Hacker News Reader

Comment by abe_m | Hacker News Reader

I came across this a few years ago. The largest problem is that Ammonia is very toxic. It is also very corrosive. If you look around, there a lots of articles about problems when delivery systems are used to transport ammonia, and then propane. Trace contamination causes failure in propane systems due to corrosion.

So in a crash situation, if the ammonia ruptures, you're probably dead, and everyone else in the vicinity. With gasoline, diesel, propane, or natural gas, if the tank ruptures, people in the vicinity are likely fine if it doesn't ignite. On heavy trucks, ruptured diesel tanks are quite common in crashes. Fires lighting from them, much less common (i.e. most ruptures don't result in fire).

The article is devoid of any comment on the safety aspects, which from what I see, is likely the more important point.

View on HN

This is a very reasonable point, and even somewhat understated, since even when ignited hydrocarbon fuel burns more safely than ammonia. Nitrogenous compounds don't ignite and gradually burn off; they detonate.

Don't try this at home, but IIRC from my mis-spent youth you can light the ammonia gas in a half-empty bottle of household ammonia solution and it will burn off quietly.

According to Wikipedia (which suggests that my memory may be faulty in this case):

"The combustion of ammonia in air is very difficult in the absence of a catalyst (such as platinum gauze or warm chromium(III) oxide), due to the relatively low heat of combustion, a lower laminar burning velocity, high auto-ignition temperature, high heat of vaporization, and a narrow flammability range."

Unlike nitrate compounds such as ammonium nitrate, ammonia contains no oxygen, and disassociates into hydrogen and nitrogen only.

I recall in middle or high school making ammonium tri-iodide with a friend whose dad was a navy seal and knew a thing or two about explosives but nevertheless for some reason thought it was ok for us to make a highly touch-sensitive explosive without supervision. We got the instructions from some variant of the Anarchist Cookbook, and they quite simply instruct you to dissolve iodine crystals in ammonia and filter it, leaving behind a residue of the product. We left it inside a plastic cooler outside for the ammonia to evaporate, which was fine until a gust of wind caused it to detonate and blow up the cooler. I don’t recall us having a plan for how to get the filter out of the cooler without detonating it though, so I’m grateful that it blew up when we weren’t nearby.

> If you look around, there a lots of articles about problems when delivery systems are used to transport ammonia, and then propane.

That's most likely related to meth production. They steal anhydrous ammonia (usually from farmers) and try storing it in propane tanks which are not designed for that. The tanks corrode or crack and then leak or explode.

I've also heard of farmers crashing their tractors into ammonia tanks or train cars of ammonia derailing, but generally speaking, the storage and transportation of ammonia is a solved problem. It's been used for industrial purposes for around 100 years and for agriculture since the 1950s. Based on on what the article said about NOx pollution and aftertreatment systems it's unlikely it will ever be viable for autos or any personal use where safety or risks are more of a concern than they are currently.

While I understand that can be a problem, I'm talking about in legitimate propane distribution infrastructure. An example is here: https://www.lpgasmagazine.com/ammonia-contamination-episodes...

From what I understand, the steel tanks are built to the same standards for both gasses, but ammonia is corrosive to copper alloy valves and fittings. Trucks can be built to haul both and don't use copper alloy fittings. Propane only systems (like home heating systems) contain copper alloy fittings, and the valves and fittings can fail.

Typically the good thing with ammonia is that it's smell is easily detectable by people well below it's toxicity level. I don't think this helps if the tank us crushed and you are trapped inside an upside down car right next to it though.

I think for the most part it is more interesting as a energy storage from renewable overproduction than in cars.

Only if the energy storage facility is far from everything.

A large tank leak and you'll end up killing a whole city.

> So in a crash situation, if the ammonia ruptures, you're probably dead, and everyone else in the vicinity.

I think the assumption is these would be mostly used for stationary power generation / marine vessels, not on-highway vehicles.

Reply on news.ycombinator.com