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Topic: Can water be avoided in the Limestone cycle  (Read 1598 times)

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Offline smathew

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Can water be avoided in the Limestone cycle
« on: January 28, 2019, 01:34:39 AM »
I am doing a science fair project and have a question about the limestone cycle. A typical limestone cycle has 3 parts given below:

Cycle - Part 1:
              CaC03 + Heat -> Ca0 + C02

Cycle – Part 2:
              Ca0 + H20 -> Ca(OH)2

Cycle – Part 3:
              Ca(OH)2 + CO2 -> CaC03 + H20

The question is - Can Part 2 of the above cycle be skipped i.e. the part that requires water? And shorted the cycle as:

Cycle - Part 1:
              CaC03 + Heat -> Ca0 + C02

Cycle – Part 2:
              Ca0 + CO2 -> CaC03

Appreciate help in this.

Thanks
SMathew

Offline Borek

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Re: Can water be avoided in the Limestone cycle
« Reply #1 on: January 28, 2019, 02:32:40 AM »
Reactions are OK, but would that be still called limestone cycle? And would it be practical to use dry CaO as a mortar?
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Offline smathew

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Re: Can water be avoided in the Limestone cycle
« Reply #2 on: January 29, 2019, 12:21:58 AM »
Thank you for the reply. For the project, I plan to use limestone to capture CO2 from the air. If possible, I would like to avoid using water. Can this be practically achieved?

Thanks

SMathew

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Re: Can water be avoided in the Limestone cycle
« Reply #3 on: January 29, 2019, 03:47:26 AM »
While not impossible I doubt it will be efficient and practical. Water definitely speeds up reactions involved, and it is much easier to work with liquids than with the dust.
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Offline Enthalpy

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Re: Can water be avoided in the Limestone cycle
« Reply #4 on: January 29, 2019, 10:01:32 AM »
I just wonder what the benefit would be, since CaO is obtained from CaCO3, from which CO2 is released by heat. If the goal is to reduce the CO2 concentration in the atmosphere globally, releasing first as much CO2 provides no gain. Or did I misintepret? Reduce the CO2 concentration just locally? Other goal?

One process that absorbs CO2 uses instead silicates from rocks. If M is a metal like Ca, Na2, Mg, K2... the MSiO3 rock put in contact with CO2 transforms in MCO3 and SiO2, simplifying much. It consists in tapping the unwanted pure CO2 exhaust of a power plant or a CaO factory, compress it and inject it in well chosen rock formation. Even that simple process, where CO2 is already concentrated and very little more is done, is presently asleep because emission bonds are too cheap for it.

Water consumption: I'm pretty sure that finely divided CaO absorbs any residual moisture from the air, whatever dry the atmosphere is, even in the worst desert. So CaO put in very fine contact with the air for CO2 absorption would find its water too.

Beware of the danger of CaO and Ca(OH)2 in the air. At some point you need an intimate contact with the atmosphere, which means a fine powder. Alas, Ca(OH)2 is caustic and CaO is worse. These things have nothing to do in your lungs, not even in small amount. Check the health literature about making CaO and using it in cement.

Offline smathew

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Re: Can water be avoided in the Limestone cycle
« Reply #5 on: February 02, 2019, 11:54:36 PM »
While not impossible I doubt it will be efficient and practical. Water definitely speeds up reactions involved, and it is much easier to work with liquids than with the dust.

Thank you for the help.

Offline smathew

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Re: Can water be avoided in the Limestone cycle
« Reply #6 on: February 03, 2019, 12:11:23 AM »
I just wonder what the benefit would be, since CaO is obtained from CaCO3, from which CO2 is released by heat. If the goal is to reduce the CO2 concentration in the atmosphere globally, releasing first as much CO2 provides no gain. Or did I misintepret? Reduce the CO2 concentration just locally? Other goal?
Thank you for the suggestions and guidance.

The plan is to capture the CO2 released when heating CaCO3 and propose using it for industrial use.
 
One process that absorbs CO2 uses instead silicates from rocks. If M is a metal like Ca, Na2, Mg, K2... the MSiO3 rock put in contact with CO2 transforms in MCO3 and SiO2, simplifying much. It consists in tapping the unwanted pure CO2 exhaust of a power plant or a CaO factory, compress it and inject it in well chosen rock formation. Even that simple process, where CO2 is already concentrated and very little more is done, is presently asleep because emission bonds are too cheap for it.
Thank you for the suggestion of using silicates. I select CaCO3 because of the availability in nature. I will study at the availability of silicates.

Beware of the danger of CaO and Ca(OH)2 in the air. At some point you need an intimate contact with the atmosphere, which means a fine powder. Alas, Ca(OH)2 is caustic and CaO is worse. These things have nothing to do in your lungs, not even in small amount. Check the health literature about making CaO and using it in cement.
Thank you for the warning.

Regards
SMathew

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