Analyzing the energy intensity and greenhouse gas emission of Canadian oil sands crude upgrading through process modeling and simulation
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This paper presents an evaluation of the energy intensity and related greenhouse gas/CO2 emissions of integrated oil sands crude upgrading processes. Two major oil sands crude upgrading schemes currently used in Canadian oil sands operations were investigated: cokingbased and hydroconversion-based. The analysis, which was based on a robust process model of the entire process, was constructed in Aspen HYSYS and calibrated with representative data. Simulations were conducted for the two upgrading schemes in order to generate a detailed inventory of the required energy and utility inputs: process fuel, steam, hydrogen and power. It was concluded that while hydroconversion-based scheme yields considerably higher amount of synthetic crude oil (SCO) than the cokerbased scheme (94 wt-% vs. 76 wt-%), it consumes more energy and is therefore more CO2-intensive (413.2 kg CO2/m3 SCO vs. 216.4 kg CO2/m3 SCO). This substantial difference results from the large amount of hydrogen consumed in the ebullated-bed hydroconverter in the hydroconversion-based scheme, as hydrogen production through conventional methane steam reforming is highly energy-intensive and therefore the major source of CO2 emission. Further simulations indicated that optimization of hydroconverter operating variables had only a minor effect on the overall CO2 emission due to the complex trade-off effect between energy inputs.
KeywordsOil sands crude upgrading hydroconversion process modeling greenhouse gas emissions
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