An innovative method to build a comprehensive kinetic model for air injection using TGA/DSC experiments

In order to study the AIP (air injection process), a practical method was developed to obtain the kinetic data for an AIP by matching the simulation model results with the TGA (thermogravimetry analysis) experiments in our previous work. However, one shortcoming for that method is the non-uniqueness of the kinetic data obtained. The other shortcoming is that TGA cannot measure the exothermic characteristics of a crude oil. The enthalpy values of the reactions are crucial for developing a comprehensive kinetic model as the enthalpy represents the heat generation of the chemical reaction and dominants the heat effect during the AIP. In this study, an innovative method is proposed to build a comprehensive kinetic model by combining both TGA/DSC (differential scanning calorimetry) experiments and simulation. In the low temperature interval, the distillation dominant stage is differentiated from the LTO (low temperature oxidation) stage by comparing the nitrogen purging TGA experiments and the air purging TGA experiments. Then, the LTO stage is further divided into several sub-divided reaction stages with corresponding temperature intervals by analyzing the TGA/DSC data. The kinetic data are estimated by applying the Arrhenius method to sub-divided reaction stages of the TGA experiments. In order to obtain the enthalpy values for oxidation reactions, the negative heat flow of the distillation process is eliminated by subtracting the nitrogen purging DSC data from the air purging DSC data, and the enthalpy values of corresponding reaction stages are obtained from the subtracted heat flow curve whose area of the exothermic peak represents the enthalpy value of a stage. Moreover, the pseudo components are defined based on the nitrogen purging TGA experiments which are associated with the sub-divided reaction stages defined previously to complete the kinetic model. Finally, the kinetic model is validated with the air purging TGA experiments. This study shows a detailed workflow to build a comprehensive kinetic model for AIP by TGA/DSC experiments. An application to a crude oil is also presented to demonstrate its practicability.