摘要
MgO/MgCO_(3)碳酸化/再生反应作为典型的中温热化学储热技术,是实现可再生能源存储和工业余热回收利用的重要途径。碱金属熔盐修饰是提升MgO碳酸化和储热性能的重要策略。当前,尚缺碱金属熔盐修饰MgO在贴近中温储热实际应用场景下的性能评价。采用简单浸渍法制备碱金属熔盐修饰MgO多孔材料,采用N_(2)吸附-脱附、X射线衍射和扫描电镜对其微观结构特性进行表征分析。基于固定床反应器在低CO_(2)分压条件下考察了碱金属熔盐修饰MgO材料的中温储热性能,探究了熔盐类型和添加摩尔比对MgO碳酸化和储热性能的影响机制。研究发现:NaNO_(3)、LiNO_(3)和KNO_(3)熔盐修饰可有效提升MgO碳酸化和储热性能。NaNO_(3)修饰MgO材料的比表面积和孔体积较佳,且NaNO_(3)修饰有利于促进CO_(2)和MgO溶解,提供丰富的碱性O^(2-)活性位点强化化学吸附,并提供多孔结构促进CO_(2)和碳酸盐离子体相扩散,因而0.15LiNO_(3)-MgO碳酸化和储热性能相对较佳。随着NaNO_(3)熔盐摩尔比例由0.05提高至0.45,NaNO_(3)-MgO材料的碳酸化和储热性能均呈现先增加后降低的趋势。较低的NaNO_(3)摩尔比例对CO_(2)和MgO溶解与解离的促进作用受限,O^(2-)碱性活性位点密度有限,而NaNO_(3)添加比例过高易导致孔隙结构堵塞,对碳酸化和储热产生不利影响。NaNO_(3)熔盐的最佳摩尔比为0.15,其对应0.15 NaNO_(3)-MgO样品在300℃和10%CO_(2)气氛下CO_(2)吸附容量和储热密度分别高达8.21mmol CO_(2)/g和1.31MJ/kg。研究结果可为高活性MgO储热材料的定向制备及其中温烟气余热回收中的应用奠定理论基础。
The carbonation/regeneration reactions of MgO/MgCO_(3)working pairs as a typical intermediate-temperature thermochemical energy storage(TCES)technique,represents an important route towards renewable energy storage and industrial heat recovery.Alkali metal salts(AMS)promoting is one effective strategy to improve the carbonation and TCES performance of MgO.Currently,reports concerning the evaluation of the TCES performance of AMS promoted MgO under more realistic conditions are still lacking.In this work,AMS promoted porous MgO materials were prepared using the wet impregnation method,and their microstructure properties were characterized by N_(2)adsorption-desorption,X-ray diffraction(XRD)and scanning electron microscopy(SEM).Intermediate-temperature TCES performance of the materials was evaluated under a low CO_(2)partial pressure using a fixed-bed reactor,and the effects of different molten salts and the molar ratio of molten salts on the carbonation and heat storage performance were investigated.Results indicated that the addition of NaNO_(3),LiNO_(3)and KNO_(3) worked satisfactorily in promoting the carbonation and TCES performance of MgO.The sample modified with NaNO_(3)showed better carbonation and heat storage performance.This was associated with their relatively higher specific surface areas and pore volumes and the fact that NaNO_(3)had promoted the dissolution and dissociation of CO_(2)and MgO.These had endowed MgO with abundant O^(2-) basic active sites for enhanced chemisorption and afforded porous structures for promoted bulk diffusion of CO_(2)and carbonate ions.With the increase in the molar ratio of NaNO_(3), the carbonation capacity and heat storage density increased first and then decreased. When the molar ratio of NaNO_(3) was low, its promoting role in CO_(2) and MgO dissolution and dissociation was limited and the density of O^(2-) basic sites was rather low. A higher NaNO_(3) molar ratio would result in pore structure blockage which would also adversely affect the carbonation and TCES perform
作者
郭亚飞
吴佳毅
檀畅
郑宇航
张李纪
赵传文
GUO Yafei;WU Jiayi;TAN Chang;ZHENG Yuhang;ZHANG Liji;ZHAO Chuanwen(School of Energy and Mechanical Engineering,Nanjing Normal University,Nanjing 210023,China)
出处
《电力科技与环保》
2022年第3期157-165,共9页
Electric Power Technology and Environmental Protection
基金
国家自然科学基金(51806108)。
关键词
碱金属熔盐
多孔MgO
碳酸化反应
中温热化学储热
储热密度
alkali metal molten salts
porous MgO
carbonation reaction
intermediate-temperature thermochemical energy storage
heat storage density
