Formation and Characteristics of Carbonaceous Deposits from Heavy Hydrocarbon Coking Vapors

Deposition of carbonaceous material in the cyclone exit line is a chronic problem for fluid cokers and is a key process limitation to achieving longer run length. Extensive characterization studies were conducted for laboratory deposits from a bench-scale bitumen coker using modern analytical techniques, e.g., elemental analysis, X-ray fluorescence, thermogravimetric analysis, scanning electron microscopy, diffusive reflection infrared spectroscopy, and solid-state 13C nuclear magnetic resonance. Simulated distillation was also applied to solvent extracts of deposits. Results substantiate that on the laboratory scale physical condensation rather than chemical reaction was the primary reason for fluid coker cyclone exit line fouling. Entrained liquid droplets also contribute to the deposit formation. Although there are both polyaromatic and aliphatic structures in fresh laboratory deposits, the former dominate. Hightemperature operation led to deposits an increased polyaromatic content. Industrial deposits are more cokelike than laboratory deposits, and they differ in morphology.