The Combustion Complex of Fine Iron Particles

The true reason underlying the energy crisis faced by our society is not the lack of renewables sources, but the mismatch between a continuous energy demand and a geographically scattered and temporally intermittent supply from these sources. To overcome this problem, the scientific community is in search of reliable and efficient energy storage alternatives. Metal-enabled Cycle of Renewable Energy (MeCRE<b><i>) </i></b>has been proposed as a solution for sustainable, long-distance transport and long-term storage of clean energy. Owing to its high energy density, zero-carbon nature, and recyclability, iron powder is nowadays considered as the most promising energy carrier to realize MeCRE on a global scale. To build real-world power and heat generation systems, fundamental insights into the combustion properties of fine iron particles are required. Although a decent amount of knowledge in the combustion of conventional solid fuels is useful, numerous unique questions rooted in iron-powder combustion must be answered. These questions are mainly related to two unique features of iron-powder combustion: (I) The heterogeneous oxidation mechanism of individual iron particles and (II) the resulting laminar and turbulent flame dynamics with a spatially discrete heat release.<br/><br/>This presentation provides an overview of some theoretical efforts (supproted by experiemtnal evidence) made towards understanding the fundamenals of underlying in iron-powder combustion. The ignition characteristics of iron particles are analyzed consideirng solid-phase oxidation kinetics. After ignition, the rate-limiting mechansims govenring of an iron droplet at more elevated temperature (&gt; 2000 K) is then examined using a single-particle combustion model informed by molecular dynamics (MD) simulations. This study reveals that the oxidation rate of an iron droplet is not solely controlled by the external diffusion of O₂, but an interplay among external diffusion, surface absorption, and internal transport. Euler-Lagrange CFD simulations are used to answer the question as to how the spatially non-uniform energy release from iron particles influences the flame dynamics under application-relevant conditions.