Zero-emission blue hydrogen using chemical scrubbing-based CO2 capture

Achieving global net zero emission necessitates the increasing demand of clean hydrogen for green energy and chemical synthesis. Blue hydrogen from coal gasification with CO2 capture and storage (CCS) enables a practical, cost-effective and scalable approach to decarbonize hydrogen industry with affordable cost. Scrubbing-based CO2 capture is a leading technology to deeply remove CO2 from various gas streams including coal gasification syngas. The present study explored the techno-economic assessment of an aqueous ammonia (NH3)-based CO2 capture process integrated with a coal gasification plant for producing zero-CO2-emission blue hydrogen. Owing to the chemical stability of NH3 at high pressure and temperature, the overall energy consumption of the NH3 process was prominently low at 0.134 MWh/tonne CO2 resulting from ultra-low regeneration duty of 1.2 GJ/tonne CO2 and negligible CO2 compression energy. This led to a competitive levelized cost of hydrogen (LCOH) of $5.3/kg H2 (based on 2022 US dollar). In addition, the proposed NH3 process ($48.2/tonne CO2) exhibited advantageous techno-economic performance compared with the commercial Selexol™ ($159.8/tonne CO2), Rectisol® ($93.9/tonne CO2) and MDEA technologies ($51.5/tonne CO2), indicating its cost competitiveness to achieve a zero-emission blue hydrogen. To our knowledge, this is the first time that zero-CO2-emission blue hydrogen synergised with advanced NH3 scrubbing technology has been presented and analysed in details.