Why not ammonia, NH3, as liquid fuel?

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

  1. Aqueous Id flat Earth skeptic Valued Senior Member

    Just rolled up

    just found this thread. read about half of it. would like to offer my perspective. the first thing I noticed was a sort of misunderstanding of the question itself. this question really asks if a nitrogen based fuel is feasible. implicit in the question is the understanding that carbon based fuels are harmful to the climate and petroleum itself has become a nightmare. also implicit more in the answers than in the question is the assumption that burning hydrogen exclusively is desirable because the byproduct is clean. I see a hole in this reasoning which I would like to fill.

    my opinion of the question is that it is a good question because it has a noble purpose. my opinion of the answers is that some of them are good, some are faulty in fact or logic or even just bogus.

    I have thought about this question before so I would like to share how I approached it. I think I stumbled onto it maybe the same way billy t did. I was thinking about a hydrogen engine and what might happen if the tank exploded. I was thinking about other ways of transporting hydrogen. it immediately occurred to me that while ammonia has a benefit of transporting more hydrogen than water it has another very important benefit because it is not a carbon based compound. at this point my mind took one more leap. also at this time I was comparing the hazards of gasoline, hydrogen and ammonia.

    what occurred to me next is at the crux of the question. and I don't see that any of you made this connection so I will offer it for you as brain food.

    nitrogen has an interesting property. nitrogen atoms readily bond with themselves in an unusual bond which is called a triple bond. the reason this is relevant is that chemical energy released in a reaction is released in an amount according to the strength of the bond. nitrogen is the lightest element having this strongest bond. so now my mind arrived at the realization that there was something optimal about ammonia. in a controlled reaction 2 molecules of ammonia would produce 1 triple bond plus 6 hydrogen bonds. my recent focus had been on water which yields 4 hydrogen bonds for every 2 molecules. I am comparing the same number of molecules because ultimately I will want to know how much energy is available per gallon.

    It struck me then that ammonia is the first compound you will encounter, as you contemplate the periodic table, which yields so much energy. what I mean by that is that it is the simplest and lightest of compounds that yields the triple bond so there will be a tendency in nature to exploit this. indeed it does seem that the nitrogen in our atmosphere was built by cyanobacteria that were the primordial factories of amino acid production and that they evolved out of an environment that was rich in methane and ammonia. my point is that nature found ammonia and exploited it for a reason and that reason is abundance of nitrogen therefore abundance of the triple bond.

    a good exercise to do to test your basic skills is to calculate the size of a tank of ammonia to get you down the road. it is discouraging because although ammonia is energetic it is not nearly as energetic as gasoline. this is the perennial problem for every kind of alternative fuel until you start considering crazy ideas like explosives or rocket fuel, which give us more atoms of nitrogen per molecule to boost the energy to the levels we have grown accustomed to with gasoline.

    so do not completely abandon this idea. people like the professor from denmark are inventing solutions to problems with energy density and hazards. I would recommend that those of you who are interested in chemistry might want to read up on bond energy, the triple bond, and how to compare an alternative fuel to gasoline in terms of energy density so you can get to the point of calculating the size of a tank because the results will give you some religion, so to speak.

    I mentioned in passing that the ammonia reaction would have to be a controlled reaction.
    what I mean by this is that the liberated nitrogen atoms should not be allowed to mix with air because the result will produce harmful products and probably reduce efficiency. I offer this idea for those of you who were only considering burning ammonia in the air. consider instead a reactor that is sealed to the environment during the reaction then when the reaction is finished purges clean nitrogen gas out the tailpipe.

    yes there are some valid objections. but, if at first all objections must be overcome then nothing would ever be attempted.
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  3. solarbobky Registered Member

    Ammonia Fuel Network

    google "Ammonia Fuel Network"
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  5. Aqueous Id flat Earth skeptic Valued Senior Member

    I did, a found a dearth of practical information, except:

    (1) A risk analysis, leaving ammonia more risky than gasoline, and less risky than LPG.

    (2) A comparison to hydrogen, showing greater energy yield, but showing only conclusions (Figure 1).

    (3) Several studies, but only as vague abstracts, no details.

    Thanks for posting this and welcome to Sciforums.
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  7. chimpkin C'mon, get happy! Registered Senior Member

    Ok...There's a process to turn hydrogen into methane:
    Admittedly not a terribly efficient conversion, I believe I read it's about 50%.
    Now, we already have a natural gas infrastructure.
    Too, cars need about a $500 conversion to run on natural gas...change the tank, alter the jets on the fuel injectors, and I believe that is that.
    Can you link to where it says we can produce ammonia from renewables in this thread? it's a heck of a long thread.
    Ammonia is currently produced from fossil fuels, as far as I know...this is one of the ways our agriculture is so fossil-fuel dependent.
    So...if we can synthesize ammonia, we need to be able to do that anyway to keep our happy butts fed.
  8. Aqueous Id flat Earth skeptic Valued Senior Member

    I think the impetus is to extract hydrogen from methane. Its by-product is CO so there has to be a carbon sequestration to go with that, or it defeats the environmental purpose of using an alternative fuel.

    For maybe twice the energy content per volume, you can apply the hydrogen you get from the above process and take it one step further, by combining it with atmospheric nitogen, in the presence of an iron catalyst, to produce ammonia. This is called the Haber Process.

    And this is also the main way to produce anhydrous ammonia for farm fertilizer use.

    I'm not sure if that cite from solarbobky ever got off the ground. There are several vague abstracts from a couple of years ago. Maybe they never got funded. The most detailed thing I could find, that looked like someone spent a little money on, was the risk analysis.
  9. DIAGONES Registered Member

    I am late to this thread- but it appears that nobody has bothered to look up a bit of history re our space program


    In the 50's and 60,s aero rocket powered planes used Liquid Oxygen/Ammonia as a relatively safe rocket propellent -

    It would seem for landcar use, a equivalent fuel cell or similar ( avoiding the liquid oxygen issue ) might well be practical - since an oxygen rich environment generated by ?? mixed with liquid ammonia could be harnessed somehow.

    Anhydrous ammonia is relatively cheap - but corosive and hazardous -

    However mixed with certain sodium compounds might just be possible to get a exothermic reaction ????
  10. Aqueous Id flat Earth skeptic Valued Senior Member

    The first nitrogen-based rocket fuel that comes to mind is not ammonia, but hydrazine.

    One of the appealing aspects of ammonia synfuel is its existing infrastructure for production and distribution.

    This fuel issue is plagued by the consumer expectation for energy density, set by the best all-around contender, gasoline. So far only hydrogen surpasses that, but it's not easily stored in liquid form, and no one wants to drive a Hindenberg.

    I think the general goals are as follows. First, a liquid fuel can be loaded fairly quickly. So that's an advantage over batteries which need time to recharge. The alternative is a system that swaps out the battery at the station. Assuming this is not around the corner, it leaves the demand for liquid fuel.

    The huge issue is the products of combustion. Nitrogen based compounds offer some hope of eliminating greenhouse gas emissions altogether, but only provided that NOx emissions can be prevented. Sequestering nitrogen is a little less problematic, since ideally it's disposed of as harmless N[sub]2[/sub].

    Ammonia can be thought of as a storage medium for hydrogen. Here is an example of work done using ammonia borane as the medium. It gives up hydrogen and polymerizes. Hydrazine can regenerate the ammonium borate.

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

    Yes, a denser storage. In a gallon of NH3 there is more hydrogen than in a gallon of liquid H2. Basically this is because H2 molecule has only two but NH3 has three and crudely speaking, a gallon of any liquid has about the same number of molecules in it.
  12. DaS Energy Registered Senior Member

    Whilst I agree you get more bang for your buck using Ammonia rather then Petrol, a problem arises in it eats out just about every metal known to man. However that may be overcome by conversion to materials unafected by Ammonia. Leaving only the problem of fuel spillage. Ethanol, Petrol and Diesel are basicaly seen as skin irritant whilst Ammonia will eat you alive.
  13. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    That is somewhat true or at least not totally false if speaking of NH3 gas in high humidity air,* but most large farms have liquid NH3 stored for many years in simple steel tanks.

    * I´m not sure, but think the NH3 somehow accelerates the corrosion water vapor makes as NH3 is a very stable molecule - quite hard to make it react with other molecules.
  14. DaS Energy Registered Senior Member

    Hello Billy T,

    I'm not sure simple steel tanks is correct. However fully agree reguarding farm storage, its a very good fertiliser.

    Eye: lacrimation, edema, or blindness may occur.
    Skin: irritation, corrosive burns, blister formation may result. Contact with liquid will freeze the tissue and produce a caustic burn.
    Inhalation: acute exposure may result in severe irritation of the respiratory tract, bronchospasm, edema or respiratory arrest.
    Ingestion: Symptoms similar to Inhalation. Lung irritation and pulmonary edema may occur.
    Chronic effects: None.
    Extreme exposure may result in death from spasm, inflammation or edema.

    Aluminium Satisfactory
    Brass Non recommended (first found that out watching the brass valves corrode away in DaS Valve)
    Copper Non recommended
    Ferritic Steels (e.g. Carbon steels)Satisfactory (first found that out watching ordinary steel casing corrode)
    Stainless Steel Satisfactory

    Only wish I had found web site before completing first construction of new energy conversion device.

    Cheers Peter
  15. Aqueous Id flat Earth skeptic Valued Senior Member

    Steel tanks are common. In early ammonia based refrigeration they used iron castings, pipe, etc. I can think of one antique in a museum which is probably at least 80 years old, and it still works.

    It can burn the corneas causing blindness, and the lungs, causing serious illness or death.

    The toxicity of ammonia is certainly an issue in contemplating using it as a fuel. It's hard to accept the risk of spilling a toxic chemical, like in a collision, as a liability for gaining a synthetic fuel source. On the other hand, it's probably less risky than having your tank of hydrogen rupture and explode. (Some of this was covered in earlier posts.)

    The alternative might be to place the fuel in cartridges, so, in the event of a accident, they can simply fall away, with little or no release. The only amount that would pose a hazard would be the few cartridges that happen to rupture, plus all the injuries associated with its manufacture and delivery. Such an idea (cartridges) has been proposed for storing liquid hydrogen. Here the problem is somewhat reduced, insofar as the pressure needed to store liquid ammonia is so much easier to achieve.

    Definitely no copper or copper alloys around ammonia.

    Does it work?
  16. DaS Energy Registered Senior Member

    Hello Aqueous Id,

    " Does it work? " Yes it works on any condensible liquid (liquid- gas- Liquid) it also works on any gas (hot gas- cold gas). Gas only requires a gas turbine. Liquid-gas-liquid requires a hydro turbine. Which oddly enough is its greatest problem. To quote Ford Motors Pty Ltd, "we can put your engine on the shelf and take all others off"

    Cheers Peter

    The device in fact is a cross converted gas and electric electric fridge. (see web How things work) The boiler of a gas fridge brings the liquid to temperature of high pressure gas. However instead of putting high pressure against a restrictor plate, which is the same thing the compressor in your electric fridge does, it puts that pressure against a turbine. Cooling is completed in same manner as enjoyed by both fridge type, in that after the gas/liquid is forced through the tiny hole of the restrictor plate it enters an expansion chamber held at vacuum in compressor models. In the case of turbine generator the restrictor plate is replaced by a turbine.

    Please note change in workings between CO2 Critical at temperature below plus 31.2* Celsius and Supercrcritical at temperature above plus 31.2* Celius.



  17. new year Registered Member

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

  19. Mars Rover Banned Banned

    I have read where in the past when commercial and domestic fridges used the Ammonia Absorption method many people died or were hospitalized with serious permanent damage over the years due to Ammonia leaks in confined spaces. Is that true?
  20. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    I of course don´t know, but the leak would need to be a sudden rupture, not thru a tiny crack. NH3 far below lethal levels will drive anyone who can move from the kitchen (the leak area). I am speaking of brief exposures. I don´t think chronic exposure, which could be fatal in a few weeks, would be tolerated either, but not so sure of this.

    Summary: I doubt the report you read.
  21. billvon Valued Senior Member

    The opposite is true. The ammonia refrigerator was developed to overcome the problems with refrigerators of the time, which used mechanical seals to retain very toxic refrigerants. Several people died when the shaft seals failed and the refrigerant leaked out. Einstein and Szilard developed a sealed refrigerator with a less toxic refrigerant to overcome this.
  22. X-Man2 We're under no illusions. Registered Senior Member

    I ran across this BBC article on Liquid Air Energy.Although their discussing it for energy storage for renewable energies,would it work for powering your vehicle? The video at link does show a Man using LAE for powering a car but what are the negatives? There is always negatives huh.

    "The Institution of Mechanical Engineers says liquid air can compete with batteries and hydrogen"

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

    I doubt that on cost basis and efficienct basis also. I was surprised to find this claim:
    Certainly compressing to 2500 PSI will make heat that can be dumped to the air and then expanded back to 135PSI will cool. (Joule -Thomson coefficient of both O2 & N2 is positive but not as good as as CO2.) However, all the heat you dumped was high quality electric power that drove the compressor and you will get only tiny part back by "air fuel" expanding from 135 PSI

    Batteries can give 80% of the input energy back to drive efficient motor Or generator when recoveing braking energy - not going to recover any of that with the liquid air car.

    I.e. I don´t think they have a winner here.

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