Abstract
The thermodynamic analysis of the thermal decomposition reaction of carbonates showed that the temperatures of thermal stability of dolomite and magnesium carbonate are very similar. Kinetics of isothermal and non-isothermal decompositions of natural dolomite in air atmosphere were investigated. Under the examined conditions, dolomite decomposed in a one-stage process. The final solid products of dolomite’s decomposition were calcium and magnesium oxides. The average value of isoconversional apparent activation energy of non-isothermal decomposition was 205.60 kJ mol−1. The kinetics of decomposition can be described by the power-law model P2/3 with ln(A) = 20.98 for the extent of reaction α < 0.77 and by two-dimensional diffusion model D2 with ln(A) = 21.12 for α > 0.77.
Highlights
Occurring dolomite—a double carbonate of Ca and Mg—CaMg(CO3)2 is typically sedimentary rock associated with calcite, widely scattered in nature
The thermodynamic analysis of the thermal decomposition reaction of carbonates showed that the temperatures of thermal stability of dolomite and magnesium carbonate are very similar
CaO+CO2 dolomite phase; other peaks can be seen for calcium carbonate or magnesium oxide phase
Summary
Occurring dolomite—a double carbonate of Ca and Mg—CaMg(CO3) is typically sedimentary rock associated with calcite, widely scattered in nature. Engler et al [13] based on in situ XRD analysis of dolomite’s decomposition in air concluded that the process between 973 and 1,023 K is as follows: 2CaMgðCO3Þ2, CaCO3 þ CaO þ 2MgO þ 3CO2 ðIVÞ At the latter temperature, the two reactions appear to occur simultaneously as (I) and (III). The starting material was a natural dolomite from the Zelatowa mine (Poland) containing 14.37 mass % MgO, 33.70 % CaO, 3.37 % Fe2O3, 0.11 % Al2O3, 0.32 % MnO and 0.55 % SiO2 with a particle size of B0.25 mm This was studied under isothermal conditions in temperatures ranging from 923 to 953 K and non-isothermal conditions in air atmosphere at different heating rates ranging from 2.5 to 15 deg min-1. The differences may result from the temperature gradient between the sample crucible and the furnace wall, the different temperatures within the sample itself, and the presence of diffusion resistance
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