Gas switching technology offers a promising alternative to chemical looping applications for highly efficient power or hydrogen production with integrated CO2 capture.
With respect to the demonstration activities, a 35 wt% active content oxygen carrier, tested under Gas Switching Water Splitting (GSWS) conditions, has shown good performance in terms of steam conversion to hydrogen and redox cyclability. Maximizing the CO2 purity and capture efficiency in GSWS requires an oxygen carrier with a high active content. A 75 wt% active content oxygen carrier has been manufactured and tested but it had shown higher tendency to carbon deposition combined with agglomeration, creating operational challenges.
A lanthanum-based oxygen carrier was tested under the Gas Switching Partial Oxidation conditions (GSPOx) for combined syngas production and CO2 utilization or hydrogen production. Despite the high reactivity and stability of this oxygen carrier, carbon deposition occurs at high methane partial pressure, which is acceptable when syngas production is targeted. This could however be an issue if pure hydrogen production is targeted, imposing adoption of additional measures for hydrogen purification.
In summary, the experimental activities contributed to diversifying the low CO2 footprint pathways of syngas and hydrogen production from methane reforming and optimizing their performance by minimizing the extent of carbon deposition while increasing the value of CO2 into usable products. An important feature that has been demonstrated through this work is the tunability of the produced syngas composition thus facilitating its efficient integration to a variety of downstream GTL applications. A 50 kWth pre-pilot cluster of three reactors able to operate at realistic temperature and pressure (1100 °C and 20 bar) was developed and commissioned which can be used for further maturation and scale of the different GST processes. This cluster was also used for testing the Mn-based OC under the combustion mode.
Regarding the techno-economic assessments, the project has evaluated several efficient process configurations involving gas switching technology through coupled reactor and process modelling. Firstly, it was established that GSC can eliminate the energy penalty of CO2 capture when integrated into an integrated gasification combined cycle (IGCC) power plant, with the best performing configuration achieving 50% efficiency through added firing with natural gas. Subsequent work showed that a simpler configuration using GSOP reactors can improve the efficiency of conventional pre-combustion CO2 capture in IGCC plants by about 5 %-points.
Economic assessments showed that these configurations can capture CO2 for as little as 23.3 Euros/ton. However, these plants will operate best as baseload power generators, which is not compatible with the rise of variable renewable energy. For this reason, more focus was given to developing inherently flexible plant configurations that integrate well with variable wind and solar power.
The first such configuration evaluated was a pre-combustion natural gas-fired power plant with full flexibility to produce either electricity or pure hydrogen. A subsequent economic assessment showed that this GSR-CC plant performs similarly to benchmarks under baseload conditions, but clearly outperforms benchmarks in a more realistic scenario where the plant operates under mid-load conditions to balance variable renewables.
Two flexible configurations were also devised for plants fuelled by syngas from solid fuels. The first alternative integrates GSC reactors with a humid air turbine (HAT) power cycle and uses the oxygen carrier material as an energy storage medium, allowing the gasifier to operate at steady state, while the power cycle operates flexibly. It returns about 2 %-points lower efficiency and 5 %-points better CO2 avoidance than the conventional GSC-IGCC plant. Subsequently, another configuration was investigated where a membrane-assisted water-gas shift reactor is integrated in the GSC-IGCC plant to allow for flexible power or hydrogen production from solid fuel. The best configuration achieved 50.3% electric and 62.4% hydrogen efficiency with more than 95% CO2 capture.
Finally, an economic assessment of the GSR technology for pure H2 production has revealed the possibility to produce hydrogen at costs below that of conventional steam methane reforming technology. An attractive business case for scale-up was identified where the GSR-H2 plant is first constructed with no CO2 capture, resulting in substantially lower costs than benchmarks. When CO2 prices finally rise and CO2 transport and storage infrastructure is in place, this plant can be easily and cheaply modified for 98% CO2 capture from the concentrated CO2 stream naturally produced by GSR. This feature makes the GSR-H2 plant robust to almost any future energy policy scenario.
The project contributed to diversifying the low CO2 footprint pathways of syngas and hydrogen production from methane reforming and optimizing their performance by minimizing the extent of carbon deposition while increasing the value of CO2 into usable products. An important feature that has been demosntrated through this work is the tunability of the produced syngas compsition thus facilitating its efficient integration to a variaty of downstream GTL applications. A 50 kWth pre-pilot cluster of three reactors able to operate at realistic temperature and pressure (1100 °C and 20 bar) was developed and commissioned which can be used for further maturation and scale of the different GST processes. The outcome from this work package has been presented in eight international conferences and six international journal articles.
The GSR-H2 concepts show great potential and can trigger industrial interest after appropriate dissemination of the results obtained.
Gas switching technology offers a promising alternative to chemical looping applications for highly efficient power or hydrogen production with integrated CO2 capture. Oxygen production for oxyfuel CO2 capture is also possible. In order to maximize efficiency, these processes need to operate at elevated pressures, creating serious scale-up challenges for interconnected chemical looping reactors. Gas switching reactors, on the other hand, are simple standalone units that can be scaled up and pressurized without facing unforeseen challenges.
The GaSTech project will accelerate the development of gas switching technologies by developing a business case for further technology scale-up. The business case will have two main components: 1) lab-scale demonstration (TRL 4) of gas switching reactor concepts and 2) large-scale technology implementation studies to evaluate techno-economic feasibility of process concepts incorporating gas switching reactors.
Specialized partners will be responsible for each individual project component. Experimental demonstration will utilize an existing reactor at NTNU that has been successfully used for demonstration of pressurized gas switching combustion. ETH will select and pre-test the oxygen carrier materials to be manufactured by ESAM for demonstration purposes. SINTEF will utilize existing large-scale gas switching reactor models to provide input to process simulations done by TUHH and UPM. Using this data, UBB will carry out economic assessments for the different processes and HAYAT will assess the business case.
GaSTech will investigate four gas switching technologies: combustion, reforming, water splitting and oxygen production. The clear similarities between these processes will allow for efficient parallel assessment in a single project. In this way, GaSTech will maximize the likelihood of developing the compelling business case required for an immediate follow-up project at TRL 6.