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Navy Creates Fuel From Seawater
New submitter lashicd sends news that the U.S. Naval Research Laboratory has announced a successful proof-of-concept demonstration of converting seawater to liquid hydrocarbon fuel. They used seawater to provide fuel for a small replica plan running a two-stroke internal combustion engine.
"Using an innovative and proprietary NRL electrolytic cation exchange module (E-CEM), both dissolved and bound CO2 are removed from seawater at 92 percent efficiency by re-equilibrating carbonate and bicarbonate to CO2 and simultaneously producing H2. The gases are then converted to liquid hydrocarbons by a metal catalyst in a reactor system. ... NRL has made significant advances in the development of a gas-to-liquids (GTL) synthesis process to convert CO2 and H2 from seawater to a fuel-like fraction of C9-C16 molecules. In the first patented step, an iron-based catalyst has been developed that can achieve CO2 conversion levels up to 60 percent and decrease unwanted methane production in favor of longer-chain unsaturated hydrocarbons (olefins). These value-added hydrocarbons from this process serve as building blocks for the production of industrial chemicals and designer fuels."
All US carriers are nuclear-powered, and being able to synthesize aviation fuel would drastically reduce the logistics cost of operating them.
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
Next step is to find a country where they have too little democracy but a lot of this "seawater" they mention.
Curiously yours, crip.
This article is linked in the story article. It has a lot more info on the process.
http://www.nrl.navy.mil/media/...
TFA was points to a 2012 press release, but it contains not much more information. They must need to supply energy to this reaction, but whether this energy is as heat, electricity or something else is unclear.
I see two uses from the point of view of the U.S. navy. One is to put one of these chemical plants in an aircraft carrier, power it with the carrier's reactor, and generate fuel for the aircraft on board. The other is to put the chemical plant on a nuclear powered supply ship, which will then transfer the fuel to non-nuclear surface ships.
From a world energy point of view, this is a way to turn non-fossil fuel power (nuclear, hydro, wind) into hydrocarbon fuel, with the overall process being carbon neutral. Burning fossil fuels to provide the energy for this process would certainly be counter productive in terms of CO2 emission and very likely economically counter productive as you'd be better chemically processing your fossil fuel instead.
By the time you're going to all of this trouble to turn electricity into fuel, it is unlikely that you'd want to run a car on it - you'd rather just have an electric car. For aircraft we really have no good alternative to hydrocarbon fuels, so it could be used here. However, on the road to a low-carbon future, we have decades worth of lower hanging fruit (notably coal power stations) before we really need to care about whether our aircraft fuels are carbon neutral.
Conspicuously missing from the articles is the energy efficiency of this process. Given the $3-$6 per gallon projected jet fuel cost, presumably the efficiency is not too bad. (I notice this number hasn't changed since 2012 which makes me suspicious that it is more guesswork than calculation.)
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You do realize that what they're producing here is artificial jet fuel, right? It's not "biofuel" because it isn't produced by bacteria or algae or other direct biological process. No, what they're talking about here is essentially the water gas shift reaction whereby dissolved CO2 in the seawater is combined with water vapor (aka steam) and carbon monoxide (produced via this "bicarbonate" reactant?) to yield carbon monoxide, carbon dioxide and hydrogen which more heat and pressure (steam) in the presence of an iron catalyst converts these products into short chain hydrocarbons (alkenes), probably ethanes (CH3) and propanes (CH4), and from there longer chain hydrocarbons with more heat and pressure until the desired blend is cooked up, jet fuels of CH9 to CH16. However, these processes don't really transition us away from fossil fuels or at least not into something besides a hydrocarbon fuel, whether produced artificially as in this case or refined from naturally occurring crude oil that we've pumped out of the ground.
What I'm wondering is, can they modify this process to produce edible hydrocarbons? Probably not something you'd enjoy eating, but the primary limitation on a nuclear submarine's endurance is the food supply for the crew.
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At least it's part of a CO2 cycle, not some new CO2 we dug out of the ground.
No sig today...
Chlorine gas is toxic. It was used in shells to poison troops in WW1.
Whereas both hydrogen and oxygen are perfectly safe and have never been known to case any sort of problem whatsoever... well, ok, there was the Hindenburg, and Apollo 1, and...
So if you do the described experiment while locked in a badly-ventilated room, leave it running for long enough to increase Ever Ready's share price by 1%, ignore the eye-watering stink that even a whiff of chlorine will produce and then light a cigarette, you could be in real trouble. If only from all the crap in the cigarette smoke...
However, all this pales into insignificance alongside the experiment's reckless use of the liquid death that is Dihydrogen Monoxide!
Seriously, guys, when everything is described as dangerous, nothing gets treated as dangerous. If you're not sure what it is, don't wait for someone on the internet to tell you not to snort it.
In a survey of 100 programmers, 111111 thought that duck-typing was a good idea.
4th grader in what country? Your USA-centrism is showing.
In other first world countries; any 2nd grader should know this.
china's plan to convert coal to hydrogen to methane is about 50 percent energy efficient. For big commercial aircraft, it will be better to use liquid hydrogen directly.
The problem with this is that it's cryogenic with an extremely low boiling point of 20 K (Kelvin). You would have to carry a much heavier tank and insulation for the liquid hydrogen on the aircraft. There's also hydrogen leaks and transport of it to the airport from wherever it is produced.
You would also need to handle boil off of hydrogen while the plane is on the ground and the hazards of handling extreme cryo fluids, which is much more dangerous than handling jet fuel/kerosene. For example, oxygen condenses at 50 K meaning a poorly insulated tank (say due to damage inflicted while conducting maintenance) could be condensing liquid oxygen inside the plane's wing.
Further, there isn't a good reusable tank material for handling liquid hydrogen. Composites weaken over time due to gas pockets in the composite material (and thermal cycling) while metals such as aluminum are subject to hydrogen embrittlement.
I think there would be a huge redesign of aircraft in order to use liquid hydrogen directly. Thicker wings say from a flying wing design would be more fuel efficient.
There would probably also be huge logistics changes. Fuel tanks would probably have to be kept at extreme cryo temperatures indefinitely (including overnight) in order to prevent thermal cycling. You couldn't have the aircraft sit on the tarmac for hours because it would either lose too much fuel due to boil off or require considerable refrigeration power to keep boil off from happening. A traffic jam combined with a hot day and loss of grid power, would be a disaster for an airport.
Meanwhile methane can be converted to normal jet fuel with some additional loss of energy. For example, a coal burning plant/refinery on site of a coal mining operation could produce methane or longer chain hydrocarbons directly.
And at the current state of affairs, the cheapest hydrogen source is methane. Any plan for creating hydrogen from water is going to run into a similar degree of energy loss as that of converting coal and water to methane and syngas.
At sea refueling is trivially easy, all you need is a ship that can carry a lot of fuel, a pump, and a hose.
"Trivially easy"? I think the Navy would disagree strongly with you on that. There are a huge number of non-trivial logistics issues. You have the expense of maintaining a second ship. You have to have that ship transport the fuel to an arbitrary location on the globe. You have to keep the fuel supply safe and ensure that the fuel tender isn't tracked back to the ship it is refueling. You have a ship with a large amount of potentially explosive fuel on board with all the attendant safety hazards that causes. It means your ships are limited in where they can go and how long by their fuel supplies rather than mission parameters.
The fact that they're fairly good at doing it doesn't mean it is something they find easy or useful. Cut of a military's fuel supply and they are effectively helpless. Fuel logistics are a HUGE and expensive problem for the military. It supposedly costs something like $16 to transport $1 worth of fuel. Also bear in mind that a lot of fuel comes from pretty volatile locations that we are likely to engage in hostile action with. There is a reason our military is putting a LOT of money into alternative fuel research. It's a huge cost and a huge tactical/strategic problem for them.
And realistically, when is a carrier or other ship likely to be far from supply lines?
Middle of the Pacific perhaps? Or any other ocean? Or when near hostiles? You don't really want to be refueling anywhere close to the people you are fighting if you can avoid it.