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Microchannel Device for De-Sulfuring Military-Grade Fuel

31 March 2006

The military is exploring the field use of hydrogen fuel cells to power electronic gadgets and facilitate communications, thereby avoiding use of generators that are noisy and create heat signatures. One barrier to that approach, however, is the source of the hydrogen.

The military has no current plants to add hydrogen to the strategic and tactical operations logistics burden, and therefore the challenge is the on-board reforming of the existing prevalent JP-8 military fuel to produce hydrogen. JP-8, however, can be high in sulfur—specifications allow it to contain up to 3,000 ppm. Neither catalysts used in reforming nor fuel cells are tolerant of sulfur.

Researchers at Pacific Northwest National Laboratory (PNNL) are developing a compact microchannel distillation unit to create a light fraction of JP-8. The JP-8 light fraction is then reacted in a catalytic process called hydrodesulfurization (HDS) to remove the sulfur from the fuel—similar to the approach refineries take to produce low-sulfur fuel.

Conventional technology utilizes hydrogen as the co-reactant with JP-8 to power the process, but, again, hydrogen is not available in the field. Instead, the PNNL process uses syngas generated by the steam reforming of the de-sulfurized JP-8 to drive the process.

Most of the syngas is further purified for use by the fuel cell, but a fraction of it is diverted to the hydrodesulfurization unit. The use of syngas creates some challenges, but it appears that they have been mostly overcome in the PNNL process, and syngas performs almost as well as pure hydrogen.

The HDS process is operated in the gas phase at low or moderate pressure and high space velocity, in contrast to the conventional operation in a three-phase trickle bed reactor under high pressure.

The research team was able to reduce the JP-8 sulfur content to 5ppm or less when starting with 320 ppm sulfur fuel, using several different catalysts. (Samples of JP-8 in use in Iraq in 2004 found sulfur concentrations ranging from 2,000 ppm to 200 ppm, with 67% of the sample ranging from 1,500 ppm to 500 ppm.)

David L King and Xiwen Huang form PNNL presented the work at the 231st American Chemical Society National Meeting in Atlanta.

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March 31, 2006 in Fuel Cells, Fuels, Hydrogen | Permalink | Comments (9) | TrackBack (0)

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Comments

lol finally realizing that engine noise is the key to letting the enemy know their location... maybe if they used EV's they could have been more stealth like lol?

Gee, entire US is going to ULSD at 15 ppm. Perhaps someone should tell DOD since jp-8 is pretty close to the same thing.

JP-8 is the same base fuel as commerical jet fuel.

JP-8 also has a gel point somewhere around -51 degrees F. Standard ULSD for automotive use gels around 20 degrees - totally unacceptable for use in aircraft and all-weather vehicles.

Jet engines, both commercial and civilian, require kerosine (aka JP-x). US and European refineries now have the technology for desulphurization, but perhaps not enough installed capacity to clean up jet fuel as well.

More likely, the military wanted this for the "dirty" fuel it buys locally in the Gulf of Persia. Sulphur damages turbine components.

Btw, there are plenty of turbocharged diesel aero engines in use in civilian light propeller aircraft. These usually don't fly at great altitude anyhow, and neither do the army's small, tactical UAVs. Ergo, they are not neccesarily exposed to arctic temperatures. There are, however, military diesel grades such as Special Austro DK with additive packages that push the cold filter plug point down to -35 degC. Besides, with a suitably designed system, once the engine is started, a fraction of the coolant may be circulated in a coil inside the fuel tank to keep it from clouding.

IMHO that the government push for a hydrogen economy is primarily war driven. The ability of ship based nuke power for electrolyzing seawater could shorten fuel logistics significantly.


Btw, there are plenty of turbocharged diesel aero engines in use in civilian light propeller aircraft.

Diesel aero engines are a great idea and represent a sensible path forward for GA with the evental demise of 100LL, but seriously, I wouldn't be surprised if there were less than 100 such aircraft in operation worldwide so far.

jb -

you're right, the civilian numbers are still smaller than I thought. Only several hundred light aircraft run diesel engines today, but that's up from zero less than a decade ago. Diesel is just way cheaper than avgas and does not contain lead, either, so I would expect the trend to continue.

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The reunion comes about as result of a fly on the wall documentary being made about Egg. Clare, a young twenty- something, film maker is following Egg's every move and it is she who comes up with the idea to get them all back together. Not surprisingly, Egg has a bit of a thing for Clare. Will it lead to anything...?

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