A system for use in the recovery of 1,3-butadiene from a C 4 fraction in both a high pressure mode or a low pressure mode, comprising: a feed vaporization system for at least partially vaporizing a hydrocarbon feed containing butanes, butenes, 1,2-butadiene, 1,3-butadiene, C 4 acetylenes, C 3 acetylenes, and C 5+ hydrocarbons; an extractive distillation system for contacting the vaporized hydrocarbon fraction with a solvent to selectively dissolve a portion of the hydrocarbon fraction forming (a) an enriched solvent fraction comprising the 1,3-butadiene, the 1,2-butadiene, C 4 acetylenes, C 3 acetylenes, C 5+ hydrocarbons, and a first portion of the butanes and the butenes and (b) a vapor fraction comprising a second portion of the butanes and the butenes; a rectifier and afterwasher for at least partially degassing the enriched solvent fraction and recovering a first vapor fraction comprising the first portion of the butanes and butenes, a second vapor fraction comprising the C 3 and C 4 acetylenes, 1,3-butadiene, 1,2-butadiene, and C 5+ hydrocarbons, and a bottoms fraction comprising partially degassed solvent; a degasser and cooling column for further degassing the solvent and recovering a liquid fraction comprising degassed solvent, a third vapor fraction comprising at least one of C4 acetylenes and 1,2-butadiene, and a fraction comprising C4 acetylenes; wherein the system for recovering 1,3-butadiene is configured to operate alternatively (a) with the degasser in a high pressure mode, or (b) with the degasser in a low pressure mode; a compressor for compressing the third vapor fraction when operating in the low pressure mode; and a heat exchanger for indirectly heating the partially degassed solvent with the liquid fraction comprising degassed solvent when operating in the low pressure mode. a feed vaporization system for at least partially vaporizing a hydrocarbon feed containing butanes, butenes, 1,2-butadiene, 1,3-butadiene, C 4 acetylenes, C 3 acetylenes, and C 5+ hydrocarbons; an extractive distillation system for contacting the vaporized hydrocarbon fraction with a solvent to selectively dissolve a portion of the hydrocarbon fraction forming (a) an enriched solvent fraction comprising the 1,3-butadiene, the 1,2-butadiene, C 4 acetylenes, C 3 acetylenes, C 5+ hydrocarbons, and a first portion of the butanes and the butenes and (b) a vapor fraction comprising a second portion of the butanes and the butenes; a rectifier and afterwasher for at least partially degassing the enriched solvent fraction and recovering a first vapor fraction comprising the first portion of the butanes and butenes, a second vapor fraction comprising the C 3 and C 4 acetylenes, 1,3-butadiene, 1,2-butadiene, and C 5+ hydrocarbons, and a bottoms fraction comprising partially degassed solvent; a degasser and cooling column for further degassing the solvent and recovering a liquid fraction comprising degassed solvent, a third vapor fraction comprising at least one of C4 acetylenes and 1,2-butadiene, and a fraction comprising C4 acetylenes; wherein the system for recovering 1,3-butadiene is configured to operate alternatively (a) with the degasser in a high pressure mode, or (b) with the degasser in a low pressure mode; a compressor for compressing the third vapor fraction when operating in the low pressure mode; and a heat exchanger for indirectly heating the partially degassed solvent with the liquid fraction comprising degassed solvent when operating in the low pressure mode. <EOS>