Determination of the Apparent Carbon Oxidation Reaction Order by a Microfluidized Bed and Its Application to Kinetic Models

Abstract

During carbon oxidation, the apparent reaction order n ranges from 0 to 1. Considering the importance of the value of n to the accuracy of char combustion rate prediction models and the error caused by subjective selections of its value, this study proposes a fast, simple, and accurate method to determine n, the results of which can be applied to improve the accuracy of kinetic models. In the kinetic control region, the apparent carbon oxidation reaction order n was first determined using a microfluidized bed (MFB). As an example of its application, the value of n thus determined was applied to a universal prediction model of the char combustion rate; the model was further developed using the shrinking-core model to predict the combustion rate of graphite during the entire reaction process. The result shows that the apparent reaction order is close to zero (0.178). The accuracy of predictions using the aforementioned modified model was found to be improved, and the accuracy of the model, as further developed, is nearly unaffected, indicating that this method of determining n has a broader application potential.

Kinetic Study of Coal Char Thermal Deactivation

“…Different coal chars have distinct deactivation rates. Some research proposed the model to simulate the char reactivity in char combustion. − For example, Wang et al developed a model for the chemical reactivity of biomass chars and proposed an equation for char gasification based on a gas–solid collision theory. They predicted the char reactivity by some properties of chars for certain coals, and the model showed a good performance for reactivity prediction.…”