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Focus on world heavy oil and bitumen resources to meet future energy demands has been increasing continuously, especially over the last decade. The Canadian province of Alberta has about 3,000 billion barrels of oilsands reserves and is expected to produce about 170 billion barrels of oil using the technologies available today. At present, about 40% of Canada’s oil production comes from oilsands. Upgrading of heavy oil/bitumen is far more costly than for conventional crude oil as it requires more complex technologies. Also, due to the nature of the bitumen it is not possible for all refineries to process the crude derived from oilsands. As a consequence, a detailed characterisation of heavy oil in order to obtain a better understanding of its nature and complex chemical composition has become very important. In addition, process severity causes increased production of hydrogen-deficient insoluble carbonaceous materials known as coke. The insoluble coke creates solid deposits, hot spots and heat transfer problems within refining units. Prediction of coke formation from different feedstocks is thus vital.

Many characterisation methods have been used to elucidate the structure, composition and properties of heavy oils and bitumens. Of these methods, determination of the correct amount of carbon residue has become increasingly important. Carbon residue is the residue that remains after evaporation and pyrolysis of crude oil/bitumen under given conditions. It is indicative of the coke-forming tendency of the oil under thermal degradation conditions, such as in refinery coking operations. Three methods have generally been used and accepted as standards for determining carbon residue: the Conradson method (ASTM D-189), the Ramsbottom method (ASTM D-524);and the microcarbon residue (MCR) method (ASTM D-4530). These three methods differ with regard to the experimental set-up; however, the principle remains the same. A known mass of a sample is heated under controlled conditions. The mass is recorded after heating. The remaining mass reflects the amount of residue present. The MCR method has attracted more attention because of the small amounts of sample used and simpler experimental set-up. Noel first described this method and showed the effect of various parameters (gas flow rate, type of gas used, type of crucible, etc.) on the amounts of MCR determined.

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