Ammonia cracking + H2 purification

Green ammonia is a widely proposed hydrogen carrier for shipping — easier to liquefy and transport than liquid H2 itself, then cracked back to H2 at the point of use. A fixed-conversion reactor dissociates NH3 (2 NH3 -> N2 + 3 H2, endothermic, 99% conversion at a typical 600 C cracking-furnace outlet) and the cracked gas is polished by an adsorption stage to fuel-cell-grade H2. Honesty note: this models the adsorption stage as a single equilibrium Langmuir contact (competitive isotherm, H2 weakly adsorbed vs. N2/NH3 strongly adsorbed) — a real PSA's cyclic pressure-swing/purge steps aren't modeled, only the equilibrium separation a cycle is built around. A true gas-phase membrane stage was left out for the same reason: the solver's membrane unit op is a liquid reverse-osmosis model (osmotic-pressure driven), not a gas-permeation membrane, so it doesn't apply here.