PURPOSE: To prevent the blockage of a catalyst layer of a hydrodesulfurization apparatus caused by a petroleum-based heavy stock oil contg. fine magnetic particles by heating the oil to a specified temp. and passing it through a filter and a high-gradient magnetic separator to remove fine particles having specified particle sizes from it.
CONSTITUTION: A petroleum-based heavy stock oil contg. fine magnetic particles is heated to 180-320°C with a heat exchanger using a bottom oil at 300-350°C supplied by a fractionating column in the later stage of a hydrogenation apparatus, is then passed through a filter at a linear velocity of 1-10cm/sec to remove solid impurities having particle sizes of 2.5μm or higher, and is passed through a high-gradient magnetic separator filled with a ferromagnetic filler comprising shell-like metal fragments and having a magnetic gradient of 0.5-20kG/cm at a linear velocity of 0.5-10cm/sec to magnetize iron particles having particle sizes of 25μm or lower to adhere them to the surface of the filler and remove them from the oil, thus reducing the content of fine particles in the stock oil remarkably. Then, the iron particles attached to the filler are removed by switching the separator from iron removing to cleaning, causing the magnetic field around the filler to disappear, and passing the bottom oil through the separator at a linear velocity of 1-10cm/sec.
KAZETO MANABU
OUCHI MASAOKI
NAGANO HARUKI
USHIO MASARU
KAMIYA KOZO
NIPPON PETROLEUM REFINING CO
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