ABSTRACT
With the increasing tendency for petroleum refiners to process heavier and more sour crudes in order to take advantage of the discount that heavy sour crudes have to light sweet crude, and with the stringent regulatory environmental mandates around the world to reduce sulfur levels in transportation and heating fuels, refiners will have to expand their ability to handle the increased levels of fuel desulfurization. The most common method for removing sulfur from fuels is hydrotreating and hydrocracking (grouped together herein as hydroprocessing). Hydroprocessing involves treating the sulfur-containing hydrocarbon with hydrogen at high pressure (500-2500 psig or 35-170 bar) and high temperature (620°F-760°F or 327°C-404°C) over a cobalt-molybdenum or nickel-molybdenum catalyst. The sulfur removed is produced as hydrogen sulfide (H2S).1 The reaction that occurs can be simply represented as
RSH H RH H S2 2+ = + (29.1)
In addition to hydroprocessing, the fluid catalytic cracker (FCC) unit will also yield some hydrogen sulfide. The amount produced from the FCC unit will depend on whether there is FCC feed hydroprocessing, a SOx transfer additive, FCC gasoline desulfurization, or a scrubber. All this H2S needs to be treated and removed from the refining operations. The Claus process is the most common method for H2S conversion and is explained in the following paragraphs.
