In Situ Observation of Coke Gasification and Behavior of Ash

Abstract

On the basis of the structure of pore distribution, the texture was classified into two regions, one was a dense structure originated from the inerts texture of coal, and the other was a foamed structure originated from the reactives. To clarify the gasification reaction and the high temperature behavior of ash in coke, the direct observation of the structures was carried out by high temperature laser microscope, μ-XRF and μ-XRD. The results were interpreted to explain the high temperature behavior of coke from the viewpoint of the macroscopic and microscopic scale.
The composition of ash was different according to the structures. The main components in ash of the dense structure were SiO₂, CaO and Al₂O₃. On the other hand in the foamed structure, S and Fe₂O₃ were main components. From the result of the direct observation of coke reaction in Ar atmosphere, some pore filled with a melted ash in the foamed structure was observed around 1000°C. While in 30%CO₂-Ar atmosphere, the melting behavior of ash was not observed in the foamed structure, however, the dense structure was covered by a melted ash. The morphology of the ash observed after gasification reaction was the plate type in one of the dense area, the spherical slags were also observed in the foamed structure and the part of the dense structure. Using μ-XRD, the crystalline size of graphite for the different structure was estimated by Sherrer's equation. The mechanism of growing of graphite crystal in high temperature was proposed.