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Germany Fired Up Over Clean Coal
MIT's Technology Review is reporting on the world's first coal-driven power plant designed to capture and store C02 emissions. "Vattenfall's small 30-megawatt plant burns the lignite in air from which nitrogen has been removed. Combustion in the resulting oxygen-rich atmosphere produces a waste stream of carbon dioxide and water vapor, three-quarters of which is recycled back into the boiler. By repeating this process, known as oxyfuel, it is possible to greatly concentrate the carbon dioxide. After particles and sulfur have been removed, and water vapor has been condensed out, the waste gas can be 98 percent carbon dioxide, according to Vattenfall. The separated carbon dioxide will be cooled down to -28 C and liquefied. Starting next year, the plan is to transport it by truck 150 miles northwest, to be injected 3,000 meters underground into a depleted inland gas field in Altmark. Ideally, in the future, the gas will be carried by pipeline to underground storage, says Vattenfall. "
Ideally, in the future, the gas will be carried by pipeline to underground storage
The failure mode of that pipe should be fun. Concentrated CO2, evaporating to gas as it shoots out the crack, turning into a thick fog that settles to the ground and suffocates everything nearby. Like a death cloud. It'll make for some fun camera footage.
Depressurize the liquid to 1 atm and it turns into either a solid or gas, right? CO2 gas suffocates and is heavier than air, or dry ice jams the pipe...
yeah, why the heck don't they convert the CO2 into something usable, like C and O2?
Maybe build another generating plant next door that supplies the energy required to break the molocules...
CO2 is a extremely stable molecule and it would take a great deal of energy to separate the two. The amount of energy it would be take would be counter-productive to the initial problem you are trying to solve.
Until we can figure out how to simulate photosynthesis or just go ahead and the let the trees do it, this just isn't the best solution available.
However, neither is pumping it in to the ground in my opinion. ...since no one is asking, I guess it doesn't really matter though.
Ask the folks in Lake Nyos. Natural CO2 escaped from a lake and killed something like 2,000 people.
Gonna be mighty hard to ask them about it, then.
That CO2 needs to be stored very securely and away from centers of population.
I believe that was exactly the idea behind burying it "3,000 meters underground into a depleted inland gas field in Altmark."
And the article doesn't mention it, but IIRC the reason for burying the waste CO2 is that it gets absorbed by the surrounding rocks and converted into harmless minerals, rather than letting it escape into the atmosphere again. Someone with more geological expertise than I have will have to explain that, though.
I actually have experience with this type of combustion. There is approximately a ~30-35% "penalty" for running the ancillary equipment. The ancillary stuff would be the on-site oxygen separation plant and the CO2 liquefaction.
With the penalty, a 30 MWe* plant would only be putting out ~20 MWe. This is potentially a huge loss of revenue for a generator. Though in the case of regulated utilities, the question becomes how much would YOU be willing to pay for this type of control (because they'll raise you're rates)
(*I know TFA sidebar says 30 MWth)
Nothing happens, even in the unlikely event that a seismic event could open a crack 3000 meters (almost two miles) deep.
Aside from the fact that CO2 is denser than air and will tend to stay in the bottom of whatever hole it's put in, the hole that it is being put in is a depleted gas field -- meaning that the rock is porous enough for the CO2 to disperse through it like a rock sponge. It takes a bit of effort to get the gas back out again. Plus, CO2 mixed with ground water forms a mild acid which tends to react with rock to form carbonates, chemically locking the CO2 in place. (With some variation depending on the specific subsurface rock, of course.)
-- Alastair
Uhh? Why not just use nuclear power, store it into Yucca Mountain (as was planned, until people complained) opposed to storing the nuclear waste in the nuclear plant itself.
SAME concept as the article...
Same concept?
Situation 1: "Sorry, folks, the storage facility leaked into the local groundwater. You'll find a little bit of carbonation in your water supply."
Situation 2: "Sorry, folks, the storage facility leaked into the local groundwater. You'll find a little bit of Cesium-137 in your water supply."
How can I believe you when you tell me what I don't want to hear?
Anyway, nuclear power continues to be a "dirty word" even after the great lengths engineers have gone to in order to make reactors as safe as possible... People will continue to be scared until there is a 100% safe way to remove spent fuel from the planet. If given a choice between sequestering greenhouse gasses and nuclear fuel, I'd probably pick the gas too. The reason is - even though I understand it is absurdly improbable - if something huge happens like an impact or unexpected volcanic activity, I'll take my chances with the gas.
Using their extensive studies of the Yucca Mountain region, experts estimate the chance of a volcanic event disrupting the proposed repository to be about one in 63 million per year. This equals about 0.0000016 percent chance per year that a volcano will disrupt the repository. Put another way, it means there is about a 99.9999984 percent chance per year that a volcanic event will not disrupt the repository. http://www.ocrwm.doe.gov/factsheets/doeymp0341.shtml
Nuclear / Fossil fuel prices:
http://www.world-nuclear.org/info/inf02.html
Fact: Everything I say is fiction.
The only forests that do liberate oxygen and store carbon are young, growing forests. Mature forests are done -- they are in carbon equilibrium.
A study from 40 years ago reported that info. More recent studies have shown that even mature forests continue to absorb CO2.
http://www.forbes.com/feeds/ap/2008/09/11/ap5412821.html
Huh, I thought it was because the earth has a funny way of shifting around and things don't always stay buried for very long which could be problematic for pressurized gasses, but I guess it's because of anti-technology ecofascists.
It's being done, it's being studied, and so far the science indicates it is pretty safe. Pressurized gasses - like natural gas - have existed underground for ages and we've managed to deal with them.
Reaction 1: 6 CO2 + 6 H2O + energy (sunlight) ----------> C6H12O6 + 6 O2
(Note: Reaction 1 is catalyzed by chlorophyll, and there is a lot of other stuff going on.)
Reaction 2: C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + energy
What it means is that plants take in water and CO2 and make sugar (carbohydrates) and oxygen from it, while sugar (and other things) can be burned in oxygen, making carbon dioxide, water, and releasing some of the energy that went to make the sugar.
(Note: You can run reaction 2 with hydrocarbons (CmHn) instead of carbohydrates. You have to supply more oxygen per hydrocarbon molecule, to oxidize the hydrogen. At the same time, oxidizing the hydrogen also releases energy.)
This is called the "carbon cycle". It used to be taught in elementary school science class, and then again in more detail in high school biology and chemistry classes.
"Global warming" is Mother Nature's way of extending the growing cycle, allowing reaction 1 to convert more carbon dioxide and water into sugar and oxygen.
The above oversimplifies the processes involved, but does at least hint at explaining why burying carbon dioxide in the landfill is idiotic: you are burying valuable food and breathable oxygen.
Hmm, lets do the math. Current solar cells have about 10% efficiency. The earth has 6371 km radius which presents an area of 1.28 * 10^14 m^2 to the Sun. The average flux on sunlight on the ground is 1 KW/m^2. And if overcast conditions dropped the efficiency 50%, you would still have 6.38 * 10^15 W. Humans currently use 1.5 * 10^13 W. This means that with these terrible assumptions, we could produce almost 500 times the power that we currently do with just solar power. Considering that newer photovoltaic cells (in design) have efficiencies of over 30%, we are talking over 1500 times. Nice try.
Actually, the natural tendency is for it to percolate out of the ground. We only find natural gas (and oil) in lens-shaped non-porous rock formations which trap the rising gas before it reaches the surface. This is called an anticline. Luckily, the most economical use for the CO2 produced is to pump it back down into the trap, where it will presumably remain for another million years.
Well, Natural gas is explosive too because it is primarily methane (90% CH4 or better) with a few other gasses mixed together with it. Now, before processing, natural gas has a lot of water in it too which would make it closer to as heavy as Co2. But either will dissipate well in the atmosphere unless conditions are just right for them not to (a small window). There isn't much to worry about because the atmosphere isn't really vacuum tube and has wind currents and all to move the Co2 around. This is how your car exhaust mixes with the atmosphere and the root theory behind global warming. Otherwise we could just build pits with soda lime in it near roads, factories and such and cure global warming that way.
I will admit that in a closed space with no wind, sure Co2 can be (is) problematic. But the practical reality of this in real life is rare because simple venting to the outside world overrides the threat. Otherwise, you would almost die when you live in a basement apartment along a busy road because of the Co2 in the car exhaust or if you lit a candle or incense.
Lake Nyos had a catastrophic incident back in the 80's but that was because a volcanic vent pumps Co2 into the lake which at those depths, the cold water saturates with the Co2 and when it is warmed, it releases it. A major venting incident caused the water to rapidly circulate which in turn caused the lake to dump not only the Co2 vented but a good portion of the Co2 that was synced in it. The solution was to place a pipe and pump into the lake allowing the cold water on bottom to be circulated to the top which warms the water and releases a good amount of the Co2 safely and slowly or controlled in a safer manor. The engineering estimates show that the accident should never happen again on the scale it did and that it is reletively safe to live near the lake again.
At the depths the Co2 will be stored, it moves so slowly that is can be measured pretty accurately. If a leak does occur, there should be ample warning and perhaps some safety devices like open pits with Co2 measuring devices in them could be used. But I'm confident that any fears over that which would be present with natural gas are negligible because the very thing that alarms you would also help keep it underground, it's weight. And at the depths that we are looking at, you have to remember that the atmosphere is compressed already at 3,000 meters which is almost 2 miles underground and is almost twice that of at sea level. The Co2 would weigh almost twice as much making it already "on the bottom". There isn't much to worry about