Why not ammonia, NH3, as liquid fuel?

Discussion in 'Chemistry' started by Billy T, Feb 26, 2007.

  1. Mars Rover Banned Banned

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    Billy T. If the compression can be done in a system where the heat produced can be used for space heating or for heating a steam generator for piston or turbine engine to run a mill or electricity generator, a lot more of the air compression input energy can be recovered and used that way. And the simple and cheap on board liquid storage and handling makes it even more competitive with more dangerous , complex and costly on-board storage and handling (fuel cells) and expensive Lithium Ion batteries. I wouldn't be so hasty as to rule out compressed/liquid air "battery" systems just yet.
     
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  3. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Well heat recovery would sort of imply small home units in most case and in all cases is direct conversion of electric energy that could have run a heat pump to get several times more home heating with much less complexity than handling liquid air.

    Further more all the energy that runs the car is disguised electric energy - not like say a car running on Natural gas, of other fuel with chemical energy released. Effectively you have an electric car with at best the energy efficiency of ~1/2, probably less than 1/3 that of the all electric cars now on the road now.
     
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  5. Tero Registered Member

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    that sums it up
     
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  7. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    You quote positorn as satating; "3) It is more expensive to produce than Hydrogen" I went back three pages but could not find that. I want to know on what basis that is true. I.e. producion energy required to later get set amount of releasable energy? OR dollars to do same OR per H2 molecule vs NH3 molecule OR per Km etc.

    I also consider "it smells auful" an advantage in that yoj can notice a very tiny leak.

    On 1) it is true that soild bacteria do make more green house damage via production of NOx when NH3 is used as fertilizer to grow corn more rapdly in cold, short growing season, Iowa than the CO2 the corn based ETOH will release as fuel does, but is that the NOx being discussed? We need some comparison releases of NOx if speaking of the release by various fuels. Gasoline , especially in high compression engines makes NOx too. Which would make more, is sort of thing that would be used full to know. Fact that gasoline or ammonia fueled engine makes NOx with no statement about their relative NOx production per mile driven is nearly useless.
     
  8. that guy Registered Member

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    Hey everyone interested in this topic! So I read a few pages of this thread (there's thirteen of them, I don't have time to read them all) and I felt compelled to respond in a way that I really haven't before. So here goes:

    Unless there's some odd sort of chemistry thing that I haven't seen before the combustion of ammonia or release of hydrogen from ammonia and combustion of that must be an exothermic process. However there is no way that it is going to be more energy dense than a carbon based fuel. Redox reactions release energy when electrons move from higher energy states to lower energy states. Both carbon and hydrogen share electrons very evenly, but oxygen is greedy for electrons and pulls them closer to itself and away from hydrogen and carbon. Because electrons are closer to a nucleus in water than they are they are in something like methane they are in lower energy states. A transfer of a hydrogen atom from carbon to oxygen therefore causes the electrons to move to lower energy states and therefore releases energy. You also get energy when carbon binds with oxygen for the same reason, oxygen is greedy for electrons and pulls the electrons around the carbon closer to itself. This is also why carbon dioxide can dissolve in water, the extra electrons around the oxygen cause a net negative charge on both sides of the molecule and the positive pole of water molecules can interact with it easily, but I digress. The crux comes when you do two things; realize that oxygen wants electrons more than carbon, hydrogen and nitrogen because it has more protons, and then take a gander at a periodic table. Nitrogen has more protons than carbon and therefore will not release as much energy in any sort of redox reaction involving oxygen as carbon will. So there's the chemistry side. Ammonia cannot possibly be a better fuel source than a hydrocarbon and if it's not as good as we use now, then it can't be implemented.

    Second point; there's a whole lot more hydrocarbon hanging out in the world than there is ammonia or nitrogen based reduced compound (I'm not saying that you will, but please don't say "all the nitrogen in the air" as energetically you'd be talking foolishly, please read a little chemistry before you say something like that). Some places all you have to do is put a shovel in the ground to get some carbon. I know this isn't what environmental people want to hear, as I'm one of them, but the reason why we use oil is because it's easy. Also we're lazy, but mostly because it's easy.

    Third point; shifting an economy from hydrocarbon based to any other sort of fuel based economy is like trying to steer an aircraft carrier with a paddle. Sure it can be done, and if you're heading towards a rock (metaphorically we are) it has to be done if that's what you can do, but it's going to take a ton of work over a very long period of time. Instead, it might be a good idea to make smarter, more long term sustainable choices like solar or wind. I'm not as up for the nuclear stuff as I used to be, although I do believe it has a place I'm not sure I think that place is on our planet. Unless said nuclear stuff is fusion, if you figure out a way to do that then a lot of these problems cease to matter and you can store your electrons around whatever molecule makes you happy. That being said there are probably some really good arguments for why solar and wind are bad ideas, I've heard things like major changes in desert ecosystems for solar, and the mass killing of bats for wind power. Unfortunately all decisions have an opportunity cost, sometimes it's hard to decide which one to pay.

    All in all great question, lots of smart people doing lots of deep thinking and that's awesome. Good luck to all of you in taking part in our (hopefully) awesome shared future!
     
  9. KitemanSA Registered Senior Member

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    It doesn't need to be. Fossil fuel is an energy source. Ammonia is an energy carrier. It just has to be better than alternative energy carriers such as H2 or batteries.

    I will say air as the source for N2. But that goes into a process like the Haber-Bosch or an electro-chemical process to make NH3 where it becomes a carrier for H. Nobody expects to use nitrogen from the air for energy.

    The time is less "now" than it was last year, if you get my drift. Gas is way cheaper now so the desire for "alternatives" is bound to decrease soon. But at some point in time we will need to eliminate the CO2 from car exhaust. NH3 is one way to do that.

    NH3 is being proposed as a method to store the unreliable energy from wind and solar to make it civilized. The issue is not about a choice between NH3 and W&S. They are potentially complementary.

    The place for current nuclear power plants is in every country in the world, though I do admit I have a preference for Liquid Fluoride Thorium Reactors.
     
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  10. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    To KitemanSA,thank for fine rebuttal to that guy's post 245. - the first post since mine in Nov.2012. I had missed his, most of which is correct and well informed, but this:
    "Ammonia cannot possibly be a better fuel source than a hydrocarbon and if it's not as good as we use now, then it can't be implemented." is not, as you note.

    I can only add that economics, dominates energy minor energy density difference. For example in Brazil almost all cars run on ethanol, even thought it energy density is only 70% that of gasoline because it is significantly cheaper per mile driven. I do that also because it is slightly CO2 negative (Tons of carbon taken from the air are at any time stored in ocean tankers, large tanks at ports, and million plus car fuel tanks) But of course the displacement of gasoline, as car fuel is the huge environmental benefit.

    Sugar cane alcohol is a real threat to oil industry profits, Why fact that it is renewable solar energy, cleaner buring, and slightly more powerful in same IC engine (significantly more powerful in IC of higher compression than gasoline can take without "knocking.") are never much noted. But big oil lies to tell switching to sugar cane alcohol would destroy the Amazon, etc. Sugar cane is of such low value per ton that it can not be profitable if grown more than 300 miles from the distillation plant. None exist less than 700 miles from any rain forest as the distillation plants get located near the demand centers (for Brazil that is Sao Paulo & Rio) so cost of truck distribution to fuel stations does not eat up all the profits.

    Big oil does not attack corn based gasohol as much as it is still 90% gasoline and fact that it is worse for the environment than pure gasoline is becoming more widely known. Iowa has a short corn growing season, so uses a lot of nitrogen fertilizer that soil bacterial convert to NOx, which is not only harmful to health, but a worse Green House Gas than even CH4, which in turn does at least 100 times more GHG damage than CO2 does in first 10 years after a "puff" is released. That excessive use of fossil fuel based fertizer, is part of the reason why Gasohol has such a low RoE, (Energy return on Energy used to make it) of approximately unity (The Cornell study and some others by universities not in corn producing states show corn based alcohol's RoE < 1.0) The larger factor is that, unlike the distillation plants in Brazil where the crushed cane gives more heat than required,* gasohol is distilled from the fermented corn with natural gas heating.

    Note from left chart at end of post that even with free fuel (the crushed cane) which is already at the distillation plant, yet the cost of generating steam is more than three times the cost of the sugar juice, which is much cheaper than from sugar cane (just press it out) than buying enzymes to break down the complex starch of corn and wait for it to act. ("Time is money.") Note buying natural gas for distillation heat is much more expensive.

    Graph is at last 5 years old. RoE > 10 is now common in Brazil and if the cellulose of the crushed cane can make (second generation) alcohol, the RoE and yield per acre may at least double with zero cost to collect from some field as with all other cellulose sources. Thus, none can compete with the crushed cane by large factor.

    * That excess heat generates about 4% of Brazil's electric energy but that is not claimed in the calculations that show sugar cane based alcohol has RoE of about 10.

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    Last edited by a moderator: Jan 20, 2015
  11. billvon Valued Senior Member

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    I disagree. All we need to do is reduce net anthropogenic emissions of CO2. CO2 is no problem; we'd all be dead without it, since plants need it. It is the overabundance of it, caused by the difference between our emissions and our uptake, that is the problem.
     
  12. Photizo Ambassador/Envoy Valued Senior Member

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    By Jove, he's right!
     
  13. KitemanSA Registered Senior Member

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    To a point, I agree with your statement. But having seen many Stankee diagrams of world energy use and source, it seem obvious to me that to get to a balance tween uptake and outlet we will need to eliminate CO2 from car exhausts. I mean this as a net, not a gross. We could do it with bio-fuels. But all my study of THAT path shows they are a no-go except for possibly harvested alge blooms. Even Brazil is killing its forests with their increasing reliance on bio-fuels and hydro power. They need to go nuclear in a big way. If then do, then food crop residue may provide adequate carbon source for syn-carbon fuels to replace petro-carbon. Or, maybe NH3 syn-fuel rather than syn-carbon fuel.
     
  14. billvon Valued Senior Member

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    12,755
    Don't let BillyT hear you say that . . . .

    But in any case, I agree that nuclear is a pretty good option. If we do go nuclear (specifically HTGR nuclear) then we have the option of doing thermal dissociation of water to get hydrogen. And with that feedstock we can make all the natural gas we want via atmospheric CO2 and the Sabatier process. I'd argue that methane is in general a better/easier fuel to handle than NH3, since 1) we have the distribution system in place, 2) it's less of an inhalation hazard, 3) it's pretty easy to store and 4) we already have vehicles that will handle it.

    (Note that in both cases - ammonia and methane - you're just adding some stuff to the hydrogen to make it easier to transport. No net increase.)
     
  15. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Yes. "sugar cane for alcohol will kill the rain forest" is a LIE that big oil promotes to the ill-informed, for obvious reasons.
    (A global switch to that slightly CO2 negative fuel would greatly reduce CO2 release and cost them several billion dollars in lost sales each year.)

    Fact is that sugar cane is a bulky, low-value per truck load, crop that can not be transported, with profit, even 200 miles while the Amazon Rain forest is more than five times that farther away from ALL the distillation plants in Brazil. The distillation plants have been located close to the main markets, Sao Paulo & Rio so trucks hauling the alcohol to the car fueling station (still called "gas stations" as language changes slowly and they do sell some gasoline and diesel too.) can do that economically.

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    If you can't read the scale, that black line in lower right of 2nd graph is 600 miles long.

    Rio is on the coast near the green block in the 1st graph. Sao Paulo is even farther from the Amazon Rain forest. Big Oil, hates the truth that is exposing their lies.
     
    Last edited by a moderator: Jan 29, 2015
  16. KitemanSA Registered Senior Member

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    Hmmm, can you say "straw-man"?
    Where did I once mention the Amazon? Heck, where did I even mention a "rain forest"? Do you think that Brazil doesn't have ANY forest EXCEPT the Amazon? Your map shows that most of Brazil is NOT Amazon. Can we rape all those forests with impunity because they are not the Amazon? Seems a bit warped.

    And associating me with "Bg Oil" is laughable. I believe all petro-carbon should be replaced by nuclear in general and Liquid Fluoride Thorium Reactors in specific... unless Polywell or Focus Fusion (or at the extreme, LENR) pans out. Sheesh, BT, the proper process is ready, aim, shoot; not "shoot anywhere".
     
  17. KitemanSA Registered Senior Member

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    Concur as modified below:
    Strike "HGTR" and replace with "Liquid Fluoride Thorium Reactors".
    Strike "no net increase" and replace with "no net increase with NH3".

    I would also suggest that the NH3 path will be easier in the long run since the N2 is much more easily avilable than the CO2. But algae blooms might be a good way to harvest the CO2.
     
  18. billvon Valued Senior Member

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    Can LFTR's operate at temperatures that allow direct thermal dissociation of water? (the only really efficient way to do it) If so, that would be great.

    N2 is certainly more available than CO2, but we would much rather be generating a reason to pull CO2 out of the atmosphere.
     
  19. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Not directly possible with heat due to limits of materials, but the energy required for electrolysis can be less as part of the water splitting energy is thermal. Thus, far this still has a long way to go before it is conomically competive with production of H2 from natural gas, but there does not seem to be any advantage of H2, even in a fuel cell powered car, over one just powered by natural gas which also is much easier to store in a fuel tank than H2 is.

    Here is some discussion of the energy consideration: http://www.madsci.org/posts/archives/2003-03/1048779104.Ph.r.html

    What we need, is a "Maxwell's demon" that selectively lets only the H ions ALWAYS present in water (Why its pH is 7) pass thru. Then we have and energy producing primary battery as the positive ion becomes neutral - not only getting the H which becomes H2 with still more energy release. That demon will not /can not exist as clearly we would be violating conservation of energy.

    But again NH3 stores even easier and as each molecule has 3 H atoms with about 50% more hydrogen in the liter of liquid. Many decades go some farmer with tank of NH3 fertilized got his IC engine running on pure ammonia vapor - avoided paying the fuel tax too! However the combustion mix is critical, but nothng that modern sensors, fuel injection and computers could not achieve, if he could drive his truck on NH3.
     
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  20. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Photo caption was: Solid black carbon is a by-product of methane cracking.
    A new way to use natural gas with no CO2 release appears possible, perhaps even evonomically attractive:
    And there is a market for carbon powder. I don't see any reason why the 100 -78 = 22% of the CH4 that is not "cracked" on the first pass could not be passed thru the reactor again. Also note that insulation can greatly reduce heat loss to the environment, especially in large reactors.

    The thermal energy released when 4H react with O2 to make two water molecules is much greater than the binding energy of 4H to C in methane. Any chemist worth his salt can give the fraction of H2 that would be the net yield if only it provides the necessary "cracking heat/energy."

    The rest of the hot H2 produced could go directly to the ammonia making reaction (a high temperature reaction too) - This may make a "hydrogen economy" (using dense-room temperature, liquid ammonia) quite attractive as mobile fuel system with zero CO2 release.
    Sugar cane based alcohol does slightly better (slightly "CO2 negative" fuel that runs in existing IC engines with minor changes) but does require land to grow. There is more than enough abandoned pasture, but even better from both health and global warming POV would be if the world eat less beef.

    As Brazil has world's largest cattle herd, and gets ~85% of its electric power from hydro dams and most cars do use alcohol from sugar cane, the main GHG released in Brazil is from both ends of its cattle.
     
    Last edited: Nov 21, 2015

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