Notices
Results 1 to 28 of 28
Like Tree1Likes
  • 1 Post By SteveF

Thread: Calcium Oxide. A good way to get pure CO2 from the Air?

  1. #1 Calcium Oxide. A good way to get pure CO2 from the Air? 
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    Calcium oxide - Wikipedia, the free encyclopedia

    From what I find in this article, it looks like you can scrub CO2 from the air simply by heating and cooling Calcium Oxide.

    Calciumoxide is usually made by the thermal decomposition of materials such as limestone, that contain calcium carbonate (CaCO3; mineral calcite) in alime kiln. This is accomplished by heating the material to above 825 C,[1] a process called calcination or lime-burning, to liberate a molecule of carbon dioxide (CO2); leaving quicklime. The quicklime is not stable and, when cooled, will spontaneously react with CO2 from the air until, after enough time, it is completely converted back to calcium carbonate.
    So If I'm reading this correctly, you could start with CaCO3, and heat it up until it liberates it's CO2 (which you then collect), leaving just CaO. Then you can react CaO again with the air, and it grabs CO2 atoms to convert itself back into CaCO3. And we start the process over again.

    I wonder how much energy is lost? Clearly some of the energy used to super heat the CaCO3 can be recovered by harnessing the heat from the CaO + CO2 reaction. But I don't know how much. I wonder if it would be possible to come close to a balance?

    Chemical of the Week -- Lime


    According to this article, the CaO + CO2 reaction actually goes faster if you make Ca(OH)2 out of the CaO first. So I've got part of the reaction here:

    CaO (s) + H2O (l) Ca(OH)2 (aq) (ΔHr = −63.7 kJ/mol of CaO)
    But I can't find a reaction with the energy released for the next step

    Ca(OH)2(s) + CO2(g) CaCO3(s) + H2O(l)



    So the main question: is there a good reason we couldn't use this to sequester lots and lots of CO2 from the air? Or maybe.... just maybe.... use that CO2 to make something like Methanol?




    Some clocks are only right twice a day, but they are still right when they are right.
    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Ph.D.
    Join Date
    Jan 2009
    Posts
    951
    Too energy intersive ,hopw are you ging to provide the heat?


    Reply With Quote  
     

  4. #3  
    Forum Bachelors Degree
    Join Date
    May 2007
    Location
    NC USA
    Posts
    488
    Sigh. Someone has taken all the fun out perpetual motion by inventing the 1st and 2nd laws of thermodynamics.
    Warron likes this.
    Reply With Quote  
     

  5. #4  
    Comet Dust Collector Moderator
    Join Date
    Mar 2011
    Location
    New Jersey, USA
    Posts
    2,848
    Quote Originally Posted by fizzlooney View Post
    Too energy intersive ,hopw are you ging to provide the heat?
    Obviously. burn a bunch of coal to make the electricity
    Reply With Quote  
     

  6. #5  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    Quote Originally Posted by fizzlooney View Post
    Too energy intersive ,hopw are you ging to provide the heat?
    I was thinking you would get a lot of the heat back. After the CaCO3 splits into CO2 and CaO, you take the CaO, put it in the furnace, and combine it with water to create Ca(OH)2, releasing a good amount of heat from the reaction. You won't get as much energy back as the energy that was consumed, of course, but you might get a lot of it back.

    The main loss is that I think you may have to let the CaO cool before combining it with water (not sure if you do or not).


    Calcium oxide - Wikipedia, the free encyclopedia
    Quicklime is relatively inexpensive. Both it and a chemical derivative (calcium hydroxide) are important commodity chemicals.
    Quicklime produces heat energy by the formation of the hydrate, calcium hydroxide, by the following equation:[2]
    CaO (s) + H2O (l) Ca(OH)2 (aq) (ΔHr = −63.7 kJ/mol of CaO)The product, commonly called "quicklime", has many uses on its own. As it hydrates, an exothermic reaction results and the solid puffs up. The hydrate can be reconverted to quicklime by removing the water by heating it to redness to reverse the hydration reaction. One litre of water combines with approximately 3.1 kilograms (6.8 lb) of quicklime to give calcium hydroxide plus 3.54 MJ of energy. This process can be used to provide a convenient portable source of heat, as for on-the-spot food warming in a self-heating can.




    The goal is to find a convenient way of getting CO2 for Methanol production, which in turn is an attempt to store energy from renewable power sources like Solar and Wind. Clearly some energy loss is expected, but if it's not extreme energy loss, then it might still be worth doing so as to capture a fraction of the excess energy produced during strong winds and/or a sunny day, instead of none.

    Besides that, if there were enough infrastructure built, maybe Methanol could begin to compete with gasoline.
    Some clocks are only right twice a day, but they are still right when they are right.
    Reply With Quote  
     

  7. #6  
    Reptile Dysfunction drowsy turtle's Avatar
    Join Date
    Mar 2009
    Location
    UK
    Posts
    2,255
    Quote Originally Posted by fizzlooney View Post
    Too energy intersive ,hopw are you ging to provide the heat?
    Solar cells in the desert pumping CO2 into a deep saline aquifer? Just a thought...

    The rate doesn't need to be particularly high, we have time on the order of decades to use them in.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
    Reply With Quote  
     

  8. #7  
    Forum Ph.D.
    Join Date
    Jan 2009
    Posts
    951
    Totally assinine
    Reply With Quote  
     

  9. #8  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    Suppose nuclear were the power source. There's plenty of heat in those reactions.

    I wonder if it would be possible to work the CaO + H2O -> Ca(OH)2 + Heat reaction into the steam process of a nuclear power plant? Instead of waiting for the CaO to cool after the CaCO3 + Heat -> CaO + CO2 reaction, maybe we could just throw it straight into unheated cold water and let it react. Then we're not really losing any energy we weren't already going to lose anyway from the basic inefficiency of steam engines.
    Some clocks are only right twice a day, but they are still right when they are right.
    Reply With Quote  
     

  10. #9  
    Reptile Dysfunction drowsy turtle's Avatar
    Join Date
    Mar 2009
    Location
    UK
    Posts
    2,255
    Quote Originally Posted by kojax View Post
    Suppose nuclear were the power source. There's plenty of heat in those reactions.
    Or geothermal maybe?

    Quote Originally Posted by fizzlooney
    Totally assinine
    How would you remove carbon dioxide from the atmosphere then?
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
    Reply With Quote  
     

  11. #10 biology is the answer... 
    New Member
    Join Date
    Jan 2012
    Posts
    3
    Plant a lot of trees!

    You can only absorb as much CO2 as you liberated to get to CaO, so that doesn't sound like a practical solution.

    -R
    Reply With Quote  
     

  12. #11  
    Reptile Dysfunction drowsy turtle's Avatar
    Join Date
    Mar 2009
    Location
    UK
    Posts
    2,255
    I believe the point was to store/bury the liberated carbon.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
    Reply With Quote  
     

  13. #12  
    Moderator Moderator
    Join Date
    Nov 2011
    Location
    city of wine and roses
    Posts
    6,222
    If you're serious about extracting CO2 from the atmosphere and the oceans, you first need to look at the way this has always happened with natural processes. There are several biological processes, but the main one for permanent sequestration is geological.

    Weathering of exposed rocks. This is a very slow process by human timeframes, but normal for geological processes. Olivine rocks are the go. Normally this happens by movement of tectonic plates shoving mountains up and exposing previously buried rock formations, some of them containing olivine deposits. If you can find a process that's low energy input required, and that can continue indefinitely with little further maintenance to ensure maximum efficacy, you're on a winner. My personal speculation for solving this problem is just simple quarries with attached windmills, not power generating turbines but grinding mills, converting quarried rocks into gravels and dusts. Just an accelerated version of the natural process - but it needs a lot of tweaking. Unfortunately, you can't just accelerate this process without clogging rivers with sludge because there'll be too much 'stuff' to be carried easily. Eventually, someone will come up with something a bit less clumsy and a lot more manageable but with the same outcome.
    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
    Reply With Quote  
     

  14. #13  
    Forum Freshman
    Join Date
    Oct 2011
    Posts
    6
    your idea is correct. but you should consider the reactions taking place in a practical manner. i don't think its an appropriate method. it requires much energy. it should occur in a close container and the pressure created by the liberation of CO2 may damage the whole system.you can rather do it by reacting a carbonate with concentrated acid and collecting the gas using an appropriate method
    Reply With Quote  
     

  15. #14  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    Quote Originally Posted by Refracktory View Post
    Plant a lot of trees!

    You can only absorb as much CO2 as you liberated to get to CaO, so that doesn't sound like a practical solution.

    -R
    Well, the main problem is getting pure CO2. It's not easy to filter it out of the air. The goal of burning lime to liberate it's CO2, and then reacting the CaO to capture it again is that each time you capture it again, you're breaking it free from the mix of CO2, O2, Nitrogen, and other elements.

    When you then liberate it again, what you're liberating is CO2 in its pure form, so you can put in a storage tank or something, and not just turn around and mix it back into the atmosphere. If you then react that pure CO2 with pure hydrogen to get Methanol, you're creating a petroleum substitute, and you can either store that methanol indefinitely (permanently reducing the CO2 in the air), or put it on the market so it competes with OPEC's natural petroleum (thereby lowering the price of transportation and improving the USA's overall economy). Either option sounds good to me.
    Some clocks are only right twice a day, but they are still right when they are right.
    Reply With Quote  
     

  16. #15  
    Suspended
    Join Date
    Jan 2012
    Posts
    649
    All we need is plenty of power for your setup plus getting the hydrogen from water. This would generate a lot of heat and I thought that this was what we are trying to avoid, so?
    Reply With Quote  
     

  17. #16  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    We need the heat. Heating up CaCO3 is how you make it release its CO2, so the more heat the better.
    Some clocks are only right twice a day, but they are still right when they are right.
    Reply With Quote  
     

  18. #17  
    Suspended
    Join Date
    Jan 2012
    Posts
    649
    By all means let us have more heat, current doctrine hereabouts seems to hold that carbon dioxide can generate heat in abundance. Problem solved. More than this I cannot say for fear of appearing inflammatory.
    Reply With Quote  
     

  19. #18  
    Forum Ph.D.
    Join Date
    Jan 2009
    Posts
    951
    Jax go back to the military forum , youhave no nbusiness here
    Reply With Quote  
     

  20. #19  
    Time Lord
    Join Date
    Mar 2007
    Posts
    8,035
    I'm thinking so long as we don't let the heat escape, how does it matter how hot we need our system to get? Just insulate it well.
    Some clocks are only right twice a day, but they are still right when they are right.
    Reply With Quote  
     

  21. #20  
    Forum Isotope Bunbury's Avatar
    Join Date
    Sep 2007
    Location
    Colorado
    Posts
    2,590
    Limestone has to be heated to 1450C to decarbonize it. A better approach might be the use of magnesium carbonate that will decarbonize at 700C, so uses less fuel and loses less heat through insulation. There are cement technologies being developed that use MgCO3/MgO while recycling the CO2. I am skeptical of this firm's claims, but will be interested to see how it develops:

    Our solution Novacem
    Reply With Quote  
     

  22. #21  
    Reptile Dysfunction drowsy turtle's Avatar
    Join Date
    Mar 2009
    Location
    UK
    Posts
    2,255
    Quote Originally Posted by adelady View Post
    Weathering of exposed rocks. This is a very slow process by human timeframes, but normal for geological processes. Olivine rocks are the go. Normally this happens by movement of tectonic plates shoving mountains up and exposing previously buried rock formations, some of them containing olivine deposits. If you can find a process that's low energy input required, and that can continue indefinitely with little further maintenance to ensure maximum efficacy, you're on a winner. My personal speculation for solving this problem is just simple quarries with attached windmills, not power generating turbines but grinding mills, converting quarried rocks into gravels and dusts. Just an accelerated version of the natural process - but it needs a lot of tweaking.
    I'm not convinced this would work. For the weathering process to happen at significantly higher rates than in nature, you'd need a much more concentrated carbonic acid - and if you've already collected the CO2, why spend time and energy converting it to silicic acid and carbonates and you can just bury it?

    Under 'normal' concentrations of carbonic acid, I doubt you could ever match the weathering of the entire sediment load of every river in the world.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
    Reply With Quote  
     

  23. #22  
    Moderator Moderator
    Join Date
    Nov 2011
    Location
    city of wine and roses
    Posts
    6,222
    For the weathering process to happen at significantly higher rates than in nature, you'd need a much more concentrated carbonic acid -
    No. What you do is change the way, and maybe where, the weathering happens. There's plenty of carbon dioxide in the air and the oceans, no need to 'concentrate' it. The natural process is for rock to be exposed gradually - at least by human time perceptions. In the high cold mountains freezing and thawing will crack rocks progressively and expose more surfaces to the air and weathering processes. That's how tectonic and natural processes do it.

    What we want to do is to geoengineer by speeding up this process, not to substitute a laboratory style instant chemical conversion. Well, we don't "want "to do it. We just have to find the least dangerous way of sequestering carbon to match the dangerous speeding up we've done of the carbon release processes. It's taken a couple of centuries to get to where we are now with release. Our "matching" sequestration process will be badly time lagged but it should be set up to run steadily for at least another couple of centuries.

    Remember, during those centuries we will be dealing with all kinds of disruptions to economic and political life because things will get desperately bad in far too many parts of the world. So the process has to be simple, cheap, repeatable and scalable. Quarrying in the first place, milling the rock into gravels and dusts is pretty straightforward. The biggest question will be how much precious energy can we spare to control the release of dusts or to move gravels and dust to where they'll have a bigger, faster impact. "Crop-dusting" mangroves and marshes would be a good strategy initially - but there are probably specific places where acidic ocean waters upwell that would need first and fastest attention.

    It's not up to me or you to work out the best way to do this now. But it's got to be done sometime or we really will cook all our food sources long before they get near harvest or table.
    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
    Reply With Quote  
     

  24. #23  
    Reptile Dysfunction drowsy turtle's Avatar
    Join Date
    Mar 2009
    Location
    UK
    Posts
    2,255
    The rate of the reaction depends on both the surface area of the sillicates, and the pH of the water. Exposed sillicates are already abundant on Earth, and down the length of a river sediment fines to the sorts of scale you're talking about.

    Now, the Amazon river has an output of around 600 Megatons per year, around 30-50% of which will be sillicates. I find it unlikely that any geoengineering/mining project will have a productivity this high, and this is only a single river. Not to mention that siliceous oozes are still being deposited as abyssal sediments around the world, indicating chemical sillicate weathering occurs at a smaller rate than sillicate sediments enter the oceans.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
    Reply With Quote  
     

  25. #24  
    Forum Freshman Robinol's Avatar
    Join Date
    Feb 2012
    Location
    India
    Posts
    39
    What is the use/advantage of this idea?
    Reply With Quote  
     

  26. #25  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    Quote Originally Posted by Robinol View Post
    What is the use/advantage of this idea?
    To remove CO2 from the air as one weapon against climate change. There is a market for CO2 in the chemical industry, so that could, perhaps, cover some of the costs.
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  27. #26  
    Forum Freshman Robinol's Avatar
    Join Date
    Feb 2012
    Location
    India
    Posts
    39
    But for removing that CO2, we are producing CO2. So how can that be beneficial?
    Reply With Quote  
     

  28. #27  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    Quote Originally Posted by Robinol View Post
    But for removing that CO2, we are producing CO2. So how can that be beneficial?
    Not sure what you mean by "producing CO2" but if we remove CO2 from the atmosphere and use it to create fuels (methane or more complex hydrocarbons) and then burn that then it is better than where we are now because we are not introducing "new" CO2 into the system. And if we use those hydrocarbons to produce plastics, say, then it is sequestered for longer (and we are still not introducing new CO2).

    (Not that I think CaO is the right way to do this)
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  29. #28  
    Reptile Dysfunction drowsy turtle's Avatar
    Join Date
    Mar 2009
    Location
    UK
    Posts
    2,255
    CCS is looking like the most likely technique to be put into widespread use right now, in my opinion.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
    Reply With Quote  
     

Similar Threads

  1. calcium
    By fionabe1985 in forum Biology
    Replies: 1
    Last Post: October 11th, 2011, 11:48 AM
  2. calcium zirconat phase transition
    By khillo in forum Chemistry
    Replies: 2
    Last Post: March 7th, 2010, 02:00 PM
  3. Nitrous Oxide
    By thejj924 in forum Chemistry
    Replies: 6
    Last Post: August 31st, 2009, 03:38 PM
  4. Calcium amount
    By Yash in forum Biology
    Replies: 2
    Last Post: October 19th, 2008, 10:03 PM
  5. Silver oxide
    By thyristor in forum Chemistry
    Replies: 1
    Last Post: September 4th, 2008, 07:13 AM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •