The influence of simultaneous adsorption of potassium and sodium vapours on coke structure and performance

Alkali metals are one of the important factors promoting the degradation of coke in blast furnace. Previous studies usually focused on the properties of coke affected, respectively, by K and Na separately, while K and Na will simultaneously affect coke performance in the actual production of blast furnace. Through simulating the actual situation where coke is affected by K and Na vapours simultaneously in blast furnace, the evolution of coke structure and thermal properties (CRI, CSR) after alkalisation with different proportions of K and Na vapours are revealed in this study. Results showed that coke structure was broken when the proportion of alkali vapours reached 3%, and coke fine formation rate increased with the increase of K vapour, indicating that K vapour caused a great damage to coke structure; CRI of coke reached the highest and CSR the lowest when K/Na ratio was 3/7. It was observed with SEM/energy dispersive spectrometer that K and Na existed in both mineral matters and carbon matrix; nepheline, generated when coke reacted with alkaline (K, Na) vapours, was determined by XRD. The content of K and Na in nepheline is dependent on the ratio of alkaline (K, Na).