About two weeks ago, the City Beat got a press release from UND about this new research project to improve so-called "clean coal" technology. We’re just running the story today because it took me that long to figure out how this technology could work.
It’s hard to talk to engineers because, it seems, they either think you’re not smart enough to understand, which means they won’t explain exactly what they’re researching. Or, if you really press them, they explain half of the research because they now assume you know more than you do. You can’t win!
In short, UND wants to find a membrane that will do a really good job filtering CO2 from the exhaust of coal-fired power plants. Brian Tande, a native of western North Dakota, is the lead on this project.
I’ll assume you have no idea how clean coal technology works so the rest of this post will put that membrane technology into context. By the way, some environmentalists like to point out that clean coal isn’t totally clean because there’s no way to scrub out all the pollutants.
Basically, there are three broad classes of clean-coal technology:
- Pre-combustion: The process of extracting CO2 begins before actual combustion. Coal is heated but not actually combusted so that it forms a gas. When the gas is burned, it creates a high concentration of CO2, higher than when coal is burned regularly. This high concentration makes it easier, and therefore cheaper, to remove the CO2.
A gassification plant produces electricity at a rate of 7.8 cents per kilowatt-hour, which is more than a regular coal-fired plant. Scrubbing the exhaust of CO2 would bring the cost up to 10.2 cents per kilowatt-hour.
- Post-combustion: Here, the process of extracting CO2 happens after coal is burned in a regular power plant. Because the concentration of CO2 is lower, it has to be increased in some way to reduce the cost of extracting it. The membranes UND is researching is part of this class of clean-coal technology.
A regular coal-fired plant produces electricity at 5 cents per kilowatt-hour. Scrubbing the exhaust would bring the cost up to 8.25 cents per kilowatt-hour. The membrane technology, if it works as well as hoped, could bring that down to 7.76 cents per kilowatt-hour.
- Oxy-combustion: In this process, coal is burned with lots of oxygen, producing CO2 diluted in water. It’s apparently easier to remove CO2 from water than from membranes and solvents used in post-combustion. But separating the oxygen is expensive.
I don’t have any data on costs.
Let me zero-in on post-combustion technology now. There are three main approaches:
- Solvents: The power plant’s exhaust goes through a solvent that has an affinity for grabbing onto CO2 molecules. This is a process is one with a long track record in other industries, such as the semiconductor industry where it’s used to remove dissolved gases from water. The problem is you have to bring the temperature of the exhaust down for the amine to work well and then you have to bring the temperature of the solvent up for it to release its hold on CO2, so you can reuse the solvent. All those temperature changes take energy, which makes the process more expensive.
By the way, when you read "amine" in the literature, just translate it to solvent because that’s what the solvent’s made of.
- Membrane-based separation: The power plant’s exhaust goes through a membrane where the CO2 is filtered out. The problem is for this to work well there has to be a big difference in pressure between the one side of the membrane and the other. Either you’ve got high pressure pushing the CO2 through the filter like a spoon mashing lumpy gravy through a sieve or you’ve a a vacuum pulling the CO2 though the filter. Either way, this requires lots of energy, which makes it expensive.
- Membrane absorption: This is the hybrid process that UND is looking into. The solvent goes through the membrane where most of the CO2 is stripped from it. This means less heat is needed to remove the remaining CO2 from the solvent.
The energy savings apparently works like this: Membranes use less energy and extract less CO2 in a given amount of time. Solvents use more energy and extract more CO2 in the same amount of time. But you combine the two and you make the solvents more efficient, removing the same amount of CO2 but using less energy.
It took me about several days to figure this out, piecing together what I got from my correspondence with Brian Tande and from research online. Engineering is subtle that way. I sent this matrix over to Tande and he said it’s "basically correct":
| Energy used | CO2 extracted | |
| Membrane alone | Less | Less |
| Solvent alone | More | More |
| Membrane and solvent | Medium | More |
Jackpot.
The exact mechanism that the UND team is looking at was a bit hard to piece together because I’d assumed that the polymeric, or plastic, membrane the team wants to use would be too fragile for the heat.
There are two kinds of membranes in wide use:
- Polymeric: The advantage of these is the polymers can come in long thin tubes that offer a lot of surface area for the CO2 to bond to, which means the membranes are more efficient. The disadvantage is polymers can’t handle that much heat.
- Ceramic: The advantage is these can take the heat, but they don’t offer as much surface area. Basically, a ceramic membrane is a sieve with millions of tiny holes that block certain molecules, CO2, say, from passing through. They’re also heavier and more expensive.
Tande said the greater efficiency of the polymeric membrane might lower the amount of heat required such that the polymers won’t get destroyed. If it turns out the polymembric membrane just isn’t viable, he said the team would turn to ceramics.
The interesting thing to me is the trade-offs involved in this project as is true with so many engineering challenges. You can have clean coal, but how much would you be willing to pay? The cool thing about engineering is it can bring down those costs and actually make an unviable policy viable.
* Actually, it’s called "partial pressure," which is the pressure of one of the gases in a mixture of gas. So the partial pressure of the CO2 is the one that has to be different from the pressure on the other side of the membrane. I’m sure the chem nerds will know why this is important, but I was a biology nerd in high school and have no idea.
The engineering aspect of this project is interesting and all, but do we know much CO2 and other pollutants are removed? If solar and wind are basically 0 and burning coal in a furnace is 100 in terms of pollutants released, where does so called, “clean coal technology” fall?
“”CO2 is not a pollutant, it is part of the animal-plant life cycle, without it, plant life would not exist on earth. Further, increased carbon dioxide in the atmosphere increases plant growth, which is a very good thing. Further, the amount of anthropogenic carbon dioxide in the atmosphere that was emitted by man is around 3% of the total. In 2008, the concentration of CO2 in the atmosphere was 385 ppmv (parts per million by volume).
Therefore, man’s total anthropogenic contribution is only 12 ppmv, a miniscule amount and if man produced no CO2 at all, the amount in the atmosphere would only drop back to the level we had in 2002-2003.”"
http://climaterealists.com/index.php?id=1552
Thank you for the minority view, which, in this case is a series of misleading nonsequitur statements.
1) No, duh, Sherlock, CO2 is a naturally occurring substance. There are a lot of things that occur in nature that in large enough proportions are bad for you. Try drinking your body weight in water and see what happens.
2) That’s nice that it makes plants grow, but if it also puts Florida under water and gives us more Hurricane Katrinas, it’s still bad for us.
This is a ludicrous argument because you’re saying if a little CO2 is good, a lot of CO2 is better. Ever overfertilize your lawn?
3) Just because CO2 isn’t 50 percent of the atmosphere, doesn’t mean it can’t be a problem. Small concentrations of gases or chemicals may have small effects, but the point is those things add up, a la the butterfly effect.
CO2 is only 0.038 percent of the atmosphere, but it feeds all the plants that exists. Whoa, can such a tiny amount of gas make such a big difference?
Can tiny amounts of gas be bad for you also? A hundred parts per million of CO, or carbon monoxide, is enough to harm your health. That’s 0.01 percent of the air.
I’d be more inclined to skepticism if you actually had a scientific argument to make instead of the equivalent of “gee, it doesn’t feel warmer, global warming doesn’t exist.”
I isn’t the majority view because you say it is.
“”
Because, as an engineer I have extensive training on the actual limits placed on human activities by the LAWS OF PHYSICS. For more than a quarter of a century I have tried to design things that violate the LAWS OF PHYSICS. I am ashamed to admit that I HAVE NOT BROKEN ANY OF THEM YET. As an engineer I am in the FRONT LINES fighting the LAWS OF PHYSICS every day. So far the LAWS OF PHYSICS are winning, 99-0.
So, here is one of those NASTY little LAWS OF PHYSICS, it’s called the THIRD LAW OF THERMODYNAMICS. It can make for a really drowsy read, but the simple version states:
“IT IS IMPOSSIBLE TO TRAP HEAT”
Yep, that’s it, pretty simple; it means that there is NOTHING NATURE, OR A MAN/WOMAN CAN DO TO TRAP HEAT.
This LAW is demonstrated MILLIONS of times every day. When you put more insulation into the attic of your house, you are SLOWING the flow of heat from inside (umm, warm and toasty) to the outside (ugh, cold and wet). You are NOT TRAPPING HEAT.
Ask yourself this simple question; if a Greenhouse can “TRAP HEAT” why is it colder inside one in January than in August? Why can’t you “trap” the heat from August and use it during the whole rest of the year? Because of the THIRD LAW.
So, if the THIRD LAW is enforced in manmade greenhouses on the surface of the earth, why is it not enforced in the atmosphere of the earth? Simple answer, it applies equally in all locations.
So you are probably now asking, what’s that whole Lobotomy thing about? Back in the 1930’s and 1940’s there was a “consensus” that lobotomies’ were an effective treatment for mental disorders. Unfortunately, one sibling of a recently deceased US Senator from Massachusetts had this “therapy” applied to her. In fact, the doctor that “perfected” the lobotomy was awarded a Noble prize for his efforts to torture and cripple individual human beings. Of course, it was later determined that the “consensus” was “mistaken”. Whoops! The next “consensus” will certainly do better, we promise.”"
http://climaterealists.com/index.php?id=4243
Another ludicrous argument.
1) Yes, obviously the earth radiates heat and obviously CO2 can’t trap heat. The fact is the earth also absorbs a lot of heat from that thing called the sun. So if the rate of heat that’s radiated is slowed down, then the atmosphere will get warmer simply because it’s constantly getting more heat.
There’s this planet called Venus where 96.5 percent of the atmosphere is CO2. It is a hell house where the surface temperatures are enough to melt lead.
2) So what if there are agreed scientific facts in the past that have proven to be wrong? ALL scientific theories begin with people that agree and people that disagree. They argue; they experiment; then eventually reach a consensus. That’s how science works.
FAIL. If you think for yourself instead of repeating propaganda, you might get it right once in a while.
“”If you think for yourself instead of repeating propaganda, you might get it right once in a while.”"
FAIL! And where is your research published? Are you not repeating propaganda?
Your left is showing again.
Thanks Tu-Uyen, Those are some of the best rebuttals I have seen concerning AGW. I’m guessing C.Y. got his engineering degree at the likes of Oral Roberts University.
Yeah, I’m a total Communist, just like that other Communist Pat Robertson:
http://www.youtube.com/watch?v=NhmpsUMdTH8
CY, your irrational partisanism is showing.
CY,
I hear Michelle Bachman and James Inhofe have openings. Sounds like the perfect match to me…
You have to ask your Tu why is it that you believe so hard in something – (globle warming or CO2 for causing it) when there isn’t ONE study that you can point to that conclusively points to man made C02 as the reason for globle warming. (using all greenhouse gases in the study) Why has the earth cooled or stayed the same temp for the last 10 years?
Because unlike you, I don’t read just the propaganda. Try the references in the Wikipedia article.
http://en.wikipedia.org/wiki/Global_warming#Temperature_changes
There are several that mentions temperature increases over the past century.
You do realize that a 10-year trend isn’t really that meaningful in climate change, right? Because the increases are seen over many decades not a decade.
Everything CY has quoted and what you have just mentioned smacks of unscientific misdirection typical of the propaganda Web sites.