Effect of Semi-Char Content on Oxygen-Enriched Co-Combustion Behaviors of Lignite and Semi-Char

Oxygen-enriched combustion experiments of individual samples (lignite and semi-char) and their blends were conducted using a thermogravimetric analyzer. The semi-char sample was prepared from Baorixile (BL) lignite under a pyrolysis temperature of 800 degrees C. The differences between semi-char and BL lignite in terms of thermal behaviors and combustion dynamics were investigated. Subsequently, the combustion reactivity corresponding to three ratios of BL lignite to semi-char was analyzed. Results showed that the yield of volatiles from BL lignite was proportional to oxygen concentration below the ignition temperature, whereas that from semi-char was nearly constant. The degree of conversion of semi-char has remained unchanged in each reaction region under different oxygen concentrations. The reduced rate of activation energy of semi-char combustion was larger than that of BL lignite below degree of conversion 0.6. These findings indicated that semi-char can maintain the combustion stability of blends. Further studies found that the thermal interaction between semi-char and lignite resulted in the optimum combustion stability when the proportion of semi-char was from 30 to 50%.