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Catalytic Carbon Extraction in Fuel Cell Production?
garyebickford asks: "I've been following the discussions in the media regarding fuel cells & hydrogen fuel. I have an idea (really a set of ideas) for handling the CO2 issues, which could make fuel cells a better solution. Perhaps someone who know about such things can tell me whether it's workable or not. Speculating wildly, if the carbon could be retained in the process (in a discharge tank, for instance), then it might even be useful as a feedstock for plastics, for example. How might a fuel cell process (both production and use), possibly multistage or incorporating a catalytic pre-process, emit carbon in non-gaseous form? What about a fuel cell that just converted ethanol or higher weight hydrocarbons to methanol, or perhaps a nitrite or another byproduct? Consumers could then recycle this waste to the fuel station at the next fill-up. Even this incomplete process can provide more energy per weight or volume than hydrogen, in theory. Would such a process be possible, or feasible?"
"Many fuels can be used in fuel cells, including hydrogen, methane/methanol, ethanol, and ammonia. One of the problems with all these, in fact any system that consumes hydrocarbons (either biomass or petroleum), is that at some point in the process the carbon is released as carbon dioxide. For H2 and NH3 the problem is in the production facility; for hydrocarbon fuels the fuel cell itself emits carbon in some form. Perhaps fuel cell research has tended to think in terms replacing the existing combustion model, with the given that output will be H2O and CO2. Is anyone studying the possibility of fuel cells that have other output chemistry?"
Build the fuel cell into a laser printer, and have it dump the carbon dust right into the toner cartridge. :)
Do it so I can plug my computer and display into it, and power them too, and I'll buy two.
I have a layman understanding of physics. This means I can read about advances in the field of physics and sometimes understand what is going on. This does not mean that I can propose new ways of looking at things in the field of physics. Why? Because every physicist has a layman's understanding of physics. Anything that you can come up with, they've already thought of it.
Thankfully this doesn't happen in computer science very often. It does happen though. I remember having a long conversation with a guy who thought he had a great idea for a replacement for floppy disks (this was pre-USB). His idea was that the monitor could read the data from a device people carry around. At first I thought I misheard him. Then I calmly explained to him that monitors are output devices, not input devices. Then he asked what the difference was. Eventually he turned red and asked how you could do it. We had a discussion about flash memory and interface standards and then he got bored and went away.
Which is typically the flow of these conversations, so excuse me for not entertaining your brilliant idea.
How we know is more important than what we know.
Combining Carbon with Oxygen or Hydrogen with Oxygen produces energy - but splitting up a chain of carbon and hydrogen to get the individual atoms to do that with requires some energy, though it's a lot less than burning the C and H will provide. Catalytic Converters on cars take the unburned hydrocarbons in the exhaust, split them and burn them before they get out the exhaust pipes, and take partially burned carbon monoxide and finish burning it. It's a waste of energy, but it was going to be wasted anyway - the reason to do this is that hydrocarbons and CO lead to air-pollution problems including smog. (They also split various nitrogen oxides to give nitrogen and oxygen; I don't know if this is exothermic or if it's using heat generated by the other reactions.)
You can't split the CO2 up into C and O2 without putting back the energy you got out of that reaction, so a catalytic converter won't help you. You could do things like combine it with calcium oxide to make calcium carbonate, and store that, but the usual way to make calcium oxide is by heating calcium carbonate to get rid of the CO2, so that's really no help.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
On of the big questions you have to ask yourself is, "What problem am I trying to solve?"
The real problems facing fuel cells-the reasons why fuel cells aren't widely used-are the cost of producing them, and the difficulties in creating fuel. You're not trying to address either of those issues. In addition, you advocate replacing hydrogen fuel cells by fuel cells based on different chemisty. Making hydrogen fuel cells cheaply is hard. Now you're adding in a different, potentially brand new chemistry - you can't just throw any old fuel into a fuel cell and expect it to work, the entire design would potentially need to be reworked, which means that your fuel cells are even more expensive.
The other question is "Why bother?" Whatever non-CO2 carbon byproduct you make, it'll yield much less energy than if you completed conversion to CO2. For what gain? High CO2 emissions aren't hurting current energy generation techniques. Due to efficiency over internal combustion, just converting to regular fuel cell will reduce the CO2 emissions at the end use point anyway.
You also ignore the regeneration of the waste. What chemistry would you use? Where would you get the energy from? If from fossil fuels, you'll still be generating CO2 - probably more than what would be generated by burning the fossil fuels directly, due to the second law of thermodynamics. If from biomass, the CO2 question is moot - the CO2 you release today is going to be reincorporated into plants tommorrow (and thus into your fuel in a week). Zero net CO2, and you don't even have to collect any waste. If the energy is from solar/wind/hydro/nuclear, you can generate H2 directly without CO2 discharge, or can create hydrocarbons/alcohol from CO2 and H2O (so you'll get no net gain in CO2 upon complete combustion).
In short, the problem you're trying to solve is not currently limiting anyone in any fashion, and even if CO2 emiting fuel cells were in popular use, your proposed techniques likely would be either superfluous or distinctly counter-productive.
Methane probably has more energy in it than gasoline. It has four high-energy hydrogen bonds while gasoline only has something like 2 per carbon, and the weight of a purely hydrogen and carbon hydrocarbon is pretty close to proportional to the number of carbons. Hydrogen gas has a LOT more energy in it than gasoline per unit mass. They used to power the Space Shuttle booster rockets with it before they switched to solid state fuels (Think plastic explosives). They might not have switched at all, except that they need oxygen to burn it with.
This is what is known to the world as Carbon Sequestration, and in fact many very important advances need to be made in this arena. So far, it seems that Germany is leading the world in this area, especially with their development of a carbon-emissions-free coal power plant (by actively capturing carbon in the process.)
While I don't see much good in utilizing hydrogen-carrying fuels over non-carbon-emission methods including hydrogen itself, since one set of methods creates Carbon Dioxide and another set creates water (I hope someone starts an electrolysis debate), you'll still get mad props and points (at least from people like me) if you can get this to work, because I don't see how it could really be problematic especially due to the numerous capture-condusive properties of carbon in its many molecular forms.
This field of research is ripe for harvest, and I'd be willing to bet there are a lot of financial backers willing to invest in working demonstrations.
--I gots 99 problems but a new machine ain't one!
AMD! Asus! Whoot! 6 years!
Alright, so I'm a molecular biologist and I work with a bunch of chemists and biochemists on alternative fules. So, I have some expertise on this, but not enough that I couldn't be understood (think it though). So, here's my understanding. First off, fule cells don't make CO2, that's their big advantage. They convert H2 and O2 into H2O. If they did (and it's possible to design one that does, if you make the hydrogen on the spot from coal, which is one way to avoid running around in a car with a pressurized H2 tank) then it would take energy to pressurize the CO2 for later reclamation. This energy would be taken off of the energy efficency of the car and likely render it less than efficiant. If it used a catylitic process to turn ethanol into ethyl aldahyde and liberated hydrogen (as is possible with enzyme aid, I'm kind of working on that problem), then it would be possible to use the spent ethylaldahyde later to regenerate ethanol for further use. There are two problems: First, this is all equilibrium chemistry. That means that you need a greater concentration of ethanol than ethyl aldahyde to make the reaction proceed forword (for the technical folks, I'm symplifying here, don't complain). That means that if you want the car to use more than half a tank of fuel and you want to seperate the byproduct for reclamition, you need some way to seperate ethyl aldehyde (or whatever) from the ethanol. How the hell do you do that? Current ways of doing this are large, expensive, and energy intensive. It could happen in the future (in theory), but we have no current means. Second, converting the byproduct (ethyl aldehyde) back into ethanol is an energy intensive process. We have no current easy and environmentally friendly means of doing this. One possible future hope (which I would like to develop and exploit in about ten years) would be to bioengineer photosynthetic bacteria to harness sunlight to convert these byproducts back into their fuel product, and then use some purification process (as yet undefined, see above) to reprocess them into stock fuel. Such bacteria does not yet exist, nor (to my knowledge) do the enzymes necessary to make it function. So, in short, yes what you propose is possible. No, it can't be done yet, nor in the next five years. I hope to see such a scheme comming along to market in possibly twenty years, at best. Even then, such a system would only be a very complex and efficient battery for storing the energy of the sun (as all renewable life and fuel is). This would limit the total energy expenditure possible to a maximum of the amount of energy poured on the earth by the sun. We are already dangerously close to using that amount of energy, in twenty years we will likely be using more and all of our various renewable energy schemes will be insufficant. We have only two options, conservation or fusion power (or malthusian disaster, but no one likes that one). I leave it to the rest of you to choose which.
Let's making diamonds!
I have an idea where we take the CO2 from the air and convert it to sugars and other chemicals needed to sustain the reaction in reactor that I call a Photosensitive Living And Natural Thing (PLANT, for short). The PLANT device catalyzes the carbon into long chains made up of broken down water molecules, so you have chemicals made with H, O and C. Let's call those "hydrocarbons". Then, we extract them, mix them with some other PLANT-derived chemicals (say something like C2H5OH), and end up with an energy-dense liquid. This liquid can then be placed in tanks, pipelines, or directly into some (wise) consumer's vehicles.
We will call this miracle chemical "Bio-Diesel".
45-50 mpg in the VW TDI, and my exhaust smells like french fries, baby!
I want to delete my account but Slashdot doesn't allow it.