Pilot-scale experimental study on arc-coupled microwave plasma-enhanced pulverized coal ignition

To ensure energy security and promote renewable integration, fuel-efficient ignition strategies for coal are of practical importance. This study establishes a pilot-scale arc-coupled microwave plasma ignition system to improve the ignition performance of low-volatile pulverized coal while reducing energy consumption. The effects of microwave power, arc power, coal fineness, and feed rate on the ignition process were systematically investigated. Flame temperature, spectral emissions, and stability were evaluated using thermocouples, optical fibre spectroscopy, and flame imaging. Results show that microwave energy enhances arc plasma excitation and promotes the formation of reactive species, thereby improving ignition stability and combustion activity. Compared to arc-only discharge, the coupled arc–microwave discharge achieves higher flame temperatures under the same or even lower total power, demonstrating superior energy efficiency. Fine coal particles (R90 = 10%–20%) respond more sensitively to microwave enhancement under low arc power, favouring a ‘low arc–high microwave’ configuration. Conversely, coarse particles (R90 = 30%) require a ‘high arc–high microwave’ setup for reliable ignition. Increasing the feed rate results in a more stable, compact flame and better microwave coupling, whereas insufficient feeding leads to flame dispersion, temperature fluctuations, and wall heat loss. This study elucidates the synergistic interactions between coal, microwave, and arc plasma under multi-parameter conditions, offering theoretical guidance and practical insight for plasma-assisted ignition in complex coal combustion systems.