CO₂ Adsorption Of Flue Gas Desulfurization Gypsum Modified Solid Amine Adsorbents

In recent years,with the rapid development of industrialization and urbanization,the global carbon dioxide emissions have maintained a rapid growth trend,resulting in a series of environmental problems,such as climate warming,tropical storms,and sea-level rise.These problems were threaten the global ecological balance.About30%-40%of CO₂ emissions were produced by coal-fired power plants each year,and most of which were attributed to the combustion of fossil fuels.Therefore,Capturing CO₂ from the flue gas of coal-fired power plant is of great concern.Carbon dioxide capture by adsorption has great development prospects.Developing an adsorbent with high adsorption capacity,fast adsorption rate,high selectivity and stable performance is the key to capture CO₂.By loading liquid organic amines on porous solid carriers,solid amine adsorbents have the advantages of high selectivity,low energy consumption and low corrosivity to the equipment,which had attracted much attention.On the basis of the research on the CO₂ adsorption performance of water vapor into the adsorbent,this paper attempts to add flue gas desulfurizing gypsum（FGDG）to adsorbents to investigate the CO₂ adsorption properties of adsorbents containing water.The main research conclusions are as follows:1 The biochar（BC）was prepared by carbonization of durian shell and then used as the carrier material of the adsorbents together with silicium-calcium slags.The mixtures of BC and silicium-calcium slags particles were firstly impregnated with the Pentaethylenehexamine（PEHA）liquids,and then were mixed with wet flue gas desulfurization gypsum（FGDG）slags to obtain the aqueous amine functionalized CO₂solid adsorbent.The CO₂ adsorption properties of adsorbents were promoted by the addition of FGDG,the presence of water in FGDG slags changed the reaction mechanisms between amino groups and CO₂.The adsorbent with 30%content of FGDG slags has a maximum adsorption capacity of 2.33 mmol·g^-11 when the adsorption temperature was 85℃.In the multi-cycle adsorption-desorption tests,the adsorption capacity only decreased by 7.3%after 12 cycles,showing a favorable adsorption stability.The thermodynamics and kinetics of CO₂ adsorption on FGDG modified BC/SCS-PEHA were studied.The isosteric heat value of CO₂ adsorption was calculated based on Clausius-Clapeyron equation between the physical and chemical adsorption heat,suggesting the simultaneous occurrence of physical and chemical effects in adsorption process.The Avrami model can fitted well the experimental data,which further verified The physical and chemical effect of adsorbent on CO₂ molecule.2 A mixture of PEHA and MDEA modified BC/SCS-FGDG sorbents were prepared by the wet impregnation method.The CO₂ adsorption performances were investigated.Hydrogen bonds and other interactions between PEHA and MDEA promote the dispersion of PEHA and reduce the diffusion resistance of CO₂.At the same time,MDEA,as a tertiary amine,could react with CO₂ in the presence of water,improving the CO₂ adsorption performance.The results showed that the maximum CO₂ adsorption capacity was 2.95 mmol?g^-11 of BC/SCS-FGDG-15%PEHA/15%MDEA at the adsorption temperature of 80℃and influent velocity of 30 mL?min^-1.After a twelve-cycle,the CO₂ adsorption capacity only decreased by 4.2%.It illustrated that BC/SCS-FGDG-15%PEHA/15%MDEA had excellent regenerability.Frenudlich model and Temkin model were applied to simulate the results of CO₂adsorption on BC/SCS-FGDG-30%PEHA and BC/SCS-FGDG-15%PEHA/15%MDEA respectively.The fitting degree of Frenudlich model to both of them was higher,andthefittingresultofchemicaladsorptionmodelTemkinto BC/SCS-FGDG-15%PEHA/15%MDEA was better than the fitting result of BC/SCS-FGDG-30%PEHA,which shows that the addition of MDEA enhances the chemisorption of adsorbents.3 BC/SCS-FGDG was modified by the mixture of PEHA and K₂CO₃.The adsorbent with 20%content of K₂CO₃ has a maximum adsorption capacity of 2.91mmol·g^-1when the influent velocity was 30 mL·min^-1and the adsorption temperature was 80℃,showed the excellent performance.The addition of K₂CO₃ in the adsorbent promoted the adsorption of CO₂.K₂CO₃ acted with CO₂ molecules under water conditions,which promoted the formation of bicarbonate.In the multi-cycle adsorption-desorption tests,the adsorption capacity of BC/SCS-FGDG-PEHA/20%K₂CO₃ only decreased by 4.5%after 12 cycles,showing a favorable adsorption stability.