Evaluation of oxygen partial pressure, absolute pressure, and heating rate effects on the thermochemical conversion of a low volatile coal

Understanding the thermochemical conversion of pulverized coal (PC) in the blast furnace raceway zone is essential for improving coal utilization and process efficiency. However, determining kinetic parameters under raceway conditions remains challenging because direct measurements at high temperatures, pressures, and heating rates are limited. In this study, the Alternative Reducing Agents (ARA) reactor was used to investigate the pyrolysis and combustion behavior of a low volatile coal under raceway relevant conditions. Separate experimental series were conducted by systematically varying oxygen partial pressure, absolute pressure, reactor temperature, and particle heating rate. The heating rate effect was evaluated by operating the reactor with and without a hydrogen burner positioned at the particle injection point. Burner activation increased the particle heating rate by a factor of 2 to 4 and raised the local gas temperature. Absolute pressure reduced pyrolysis rates at low heating rates, while this effect is negligible at high heating rates. Significant effects of temperature on the pyrolysis rate were observed until 1200 ∘ C, whereas an increase to 1400 ∘ C had only a minor effect. No clear trend was observed for the heating rate effect on pyrolysis. Under combustion conditions, burnout increases at higher oxygen partial pressures and temperatures, while a minor effect of the absolute pressure was also observed. Heating rate effects were hard to evaluate due to a simultaneous temperature increase in the gas stream. Determining reaction orders for coal oxidation yielded different results between experiments with and without the burner. Reaction orders for oxygen between 0.7 and 0.8, and between 0.5 and 1.12 were determined for low heating and high heating rates, respectively, at the different experimental temperatures. Additional comparison data from ARA experiments and blast furnace injection are required before ranking PC is possible.