Study On The Doping Modification Of Calcium-based CO₂ Sorbents And The SO₂ Removal Characteristics Using Wasted CaO

As one of the main factor of the greenhouse effects,carbon dioxide has been paid more and more attention by scientists.Calcium Cyclic Decarburization has become a cheap and high effective carbon capture approach that has entered a large-scale and early stage of application,but the development of this technology is still face some technical difficulties,such as the decarburization efficiency of calcium-based sorbents will be greatly decreased,and unable to achieve long-term efficient circulation decarburization.In addition,the waste of calcium-based adsorbents will cause secondary pollution if it is not being disposed appropriately.In this paper,the research work carried out mainly based on the above issues.This paper is based on the traditional calcium-based decarburization adsorption cycle,the doping modification method is used to improve the sintering resistance of the synthetic decarburization adsorbent,increase the circulation stability of the sample.The effects of Element type?Ce/Yb/Mg/Ho?on the decarburization of calcium-based adsorbents were investigated by controlling the variables.The effects of various conditions on the decarburization of calcium-based adsorbents were investigated.At the same time,the decarburization performance of the samples was analyzed by theoretical analysis.And then,use the idea of "treating waste with waste" to make use of decarbonization waste for economic value under the premise of increase calcium-based adsorbent decarbonization economy in comprehensive.The idea of wet desulfurization of calcium-based decarburization waste was first proposed and the theoretical verification and characterization were carried out in fixed bed and gas-liquid reactor.Finally,the samples were characterized by scanning electron microscopy?SEM?,Micromeritics?BET?and other instruments.Research indicates:1)for the effect of element' doping and modification is Mg> Ce> Yb> Ho,in which Mg and Ce doped modified adsorbents have slightly better cyclic stability.Mg,Ce,Yb metal oxides dispersed in the calcium oxide grains between the inhibition of grain fusion,play a certain role in sintering,Ho elements are evenly distributed,but not the role of anti-sintering,EDS and SEM data verify above conclusions.2)The higher the CeO₂ content,the stronger the decarburization stability of the calcium-based sample.At low cycles,the decarburization of low CeO₂ content is better than that of high CeO₂ content because cerium itself is poor for CO₂ adsorption,but it can effectively improve the cyclic stability of calcium-based decarburization.Therefore,the higher the number of cycles,the higher the CeO₂ content,the higher the CO₂ adsorption capacity.Sol-gel method has a great advantage compared with coprecipitation method for calcium-based synthetic adsorbent preparation.The silica gel adsorbent prepared by sol-gel method has a more favorable microstructure,and the initial CO₂ adsorption performance and decarburization cycle performance of the sample are stronger.4)The technical scheme of wet desulfurization of calcium-based decarburization waste was first proposed and verified.Experiments show that decarbonization waste in a timely manner in the high cycle decarburization efficiency is low,there is still a good wet desulfurization efficiency.The exist of Mg has some effects on the wet desulfurization efficiency of natural calcium-based waste.The results show that the decarburization waste from dolomite can be higher than that of limestone-derived decarburized waste effectiveness.This is because the Mg element in the desulfurization generated when a large number of neutral particles to prevent the decline in PH,the cycle of maintaining a high PH so that the sample desulfurization performance better.5)When the number of cycles is less than 40,Ca L cycle has little effect on the removal performance of SO₂.When the number of calcium cycles exceeds 40,the desulfurization efficiency will decrease significantly,which may be due to the specific surface area and pore size changed with the increase of the number of cycles.And compared with the desulfurization effect and digestion conversion rate of experimental data found that the direct impact of digestion and conversion rate of the sample affected the desulfurization efficiency.In addition,it was found that the desulfurization efficiency when the sample size was less than 0.4 mm was obviously better than the efficiency of the samples whose size is larger than 0.4 mm.This is because the specific volume of calcium hydroxide is larger than the calcium oxide's,when the sample in contact with water for wet desulfurization,small particles can be faster cracking,and promote the progress of the reaction.The research results of this paper have enriched the research results of the decarburization direction of calcium-based recirculation,which has provided a lot of experimental basis and theoretical basis for the modified doping of calcium-based decarburization adsorbent and wetting and desulfurization of waste.The research has promoted the process of the Cyclic decarburization of this method from the theory into industrial production in some degree.