ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Gasification reactivity and morphology of coal chars formed in N₂ and CO₂ atmospheres

Yun Liu, Yan-Jun Guan, and Kai Zhang

North China Electric Power University, Beijing, China

E-mail: kzhang@ncepu.edu.cn

Abstract: In this study, chars derived from Zhundong coal were prepared in a tubular reactor under CO₂ and N₂ atmospheres in the temperature range 500–800 °C. The structure features of char were proven using scanning electron microscopy, X-Ray diffraction, N₂ adsorption analyzer and Raman spectroscopy. Besides, the correlations of structure features and gasification reactivity of coal char were also investigated. The results reveal that char yield during devolatilization under CO₂ atmosphere is relatively lower than that under N₂ atmosphere, which could be attributed to heterogeneous reactions of CO₂ with tar and char under CO₂. The char formed in CO₂ atmosphere exposes more pores in char matrix accompanied by the rough surface, resulting in a higher specific surface than that obtained under N₂. Additionally, the char formed under CO₂ atmosphere has lower degree of graphitization and higher ratio of small to large aromatic ring systems, compared to that obtained under N₂. As a result, the gasification in a thermo-gravimetric analyzer indicates that the char prepared under CO₂ is more reactive, due to more amorphous carbon structures formed under CO₂. The homogeneous and heterogeneous reactions of CO₂ with gases, tar and char occur when CO₂ is introduced in the pyrolysis process. Moreover, the introduction of CO₂ changes morphology of char, since CO₂ participates in reaction process on the char surface, resulting in promoting the gasification reactivity.

Keywords: CO₂ atmosphere ; Pyrolysis ; Char structure ; Reactivity ; N₂ atmosphere 

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-018-0423-9

Chemical Papers 72 (8) 2045–2054 (2018)