Study On Reaction Characteristics Of CO₂Adsorptive Material At High Temperature In Fluidized Bed

Global warming and climate change have become the common concern ofinternational community. According to the latest data of the Global Carbon Project, theworldwide CO2emissions generated from the combustion of fossil fuel will rise to a recordhigh of36billion tons in2013,43%of which come from coal. Thus, it is an urgent concernto reduce the carbon emission of coal-fired power plant. Considering the great significanceof the CO2capture and recovery, domestic and international scholars have paid increasedattention on finding an economical and efficient CO2sorbents which can be used for hightemperature CO2adsorption in industrial fluidized bed.Kaolin, which is of great abundance and low price, mainly consists of SiO2and Al2O3.The existence of Al2O3can effectively alleviate the sintering of CaO. Therefore, kaolin waschosen as raw material of modified CaO sorbents in present study. Two different modifiedCaO sorbents were derived by directly adding calcined kaolin with (CaO/D) and withoutdesilicication (CaO/K) into CaO respectively. The adsorption properties and cycleperformance of the sorbents were tested in fixed bed and fluidized bed, and the resultsdemonstrated that CaO/K shows superiority in CO2cycling adsorption. In this work, X-RayDiffraction (XRD), X-ray fluorescence (XRF), Scanning Electron Microscope (SEM)and BET method were employed to characterize the modified adsorbents, and the resultsindicated that CaO/K has large specific surface area and pore volume. Subsequently, theeffect of particle size on the CO2adsorption properties of CaO/K adsorbent were studiedfluidized bed CO2. Laser Particle Size Analysis (LPSA) and BET method were used tocharacterize the modified sorbents after of1and20cycles of adsorption process, and theresults demonstrated that CaO/K adsorbent with larger particle size (>200μm) is morestable than the smaller ones (100-150μm and150-200μm) although its initial carbonation conversion rate is relatively lower. In addition, the temperature of the carbonation reactionalso influents on the CO2adsorption properties of CaO/K sorbent.Rice husk, an accessory of rice which distributes widely around the nation, contains alarge amount of SiO2and costs little. The ash of rice husk as well as kaolin were used toprepare the lithium silicate(Li4SiO4) adsorbents in this study. To test the cycle performanceof the sorbents, various experiments were performed and different characterization methodswere used. The results showed that both kaolin and rice husk ash can be used as the siliconsource for preparation of Li4SiO4sorbents. Due to the presence of K and Na, theun-pretreated rice husk ash shows superior CO2capture capacity and cycle performance.The effects of doped K and Na on the CO2capture characteristics of Li4SiO4were alsostudied in present study, and the results indicated that the doped K and Na are beneficial forthe CO2capture capacity of Li4SiO4.Fly ash, the solid waste from coal-fired power plants which contains large amounts ofSiO2, was also used to prepare Li4SiO4sorbents. Alkali metals K and Na were used tomodify the derived Li4SiO4sorbents. The results of adsorption experiments indicated thatthe addition of K increases the CO2capture capacity of Li4SiO4sorbents, while Na showsthe opposite effect, which may be caused by the existence of a certain amount of Na in thefly ash.