Clean Coal?

  1. russ_watters

    Staff: Mentor

    I'm not seeing it. The problem is obvious: The primary combustion products of coal are water and carbon dioxide. The proportions vary with the type of coal, but a considerable fraction of the energy released by burning coal comes from combustion of carbon, so if no carbon dioxide is released, then the primary component of the ash must be unburnt coal.

    Basically as described it is just a catalyzed reaction to remove the hydrogen from coal, releasing drastically less energy than burning the coal the normal way.
  2. jcsd
  3. it depends; if the energy released this way can directly create an emf, as in fuel cells, then there's no issue. if the energy released this way is used for a heat engine then yeah its no good.
  4. mheslep

    mheslep 3,405
    Gold Member

    The chemical looping process out of OSU does create carbon dioxide, though there's no hot exhaust products 'smoke stack' required. The article has it wrong, or is at least sloppy. An advantage claimed here is the process creates nearly pure CO2 in an already separated stream ready for storage; it doesn't have to be separated from a exhaust flume containing combustion products.

    C11H10O (coal) + 26/3 Fe2O3 → 11 CO2 + 5 H2O + 52/3 Fe

    With no combustion I suppose NOx actually would go to zero.

  5. AlephZero

    AlephZero 7,248
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    If you google "fox news global warming", that "problem" may not be so obvious to Fox News as it is to PF.
  6. Q_Goest

    Q_Goest 2,989
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    Thanks for the explanation mheslep. I looked at it and saw the CO2 was being produced but didn't understand what was unique about this set up.

    I guess there are a few issues that will be addressed for any kind of clean coal system such as this.
    1) How much more will the power from a plant using this technology cost? That's a function of capital cost, operating cost, power cost and efficiency.
    2) Can the CO2 be sequestered in any reasonably reliable way and how much will that add to the cost of power from such a plant? I would presume the CO2 would be put underground, but it has to stay there of course. The plant would have to be built on a location that had the right geology to 'bury' the CO2 for a period long enough to ensure it wouldn't affect the environment. That seems problematic. If the CO2 has to be shipped (via pipeline or other means) to a 'landfill' where it can be sequestered, great, but it has to be done at an economical cost.

    I wonder how those hurdles affect the cost of clean coal?
  7. russ_watters

    Staff: Mentor

    Thanks for the clarification.
    What combustion products? The primary combustion products of coal are CO2 and water anyway and condensing out the water is both easy and boosts your efficiency, leaving you with just CO2 and only trace amounts of other stuff -- not much different from the claimed benefit of this process.

    Is the only benefit then that the small amounts of other nasties in coal don't get burned? I was under the impression that they were already scrubbed from the exhaust pretty effectively (hence the recently realized ability to see the sky in Los Angeles).
  8. It's impossible for three very good reasons:

    First, what you're trying to bury is the products of generating electricity. In order to bury and compress all of it, you'll probably end up using more energy than what you got out of it by burning it in the first place.

    Second, the sheer quantities we're talking about alone make it impractical. One large coal power plant uses several tons of coal a day. So that's several tons worth of waste gas that would need to be stored per day, per plant. There's simply no way to make it work practically.

    Third, this idea is really dangerous. The Lake Nyos disaster shows that there are some very substantial and very real risks of CO2 gas eruptions, especially since you're basically putting it in hollowed out gas pockets.

    This whole thing is just another impractical fantasy born out of desperation to avoid the inevitable use of nuclear power.
  9. mheslep

    mheslep 3,405
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    That was my first thought - elimination of CO, H2S, SOx, etc. Yes they get that benefit but that's not the major motivation. According to them one of the cost drivers of CO2 sequestration is low concentration of CO2 (relative to N2).

    Another advantage is they claim an all-in energy efficiency of 64%, versus ~45% with the latest super critical coal boilers.
    Last edited: Feb 22, 2013
  10. mheslep

    mheslep 3,405
    Gold Member

    My take away from the article is that, economically, CO2 sequestration is really two part problem: 1) cheap separation, 2) burial (or reuse?). They are apparently claiming an innovative solution for part one, which was not trivial. Part two, burial: left as an exercise to the reader.

    I suppose there may eventually be other possibilities for the CO2 besides burial, like feeders for biofuel plants.
  11. Borek

    Staff: Mentor

    Yucca Mountain perhaps.

    Sorry, couldn't resist.
  12. Borek

    Staff: Mentor

    You may want to check your numbers.
  13. SteamKing

    SteamKing 11,019
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    The Cumberland, Tennessee coal plant is capable of generating about 2400 MW of electricity and consumes about 20000 tons of coal per day. The hopper railcars carrying the coal can handle 80-125 tons of coal per car.

  14. I'll add to Steamking's comment with another example, the Taichung power plant in Taiwan. For 5,780 MW of generated electricity it consumes 14.5 million tons of coal a year, so divided by 365 days in a year that comes out to 39,726 tons per day. Dividing further I figure it takes about 6.87 tons per day to generate 1 MW of power.

    Now as for it's emissions, all that material going in is going to have to come out, right? Well it does.....only combined with oxygen which ends up adding mass to what was already put in. According to the Carbon Monitoring for Action in 2009 that plant put out a total of 36,336,000, which comes out to 99,550 tons per day. So from that it would appear that sequestration is a pipe dream.
  15. jim hardy

    jim hardy 5,460
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    thank you. I get too mad to talk rationally about sequestration. IMHO it's just a scheme to enrich Al Gore.

    That's a train roughly a mile long every day for that plant.
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