A chemical reactor network approach for a gas-assisted iron dust flame in a laboratory-scale combustor

Abstract

Metal powders demonstrate promising performance when reacting with oxygen in laboratory-scale reactors, releasing the chemically stored energy as heat. To scale up this technology, chemical reactor network (CRN) modeling serves as a critical tool to bridge the gap between laboratory experiments and real-world applications. In this work, a multi-phase CRN is derived to analyze the iron oxidation and pollutant formation in a novel methane-assisted iron dust flame in a laboratory-scale combustor. State-of-the-art single particle oxidation models are employed to describe the conversion of iron particles, while gas phase combustion is modeled with a detailed kinetic mechanism within fully coupled reactors. The approach is validated for single particle combustion using the solid-gas plug flow reactor. It is demonstrated, that a reactor network model with four solid-gas perfectly stirred reactors accurately reproduces the flame structure of laminar iron flames. Subsequently, both ideal reactor models are combined in a multi-phase reactor network to analyze iron oxidation, evaporation and NOx formation in the swirl burner. The CRN design is based on a recent high-fidelity Large Eddy Simulation. The monodisperse description of the iron suspension within the CRN reveals that different initial particle diameters significantly influence the estimated evaporated mass, ranging from less than 0.5% for $20\mu m$ particles to approximately 4% for $5\mu m$ particles, while the overall iron conversion remains largely unaffected. Furthermore, sensitivity analyses highlight the critical role of the oxygen distribution and local gas temperatures within the reactor to effectively control NOx formation and potential nano-oxide emissions during iron combustion.