Low-emission pre-combustion gas-to-wire via ionic-liquid [Bmim][NTf2] absorption with high-pressure stripping

Abstract

Autothermal reforming is an important pathway to hydrogen via fossil fuel decarbonization. Traditionally, the finishing step of hydrogen production via autothermal reforming consists of decarbonation via conventional aqueous-amine absorption which incurs a huge energy penalty due to high heat-ratio and low-pressure carbon dioxide stripping entailing costly compression for geological storage. This work proposes and assesses an alternative high-pressure temperature-swing hydrogen decarbonation that promotes stripping at high-pressure reducing carbon dioxide compression costs. Such new hydrogen decarbonation uses 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide ionic-liquid physical-absorption due to its solute affinity, low vapor-pressure, high thermal stability and low heat consumption for carbon dioxide stripping at high-temperature and high-pressure. Technical and economic aspects of the ionic-liquid temperature-swing decarbonation are evaluated and compared with the conventional aqueous-amine decarbonation. Results showed that high-pressure ionic-liquid stripping requires 5.5 times less heat to produce a high-pressure carbon dioxide stream and reduces 4.3 times its compression power. These results directly impact net power exportation of the combined-cycle hydrogen-fired power plant; i.e., the ionic-liquid gas-to-wire exports 35.6% more electricity than the aqueous-amine counterpart. Economically, the ionic-liquid gas-to-wire has 36% higher revenues, entailing a net value 2.5 times higher (US$ 390.2*106) and 5 years lower payback-time than the conventional aqueous-amine counterpart.