Characteristic and kinetics of light calcination of magnesite in micro fluidized bed reaction analyzer

The calcination reaction characteristics and reaction kinetics of magnesite powder in nitrogen and air atmosphere were studied by microfluidic bed reaction analyzer (MFBRA) and thermogravimetric analyzer (TGA). It was shown that the activation energy of magnesite calcination measured in nitrogen and air was quite similar, indicating that the oxygen in the air had little effect on the calcination of magnesite. The time for complete decomposition of magnesite in MFBRA was short as a few seconds in MFBRA at temperatures above 800℃, showing its reaction rate much quicker than that in TGA, which revealed the difference between TGA and MFBRA in measuring the reaction kinetics. Both activation energy and pre-exponential factor are significantly lower in MFBRA (about 125 kJ/mol, 105 s-1) than in TGA (about 200 kJ/mol, 1015 s-1). The gas product CO2 produced by magnesite decomposition is difficult to fully flow out from the crucible of TGA and thus inhibits the decomposition reaction of magnesite. For MFBRA, it can effectively reduce the inhibition effect from the formed CO2 that easily flows into the main gas flow surrounding the particles. It is also found that the magnesite decomposition reaction follows the nucleation and growth control model in both MFBRA and TGA. Overall, for the reaction in fluidized beds, the study verifies that MFBRA provides a reliable secure of the reaction rate and kinetic parameters for the gas-formation calcination or decomposition reactions like tested light calcination of magnesite. © All Right Reserved.