Article pubs.acs.org/EF
Initial Deposition Feature during High-Temperature Pressurized Pyrolysis of a Typical Zhundong Coal Xiongchao Lin,*,† Yuanping Yang,† Sasha Yang,† Shouyi Li,† Yajun Tian,*,‡ and Yonggang Wang† †
School of Chemical & Environmental Engineering, China University of Mining and Technology (Beijing), D11 Xueyuan Road, Haidian District, Beijing 100083, PR China ‡ National Institute of Clean-and-Low-Carbon Energy, Beijing 102211, PR China 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 decomposition of minerals and the diffusive force of volatiles. The species (mainly Na, K, Ca, Mg, S, and Cl) in the pyrolysis gas were responsible for the generation of corrosive aerosol during the pyrolysis of high-basic coal. Elements with various forms in the aerosol could mutually combine and form deposition precursor (mainly as NaCl, Ca−S−O, MgO, Na−S− O, etc.). The deposits were shaped at lower temperature (
