February 22, 2007
Debate on Cleaner Coal Continues
From yesterday's New York Times ("Cleaner Coal is Attracting Some Doubts").
My favorite phrase from the article is "capture ready" to describe a power plant design. Sort of like an HDTV-ready TV set. I think I'd like to hold out for power plants that actually capture the carbon...
February 24, 2007 1:38 AM
jim karlock Says:
From the articleGetting carbon out of the gas stream before combustion must be easier, Mr. Smith said, because the post-combustion gases in a pulverized coal plant are 160 times as great.
JK: Since coal is almost pure carbon, how does one remove the carbon and have something left to burn?
February 24, 2007 4:17 PM
You need to understand it isn't "clean" coal, as in, "no CO2," it is "clean" coal, as in "no worse than natural gas." LNG is actually a lot dirtier than regular natural gas, so clean coal is therefore cleaner than LNG, which is what people are proposing to do about our energy problems in this country right now. I find the comparison quite similar to comparing Hitler and Vlad the Impaler, but "Clean coal, better than Vlad the Impaler" didn't fare very well in the focus groups, so they just call it "clean coal."
If you burn the coal with oxygen instead of air, (which is 80% nitrogen,) you don't end up with as much stuff at the end of the smokestack, (by a lot, because a lot of the oxygen in the air combines with the nitrogen, not with the carbon at those temperatures,) which means that it is easier to capture. (This is the capture ready smokestack: it has been proven on a small scale.) The way you get some of the oxygen is from water, (although you have to add more than that, cause just adding water to coal just gives you wet coal*, not a fire, and oxygen is fairly energy intensive to get,) and the water adds hydrogen to the coal, which makes it into something that roughly resembles natural gas, (hence the "gasification.") You didn't actually get any [useful] energy out of that process, but you did use a lot of coal and got some gas out of it.
Then you burn that gas, (with regular old air,) and actually generate the power from it.
*Wet coal actually releases a little bit of methane, for a while, (this is also known as coal gas,) but it is a very slow process. (That is the entire point of the oxygen, it gets hot and it speeds up.) Coal that has already released a bunch of methane, (because it spent a lot of it's time being wet,) tends to be harder to gasify, (the easy bonds have already broken.)
February 25, 2007 8:01 PM
Ron Swaren Says:
"clean coal is therefore cleaner than LNG, which is what people are proposing to do about our energy problems in this country right now. "
Wouldn't another solution be to encourage frugality? Do people need to heat the whole house all night long, or just their sleeping areas? Do office buildings need maximum heat 24 hours a day, or just when and where people are working?
A conversion to natural gas became popular over the last two decades as certain conditions favored the cost and convenience of gas appliances. Now, with a better understanding of fossil fuel risks and with the greater cost effectiveness of new electric generating technologies that trend should be up for serious reconsideration.