Navy plans to make jet fuel from sea water

Nydoc · Post by **Nydoc** » Wed Nov 14, 2012 7:04 am

It's an old article, but still interesting:
http://www.nrl.navy.mil/media/news-rele ... o-the-seas

KitemanSA · Post by **KitemanSA** » Wed Nov 14, 2012 12:19 pm

They could get something like 90% of the effect if they were to convert their LM2500s and RR equivalents to burn ammonia and just make the ammonia. MUCH simpler. Every strike group would have an AON (auxiliary oiler, nuclear) or maybe an AOF.

D Tibbets · Post by **D Tibbets** » Mon Nov 19, 2012 1:32 am

Assuming chemical conversions could adequately convert water and carbon dioxide into hydrocarbon fuels, the navy could already be doing this in nuclear carriers. I suspect the chemistry is the limiting issue. And, the carriers would still need large fuel tanks to handle surge operations. I suspect the processes require to much infrastructure and possibly available power to produce the fuel on an as needed basis. It might take a nuclear carrier a month to replenish it's fuel stores. Compare this with ~ 1/2 day(?) to offload fuel from a tanker. The carrier may need much more available excess power, and revolutionary fuel generating chemical processes. The article may be addressing the latter issue.
I don't know how much excess power a nuclear carrier has after meeting engine and other engineering demands.

Dan Tibbets

Skipjack · Post by **Skipjack** » Mon Nov 19, 2012 3:35 am

I don't know how much excess power a nuclear carrier has after meeting engine and other engineering demands.

Well, I guess they have a lot of excess power during those times when they are not on alert and going full speed.

Joseph Chikva · Post by **Joseph Chikva** » Mon Nov 19, 2012 5:01 am

D Tibbets wrote:I suspect the chemistry is the limiting issue.

No, the chemistry of this process is well developed.
Germans suffering during WW2 shortcoming of crude oil did motor fuel from coal.
First step there was the gasification of coal with producing of mix CO, CO2, H2 and H2O.
Then redusting.
Then absorption of so called acid gas (the mix of CO2 and SO2)
Then mix of CO and H2 with stechiometric ratio 1:2 was directed into ferric or cobalt catalytic reactor.
As result they get hydrocarbons and water.
This is so called Fischer-Tropsch process discovered IIRC in 1925.

The similar process was also developed by South African company SASOL when South Africa was under embargo and nobody sold them the crude oil.
Now SASOL is a world leader offering coal-to-liquid and gas-to-liquid technology around the world.
They state that technology is commercially attractive when oil price exceeds certain limit (80 USD per barrel IIRC).

The similar process ( CO+2H2) but with another catalyst gives also methanol – very bulk chemical product.

And for improving of stechiometric ratio till desired 1:2 the catalytic reaction CO2+H2O => CO+H2 is also used. Technology provider are many companies. E.g. Haldor Topse.

KitemanSA · Post by **KitemanSA** » Mon Nov 19, 2012 5:03 am

The hard part has always been getting the CO2. That issue disappears with ammonia.

Joseph Chikva · Post by **Joseph Chikva** » Mon Nov 19, 2012 5:22 am

KitemanSA wrote:The hard part has always been getting the CO2. That issue disappears with ammonia.

First link from google. Key words: CO2 recovery from air membrane

Liquid membranes of amine liquids with glycol compounds were used for the separation of CO2 from atmospheric air. Because the CO2 concentration in atmospheric air is only 400 ppm, CO2 separation based on a facilitated transport mechanism by an amine compound has an advantage.

ladajo · Post by **ladajo** » Mon Nov 19, 2012 11:06 am

CVN's run around at speed for flight operations. It is not a matter of alert/non alert. It is a matter of wind. Flight Operations also use steam for the catapults. EMALS will provide an interesting option in that regard.

Amine CO2 process has been used for years. It is the primary method of CO2 scrubbing in submarines. "Ain't no stink like boat stink" is a well known related quote in the boat community. Amine carries a particular odor. It is also a finite (albiet plenty) resource on board. One does not make more u/w. Something else to consider in this process is the volume of CO2 desired, as well as the mass-rate for the overall envisioned process.

I think the ammonia idea has some merit personally...

Joseph Chikva · Post by **Joseph Chikva** » Mon Nov 19, 2012 11:32 am

I only showed the first link taken from Google search as know that CO2 recovery from air should not be a big problem.
BTW ammonia has an odor too.
But there are some odorless processes as well.

I am afraid that entire facilities will be costly and very roomy. I did not read carefully, how they are going to get hydrogen? Via water electrolyze? If so, process will be quite energy intensive.

ladajo · Post by **ladajo** » Mon Nov 19, 2012 11:58 am

Submarines also generate Oxygen from water using electrolysis. The other by product...Hydrogen. But again, desired mass rate is the question.

KitemanSA · Post by **KitemanSA** » Mon Nov 19, 2012 1:44 pm

Using the Haber process, you need hydrogen gas. Using SSAS (Solid State Ammonia Synthesis - kind of a fuel cell in reverse) all you need is water and nitrogen.

SSAS is kind of at the "Haber" stage, not the "Haber-Bosch" stage, scientifically proven, but not yet industrialized. RSN they say.

KitemanSA · Post by **KitemanSA** » Mon Nov 19, 2012 1:53 pm

Joseph Chikva wrote: I am afraid that entire facilities will be costly and very roomy. I did not read carefully, how they are going to get hydrogen? Via water electrolyze? If so, process will be quite energy intensive.

That is kind of the point, nuclear reactors give intensive energy, but current designs are too massive to be useful on smaller ships (CGs, DDs, FFs, LCSs, and the like). Design a massive (i.e. roomy) ship to create the energy and convert it into a more generally useful form, e.g., an AON (or AOF). Just a thought.

Skipjack · Post by **Skipjack** » Mon Nov 19, 2012 3:00 pm

Hmm, reading up on it some more, I do have to say that ammonia has its merrits. Here is some food for thought. In an electric ship, the ammonia could be used in a fuel cell to generate electricity instead of burning it. Since it will be hard to have a 100% efficient combustion, you would always release tons of unburnt ammonia into the air, potentially poisoning people arround you. Because of that, fuel cells would probably be preferable over burning the stuff.

ladajo · Post by **ladajo** » Mon Nov 19, 2012 3:20 pm

KitemanSA wrote:
Joseph Chikva wrote: I am afraid that entire facilities will be costly and very roomy. I did not read carefully, how they are going to get hydrogen? Via water electrolyze? If so, process will be quite energy intensive.
That is kind of the point, nuclear reactors give intensive energy, but current designs are too massive to be useful on smaller ships (CGs, DDs, FFs, LCSs, and the like). Design a massive (i.e. roomy) ship to create the energy and convert it into a more generally useful form, e.g., an AON (or AOF). Just a thought.

I would argue that it is not size, but cost (and false costs at that) that has limited more prolific use of nuclear plants in surface ships. We did design the D series of plants for use in Destroyers and Frigates, not just the Cruisers they ended up in.

Submarine hulls are more constrictive than surface ships. In a ship, you can go up as well as along with the design. In a submarine, you must stay in the tube, so you can only go along the tube.

The design spin in the last years has been for core and plant life (single load for ship lifetime) vice power density.

I really do think there is some merit to hybrid plants where power used used for differing functions, vice the sole tradition of steam = shaft turns and turbine generator hums. (I guess I should also give a small hat tip to pure water production...)

There is so much more we could do with the plants, but we are stuck in the 1950's Rickover model. Imagine re-engineering with alternate core designs like we futzed around with before. Sodium, Floride, Thorium...
So much possibility. Sigh.

Joseph Chikva · Post by **Joseph Chikva** » Mon Nov 19, 2012 3:57 pm

KitemanSA wrote:That is kind of the point, nuclear reactors give intensive energy, but current designs are too massive to be useful on smaller ships (CGs, DDs, FFs, LCSs, and the like). Design a massive (i.e. roomy) ship to create the energy and convert it into a more generally useful form, e.g., an AON (or AOF). Just a thought.

I've just taken my "Applied Electrochemistry" book and can provide you the following number:
depending of type of electrolyzer cell we need 4.3-5.6 kW*h for producing of 1 m^3 hydrogen
We can recall other numbers as well:
1 m^3 hydrogen has a mass about 89.3 g
Hydrocarbons contain about 1/7 of Hydrogen by mass.
But Fischer-Tropsch process spends hydrogen for auxiliary producing of water.
I have not an input data how much surplus power have warships, you know this number better.
So, you can estimate yourself how much hydrocarbons can be produced in 1 hour, day, etc.
Also recall, that you need not only hydrogen, etc, facilities.
As I understand (correct me if I am wrong) you need produce the so called synthesis-gas (the mix of CO and H2), to direct that gas to Fischer-Tropsch reactor, then to remove water, then to distill the mix of hydrocarbons. As Fischer-Tropsch process gives the mix beginning from methane (CH4) and ending with solid paraffins. While jet fuel has boiling points from about 150 C deg to about 240 C deg.
And how we can utilize the light ends and heavy ends?