Why not ammonia, NH3, as liquid fuel?

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

  1. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    A jug of ammonia (Not hard to keep liquid at room temperature with modest pressure.) has more hydrogen in it than a jug of pure liquid hydrogen!* (which is very hard to keep liquid even with huge pressures and very cold temperatures)

    When you decompose ammonia (NH3) you get heat and can throw the N2 formed into the air and even Green Peace’s idiots** know that is OK.

    The resulting H2 can be burned to H2O, which also is harmless to discharge into the air.

    Ammonia is relative cheap to make - if it were not farmers would not be injecting solution of it (I think) into the soil of their farms. - I think that is the major commercial use of NH3 today.

    I am not much of a chemist, but can someone who is tell me why do we not use these facts to make ammonia fuel for cars and trucks, etc?
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    *True because each molecule has 3 atoms of hydrogen, instead of 2 in it.
    **The ones that have blocked the development of safe nuclear power in US for 30+years with the net result that much more CO2 has been dumped into the air and global warming is now a serious enviromental problem, not to mention all the SO2 that has been released, killing fish in Adrondac and N. European lakes, even killing some forests with the "acid rain" SO2 becomes. etc.
     
    Last edited by a moderator: Feb 26, 2007
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  3. Plazma Inferno! Ding Ding Ding Ding Administrator

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    My contribution, although I'm not chemist.

    Ammonia fuel cell

    United States Patent 7157166

    This invention refers to generating electrical energy comprising an ammonia fuel cell for generating electrical energy including a catalyst being in contact with a high temperature proton conducting membrane and the catalyst comprising at least one decomposition catalyst which causes NH[sub]3[/sub] to decompose to N[sub]2[/sub] and H[sub]2[/sub] and at least one catalytic anode which dissociates and ionizes H[sub]2[/sub] into H[sup]+[/sup] and electrons, the fuel cell further including at least one catalytic cathode for reaction of H[sup]+[/sup], electrons and oxygen to form H[sub]2[/sub]O, an external circuit from the catalytic anode to the catalytic cathode, an ammonia source for introducing ammonia into the fuel cell, a gas exit for N[sub]2[/sub], and an oxygen source.


    Also, Ammonia Cracker has been developed two years ago by Apollo Energy Systems to extract hydrogen from ammonia for fuel.

    More here.
     
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  5. Roman Banned Banned

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    Creating the fertilizers (NH3) that farmers use requires a great deal of energy. Energy we get from fossil fuels.
     
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  7. MetaKron Registered Senior Member

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    Right now, most ammonia is manufactured from hydrogen and nitrogen, using a lot of electricity. Not much use cracking ammonia to get a raw material that it is manufactured from.

    http://en.wikipedia.org/wiki/Ammonia
     
  8. Positron Agony: Not all pain is gain Registered Senior Member

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    Here are some of the reasons for not using ammonia as opposed to hydrogen

    1) It puts off Nitrous Oxide which is very bad for you

    2) It smells awful

    3) It is more expensive to produce than Hydrogen
     
  9. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Can yo say a little more on (1)? Are you just referring to the NOx that is made when any fuel is burned in modern high compression / high temperature engine, or something specific to HN3?

    On (2) THIS IS AN ADVANTAGE. In higher concentration it will kill you. It must be keep under compression at all times and if a small leak does occur, the strong smell can save your life.
    Contrast this with the oderless CO that kills a few people every year. (Often they were keeping warm with the car's gasoline motor running while stuck in snow drift that blocked the dispersion of the exhaust, helped it seep into the car. That will never happen with ammonia, thanks to the smell and fact neither H2, & N2 nor H2O products of this system (as I understand it) are toxic.

    On (3) and in answer to Metkron also:
    Probably true NH3 is more expensive to make (as there is more stored energy stored in each molecule), but againthat is an advantage.
    Important point to keep in mind is:
    Both H2 and NH3 are energy transport systems, not energy sources.
    - Clearly when the cost of transport is included, room temperature NH3 system is much cheaper and much lighter in the car for much better fuel milage performance.
     
    Last edited by a moderator: Feb 27, 2007
  10. Nasor Valued Senior Member

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    It would work great if you could get some kind of catalyst to help you break down the NH3 into N2 and H2. As is, there is no good way to do it. It would take you more energy to get hydrogen from the NH3 than you could hope to get back by burning it.
     
  11. Positron Agony: Not all pain is gain Registered Senior Member

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    I suppose the smell could be a good thing but with combustion the products of the reaction must go somewhere. It would not be efficent to "can" it in another part of the car because not all will be used up. As for the NOx put off. Something is put off for all reactions. CO2 is put off from Combustion with gasoline and NOx is just what would be put off burning ammonia.
     
  12. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    I do not envision burning NH3,not even sure it will burn. One decomposes it and throws the very low cost, efficient, light-weight (compared to metal hydrides, cryogenic / very high pressure tanks, etc. H2 requires) "transport system" I.e. the nitrogen, as N2, away.

    Both H2 and decomposed NH3 can be used in fuel cell electric moter car to proproduce zero NOx and in principle as not Carnot limited, more efficiet cars - perhapse more that twice as efficient as the 30 to 35% Carnot limited IC engine cars of today, but practical economic consideration (do not use lot of copper in the motors etc.) may limit the real world efficiency to only twice that of current cars.

    Nasor I do not remember the details, but a catalytic decomposition system is well developed. - I read about it years ago - why I know the decomposition is exothermic. Probably, Plazma Inferno's patent reference tells at least one also.
     
    Last edited by a moderator: Feb 27, 2007
  13. Positron Agony: Not all pain is gain Registered Senior Member

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    On a small scale in a car, compressed tanks could be dangerous unless properly sheilded and this will hike the price of the car. As for "burning" the ammonia it is just a term I use for using something as energy in casual chemistry speak.
     
  14. MetaKron Registered Senior Member

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    This one might make sense. Couldn't there also be a cycle to use the released hydrogen?
     
  15. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    I think you need to keep your thoughts separate to avoid confusion:

    Burning can mean oxidation in a fuel cell, I admit, but if you want that to be understood, say that.

    I also think that "burning ammonia" meansjust that - not decomposing ammonia and then either buring one of the decomposition product in an IC engine of a car OR using it as the fuel of fuel cell.

    Even the discussion of the two catalyist fuel cell (in Plazma's post) keeps it clear that it is a two step process - decomposition followed by fuel cell use of the hydrogen.

    no one can tell what you ae saying if you fail to distinguish these concptually different process by calling them all "burning" - at least I was not able to tell what you were referring to.

    As far as your comments about the "ammonia car" - I agree that it would be more expensive, but note that the gasoline IC engine has had more than 100 years of development to bring the cost per horsepower of capacity down. Might be more fair to compare both systems after 10 years of progress in development of each.
     
    Last edited by a moderator: Feb 27, 2007
  16. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Yes. For example, if nuclear power were used to first produce H2 from electrolysis and also at the power plant, this H2 and N2 from the air were made into NH3, it could be sent long distances with less loss (and in hidden under ground pipes)* to cities and then distributed thru (in some cases existing natural gas pipelines) to individual homes where small fuel cells provide both heat (for making hot water etc) and electricity.

    Certainly a transform of the existing energy system, more costly at least initially, but with zero release of CO2 and much higher efficiency than the current system which wastes at least 2/3 of the energy by the time it is used in the home.
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    *Always amazes me how "ugly" many view the graceful aerodynamic wind generators yet say little about power line marching across the landscape, some time even building their homes along these lines.
     
  17. MetaKron Registered Senior Member

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    OK, I made a mistake and should have read the link.

    The ammonia cracker makes sense. Apparently it doesn't even have to use electricity. Too bad it won't generate enough power to actually liquefy the hydrogen.
     
  18. francois Schwat? Registered Senior Member

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    I once had an adjunct teacher in high school physics. He was a real greeny hippy type. You could just tell by his whole attitude and he was only well-dressed and shaven so he could be a teacher. He did Peace Corps and taught classes to kids in Tanzania. He was in class one day expressing in a matter-of-fact tone that we could easily be driving water-powered cars if it weren't for the big oil and the powers that be. He's like, "Water has hydrogen! We can use the hydrogen to power our cars!"

    "I'm like, but it requires energy to separate the hydrogen from the water. Water, itself as it is, is not a viable fuel. The energy that goes into breaking apart water into its constituent atoms is what make hydrogen and oxygen volatile chemicals. Its constituents atoms are volatile because they can be used as fuel. It's energy potential is often what makes a fuel volatile."

    The guy was like, "Nope. We could have had water-powered cars in the 70's."

    My real physics teacher understood what I was saying and knew I was right, but didn't say anything.

    I guess the main question is, how easily can the hydrogen atoms be stripped off the ammonia molecules? Obviously energy is needed to break the bonds, to separate the hydrogen from the nitrogen, just like energy is needed to break the bonds of hydrogen from oxygen in water. But how much energy is needed to do it? If too much energy is needed, then it might be a completely fruitless endeavor. On the other hand, it might use very little energy, in which case ammonia might be a very good idea.

    However, just because ammonia contains a lot of hydrogen doesn't make it a good potential fuel.
     
  19. MetaKron Registered Senior Member

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    I think we're better off with engines that don't rely on internal explosions to combust the fuel. Hydrocarbons are only a problem because of soot. I have thought for a long time that steam engines are a better choice for powering hybrid electrics for that reason, that they can generate less pollution and the storage battery keeps the driver from having to wait for them to warm up.

    The creation of ammonia is an endothermic process. Releasing the stored energy is exothermic, so the generation of electricity by cracking ammonia can work, as the article referenced above says. The Wikipedia article says that ammonia has also been used as rocket fuel with liquid oxygen for the oxidizer.
     
  20. Positron Agony: Not all pain is gain Registered Senior Member

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    Billy, I apologize for any confusing tones that came off from me and I will try not to do it again. I agree that if ammonia is used extensivley in cars the cost will indeed be much cheaper. Unfortunatley it has been hard to get America on the track to hydrogen as an alternative fuel and any switches on that may confuse people as to think we don't know what we are doing. If the people do not support it the people in Washington will just keep going with something that can fatten their wallet. But, i'm straying from the chemical point of this thread. Ammonia is surely an alternative scource of energy but just about everything is or can be with proper reasearch.
     
  21. Nasor Valued Senior Member

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    Thermodynamically, you release energy when you go from 2 ammonia molecules and 3 oxygen molecules to 6 water molecules and 2 nitrogen molecules. So from an energy standpoint, it could work.
     
  22. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    I am not a chemist but have read that the catalytic decomposition (at high temperature, I think, but that is not a chronic energy requirement for an exothermic process, if well insulated.) is an exothermic process. You could check this by comparing the binding energy in two molecules of NH3 with that in an N2 and 3 of H2*. I.e. six N-H bonds broken in the two NH3s and four stronger ones formed. I.e. you are forgetting the fact that twice as many new bound molecules are formed for those decomposed. - That is why I do believe what I have read about decomposition being exothermic.

    by edit - I now see Nasor just said the over all process (water and N2 as final products) is exothermic, but even only the decompositioon stage is exothermic I believe and told above how to check.
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    *I do not know if it is correct or not, but as a physicsist, I tend to think of H2 as sort of like deterium in mass and sort of like helium in electronic configuration. I.e. has two protons keeping apart by electo statics and two electron going around this "split He nucleus" in the same n = 1 ground state as one is spin up and the other is spin down and Pauli (exclusion principle) is happy. Thus very strongly bound, I think, H2 is.
     
    Last edited by a moderator: Feb 28, 2007
  23. Nasor Valued Senior Member

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    Actually it's endothermic to go from 2 NH3 to 1 N2 and 3 H2. So if you use ammonia as a hydrogen source you actually pay an energy penalty when you liberate the hydrogen from the ammonia, but you more than make up for it in the second step where you combine the hydrogen with oxygen.
     

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