In-situ study of effect of migrating alkali metals on gasification reactivity of coal char

The migrating and diffusion of alkali metals affect catalytic gasification of coal char. The paper investigated in-situ gasification behaviors of coal char by TG and hot stage microscope, and studied catalytic performance of single NaAlO₂ particle and Na distribution by SEM-EDX. The results show that in the beginning stage, the curve of carbon conversion obtained by area method is consistent with that by TG method. In the ending stage, the ash in coal char acts as framework of the particles, as a result, area of the particles keeps unchanged. Meanwhile, the ash hinders diffusion of gasifying agent into coal char, and decreases the gasification rate, so carbon conversion rate calculated by area change is lower than that from TG. The single NaAlO₂ particle has catalytic performance. The coal char particles, which are closer to NaAlO₂, have higher gasification reactivity, because the amount of migrating alkali is higher. The migrating distance of NaAlO₂ is higher than 840 μm at 900 ℃ .