Evaluation of catalytic combustion of pulverized coal for use in pulverized coal injection (PCI) and its influence on properties of unburnt chars

• Effect of catalysts on pulverized coal combustion at high heating rates was investigated.
• Variation on structure of unburnt chars including particle size, surface area, pore structure, and chemical structure with catalysts addition was identified.
• The reactivity of unburnt chars after catalytic combustion was evaluated.

In order to investigate the influences of applying catalysts on pulverized coal injection (PCI) and blast furnace (BF) operations, the catalytic combustion of two kinds of pulverized coals by three oxides (MnO2, CaO and Fe2O3) was simulated by using a drop tube furnace (DTF), and variation of structures as well as the reactivity of unburnt chars were examined. For bituminous, the relative active sequence of catalysts to the burnout rate was: CaO > Fe2O3 > MnO2. For anthracite, it is as follows: Fe2O3 > CaO > MnO2. These three catalysts exhibited better catalytic effect on anthracite than bituminous coal. In addition, the structural study results imply that the chemical reactions on char particle and pore surface were enhanced greatly by catalysts. On the other hand, the X-ray diffraction analysis shows that chars became more ordered with catalysts addition. Nevertheless, unburnt chars formed from catalytic combustion still have a higher reactivity than pure unburnt char, which is most probably due to the lower activation energy. Consequently, these results imply that the catalytic combustion in PCI operation facilitates the combustion process of pulverized coal in raceway, as well as the following consumption of unburnt char out of raceway.