Conference Dates

July 1-6, 2007

First Page



Feed filters were installed in Syncrude hydrotreater units to protect the catalyst beds from plugging by fine solids in the feed. Severe filter fouling occurred after a process flow sheet change. The root cause of fouling was revealed through a step-by-step scientific investigation. It was first confirmed that the fouling problem was related to a process flow sheet change that introduced a heavy vacuum gas oil (HVGO) stream into the coker combined gas oil (KCGO) stream prior to filtration. Characterization of the foulant and the feed indicated that the fouling reactions are likely oxidative polymerization. Iron naphthenate or naphthenic acid in the HVGO stream could act as a catalyst for such a reaction. A bench-scale oxidation test was carried out to compare the oxygen uptake rates and the C7-insoluble contents after oxidation in KCGO, KCGO+HVGO, KCGO+iron naphthenate and KCGO+naphthenic acid streams. While the oxygen uptake kinetics for these samples were similar, the C7-insoluble contents for KCGO+HVGO and KCGO+iron naphthenate increased significantly after oxidation compared to the base case of KCGO. No significant increase of the C7-insoluble content was observed for KCGO+naphthenic acid, indicating that it was the iron naphthenate that catalyzed the fouling reactions. Iron naphthenate was a corrosion product in the HVGO stream, which could be eliminated by preventing corrosion in the vacuum distillation unit. The filter fouling problem indeed disappeared after the installation of corrosionresistant equipment. This paper is the modified version of a former publication: X.A. Wu, K.H. Chung, 2007, Hydrotreater feed filter fouling and its remedy, Energy Fuels Vol. 21, pp. 1212-1216.