CONTROL OF COKE FORMATION FROM HYDROCRACKED ATHABASCA BITUMEN

The mechanism of formation of carbonaceous deposits from hydrocracked Athabaca bitumen is shown to result in both isotropic and anisotropic solids. The formation of mesophase spheres present as a separate liqui d phase has been observed in the laboratory. High severity results in the formation of an increased amount of anisotropic solid which is obs erved in both laboratory and commercial samples. The formation of thes e deposits in the downstream separators of a commercial plant has occu rred and is a hindrance to reliable operation. A strategy to reduce th e formation of these deposits in a commercial plant was evaluated in a series of laboratory experiments. The use of process-derived gas oils can be used as quench oil to lower the temperature of the commercial separators. There was no increase in the rate of toluene insoluble for mation as a result of the use of quench oils, which allowed the full a dvantage of the temperature decrease to be achieved. A qualitative com parison of the build-up of deposits in the commercial separators is pr ovided from separator vessel monitoring.