Heat required to liberate CO2 with one kg-mole CaCO3
Heat required to liberate CO2 with one kg-mole CaCO3
(OP)
Please advise me what is the required heat to liberate CO2 with one kg-mole of CaCO3, starting from room temperature of 68F, thanks. I know CO2 will start to liberate @932F.





RE: Heat required to liberate CO2 with one kg-mole CaCO3
m = mass of CaCO3
cp = heat capacity
T = delta T
RE: Heat required to liberate CO2 with one kg-mole CaCO3
Do you know Cp at 68F?
Is average/mean Cp_mean=(Cp_932+Cp_68)/2?
Thanks for the response.
RE: Heat required to liberate CO2 with one kg-mole CaCO3
Thanks.
RE: Heat required to liberate CO2 with one kg-mole CaCO3
Sorry that I don't have some actual numbers to help you out with.
RE: Heat required to liberate CO2 with one kg-mole CaCO3
My apologies if my questions are too direct.
Zoobie,
Thanks for the response.
Sam
RE: Heat required to liberate CO2 with one kg-mole CaCO3
you can make it in two steps, first the heat required to get to 932F, then the heat of reaction for the given conversion, if you know your equilibrium composition use it otherwise you should try to know it.
RE: Heat required to liberate CO2 with one kg-mole CaCO3
Forgot about the reaction half.
RE: Heat required to liberate CO2 with one kg-mole CaCO3
Is there a simple way of finding the heat quantity absorbed by CaCO3 to liberate the CO2?
RE: Heat required to liberate CO2 with one kg-mole CaCO3
Zoobie told us
CaCO3 -> CaO + CO2
first you will have to balance the equation, then you will use the heat of formations (usually refered to as DeltaF) multiplied by your stechiometric coeffs (remember reactives are negative, products are possitive) and make the addition, the result of that is your heat of reaction.
RE: Heat required to liberate CO2 with one kg-mole CaCO3
Do you have a solution yet?
This is a very basic equilibrium CaCO3 = CaO + CO2(g)
It isn't quite correct to say that CO2 is liberated at a certain temperature; instead, the equilibrium CO2 pressure is a function of temperature. Write each ΔGf of each compound as a function of temperature. Of course, ΔGf = ΔHf – T ΔSf.
From ΔGRxn = ΔGf, CaO + ΔGf, CO2 - ΔGf, CaCO3, get ΔGRxn = ΔHRxn – T ΔSRxn.
This ΔHRxn may be sufficient to answer your question. For a little more understanding,
ΔGRxn = - RT ln PCO2
so
PCO2 = exp [-ΔGRxn/RT]
and at PCO2 = 1 atm,* ΔGRxn = 0
*1 bar if that's the thermochemical standard state being used.
Gaskell's book Introduction to Metallurgical Thermodynamics (most recent edition is titled Introduction to the Thermodynamics of Materials) is pretty thorough at explaining condensed phase-gaseous equilibria (including oxide-carbonate equilibria).
Thermodynamic Properties of Minerals and Related Substances at 298.15 K and 1 Bar (10 Pascals Pressure and at Higher Temperatures) (US Geological Survey Bulletin 1452) by R. A. Robie et al. has all the necessary data.
Note that CaCO3 has more than one crystal structure; use the data for calcite.
RE: Heat required to liberate CO2 with one kg-mole CaCO3
Thanks for the reply. Without going to the books you mentioned, I cannot comprehend the equations with lots of unknowns.
RE: Heat required to liberate CO2 with one kg-mole CaCO3
The thermodynamic data are readily available, e.g., see the tables
'Standard Thermodynamic Properties of Chemical Substances' in CRC Handbook of Chemistry & Physics or
'Heats and Free Energies of Formation of Inorganic Compounds' in Perry's Chemical Engineers' Handbook.
Note that the CRC book gives heats of formation in kJ/mol while Perry's uses kcal/mol (& these are gram moles).
RE: Heat required to liberate CO2 with one kg-mole CaCO3
RE: Heat required to liberate CO2 with one kg-mole CaCO3
http://en.wikipedia.org/wiki/Calcination
http://en.
Besides the heat of reaction (which can be taken from above articles), the other factor needed is the heat capacity Cp of CaCO3, which from Robie et al. is
Cp = 99.715 + 0.026920 T - 2.1576x10-6 T-2, J/mole/oK
To heat CaCO3 from T1 to T2 , integrate: ∫Cp dT.
Of course, T is in oK.
For the reaction to go rapidly, heat to T2 = 1171 oK, which is where the equilibrium PCO2 = 101 kPa (1 atm).
RE: Heat required to liberate CO2 with one kg-mole CaCO3
RE: Heat required to liberate CO2 with one kg-mole CaCO3
Cp(CaCO3) = 99.715 + 0.026920 T - 2.1576x106 T-2, J/mole/oK
valid for T = 298 to 1200 K,
from Thermodynamic Properties of Minerals..., Robie et al. (1979).