Influence of Surface Modification on Combustion Characteristics of Charcoal and Its Performance on Emissions Reduction in Iron Ore Sintering

Abstract

For bridging the huge gap of combustibility between coke breeze and charcoal in iron ore sintering, the influences of using SiO₂ and B₂O₃ as modifiers on combustion characteristics of charcoal were investigated. The results showed that due to the physical barrier function of SiO₂ powders and the surface covering function of B₂O₃ film, the porosity of modified charcoal was reduced. The combustion speed of modified charcoal was therefore slowed down and showed less differences to coke breeze than non-modified charcoal. Recommended mass percentages of SiO₂ and B₂O₃ in modified charcoal were 2% and 3% respectively. The combustion reaction activation energy of charcoal was increased from 55.54 kJ∙mol⁻¹ to 86.97 kJ∙mol⁻¹ and 92.82 kJ∙mol⁻¹ respectively after modification, which was close to 122.75 kJ∙mol⁻¹ of coke breeze. Laboratory-scale sintering tests showed that the proper replacement percentage of charcoal to coke breeze was increased from 20% to 40% after the surface modification. And the emission reduction percentages of NOx and SOx were correspondingly improved from 16.58% and 11.02% to about 28% and 37% respectively, while the average combustion efficiency was kept at the comparable level to the case using coke breeze only.