Chemical looping water splitting

Technology

What is it?

A chemical loop utilises a recyclable metal with water and hydrocarbon feedstocks to produce hydrogen, water and carbon dioxide. The metal is involved in a repeating cycle of reaction steps.

Why is it important?

Hydrogen and carbon dioxide are obtained as separate high-purity gas streams, allowing easier integration of CCUS.

Characteristics

• Inputs: Hydrocarbons / coal / tar. Optional: biomass
• By-products: CO₂, other hydrocarbons
• Operating temperature: 700 to 1000°C

Benefits

• Multiple feedstock options: fuel gas (including alcohol, hydrocarbons [when combined with reforming], biogas, waste gas), heavy bio-crude, biomass, tar and coal
• Solid oxygen carrier eliminates need for air as oxygen supply – fuel is converted into a pure stream of CO₂ and H₂O, which is easily separated
• High purity hydrogen (99.95-99.999%) can be obtained as a separate gas stream
• High fuel conversion efficiency
• Heat from exothermic oxidation can be channelled to the exothermic reduction to reduce required heat input
• If using fluidised bed reactor: continuous operation, supply of pure separated CO₂, N₂ and H₂ - potentially a poly-generation application
• Can be incorporated with syngas conversion processes
• Carbon capture integration has been shown to be effective

Limitations

• Oxygen carriers require replacement over time – utilisation of low-cost natural minerals is important to reduce the cost

RD&D priorities

• Optimise the composition or structure of the oxygen carrier to improve stability
• Evaluate fuel flexibility and investigate natural minerals as oxygen carriers to improve overall dynamic process characteristics
• Improve reactor design
• Improve process development and integration
• Improve process simulation
• Demonstrate prototypes and pilot plants (large scale, long term operation)
• Demonstrate use of oxygen carriers in industrial environment

Known active organisations

• The Australian National University
• CSIRO
• Monash University
• The University of Adelaide
• The University of Newcastle
• The University of Queensland