Comparison of Thermal Cracking Processes for Athabasca Oil Sand Bitumen: Relationship between Conversion and Yield

Abstract

This study compared various thermal cracking processes for Athabasca oil sand bitumen according to the relationship between vacuum residue (VR) conversion and the product yield for each process, using reported data. The conversion was defined as the fraction of VR which was converted to lighter products. The conventional processes examined were visbreaking, delayed coking, and fluid coking, and the developing processes were high conversion soaker cracking (HSC), heavy to light (HTL), I y Q, Eureka, and supercritical water cracking (SCWC). HSC and SCWC were higher severity visbreaking-type processes with conversions of 0.49 and 0.39-0.50, respectively. HTL and I y Q_(recycle) were lower severity fluid coking-type processes with a conversion of 0.52. I y Q (once through), and Eureka showed the highest conversions (0.62-0.68).Supercritical water (SCW) upgrading was operated experimentally at higher severity, with a conversion of 0.64, and showed the highest yield of distillate product (DP) among all thermal cracking processes investigated.Analysis of the conversion-yield relationship revealed the thermal cracking behavior of Athabasca bitumen. The key for achieving higher conversions with lower coke yield was considered to be efficient mass transfer of the volatile fraction stripped away from condensed phase which is liquid fraction at the experimental condition. The condensed-phase decomposition showed an upper limit of conversion of 0.55, and that with high mass-transfer system exceeded 0.65.

Effect of CO addition on upgrading bitumen in supercritical water

“…5), and thehigh-temperature conditions accelerated the polymerization of the coke precursor,increasingcoke formation.At 723 K in SCW + CO, there wasalmost no oil in the reactor and the ratio of heavy products with apparent boiling points of 723-773 K and of more than773 K in the extract oil was higher than under the other conditions.In this case, the distribution of oil from the oil-rich phase to the water-rich phase wasincreased considerablyby the high temperature.Almost all theoil containingcoke precursorswas probably distributed in thewater-rich phase and quickly passed through the reactor without much reaction.However, the coke yield reached its maximum at 713 K.The transfer of oil from the oil-rich phase to the water-rich phase was increased at 713 K, althoughvery heavy fractions, such as coke precursors,maynot have entered thewater-rich phase and remained in the oil-rich phase.Thesecoke precursorscould not dissolve in the small amount of oil in the oil-rich phaseand became coke.The lightest extract oil was obtained at 693 K.At 693 K, the amount of oil in the oil-rich phase was sufficientto dissolve the coke precursor effectively.The coke formation was suppressed by the high solubility of the coke precursors in oil, and coke formationproceededslowly because of thelow temperature.The decomposition of oil proceeded overa long retention time where the transfer of oil from the oil-rich phase to the water-rich phase was less than that above 17 693 K.Furthermore, the long retention time probably improved the hydrogenation of the coke precursor in the oil-rich phase through the WGSR.These factorsmay have contributed tothe effective upgrading of oil at 693 K.Finally, we compared the results in this study with previous resultsobtained in SCW.Morimoto et al compared various results for oil sand bitumen cracking[26].They focused the relationship between coke yield and conversion based on the boiling point of oil.We compared our results with other results in SCW according to their method.The conversion and coke yield aresummarized inTable 2.The conversion was defined by the amount of oil withhigher boiling points than the cut point.The trends can be discussed to some extent, although the definition of conversion was different under each set of conditions.…”

Modeling the Fluid Dynamics of a Commercial Ebullated Bed Hydroprocessor

“…Athabascan bitumen contains high quantities of asphaltenes, approximately 15 wt %, 35 and maintaining high hydrogen partial pressures is favorable for the conversion of the VR feedstock to lighter products as well as for reducing the rate of coke formation in the reactor. In fact, the VR resid used as feedstock for commercial ebullated bed hydroprocessors is a mix of both vacuum and atmospheric distillation tower bottoms resulting in aphaltene quantities significantly greater than that of the upstream bitumen feedstock.…”

Understanding bitumen partial upgrading through process modelling and simulation

“…To achieve this, partial upgrading technologies target primarily the vacuum residue (525 C+) portion of bitumen, a fraction that accounts for about 50-55 g/100 g of bitumen. Among the diversity of new concepts and existing technologies proposed for partial upgrading, [3][4][5][6][7][8] Reproduced with the permission of the Minister of Natural Resources Canada.…”

“…To achieve this, partial upgrading technologies target primarily the vacuum residue (525°C+) portion of bitumen, a fraction that accounts for about 50‐55 g/100 g of bitumen. Among the diversity of new concepts and existing technologies proposed for partial upgrading, [ 3–8 ] thermal cracking in its various forms, solvent deasphalting (SDA), and combinations thereof are the preferred candidates. The use of ebullated‐bed or slurry hydrocracking technologies to achieve the required density and viscosity reductions seems to be less desirable owing to the requirement for a large hydrogen production plant and sour gas treating infrastructure in the field.…”