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Supercritical CO2 Closed-Cycle Gas Turbines
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Author:  NNadir [ Apr 15, 2010 6:30 pm ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

At the right time, under the right conditions, particularly in the presence of any carbon in any form, carbon dioxide is actually a fairly decent oxidant.

It's certainly by no means a show stopper, but something worth keeping in the back of one's mind. The topic of carbon dioxide as an oxidant is on my mind quite a bit.

Supercritical carbon dioxide, usually with complexants or other additives, is now the subject of international attention as a so called "green" solvent, including solvent extraction in actinide/fp chemistry, but not limited to that kind of chemistry.

Author:  Cyril R [ Dec 19, 2011 5:15 am ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

Is there any reaction between the secondary fluoride coolant, such as NaF-NaBF3 or KF-ZrF4 or NaF-BeF2, with CO2? Specifically, if there is a leak of CO2 into the secondary molten salt coolant, what happens?

Author:  Luke [ Dec 19, 2011 6:51 am ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

Cyril R wrote:
......if there is a leak of CO2 into the secondary molten salt coolant, what happens?
So far as I can tell from the thermodynamic data, all you get is fizzy salt, i.e. some CO2 dissolves at the high P / low T end, and will try and come out as bubbles in the primary HX when it gets hot. The initial state with F bonded to Na, Li, K, B or Zr and O bonded to C is markedly more stable than any alternative arrangement of those elements. CO2 is a slightly acidic gas, borates are also acidic, though this is suppressed here by interaction with NaF. NaF is marginally basic, but it's neutralised by the borate. ORNL chose mixtures that are about as close to the bottom of the energy hill as you can get.

Author:  Cyril R [ Dec 19, 2011 6:58 am ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

Thanks for the quick response Luke. It looks like CO2 has an important advantage in leak compatibility compared to water/steam.

Author:  Cyril R [ Jan 12, 2012 5:34 am ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

I found this report that summarizes the performance of a test loop at Sandia.

http://prod.sandia.gov/techlib/access-c ... 100171.pdf

Lots of interesting information. Clearly there are some material issues to be resolved (bearings that last 20 hours when throttled!). 75000 rpm is nasty.

Author:  Asteroza [ Feb 17, 2012 6:29 am ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

I noticed there didn't seem to be much in the way of discussion of non-traditional axial turbines. RamGen is working on an unusual design for a CO2 compressor (and similar full combustion gas turbine) based on compression and expansion ramps wrapped around a rotor. The gas turbine one is effectively a curved ramjet on a wheel rim, sucking in premixed air/fuel and using the shock to ignite the mixture. The compressor ramp inlet, which they call a rampressor, and the expansion ramp nozzle, can be separated into single function rotors. The company seems to be involved with coal plant CCS demos as a compact low power CO2 compressor. It seems compressor exit temperature is high though, so it may be less attractive for a SCO2 loop.

http://www.ramgen.com

To be honest, I don't have a clear idea of how a shock compression based compressor would behave with a near supercritical or supercritical mixture, so it may be totally not applicable.

Author:  camiel [ Mar 03, 2012 4:13 pm ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

I have been reading a lot on the supercritical CO2 cycle lately and I would like to share the following link to the Supercritical CO2 Power Cycle Symposium: http://www.sco2powercyclesymposium.org/

The site has a very useful repository of documents, originating from symposia held in 2009 and 2011. Labs such as Sandia and Knolls Atomic Power Laboratory and companies such as Barber-Nichols are very active in researching the supercritical CO2 cycle. This must be a very interesting development for the U.S. Navy with their future plans for all-electric ships equipped with railguns, which need lots of power.

A supercritical CO2 cycle can use all kinds of heat sources and there are several papers investigating nuclear reactor-SCO2 cycles, ranging from a sodium-cooled reactor (paper by the French CEA) to a lead-cooled reactor (paper by KAERI from South Korea) and a direct cycle Gas-cooled Fast Reactor (paper by Sandia). Nothing on MSRs and SCO2 cycles, however.

Author:  camiel [ May 06, 2012 8:43 am ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

Sandia National Laboratories is apparently looking at marketing the supercritical carbon dioxide turbine it is developing, in light of DOE SMR funding:

http://www.bizjournals.com/albuquerque/ ... oosts.html

Author:  camiel [ Jun 03, 2012 4:17 pm ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

I was just wondering why none of the major players in the turbine/generator business (Alstom, General Electric, Siemens, Doosan, Mitsubishi, etc.) are investing in the development of closed-cycle gas turbine systems, such as S-CO2 gas turbines, which hold great promise, not only for nuclear applications but also for other kinds of heat sources. Don't they see a need for this technology ?

Author:  Cyril R [ Jun 04, 2012 1:58 pm ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

camiel wrote:
I was just wondering why none of the major players in the turbine/generator business (Alstom, General Electric, Siemens, Doosan, Mitsubishi, etc.) are investing in the development of closed-cycle gas turbine systems, such as S-CO2 gas turbines, which hold great promise, not only for nuclear applications but also for other kinds of heat sources. Don't they see a need for this technology ?


Well, it isn't really that surprising. It's a long term development and a risky one. Big companies have shareholders to keep happy, and they don't like investing money with no return for 10-20 years. Also these companies already have open cycle Brayton for direct fuel combustion and closed cycle steam for external combustion. It could be that they don't see the market for closed Brayton cycles. Another factor is that many of these big engineering companies are equipment suppliers, not buyers. They have to be sure of some kind of market. That's why you see GE lacking guts on the ESBWR and the S-PRISM. They could easily buy a unit or two themselves but they are don't consider themselves as buyers. It's really a shame. If they made an exeption and be a product buyer for once, they could prove to the world that their advanced reactors are practical, proven, and desireable. Right now they're just making a bad impression with their "failure to launch".

If you look at the real risky first stage innovation, this is done with public R&D. For example gas turbines were initially developed with huge funds for the military. Very practical for fighter jets. It was only when these turbines were well established in the jet fighter market, that the big commercial giants got interested. In fact, their initial products were little more than jet engines with a generator attached...

Author:  camiel [ Jun 05, 2012 8:21 am ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

I think the development of this technology may be a low-to-medium risk for companies like General Electric or Siemens. Failure of such a project is not going to bankrupt the company. According to Steve Wright of Sandia the development of 10MW prototype is going to cost about $20 to $30 million dollars, with a time frame of 3 to 4 years. He is quoting a cost of $1 per watt once development is underway. A 100MW turbine would cost about $ 100 mn. dollars. I think it is small beer for companies like Alstom, GE and Siemens. It may be that they are happy with the status quo, but I think developing such a technology would open up new opportunities, ranging from coal-fired, solar thermal to nuclear, and would be a way to differentiate themselves from the competition.

You are right about the S-PRISM. I think it would be a good idea if General Electric would offer the UK Government to build it for them under a so-called BOT-contract (Build, Operate, Transfer) as a solution for Britain's 100 t plutonium "problem". GE has definitely the financial capacity to do so. Perhaps, them not doing so tells me they are not convinced of the PRISM technology themselves.

Author:  camiel [ Jun 08, 2014 5:11 am ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

For those interested in supercritical CO2 power conversion systems R&D:

http://www.swri.org/4org/d18/sCO2/abstracts.htm

There is going to be a new symposium on supercritical CO2 power cycles, this time it will be held in Pittsburgh, PA on September 9 and 10, 2014. Information from previous symposiums can be found here: http://www.sco2powercyclesymposium.org/resource_center

Author:  Kirk Sorensen [ Jun 08, 2014 11:54 am ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

Thanks! This looks very interesting!

Author:  jagdish [ Jun 14, 2014 4:28 am ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

I am thinking of the use of CO2 as coolant in CANDU PHWR. It is one reactor design where you can use a different moderator and a coolant. CO2 will save on heavy water used.
The British are using their AGR's but are going for costlier EPR. What is their point in giving up CO2? Is it corrosion at high temperatures?
If we use Th-Pu or Th-20%LEU for a high burn up fuel, we could bundle all the medium life features together with CO2 coolant and have single use replaceable, recyclable fuel tubes in the PHWR. Lower fuel and heavy water costs could balance the lower tube life costs.

Author:  Lindsay [ Jun 15, 2014 12:26 pm ]
Post subject:  Re: Supercritical CO2 Closed-Cycle Gas Turbines

camiel wrote:
For those interested in supercritical CO2 power conversion systems R&D:

That does look interesting, I'd be keen to better understand how far away the first commercially available systems are likely to be and what sort price estimates go with those.

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