Study on vacuum pyrolysis of oil sands by comparison with retorting and nitrogen sweeping pyrolysis

Vacuum pyrolysis is a promising technology for the production of fossil fuels from oil sands. In this study, vacuum pyrolysis was compared with retorting and nitrogen sweeping pyrolysis based on the yields and the properties of the pyrolysis products. In the pyrolysis experiments, the samples of oil sands were heated to the final reaction temperature under varying heating rates and varying vacuum pressures. It was found that the effect of the reactor heating rate on the liquid oil yield of the pyrolysis reactions became less significant as the pressure was decreased below atmospheric level, to the point that the liquid yield of complete vacuum pyrolysis (0 MPa) was independent of the variation in heating rate. Longer vapor residence times lead to higher gas and coke yields and lower liquid yields. The coupling of retorting and vacuum pyrolysis was proposed and investigated, with the conclusion that vacuum can be utilized after the reactor reaches 500 °C with little sacrifice of the liquid product yield that can be produced by using vacuum only. Elemental analysis and the analysis of the distribution of saturates, aromatics, resins and asphaltenes (SARA) were carried out to characterize the differences in the composition of the pyrolysis liquid products. Simulated distillation was conducted to analyze the boiling point distribution of the initial bitumen and the pyrolysis oil products. Significant differences in the distribution of SARA fractions were observed between samples obtained from solvent extraction process and those from pyrolysis.