Science and Technology news... :: View topic

Dan Bloomquist · Guest

Cyril Meynier wrote:
[quote]
Efficiency seems to be linked to primary fuel used on one hand (as in
other technologiues, it is harder to use efficiently biomass or
lignite than high-grade coal, because of higher mineral content), and
the size of the chemical reactor on the other hand : a smaller reactor
have more radient thermal losses.

A small biomass-to-hydrogen plant is been built in Germany, with a
thermal power of 2.5 MWth, using low-quality biomass. Efficency is
only in the 50-60% range:
http://www.hyweb.de/News/arcv298e.html#Biomass%20gasification%20project%20april%2098-e

Steam pressure seems to be a important parameter too, since some
laboraties are working on gasification of biomass with supercritical
water.

It is not said wether CO + H2O -> CO2 + H2 is used or CO is burnt
directly.

Departement Of Energy *pomises* a75% for coal-to-hydrogen conversion
in Vision21 plants (for advanced large-scale gasificators), so i am
likely to expect a real figure in the 65-70% range.

Efficiency in undoubtly somewhat higher using methane as fuel, at some
70+% right now (not in 2020).

In all cases, this is much more than with electrolysys (whatever is
the efficiency of the electrolyser) : a state-of-the-art supercritical
coal-fired plant can give a 45% efficiency at best.

Capital cost is likely inferior too. A multi-MW electrolyser would be
very expensive.

From an ecological point of view, producing hydrogen from solar heat
would be much better. A canadian company is building a prototype :
http://www.sheclabs.com/

However, their site offer few accurate figures, no effiency figure is
given.

[/quote]
Here, I posted this a couple of months ago:
http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/32405d.pdf

Thermal production of hydrogen looks like a nice round 50%.

Solar thermal electric and EVs still look good.

Best, Dan.

[quote]
--
"Die Naturwissenschaft ohne Religion ist lahm, die Religion ohne Naturwissenschaft ist blind. "
Einstein
[/quote]

--
http://lakeweb.net
http://ReserveAnalyst.com
dbAtLakewebDotCom

Cyril Meynier · Guest

Retrouvons en direct Dan Bloomquist <lakeweb@citlink.net>, notre
envoyé(e) spécial(e) sur sci.energy.hydrogen:

[quote]
Here, I posted this a couple of months ago:
http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/32405d.pdf

Thermal production of hydrogen looks like a nice round 50%.

Solar thermal electric and EVs still look good.
[/quote]
In this paper, heat is provided at 800°. So Sheclabs must use another
catalyst, since they use lower Temp (400°).

In both cases, the residual heat (the, eg, 50% that are not found in
chemical energy in hydrogen) is rejected at 120°, so it could maybe be
partly used in cogeneration, for absortion air conditioning, district
heating, greenhouses heating, industry, and so on.

best

--
"Die Naturwissenschaft ohne Religion ist lahm, die Religion ohne Naturwissenschaft ist blind. "
Einstein

Don W. · Guest

"Dan Bloomquist" <lakeweb@citlink.net> wrote in message
news:3F9FF4BC.3090500@citlink.net...
[quote]

Harry Conover wrote:
Dan Bloomquist <lakeweb@citlink.net> wrote in message
news:<3F9F0860.3040407@citlink.net>...

I>m waiting to hear what the C + 2H20 -> CO2 + 2H2 efficiency is. If
70%+, that changes things.

Hmmm... I though that this reaction was: C + H2O -> CO + H2, the old
gashouse "Water Gas" process used to produce manufactured illuminating
gas.

How do you modify/re-configure this classic reaction to produce CO2 +
H2 without a loss of energy?

The more perplexing question is that of how to compute efficiency. My
best guess is that one would take the energy yield produced the the
combustion of the CO and the H2, then divide it by the energy
equivalent of the heat of combusion of carbon, in which case I would
predict a thermodynamic efficiency of less than 25% with respect to
the product yield. (Worse still, if the CO is oxidized to CO2 in a
subsequent conversion step.)

Then too, perhaps I>m missing something important which, not being a
chemical engineer, is entirely possible.

Harry C.

Thanks Harry,
I>m not the chemist. I would hope Graham chimes in, he does this best.

Dan.

--
http://lakeweb.net
http://ReserveAnalyst.com
dbAtLakewebDotCom

[/quote]
I>m no chemist too, but I think you simplified a two step process down to
one step. The first step is as Harry described it and the second step takes
the CO and more steam to produce CO2 and more hydrogen.

Don W.

Don Lancaster · Guest

"Don W." wrote:
[quote]
"Dan Bloomquist" <lakeweb@citlink.net> wrote in message
news:3F9FF4BC.3090500@citlink.net...

Harry Conover wrote:
Dan Bloomquist <lakeweb@citlink.net> wrote in message
news:<3F9F0860.3040407@citlink.net>...

I>m waiting to hear what the C + 2H20 -> CO2 + 2H2 efficiency is. If
70%+, that changes things.

Hmmm... I though that this reaction was: C + H2O -> CO + H2, the old
gashouse "Water Gas" process used to produce manufactured illuminating
gas.

How do you modify/re-configure this classic reaction to produce CO2 +
H2 without a loss of energy?

The more perplexing question is that of how to compute efficiency. My
best guess is that one would take the energy yield produced the the
combustion of the CO and the H2, then divide it by the energy
equivalent of the heat of combusion of carbon, in which case I would
predict a thermodynamic efficiency of less than 25% with respect to
the product yield. (Worse still, if the CO is oxidized to CO2 in a
subsequent conversion step.)

Then too, perhaps I>m missing something important which, not being a
chemical engineer, is entirely possible.

Harry C.

Thanks Harry,
I>m not the chemist. I would hope Graham chimes in, he does this best.

Dan.

--
http://lakeweb.net
http://ReserveAnalyst.com
dbAtLakewebDotCom

I>m no chemist too, but I think you simplified a two step process down to
one step. The first step is as Harry described it and the second step takes
the CO and more steam to produce CO2 and more hydrogen.

Don W.
[/quote]
Efficiency is meaningless if you do not also consider loss of exergy.

Being 100 percent efficient at converting high value kilowatt hours into
low value kilowatt hours is pretty much useless.

--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: don@tinaja.com fax 847-574-1462

Please visit my GURU>s LAIR web site at http://www.tinaja.com

Dan Bloomquist · Guest

Don Lancaster wrote:
[quote]"Don W." wrote:

"Dan Bloomquist" <lakeweb@citlink.net> wrote in message
news:3F9FF4BC.3090500@citlink.net...

Harry Conover wrote:

Dan Bloomquist <lakeweb@citlink.net> wrote in message

news:<3F9F0860.3040407@citlink.net>...

I>m waiting to hear what the C + 2H20 -> CO2 + 2H2 efficiency is. If
70%+, that changes things.

Hmmm... I though that this reaction was: C + H2O -> CO + H2, the old
gashouse "Water Gas" process used to produce manufactured illuminating
gas.

How do you modify/re-configure this classic reaction to produce CO2 +
H2 without a loss of energy?

The more perplexing question is that of how to compute efficiency. My
best guess is that one would take the energy yield produced the the
combustion of the CO and the H2, then divide it by the energy
equivalent of the heat of combusion of carbon, in which case I would
predict a thermodynamic efficiency of less than 25% with respect to
the product yield. (Worse still, if the CO is oxidized to CO2 in a
subsequent conversion step.)

Then too, perhaps I>m missing something important which, not being a
chemical engineer, is entirely possible.

Harry C.

Thanks Harry,
I>m not the chemist. I would hope Graham chimes in, he does this best.

Dan.

--
http://lakeweb.net
http://ReserveAnalyst.com
dbAtLakewebDotCom

I>m no chemist too, but I think you simplified a two step process down to
one step. The first step is as Harry described it and the second step takes
the CO and more steam to produce CO2 and more hydrogen.

Don W.

Efficiency is meaningless if you do not also consider loss of exergy.

Being 100 percent efficient at converting high value kilowatt hours into
low value kilowatt hours is pretty much useless.

[/quote]
Converting heat 'high value kilowatt hours' into fuel 'low value
kilowatt hours'. I don>t get it.

Where as efficiency, 50%, says you loose half your heat value. If you
have a better way of turning coal into motor fuel, I>d like to hear it.
A coal powered Stanley Steamer would do I suppose.

If solar is the source, not a terrible deal. But you post the math...

Best, Dan.

--
http://lakeweb.net
http://ReserveAnalyst.com
dbAtLakewebDotCom

Fred B. McGalliard · Guest

"Don Lancaster" <don@tinaja.com> wrote in message
news:3FA091FD.2860723B@tinaja.com...
....
[quote]Efficiency is meaningless if you do not also consider loss of exergy.
[/quote]
Efficiency is meaningless if it is as undefined as exergy can be. I would
stick with the 200 year old definition in your physics text. That should
keep things right up.

No One · Guest

[quote]Electricity from coal nets 35% of the heat value. The electrolysis route
is popular here. Then you would be lucky to see 7% of the heat value of
that coal make it to the wheels of an auto.

Dan, just to be a pain, that>s only a factor of 2 poorer than the
conversion
of gasoline to auto wheels.

[/quote]
Roland, just to be a pain, ONLY a factor of 2! If some offered to increase
your pay or cut your expenses by "only a factor of 2" would you say well
that ain>t enough to fool with?

Cyril Meynier · Guest

Retrouvons en direct "Don W." <dNOSPAMwiddersAThotmail.com>, notre
envoyé(e) spécial(e) sur sci.energy.hydrogen:

[quote]
I>m no chemist too, but I think you simplified a two step process down to
one step. The first step is as Harry described it and the second step takes
the CO and more steam to produce CO2 and more hydrogen.
[/quote]
An interesting proposal is the one that use methane from coal seams.
http://www.ornl.gov/info/ornlreview/vol35_2_02/methane.shtml
(second part)
Dig two wells into a unused (too deep) coal seam or an abandonned one.
Using one well, inject CO2 into the the seam.

CO2 is absorbed into the coal and replace the methane that is catch
using the second well. Then use methane reforming, followed by
water-shift : CH4 + H2O + Heat-> CO + 3H2
CO + H2O -> CO2 + H2 + heat
The capture CO2, for use in the first well.

Each mole of methane is replaced by a mole of CO2 in the seam. And you
get a emission-free (but depletable) source of hydrogen.

However, as said in the site, this ids quite theorical for now. Nobody
can say exactly how much CO2 can be stored and how much methane can be
extracted. So don>t hope industrial use of this system before many
years.

Here in Northern France, two companies (methamine, gazonor) are
already exploiting methane from four coal seams (two are unminable,
two are abandonned). However, they use pumps. The methane is sold to
the natural gas distribution network.

--
"Die Naturwissenschaft ohne Religion ist lahm, die Religion ohne Naturwissenschaft ist blind. "
Einstein

Roland Paterson-Jones · Guest

"Fred B. McGalliard" <frederick.b.mcgalliard@boeing.com> wrote in message
news:HnKvE9.CAv@news.boeing.com...
[quote]
"Don Lancaster" <don@tinaja.com> wrote in message
news:3FA091FD.2860723B@tinaja.com...
...
Efficiency is meaningless if you do not also consider loss of exergy.

Efficiency is meaningless if it is as undefined as exergy can be. I would
stick with the 200 year old definition in your physics text. That should
keep things right up.
[/quote]
I think Don meant 'entropy gain'. Either way, Don clearly has little
appreciation of the concept of exergy.

I have a theory about Don. Phone his number and you reach not him, but some
lacky who answers the phone, trying to sell some of his stuff.

I reckon a lot of the posts on this newsgroup, purportedly from Don
Lancaster, are not written by the Don, but rather by some lacky who has
recognised some words like 'electrolysis', and who has a pro-forma response,
pointing you to the 'guru>s lair'.

http//www.tinaja.com/glib/tanad01.pdf

Don is sailing the Bahamas, resting on his laurels, and good for him!

Roland

--
Roland and Lisa Paterson-Jones
Forest Lodge, Stirrup Lane, Hout Bay
http://www.rolandpj.com/forest-lodge
mobile: +27 72 386 8045
e-mail: forest-lodge@rolandpj.com

[quote]
[/quote]

Fred B. McGalliard · Guest

"Roland Paterson-Jones" <roland@rolandpj.com> wrote in message
news:bo1lr9$q8e$1@ctb-nnrp2.saix.net...
....
[quote]I reckon a lot of the posts on this newsgroup, purportedly from Don
Lancaster, are not written by the Don, but rather by some lacky who has
recognised some words like 'electrolysis', and who has a pro-forma
response,
pointing you to the 'guru>s lair'.
[/quote]
Now that makes sense to me. Thanks.

Bobster . · Guest

Meynier;

Thank you very much for posting this most interesting site, SHEC-Labs.
This method of using the Suns heat to break down water sounds real good.
2004 isn>t very far off.

Bobster

Cyril Meynier · Guest

Retrouvons en direct bobster37@webtv.net (Bobster .), notre
envoyé(e) spécial(e) sur sci.energy.hydrogen:

[quote]Thank you very much for posting this most interesting site, SHEC-Labs.
This method of using the Suns heat to break down water sounds real good.
2004 isn>t very far off.
[/quote]
Their are other similar programs in various countries, but the
interesting feature is the low temperature used here, 400°c
(750Fahrenheit), while other technologies requires 800°c (1500F).

A 800°c source from solar energy requires an advanced receiver design
with very high concentration, obteined using a solar tower with
two-axis tracking (like Solar two is california, PS10 is spain).

400° is easy to get : this is the Temp got with trough parabolic
receivers like in Kramer Junction.

A lower temp means easier (and less expensive) construction, less
radiant heat losses.

--
"Die Naturwissenschaft ohne Religion ist lahm, die Religion ohne Naturwissenschaft ist blind. "
Einstein

Cyril Meynier · Guest

[quote]In this paper, heat is provided at 800°. So Sheclabs must use another
catalyst, since they use lower Temp (400°).
[/quote]
I add that this kind of technology can allow multiu-stage power usage.

Here is what it could look like :

-A primary heat source (solar tower receiver or High Temp Nuclear
Reactor) gives 100 MW(thermal), with a tempertature of 1100°c (2000F).

-A closed Brayton cycle (efficiency : 30%) produces electricity. With
the original 100 MWth, 30 MW(electric) are produced, while 5MW are
lost and 65 MW(thermal) are rejected @ 500°c (930 F)

- A thermochemical cycle uses this heat to split water. 30MW of
hydrogen are produced (250 grams per second), together with oxygen
that can be sold too. 5 MW are lost, 30 MW are rejected @ 180°c
(350F).

- The waste heat is reused for some low-temperature application, like
seawater distillation, or distric heating.

--
"Cette citation n>existe pas"
Beaumarchais, le coiffeur de Barcelone

Philip Felton · Guest

Dan Bloomquist wrote:

[quote]Cyril Meynier wrote:

In the case of methane, (which we already import), it can be used
directly as a fuel. Why suffer the losses by using the hydrogen vector?

Both coal and methane can be turned directly to hydrogen.

from coal :
C + 2H2O ->2H2 + CO2
in fact :
C + H2O -> C0 + H2 (syngas)
A reaction that has been used for decades. It was used around
1900 to produce city gas from coal. Some French build "gazogenes",
devices that used this reaction to run a car using coal or wood during
WWII. Several modern coal-fired plants (IGCC) uses thius reaction and
burn syngas in turbines.
Then :
CO + H2O -> CO2 + H2
[/quote]
Where do you get the idea that coal = C from? CH is more like it.

Phil.

Dan Bloomquist · Guest

You screwed up the headers:

Philip Felton wrote:
[quote]

Cyril Meynier wrote:

Dan Bloomquist wrote:
In the case of methane, (which we already import), it can be used
directly as a fuel. Why suffer the losses by using the hydrogen vector?
[/quote]

[quote]Both coal and methane can be turned directly to hydrogen.

from coal :
C + 2H2O ->2H2 + CO2
in fact :
C + H2O -> C0 + H2 (syngas)
A reaction that has been used for decades. It was used around
1900 to produce city gas from coal. Some French build "gazogenes",
devices that used this reaction to run a car using coal or wood during
WWII. Several modern coal-fired plants (IGCC) uses thius reaction and
burn syngas in turbines.
Then :
CO + H2O -> CO2 + H2

Where do you get the idea that coal = C from? CH is more like it.

Phil.

[/quote]
Best, Dan.

--
http://lakeweb.net
http://ReserveAnalyst.com
dbAtLakewebDotCom


www.GetXFactor.com Leading Technology, Science, Agriculture News and information	Part of the Identityscape.com network... getxfactor.com jmoodmusic.com smartbusinesschoices.com mintdepot.com lowfaresalways.com evangelicalview.com shoppingpodder.com soproudlywehail.com webnews.ws currenthumor.com

Science and Technology news... Forum Index -> Energy - Hydrogen Forum	Goto page Previous 1, 2, 3 Next
Page 2 of 3