Direct Thermochemical Hydrogen via Nuclear Energy; the Sulfur Iodine Cycle

Those who are familiar with my comments here and at SmirkingChimp will know that I am a skeptic on the so called "hydrogen economy," at least under conditions in which hydrogen is proposed as a common fuel for automobiles and the like.

Leaving aside the safety and transport issues, one of my objections has always been - despite what the Bushies and others tell you - is that hydrogen is NOT a form of energy: It is an energy storage system. It requires energy to make it. Further, most of the conversions proposed to make hydrogen from other forms of energy are highly inefficient: For instance, to make hydrogen by electrolysis of salt solutions one can usually recover only about 10% of the energy. Electrolysis also requires the disposal of the chlorine side product and, at least until recently, the use of liquid metal mercury electrodes that cause huge contamination problems. The preferred and (and more efficient) way of making hydrogen is the water gas reaction, which of course consumes natural gas, a non renewable, greenhouse gas forming fuel.

Here though, is a process that goes a long way to eliminating some of the inefficiency concerns: A rather clever thermochemical process that splits water into hydrogen and oxygen via a cyclic process. The primary source of the energy for this conversion is nuclear energy, one of the cleanest options available to those of us who live in early in the 21st century. Such processes, cyclic processes, are very important in nature: Just one such example is the famous citric acid (Kreb's) cycle by which living things oxidize sugars to CO2 and water.

I still don't think that hydrogen is a desirable primary fuel. However it is an intermediate that can be used to make primary fuels. Readily available cheap hydrogen theoretically could be used to hydrogenate atmospheric CO2 to motor fuels, making such fuel use part of a "carbon cycle." It would beat the pants out of attacking foreign countries, killing their children, and stealing their oil.

Anyway, here's the link:
http://web.gat.com/hydrogen/images/pdf%20files/brown_si_cycle.pdf

Enjoy.

I agree with you, but wouldn't it be more correct to say it requires energy to free it? Not a huge deal, but you are not actually "making Hydrogen" unless you have a process to fission Helium or another element. Sorry that I'm in a nit-picky mood, but something is forcing me to type this...

I'm a chemist, so I believe that chemical transformations are in fact "making" things, although most chemical transformations do not involve changes in the overall mass of systems. I think for instance that one "makes" steel, though actually one is only reducing iron sulfide and alloying it with carbon and other elements.

I did post some "making" comments more to your taste over on the supernova thread.

Good one though. ;-)

ation bear the merits it assumes, or not? If so, it seems like the perfect way to deal with both waste and petroleum shortages.

I don't know where it sits right now on the economic spectrum, but yes, we will need that carbon back.

Good ta' see ya. The connect time on the ol'SC was driving me away.

Well there were a lot of things at Smirking Chimp driving me away. I'm kind of hiding out these days in this Environmental Forum.

I get into lots of trouble elsewhere.

The pdf link NNadir posted is big...

The iodine-sulfur process combines iodine with SO₂ and water to produce hydrogen iodide. This reaction is exothermic, occurring at low temperature (120°C):

I₂ + SO₂ + 2H₂O ==> 2HI + H₂SO₄

HI then dissociates to hydrogen and iodine at about 350°C, endothermically:

2HI ==> H₂ + I₂

Then, at about 800-1000°C you recycle:

H₂SO₄ ==> H₂O + SO₂ + 1/2O₂

The heat might come from your nuclear reactor.

This process can deliver hydrogen at high pressure, which is very useful for making synthetic fuels or feedstocks.

That's the easy part. The hard part is making sure you don't hire any clowns like George W. Bush or Homer Simpson to run the place.

Of course there is no real Homer Simpson.

I wish I could say there was no real George W. Bush but there is. Worse is the fact that he is indeed "running" a nuclear facility, a facility of the worst sort, weapons. That facility of course is the United States government.

It's nice to see someone offering potential partial solutions other than the usual "build solar cells all over the west" dogma I get. I'll print this and have a nice chat with one of my favorite professors over lunch- it'll cheer him up. Thanks!

I'm a non-dogma environmentalist, although lately I've been spending much of my time beating down those nasty DRE voting machines made by Diebold and others.

I do have some concerns about this sulfur-iodine process. It's a little difficult for me to see how it can be made foolproof.

Murphy's law and the Peter Principle say that some guy like Homer Simpson will eventually be supervising the stage in the process where the very hot helium stream from the pebble bed nuclear reactor is used to decompose what is essentially smoking burning pure and very angry sulfuric acid.

You'd want to be far, far away when that idiot smacks his head and says "Doh!"

So, the first question is, what are we going to use this hydrogen for? Are we going to use it to fix nitrogen for our crops? Maybe it would be more cost effective to rotate our crops and recycle our wastes in such a way that we don't need synthetic nitrogen fertilizers.

Are we going to use this hydrogen to make fuels? Maybe it would be better to work close to home rather than commute.

One thing I do know is that oil and natural gas are finite. At some point, maybe very soon, an energy economy based upon oil and natural gas will fail.

I hope that you will not mind AZcat if I address some the issues raised here.

If you are looking for a system of energy production that is "fool" proof, I cannot help you. There has never been a form of energy used on earth by human beings that meets this criteria. Given the millions of persons who die each year in the world from the environmental, health, safety, and social costs of fossil fuel use, it is certain that the status quo is far from the risk optimized solution to technological energy use.

I would have to agree that conservation is an important tool in minimizing the risk portions of energy use. No responsible person claiming an environmentalist bent would argue otherwise. Still it goes without saying that there will be a requirement for industrial scale energy for the forseeable future. The question is, what are the best options?

Hydrogen in an oxidizing atmosphere, such as we have on earth, is a useful energy intermediate. It is important even today in both the energy and the agricultural fields.

The potential application to hydrogen to the production of (clean) motor fuels involves hydrogenation either of carbon monoxide, carbon dioxide (to make small clean burning hydrocarbons or ethers) or ammonia (which has a fuel value). It is also conceivable to use hydrogen as a peak load storage medium for energy use in fuel cells, not only in cars, but in homes and businesses where cogeneration opportunities would increase efficiencies.

While I do not believe it would be wise to use hydrogen directly as a fuel, the importance and application of hydrogen as a local intermediate make its cheap production very attractive on environmental and economic grounds. There are too many applications to list here, or even in a reasonably small monograph.

Returning to the fool Homer Simpson, no I cannot guarantee that such a person might not cause a disaster of some sort in an energy production scheme. This however is hardly unique to nuclear power. A complete idiot is running our current energy scheme, fossil fuel myopia, and dead bodies are distributed widely in Iraq as a result.

Now, I happen to think that "The Simpsons" is a worthless show. I don't watch it. I know about it only through osmosis. I would hardly suspect though that a cartoon sitcom lampooning nuclear energy on Fox Television has any bearing on the wisdom of using nuclear energy. The show, I'm sure, has no bearing on the actual state of professionalism, training, engineering, or technical expertise of those who really DO work with nuclear energy. The fact is that 30% of the electrical energy in the United States has been generated in the last 3 decades without a single demonstrable loss of life in the United States. In France, the figure is 90%. Therefore, however fearsome Homer Simpson may seem, he is at best a cartoon reflection of our irrational fears, fears that reflect our cultural ignorance and not the realities of our physical situation.

As for the specifics: I have a huge respect for the state of modern day materials science, a science that was relatively poorly developed in the era during which the last nuclear reactors in this country were built. I really have no problem with the hot decomposition of sulfuric acid. It is probably (though I don't know this) a process already in use in another application. General Atomics has apparently already piloted the process, and I am sure that the engineers there have a pretty sophisticated understanding of the reactor parameters. I note that this reaction in any case will not be taking place in a nuclear portion of the reactor, irrespective of the type of reactor that is used. (General Atomics pushes HTGCR's because that's what they're famous for making; other high temperature reactors might be better for the sulfur iodine process. Other reactors may be equally suitable or even better.) Thus an accident in this part of the reactor - although it will be beat to death by the media that ignores gas, oil and coal accidents - will be limited in its impact.

Hydrogen powered cars are worse than what we have now if the hydrogen is made using coal. Some sort of methanol powered hybrid like the Prius would be better.

And yes, I agree with you NNadir, using nuclear energy to make hydrogen is better than fighting wars over gas and oil.

But I do think that too many people are looking for "magic wands" these days. They think they can simply sign a check for some new technology and it will make their problems go away.

It's not that easy. This point has been especially hammered home to me as I investigate the electronic voting machine industry.

Before we can expect any of these high technologies to save us we've got to get rid of the Enron style corruption, and the NASA style complacency.

That's a political problem, not a technological problem.

You wrote: "...But I do think that too many people are looking for "magic wands" these days. They think they can simply sign a check for some new technology and it will make their problems go away..."

Neither do I believe in magic wands, my least favorite being those that refer rather blithely to the "hydrogen economy."

That said, there are many technological solutions that have merit and I think that this Sulfur Iodine procedure is one worth careful consideration. Note that the authors of the link I provided in the intial post reviewed 800 references to thermal water splitting schemes and selected only two.

Obviously such a scheme would require significant investment and time. As we all know, the devils are in the details. Yet every major industrial system went through a procedure of being merely an idea, and then a pilot project, and finally an industrial project. There is no magic here, only the need for hard work and vision, and the acceptance of financial and other risks. Nevertheless such an investment beats spending inordinate sums on killing people to steal their oil by a long shot.

But we really have no choice. As you say, the fossil fuel-based economy is finite and while nobody really knows how much is left, we better start addressing these concerns now, because there is no "magic fix" for the problem.