Study On The Sorption Performance And Failure Mechanism Of Compound CO₂ Sorbent

The large amount of CO₂ emissions has led to a series of problems such as global warming,melting of glaciers,and frequent extreme weather,and it is imperative to capture CO₂ on global large-scale.Among many post-combustion capture technologies,solid adsorbent technology for CO₂ capture has become one of the current research hotspots due to its good compatibility with existing coal-fired power plants,high adsorbent recycling efficiency,and no corrosion to equipment and other advantages.However,the investigation of solid adsorbents with excellent CO₂ adsorption capacity and cycle characteristics is still insufficient;there are few reports about the study on the failure mechanism and competitive adsorption between CO₂ and SO₂ on solid adsorbent.Therefore,this paper has done some work on the following aspects.Based on above issues,the specific research was included in the following aspects:The preparation process of sodium-based adsorbent and amine-based adsorbent was optimized,and the CO₂ sorption performance and cyclic characteristics of the two types of adsorbents were studied.Results show that the CO₂ adsorption capacity of sodium-based adsorbent prepared by dry-impregnation method is higher than that of adsorbents prepared by wet-impregnation method.The CO₂ adsorption capacity of the adsorbent is the highest at the reaction temperature of 50?.When TEOS:APTES:H₂O molar ratio was 1:2:3 and deionized water was added in two steps,the carbonation reaction and cyclic characteristics of the amine-based adsorbent were excellent.The optimal reaction temperature of the adsorbent is50?.CO₂ concentration will affect the carbonation reaction rate of the amine-based adsorbent,but the final CO₂ adsorption capacities of different CO₂ concentrations have little difference.Due to the different reaction paths,the CO₂ adsorption capacity of the amine-based adsorbent reacted in the atmosphere containing water vapor is higher than that in water-free vapor atmosphere.The negative effect of SO₂ on Na₂CO₃/Al₂O₃ for CO₂ capture and the corresponding mechanism were investigated in the fixed-bed reactor.Results show that when the reaction atmosphere contains SO₂,the difficultly decomposed by-product?Na₂SO₃?reduces the utilization of Na₂CO₃,thus significantly decreasing the CO₂ adsorption capacity,and consequently,the cyclic characteristics were seriously affected.Besides,the pore distribution of sorbent has also changed.The lower the CO₂ concentration,the slower the decline trend of CO₂ adsorption capacity of adsorbent with the increase of cycle number.The negative effects on cyclic characteristics of adsorbents are more serious severer with increase of SO₂concentration,but while the total conversion rate of adsorbent is improved.The reaction competition between adsorbent and CO₂ was the strongest at 50?.The selectivity adsorption coefficient of CO₂ is the highest at the temperature of 50?.The negative effect of SO₂ on APTES/TEOS for CO₂ capture and the corresponding mechanism were investigated in the fixed-bed reactor,and partial kinetic parameters were obtained on TGA.Results show that SO₂ can react with amine-based adsorbents and its carbonated reaction products to form sulphite or sulfate by-products which are difficult to decompose,thus the CO₂ adsorption capacity,cyclic characteristics and pore distribution of sorbent were seriously affected.In addition,the deactivation caused by SO₂ under water vapor atmosphere is severer than that without water vapor.The thermogravimetric test shows that the activation energies of chemical-reaction controlled region and diffusion-controlled region of carbonation reaction were 31.39 kJ·mol^-1and 54.07 kJ·mol^-1,respectively.The two-region activation energies of the sulfation reaction were 7.62 kJ·mol^-1 and 36.05 kJ·mol^-1,respectively.Results show that properly increasing the CO₂ concentration,decreasing SO₂concentration can increase the CO₂ sorption competitiveness of the sorbent.When the reaction temperature is between 30°C and 50°C,the decrease of CO₂ adsorption capacity is more significant with increasing temperature.When the reaction temperature is between 60?and 70?,the decreasing trend of CO₂ adsorption capacity of adsorbent slows down with the increase of temperature.