Kinetics of Crude-Oil Coke Combustion

Coke is a solid or semiliquid material that deposits on the sand-grain surface area and is eventually burned as a fuel during an in-situ combustion process. Its combustion is the main source of energy to sustain the fire front. This study investigates the effects of different variables - such as specific surface area, oxygen partial pressure, and oil content - on the coke combustion by thermogravimetric analysis (TGA). Each variable was varied while the others were kept constant. The TGA and the derivative thermogravimetric (DTG) curves were subjected to kinetic analysis. The rate equation produced indicated that the rate of coke combustion was proportional to the coke content yet to be burned, oxygen partial pressure, and sand-grain specific surface area. The rate constant followed an Arrhenius-type equation for the temperature dependency. The rate equation was tested for the range of specific surface areas of 0.126 to 24.3 m/sup 2//g (615 to 119,000 ft/sup 2//lbm), oil content of 10 to 58 wt%, and oxygen partial pressure of 5 to 50 kPa (0.05 to 0.50 atm). The model's validity was tested for various crude oils from different geographical locations in the U.S., Canada, and Latin America.