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Alberto says: July 22nd, 2009

Please let me give you some Thermodynamics topics concerning your idea, how you talk about it.

1-You mine CaCO3 (let’s say 1 tonn) … spending energy…
2-You heat CaCO3 to extract CaO (you’ll need to heat to over 900°C… a lot of energy, at least 6 MegaJoules per 100g)
3-Once heat, CaCO3 will absorb 176 KJoules/100g (about 1760 Megajoule for 1 tonn) to decompose to CaO and CO2… producing CO2
4-…now you propose to use this CaO to trap some new CO2 on water… some CO2 that will be less than you’ve already spent!!!

First problem: what you have been doing is get free one CO2 molecule to absorb another CO2 molecule… not so smart…
Second problem: In order to decompose CaCO3 you’ll have to spend 1760 MJ or energy per 1 tonn of CaCO3, the equivalent you might produce burning 53 kg of carbon and producing 196 kg of CO2… all of that to trap 440 kg of CO2… and I didn’t count the energy needed for heating and all other operations!!!

Short: you are proposing to take a substance, spend a lot of energy (and produce a lot of CO2) to extract its CO2 and send it into the atmosphere so that you’ll be able to re-trap some of the CO2 you have just been producing… on thermodynamics, it doesn’t make sense…

Alberto

Ps: as you wanted numbers…
1-Energy needed to calcinate CaCO3: 176 Kjoule/100g CaCO3, equivalent to producing AT LEAST 19,6 g of CO2; heating CaCO3 to 900°C: 6 MJoule/100g CaCO3 theoric (based zero loss efficiency)
2-CO2 generated during the production of lime: 44g CO2 from 100g CaCO3 decomposition, 19.6 g CO2 due to you need to give energy to decompose 100g CaCO3… at least 180g CO2 for heating of 100g CaCO3 based on Carbon rich fuel
3-CaCO3 calcination is a process that is thermodynamically possible only at very high temperature (900°C or more); no way of proceeding without heating.

Jem Cooper says: February 9th, 2010

Alberto,
The plan only makes sense if you capture and sequester the carbon dioxide produced in the calcination step.

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