|Bitumen, the product from oil sands, has different properties than light crude oil.|
Natural Resources Canada, National Research Council Canada, and the US Department of Energy have published a report that starts to identify the gaps in knowledge related to the use of fuels derived from synthetic crude produced from oil sands (OSDF—Oil-Sands-Derived Fuels) in advanced combustion engines.
The report, Oil Sands Chemistry and Engine Emissions Roadmap Workshop, captures the activity of a workshop the organizations hosted earlier this year.
The rapid development of Canadian oil sands (earlier post) combined with its strategic importance to North America is more widely introducing a new class of crude oils to US refineries. These crude oils, whether shipped as unprocessed bitumen or in upgraded form as synthetic crude have different characteristics from conventional light and heavy crudes, and their introduction as a major proportion of the refinery crude diet will present challenges.
Most conventional refineries are limited to using about 10-15% of synthetic oil sands crude in their diets before fuels quality limitations begin to appear, according to the report.
The challenges to utilizing these crudes include the need for more “severe” processes to refine the heavy synthetic crude to duplicate fuel characteristics to which engines have become accustomed. The technology to overcome these differences is largely known, but requires significant lead-time to install.
At the same time, the oil-sand producers are investing in upgrading facilities to add value to their product—thereby creating a challenge to ensure that the upgrading between the oil sands and the refining industry is not duplicated.
Engine R&D has been experimenting with new combustion technology for some time, primarily as a way to meet the more stringent emissions restrictions. At this relatively early stage of research there are a number of different new engines being studied, most revolving around lower temperature combustion, and whatever other engine parameters are necessary to ensure complete combustion.
Continued development of this new engine technology—with no clear winner anointed at this point—necessarily results in many technology gaps. In particular, this includes the marriage of the technology with the optimum fuel, and such other requirements as the impact on emission control systems.
Some of the overarching knowledge gaps, according to the report, include:
Chemical characterization of preferred fuel types.
Modeling of different fuel types in new internal combustion devices.
Fundamental understanding of diesel lubricity issue in all fuels.
Relationship between physical properties and fuel chemistry for all diesel fuels.
Mutual understanding of engine manufacturer and fuel producer issues.
The role of blending between high volumes of OSDF and conventional crudes. However, in this case, co-processing is a fact in many refineries today.
The role of additives and compatibility issues in all fuels.
The development of enabling devices, such as improved fuel quality sensors, and possibly on-board reforming devices, and their integration with optimum engine performance.
The workshop broke out to discuss in detail advanced engines with OSDF gasoline- and diesel-like fuels; fuels processing and characterization; emission control systems; fuels of the future; and the implications of OSDF on existing engines.
Each of the topical areas discussed in detail at the workshop have their own areas where more research is needed. For example:
Existing engines. The greatest challenge in the application of synthetic crude based fuels is presented by diesel fuels and jet fuels (as opposed to gasolines). The higher aromatics content in synthetic crude results in high-aromatics and low-cetane diesel, which produces higher emissions. Car makers who plan to introduce light-duty diesel engines in the North American market have been calling for increased cetane specification in US fuels (the minimum cetane number in Europe is 51, compared to 40 in the USA).
New engine/combustion technologies. Low temperature combustion (LTC) and partial homogeneous charge compression ignition (HCCI) are being commercialized as in-cylinder NOx reduction technologies. Contrary to the conventional diesel combustion, low-cetane number has been preferred in HCCI combustion, according to several studies. Chemical characterization and modeling of different fuel types in new internal combustion engines will be necessary to fill existing technology gaps.
Emission control systems. In existing engines, there is a lack of understanding of how OSDF impact the performance of emission control devices, such as soot filters, NOx and EGR system performance.
Future fuels. Other alternatives will be increasingly used—such as biofuels or Fischer-Tropsch fuels—as a fuels or blending components, both for existing diesel engines and future new engines.
The workshop was designed to identify the gaps it what is known; it did not attempt to assign responsibilities for any follow up work.