SCO2 Oxy-Combustion Technology Group
SCO2 Oxy-Combustion Technology Group
December 11, 2017
Presentation by Dr. Pete Strakey
- 1:05p – Introduction / Meeting Outline / Objectives
- 1:15p – Strakey presentation on NETL R&D activities
- 2:00p – Q&A
- 2:15p – General Discussion
- 2:30p – Conclude
An introduction from the Working Group host:
- Seth Lawson - NETL
- Federal Project Manager in Advanced Energy Systems Team
- Currently several projects in the NETL portfolio related to SCO2 oxy-combustion
- SCO2-based power cycles are a transformational technology
- Direct fired cycles – a major challenge is oxy-combustion
- Working Group plans to meet on a bi-monthly basis
- Meeting is open to the public
- WebEx meeting
- A volunteer speaker will present on a relevant topic followed by Q&A
- Open discussion on SCO2 oxy-combustion will be encouraged
- Meeting minutes and presentation will be shared following the meeting
- Pete Strakey –Thermal Science Group in the NETL Research and Innovation Center (RIC)
- Title: “Oxy-Combustion Fundamentals for Direct Fired Cycles”
- Presented on NETL R&D activities in SCO2 oxy-combustion
- Designed a generic 50 MWth (P=300 bar) combustor with SSME preburner type combustor with 21 coaxial injectors
- Simulated Two limiting cases using CFD:
- The 70% CO2 case yielded conventional looking turbulent flame
- The 91% CO2 case appear to have autoignition characteristics
- Both cases yielded the same average temperature at the combustor exit
- CO2 production in each case was predicted using Dynamic Smagorinksy 17-species skeletal mechanism
- The 70% CO2 case yielded 2.6% CO at combustor exit while the 91% CO2 case yielded >0.1% CO at combustor exit
- Thermo-acoustic instabilities were modeled with LES using the Aramco 17 skeletal model with 75% CO2 by mass
- Radial mode thermoacoustic instability at 3kHz was observed
- Peak-to-peak pressure oscillation was 60% of the mean combustor pressure
- General Conclusions include:
- Oxy-combustion at 300 bar with CO2 diluent is somewhat uncharted territory
- Accurately predicting CO levels for combustor design to minimize CO at the turbine inlet is critical to maximizing cycle efficiency. For every mole % of CO that enters the turbine a cycle efficiency penalty of 1% is expected
- These findings suggest that thermos-acoustic instability is a major issue. Strakey plans to explore the effect of CO2 concentration on instability. Hypothesis: The propensity for instability will decrease as oxygen concentration decreases
- Because selecting appropriate combustion models is critical to accurately modeling combustion with CFD, there is a need for validated detailed chemical kinetic mechanisms and corresponding reduced mechanisms
- Perhaps the greatest research need currently is experimental data from oxy-combustion of natural gas and/or syngas at relevant conditions. This data will play a critical role in validating reduced order kinetic mechanisms and CFD models
Q&A followed the presentation, with some highlights below of Pete’s responses to the questions:
- Used the mean exit temperature from the combustor model (~1550K) as the turbine inlet condition.
- Used Aramco-derived 17-species skeletal mechanism in CFD combustor simulations
- Expect lower CO levels for the lower O2 cases.
- Transport properties from kinetic theory modeling
- Haven’t yet looked at thermoacoustic instabilities at other CO2 concentrations, but instability is expected to improve at high
- Expect propensity for thermoacoustic instability to go down with lower O2 concentration.
- Have not yet looked at combustor equivalence ratio
- In simulations, don’t see any unburned hydrocarbons – all converted to CO2 and CO.
- Flame instability quite a bit worse for low O2 case.
- Important to understand CO levels at the combustor exit and entering the turbine.
- Nate Weiland described some of NETL cycle modeling work:
- Evaluated cycle efficiency as a function of CO mole fraction out of combustor
- Approximately 1% reduction of cycle efficiency per mole % CO in combustor exhaust
- If geometry doesn’t have good mixing, could have higher CO in combustor exhaust
- Effect of excess O2
- Most simulations done at ~1% excess O2
- Didn’t do corresponding cycle analysis but expect slight (1.5%) excess O2
- Will report this work at upcoming SCO2 Power Cycles Symposium
- Need for a combustor test stand to experimentally validate the models
- Modeling/systems analyses work at NETL is valuable to industry
- SwRI has a current DOE-funded project to build/test an oxy-combustor test stand
- They plan to adapt SunShot test loop for oxy-combustor testing
- Seth indicated he spoke with Jacob Delimont at SwRI about presenting on this work at a future Working Group meeting.
- Sought any comments on this Working Group meeting format. Feedback is highlighted below:
- Excellent format to discuss the issues.
- More likely to get people to contribute using this format.
- Could we do the whole meeting on WebEx, not using phone line?
- Is the bi-monthly meeting frequency appropriate?
- Group agreed this is a good frequency for the meeting.
- Any volunteers to present at next meeting?
- Potential opportunities for face-to-face meetings for the Working Group
- 6th International SCO2 Power Cycles Symposium
- Turbo Expo - Norway
Planning Discussion for Future Meetings
Discussion on planning future meetings:
- Next meeting will be in February 2018.
- Can we share the attendee list – names and organizations?
- Do we have a mission statement/mandate?
- Seth indicated the objective is to provide a forum for participants from industry, government, and academia to share insights and address oxy-combustion technology gaps for commercialization of direct fired SCO2 power cycles
- Anyone who has suggestions on how to improve the working group meeting or on the focus/objective of the working group, please email Seth Lawson (email@example.com).