Acetylene recovery from cracked gas (selective solvent absorption)

The other real use of cracked-gas acetylene: instead of being hydrogenated away as a trace impurity (see naphtha-steam-cracker's ACETYLENE_HYDRO step and patent-c3-selective-hydrogenation), acetylene is deliberately RECOVERED as product when present at high enough concentration -- industrially via selective solvent absorption (DMF or NMP preferentially dissolve acetylene over the other light hydrocarbons), then stripped back out to release a pure acetylene stream. Honesty note: no cited DMF/NMP-hydrocarbon binary VLE data exists in this codebase to build a rigorous absorber/stripper, so this uses the same fixed-recovery separator shortcut this codebase's existing amine/CO2-capture examples already use for exactly this situation (e.g. blue-hydrogen-smr-ccs's CO2 capture step) -- a disclosed simplification of a real physical separation, not a claim of rigorous solvent thermodynamics.