Gas Oil HDS
Hydrotreating is a catalytic process to stabilize products and remove objectionable elements, particularly sulfur and nitrogen, by reacting them with hydrogen prior to feed to the FCC Unit. Most hydrotreating reactions take place between 600-800˚F (315-425˚C) and at relatively high pressures up to 2000 psi (138 bar) depending on the level of reaction severity needed to meet product specification and the composition of the feedstock.
Hydrogen is combined with feed either before or after it has been heated to reaction temperature. The combined feed enters the top of a fixed bed reactor, or series of reactors depending on the level of contaminant removal required, where it flows downward over a bed of metal-oxide catalyst. For desulphurization, the most common catalysts are cobalt-molybdenum. When hydrodenitrofication (HDN) is desired in addition to desulfurization, nickel-molybdenum catalysts are recommended.
Hydrogen reacts with the oil to produce hydrogen sulfide from sulfur, ammonia from nitrogen, saturated hydrocarbons and free metals. Metals remain on the catalyst and other products leave with the oil-hydrogen steam. Hydrogen is separated from oil and hydrogen sulfide and light end are stripped from the desulfurized product.
Hydrogen sulfide is sent to sour gas processing and water removed from the process is sent to sour water stripping prior to use as desalter water or discharge.
