Preparation Conditions of Char via Pyrolysis of Low-rank Particulate Coal in Oxygen-containing Atmosphere

Physicochemical properties of char made by pyrolyzing a kind of low-rank particulate coal in O2-containing atmosphere and a quartz sand fluidized bed were investigated. The tested conditions included coal particle size, O2 concentration, pyrolysis temperature and residence time. The char with fixed carbon content over 82%(ω) and volatile matter below 7%(ω) was obtained by pyrolyzing the coal with particle size of 1～13 mm at the temperatures above 850℃ in the atmosphere with O2 content not below 3%(ψ) for pyrolysis time not shorter than 120 s. With the increase of temperature from 650℃ to 950℃, the corresponding interlayer spacing (d002) of the crystallite structure calculated from the XRD intensities was in the range from 0.383 to 0.372 nm, indicating a gradually condensed and ordered structure. BET specific surface area first increased then decreased with O2 concentration, and reached its maximum 242.71 m2/g at O2 7%(ψ), corresponding to the highest oxidation reactivity of char. The char produced via long-time pyrolysis in the O2-contaning atmosphere lowered the specific surface area and reactivity due to the burn-off of some formed pores.