Tensi-volumetric studies of the CaCO/sub 3/-CaO-CO/sub 2/ system

Technical Report · Sat Dec 01 04:00:00 EST 1979

OSTI ID:5738676

Shukla, R K

A tensi-volumetric apparatus was developed and used to study two aspects of the CaO-CO/sub 2/-CaCO/sub 3/ system, namely the thermodynamics of the CaCO/sub 3/ (calcite) phase viewed as a pseudo-binary solid solution of CaO and CO/sub 2/, and the kinetics of decomposition of CaCO/sub 3/ (calcite). The solubility of CO/sub 2/ in the calcite (CaCO/sub 3/) phase was studied as a function of pressure and temperature. It is shown that it is possible to obtain calcite of substoichiometric compositions expressed by (CaO x (CO/sub 2/)/sub 1-delta), where at the temperatures of measurement, 773/sup 0/K to 1000/sup 0/K, delta is a small, but measurable quantity. The composition limits of this phase increase rapidly with temperature. Calcite decomposition rates were measured in the range of P//sub Peq/ from 0.05 to about 0.8 and in the temperature range of 853/sup 0/ to 933/sup 0/K. The decomposition rate changed by about three orders of magnitude in this range of P//sub Peq/ at every temperature of study. Decomposition rates of calcite powder depend on particle size, powder bed depth and compactness of samples. Measurements with single crystals of calcite suggest that at least two different processes limit the decomposition rate in different P//sub Peq/ regimes. The apparent activation enthalpy, ..delta..H/sup */, for decomposition at P//sub Peq/ less than or equal to 0.1, calculated in terms of decomposition fluxes, is about 49.2 +- 1.2 K cals mole/sup -1/. At values of P//sub Peq/ near unity, the value of ..delta..H/sup */ rose to about 61.8 +- 1.8 K cals mole/sup -1/. Decomposition rates for powders did not show a consistent apparent activation enthalpy over the range of P//sub Peq/ studied; they varied between 65 and 80 K cals mole/sup -1/.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5738676
• Report Number(s): LBL-9885
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALINE EARTH METAL COMPOUNDS
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBONATES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DECOMPOSITION
KINETICS
OXIDES
OXYGEN COMPOUNDS
PRESSURE DEPENDENCE
REACTION KINETICS
SOLUBILITY
SOLVENT PROPERTIES
TEMPERATURE DEPENDENCE
THERMODYNAMICS