Kinetic analysis of sludge low-temperature drying experiments: Apparent activation energy consistency

In the drying process, kinetic parameters are essential in predicting experimental output, advancing equipment design, and commercial promotion. Both drying kinetics and reaction kinetics are used in the drying processes, and they have in common the ability to calculate apparent activation energy (Ea). However, no comparative results analysis and the respective characteristics of these two methods have been investigated. Experiments were carried out with four types of sludge (municipal and electroplating sludge) to compare the features of the two methods under convective air drying conditions at 40–70 °C. Moreover, to increase the results’ reliability, 11 drying processes from the literature were selected and their kinetics were calculated. The results show that the deviation of the Ea is less than 6.3%. The consistency demonstrates the validity of both calculation methods. However, the two methods have their characteristics. The drying kinetics requires known dry material size, while the reaction kinetics (“lnln”- method) relies on table lookup to match the mechanism function. The consistency indicates both methods can complement each other, and their joint use broadens our understanding of kinetic analysis. The results also imply that kinetic parameters of the reaction kinetics exhibit kinetic compensation effects, which provides new insights into Le Chatelier's principle.