The high sodium content in Zhundong coal results in severe slagging, ash deposition, high-temperature corrosion, and particle emission problems during utilization. Kaolin is a common in-furnace additive for the removal of sodium and alleviation of such issues. In this study, a novel modification method, namely, intercalation-exfoliation combined with acid leaching, was applied to improve sodium adsorption efficiency of kaolin, with kaolin modified by intercalation-exfoliation and raw kaolin as a comparison. With combustion experiments and alkali metal vapor adsorption experiments, the effects of surface modification, combustion temperature, and blending ratio of kaolin adsorbents on sodium adsorption efficiency as well as the temporal profiles of alkali metal vapor adsorption processes fitted by four adsorption kinetic models were obtained. Experimental results showed that kaolin modified by the novel method displayed the best sodium adsorption performance, whose alkali metal vapor adsorption process was mainly controlled by intra-particle diffusion. In contrast, controlling steps of raw kaolin and kaolin with intercalation-exfoliation were external mass transfer and chemisorption on the surface, respectively. Such results arised from the amorphous transformation of crystal structure, increased adsorption sites after dehydroxylation, generation of free active silica with inner surface partly destroyed by acid, and loose scaly structure with expanded pore volume. Lower combustion temperature and higher blending ratio of kaolin were favorable for sodium adsorption. It was also found that kaolin additive caused a decrease in ash fusion temperatures (AFTs), and such tendency could be alleviated to some extent by the novel modification method. The blending ratio of kaolin should be determined according to the slag discharge mode (solid/liquid) during combustion. Kaolin modified by the method of intercalation-exfoliation combined with acid leaching had the best performance concerning sodium adsorption capacity and alleviation of slagging tendency, implying a broad application prospect.

准东煤中的高钠含量会导致严重的结渣，灰烬沉积，高温腐蚀以及在使用过程中产生颗粒物排放的问题。高岭土是一种常见的炉内添加剂，用于去除钠和减轻此类问题。本研究采用插层剥落结合酸浸的新型改性方法，以提高高岭土的钠吸附效率，以插层剥落改性的高岭土与生高岭土为比较。通过燃烧实验和碱金属蒸气吸附实验，获得了表面改性，燃烧温度和高岭土吸附剂的混合比对钠吸附效率的影响，以及通过四个吸附动力学模型拟合的碱金属蒸气吸附过程的时间分布。实验结果表明，新方法改性的高岭土表现出最好的钠吸附性能，其碱金属蒸气吸附过程主要受颗粒内扩散控制。相反，生高岭土和高岭土的插层-剥离控制步骤分别是外部传质和表面化学吸附。这些结果来自晶体结构的无定形转变，脱羟基后吸附位点的增加，内表面被酸部分破坏的游离活性二氧化硅的生成以及孔体积扩大的鳞片状松散结构。较低的燃烧温度和较高的高岭土混合比有利于钠的吸附。还发现高岭土添加剂导致灰分熔化温度（AFTs）降低，这种趋势可以通过新颖的修改方法得到一定程度的缓解。高岭土的混合比应根据燃烧过程中的排渣方式（固/液）确定。插层剥落结合酸浸改性的高岭土在钠吸附量和缓降结渣方面表现最佳，具有广阔的应用前景。