| Description |
The kinetic parameters for the pyrolysis of bitumen-impregnated sandstone (tar sand) particles have been determined by thermogravimetric analysis (TGA). The experimental techniques included both isothermal and nonisothermal methods. The tar sand deposits investigated in this study, all of which are oil-wet sands from the Uinta Basin in the State of Utah, included PR Spring Rainbow I, Whiterocks, and Sunnyside, The pyrolysis of tar sand particles 1 and 4 millimeters in diameter has been investigated. The isothermal experiments indicated that first-order kinetics fit most of the bitumen conversion range for high pyrolysis temperatures, while a secondorder assumption describes the data best at low pyrolysis temperatures. The first-order assumption gave an apparent activation energy of approximately 30 Kcal/mol, while the second order assumption gave an apparent activation energy of about 50 Kcal/mol. The nonisothermal data were analyzed according to Friedman's procedure and the overall integral method. The results of the analyses gave a mixed reaction order between one and two, with an apparent activation energy of approximately 40 Kcal/mol. The intrinsic kinetics of the combustion of the carbonaceous residue or coke deposited on the sand during pyrolysis was studied by TGA. Nonisothermal experiments with a fixed heating rate but with various oxygen partial pressures were conducted. The results were analyzed to obtain the kinetic parameters by the integral method and by the method of Freeman and Carroll. The analyses indicate a reaction order between one and two relative to the unreacted fraction of coke and a fractional order dependence on oxygen partial pressures. The first-order assumption with respect to the unreacted fraction of coke led to an apparent activation energy of 28 kcal/mol and an oxygen partial pressure dependence of 0,5, The second-order assumption gave an apparent activation energy of 43 Kcal/mol and oxygen partial pressure dependence of 0.75. |
