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KAUST researchers show blending ammonia with DME yields low-carbon fuel with combustion properties similar to gasoline

Blending ammonia with a small amount of dimethyl ether (DME) gives a liquid fuel with low-temperature combustion properties very similar to gasoline, researchers at KAUST have shown. The development of such fuels could provide an option—in addition to electric cars—for “clean” power for the transportation sector. A paper on their work is published in the journal Renewable Energy.

Ammonia as a fuel provides a promising outlook to reach zero-carbon emissions, but its certain characteristics hinder its direct application in combustion devices.

—Binod Raj Giri, corresponding author

Pure ammonia has a high autoignition temperature and narrow flammability limits, but these combustion properties can be modified by blending it with a secondary fuel.

The objective is to find the optimal promoter, which provides the best performance in terms of efficiency improvement and emission reduction while being added in as small of a fraction as possible.

— Professor Aamir Farooq

The team showed that DME could be one such promoter. It burns cleanly, with a much lower autoignition temperature than ammonia, and can be produced in a sustainable net-zero carbon cycle.

The team found that an 18% molar blend of DME in ammonia mimicked the low-temperature combustion behavior of representative gasoline fuel. The blend could be suitable for ammonia-fed compression ignition engines at higher DME concentrations, although flame instabilities could be an issue for higher DME content at elevated pressures.

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We showed that DME can strongly promote the combustion behavior of ammonia and that a proper blend can be a promising fuel to achieve a net-zero carbon emission. This particular blend can be very suitable for ammonia-fed spark ignition engines.

—Binod Raj Giri

The researchers also developed a chemical kinetic model of ammonia-DME fuel-blend combustion based on their experimental findings. Such models could be used to optimize fuel-engine interactions to design high-efficiency future ICEs and achieve net-zero CO2 emissions, Farooq said.

Overall, our kinetic model offered reasonable predictive capabilities capturing the experimental trends over a wide range of conditions. In the worst-case scenario, our model underpredicted IDTs by a factor of ∼2.5 while overpredicting laminar flame speed by ∼20%.

—Issayev et al.

The team is also investigating blends of ammonia with other additives such as hydrogen, methane, propene, dimethyl ether, diethyl ether and dimethoxy methane.

Resources

  • Issayev, G., Giri, B.R., Elbaz, A.M., Shrestha, K.P., Mauss, F., Roberts, W.L., Farooq, A. (2022) “Ignition delay time and laminar flame speed measurements of ammonia blended with dimethyl ether: A promising low carbon fuel blend.” Renewable Energy 181, 1353 -1370 doi: 10.1016/j.renene.2021.09.117

Comments

William Taylor

Almost anything will be better than batteries!

sd

Almost any "green" solution will consume more power and be more expensive than batteries.

mahonj

If we can find an economical way of making a liquid, mostly ammonia fuel, it could be useful. I wonder could you
I wonder how safe it is if you spill or sniff it?
From Wikipedia:
"Dimethyl ether is also relatively non-toxic, although it is highly flammable. BASF Explosion Disaster on July 28, 1948 in Ludwigshafen was caused by this compound – 200 people died, a third of the industrial plant was destroyed"
want to be careful there.

Lad

Oil Executive: "Give me anything but batteries, I'll even take Ammonia!"

GdB

Rather than displace battery EVs, this could be a great way to allow retrofit of the ICE car manufacturing base for little cost, as a sto gap before low cost LFP EVs take over.

Gryf

This would be a great fuel for Marine and Aviation applications. Wartsila is already building engines for Ammonia and Methanol.

sd

Maybe something similar to this will find use for "Sustainable" Aircraft Fuel (SAF). I think that it is possible but less likely to find use for marine fuel. However, it is extremely unlikely to find use for on-road vehicles. Batteries are getting better and the cost is much less. Being green is great but, in the end, economics are a much stronger driver. The cost of driving my Chevy Bolt is about 2.5 cents per mile (4.3 miles per kW average and 11 cents per kWhr) plus no maintenance other than tires should not be lost on anyone.

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