Catalytic Gasification of Crushed Coke and Changes of Structural Characteristics

The influence of the catalyzer on crushed coke gasification reactivity and its structural changes during steam gasification were studied in the present paper. Crushed coke samples were loaded with three kinds of catalysts, CaO, Na2CO3, and Fe2O3, and then dried at 950 °C. The coke gasified with steam in thermogravimetric analyser was used to study the influence of catalyzer loading on the gasification reactivity. Coke samples under different reaction times were prepared using a tube-type furnace. A specific surface area and porosity analyzer, an X-ray diffraction (XRD) apparatus, and a Raman spectra apparatus were used to characterize the structure of coke. A comparison of the reactivity of coke loaded with different kinds of catalyzers revealed that the coke with Na2CO3 exhibited higher gasification reactivity, and the optimum load of Na2CO3 on the coke was 5%. Brunauer–Emmett–Teller data showed that the addition of Na2CO3 can effectively corrode the pores on the surface of the coke to produce many small holes on the surface of the coke and widen the aperture of the coke. When Na2CO3 is added to the channel of the coke, the smaller porosity of the coke becomes more crowded. Coke loaded with Na2CO3 has a larger average pore diameter, which is more beneficial to the reaction with steam. Raman spectra analysis showed that the degree of graphite-like structures in the graphite layer increases as the reaction proceeds and that Na2CO3 inhibits the growth of large aromatic ring structures and decreases the content of graphite-like crystal structures. The XRD results suggested that some of the sodium atoms are inserted into the coke matrix and distort the orientation of carbon crystallites, thus effectively hindering the trend of carbon graphitization in the process of gasification. The XRD analysis result is in accordance with the results of Raman analysis.