Effects And Mechanism Of Intercalation-exfoliation Modified Kaolin On Sodium Adsorption And Capture Under High Temperature

As a very promising potential power coal, Zhundong coal attracts wide attention. But its high content of Na causes serious fouling and slagging problems. Kaolin is an effective adsorbent of Na capture under high temperature. Coal additive proportion limit and the high content of Na in Zhundong coal is the key to restrict the use of kaolin in Na adsorption. Intercalation-exfoliation modified method apply to the field of nano materials can effectively improve the surface area, ion-exchange capacity of kaolin. Therefore, in order to improve adsorption efficiency of Na under high temperature, this paper aims to use intercalation-exfoliation modified kaolin as the Na adsorbent.The characterizations of intercalation-exfoliation modified kaolin such as functional bonds were studied to investigate the changes of its structure. The results showed that the layer space was enlarged, inner surface hydroxyl groups reduced due to the prototropy. The particles of modified kaolin became smaller, single layer structure appeared, the pore size and pore structure have increased significantly.Kaolin modified by four methods and NaCl mix-burning experiment were conducted to study its capture efficiency of Na under high temperature, the results indicate that modified kaolin can improve its adsorption ability of Na effectively, potassium acetate modified kaolin has the most significant effect, urea modification is second best. Modified kaolin is beneficial to the formation of insoluble Na because of more reaction sites caused by the loss of hydroxyl groups. The composition and structure of kaolin has changed duo to its preheating, which lead to the reduction of its adsorption capacity.Then modified kaolin was co-fired with Zhundong coal to research the effects of Na Capture in Zhundong coal.The results demonstrated that modified kaolin can effectively improve the efficiency of Na adsorption, particularly for the insoluble Na. The Na adsorption efficiency of Wanxiang coal increased by 50%, meanwhile adding modified kaolin was not change ash melting point significantly. Coal ash morphology became more delicate and scattered, more minerals with Na produced such as albite and glauberite.In summary, because of the loss of hydroxyl groups and increasing of pore size, intercalation-exfoliation modified kaolin can effectively improve the adsorption of Na in Zhundong coal under high temperature, at the same time, ash melting point was not significantly changed. Therefore, this method has good research and application prospect.