Kinetic studies of graphon and coal-char reaction with NO and O2: direct non-linear regression from TG curves

Abstract

The reactions of carbonaceous materials (graphon and coal-char) with NO, O2 and NO+O2 were investigated by a thermogravimetric analysis (TGA). A method of direct non-linear regression of the kinetic equation was applied for a simultaneous calculation of the apparent activation energy, frequency factor and reaction order from a single TG curve of carbon gasification in various atmospheres. It was proven that the proposed calculation method is applicable for the calculation of kinetic parameters from overlapping processes. Calculations from TG curves of the above reactions demonstrate that NO-carbon and (NO+O2)-carbon reactions contain two processes, while O2-carbon is a single process. The reaction order of O2-carbon is approximate 0.5, while the reaction orders of NO-carbon or (NO+O2)-carbon reaction are dependent on the process and type of carbon. Graphon shows higher apparent activation energy than coal-char due to the pore structure and uncatalysed effects.