Clean Coal? Uh.. no
May 19th, 2008
|
| Share |
Clean coal. Clean dirt. Clean filth. Clean smut. These are all phrases which really don’t make a lot of sense. Coal is inherantly pretty dirty stuff. It’s mostly carbon, which means when it burns it generates mostly carbon dioxide. There’s nothing you can do about this, because that’s simply what it is. At best, you can try to grab that carbon dioxide and stuff it somewhere, but when you consider that burning one ton of coal generates three tons of CO2, you’ll realize pretty fast that there aren’t that many places to stick it, especially considering the enormous energy needed to capture, compress and sequester the stuff.
While coal is mostly carbon, it does have traces of other stuff in it. It has lead, mercury, uranium, thorium, thallium and just about every other mineral you can think of mixed in. One reason for this is that carbon, which is basically what coal is, does a pretty good job of filtering out big heavy molecules and metals. This is why “activated carbon” filters are used to clean water and air. But over eons of filtering ground water, coal tends to build up a lot of nasty stuff. Coal also contains a fair amount of sulfur, which leads to sulfur dioxide and acid rain. This combined with other volatile organics, nitrous emissions, soot and fly ash makes for a very nasty brew of toxic material.
This “nasty stuff” is actually a relatively small portion of the coal by mass or volume. However, when you burn tens of thousands of tons of it at a single location in a single day, well that <1% of mercury, lead, thallium, arsenic and other stuff tends to add up pretty fast. So what happens to this stuff? Well, in a traditional coal power plant, it gets blown out the stack with everything else. In so-called “clean-coal” plants the CO2 is vented directly into the atmosphere like any other plant, but the flu gas receives some treatment. It may simply have the sulfur reduced, and no treatment for the mercury or other emissions and still be called “clean coal.” In less filthy plants the coal may be washed down of most of the contaminants and then the gas filtered. This reduces (but does not eliminate) much of the contaminants. “Gasification” can reduce it even more.
But there are two prices to this: First the systems are very energy intensive and thus a “clean coal” power plant can actually burn more coal and produce more CO2 than the non-”clean” coal plants to produce the same amount of energy. Another problem is that the filth doesn’t go away. Sure, you may remove 90% from the stack (which is about 10% too little) but that fly ash, sulfur, heavy metals and so on has to go somewhere. Normally this is into places like “slurry dams” or just into big piles which may or may not even be isolated from ground water.
The sheer volume of this stuff is enormous, making treatment or disposal like other chemical waste nearly impossible.
Here’s some propaganda. Thanks to Physical Insights for finding this. “Moist air” indeed..
This entry was posted on Monday, May 19th, 2008 at 1:27 pm and is filed under Bad Science, Enviornment, Good Science, Not Even Wrong, Obfuscation. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
View blog reactions
May 19th, 2008 at 1:41 pm
You’re right about the sheer amount of coal used being the problem. It is just so enormous that I don’t think there’s any way you could hope to treat that much material the way you’d really want to.
Quote Comment
May 19th, 2008 at 1:44 pm
Coal can be clean, as long as you don’t burn it. Nor react it with steam.
Regarding CO2, perhaps the least dirty of the products if those bizarre practices are carried out, you say, “there aren’t that many places to stick it, especially considering the enormous energy needed to capture, compress and sequester the stuff”. What if the energy needed to capture, compress, and store it were available in gigantically enormous amounts from a substance that has energy for this, but not, essentially, for any other purpose?
And what if the result of this stuff’s going to work on atmospheric CO2 were that it turned into inert rock that could lie in a thin layer whose thickness, for all the hundreds of gigatonnes of legacy CO2 that we now have to deal with, would amount to centimetres on the world’s desert regions, or maybe 1 mm on the whole planet?
Should that turn out to be true, it would probably follow that other proposed CO2 remediation methods were boondoggles. More here; note particularly the comment from schuiling, Roelof Dirk near the end of the comment string.
Quote Comment
May 19th, 2008 at 2:08 pm
Dr. Schuiling’s ideas on the use of natural geochemical processes to solve environmental problems are interesting, but at there current stage are more at the conceptual phase than the practical. He has had to make too many assumptions and at any rate hasn’t really factored in the growth in China’s coal usage.
The whole point is coal is not necessary as a source of energy, so why invest in ‘clean coal’ technologies to begin with? With the FutureGen projects basically in the toilet, it would seem that clean coal is going to be like hot fusion, forever ‘just around the corner’
Quote Comment
May 19th, 2008 at 2:26 pm
Is carbon capture and sequestration really that unrealistic? I hear about it all the time that the new power plants are going to be required to keep their carbon and contain it instead of release it. It sounds like it is doable because all the information i’ve seen shows there is being a big investment in it anyway so what is so hard about it?
I know there is a lot of carbon but what about old coal mines and gas wells and that kind of thing? Don’t we have enough to ship it to those and put it underground or even in the deep ocean?
Quote Comment
May 19th, 2008 at 2:34 pm
Adam said:
It’s the energy costs of doing it that will kill you even if there was a practical way to capture the carbon dioxide in bulk. Any chemical process involves a transfer of energy, in this case energy must be put in, and that doesn’t come for nothing.
Nor, despite breathless pres-releases to the contrary. has anyone yet come up with a economical process for doing this in bulk.
Quote Comment
May 19th, 2008 at 2:47 pm
If that were the only way to do it, it would indeed be unrealistic. Consider a plant that in its history has made 100 million MWh. If its CO2 were turned into magnesite, it would, I guess, be substantially more voluminous than the original coal, and the original coal would have been enough to make a conical pile 200 m high, 680 m across the base. The petrified CO2 pile would I guess be a 1,000-foot artificial mountain.
Many plants are already dispersing mountains’ worth of the stuff into the air. It turns out to be possible to grind up other mountains and puff them out into the atmosphere, after the CO2, and drop it down in a thin layer over much or all of the Earth’s surface, as permanent rock dust.
Quote Comment
May 19th, 2008 at 2:55 pm
There are a couple of ways to do it. One way is to try to gather the CO2 and compress it. This has been done partially for natural gas burning facilities, but it uses a lot of energy and it is only doable when there is some kind of market for the Co2. Even then, it is less than 50% captured and it costs a lot in terms of effort and energy to capture and pipe it. Also, the gas needs to be burned in special oxygen enriched chambers and then the exhaust has to be dried of water and any residual oxygen removed. It is not easy.
The other way, which is easier to pull off is to react the CO2 with something that will bind it. Lithium hydroxide, for example, can soak up and lot of CO2. These have the problem that such chemicals don’t exist in nature and need energy to produce. They also may produce CO2 in the refining process. There are regenerative scrubbers that can soak up CO2 and then release it when they are heated or otherwise regenerated. These are used on submarines or space stations. It is an energy intensive process as well.
If you could do it with coal, I’d bet you a good 50% of the energy would need to be used to run the systems to capture the CO2, even if you had the best engineered systems around. Then there is that damn question of where you can put it. If you want to transform it to a stable form that will need energy as well. Given enough energy you could take it all the way back to carbon like you started with, but what would be the point of that? You’d expend a lot more energy going full circle!
Quote Comment
May 19th, 2008 at 3:07 pm
Yes they do.
Not too much. It’s looking like, out of the 400 kJ we had long ago from a mole of CO2 production, we will need to give back 40 kJ to comminute olivine and 10 kJ to strew it.
Quote Comment
May 19th, 2008 at 3:18 pm
G.R.L. Cowan, hydrogen-to-boron convert said:
This is fantasy land Cowan, and based on questionable foundations, and like the boron economy you’ve been flogging for years, means a vast overhaul in infrastructure. So what hat it works on paper? We have easer ways of reducing the greenhouse gas emissions from power generation with proven technology, why would we go with this untried scheme.
At any rate CO2 is just part of the problems with coal; fouling up land, destroying water supplies, and killing people are at unacceptable limits from mining the damned stuff, never mind burning it.
Quote Comment
May 19th, 2008 at 3:23 pm
Okay, well there are chemicals in nature which can soak up CO2, for example one of the most primitive scrubber systems is just water with limestone dust in it. The ones we use these days which have a high density of CO2 absorption are ones like lithium hydroxide. That is what you find in rebreathers and submarines and space suits. Those need to be refined and manufactured.
Quote Comment
May 19th, 2008 at 4:14 pm
Bottom line is the total lifetime releases of CO2 from electricity generating technologies works out to:
Coal – 990 kg CO2/MWeh
Natural Gas – 653 kg CO2/MWeh
Solar PV – 79 kg CO2/MWeh
Wind – 37 kg CO2/MWeh
Nuclear – 21 kg CO2/MWeh
Hydro – 18 kg CO2/MWeh
Total life cycle emissions accounted for.
*source: Central Research Institute of Electric Power Industry, Japan, Annual Research Report
Even with the best CO2 capture at the flue nuclear is going to beat coal hands down. We could then apply Schuiling’s ideas to deal with the rest of the CO2 burden from other processes. like steel-making.
Quote Comment
May 19th, 2008 at 5:52 pm
There is already a cheap, readily available system for converting CO2 into solid form which can be completly powered with solar energy.
Quote Comment
May 19th, 2008 at 6:24 pm
Cheap, readily available, and ineffective.
Oh, but no-one ever thought of planting plants before. Tiresome.
Quote Comment
May 19th, 2008 at 7:57 pm
Chuck said:
Yes, but a lot of realestate is needed. Also, one must be careful or the plants will only release it again when they decay. Trees work okay, because they have a long enough lifetime that they can make a difference. Stuff like grass often ends up just returning it to the atmosphere. Plankton is good, if it ends up sinking and not decaying.
Quote Comment
May 19th, 2008 at 8:08 pm
I think that the attempt to sequester CO2 is an exercise in futility in the long run. In order to separate CO2, which at best is 10% of the stack constituents you have to either increase the draft or raise the stack temperature, both of which lower the combustion efficiency. In any case you would have to drastically lower the over all efficiency of the plant, which means more cola burned per watt. Which carries back to the mine, the barge or the railroad which have to transport the coal as well as the energy costs of the additional equipment required to separate the CO2 and the tons of absorbent needed to actually absorb the CO2 and the energy required to move the stuff around and finding a dump site.
Considering what happened last year where much of the North had snow in places where it had never snowed before, all this effort seems to me to be rather pointless. In spite of James Hansen’s ravings global warming doesn’t seem to be the catastrophe that the Greens assumed it would be. I don’t like coal fired plants for a variety of reasons, but CO2 is the least of their problems.
Quote Comment
May 19th, 2008 at 8:19 pm
I agree. Another thing I’ve said before is that having a zero CO2 society is both unnecessary and unrealistic. If we cut emissions by 75% we’d be in great shape. We don’t need to nit pick every barbecue, every bonfire, every aircraft, every rocket launch, every classic car show and so on. If the big sources can be cut enough then it will be more than sufficient to keep things reasonably stable.
And lets not forget that many (most) of the big CO2 sources are also sources of all kinds of other nasty stuff!
Quote Comment
May 20th, 2008 at 12:30 am
drbuzz0 said:
That’s why we need to clear cut lots of forests! Then we can make sure the wood doesn’t decay by building log cabins with the logs. Or a big wooden wall on our border with Mexico. Wooden roller coasters could also use lots of the wood!
(Just being a bit sarcastic. But I do wonder, wouldn’t logging (and replanting) actually result in a net decrease in CO2, assuming the logs are used for construction or something? It seems many assume logging results in all the CO2 in the trees being released, but isn’t the opposite the case?)
Quote Comment
May 20th, 2008 at 12:40 am
Andrew said:
First only some of the tree is used, second much of the cut wood goes for pulp and much of that is not recycled.
Quote Comment
May 20th, 2008 at 12:48 am
DV82XL said:
So the best thing to do would be to log it and then just sink the logs in cold lakes? We ought to log big areas of Canada, replant, and sink the logs in the lakes.
http://www.forest-reflections.com/history.htm
That would serve as a carbon sink for at least a few hundred years.
Quote Comment
May 20th, 2008 at 12:55 am
Andrew said:
Too little, to make a difference.
Quote Comment
May 20th, 2008 at 1:46 am
I KNOW! We need to collect as much of the CO2 as we can, then dump it ALL ON THE MOON, and then…
…wait, nevermind.
Quote Comment
May 20th, 2008 at 2:47 pm
Considering the U.S. has a 200+ year supply of coal in the ground which is relatively cheap and easy to get out and to the power plants, I doubt we’ll see coal-fired plants vanish in the near future. Yeah, they’re not the cleanest but they’re there, and they work.
The infrastructure cost to replace all fossil power plants would be huge to the point its beyond comprehension. Coal and natural gas account for about 70% of U.S. electric production. Nuclear with its 104 reactors makes up about 20%. To replace fossil fuels with nuclear (the most energy-dense source) would require ~350 more reactors. Increase that number by orders of magnitude if you want to go with the ‘green alternatives’ of wind or solar since they’re significantly more diffuse than nuclear and about a third as reliable.
The short of it is we need all the energy sources we can get. Coal’s not going anywhere. Nuclear’s here to stay. Natural Gas comes and goes due to its price volatility but will be around for those peak demand high price markets. Solar and Wind have their limited applications but for the most part are feel good eco-Band-Aids that fall short of supplying even a fraction of the nation’s energy needs despite the environmentalists’ claims to be the wave of the future and our salvation from fossil fuels (something I’ve heard about as long as I’ve been alive and still waiting for it to come true…). Might sound a little preachy, but that’s how I see the facts, not how I wish them to be.
Quote Comment
May 20th, 2008 at 3:51 pm
Tsakanga said:
While there is a certain amount of truth in what you say, I don’t think that it is as cut and dried as that.
Certainly, none of the ‘renewable™’ solutions stand a chance of making a difference, and gas will have to serve in peaking into the foreseeable future, the replacement of coal is quite possible, if some reasonable changes are made.
First and foremost, a streamlined approval and licensing process must be put in place. The industry has matured beyond its beginnings sixty years ago, and much of what were unknowns at the time have been addressed, and most if not all of the safety protocols have been field proven. Along with this there are millions of reactor-hours of operational experience behind us. It’s time to turn the page.
Second, a standard, modular design must be selected such that each new powerplant doesn’t have to be engineered from the bottom up, and economies of scale and centralized production of components can be realized.
Thirdly, funding rules have to change such that a project doesn’t have to start servicing loans until it starts to produce power. Much of the massive cost overruns that the industry has suffered has been in interest as delays, mostly caused by endless trips to court to deal with antinuclear barratry and other legal harassment.
And lastly, the ’show cause’ bar has to be set higher before temporary injunctions are issued by courts in these matters, with a fixed window for public comment during the site approval process.
With these changes, and a moratorium on new coal plants, constriction of a 350 reactor fleet is more than possible.
Quote Comment
May 20th, 2008 at 3:55 pm
Tsakanga: You have some good points. I seriously doubt that electrical generation from coal is going away completely anytime soon.
Consider, however, that many coal plants in the US are rather small and they are very old (we’re talking 50 or more years in age). If we can retire these small, old plants and replace them with large nuclear plants, that is a very good first step.
Next, we should consider the following: why should we build a large, new, “clean” coal plant when we can build a large, new, much cleaner nuclear plant?
Finally, I should point out that the US has more natural gas (nameplate) capacity than both coal and nuclear combined, and most of that is hardly used. Why build more natural gas plants?
Personally, I think that natural gas is a great resource for times when peaking power is needed, but that should be rare. Large, (relatively) efficient combined-cycle gas plants made sense when gas was cheap, but I doubt we’ll see those days again. (Certainly, we won’t unless NIMBY concerns about LNG terminals in the US are overcome.)
So, in short, I agree with your skepticism, but a better energy balance has to start somewhere. “Clean coal” is clearly nothing more than a marketing gimmick. I’m willing to accept “dirty” coal for now, because there is little alternative for the near future; however, I am not about to fall for the line that coal can be made “clean” and therefore is a preferred source of energy.
Quote Comment
May 20th, 2008 at 4:40 pm
Two advantages a natural gas powered gas turbine or combined cycle plant is that they can be kept in shutdown condition and turned on at a start of a button and they can be hidden in little pockets and even their neighbors don’t even know they are there. This is stored power that can be used during peak power even though the plants are expensive to run and are not needed most of the time.
Quote Comment