Initial Deposition Feature during High-Temperature Pressurized Pyrolysis of a Typical Zhundong Coal

Abstract

This work clarifies the diffusion and initial deposition behavior of volatilizable elements during pressurized pyrolysis of a typical Zhundong high-basic (i.e., high proportion of alkali and alkaline earth metallic species, AAEMs) coal. The concentrations of AAEMs in raw coal and its derived char as a function of pyrolysis temperature and pressure were duly measured; besides, the features of innermost deposit in specific areas of pyrolysis reactor were particularly investigated. The release of AAEMs was strongly related with their occurrences in coal. Specifically, Na, mostly in a water-soluble form in raw coal, still existed as solid and/or liquid phase below 1000 °C and thus could be partially adsorbed and retained in the porous structure of char, which could be enhanced by elevated pyrolysis pressure with the average weight loss of Na in the range of 16.0–29.1 wt %. Nevertheless, the diffusions of K (6.8–17.3 wt %), Ca (16.4–29.7 wt %), and Mg (10.7–21.2 wt %) were substantially dependent on the decomp...