DEVELOPMENT OF METHOD FOR REMOVING IRON C ONTAMINANTS FROM FEEDSTOCK FOR RESIDUAL OIL DESULFURIZATION (RDS) (PART 1) INVESTIGATION OF SUBSTANCES CAUSING INCREASE OF REACTOR PRESSURE-DROP

For the purpose to investigate the cause of increase of the reactor pr essure drop (Delta P) in RDS reactor, the spent catalysts were analyze d in detail. As a result, it was found that FeS particles and surround ing carbonaceous materials were blocking up the space between the cata lyst particles. Investigating the source of FeS, it was clarified that there existed micron size iron contaminants in RDS feedstocks that ca talyze dehydrogenation reaction of aromatic compounds. These facts rev ealed the mechanism of increase in Delta P in RDS reactor. That is, ir on contaminants in feed oil for RDS accumulate quantitatively on the s urface of catalyst, around which carbonaceous materials are formed, th us reducing the space between the catalyst particles and causing incre ase of the reactor Delta P. Several properties of the iron contaminant s were studied for the purpose to develop a method for their removal. As a result, it was found that the iron contaminants consist of parama gnetic substance, Pyrotite, having a relatively large magnetic suscept ibility and that their particle diameters range from IO to 20 mu m. Si nce these properties are suitable for magnetic separation, preliminary experiments were carried out by using High Gradient Magnetic Separato r that resulted in removal of about 50%, of the iron contaminants. It was decided, therefore, to develop the magnetic separation.