Structure and reactivity of chars prepared from low-volatile coal under O2/N2 and O2/CO2 conditions in a flat-flame assisted entrained flow reactor

Accurate assessment of the structural characteristics and reactivity of coal char is crucial for the design of burners. Chars from low-volatile coal were prepared under O2/N2 (ON) and O2/CO2 (OC) conditions in a flat-flame assisted entrained flow reactor, with bituminous coal as a reference. Both the heating rate and residence time were carefully selected to mimic the conditions used in actual industrial boilers. The physical-chemical structures and reactivities of all chars were characterized using Raman and FTIR spectrometers and thermogravimetric analysis. The physical structure results indicated that a high CO2 content inhibited the char yield and specific surface area of chars from low-volatile anthracite coal, while, for chars from high-volatile bituminous coal, CO2 increased the char yield and specific surface area. For chemical structures, the degree of disorder in the carbon skeleton structures and active functional group contents of all chars prepared under OC conditions were greater than those of chars prepared under ON conditions. Moreover, the apparent reactivity results demonstrated that the physical structure characteristics of coal char played a leading role in the apparent reactivity under investigative conditions.