Numerical investigation of nanosecond plasma-assisted ignition in blast furnace gas

Abstract

The ignition delay of blast furnace gas (BFG) and air mixtures is numerically investigated in a constant-pressure reactor employing plasma-assisted ignition. Given the absence of a well-established chemical kinetic mechanism for plasma-assisted ignition in BFG and air mixtures, this study develops a mechanism by integrating well-validated plasma kinetics reactions involving CO2 with CO and H2, along with pre-existing plasma kinetics for air. The study explores the influence of various factors on ignition delay time, including the reduced electric field, the number of nanosecond pulses, equivalence ratio, and molar fraction of hydrogen. It is found that the utilization of nanosecond pulsed plasma results in a notable enhancement of the ignition delay time in BFG. Under lower reduced electric field conditions, the vibrational states of N2 predominantly contribute to the generation of O radicals. Increasing the number of nanosecond pulses facilitates the ignition in BFG and air mixtures while maintaining the same overall deposition energy. Ignition occurs more rapidly in fuel-rich mixtures due to the elevated accumulation of O, H, OH radicals during the final nanosecond pulse in rich mixtures. When the H2 concentration is elevated to 3 %, the electron impact reaction H2 + e → e + H + H becomes a more significant source of H radicals during the nanosecond pulse, in contrast to the 1 % H2 case. Additionally, this study investigate the effect of species at the last nanosecond pulse on ignition delay time of BFG. The results indicate that the impact of nanosecond plasma on the ignition delay time of BFG can be captured by considering the concentration of the primitive BFG/air species (CO, CO2, H2, O2, N2) and key radicals (O, H, OH) at the last nanosecond pulse.