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#1 malbear

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Posted 24 January 2021 - 20:30

has anybody any experience with NH3 as a fuel. pro and con discussion http://www.nh3car.com/index.htm



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#2 Greg Locock

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Posted 25 January 2021 - 00:17

Is this what you are talking about https://www.sciencem...-without-carbon

 

So as far as cars go, you split the ammonia into nitrogen and hydrogen, and then use the hydrogen in a conventional fuel cell.

 

If it works out on a commercial scale then it makes BEVs look a bit sad, in some cases. But all 3 processes are a bit underbaked at the moment - the ammonia production is inefficient (I don't care about that) and uses weird chemicals. How does a NH3->H2 reformulator work? how efficient is that (I do care about that). And finally fuel cells seem very do-able, but due to lack of fuel or purpose they are still fiendishly expensive. So I'd randomly guess 10-15 years from production if there are no major blockers.

 

CSIRO are working on pV to H2, ie electrolysis, but the problems there are known, and hard.

 

However if you mean burning it directly in engines then the big problem will be NOX. https://cen.acs.org/...s-planes/98/i31



#3 TDIMeister

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Posted 03 February 2021 - 20:01

You can also burn NH3 directly in an engine without splitting it first to its constituents. There's some research in using it in farm machinery, since ammonia is widely available and used for fertilizer production. There's also discussion about burning it in jet engines for aircraft and in ships (with modifications to the engines, of course) as carbon-neutral, sulphur-free alternatives to jet fuel and fuel oil, respectively.

 

As likely already covered in the above articles, the main headline attraction is carbon neutrality. However, most industrial ammonia is produced by the Haber–Bosch process, an endothermic process whose thermal energy resource typically comes from natural gas. The lifecycle is therefore decidedly not carbon neutral.

 

As a fuel in combustion engines, it has appreciably lower volumetric and gravimetric energy content compared to hydrocarbon fuels. Ammonia is said to have a high effective octane rating, but it burns with a very slow laminar flame speed. Ammonia slip through the exhaust (unreacted ammonia analogous to HC emissions) is extremely toxic in sufficient concentrations. It burns with a relatively cool flame, which is a positive for NOx emissions according to the Zeldovich Mechanism, but countering this effect is the much higher reactant concentration of nitrogen species, which shifts the reaction kinetics towards the product side (favouring NOx formation).

 

https://www.scienced...540748918306345



#4 Greg Locock

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Posted 03 February 2021 - 22:34

Is NOx a problem anywhere but cities (Sorry I'm feeling lazy)? If NOx is a city problem, and NH3 via a clean process is practical, then EVs for cities and cars, NH3 burners for long distance haulage and ag and edge cases where EVs don't cut it. (Quiet grin - the internal combustion engine lives on!). However that is a whole stack of ifs and unknowns.

.



#5 TDIMeister

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Posted 04 February 2021 - 04:06

I for one follow Greg's optimism that ICEs will live on quite a while in the future - but maybe not in passenger cars or light-duty transport. I am writing papers for conferences (SAE and ASME) this year that will introduce ICE concepts that emit absolutely ZERO carbon, NOx, PM, HC and CO emissions. In one concept, the exhaust (water from burning hydrogen) is right around ambient pressure and temperature at the boiling point rather than several hundred degrees higher, which can be directly exploitable for CHP. Yet, the peak temperature of the cycle is over 3000 K. And it does this without any particular mechanical wizardry.

 

Sounds absurd? Stay tuned. 


Edited by TDIMeister, 04 February 2021 - 04:08.


#6 malbear

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Posted 04 February 2021 - 04:09

Is NOx a problem anywhere but cities (Sorry I'm feeling lazy)? If NOx is a city problem, and NH3 via a clean process is practical, then EVs for cities and cars, NH3 burners for long distance haulage and ag and edge cases where EVs don't cut it. (Quiet grin - the internal combustion engine lives on!). However that is a whole stack of ifs and unknowns.

.

 

NOX has a natural cycle from the effect of lightning 

https://www.scienced...on metric tons.

 

 

so if NH3 is a slow burner then prolonged constant volume and high swirl or both would be advantageous during combustion


Edited by malbear, 04 February 2021 - 04:10.


#7 TDIMeister

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Posted 04 February 2021 - 04:29

so if NH3 is a slow burner then prolonged constant volume and high swirl or both would be advantageous during combustion

I'm sure @manolis has concepts to address both. :)



#8 malbear

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Posted 04 February 2021 - 04:39

I'm sure @manolis has concepts to address both. :)

so do I  :cat:



#9 TDIMeister

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Posted 04 February 2021 - 04:39

Is NOx a problem anywhere but cities (Sorry I'm feeling lazy)? If NOx is a city problem, and NH3 via a clean process is practical, then EVs for cities and cars, NH3 burners for long distance haulage and ag and edge cases where EVs don't cut it. (Quiet grin - the internal combustion engine lives on!). However that is a whole stack of ifs and unknowns.

You're right, Greg, NOx is arguably more of an urban problem because of the concentration of emitters, and also in certain geographic locations than others (e.g. the southern California airshed).

 

For NOx emissions, the proponents point out that ammonia-as-fuel already provides the required reactant for selective catalytic reduction (SCR) systems - the urea in AdBlue/DEF breaks down to NH3 at elevated temperature and it's the latter that is the active ingredient for SCR to reduce NOx.

 

NH3 slip can be (and is already) addressed in modern Diesel engines and powerplants with selective catalytic reduction systems equipped with a dedicated ammonia-slip catalyst, not much unlike the familiar oxidizing catalyst.

https://ac.umicore.c...-slip-catalyst/



#10 TDIMeister

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Posted 04 February 2021 - 04:40

so do I  :cat:

Do tell!



#11 gruntguru

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Posted 08 February 2021 - 20:54

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