[Bioconversion] Fireball Express!

[Jeff Davis]

On Saturday 28 October 2006 05:53 pm, AJH wrote:
> >Can we use this method to fuel a stove?
>
> I cannot see how, it takes a metal that has been refined using a high
> grade energy source and burns it to produce far higher temperatures
> than a stove can use.

Maybe a small amount in a retained heat stove or is this stuff poisonous?


Geoff wrote,
> Interesting how that is similiar to the glowing char removing the extra 
oxygen from CO2 in a
> gasifier, I wonder if there are other such reactions out there just waiting 
to be remembered.
> Cheers,
> Geoff.

We have to keep our eyes open ALL THE TIME!

See article below:

Jeff



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http://www.mng.org.uk/green_house/renewable_energy/metal_NS_article.htm

If smog-choked streets test our love for petrol and diesel engines, then 
rocketing fuel prices and global warming could end that relationship once and 
for all. But before you start saving for the fuel-cell-powered electric car 
that industry experts keep promising, there's something you should know. The 
car of the future will run on metal.

So reckons Dave Beach, a researcher at Oak Ridge National Laboratory in 
Tennessee, who has come up with a plan to transform the way we fuel our 
engines. Chunks of metal such as iron, aluminium or boron are the thing, he 
believes. Turn them into powder with grains just nanometres across and the 
stuff becomes highly reactive. Ignite it, and it releases copious quantities 
of energy. With a modified engine and a tankful of metal, Beach calculates 
that an average saloon car could travel three times as far as the equivalent 
petrol-powered vehicle. Better still, because of the way that this metal 
nano-fuel burns, it is almost completely non-polluting. That means no carbon 
dioxide, no dust, no soot and no nitrogen oxides. What's more, this fuel is 
fully rechargeable: treat your spent nanoparticles with a little hydrogen and 
the stuff can be burnt again and again. It could spell the start of a new 
iron age, and not just for cars. All kinds of engines, from domestic heating 
units to the turbines in power stations, could be adapted to burn metal.

Topping up your tank with what are essentially iron filings might sound 
bizarre, but vehicles can run on all sorts of materials, from methane to coal 
dust or gunpowder. So why not metal too? After all, burning a heap of 
powdered iron releases almost twice as much energy as the same volume of 
petrol. And replacing iron with boron gives you five times as much (see 
Graph).

Rockets already use metal powder as fuel. A dash of aluminium gives extra 
oomph to the space shuttle's solid rocket boosters, for instance, and metal 
powder is used in rocket-powered torpedoes.

However, putting metal inside a rocket engine is a very different proposition 
from using it in a car engine. When granules of metals such as iron and 
aluminium come into contact with air, they become coated with a layer of 
oxide that must be removed before the metal can ignite. To kick off 
combustion in most metals, you need a heat source with a temperature of at 
least 2000 °C, which is high enough to vaporise the oxide layer and expose 
the bare, reactive metal beneath. That might be fine for a rocket, but it's 
not so simple for a car engine. Another problem is that once the vaporised 
metal oxide starts to cool, it solidifies and forms ash. While high 
temperatures and clouds of ash present no problems in a one-shot rocket, they 
create a serious mess for anyone trying to burn metal powder in an internal 
combustion engine.

Solomon Labinov, also a researcher at Oak Ridge, is all too familiar with this 
problem. In the early 1980s, while he was the director of an engineering 
institute in Kiev, Ukraine, he and his team tried burning micrometre-sized 
iron particles in an internal combustion engine. They modified the engine to 
work at high temperatures, but found that the oxide ash deposited on the 
pistons, cylinder walls and valves, clogging up the engine. They couldn't 
find a way round the problem and gave up.

Labinov subsequently moved to the US, and went to work at Oak Ridge. In 2003 
he suggested to Beach and theorist Bobby Sumpter that they take a fresh look 
at the problem, this time using nanoscale particles.

In experiments they found that iron nanoparticles measuring about 50 
nanometres across ignited far more easily than the larger granules of iron 
that Labinov had worked with: heating them to around 250 °C, or even just a 
spark, could do the job. And the more the researchers looked, the more they 
realised that the nanoparticles behaved in a very different way to their less 
finely divided cousins.

Nanoparticles burn much more easily because their surface area to volume ratio 
is huge. Iron reacts very readily with oxygen, so if a lot of it is exposed 
to air at the same time, oxidation can generate enough heat to ignite the 
metal spontaneously. To prevent this, nanoparticles are usually given a 
protective oxide coating during manufacturing. But even with an oxide layer, 
the huge surface area of these nanoparticles means that with just a little 
heat, it is easy for oxygen molecules to diffuse through and trigger 
combustion.

One consequence of this is that once the nanoparticles are ignited by a spark, 
say, they burn rapidly and the combustion temperature peaks at around 800 °C 
- hot enough to do useful work but not so high as to melt an alloy engine. 
And crucially, unlike the micrometre-sized particles, nanoparticles don't 
burn hot enough to vaporise or even melt. They just oxidise, leaving a heap 
of oxide nanoparticles. And that means no sticking to the walls of the 
cylinder, and no clogged engine.

The tidy heap of iron oxide left over from the combustion process gave Beach 
an idea: he realised that it would be easy to convert the iron oxide back 
into usable fuel. He heated the burnt fuel to 425 °C in a flow of hydrogen. 
The iron oxide particles were reduced to iron, and the hydrogen combined with 
oxygen to form water. Now the fuel was ready to burn again.

There was one more problem to solve if the particles were to have any real 
potential as fuel. Individually, nanoparticles burn in a flash, releasing all 
their heat in a millisecond or so. But to make the metal fuel useful in a 
wide range of engines, the rate of heat production should not be so fast that 
an engine cannot deal efficiently with the heat produced. In internal 
combustion engines, for example, each burst of combustion can last anywhere 
between 5 and 20 milliseconds. If heat is released any faster, the fuel is 
used below its maximum efficiency.

So the team attempted to limit how quickly their fuel burnt by pressing the 
nanoparticles into larger clusters. The idea was to limit both how fast 
oxygen could diffuse into the nanoparticles and how fast heat could flow out 
of them, so reducing the rate of heat release.

The plan worked. Beach and his colleagues found they could create nanoparticle 
clusters weighing anything from 1 to 200 milligrams each, and by adjusting 
their size, shape and density they could control the burn rate. While single 
particles would burn in just milliseconds, the largest clusters could take 
from 500 milliseconds to two seconds.

With the first stage of the research complete, the team now plans to design an 
engine that can run on the fuel. It would be relatively easy, Beach believes, 
to convert external combustion engines such as the gas turbines that power 
jet aircraft and vehicles such as tanks, or even those used to generate 
electricity in power stations. These engines might operate on metal fuel 
without too much difficulty, he suspects, though they would certainly need 
modifications to the fuel-delivery systems, and he would need to find a way 
to collect the spent fuel.

Another option is to use the fuel to power a Stirling engine, an efficient 
external combustion engine in which a fluid or gas in a cylinder is 
alternately cooled and heated to move a piston (New Scientist, 11 December 
1999, p 30). Stirling engines are used in domestic combined heat and power 
units, for example, and for cooling satellites.

When it comes to cars, a Stirling engine is a possibility: NASA and a number 
of car manufacturers, including Ford, have already experimented with Stirling 
engines designed to power vehicles. But Beach also hopes it will be possible 
to use his metal fuel in an internal combustion engine. A modified diesel 
engine might be able to burn nanoparticle powder as a fuel, just as a 
conventional diesel engine uses a mist of diesel fuel (see Diagram).

Beach suggests that metal powder or clusters could be injected into the engine 
cylinders from a storage tank, possibly using a jet of air, which could also 
supply the oxygen for combustion. A spark plug would trigger ignition and 
burnt fuel would be carried from the cylinder by the exhaust gases.

Beach's team must also find a way to collect that spent fuel. One possibility 
is to store it in the fuel canister, with a movable membrane dividing the 
canister into two sections, one for fresh and one for spent fuel. The burnt 
fuel might be collected using a filter or, since iron oxide powder is 
ferromagnetic, an electromagnet. When a driver needed a top-up, the entire 
canister could be unclipped and exchanged for a fresh one at a filling 
station, and the used fuel would then be recharged.
“Scrapyards full of old cars could become fuel for the vehicles of tomorrow”

The result would be an engine similar to a conventional one, but which emits 
no carbon dioxide, harmful particulates or even nitrogen oxides. These 
compounds usually form in combustion at high temperatures, but Beach has 
shown that he can lower temperatures to about 525 °C by varying the size of 
the clusters. However, plenty of work is still needed to strike the right 
balance between temperature, speed of combustion and engine efficiency.

A vehicle running on metal fuel should please both drivers and environmental 
campaigners. Beach calculates that a fuel tank holding 33 litres of his iron 
fuel will power a car engine for the same distance as a 50-litre tank of 
conventional petrol or diesel.
Heavy load

There are still major drawbacks, however, the most significant of which is 
weight, according to Nathan Glasgow, a consultant at the Rocky Mountain 
Institute, a think tank in Snowmass, Colorado. Although iron is a compact 
fuel compared to hydrogen, it is also extremely heavy, and even though its 
high energy content allows you to almost halve the size of a typical 50-litre 
fuel tank and still get the same energy out, a tank of fuel would weigh about 
100 kilograms - more than twice as heavy as the petrol it replaces. And 
because the spent fuel is kept on board, unlike the polluting by-products of 
conventional fuel, this weight won't decrease as you drive - you must always 
lug the full load around. The weight of fuel will also add to the cost of 
shipping it back and forth to recycling facilities.

David Keith, a physicist at the University of Calgary in Alberta, Canada, is 
satisfied that the technology itself is sound, but believes there are 
fundamental difficulties with iron as a fuel. Even if everything works 
perfectly, he says, the fuel is simply too heavy to be really useful.

So for the ultimate in clean, green driving, perhaps hydrogen really is the 
answer. After all, it packs over 12 times as much energy per kilogram as 
iron.

Beach is unconvinced. Of course hydrogen is important, he says, but you don't 
want to be filling your tank with it. "What we're saying is that metal fuel 
is a more convenient, safer, and more practical energy carrier than 
hydrogen." And it's true that engineers are still struggling to find ways to 
store hydrogen at densities high enough to make it a practical alternative to 
petrol. In contrast, metal fuel is stable at room temperature, so it is easy 
to store and transport. "We've got a solid at ambient pressure. So moving it 
around on freight cars or storing it for long periods of time isn't a 
problem," says Beach.

Besides, there's a potentially more serious problem with hydrogen-powered 
vehicles that the use of metal would sidestep. The water produced by hydrogen 
fuel cells is usually just allowed to escape into the atmosphere. Some 
climate scientists are concerned that the huge amounts of water vapour 
released by millions of hydrogen-powered cars and trucks would accelerate 
global warming.

Recycling metal oxide fuel with hydrogen also produces water vapour, but it 
would be generated at large recycling units rather than by vehicles out on 
the road. This means that it would be simple to collect the water and recycle 
it - perhaps even using electrolysis to convert it back into hydrogen.

It might even be possible to dispense with hydrogen altogether. If carbon 
sequestration becomes viable, carbon monoxide could be used to recycle spent 
metal fuel, creating carbon dioxide. Carbon monoxide is a common by-product 
of coal gasification - one of the technologies likely to become more 
important as the coal industry attempts to reduce its contribution to global 
warming. Use this carbon monoxide directly for recycling fuel and the 
industry would get more useful energy out of its coal than before.

Beach has even got some solutions to the weight issue. Use aluminium 
nanoparticles rather than iron, for example, and you get about four times as 
much energy per kilogram. With boron you'd get almost six times as much. Of 
course, since these metals cost more than iron, the fuel would be more 
expensive in the first place. Aluminium, for instance, costs about 15 times 
as much as iron.

Clearly it is very early days for metal power. The Oak Ridge researchers are 
still applying for grants to build a prototype engine, and Beach has yet to 
carry out a full analysis to find out whether his fuel could be 
cost-effective. The team also plans a series of experiments to optimise the 
size of its nanoparticles, as well as to investigate the best way to package, 
inject and collect the stuff in a real engine. And even if their work 
succeeds, who is going to buy the first metal-powered car when there's 
nowhere to fuel it, and who is going to build a network of fuel stations 
until there are cars to fill?

At the very least, metal-burning engines are another entry in the list of 
alternatives to oil. And whatever happens, Beach's remarkable idea does raise 
one interesting possibility. In the past, energy magnates have earned 
billions from coal, oil and gas fields. In the future, they could grow rich 
from scrapyards full of yesterday's cars, by transforming them into fuel for 
the vehicles of tomorrow.
Kurt Kleiner is a science writer based in Toronto.
-- 
Jeff Davis
Somewhere 20 miles south of Lake Erie, USA
http://www.velocity.net/~jeff0124