Experimental and kinetics study of NO heterogeneous reduction on semi-coke and its chars: Effects of high-temperature rapid pyrolysis and atmosphere

The high-temperature rapid pyrolysis has an evident impact on NO heterogeneous reduction over semi-coke char, which is rarely reported before. This study systematically evaluated the reactivity and kinetics of NO reduction over semi-coke and its rapid pyrolysis chars with the presence of O2 and CO using a fixed-bed reactor. The experimental results showed that the rapid pyrolysis at a desirable temperature of roughly 1100 °C can promote NO reduction over semi-coke, but excessively high and low pyrolysis temperatures were unfavorable for char-NO reaction. Partially explaining the situation was the trend of a rise before fall in specific surface area and C–O bond content of char with the rising pyrolysis temperature. The rapid pyrolysis char formed above 1100 °C showed lower activation energy than the fixed-bed pyrolysis char by 24.10%, but the higher one by 12.55% at 900 °C. The presence of CO noticeably promoted the NO reduction and reduced the activation energy by up to 41.73% at 0.75% CO, while the addition of oxygen inhibited NO reduction over semi-coke char. The suitable pyrolysis temperature with the presence of CO favored NO reduction over rapid pyrolysis char, which guided semi-coke utilization as a fuel or reducing agent.