Reaction kinetics of CaC2 formation from powder and compressed feeds

The production of CaC2 from coke/lime powders and compressed powder pellets are low cost and fast processes. A number of studies have reported the reaction kinetics of these reactions but they are still not well understood and the proposed kinetic models are not comparable due to differences in the reaction conditions. Therefore the reaction behavior of CaO/C powders (0.074 mm) and cubes (5 mm x 5 mm x (4.6-5.1) mm) compressed from a mixture of powders have been studied using thermal gravimetric analysis (TGA) at 1700-1850 degrees C. Kinetic models were obtained from the TGA data using isoconversional and model-fitting methods. The reaction rates for the compressed feeds were lower than those for the powder feeds. This is due to the reduced surface area of the compressed samples which inhibits heat transfer from the surrounding environment (or the heating source) to the sample. The compression pressure had little influence on the reaction rate. The reaction kinetics of both the powder and the compressed feeds can be described by the contracting volume model f(alpha) = 3(1-alpha)(2/3), where alpha is the conversion rate of reactant. The apparent activation energy and pre-exponential factor of the powder feed were estimated to 346-354 kJ.mol(-1) and 5.9 x 10(7) min(-1), respectively, whereas those of the compressed feed were 305-327 kJ.mol(-1) and 3.6 x 10(6) min(-1), respectively.