Perspectives on Oxy-fuel combustion after OxyCAP/OxyCORR workshops

Written by Ignacio (Nacho) Trabadela, a PhD student at the University of Edinburgh whose attendance at the OxyCAP/OxyCORR workshops in London in June 2014 was supported by the ECR Meeting Fund. This focusses on the OxyCORR part of the workshops. A blog about the OxyCAP element can be read here

In sunny London, after three June days of results and discussions about research on oxy-fuel combustion, one thing was clear from my perspective: oxy-fuel is very well positioned to roll-out as key CCS technology for mitigating climate change. Two first of a kind (FOAK) plants towards technology commercialisation are expected in operation before the end of this decade: FutureGen 2.0 in the US and White Rose in the UK. Oxy-fuel has inherent flexibility due to: 1) variability in O2 levels during the combustion process, allowing enhanced fuel flexibility; 2) fast ramp-rates of air separation unit (ASU) upon O2 purity; and 3) option of interim flue gas recycle use/energy storage upstream compression and purification unit (CPU). Flexibility is essential because debate about base load plant efficiency and CCS associated penalties comes into a new stage when electricity is dispatched where existing constrains in supply-demand, meaning that load-following plants revenue increase at peak demand in a grid with high renewables penetration but unable to dispatch. Although levelised cost of electricity (LCOE) might be higher for an oxy-fuel plant versus unabated plant or other comparable technologies, that load capability to dispatching at higher demand quickly means higher margins, becoming a more efficient business model if plant is capable of not missing any of the hours with higher profit in the year. This has an effect in wholesale electricity prices but does not mean higher prices for consumers, in most cases the contrary.

Having attended previous IEAGHG Oxy-fuel Corrosion Workshops in 2011 (London, UK) and 2013 (Ponferrada, Spain) it was interesting to see evolution of this research topic. There are not many urgent research questions outstanding on corrosion and OxyCORR  has proved that. Organised by IEAGHG, OxyCORR had two chairmen: Prof. Axel Kranzmann from BAM (Germany) and Prof. John Oakey from Cranfield University (UK), best contact experts on this research area.

There were presentations from Industry such E.ON (UK) and Alstom (Switzerland/Germany) joined by discussion from US DOE, IFK Stuttgart and UK institutions.

The main conclusions from the workshop and key elements in final discussion were:

1) Focus on next research steps from this working group should be around:

1.1) Implementation with advanced steam conditions – 700 deg C steam

1.2) Impacts of different fuels including biomass and ash compositions

1.3) Plant operation conditions – base load v flexible operation and effect on materials.

2) Conventional air-firing experience translates well to oxy-firing. 1st Generation demonstration plants will have modest steam conditions There is still a desire to reduce plant costs by minimising clean-up of the recycle gas. Efficiency of dry S-capture in FutureGen 2.0 scheme will be good in order to compare to low S (0.2 – 0.35 % sulphur in coal) in Callide where they do not have an internal FGD.

3) Talking large scale is only possible if wooden biomass versus other biomass options for smaller boilers.

4) Temperature transients – corrosion – important to pay attention to things condensating from gas/ evaporating.

5) Plant operational conditions – base load vs. load following – impact of load variations/recycle levels on boiler environment. Traversing dew-points in flexible plant operation means longer residence time of particles in the boiler – deposition of the particles.

6) There is not enough information on how oxy-fuel plants will work 50-60% load and how that will affect corrosion.

7) Need for long term testing. Typical is 1000 hours so might be worthy going to 10000 hours or over a year test.

8) There is need for more work on CFB option for in-bed capture.

9) Corrosion data should be handled following adequate ISO standard.

10) There are no significant changes in ash and material behaviour under oxy-fuel that cannot be tackled properly. However, there is a need for a strategy to go ahead into oxy-fuel commercialisation stage.

Presentations (available at https://www.ieaghg.org/ccs-resources/technical-workshops/19-ccs-resources/technical-workshops/462-4th-meeting-of-the-oxy-corrosion-working-group ) given were an excellent exercise towards high impact and delivery of current research into the FOAK oxy-fuel projects.

Finally, I’d like to thank my supervisors Jon Gibbins and Hannah Chalmers for giving me the opportunity of attending key meetings during my PhD studies. Also, I’d like to acknowledge the financial support of the UK CCS Research Centre in financing attendance to OxyCORR in London as part of UKCCSRC Network Early Career Researcher Meeting Fund. The UKCCSRC is funded by the EPSRC as part of the RCUK Energy Programme.