On Jul 20, 2009, at 5:56 AM, Jones Beene wrote:
-----Original Message-----
HH: Possibly a better way to go is to use oxygen to burn the
power plant fuel and recycle 100% of the CO2 through algae. Then run
the power plant on the algae, its oil, cellulose and all. No coal
necessary at all. No sequestration necessary. The byproduct, a lot
of liquid nitrogen ....
Horace, it gets even better than that. You do not need cryogenics or
nitrogen storage and distribution. These options have been tossed
around in
the past. There are a number of techniques for enriching air in O2
from
about 80/20 to about 50/50 with minimal energy expenditure.
Yes. For example, google (oxygen membrane). Also, google (oxygen
conductor).
Unless the value of the nitrogen can be made higher, then full
separation of
the gases through cryogenics, or pressure swing techniques, etc is
far too
energy intensive to make that feasible.
I don't know that to be true when you get into GW power generation.
Most of the energy of compression can be recovered, provided the heat
of compression is stored, or otherwise available. Much more refined
heat exchange methods are affordable for very large scale
liquifaction/vaporization plants than for ordinary air liquifaction
plants. There is a somewhat analogous phenomenon relating to water
distilling. If your sole goal is the distilling of water, then the
energy obtained from generating electricity from the steam generation
can be recovered by driving restive heating in the boilers. This
provides a feedback effect that permits distilling water with far
less energy than that required to boil it.
With the most efficient low pressure blower - the so-called
squirrel-cage
type, you can move tons of air per hour very cheaply, and in the
process use
permanent magnets (in combination with selective membranes) to play
on the
very high magnetic susceptibility of O2 compared to N2.
It is more based on the the fact O2 is paramagnetic I think. O2 in
gas (air) form thus can form miniture magnetic dipoles and thus can
be attracted by a magnetic gradient (as opposed to a magnetic
field.) Though it takes little energy to concentrate in this way,
the process is slow because the diffusion rate of the O2 is low, and
diffusion itself tend to cause dilution of the separated O2. The
separation is limited by the diffusion equilibrium that results.
Magnetic separation works better with liquid air.
There are quite a few patents and also studies like this:
http://www.sciencedirect.com/science?
_ob=ArticleURL&_udi=B6TVM-4M221KK-C&_us
er=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStr
Id=962
541556&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_
userid
=10&md5=3b66ddc35ecf90947310ba1c670e3ca2
This abstract implies the idea is new. Hardly true! This kind of
separation has been around a long time. I thought about trying to
improve my home boiler by adding a magnetic separator to it decades
ago. I thought the better of it after considering the possible side
effects. It seems to me there was a SciAm Amateur Scientist (or
maybe PopSci) article about this in the 60's.
Actually some nitrogen is preferable in the exhaust - especially
for Algae
growth in those strains used for food purposes, so the 50/50 mix is
good.
The net exhaust gas has been reduced in volume considerably, the net
proportion of CO2 increased and it makes for a tidier system.
Regardless as to whether the CO2 comes from 100 percent recycling, or
some of the new carbon comes from the air via photosynthesis, the
important thing I think is to avoid burning fossil fuels to make
electricity. Recovering 40 percent of the CO2 and then recycling it
via photosynthesis and burning it in motor vehicles still eventually
converts *all* the coal burned to CO2. It is only by closing the
recovery loop, or burning renewables, or some combination, that
production of CO2 from fossil fuels is avoided. If the CO2 is
produced and sequestered, especially in gas form, it is likely just
making a problem for future generations when it escapes, and that
sequestering process (plus the coal mining) may prove to be even more
expensive and location dependent than a fully renewable solution.
Unfortunately most of the research is driven by a coal industry
desperate to continue mining rather than adapting to manufacturing a
renewable solution. They should wake up and realize that the second
approach could employ a lot more people in a lot less dangerous
environment.
My point restated is that what appears to be a 40 percent solution is
not really a 40 percent solution, it is still a zero percent
solution. *All* the CO2 from coal burning ends up in the atmosphere,
though the benefit derived is improved. It is not incrementally that
difficult (or even expensive apparently) to leap from the 40 percent
solution (actually zero percent solution) to a hundred percent
solution. I don't think this is in disagreement with any thing
you've said. I think we are in much agreement. I just feel it is
important to briefly focus attention on the importance of the 100
percent solution because a 40 percent conversion to biofuel solution
looks like a viable compromise from a political point of view, when
it really is no compromise at all on where every ounce of the the
coal mined ends up.
In terms of "societal value" and especially if we avoid all coal
(with its
toxic ash like arsenic) I think we would be better off growing an
algae
strain that is high in food protein and lower in lipids.
If the plant operator must use coal, then a strain with higher
lipids would
be preferable, of course; but if the plant operator knows that he
will be
able to reduce the net tonnage of new carbon purchased, by up to
2/3 even
with food algae, then it makes shifting away from coal more
palatable ...
"palatable" being the operative word.
The value of protein should always be much higher (in the big
picture of 6
billion humans) than the value of cellulosic biomass. Therefore,
even if an
even-swap is made (for humanitarian reasons) that is to say: algae for
biomass - then the results of having the increased high quality food
available to feed both humans and farm animals is highly beneficial.
Of course, planning-ahead with that kind of 'big picture'
foresight, is not
something that capitalism does very well.
Jones
Yes, and we haven't even touched on the world wide water shortage
problem. At least some oilgae can produce oil while living in salt
water. That helps, but the demand for energy to make pure water from
ocean water and from contaminated sources continue to grow. We
clearly need to develop major new and safe global sources of energy.
OTOH, maybe nature will solve the problem by a sudden reduction of
the population.
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
