It takes considerable energy to decompose NH3. There is net energy release after you get it decomposted by oxidizing the decomposition products, especially the H2 -> H2O reaction. At certain times of the year, tons of NH3 are spread on farms by their owners each day in the USA. That agricultural use is the main market for NH3 in the USA, I think. Yes, NH3 is toxic, but it has such a strong smell that one would leave the area, if a small leak were to develope. Farmers spread it in an water solution, I think. Although one could add energy to each molecule by hitting pure NH3 liquid (which would not be liquid unless inside a presure containiner) I strongly doubt that the energy per molecule possible this way would be even half that necessary to decompose a molecule. You do not seem to understand that the decomposition REQUIRES input of energy. I.e. is an endothermic process. I know little chemisty, but of that I am sure. Can you support ANY of your statements? I bet less than half are correct.
Yeah, I avoid petty squabbles these days. PM me, and post your theories, not contradiction for all to see. Waste of time/effort...<==*Ellipse
Not squabbling. I am sort of a self apointed watchdog at sciforums in that I try to correct errors when I can. {later by edit: Even my own -see next paragraph.} Many will confirm this. Quite a few people lurk here and as retired professor (in part) I do not like to see falsehoods spread. Thus, I post and rarely use PMs - that would be squabbling. Also I want to note that my speculation (I said "I think") that one might be able to put fires out with ammonia is wrong.* (So I have removed that error in prior post.) If ammonia molecules are introduced into a flame, for example as in "flash point" testing, then they do get enough energy to decompose. If there is approximately a 20% concentration of these molecules then there can be a explosion, I think. It of course does require that the ammonia be in the gas, not liquid, phase; but at atmospheric pressure that would be the case. Liquids (and solids) normally will not burn but many will vaporize or thermally decompose and their decomposition products will both burn and provide the heat to decompose more of the solid or liquid so wood, coal etc. can serve as fuels, but they do not burn as solids. Thus I continue to think that liquid ammonia will not burn but the gas will within the limited concentration range you gave. --------------------- *For all practical purposes, but not entirely. If one very quickly floods a small flame (such as a candle) even with a stream of liquid gasoline you can put the candle out. - Very dangerous to demonstrate but dramatically shows that liquids do not burn.
http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=2 ... "Major Hazards * Major hazard : Inhalation and Bodily Contact * Toxicity (Am. Conf. Of Gov. Ind. Hygienists ACGIH 2000 Edition) : 25 ppm * Flammability limits in air (STP conditions) : 15-30 vol% * Odour : Pungent, Irritating * UN Number : UN1005 * EINECS Number : 231-635-3 * DOT Label (USA) : NFG * DOT Hazard class (USA) : Non flammable Gas """ ... Let's stay focused. DEATH Trap. We're not the Venutians. This is ridiculous. But, I feel you may proceed to pursue this, until most are fed up. Then, I'll discontinue my subscription. Build you a little engine bias though, and breath well, of it...
I tend to agree with your point here. I have (in OP) ONLY suggested that ammonia be used to STORE hydrogen economically, never suggested to burn it in an ICE* as some small fraction would still be unburned in the exhaust, making cities uninhabital. What I imagine may be possible is a very well sealed, (but refillable) ammonia tank that within sealed converter produces hydrogen for a fuel cell but has a high presssure stage** condensing any un decomposed ammonia for recycle to the decomposition stage. I.e. only pure H2 and N2 get to the fuel cell. I started this thread to call attention to the STORAGE advantages of ammonia. I.e. is higher density of hydrogen than pure hydrongen and very easy to store as room temperature liquid at modest pressure. ------------------- *That idea came from others. **Perhaps some "molecular sieve" exists that will pass the N2 but not NH3? It is easy to pass H2 thru a metal wall. For example, H2 can (and sometimes is) purified by passing it thru hot paldium. - goes thru very rapidly almost as if there were no wall!
And another thing:::"DEATH Cloud", many plant workers or laughing their MFA off right now. Being a coolant leak of minute traces leads to an Emergency plan. Where if happenchance or improper course of action is succumbed to: You DIE! Toxic, toxic, toxic...
Friends: Be merciful on yo' hade. And, pass not these thoughts. We must live another day. If, however, whomever of ill-logic presses the patent to succeed in this: NICE knowin' ya' I guess. MAY God have mercy on all of Our souls!!! Amen-aimen'...
Perhaps urea, not ammonia, is the way to go for economical, light-weight, mobile storage of hydrogen, but IMHO still, not desirable to use the ammonia one can get from urea as fuel for an ICE. (Small unburnt fraction in exhaust is at least un acceptable irritant if not deadly in urban use. More comments in my last post.(45) Perhaps one needs a cryogentic "cold finger"* in the fuel cell exhaust in addition to the compression and "molecular sieve" preceeding the fuel cell as I suggested in that post to keep the NH3 vapor in the exhaust acceptably low concentration? Crudely put: Drink lots of beer and run your car on piss! Following from http://www.u3kenergy.com/ "...Both ammonia and hydrogen are widely recognized as theoretically attractive alternative fuels. The principal problems they face are safety, storage, transport, and, especially in the case of hydrogen, cost. Urea solves these problems. U3K's technology enables the solution. U3K's patented technology (USPTO 7,140,187) can convert urea to either ammonia or hydrogen for delivery to internal combustion engines and fuel cells in stationary or mobile applications. ... U3K's system can provide internal combustion engines with ammonia or fuel cells with hydrogen "on demand". Urea has many advantages compared to traditional fossil fuels: it is non-toxic, clean burning, non-explosive, and is more economical than refined petroleum products. Urea can fit into the existing liquid based fueling infrastructure. Existing engines can be retrofit cheaply. The capital cost of urea fueling stations is significantly less than the cost of existing gasoline stations. With current urea manufacturing technology, urea has a "well to wheel" efficiency that exceeds gasoline. And urea can be stored as a solid or a liquid. Urea is listed on the FDA's GRAS list, a remarkable fact for a substance which can be converted to clean burning, high octane, and high performance motor fuels with sufficient energy density to match current driving range expectations. Urea engine emissions are principally** nitrogen and water. Greenhouse gas emissions through the entire fuel production/consumption cycle are reduced significantly relative to conventional refined fuels. ..." ------------------- *Some "wiper" continuously collecting the ammonia/water ice that condenses on it for return to the decomposing stage? ** Yes but if that "Minor Component" is NH3, forget it. PS Urea is a white solid. At the self-serve refill station, you buy a bag or two for your car's "hopper" and drop it in and drive off. Faster and safer than a gasoline refill! (Don't forget to save the crumbs for your house plants.) Please Register or Log in to view the hidden image!
That's due to it not burning completely as most fuels. It was also a lead to the fact highly toxic fumes would result. It's kind of like kerosene when it burns. You can see the different layers burning, according to the flow rate given. However, kerosene is not as toxic, and is pretty much safe, given good ventilation.
Ammonia Fuel Cells Ammonia fuel cells do NOT produce nitrous oxide. The most advanced ones crack ammonia into N(2) and H(3) and the hydrogen is used to produce electricity just as in a straight hydrogen fuel cell while the nitrogen is simply returned to the atmosphere from which it came. (Unpolluted, historically natural air is approximately 80% nitrogen.) Further, there have been a number of breakthroughs recently that replace platinum as a fuel cell catalyst, which is both too expensive and too rare for producing commercial quantities of vehicles. There is a Danish company, Amminex, that uses porous metal hydride pellets to absorb ammonia and fuel cell heat to release it. The energy density of this storage approach is greater at room temperature than liquid hydrogen at cryogenic temperatures and consumes less energy to implement than liquid hydrogen storage. It is completely safe as well. It is currently by far the safest and most efficient storage approach using hydrogen as an energy carrier. You could throw a match at these pellets with no negative consequences. There is also already a large transportation infrastructure for ammonia. In addition, there are now breakthroughs in more efficient methods using must cheaper catalysts than the Haber-Bosch process uses in producing ammonia from renewable energy sources such as wind and solar. In brief, there are quite a few dogmatic pronouncements being made in this forum that are ill-informed and/or based on very small pieces of the big picture. One statement on another site even boldly proclaimed that hydrogen must come from fossil fuel, so there is no advantage to using it as an energy carrier. This is pure ignorance. Just because most current commercial production comes from natural gas is not any indication at all that ammonia must or should forever come from fossil fuel. A lot of this kind of ignorant dogma comes from listening to "official" media pronouncements from so-called experts with nasty conflicts of interest and googols of disinformation concerning how far away we are from the kind of technologies mentioned here, when in fact they are only a few short years, if that, from commercial implementation on a large scale. We must learn to inform ourselves and to think more scientifically as well as much more independently. That's a tall order for most, I fear.
Hi rwendell and welcome to sciforums. BTW your’s was the best first post I can remember seeing. I looked into your source: Danish Technical University, DTU, is developing: Amminex Please Register or Log in to view the hidden image! “…ammonia-based solid-state hydrogen storage solution: a tablet that can be held in your hand. The tablet is a metal ammine complex that stores 9.1% hydrogen by weight in the form of ammonia absorbed efficiently in magnesium chloride: Mg(NH3)6Cl2. The storage is completely reversible, and by adding an ammonia decomposition catalyst, hydrogen can be delivered at temperatures below 347º C (656º F). The tablets can be recharged with additional ammonia. … Should you drive a car 600 km using gaseous hydrogen at normal pressure, it would require a fuel tank with a size of nine cars. With our technology, the same amount of hydrogen can be stored in a normal gasoline tank.—Professor Claus Hviid Christensen, Department of Chemistry at DTU The DTU team is finding that the kinetics of ammonia adsorption and desorption with the metal ammine complexes are reversible and fast, and that the complex is simple to manufacture and easy to handle. {BillyT: there is heat released with recharge - perhaps the car's water cooling system can remove it?) For use in a PEM fuel cell, the ammonia released from the tablet would then need to be decomposed to hydrogen, and the resulting gas cleansed of any remaining ammonia (probably by passing it over a small amount of unsaturated MgCl2). Due to the toxicity of ammonia in its liquid form, most recent work on ammonia as a hydrogen storage solution has focused on solids such as ammonia borane. … and polyammonia borane. This family of molecules demonstrates hydrogen capacities of > 12 wt%. …” From: http://www.greencarcongress.com/2005/09/handheld_hydrog.html Another source said: 100 gram block stores 51.7grams of ammonia or about 1/3 is NH3 (at room temp as photo show block held in hand also). Rather than fuel the first use will probably be to clean up NOx in diesel exhaust via: 2NH3 + NO + NO2 → 2N2 + 3H2O The diesel exhaust has much more heat than required to desorb the NH3 from the MgCl2 block, Only small amounts (compared to fuel use) of NH3 are required and system would be a simple addition to the exhaust pipe – no H2 fuel cell needed and no need to crack the NH3 for H2, which is not too hard but is capital cost and complex. For more details, See: http://www.amminex.net/index.php?option=com_content&task=view&id=60&Itemid=131 Final Billy T comments: DTU makes big deal about the volume advantage compared to other means of H2 fuel storage, but the mass of the MgCl2 block carried around constantly in a car is a concern. Pressurized NH3 in a high strength glass fiber tank may be lighter for same NH3 stored. More than offsetting this is the safety factor. I.e. in an accident that ruptures the tank rapid release of NH3 is likely to kill people, but their adsorbed NH3 would only slowly desorb – wind could safely dissipate it. Their moderate temperature fuel cell ideas with cracking part of the fuel cell looks very attractive to me. Glad I started this thread (and that rwendell came along to revive it). – I have known fact that there is more H2 in a fixed volume of NH3 than liquid H2 for many years and certainly NH3 is much easier and cheaper to store. However, a urea based system may win in the final analysis. Perhaps someone will update the referenced link in my post 48 with a summary as I have here for the MgCl2 block storage approach?
Fuel cell alternative catalyst sources... I can't include links apparently, so I will give some Google key words: Breaking the Boundary - A Connection to a Better Fuel Cell Carbon catalyst could herald cut-price fuel cells Next-Generation Fuel Cells Quantum Sphere Formation of Pt-free Fuel Cell Catalyst with Highly Developed Nano-space by Carbonizing Catalase
lol... My chemistry is a bit rustry and so is my physiology... but isn't NH3, or ammonia one of the byproducts of breakdown of urea, or the (NH2)2CO? I guess I could go look up the chemical reaction, but I'll be lazy. Urea is a metabolic end product, which is stripped of its energy in the end. We ingest amino acids (which contain N) and glucose (which contains the carbons and the stored energy in form of excited electrons) and the result is production of heat and ATP, allowing us to generate heat and maintain motor functions and metabolic processes with production of the byproducts urea/ammonia. (Stool is the result of undigested fibers/enzymatic byproducts/biliary waste). I'm not sure the exact same principle could be applied to mechanical vehicles here, because it would almost be like taking the Carbon monoxide that is released and trying to pump it back into the car for energy. Gasoline consists of hydrocarbons, from which the hydrogen protons being released/burned allows for the energy to run the car. As to how efficient it would be to release the hydrogens from ammonia? I guess I don't have enough knowledge in the field of chemistry to be able to answer.
Rwendell's first "goolgle link" has sublink: http://www.sciencemag.org/cgi/content/short/321/5889/671 And only the read for free part of the article in 1 August 08 issue, (with bold added by Billy T) is: "The air electrode, which reduces oxygen (O2), is a critical component in energy generation and storage applications such as fuel cells and metal/air batteries. The highest current densities are achieved with platinum (Pt), but in addition to its cost and scarcity, Pt particles in composite electrodes tend to be inactivated by contact with carbon monoxide (CO) or by agglomeration. We describe an air electrode based on a porous material coated with poly(3,4-ethylenedioxythiophene) (PEDOT), which acts as an O2 reduction catalyst. Continuous operation for 1500 hours was demonstrated without material degradation or deterioration in performance. O2 conversion rates were comparable with those of Pt-catalyzed electrodes of the same geometry, and the electrode was not sensitive to CO. Operation was demonstrated as an air electrode and as a dissolved O2 electrode in aqueous solution. " This really does seem to be something to get excited about. His other google links, especially the second which uses carbon nanotubes, (read that "more costly than Pt," I think) did not look as promising to me. Last link is quite technical - early stage studies. Rwendell must have more than a passing interest in this field. Do you work in it? or just a student doing a good job on some term paper? Anyway - I am impressed with you. keep positing
This was addressed earlier in the thread. You get a net energy release when you break the protons off ammonia and combine them with oxygen to make water. Ammonia is a good fuel, and a good way to store hydrogen.
So that water would be released as... steam? That wouldn't be a bad idea if we could manage to do it efficiently, do you know how much energy would be required to produce the ammonia in usable means?
Whether the product is gas or liquid would probably depend on whether you are actually burning it with oxygen or combining it with oxygen in a fuel cell. The standard enthalpy of formation for ammonia is listed earlier in the thread.
I can think of some more since then, lithium ion has been improving in leaps and bounds, zinc and metal air fuel cells have great potentials but still horribly ignored option.
To ElectricFetus: Your comments on NH3 need revision in light of the progress reported in post 52. For example, when "disolved" in their porous MgCl2 the particial pressure is so low you can hold NH3 IN YOUR HAND, assuming you are in a well ventlated space or outdoors.
