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PostPosted: Mar 10, 2016 5:22 pm 
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My search of this forum for "Green Freedom" revealed several mentions but no actual technical discussions.

Green Freedom is all about using a LWR's modified (some K2CO3 added) cooling tower's water as an adsorbent for the CO2 in the air going through which would, in turn, be electrolyzed out of that water and combined with hydrogen to make 18000 bbls of synthetic gasoline/oil and 5000 tonnes of methanol (MeOH) per day.(see http://bioage.typepad.com/greencarcongr ... reedom.pdf)

Except for the "nuclear" part , it's really politically correct because it would use waste heat to collect the carbon dioxide & then help convert it to a "carbon neutral" fuel .

Unfortunately, it's impossible because the air used to cool a typical reactor would contain only about 2% of the carbon dioxide necessary to make that much fuel. (see the gold highlighted part of the ATTACHMENT)

I also feel that the LANL's assumptions re its scheme's overall reactor energy-to-fuel energy estimates are pretty optimistic (about 70%) but can't figure out a way to prove it one way or the other. Can any of you?

However, if that part of their scheme is OK we could still use utilize it as a way to convert CO2 form cement/lime plants to such fuel (much richer CO2 sources).


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PostPosted: Mar 12, 2016 10:50 am 
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Your spreadsheet seems to suggest that there is a 70 degree delta T across a typical natural draft cooling tower?

It is something like 7K, not 70.


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PostPosted: Mar 12, 2016 1:57 pm 
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E Ireland wrote:
Your spreadsheet seems to suggest that there is a 70 degree delta T across a typical natural draft cooling tower?

It is something like 7K, not 70.



Do you have a reference for your delta T figure? I had to guess at it because my Googling didn't come up with anything revealing what a "typical" value would be. I do vividly remember how "steamy" the ATR's cooling tower's air outlflow was even during the hot dry summers that we have out here which is I guessed that that air must be pretty hot.

If the real dT is 7 'stead of 70, the air required to cool the reactor would still only contain about 20% of the CO2 needed to make the amount of fuel claimed.

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PostPosted: Mar 12, 2016 3:18 pm 
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The condensor pressure in an ESBWR is projected to be only 5.4kPa (last page).

That translates to a boiling point of ~35C.
As the vast majority of the energy removed in the condensor is the heat of vapourisation of the steam rather than any remaining sensible heat (as the steam is effectively saturated at the LP turbine outlet) that puts an obvious upper bound on the temperature of the cooling water on entry to the tower, and hence on the air outlet temperature from the tower.
The rated maximum wet bulb temperature of the tower is approximately 27 degrees Celsius, which implies only 7-8 degrees of delta-T across the tower in those conditions.

This is also distorted in that air can actually be cooled below ambient temperature in the tower thanks to the evaporation of the water depending on inlet air humidity.
In other words you can actually have negative air heating.
The air will still be bouyant because it contains water vapour that is lighter than air at equal temperature.

The air flow is primarily there to hold humidity around the droplets down to minimise the wet bulb temperature seen by the water droplets.
The vapour pressure of the droplets is already increased thanks to the Kelvin Effect.

The output can still feel steamy because it is far more humid than the ambient air which means you feel warmer as it supresses the action of perspiration to cool your body.


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PostPosted: Mar 12, 2016 10:40 pm 
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Here's an updated spreadsheet (lines 35-41) assuming a scaled-up version of a referenced example put together by people who are familiar with the details of how cooling towers work.

The bottom line is that the air needed to cool a 1 GWe LWR contains under 4% of the CO2 necessary to make fuel at the rate claimed by LANL's experts; i.e., my conclusion holds.

If we were to pump 25 x as much air through a much-modified cooling tower optimized for CO2 collection rather than cooling, its pumping losses would be prohibitive.

Conclusion: if you want to make a carbon based fuel with nuclear power, don't try to get its carbon moiety from air (or seawater, for that matter).


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PostPosted: Mar 27, 2016 11:00 am 
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I had many email correspondences with those two scientists a few years ago and spoke to them on the telephone. My conclusion was they are underestimating costs. I do not have the technical background to judge if their technology will actually work as promised. It may very well work, but it will be expensive.


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