Influence mechanism of alkali metals on CO2 gasification properties of metallurgical coke

In order to clarify the function mechanism of alkali metal on degradation of metallurgical coke in blast furnace, the influence of alkali metal potassium and sodium on carbon structure change was investigated by gaseous adsorption method, and also the catalytic gasification reaction behaviors of alkali metal adsorbed coke samples was further studied. The results showed that the alkali metal vapor absorbed on coke has significant degradation effect on high temperature metallurgical properties of coke, which has catalytic effect and significantly increases gasification reactivity, and the catalytic limit of potassium vapor and sodium vapor was about 5% and 3%, respectively. Besides, potassium adsorption could also cause more fine coke particles to be produced, further aggravating degradation of coke in blast furnace. The analysis of physicochemical structures of different samples shows that the destruction of aromatic ring structure with dense and stable carbon structure in coke by alkali metal vapor adsorption process was the essential cause of coke reactivity increase and fracture. Kinetics analysis study shows that the random pore model (RPM) has the best performance representing the catalytic gasification process, and for different samples the activation energy first increases and then decreases with the increase of alkali metal adsorption content. It was also confirmed that there existed the kinetic compensation effect in the gasification process.