented for the capture of flue gas CO₂includesbsoption, adsorption, membrane separation and the separation at low temperature. Thechemical absorption of CO₂with aqueous solutions of amines is presently the mosteconomical one, but there are some problems with equipment corrosion, amine lost andhigh-energy cost. The adsorption method bearing advantange in simple equipment,low-energy cost, wide range of pressure and temperature has been the most potentialmethod for the CO₂capture.The adsorbent is the core of adsorption, which determines the separation performance.So the paper studied the separation coefficients of twelve adsorbents, and the influences oftemperature, surface polarity, specific surface area and pore size on the separationperformance are presented, firstly.Because CO₂could be adsorbed with the occurrence of multi-layer adsorption andcapillary condensation, while N₂adsorbed with the single molecular adsorption undernormal temperature, so the researches on whether the change of adsorption mechanismcould enhance the separation performance of CO₂and N₂under high pressures areobservated.Secondly, in order to enhance the separation performances of adsorbent, adsorbentsSG-A and SG-B are modified with different amines. The effects of amine-loading andtemperature on the separation between CO₂and N₂are investigated, and the regenerationand stability are also researched at normal temperature. The results show thatamine-modified adsorbents could enhance the separation performances. And the modifiedadsorbents with TEA or MDEA have a good regeneration at normal temperature, but withDEA couldn’t.At last, the effects of water on the separation coefficient between CO₂and N₂withloading different amines are presented. The results show that the presence of water could enhance the separation of CO2and N₂, and the modified adorbents with TEA or MDEA alsocould be regenerated in the presence of water.