Bridging Blue and Green Hydrogen (21.RP2.0085) – Completed

The challenge

All hydrogen production methods suffer from significant drawbacks.  In the case of green hydrogen production via electrolysis, total production cost is inhibitive whereas for blue hydrogen production (methane reforming, coal gasification and methane pyrolysis, all followed by CO₂ capture and storage) significant residual CO₂ emissions persist.

The solution

This project considered the combined production of blue and green hydrogen, exploring the potential for both cost and CO₂ emissions reduction, whilst also considering the various logistical and operational challenges posed by integration. The link in this case is use of autothermal reforming (ATR) of methane or coal gasification (CG) for blue hydrogen production with the required oxygen feed being provide via the electrolysis of water for green hydrogen production.

Researchers produced a dynamic ASPEN simulation of an integrated blue and green hydrogen production process and compared this against separate blue and green hydrogen production. Both ATR of methane and coal gasification (CG) of lignite were considered for blue hydrogen production whilst proton exchange membranes (PEM) electrolysis was considered for green hydrogen production. Detailed case studies were executed for locations in the vicinity of Karratha (ATR) and the Latrobe Valley (GC) respectively. Total cost (levelised cost of hydrogen (LCOH) and emission intensity (kg-CO₂e/Kg-H₂) were finally determined and compared.

The outcome

Integration using oxygen from electrolysis to feed the reforming process reduced costs significantly relative to green hydrogen production and reduced CO₂ emissions relative to blue hydrogen production. The effect was much more pronounced in the case of ATR. Sample data below pertains to a 100 tonnes per day hydrogen production facility.

CAPEX = Capital Expenditure; EI = Emissions Intensity; OPEX = Operating Expense; C2G = Cradle to gate; LCOH = Levelised Cost of Hydrogen; W2G = Well-to-Gate

Impact

The impact of this project is that it showed that the integrated process would allow reduced costs and a quicker reduction of CO₂ emissions for current hydrogen facilities looking to transition towards electrolytic green hydrogen production.

Next steps

Future research should focus on reducing the complexity and costs of integration, in particular those associated with the required oxygen buffering.  Other potential uses of the (currently) waste oxygen by-product of green hydrogen production via electrolysis should also be explored.