Shrinking-Core Ilmenite Reduction — Lunar Oxygen ISRU

Real gas-solid reactions like hydrogen-reduction of lunar ilmenite (FeTiO₃ + H₂ ⇌ Fe + TiO₂ + H₂O) don't convert a grain all at once — a shrinking core of unreacted mineral retreats inward behind a growing shell of solid product, and hydrogen has to cross gas film, then that product shell, then react at the shrinking surface, three resistances in series. This 2D simulation tracks a whole population of ilmenite grains spanning a realistic size spread, each integrating its own combined-resistance shrinking-core kinetics toward the same temperature- and pressure-dependent equilibrium conversion the process is thermodynamically limited to, and renders every grain's live core/shell radius directly. Adjust reduction temperature, H₂ partial pressure, feed ilmenite content and grain size to see which resistance dominates and how the mass-weighted bulk conversion and oxygen yield respond.